1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
2896
2897
2898
2899
2900
2901
2902
2903
2904
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914
2915
2916
2917
2918
2919
2920
2921
2922
2923
2924
2925
2926
2927
2928
2929
2930
2931
2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
2944
2945
2946
2947
2948
2949
2950
2951
2952
2953
2954
2955
2956
2957
2958
2959
2960
2961
2962
2963
2964
2965
2966
//! Compiler intrinsics.
//!
//! The corresponding definitions are in <https://github.com/rust-lang/rust/blob/master/compiler/rustc_codegen_llvm/src/intrinsic.rs>.
//! The corresponding const implementations are in <https://github.com/rust-lang/rust/blob/master/compiler/rustc_const_eval/src/interpret/intrinsics.rs>.
//!
//! # Const intrinsics
//!
//! Note: any changes to the constness of intrinsics should be discussed with the language team.
//! This includes changes in the stability of the constness.
//!
//! In order to make an intrinsic usable at compile-time, one needs to copy the implementation
//! from <https://github.com/rust-lang/miri/blob/master/src/shims/intrinsics> to
//! <https://github.com/rust-lang/rust/blob/master/compiler/rustc_const_eval/src/interpret/intrinsics.rs> and add a
//! `#[rustc_const_unstable(feature = "const_such_and_such", issue = "01234")]` to the intrinsic declaration.
//!
//! If an intrinsic is supposed to be used from a `const fn` with a `rustc_const_stable` attribute,
//! the intrinsic's attribute must be `rustc_const_stable`, too. Such a change should not be done
//! without T-lang consultation, because it bakes a feature into the language that cannot be
//! replicated in user code without compiler support.
//!
//! # Volatiles
//!
//! The volatile intrinsics provide operations intended to act on I/O
//! memory, which are guaranteed to not be reordered by the compiler
//! across other volatile intrinsics. See the LLVM documentation on
//! [[volatile]].
//!
//! [volatile]: https://llvm.org/docs/LangRef.html#volatile-memory-accesses
//!
//! # Atomics
//!
//! The atomic intrinsics provide common atomic operations on machine
//! words, with multiple possible memory orderings. They obey the same
//! semantics as C++11. See the LLVM documentation on [[atomics]].
//!
//! [atomics]: https://llvm.org/docs/Atomics.html
//!
//! A quick refresher on memory ordering:
//!
//! * Acquire - a barrier for acquiring a lock. Subsequent reads and writes
//!   take place after the barrier.
//! * Release - a barrier for releasing a lock. Preceding reads and writes
//!   take place before the barrier.
//! * Sequentially consistent - sequentially consistent operations are
//!   guaranteed to happen in order. This is the standard mode for working
//!   with atomic types and is equivalent to Java's `volatile`.

#![unstable(
    feature = "core_intrinsics",
    reason = "intrinsics are unlikely to ever be stabilized, instead \
                      they should be used through stabilized interfaces \
                      in the rest of the standard library",
    issue = "none"
)]
#![allow(missing_docs)]

use crate::marker::DiscriminantKind;
use crate::marker::Tuple;
use crate::mem;

pub mod mir;
pub mod simd;

// These imports are used for simplifying intra-doc links
#[allow(unused_imports)]
#[cfg(all(target_has_atomic = "8", target_has_atomic = "32", target_has_atomic = "ptr"))]
use crate::sync::atomic::{self, AtomicBool, AtomicI32, AtomicIsize, AtomicU32, Ordering};

#[stable(feature = "drop_in_place", since = "1.8.0")]
#[rustc_allowed_through_unstable_modules]
#[deprecated(note = "no longer an intrinsic - use `ptr::drop_in_place` directly", since = "1.52.0")]
#[inline]
pub unsafe fn drop_in_place<T: ?Sized>(to_drop: *mut T) {
    // SAFETY: see `ptr::drop_in_place`
    unsafe { crate::ptr::drop_in_place(to_drop) }
}

extern "rust-intrinsic" {
    // N.B., these intrinsics take raw pointers because they mutate aliased
    // memory, which is not valid for either `&` or `&mut`.

    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange` method by passing
    /// [`Ordering::Relaxed`] as both the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange`].
    #[rustc_nounwind]
    pub fn atomic_cxchg_relaxed_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange` method by passing
    /// [`Ordering::Relaxed`] and [`Ordering::Acquire`] as the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange`].
    #[rustc_nounwind]
    pub fn atomic_cxchg_relaxed_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange` method by passing
    /// [`Ordering::Relaxed`] and [`Ordering::SeqCst`] as the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange`].
    #[rustc_nounwind]
    pub fn atomic_cxchg_relaxed_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange` method by passing
    /// [`Ordering::Acquire`] and [`Ordering::Relaxed`] as the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange`].
    #[rustc_nounwind]
    pub fn atomic_cxchg_acquire_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange` method by passing
    /// [`Ordering::Acquire`] as both the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange`].
    #[rustc_nounwind]
    pub fn atomic_cxchg_acquire_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange` method by passing
    /// [`Ordering::Acquire`] and [`Ordering::SeqCst`] as the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange`].
    #[rustc_nounwind]
    pub fn atomic_cxchg_acquire_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange` method by passing
    /// [`Ordering::Release`] and [`Ordering::Relaxed`] as the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange`].
    #[rustc_nounwind]
    pub fn atomic_cxchg_release_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange` method by passing
    /// [`Ordering::Release`] and [`Ordering::Acquire`] as the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange`].
    #[rustc_nounwind]
    pub fn atomic_cxchg_release_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange` method by passing
    /// [`Ordering::Release`] and [`Ordering::SeqCst`] as the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange`].
    #[rustc_nounwind]
    pub fn atomic_cxchg_release_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange` method by passing
    /// [`Ordering::AcqRel`] and [`Ordering::Relaxed`] as the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange`].
    #[rustc_nounwind]
    pub fn atomic_cxchg_acqrel_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange` method by passing
    /// [`Ordering::AcqRel`] and [`Ordering::Acquire`] as the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange`].
    #[rustc_nounwind]
    pub fn atomic_cxchg_acqrel_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange` method by passing
    /// [`Ordering::AcqRel`] and [`Ordering::SeqCst`] as the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange`].
    #[rustc_nounwind]
    pub fn atomic_cxchg_acqrel_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange` method by passing
    /// [`Ordering::SeqCst`] and [`Ordering::Relaxed`] as the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange`].
    #[rustc_nounwind]
    pub fn atomic_cxchg_seqcst_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange` method by passing
    /// [`Ordering::SeqCst`] and [`Ordering::Acquire`] as the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange`].
    #[rustc_nounwind]
    pub fn atomic_cxchg_seqcst_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange` method by passing
    /// [`Ordering::SeqCst`] as both the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange`].
    #[rustc_nounwind]
    pub fn atomic_cxchg_seqcst_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);

    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange_weak` method by passing
    /// [`Ordering::Relaxed`] as both the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange_weak`].
    #[rustc_nounwind]
    pub fn atomic_cxchgweak_relaxed_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange_weak` method by passing
    /// [`Ordering::Relaxed`] and [`Ordering::Acquire`] as the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange_weak`].
    #[rustc_nounwind]
    pub fn atomic_cxchgweak_relaxed_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange_weak` method by passing
    /// [`Ordering::Relaxed`] and [`Ordering::SeqCst`] as the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange_weak`].
    #[rustc_nounwind]
    pub fn atomic_cxchgweak_relaxed_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange_weak` method by passing
    /// [`Ordering::Acquire`] and [`Ordering::Relaxed`] as the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange_weak`].
    #[rustc_nounwind]
    pub fn atomic_cxchgweak_acquire_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange_weak` method by passing
    /// [`Ordering::Acquire`] as both the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange_weak`].
    #[rustc_nounwind]
    pub fn atomic_cxchgweak_acquire_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange_weak` method by passing
    /// [`Ordering::Acquire`] and [`Ordering::SeqCst`] as the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange_weak`].
    #[rustc_nounwind]
    pub fn atomic_cxchgweak_acquire_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange_weak` method by passing
    /// [`Ordering::Release`] and [`Ordering::Relaxed`] as the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange_weak`].
    #[rustc_nounwind]
    pub fn atomic_cxchgweak_release_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange_weak` method by passing
    /// [`Ordering::Release`] and [`Ordering::Acquire`] as the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange_weak`].
    #[rustc_nounwind]
    pub fn atomic_cxchgweak_release_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange_weak` method by passing
    /// [`Ordering::Release`] and [`Ordering::SeqCst`] as the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange_weak`].
    #[rustc_nounwind]
    pub fn atomic_cxchgweak_release_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange_weak` method by passing
    /// [`Ordering::AcqRel`] and [`Ordering::Relaxed`] as the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange_weak`].
    #[rustc_nounwind]
    pub fn atomic_cxchgweak_acqrel_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange_weak` method by passing
    /// [`Ordering::AcqRel`] and [`Ordering::Acquire`] as the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange_weak`].
    #[rustc_nounwind]
    pub fn atomic_cxchgweak_acqrel_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange_weak` method by passing
    /// [`Ordering::AcqRel`] and [`Ordering::SeqCst`] as the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange_weak`].
    #[rustc_nounwind]
    pub fn atomic_cxchgweak_acqrel_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange_weak` method by passing
    /// [`Ordering::SeqCst`] and [`Ordering::Relaxed`] as the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange_weak`].
    #[rustc_nounwind]
    pub fn atomic_cxchgweak_seqcst_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange_weak` method by passing
    /// [`Ordering::SeqCst`] and [`Ordering::Acquire`] as the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange_weak`].
    #[rustc_nounwind]
    pub fn atomic_cxchgweak_seqcst_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
    /// Stores a value if the current value is the same as the `old` value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `compare_exchange_weak` method by passing
    /// [`Ordering::SeqCst`] as both the success and failure parameters.
    /// For example, [`AtomicBool::compare_exchange_weak`].
    #[rustc_nounwind]
    pub fn atomic_cxchgweak_seqcst_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);

    /// Loads the current value of the pointer.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `load` method by passing
    /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicBool::load`].
    #[rustc_nounwind]
    pub fn atomic_load_seqcst<T: Copy>(src: *const T) -> T;
    /// Loads the current value of the pointer.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `load` method by passing
    /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicBool::load`].
    #[rustc_nounwind]
    pub fn atomic_load_acquire<T: Copy>(src: *const T) -> T;
    /// Loads the current value of the pointer.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `load` method by passing
    /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicBool::load`].
    #[rustc_nounwind]
    pub fn atomic_load_relaxed<T: Copy>(src: *const T) -> T;
    /// Do NOT use this intrinsic; "unordered" operations do not exist in our memory model!
    /// In terms of the Rust Abstract Machine, this operation is equivalent to `src.read()`,
    /// i.e., it performs a non-atomic read.
    #[rustc_nounwind]
    pub fn atomic_load_unordered<T: Copy>(src: *const T) -> T;

    /// Stores the value at the specified memory location.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `store` method by passing
    /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicBool::store`].
    #[rustc_nounwind]
    pub fn atomic_store_seqcst<T: Copy>(dst: *mut T, val: T);
    /// Stores the value at the specified memory location.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `store` method by passing
    /// [`Ordering::Release`] as the `order`. For example, [`AtomicBool::store`].
    #[rustc_nounwind]
    pub fn atomic_store_release<T: Copy>(dst: *mut T, val: T);
    /// Stores the value at the specified memory location.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `store` method by passing
    /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicBool::store`].
    #[rustc_nounwind]
    pub fn atomic_store_relaxed<T: Copy>(dst: *mut T, val: T);
    /// Do NOT use this intrinsic; "unordered" operations do not exist in our memory model!
    /// In terms of the Rust Abstract Machine, this operation is equivalent to `dst.write(val)`,
    /// i.e., it performs a non-atomic write.
    #[rustc_nounwind]
    pub fn atomic_store_unordered<T: Copy>(dst: *mut T, val: T);

    /// Stores the value at the specified memory location, returning the old value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `swap` method by passing
    /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicBool::swap`].
    #[rustc_nounwind]
    pub fn atomic_xchg_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
    /// Stores the value at the specified memory location, returning the old value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `swap` method by passing
    /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicBool::swap`].
    #[rustc_nounwind]
    pub fn atomic_xchg_acquire<T: Copy>(dst: *mut T, src: T) -> T;
    /// Stores the value at the specified memory location, returning the old value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `swap` method by passing
    /// [`Ordering::Release`] as the `order`. For example, [`AtomicBool::swap`].
    #[rustc_nounwind]
    pub fn atomic_xchg_release<T: Copy>(dst: *mut T, src: T) -> T;
    /// Stores the value at the specified memory location, returning the old value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `swap` method by passing
    /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicBool::swap`].
    #[rustc_nounwind]
    pub fn atomic_xchg_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
    /// Stores the value at the specified memory location, returning the old value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `swap` method by passing
    /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicBool::swap`].
    #[rustc_nounwind]
    pub fn atomic_xchg_relaxed<T: Copy>(dst: *mut T, src: T) -> T;

    /// Adds to the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `fetch_add` method by passing
    /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicIsize::fetch_add`].
    #[rustc_nounwind]
    pub fn atomic_xadd_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
    /// Adds to the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `fetch_add` method by passing
    /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicIsize::fetch_add`].
    #[rustc_nounwind]
    pub fn atomic_xadd_acquire<T: Copy>(dst: *mut T, src: T) -> T;
    /// Adds to the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `fetch_add` method by passing
    /// [`Ordering::Release`] as the `order`. For example, [`AtomicIsize::fetch_add`].
    #[rustc_nounwind]
    pub fn atomic_xadd_release<T: Copy>(dst: *mut T, src: T) -> T;
    /// Adds to the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `fetch_add` method by passing
    /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicIsize::fetch_add`].
    #[rustc_nounwind]
    pub fn atomic_xadd_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
    /// Adds to the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `fetch_add` method by passing
    /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicIsize::fetch_add`].
    #[rustc_nounwind]
    pub fn atomic_xadd_relaxed<T: Copy>(dst: *mut T, src: T) -> T;

    /// Subtract from the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `fetch_sub` method by passing
    /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicIsize::fetch_sub`].
    #[rustc_nounwind]
    pub fn atomic_xsub_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
    /// Subtract from the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `fetch_sub` method by passing
    /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicIsize::fetch_sub`].
    #[rustc_nounwind]
    pub fn atomic_xsub_acquire<T: Copy>(dst: *mut T, src: T) -> T;
    /// Subtract from the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `fetch_sub` method by passing
    /// [`Ordering::Release`] as the `order`. For example, [`AtomicIsize::fetch_sub`].
    #[rustc_nounwind]
    pub fn atomic_xsub_release<T: Copy>(dst: *mut T, src: T) -> T;
    /// Subtract from the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `fetch_sub` method by passing
    /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicIsize::fetch_sub`].
    #[rustc_nounwind]
    pub fn atomic_xsub_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
    /// Subtract from the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `fetch_sub` method by passing
    /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicIsize::fetch_sub`].
    #[rustc_nounwind]
    pub fn atomic_xsub_relaxed<T: Copy>(dst: *mut T, src: T) -> T;

    /// Bitwise and with the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `fetch_and` method by passing
    /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicBool::fetch_and`].
    #[rustc_nounwind]
    pub fn atomic_and_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
    /// Bitwise and with the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `fetch_and` method by passing
    /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicBool::fetch_and`].
    #[rustc_nounwind]
    pub fn atomic_and_acquire<T: Copy>(dst: *mut T, src: T) -> T;
    /// Bitwise and with the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `fetch_and` method by passing
    /// [`Ordering::Release`] as the `order`. For example, [`AtomicBool::fetch_and`].
    #[rustc_nounwind]
    pub fn atomic_and_release<T: Copy>(dst: *mut T, src: T) -> T;
    /// Bitwise and with the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `fetch_and` method by passing
    /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicBool::fetch_and`].
    #[rustc_nounwind]
    pub fn atomic_and_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
    /// Bitwise and with the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `fetch_and` method by passing
    /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicBool::fetch_and`].
    #[rustc_nounwind]
    pub fn atomic_and_relaxed<T: Copy>(dst: *mut T, src: T) -> T;

    /// Bitwise nand with the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`AtomicBool`] type via the `fetch_nand` method by passing
    /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicBool::fetch_nand`].
    #[rustc_nounwind]
    pub fn atomic_nand_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
    /// Bitwise nand with the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`AtomicBool`] type via the `fetch_nand` method by passing
    /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicBool::fetch_nand`].
    #[rustc_nounwind]
    pub fn atomic_nand_acquire<T: Copy>(dst: *mut T, src: T) -> T;
    /// Bitwise nand with the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`AtomicBool`] type via the `fetch_nand` method by passing
    /// [`Ordering::Release`] as the `order`. For example, [`AtomicBool::fetch_nand`].
    #[rustc_nounwind]
    pub fn atomic_nand_release<T: Copy>(dst: *mut T, src: T) -> T;
    /// Bitwise nand with the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`AtomicBool`] type via the `fetch_nand` method by passing
    /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicBool::fetch_nand`].
    #[rustc_nounwind]
    pub fn atomic_nand_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
    /// Bitwise nand with the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`AtomicBool`] type via the `fetch_nand` method by passing
    /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicBool::fetch_nand`].
    #[rustc_nounwind]
    pub fn atomic_nand_relaxed<T: Copy>(dst: *mut T, src: T) -> T;

    /// Bitwise or with the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `fetch_or` method by passing
    /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicBool::fetch_or`].
    #[rustc_nounwind]
    pub fn atomic_or_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
    /// Bitwise or with the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `fetch_or` method by passing
    /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicBool::fetch_or`].
    #[rustc_nounwind]
    pub fn atomic_or_acquire<T: Copy>(dst: *mut T, src: T) -> T;
    /// Bitwise or with the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `fetch_or` method by passing
    /// [`Ordering::Release`] as the `order`. For example, [`AtomicBool::fetch_or`].
    #[rustc_nounwind]
    pub fn atomic_or_release<T: Copy>(dst: *mut T, src: T) -> T;
    /// Bitwise or with the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `fetch_or` method by passing
    /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicBool::fetch_or`].
    #[rustc_nounwind]
    pub fn atomic_or_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
    /// Bitwise or with the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `fetch_or` method by passing
    /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicBool::fetch_or`].
    #[rustc_nounwind]
    pub fn atomic_or_relaxed<T: Copy>(dst: *mut T, src: T) -> T;

    /// Bitwise xor with the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `fetch_xor` method by passing
    /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicBool::fetch_xor`].
    #[rustc_nounwind]
    pub fn atomic_xor_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
    /// Bitwise xor with the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `fetch_xor` method by passing
    /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicBool::fetch_xor`].
    #[rustc_nounwind]
    pub fn atomic_xor_acquire<T: Copy>(dst: *mut T, src: T) -> T;
    /// Bitwise xor with the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `fetch_xor` method by passing
    /// [`Ordering::Release`] as the `order`. For example, [`AtomicBool::fetch_xor`].
    #[rustc_nounwind]
    pub fn atomic_xor_release<T: Copy>(dst: *mut T, src: T) -> T;
    /// Bitwise xor with the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `fetch_xor` method by passing
    /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicBool::fetch_xor`].
    #[rustc_nounwind]
    pub fn atomic_xor_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
    /// Bitwise xor with the current value, returning the previous value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] types via the `fetch_xor` method by passing
    /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicBool::fetch_xor`].
    #[rustc_nounwind]
    pub fn atomic_xor_relaxed<T: Copy>(dst: *mut T, src: T) -> T;

    /// Maximum with the current value using a signed comparison.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] signed integer types via the `fetch_max` method by passing
    /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicI32::fetch_max`].
    #[rustc_nounwind]
    pub fn atomic_max_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
    /// Maximum with the current value using a signed comparison.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] signed integer types via the `fetch_max` method by passing
    /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicI32::fetch_max`].
    #[rustc_nounwind]
    pub fn atomic_max_acquire<T: Copy>(dst: *mut T, src: T) -> T;
    /// Maximum with the current value using a signed comparison.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] signed integer types via the `fetch_max` method by passing
    /// [`Ordering::Release`] as the `order`. For example, [`AtomicI32::fetch_max`].
    #[rustc_nounwind]
    pub fn atomic_max_release<T: Copy>(dst: *mut T, src: T) -> T;
    /// Maximum with the current value using a signed comparison.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] signed integer types via the `fetch_max` method by passing
    /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicI32::fetch_max`].
    #[rustc_nounwind]
    pub fn atomic_max_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
    /// Maximum with the current value.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] signed integer types via the `fetch_max` method by passing
    /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicI32::fetch_max`].
    #[rustc_nounwind]
    pub fn atomic_max_relaxed<T: Copy>(dst: *mut T, src: T) -> T;

    /// Minimum with the current value using a signed comparison.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] signed integer types via the `fetch_min` method by passing
    /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicI32::fetch_min`].
    #[rustc_nounwind]
    pub fn atomic_min_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
    /// Minimum with the current value using a signed comparison.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] signed integer types via the `fetch_min` method by passing
    /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicI32::fetch_min`].
    #[rustc_nounwind]
    pub fn atomic_min_acquire<T: Copy>(dst: *mut T, src: T) -> T;
    /// Minimum with the current value using a signed comparison.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] signed integer types via the `fetch_min` method by passing
    /// [`Ordering::Release`] as the `order`. For example, [`AtomicI32::fetch_min`].
    #[rustc_nounwind]
    pub fn atomic_min_release<T: Copy>(dst: *mut T, src: T) -> T;
    /// Minimum with the current value using a signed comparison.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] signed integer types via the `fetch_min` method by passing
    /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicI32::fetch_min`].
    pub fn atomic_min_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
    /// Minimum with the current value using a signed comparison.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] signed integer types via the `fetch_min` method by passing
    /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicI32::fetch_min`].
    #[rustc_nounwind]
    pub fn atomic_min_relaxed<T: Copy>(dst: *mut T, src: T) -> T;

    /// Minimum with the current value using an unsigned comparison.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] unsigned integer types via the `fetch_min` method by passing
    /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicU32::fetch_min`].
    #[rustc_nounwind]
    pub fn atomic_umin_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
    /// Minimum with the current value using an unsigned comparison.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] unsigned integer types via the `fetch_min` method by passing
    /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicU32::fetch_min`].
    #[rustc_nounwind]
    pub fn atomic_umin_acquire<T: Copy>(dst: *mut T, src: T) -> T;
    /// Minimum with the current value using an unsigned comparison.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] unsigned integer types via the `fetch_min` method by passing
    /// [`Ordering::Release`] as the `order`. For example, [`AtomicU32::fetch_min`].
    #[rustc_nounwind]
    pub fn atomic_umin_release<T: Copy>(dst: *mut T, src: T) -> T;
    /// Minimum with the current value using an unsigned comparison.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] unsigned integer types via the `fetch_min` method by passing
    /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicU32::fetch_min`].
    #[rustc_nounwind]
    pub fn atomic_umin_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
    /// Minimum with the current value using an unsigned comparison.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] unsigned integer types via the `fetch_min` method by passing
    /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicU32::fetch_min`].
    #[rustc_nounwind]
    pub fn atomic_umin_relaxed<T: Copy>(dst: *mut T, src: T) -> T;

    /// Maximum with the current value using an unsigned comparison.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] unsigned integer types via the `fetch_max` method by passing
    /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicU32::fetch_max`].
    #[rustc_nounwind]
    pub fn atomic_umax_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
    /// Maximum with the current value using an unsigned comparison.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] unsigned integer types via the `fetch_max` method by passing
    /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicU32::fetch_max`].
    #[rustc_nounwind]
    pub fn atomic_umax_acquire<T: Copy>(dst: *mut T, src: T) -> T;
    /// Maximum with the current value using an unsigned comparison.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] unsigned integer types via the `fetch_max` method by passing
    /// [`Ordering::Release`] as the `order`. For example, [`AtomicU32::fetch_max`].
    #[rustc_nounwind]
    pub fn atomic_umax_release<T: Copy>(dst: *mut T, src: T) -> T;
    /// Maximum with the current value using an unsigned comparison.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] unsigned integer types via the `fetch_max` method by passing
    /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicU32::fetch_max`].
    #[rustc_nounwind]
    pub fn atomic_umax_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
    /// Maximum with the current value using an unsigned comparison.
    ///
    /// The stabilized version of this intrinsic is available on the
    /// [`atomic`] unsigned integer types via the `fetch_max` method by passing
    /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicU32::fetch_max`].
    #[rustc_nounwind]
    pub fn atomic_umax_relaxed<T: Copy>(dst: *mut T, src: T) -> T;

    /// An atomic fence.
    ///
    /// The stabilized version of this intrinsic is available in
    /// [`atomic::fence`] by passing [`Ordering::SeqCst`]
    /// as the `order`.
    #[rustc_nounwind]
    pub fn atomic_fence_seqcst();
    /// An atomic fence.
    ///
    /// The stabilized version of this intrinsic is available in
    /// [`atomic::fence`] by passing [`Ordering::Acquire`]
    /// as the `order`.
    #[rustc_nounwind]
    pub fn atomic_fence_acquire();
    /// An atomic fence.
    ///
    /// The stabilized version of this intrinsic is available in
    /// [`atomic::fence`] by passing [`Ordering::Release`]
    /// as the `order`.
    #[rustc_nounwind]
    pub fn atomic_fence_release();
    /// An atomic fence.
    ///
    /// The stabilized version of this intrinsic is available in
    /// [`atomic::fence`] by passing [`Ordering::AcqRel`]
    /// as the `order`.
    #[rustc_nounwind]
    pub fn atomic_fence_acqrel();

    /// A compiler-only memory barrier.
    ///
    /// Memory accesses will never be reordered across this barrier by the
    /// compiler, but no instructions will be emitted for it. This is
    /// appropriate for operations on the same thread that may be preempted,
    /// such as when interacting with signal handlers.
    ///
    /// The stabilized version of this intrinsic is available in
    /// [`atomic::compiler_fence`] by passing [`Ordering::SeqCst`]
    /// as the `order`.
    #[rustc_nounwind]
    pub fn atomic_singlethreadfence_seqcst();
    /// A compiler-only memory barrier.
    ///
    /// Memory accesses will never be reordered across this barrier by the
    /// compiler, but no instructions will be emitted for it. This is
    /// appropriate for operations on the same thread that may be preempted,
    /// such as when interacting with signal handlers.
    ///
    /// The stabilized version of this intrinsic is available in
    /// [`atomic::compiler_fence`] by passing [`Ordering::Acquire`]
    /// as the `order`.
    #[rustc_nounwind]
    pub fn atomic_singlethreadfence_acquire();
    /// A compiler-only memory barrier.
    ///
    /// Memory accesses will never be reordered across this barrier by the
    /// compiler, but no instructions will be emitted for it. This is
    /// appropriate for operations on the same thread that may be preempted,
    /// such as when interacting with signal handlers.
    ///
    /// The stabilized version of this intrinsic is available in
    /// [`atomic::compiler_fence`] by passing [`Ordering::Release`]
    /// as the `order`.
    #[rustc_nounwind]
    pub fn atomic_singlethreadfence_release();
    /// A compiler-only memory barrier.
    ///
    /// Memory accesses will never be reordered across this barrier by the
    /// compiler, but no instructions will be emitted for it. This is
    /// appropriate for operations on the same thread that may be preempted,
    /// such as when interacting with signal handlers.
    ///
    /// The stabilized version of this intrinsic is available in
    /// [`atomic::compiler_fence`] by passing [`Ordering::AcqRel`]
    /// as the `order`.
    #[rustc_nounwind]
    pub fn atomic_singlethreadfence_acqrel();

    /// The `prefetch` intrinsic is a hint to the code generator to insert a prefetch instruction
    /// if supported; otherwise, it is a no-op.
    /// Prefetches have no effect on the behavior of the program but can change its performance
    /// characteristics.
    ///
    /// The `locality` argument must be a constant integer and is a temporal locality specifier
    /// ranging from (0) - no locality, to (3) - extremely local keep in cache.
    ///
    /// This intrinsic does not have a stable counterpart.
    #[rustc_nounwind]
    pub fn prefetch_read_data<T>(data: *const T, locality: i32);
    /// The `prefetch` intrinsic is a hint to the code generator to insert a prefetch instruction
    /// if supported; otherwise, it is a no-op.
    /// Prefetches have no effect on the behavior of the program but can change its performance
    /// characteristics.
    ///
    /// The `locality` argument must be a constant integer and is a temporal locality specifier
    /// ranging from (0) - no locality, to (3) - extremely local keep in cache.
    ///
    /// This intrinsic does not have a stable counterpart.
    #[rustc_nounwind]
    pub fn prefetch_write_data<T>(data: *const T, locality: i32);
    /// The `prefetch` intrinsic is a hint to the code generator to insert a prefetch instruction
    /// if supported; otherwise, it is a no-op.
    /// Prefetches have no effect on the behavior of the program but can change its performance
    /// characteristics.
    ///
    /// The `locality` argument must be a constant integer and is a temporal locality specifier
    /// ranging from (0) - no locality, to (3) - extremely local keep in cache.
    ///
    /// This intrinsic does not have a stable counterpart.
    #[rustc_nounwind]
    pub fn prefetch_read_instruction<T>(data: *const T, locality: i32);
    /// The `prefetch` intrinsic is a hint to the code generator to insert a prefetch instruction
    /// if supported; otherwise, it is a no-op.
    /// Prefetches have no effect on the behavior of the program but can change its performance
    /// characteristics.
    ///
    /// The `locality` argument must be a constant integer and is a temporal locality specifier
    /// ranging from (0) - no locality, to (3) - extremely local keep in cache.
    ///
    /// This intrinsic does not have a stable counterpart.
    #[rustc_nounwind]
    pub fn prefetch_write_instruction<T>(data: *const T, locality: i32);

    /// Magic intrinsic that derives its meaning from attributes
    /// attached to the function.
    ///
    /// For example, dataflow uses this to inject static assertions so
    /// that `rustc_peek(potentially_uninitialized)` would actually
    /// double-check that dataflow did indeed compute that it is
    /// uninitialized at that point in the control flow.
    ///
    /// This intrinsic should not be used outside of the compiler.
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn rustc_peek<T>(_: T) -> T;

    /// Aborts the execution of the process.
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// [`std::process::abort`](../../std/process/fn.abort.html) is to be preferred if possible,
    /// as its behavior is more user-friendly and more stable.
    ///
    /// The current implementation of `intrinsics::abort` is to invoke an invalid instruction,
    /// on most platforms.
    /// On Unix, the
    /// process will probably terminate with a signal like `SIGABRT`, `SIGILL`, `SIGTRAP`, `SIGSEGV` or
    /// `SIGBUS`.  The precise behaviour is not guaranteed and not stable.
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn abort() -> !;

    /// Informs the optimizer that this point in the code is not reachable,
    /// enabling further optimizations.
    ///
    /// N.B., this is very different from the `unreachable!()` macro: Unlike the
    /// macro, which panics when it is executed, it is *undefined behavior* to
    /// reach code marked with this function.
    ///
    /// The stabilized version of this intrinsic is [`core::hint::unreachable_unchecked`].
    #[rustc_const_stable(feature = "const_unreachable_unchecked", since = "1.57.0")]
    #[rustc_nounwind]
    pub fn unreachable() -> !;

    /// Informs the optimizer that a condition is always true.
    /// If the condition is false, the behavior is undefined.
    ///
    /// No code is generated for this intrinsic, but the optimizer will try
    /// to preserve it (and its condition) between passes, which may interfere
    /// with optimization of surrounding code and reduce performance. It should
    /// not be used if the invariant can be discovered by the optimizer on its
    /// own, or if it does not enable any significant optimizations.
    ///
    /// This intrinsic does not have a stable counterpart.
    #[rustc_const_stable(feature = "const_assume", since = "1.77.0")]
    #[rustc_nounwind]
    pub fn assume(b: bool);

    /// Hints to the compiler that branch condition is likely to be true.
    /// Returns the value passed to it.
    ///
    /// Any use other than with `if` statements will probably not have an effect.
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// This intrinsic does not have a stable counterpart.
    #[rustc_const_unstable(feature = "const_likely", issue = "none")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn likely(b: bool) -> bool;

    /// Hints to the compiler that branch condition is likely to be false.
    /// Returns the value passed to it.
    ///
    /// Any use other than with `if` statements will probably not have an effect.
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// This intrinsic does not have a stable counterpart.
    #[rustc_const_unstable(feature = "const_likely", issue = "none")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn unlikely(b: bool) -> bool;

    /// Executes a breakpoint trap, for inspection by a debugger.
    ///
    /// This intrinsic does not have a stable counterpart.
    #[rustc_nounwind]
    pub fn breakpoint();

    /// The size of a type in bytes.
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// More specifically, this is the offset in bytes between successive
    /// items of the same type, including alignment padding.
    ///
    /// The stabilized version of this intrinsic is [`core::mem::size_of`].
    #[rustc_const_stable(feature = "const_size_of", since = "1.40.0")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn size_of<T>() -> usize;

    /// The minimum alignment of a type.
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// The stabilized version of this intrinsic is [`core::mem::align_of`].
    #[rustc_const_stable(feature = "const_min_align_of", since = "1.40.0")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn min_align_of<T>() -> usize;
    /// The preferred alignment of a type.
    ///
    /// This intrinsic does not have a stable counterpart.
    /// It's "tracking issue" is [#91971](https://github.com/rust-lang/rust/issues/91971).
    #[rustc_const_unstable(feature = "const_pref_align_of", issue = "91971")]
    #[rustc_nounwind]
    pub fn pref_align_of<T>() -> usize;

    /// The size of the referenced value in bytes.
    ///
    /// The stabilized version of this intrinsic is [`mem::size_of_val`].
    #[rustc_const_unstable(feature = "const_size_of_val", issue = "46571")]
    #[rustc_nounwind]
    pub fn size_of_val<T: ?Sized>(_: *const T) -> usize;
    /// The required alignment of the referenced value.
    ///
    /// The stabilized version of this intrinsic is [`core::mem::align_of_val`].
    #[rustc_const_unstable(feature = "const_align_of_val", issue = "46571")]
    #[rustc_nounwind]
    pub fn min_align_of_val<T: ?Sized>(_: *const T) -> usize;

    /// Gets a static string slice containing the name of a type.
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// The stabilized version of this intrinsic is [`core::any::type_name`].
    #[rustc_const_unstable(feature = "const_type_name", issue = "63084")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn type_name<T: ?Sized>() -> &'static str;

    /// Gets an identifier which is globally unique to the specified type. This
    /// function will return the same value for a type regardless of whichever
    /// crate it is invoked in.
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// The stabilized version of this intrinsic is [`core::any::TypeId::of`].
    #[rustc_const_unstable(feature = "const_type_id", issue = "77125")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn type_id<T: ?Sized + 'static>() -> u128;

    /// A guard for unsafe functions that cannot ever be executed if `T` is uninhabited:
    /// This will statically either panic, or do nothing.
    ///
    /// This intrinsic does not have a stable counterpart.
    #[rustc_const_stable(feature = "const_assert_type", since = "1.59.0")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn assert_inhabited<T>();

    /// A guard for unsafe functions that cannot ever be executed if `T` does not permit
    /// zero-initialization: This will statically either panic, or do nothing.
    ///
    /// This intrinsic does not have a stable counterpart.
    #[rustc_const_stable(feature = "const_assert_type2", since = "1.75.0")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn assert_zero_valid<T>();

    /// A guard for `std::mem::uninitialized`. This will statically either panic, or do nothing.
    ///
    /// This intrinsic does not have a stable counterpart.
    #[rustc_const_stable(feature = "const_assert_type2", since = "1.75.0")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn assert_mem_uninitialized_valid<T>();

    /// Gets a reference to a static `Location` indicating where it was called.
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// Consider using [`core::panic::Location::caller`] instead.
    #[rustc_const_unstable(feature = "const_caller_location", issue = "76156")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn caller_location() -> &'static crate::panic::Location<'static>;

    /// Moves a value out of scope without running drop glue.
    ///
    /// This exists solely for [`mem::forget_unsized`]; normal `forget` uses
    /// `ManuallyDrop` instead.
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    #[rustc_const_unstable(feature = "const_intrinsic_forget", issue = "none")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn forget<T: ?Sized>(_: T);

    /// Reinterprets the bits of a value of one type as another type.
    ///
    /// Both types must have the same size. Compilation will fail if this is not guaranteed.
    ///
    /// `transmute` is semantically equivalent to a bitwise move of one type
    /// into another. It copies the bits from the source value into the
    /// destination value, then forgets the original. Note that source and destination
    /// are passed by-value, which means if `Src` or `Dst` contain padding, that padding
    /// is *not* guaranteed to be preserved by `transmute`.
    ///
    /// Both the argument and the result must be [valid](../../nomicon/what-unsafe-does.html) at
    /// their given type. Violating this condition leads to [undefined behavior][ub]. The compiler
    /// will generate code *assuming that you, the programmer, ensure that there will never be
    /// undefined behavior*. It is therefore your responsibility to guarantee that every value
    /// passed to `transmute` is valid at both types `Src` and `Dst`. Failing to uphold this condition
    /// may lead to unexpected and unstable compilation results. This makes `transmute` **incredibly
    /// unsafe**. `transmute` should be the absolute last resort.
    ///
    /// Transmuting pointers *to* integers in a `const` context is [undefined behavior][ub],
    /// unless the pointer was originally created *from* an integer.
    /// (That includes this function specifically, integer-to-pointer casts, and helpers like [`invalid`][crate::ptr::invalid],
    /// but also semantically-equivalent conversions such as punning through `repr(C)` union fields.)
    /// Any attempt to use the resulting value for integer operations will abort const-evaluation.
    /// (And even outside `const`, such transmutation is touching on many unspecified aspects of the
    /// Rust memory model and should be avoided. See below for alternatives.)
    ///
    /// Because `transmute` is a by-value operation, alignment of the *transmuted values
    /// themselves* is not a concern. As with any other function, the compiler already ensures
    /// both `Src` and `Dst` are properly aligned. However, when transmuting values that *point
    /// elsewhere* (such as pointers, references, boxes…), the caller has to ensure proper
    /// alignment of the pointed-to values.
    ///
    /// The [nomicon](../../nomicon/transmutes.html) has additional documentation.
    ///
    /// [ub]: ../../reference/behavior-considered-undefined.html
    ///
    /// # Examples
    ///
    /// There are a few things that `transmute` is really useful for.
    ///
    /// Turning a pointer into a function pointer. This is *not* portable to
    /// machines where function pointers and data pointers have different sizes.
    ///
    /// ```
    /// fn foo() -> i32 {
    ///     0
    /// }
    /// // Crucially, we `as`-cast to a raw pointer before `transmute`ing to a function pointer.
    /// // This avoids an integer-to-pointer `transmute`, which can be problematic.
    /// // Transmuting between raw pointers and function pointers (i.e., two pointer types) is fine.
    /// let pointer = foo as *const ();
    /// let function = unsafe {
    ///     std::mem::transmute::<*const (), fn() -> i32>(pointer)
    /// };
    /// assert_eq!(function(), 0);
    /// ```
    ///
    /// Extending a lifetime, or shortening an invariant lifetime. This is
    /// advanced, very unsafe Rust!
    ///
    /// ```
    /// struct R<'a>(&'a i32);
    /// unsafe fn extend_lifetime<'b>(r: R<'b>) -> R<'static> {
    ///     std::mem::transmute::<R<'b>, R<'static>>(r)
    /// }
    ///
    /// unsafe fn shorten_invariant_lifetime<'b, 'c>(r: &'b mut R<'static>)
    ///                                              -> &'b mut R<'c> {
    ///     std::mem::transmute::<&'b mut R<'static>, &'b mut R<'c>>(r)
    /// }
    /// ```
    ///
    /// # Alternatives
    ///
    /// Don't despair: many uses of `transmute` can be achieved through other means.
    /// Below are common applications of `transmute` which can be replaced with safer
    /// constructs.
    ///
    /// Turning raw bytes (`[u8; SZ]`) into `u32`, `f64`, etc.:
    ///
    /// ```
    /// let raw_bytes = [0x78, 0x56, 0x34, 0x12];
    ///
    /// let num = unsafe {
    ///     std::mem::transmute::<[u8; 4], u32>(raw_bytes)
    /// };
    ///
    /// // use `u32::from_ne_bytes` instead
    /// let num = u32::from_ne_bytes(raw_bytes);
    /// // or use `u32::from_le_bytes` or `u32::from_be_bytes` to specify the endianness
    /// let num = u32::from_le_bytes(raw_bytes);
    /// assert_eq!(num, 0x12345678);
    /// let num = u32::from_be_bytes(raw_bytes);
    /// assert_eq!(num, 0x78563412);
    /// ```
    ///
    /// Turning a pointer into a `usize`:
    ///
    /// ```no_run
    /// let ptr = &0;
    /// let ptr_num_transmute = unsafe {
    ///     std::mem::transmute::<&i32, usize>(ptr)
    /// };
    ///
    /// // Use an `as` cast instead
    /// let ptr_num_cast = ptr as *const i32 as usize;
    /// ```
    ///
    /// Note that using `transmute` to turn a pointer to a `usize` is (as noted above) [undefined
    /// behavior][ub] in `const` contexts. Also outside of consts, this operation might not behave
    /// as expected -- this is touching on many unspecified aspects of the Rust memory model.
    /// Depending on what the code is doing, the following alternatives are preferable to
    /// pointer-to-integer transmutation:
    /// - If the code just wants to store data of arbitrary type in some buffer and needs to pick a
    ///   type for that buffer, it can use [`MaybeUninit`][mem::MaybeUninit].
    /// - If the code actually wants to work on the address the pointer points to, it can use `as`
    ///   casts or [`ptr.addr()`][pointer::addr].
    ///
    /// Turning a `*mut T` into an `&mut T`:
    ///
    /// ```
    /// let ptr: *mut i32 = &mut 0;
    /// let ref_transmuted = unsafe {
    ///     std::mem::transmute::<*mut i32, &mut i32>(ptr)
    /// };
    ///
    /// // Use a reborrow instead
    /// let ref_casted = unsafe { &mut *ptr };
    /// ```
    ///
    /// Turning an `&mut T` into an `&mut U`:
    ///
    /// ```
    /// let ptr = &mut 0;
    /// let val_transmuted = unsafe {
    ///     std::mem::transmute::<&mut i32, &mut u32>(ptr)
    /// };
    ///
    /// // Now, put together `as` and reborrowing - note the chaining of `as`
    /// // `as` is not transitive
    /// let val_casts = unsafe { &mut *(ptr as *mut i32 as *mut u32) };
    /// ```
    ///
    /// Turning an `&str` into a `&[u8]`:
    ///
    /// ```
    /// // this is not a good way to do this.
    /// let slice = unsafe { std::mem::transmute::<&str, &[u8]>("Rust") };
    /// assert_eq!(slice, &[82, 117, 115, 116]);
    ///
    /// // You could use `str::as_bytes`
    /// let slice = "Rust".as_bytes();
    /// assert_eq!(slice, &[82, 117, 115, 116]);
    ///
    /// // Or, just use a byte string, if you have control over the string
    /// // literal
    /// assert_eq!(b"Rust", &[82, 117, 115, 116]);
    /// ```
    ///
    /// Turning a `Vec<&T>` into a `Vec<Option<&T>>`.
    ///
    /// To transmute the inner type of the contents of a container, you must make sure to not
    /// violate any of the container's invariants. For `Vec`, this means that both the size
    /// *and alignment* of the inner types have to match. Other containers might rely on the
    /// size of the type, alignment, or even the `TypeId`, in which case transmuting wouldn't
    /// be possible at all without violating the container invariants.
    ///
    /// ```
    /// let store = [0, 1, 2, 3];
    /// let v_orig = store.iter().collect::<Vec<&i32>>();
    ///
    /// // clone the vector as we will reuse them later
    /// let v_clone = v_orig.clone();
    ///
    /// // Using transmute: this relies on the unspecified data layout of `Vec`, which is a
    /// // bad idea and could cause Undefined Behavior.
    /// // However, it is no-copy.
    /// let v_transmuted = unsafe {
    ///     std::mem::transmute::<Vec<&i32>, Vec<Option<&i32>>>(v_clone)
    /// };
    ///
    /// let v_clone = v_orig.clone();
    ///
    /// // This is the suggested, safe way.
    /// // It does copy the entire vector, though, into a new array.
    /// let v_collected = v_clone.into_iter()
    ///                          .map(Some)
    ///                          .collect::<Vec<Option<&i32>>>();
    ///
    /// let v_clone = v_orig.clone();
    ///
    /// // This is the proper no-copy, unsafe way of "transmuting" a `Vec`, without relying on the
    /// // data layout. Instead of literally calling `transmute`, we perform a pointer cast, but
    /// // in terms of converting the original inner type (`&i32`) to the new one (`Option<&i32>`),
    /// // this has all the same caveats. Besides the information provided above, also consult the
    /// // [`from_raw_parts`] documentation.
    /// let v_from_raw = unsafe {
    // FIXME Update this when vec_into_raw_parts is stabilized
    ///     // Ensure the original vector is not dropped.
    ///     let mut v_clone = std::mem::ManuallyDrop::new(v_clone);
    ///     Vec::from_raw_parts(v_clone.as_mut_ptr() as *mut Option<&i32>,
    ///                         v_clone.len(),
    ///                         v_clone.capacity())
    /// };
    /// ```
    ///
    /// [`from_raw_parts`]: ../../std/vec/struct.Vec.html#method.from_raw_parts
    ///
    /// Implementing `split_at_mut`:
    ///
    /// ```
    /// use std::{slice, mem};
    ///
    /// // There are multiple ways to do this, and there are multiple problems
    /// // with the following (transmute) way.
    /// fn split_at_mut_transmute<T>(slice: &mut [T], mid: usize)
    ///                              -> (&mut [T], &mut [T]) {
    ///     let len = slice.len();
    ///     assert!(mid <= len);
    ///     unsafe {
    ///         let slice2 = mem::transmute::<&mut [T], &mut [T]>(slice);
    ///         // first: transmute is not type safe; all it checks is that T and
    ///         // U are of the same size. Second, right here, you have two
    ///         // mutable references pointing to the same memory.
    ///         (&mut slice[0..mid], &mut slice2[mid..len])
    ///     }
    /// }
    ///
    /// // This gets rid of the type safety problems; `&mut *` will *only* give
    /// // you an `&mut T` from an `&mut T` or `*mut T`.
    /// fn split_at_mut_casts<T>(slice: &mut [T], mid: usize)
    ///                          -> (&mut [T], &mut [T]) {
    ///     let len = slice.len();
    ///     assert!(mid <= len);
    ///     unsafe {
    ///         let slice2 = &mut *(slice as *mut [T]);
    ///         // however, you still have two mutable references pointing to
    ///         // the same memory.
    ///         (&mut slice[0..mid], &mut slice2[mid..len])
    ///     }
    /// }
    ///
    /// // This is how the standard library does it. This is the best method, if
    /// // you need to do something like this
    /// fn split_at_stdlib<T>(slice: &mut [T], mid: usize)
    ///                       -> (&mut [T], &mut [T]) {
    ///     let len = slice.len();
    ///     assert!(mid <= len);
    ///     unsafe {
    ///         let ptr = slice.as_mut_ptr();
    ///         // This now has three mutable references pointing at the same
    ///         // memory. `slice`, the rvalue ret.0, and the rvalue ret.1.
    ///         // `slice` is never used after `let ptr = ...`, and so one can
    ///         // treat it as "dead", and therefore, you only have two real
    ///         // mutable slices.
    ///         (slice::from_raw_parts_mut(ptr, mid),
    ///          slice::from_raw_parts_mut(ptr.add(mid), len - mid))
    ///     }
    /// }
    /// ```
    #[stable(feature = "rust1", since = "1.0.0")]
    #[rustc_allowed_through_unstable_modules]
    #[rustc_const_stable(feature = "const_transmute", since = "1.56.0")]
    #[rustc_diagnostic_item = "transmute"]
    #[rustc_nounwind]
    pub fn transmute<Src, Dst>(src: Src) -> Dst;

    /// Like [`transmute`], but even less checked at compile-time: rather than
    /// giving an error for `size_of::<Src>() != size_of::<Dst>()`, it's
    /// **Undefined Behaviour** at runtime.
    ///
    /// Prefer normal `transmute` where possible, for the extra checking, since
    /// both do exactly the same thing at runtime, if they both compile.
    ///
    /// This is not expected to ever be exposed directly to users, rather it
    /// may eventually be exposed through some more-constrained API.
    #[rustc_const_stable(feature = "const_transmute", since = "1.56.0")]
    #[rustc_nounwind]
    pub fn transmute_unchecked<Src, Dst>(src: Src) -> Dst;

    /// Returns `true` if the actual type given as `T` requires drop
    /// glue; returns `false` if the actual type provided for `T`
    /// implements `Copy`.
    ///
    /// If the actual type neither requires drop glue nor implements
    /// `Copy`, then the return value of this function is unspecified.
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// The stabilized version of this intrinsic is [`mem::needs_drop`](crate::mem::needs_drop).
    #[rustc_const_stable(feature = "const_needs_drop", since = "1.40.0")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn needs_drop<T: ?Sized>() -> bool;

    /// Calculates the offset from a pointer.
    ///
    /// This is implemented as an intrinsic to avoid converting to and from an
    /// integer, since the conversion would throw away aliasing information.
    ///
    /// This can only be used with `Ptr` as a raw pointer type (`*mut` or `*const`)
    /// to a `Sized` pointee and with `Delta` as `usize` or `isize`.  Any other
    /// instantiations may arbitrarily misbehave, and that's *not* a compiler bug.
    ///
    /// # Safety
    ///
    /// Both the starting and resulting pointer must be either in bounds or one
    /// byte past the end of an allocated object. If either pointer is out of
    /// bounds or arithmetic overflow occurs then any further use of the
    /// returned value will result in undefined behavior.
    ///
    /// The stabilized version of this intrinsic is [`pointer::offset`].
    #[must_use = "returns a new pointer rather than modifying its argument"]
    #[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
    #[rustc_nounwind]
    pub fn offset<Ptr, Delta>(dst: Ptr, offset: Delta) -> Ptr;

    /// Calculates the offset from a pointer, potentially wrapping.
    ///
    /// This is implemented as an intrinsic to avoid converting to and from an
    /// integer, since the conversion inhibits certain optimizations.
    ///
    /// # Safety
    ///
    /// Unlike the `offset` intrinsic, this intrinsic does not restrict the
    /// resulting pointer to point into or one byte past the end of an allocated
    /// object, and it wraps with two's complement arithmetic. The resulting
    /// value is not necessarily valid to be used to actually access memory.
    ///
    /// The stabilized version of this intrinsic is [`pointer::wrapping_offset`].
    #[must_use = "returns a new pointer rather than modifying its argument"]
    #[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
    #[rustc_nounwind]
    pub fn arith_offset<T>(dst: *const T, offset: isize) -> *const T;

    /// Masks out bits of the pointer according to a mask.
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// Consider using [`pointer::mask`] instead.
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn ptr_mask<T>(ptr: *const T, mask: usize) -> *const T;

    /// Equivalent to the appropriate `llvm.memcpy.p0i8.0i8.*` intrinsic, with
    /// a size of `count` * `size_of::<T>()` and an alignment of
    /// `min_align_of::<T>()`
    ///
    /// The volatile parameter is set to `true`, so it will not be optimized out
    /// unless size is equal to zero.
    ///
    /// This intrinsic does not have a stable counterpart.
    #[rustc_nounwind]
    pub fn volatile_copy_nonoverlapping_memory<T>(dst: *mut T, src: *const T, count: usize);
    /// Equivalent to the appropriate `llvm.memmove.p0i8.0i8.*` intrinsic, with
    /// a size of `count * size_of::<T>()` and an alignment of
    /// `min_align_of::<T>()`
    ///
    /// The volatile parameter is set to `true`, so it will not be optimized out
    /// unless size is equal to zero.
    ///
    /// This intrinsic does not have a stable counterpart.
    #[rustc_nounwind]
    pub fn volatile_copy_memory<T>(dst: *mut T, src: *const T, count: usize);
    /// Equivalent to the appropriate `llvm.memset.p0i8.*` intrinsic, with a
    /// size of `count * size_of::<T>()` and an alignment of
    /// `min_align_of::<T>()`.
    ///
    /// The volatile parameter is set to `true`, so it will not be optimized out
    /// unless size is equal to zero.
    ///
    /// This intrinsic does not have a stable counterpart.
    #[rustc_nounwind]
    pub fn volatile_set_memory<T>(dst: *mut T, val: u8, count: usize);

    /// Performs a volatile load from the `src` pointer.
    ///
    /// The stabilized version of this intrinsic is [`core::ptr::read_volatile`].
    #[rustc_nounwind]
    pub fn volatile_load<T>(src: *const T) -> T;
    /// Performs a volatile store to the `dst` pointer.
    ///
    /// The stabilized version of this intrinsic is [`core::ptr::write_volatile`].
    #[rustc_nounwind]
    pub fn volatile_store<T>(dst: *mut T, val: T);

    /// Performs a volatile load from the `src` pointer
    /// The pointer is not required to be aligned.
    ///
    /// This intrinsic does not have a stable counterpart.
    #[rustc_nounwind]
    #[rustc_diagnostic_item = "intrinsics_unaligned_volatile_load"]
    pub fn unaligned_volatile_load<T>(src: *const T) -> T;
    /// Performs a volatile store to the `dst` pointer.
    /// The pointer is not required to be aligned.
    ///
    /// This intrinsic does not have a stable counterpart.
    #[rustc_nounwind]
    #[rustc_diagnostic_item = "intrinsics_unaligned_volatile_store"]
    pub fn unaligned_volatile_store<T>(dst: *mut T, val: T);

    /// Returns the square root of an `f32`
    ///
    /// The stabilized version of this intrinsic is
    /// [`f32::sqrt`](../../std/primitive.f32.html#method.sqrt)
    #[rustc_nounwind]
    pub fn sqrtf32(x: f32) -> f32;
    /// Returns the square root of an `f64`
    ///
    /// The stabilized version of this intrinsic is
    /// [`f64::sqrt`](../../std/primitive.f64.html#method.sqrt)
    #[rustc_nounwind]
    pub fn sqrtf64(x: f64) -> f64;

    /// Raises an `f32` to an integer power.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f32::powi`](../../std/primitive.f32.html#method.powi)
    #[rustc_nounwind]
    pub fn powif32(a: f32, x: i32) -> f32;
    /// Raises an `f64` to an integer power.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f64::powi`](../../std/primitive.f64.html#method.powi)
    #[rustc_nounwind]
    pub fn powif64(a: f64, x: i32) -> f64;

    /// Returns the sine of an `f32`.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f32::sin`](../../std/primitive.f32.html#method.sin)
    #[rustc_nounwind]
    pub fn sinf32(x: f32) -> f32;
    /// Returns the sine of an `f64`.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f64::sin`](../../std/primitive.f64.html#method.sin)
    #[rustc_nounwind]
    pub fn sinf64(x: f64) -> f64;

    /// Returns the cosine of an `f32`.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f32::cos`](../../std/primitive.f32.html#method.cos)
    #[rustc_nounwind]
    pub fn cosf32(x: f32) -> f32;
    /// Returns the cosine of an `f64`.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f64::cos`](../../std/primitive.f64.html#method.cos)
    #[rustc_nounwind]
    pub fn cosf64(x: f64) -> f64;

    /// Raises an `f32` to an `f32` power.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f32::powf`](../../std/primitive.f32.html#method.powf)
    #[rustc_nounwind]
    pub fn powf32(a: f32, x: f32) -> f32;
    /// Raises an `f64` to an `f64` power.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f64::powf`](../../std/primitive.f64.html#method.powf)
    #[rustc_nounwind]
    pub fn powf64(a: f64, x: f64) -> f64;

    /// Returns the exponential of an `f32`.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f32::exp`](../../std/primitive.f32.html#method.exp)
    #[rustc_nounwind]
    pub fn expf32(x: f32) -> f32;
    /// Returns the exponential of an `f64`.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f64::exp`](../../std/primitive.f64.html#method.exp)
    #[rustc_nounwind]
    pub fn expf64(x: f64) -> f64;

    /// Returns 2 raised to the power of an `f32`.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f32::exp2`](../../std/primitive.f32.html#method.exp2)
    #[rustc_nounwind]
    pub fn exp2f32(x: f32) -> f32;
    /// Returns 2 raised to the power of an `f64`.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f64::exp2`](../../std/primitive.f64.html#method.exp2)
    #[rustc_nounwind]
    pub fn exp2f64(x: f64) -> f64;

    /// Returns the natural logarithm of an `f32`.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f32::ln`](../../std/primitive.f32.html#method.ln)
    #[rustc_nounwind]
    pub fn logf32(x: f32) -> f32;
    /// Returns the natural logarithm of an `f64`.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f64::ln`](../../std/primitive.f64.html#method.ln)
    #[rustc_nounwind]
    pub fn logf64(x: f64) -> f64;

    /// Returns the base 10 logarithm of an `f32`.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f32::log10`](../../std/primitive.f32.html#method.log10)
    #[rustc_nounwind]
    pub fn log10f32(x: f32) -> f32;
    /// Returns the base 10 logarithm of an `f64`.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f64::log10`](../../std/primitive.f64.html#method.log10)
    #[rustc_nounwind]
    pub fn log10f64(x: f64) -> f64;

    /// Returns the base 2 logarithm of an `f32`.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f32::log2`](../../std/primitive.f32.html#method.log2)
    #[rustc_nounwind]
    pub fn log2f32(x: f32) -> f32;
    /// Returns the base 2 logarithm of an `f64`.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f64::log2`](../../std/primitive.f64.html#method.log2)
    #[rustc_nounwind]
    pub fn log2f64(x: f64) -> f64;

    /// Returns `a * b + c` for `f32` values.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f32::mul_add`](../../std/primitive.f32.html#method.mul_add)
    #[rustc_nounwind]
    pub fn fmaf32(a: f32, b: f32, c: f32) -> f32;
    /// Returns `a * b + c` for `f64` values.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f64::mul_add`](../../std/primitive.f64.html#method.mul_add)
    #[rustc_nounwind]
    pub fn fmaf64(a: f64, b: f64, c: f64) -> f64;

    /// Returns the absolute value of an `f32`.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f32::abs`](../../std/primitive.f32.html#method.abs)
    #[rustc_nounwind]
    pub fn fabsf32(x: f32) -> f32;
    /// Returns the absolute value of an `f64`.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f64::abs`](../../std/primitive.f64.html#method.abs)
    #[rustc_nounwind]
    pub fn fabsf64(x: f64) -> f64;

    /// Returns the minimum of two `f32` values.
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f32::min`]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn minnumf32(x: f32, y: f32) -> f32;
    /// Returns the minimum of two `f64` values.
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f64::min`]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn minnumf64(x: f64, y: f64) -> f64;
    /// Returns the maximum of two `f32` values.
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f32::max`]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn maxnumf32(x: f32, y: f32) -> f32;
    /// Returns the maximum of two `f64` values.
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f64::max`]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn maxnumf64(x: f64, y: f64) -> f64;

    /// Copies the sign from `y` to `x` for `f32` values.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f32::copysign`](../../std/primitive.f32.html#method.copysign)
    #[rustc_nounwind]
    pub fn copysignf32(x: f32, y: f32) -> f32;
    /// Copies the sign from `y` to `x` for `f64` values.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f64::copysign`](../../std/primitive.f64.html#method.copysign)
    #[rustc_nounwind]
    pub fn copysignf64(x: f64, y: f64) -> f64;

    /// Returns the largest integer less than or equal to an `f32`.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f32::floor`](../../std/primitive.f32.html#method.floor)
    #[rustc_nounwind]
    pub fn floorf32(x: f32) -> f32;
    /// Returns the largest integer less than or equal to an `f64`.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f64::floor`](../../std/primitive.f64.html#method.floor)
    #[rustc_nounwind]
    pub fn floorf64(x: f64) -> f64;

    /// Returns the smallest integer greater than or equal to an `f32`.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f32::ceil`](../../std/primitive.f32.html#method.ceil)
    #[rustc_nounwind]
    pub fn ceilf32(x: f32) -> f32;
    /// Returns the smallest integer greater than or equal to an `f64`.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f64::ceil`](../../std/primitive.f64.html#method.ceil)
    #[rustc_nounwind]
    pub fn ceilf64(x: f64) -> f64;

    /// Returns the integer part of an `f32`.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f32::trunc`](../../std/primitive.f32.html#method.trunc)
    #[rustc_nounwind]
    pub fn truncf32(x: f32) -> f32;
    /// Returns the integer part of an `f64`.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f64::trunc`](../../std/primitive.f64.html#method.trunc)
    #[rustc_nounwind]
    pub fn truncf64(x: f64) -> f64;

    /// Returns the nearest integer to an `f32`. Changing the rounding mode is not possible in Rust,
    /// so this rounds half-way cases to the number with an even least significant digit.
    ///
    /// May raise an inexact floating-point exception if the argument is not an integer.
    /// However, Rust assumes floating-point exceptions cannot be observed, so these exceptions
    /// cannot actually be utilized from Rust code.
    /// In other words, this intrinsic is equivalent in behavior to `nearbyintf32` and `roundevenf32`.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f32::round_ties_even`](../../std/primitive.f32.html#method.round_ties_even)
    #[rustc_nounwind]
    pub fn rintf32(x: f32) -> f32;
    /// Returns the nearest integer to an `f64`. Changing the rounding mode is not possible in Rust,
    /// so this rounds half-way cases to the number with an even least significant digit.
    ///
    /// May raise an inexact floating-point exception if the argument is not an integer.
    /// However, Rust assumes floating-point exceptions cannot be observed, so these exceptions
    /// cannot actually be utilized from Rust code.
    /// In other words, this intrinsic is equivalent in behavior to `nearbyintf64` and `roundevenf64`.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f64::round_ties_even`](../../std/primitive.f64.html#method.round_ties_even)
    #[rustc_nounwind]
    pub fn rintf64(x: f64) -> f64;

    /// Returns the nearest integer to an `f32`. Changing the rounding mode is not possible in Rust,
    /// so this rounds half-way cases to the number with an even least significant digit.
    ///
    /// This intrinsic does not have a stable counterpart.
    #[rustc_nounwind]
    pub fn nearbyintf32(x: f32) -> f32;
    /// Returns the nearest integer to an `f64`. Changing the rounding mode is not possible in Rust,
    /// so this rounds half-way cases to the number with an even least significant digit.
    ///
    /// This intrinsic does not have a stable counterpart.
    #[rustc_nounwind]
    pub fn nearbyintf64(x: f64) -> f64;

    /// Returns the nearest integer to an `f32`. Rounds half-way cases away from zero.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f32::round`](../../std/primitive.f32.html#method.round)
    #[rustc_nounwind]
    pub fn roundf32(x: f32) -> f32;
    /// Returns the nearest integer to an `f64`. Rounds half-way cases away from zero.
    ///
    /// The stabilized version of this intrinsic is
    /// [`f64::round`](../../std/primitive.f64.html#method.round)
    #[rustc_nounwind]
    pub fn roundf64(x: f64) -> f64;

    /// Returns the nearest integer to an `f32`. Rounds half-way cases to the number
    /// with an even least significant digit.
    ///
    /// This intrinsic does not have a stable counterpart.
    #[rustc_nounwind]
    pub fn roundevenf32(x: f32) -> f32;
    /// Returns the nearest integer to an `f64`. Rounds half-way cases to the number
    /// with an even least significant digit.
    ///
    /// This intrinsic does not have a stable counterpart.
    #[rustc_nounwind]
    pub fn roundevenf64(x: f64) -> f64;

    /// Float addition that allows optimizations based on algebraic rules.
    /// May assume inputs are finite.
    ///
    /// This intrinsic does not have a stable counterpart.
    #[rustc_nounwind]
    pub fn fadd_fast<T: Copy>(a: T, b: T) -> T;

    /// Float subtraction that allows optimizations based on algebraic rules.
    /// May assume inputs are finite.
    ///
    /// This intrinsic does not have a stable counterpart.
    #[rustc_nounwind]
    pub fn fsub_fast<T: Copy>(a: T, b: T) -> T;

    /// Float multiplication that allows optimizations based on algebraic rules.
    /// May assume inputs are finite.
    ///
    /// This intrinsic does not have a stable counterpart.
    #[rustc_nounwind]
    pub fn fmul_fast<T: Copy>(a: T, b: T) -> T;

    /// Float division that allows optimizations based on algebraic rules.
    /// May assume inputs are finite.
    ///
    /// This intrinsic does not have a stable counterpart.
    #[rustc_nounwind]
    pub fn fdiv_fast<T: Copy>(a: T, b: T) -> T;

    /// Float remainder that allows optimizations based on algebraic rules.
    /// May assume inputs are finite.
    ///
    /// This intrinsic does not have a stable counterpart.
    #[rustc_nounwind]
    pub fn frem_fast<T: Copy>(a: T, b: T) -> T;

    /// Convert with LLVM’s fptoui/fptosi, which may return undef for values out of range
    /// (<https://github.com/rust-lang/rust/issues/10184>)
    ///
    /// Stabilized as [`f32::to_int_unchecked`] and [`f64::to_int_unchecked`].
    #[rustc_nounwind]
    pub fn float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;

    /// Returns the number of bits set in an integer type `T`
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// The stabilized versions of this intrinsic are available on the integer
    /// primitives via the `count_ones` method. For example,
    /// [`u32::count_ones`]
    #[rustc_const_stable(feature = "const_ctpop", since = "1.40.0")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn ctpop<T: Copy>(x: T) -> T;

    /// Returns the number of leading unset bits (zeroes) in an integer type `T`.
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// The stabilized versions of this intrinsic are available on the integer
    /// primitives via the `leading_zeros` method. For example,
    /// [`u32::leading_zeros`]
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(core_intrinsics)]
    /// # #![allow(internal_features)]
    ///
    /// use std::intrinsics::ctlz;
    ///
    /// let x = 0b0001_1100_u8;
    /// let num_leading = ctlz(x);
    /// assert_eq!(num_leading, 3);
    /// ```
    ///
    /// An `x` with value `0` will return the bit width of `T`.
    ///
    /// ```
    /// #![feature(core_intrinsics)]
    /// # #![allow(internal_features)]
    ///
    /// use std::intrinsics::ctlz;
    ///
    /// let x = 0u16;
    /// let num_leading = ctlz(x);
    /// assert_eq!(num_leading, 16);
    /// ```
    #[rustc_const_stable(feature = "const_ctlz", since = "1.40.0")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn ctlz<T: Copy>(x: T) -> T;

    /// Like `ctlz`, but extra-unsafe as it returns `undef` when
    /// given an `x` with value `0`.
    ///
    /// This intrinsic does not have a stable counterpart.
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(core_intrinsics)]
    /// # #![allow(internal_features)]
    ///
    /// use std::intrinsics::ctlz_nonzero;
    ///
    /// let x = 0b0001_1100_u8;
    /// let num_leading = unsafe { ctlz_nonzero(x) };
    /// assert_eq!(num_leading, 3);
    /// ```
    #[rustc_const_stable(feature = "constctlz", since = "1.50.0")]
    #[rustc_nounwind]
    pub fn ctlz_nonzero<T: Copy>(x: T) -> T;

    /// Returns the number of trailing unset bits (zeroes) in an integer type `T`.
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// The stabilized versions of this intrinsic are available on the integer
    /// primitives via the `trailing_zeros` method. For example,
    /// [`u32::trailing_zeros`]
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(core_intrinsics)]
    /// # #![allow(internal_features)]
    ///
    /// use std::intrinsics::cttz;
    ///
    /// let x = 0b0011_1000_u8;
    /// let num_trailing = cttz(x);
    /// assert_eq!(num_trailing, 3);
    /// ```
    ///
    /// An `x` with value `0` will return the bit width of `T`:
    ///
    /// ```
    /// #![feature(core_intrinsics)]
    /// # #![allow(internal_features)]
    ///
    /// use std::intrinsics::cttz;
    ///
    /// let x = 0u16;
    /// let num_trailing = cttz(x);
    /// assert_eq!(num_trailing, 16);
    /// ```
    #[rustc_const_stable(feature = "const_cttz", since = "1.40.0")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn cttz<T: Copy>(x: T) -> T;

    /// Like `cttz`, but extra-unsafe as it returns `undef` when
    /// given an `x` with value `0`.
    ///
    /// This intrinsic does not have a stable counterpart.
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(core_intrinsics)]
    /// # #![allow(internal_features)]
    ///
    /// use std::intrinsics::cttz_nonzero;
    ///
    /// let x = 0b0011_1000_u8;
    /// let num_trailing = unsafe { cttz_nonzero(x) };
    /// assert_eq!(num_trailing, 3);
    /// ```
    #[rustc_const_stable(feature = "const_cttz_nonzero", since = "1.53.0")]
    #[rustc_nounwind]
    pub fn cttz_nonzero<T: Copy>(x: T) -> T;

    /// Reverses the bytes in an integer type `T`.
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// The stabilized versions of this intrinsic are available on the integer
    /// primitives via the `swap_bytes` method. For example,
    /// [`u32::swap_bytes`]
    #[rustc_const_stable(feature = "const_bswap", since = "1.40.0")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn bswap<T: Copy>(x: T) -> T;

    /// Reverses the bits in an integer type `T`.
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// The stabilized versions of this intrinsic are available on the integer
    /// primitives via the `reverse_bits` method. For example,
    /// [`u32::reverse_bits`]
    #[rustc_const_stable(feature = "const_bitreverse", since = "1.40.0")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn bitreverse<T: Copy>(x: T) -> T;

    /// Performs checked integer addition.
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// The stabilized versions of this intrinsic are available on the integer
    /// primitives via the `overflowing_add` method. For example,
    /// [`u32::overflowing_add`]
    #[rustc_const_stable(feature = "const_int_overflow", since = "1.40.0")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn add_with_overflow<T: Copy>(x: T, y: T) -> (T, bool);

    /// Performs checked integer subtraction
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// The stabilized versions of this intrinsic are available on the integer
    /// primitives via the `overflowing_sub` method. For example,
    /// [`u32::overflowing_sub`]
    #[rustc_const_stable(feature = "const_int_overflow", since = "1.40.0")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn sub_with_overflow<T: Copy>(x: T, y: T) -> (T, bool);

    /// Performs checked integer multiplication
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// The stabilized versions of this intrinsic are available on the integer
    /// primitives via the `overflowing_mul` method. For example,
    /// [`u32::overflowing_mul`]
    #[rustc_const_stable(feature = "const_int_overflow", since = "1.40.0")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn mul_with_overflow<T: Copy>(x: T, y: T) -> (T, bool);

    /// Performs an exact division, resulting in undefined behavior where
    /// `x % y != 0` or `y == 0` or `x == T::MIN && y == -1`
    ///
    /// This intrinsic does not have a stable counterpart.
    #[rustc_const_unstable(feature = "const_exact_div", issue = "none")]
    #[rustc_nounwind]
    pub fn exact_div<T: Copy>(x: T, y: T) -> T;

    /// Performs an unchecked division, resulting in undefined behavior
    /// where `y == 0` or `x == T::MIN && y == -1`
    ///
    /// Safe wrappers for this intrinsic are available on the integer
    /// primitives via the `checked_div` method. For example,
    /// [`u32::checked_div`]
    #[rustc_const_stable(feature = "const_int_unchecked_div", since = "1.52.0")]
    #[rustc_nounwind]
    pub fn unchecked_div<T: Copy>(x: T, y: T) -> T;
    /// Returns the remainder of an unchecked division, resulting in
    /// undefined behavior when `y == 0` or `x == T::MIN && y == -1`
    ///
    /// Safe wrappers for this intrinsic are available on the integer
    /// primitives via the `checked_rem` method. For example,
    /// [`u32::checked_rem`]
    #[rustc_const_stable(feature = "const_int_unchecked_rem", since = "1.52.0")]
    #[rustc_nounwind]
    pub fn unchecked_rem<T: Copy>(x: T, y: T) -> T;

    /// Performs an unchecked left shift, resulting in undefined behavior when
    /// `y < 0` or `y >= N`, where N is the width of T in bits.
    ///
    /// Safe wrappers for this intrinsic are available on the integer
    /// primitives via the `checked_shl` method. For example,
    /// [`u32::checked_shl`]
    #[rustc_const_stable(feature = "const_int_unchecked", since = "1.40.0")]
    #[rustc_nounwind]
    pub fn unchecked_shl<T: Copy>(x: T, y: T) -> T;
    /// Performs an unchecked right shift, resulting in undefined behavior when
    /// `y < 0` or `y >= N`, where N is the width of T in bits.
    ///
    /// Safe wrappers for this intrinsic are available on the integer
    /// primitives via the `checked_shr` method. For example,
    /// [`u32::checked_shr`]
    #[rustc_const_stable(feature = "const_int_unchecked", since = "1.40.0")]
    #[rustc_nounwind]
    pub fn unchecked_shr<T: Copy>(x: T, y: T) -> T;

    /// Returns the result of an unchecked addition, resulting in
    /// undefined behavior when `x + y > T::MAX` or `x + y < T::MIN`.
    ///
    /// This intrinsic does not have a stable counterpart.
    #[rustc_const_unstable(feature = "const_int_unchecked_arith", issue = "none")]
    #[rustc_nounwind]
    pub fn unchecked_add<T: Copy>(x: T, y: T) -> T;

    /// Returns the result of an unchecked subtraction, resulting in
    /// undefined behavior when `x - y > T::MAX` or `x - y < T::MIN`.
    ///
    /// This intrinsic does not have a stable counterpart.
    #[rustc_const_unstable(feature = "const_int_unchecked_arith", issue = "none")]
    #[rustc_nounwind]
    pub fn unchecked_sub<T: Copy>(x: T, y: T) -> T;

    /// Returns the result of an unchecked multiplication, resulting in
    /// undefined behavior when `x * y > T::MAX` or `x * y < T::MIN`.
    ///
    /// This intrinsic does not have a stable counterpart.
    #[rustc_const_unstable(feature = "const_int_unchecked_arith", issue = "none")]
    #[rustc_nounwind]
    pub fn unchecked_mul<T: Copy>(x: T, y: T) -> T;

    /// Performs rotate left.
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// The stabilized versions of this intrinsic are available on the integer
    /// primitives via the `rotate_left` method. For example,
    /// [`u32::rotate_left`]
    #[rustc_const_stable(feature = "const_int_rotate", since = "1.40.0")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn rotate_left<T: Copy>(x: T, y: T) -> T;

    /// Performs rotate right.
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// The stabilized versions of this intrinsic are available on the integer
    /// primitives via the `rotate_right` method. For example,
    /// [`u32::rotate_right`]
    #[rustc_const_stable(feature = "const_int_rotate", since = "1.40.0")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn rotate_right<T: Copy>(x: T, y: T) -> T;

    /// Returns (a + b) mod 2<sup>N</sup>, where N is the width of T in bits.
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// The stabilized versions of this intrinsic are available on the integer
    /// primitives via the `wrapping_add` method. For example,
    /// [`u32::wrapping_add`]
    #[rustc_const_stable(feature = "const_int_wrapping", since = "1.40.0")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn wrapping_add<T: Copy>(a: T, b: T) -> T;
    /// Returns (a - b) mod 2<sup>N</sup>, where N is the width of T in bits.
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// The stabilized versions of this intrinsic are available on the integer
    /// primitives via the `wrapping_sub` method. For example,
    /// [`u32::wrapping_sub`]
    #[rustc_const_stable(feature = "const_int_wrapping", since = "1.40.0")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn wrapping_sub<T: Copy>(a: T, b: T) -> T;
    /// Returns (a * b) mod 2<sup>N</sup>, where N is the width of T in bits.
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// The stabilized versions of this intrinsic are available on the integer
    /// primitives via the `wrapping_mul` method. For example,
    /// [`u32::wrapping_mul`]
    #[rustc_const_stable(feature = "const_int_wrapping", since = "1.40.0")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn wrapping_mul<T: Copy>(a: T, b: T) -> T;

    /// Computes `a + b`, saturating at numeric bounds.
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// The stabilized versions of this intrinsic are available on the integer
    /// primitives via the `saturating_add` method. For example,
    /// [`u32::saturating_add`]
    #[rustc_const_stable(feature = "const_int_saturating", since = "1.40.0")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn saturating_add<T: Copy>(a: T, b: T) -> T;
    /// Computes `a - b`, saturating at numeric bounds.
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// The stabilized versions of this intrinsic are available on the integer
    /// primitives via the `saturating_sub` method. For example,
    /// [`u32::saturating_sub`]
    #[rustc_const_stable(feature = "const_int_saturating", since = "1.40.0")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn saturating_sub<T: Copy>(a: T, b: T) -> T;

    /// This is an implementation detail of [`crate::ptr::read`] and should
    /// not be used anywhere else.  See its comments for why this exists.
    ///
    /// This intrinsic can *only* be called where the pointer is a local without
    /// projections (`read_via_copy(ptr)`, not `read_via_copy(*ptr)`) so that it
    /// trivially obeys runtime-MIR rules about derefs in operands.
    #[rustc_const_stable(feature = "const_ptr_read", since = "1.71.0")]
    #[rustc_nounwind]
    pub fn read_via_copy<T>(ptr: *const T) -> T;

    /// This is an implementation detail of [`crate::ptr::write`] and should
    /// not be used anywhere else.  See its comments for why this exists.
    ///
    /// This intrinsic can *only* be called where the pointer is a local without
    /// projections (`write_via_move(ptr, x)`, not `write_via_move(*ptr, x)`) so
    /// that it trivially obeys runtime-MIR rules about derefs in operands.
    #[rustc_const_unstable(feature = "const_ptr_write", issue = "86302")]
    #[rustc_nounwind]
    pub fn write_via_move<T>(ptr: *mut T, value: T);

    /// Returns the value of the discriminant for the variant in 'v';
    /// if `T` has no discriminant, returns `0`.
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// The stabilized version of this intrinsic is [`core::mem::discriminant`].
    #[rustc_const_stable(feature = "const_discriminant", since = "1.75.0")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn discriminant_value<T>(v: &T) -> <T as DiscriminantKind>::Discriminant;

    /// Returns the number of variants of the type `T` cast to a `usize`;
    /// if `T` has no variants, returns `0`. Uninhabited variants will be counted.
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    ///
    /// The to-be-stabilized version of this intrinsic is [`mem::variant_count`].
    #[rustc_const_unstable(feature = "variant_count", issue = "73662")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn variant_count<T>() -> usize;

    /// Rust's "try catch" construct which invokes the function pointer `try_fn`
    /// with the data pointer `data`.
    ///
    /// The third argument is a function called if a panic occurs. This function
    /// takes the data pointer and a pointer to the target-specific exception
    /// object that was caught. For more information see the compiler's
    /// source as well as std's catch implementation.
    ///
    /// `catch_fn` must not unwind.
    #[rustc_nounwind]
    pub fn r#try(try_fn: fn(*mut u8), data: *mut u8, catch_fn: fn(*mut u8, *mut u8)) -> i32;

    /// Emits a `!nontemporal` store according to LLVM (see their docs).
    /// Probably will never become stable.
    ///
    /// Do NOT use this intrinsic; "nontemporal" operations do not exist in our memory model!
    /// It exists to support current stdarch, but the plan is to change stdarch and remove this intrinsic.
    /// See <https://github.com/rust-lang/rust/issues/114582> for some more discussion.
    #[rustc_nounwind]
    pub fn nontemporal_store<T>(ptr: *mut T, val: T);

    /// See documentation of `<*const T>::offset_from` for details.
    #[rustc_const_stable(feature = "const_ptr_offset_from", since = "1.65.0")]
    #[rustc_nounwind]
    pub fn ptr_offset_from<T>(ptr: *const T, base: *const T) -> isize;

    /// See documentation of `<*const T>::sub_ptr` for details.
    #[rustc_const_unstable(feature = "const_ptr_sub_ptr", issue = "95892")]
    #[rustc_nounwind]
    pub fn ptr_offset_from_unsigned<T>(ptr: *const T, base: *const T) -> usize;

    /// See documentation of `<*const T>::guaranteed_eq` for details.
    /// Returns `2` if the result is unknown.
    /// Returns `1` if the pointers are guaranteed equal
    /// Returns `0` if the pointers are guaranteed inequal
    ///
    /// Note that, unlike most intrinsics, this is safe to call;
    /// it does not require an `unsafe` block.
    /// Therefore, implementations must not require the user to uphold
    /// any safety invariants.
    #[rustc_const_unstable(feature = "const_raw_ptr_comparison", issue = "53020")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn ptr_guaranteed_cmp<T>(ptr: *const T, other: *const T) -> u8;

    /// Allocates a block of memory at compile time.
    /// At runtime, just returns a null pointer.
    ///
    /// # Safety
    ///
    /// - The `align` argument must be a power of two.
    ///    - At compile time, a compile error occurs if this constraint is violated.
    ///    - At runtime, it is not checked.
    #[rustc_const_unstable(feature = "const_heap", issue = "79597")]
    #[rustc_nounwind]
    pub fn const_allocate(size: usize, align: usize) -> *mut u8;

    /// Deallocates a memory which allocated by `intrinsics::const_allocate` at compile time.
    /// At runtime, does nothing.
    ///
    /// # Safety
    ///
    /// - The `align` argument must be a power of two.
    ///    - At compile time, a compile error occurs if this constraint is violated.
    ///    - At runtime, it is not checked.
    /// - If the `ptr` is created in an another const, this intrinsic doesn't deallocate it.
    /// - If the `ptr` is pointing to a local variable, this intrinsic doesn't deallocate it.
    #[rustc_const_unstable(feature = "const_heap", issue = "79597")]
    #[rustc_nounwind]
    pub fn const_deallocate(ptr: *mut u8, size: usize, align: usize);

    /// Determines whether the raw bytes of the two values are equal.
    ///
    /// This is particularly handy for arrays, since it allows things like just
    /// comparing `i96`s instead of forcing `alloca`s for `[6 x i16]`.
    ///
    /// Above some backend-decided threshold this will emit calls to `memcmp`,
    /// like slice equality does, instead of causing massive code size.
    ///
    /// Since this works by comparing the underlying bytes, the actual `T` is
    /// not particularly important.  It will be used for its size and alignment,
    /// but any validity restrictions will be ignored, not enforced.
    ///
    /// # Safety
    ///
    /// It's UB to call this if any of the *bytes* in `*a` or `*b` are uninitialized or carry a
    /// pointer value.
    /// Note that this is a stricter criterion than just the *values* being
    /// fully-initialized: if `T` has padding, it's UB to call this intrinsic.
    ///
    /// (The implementation is allowed to branch on the results of comparisons,
    /// which is UB if any of their inputs are `undef`.)
    #[rustc_const_unstable(feature = "const_intrinsic_raw_eq", issue = "none")]
    #[rustc_nounwind]
    pub fn raw_eq<T>(a: &T, b: &T) -> bool;

    /// Lexicographically compare `[left, left + bytes)` and `[right, right + bytes)`
    /// as unsigned bytes, returning negative if `left` is less, zero if all the
    /// bytes match, or positive if `right` is greater.
    ///
    /// This underlies things like `<[u8]>::cmp`, and will usually lower to `memcmp`.
    ///
    /// # Safety
    ///
    /// `left` and `right` must each be [valid] for reads of `bytes` bytes.
    ///
    /// Note that this applies to the whole range, not just until the first byte
    /// that differs.  That allows optimizations that can read in large chunks.
    ///
    /// [valid]: crate::ptr#safety
    #[rustc_const_unstable(feature = "const_intrinsic_compare_bytes", issue = "none")]
    #[rustc_nounwind]
    pub fn compare_bytes(left: *const u8, right: *const u8, bytes: usize) -> i32;

    /// See documentation of [`std::hint::black_box`] for details.
    ///
    /// [`std::hint::black_box`]: crate::hint::black_box
    #[rustc_const_unstable(feature = "const_black_box", issue = "none")]
    #[rustc_safe_intrinsic]
    #[rustc_nounwind]
    pub fn black_box<T>(dummy: T) -> T;

    /// `ptr` must point to a vtable.
    /// The intrinsic will return the size stored in that vtable.
    #[rustc_nounwind]
    pub fn vtable_size(ptr: *const ()) -> usize;

    /// `ptr` must point to a vtable.
    /// The intrinsic will return the alignment stored in that vtable.
    #[rustc_nounwind]
    pub fn vtable_align(ptr: *const ()) -> usize;

    /// Selects which function to call depending on the context.
    ///
    /// If this function is evaluated at compile-time, then a call to this
    /// intrinsic will be replaced with a call to `called_in_const`. It gets
    /// replaced with a call to `called_at_rt` otherwise.
    ///
    /// # Type Requirements
    ///
    /// The two functions must be both function items. They cannot be function
    /// pointers or closures. The first function must be a `const fn`.
    ///
    /// `arg` will be the tupled arguments that will be passed to either one of
    /// the two functions, therefore, both functions must accept the same type of
    /// arguments. Both functions must return RET.
    ///
    /// # Safety
    ///
    /// The two functions must behave observably equivalent. Safe code in other
    /// crates may assume that calling a `const fn` at compile-time and at run-time
    /// produces the same result. A function that produces a different result when
    /// evaluated at run-time, or has any other observable side-effects, is
    /// *unsound*.
    ///
    /// Here is an example of how this could cause a problem:
    /// ```no_run
    /// #![feature(const_eval_select)]
    /// #![feature(core_intrinsics)]
    /// # #![allow(internal_features)]
    /// use std::hint::unreachable_unchecked;
    /// use std::intrinsics::const_eval_select;
    ///
    /// // Crate A
    /// pub const fn inconsistent() -> i32 {
    ///     fn runtime() -> i32 { 1 }
    ///     const fn compiletime() -> i32 { 2 }
    ///
    ///     unsafe {
    //          // ⚠ This code violates the required equivalence of `compiletime`
    ///         // and `runtime`.
    ///         const_eval_select((), compiletime, runtime)
    ///     }
    /// }
    ///
    /// // Crate B
    /// const X: i32 = inconsistent();
    /// let x = inconsistent();
    /// if x != X { unsafe { unreachable_unchecked(); }}
    /// ```
    ///
    /// This code causes Undefined Behavior when being run, since the
    /// `unreachable_unchecked` is actually being reached. The bug is in *crate A*,
    /// which violates the principle that a `const fn` must behave the same at
    /// compile-time and at run-time. The unsafe code in crate B is fine.
    #[rustc_const_unstable(feature = "const_eval_select", issue = "none")]
    pub fn const_eval_select<ARG: Tuple, F, G, RET>(
        arg: ARG,
        called_in_const: F,
        called_at_rt: G,
    ) -> RET
    where
        G: FnOnce<ARG, Output = RET>,
        F: FnOnce<ARG, Output = RET>;

    /// Returns whether the argument's value is statically known at
    /// compile-time.
    ///
    /// This is useful when there is a way of writing the code that will
    /// be *faster* when some variables have known values, but *slower*
    /// in the general case: an `if is_val_statically_known(var)` can be used
    /// to select between these two variants. The `if` will be optimized away
    /// and only the desired branch remains.
    ///
    /// Formally speaking, this function non-deterministically returns `true`
    /// or `false`, and the caller has to ensure sound behavior for both cases.
    /// In other words, the following code has *Undefined Behavior*:
    ///
    /// ```no_run
    /// #![feature(is_val_statically_known)]
    /// #![feature(core_intrinsics)]
    /// # #![allow(internal_features)]
    /// use std::hint::unreachable_unchecked;
    /// use std::intrinsics::is_val_statically_known;
    ///
    /// unsafe {
    ///    if !is_val_statically_known(0) { unreachable_unchecked(); }
    /// }
    /// ```
    ///
    /// This also means that the following code's behavior is unspecified; it
    /// may panic, or it may not:
    ///
    /// ```no_run
    /// #![feature(is_val_statically_known)]
    /// #![feature(core_intrinsics)]
    /// # #![allow(internal_features)]
    /// use std::intrinsics::is_val_statically_known;
    ///
    /// unsafe {
    ///     assert_eq!(is_val_statically_known(0), is_val_statically_known(0));
    /// }
    /// ```
    ///
    /// Unsafe code may not rely on `is_val_statically_known` returning any
    /// particular value, ever. However, the compiler will generally make it
    /// return `true` only if the value of the argument is actually known.
    ///
    /// When calling this in a `const fn`, both paths must be semantically
    /// equivalent, that is, the result of the `true` branch and the `false`
    /// branch must return the same value and have the same side-effects *no
    /// matter what*.
    #[rustc_const_unstable(feature = "is_val_statically_known", issue = "none")]
    #[rustc_nounwind]
    #[cfg(not(bootstrap))]
    pub fn is_val_statically_known<T: Copy>(arg: T) -> bool;
}

// FIXME: Seems using `unstable` here completely ignores `rustc_allow_const_fn_unstable`
// and thus compiling stage0 core doesn't work.
#[rustc_const_stable(feature = "is_val_statically_known", since = "0.0.0")]
#[cfg(bootstrap)]
pub const unsafe fn is_val_statically_known<T: Copy>(_arg: T) -> bool {
    false
}

// Some functions are defined here because they accidentally got made
// available in this module on stable. See <https://github.com/rust-lang/rust/issues/15702>.
// (`transmute` also falls into this category, but it cannot be wrapped due to the
// check that `T` and `U` have the same size.)

/// Check that the preconditions of an unsafe function are followed, if debug_assertions are on,
/// and only at runtime.
///
/// This macro should be called as `assert_unsafe_precondition!([Generics](name: Type) => Expression)`
/// where the names specified will be moved into the macro as captured variables, and defines an item
/// to call `const_eval_select` on. The tokens inside the square brackets are used to denote generics
/// for the function declarations and can be omitted if there is no generics.
///
/// # Safety
///
/// Invoking this macro is only sound if the following code is already UB when the passed
/// expression evaluates to false.
///
/// This macro expands to a check at runtime if debug_assertions is set. It has no effect at
/// compile time, but the semantics of the contained `const_eval_select` must be the same at
/// runtime and at compile time. Thus if the expression evaluates to false, this macro produces
/// different behavior at compile time and at runtime, and invoking it is incorrect.
///
/// So in a sense it is UB if this macro is useful, but we expect callers of `unsafe fn` to make
/// the occasional mistake, and this check should help them figure things out.
#[allow_internal_unstable(const_eval_select)] // permit this to be called in stably-const fn
macro_rules! assert_unsafe_precondition {
    ($name:expr, $([$($tt:tt)*])?($($i:ident:$ty:ty),*$(,)?) => $e:expr $(,)?) => {
        if cfg!(debug_assertions) {
            // allow non_snake_case to allow capturing const generics
            #[allow(non_snake_case)]
            #[inline(always)]
            fn runtime$(<$($tt)*>)?($($i:$ty),*) {
                if !$e {
                    // don't unwind to reduce impact on code size
                    ::core::panicking::panic_nounwind(
                        concat!("unsafe precondition(s) violated: ", $name)
                    );
                }
            }
            #[allow(non_snake_case)]
            #[inline]
            const fn comptime$(<$($tt)*>)?($(_:$ty),*) {}

            ::core::intrinsics::const_eval_select(($($i,)*), comptime, runtime);
        }
    };
}
pub(crate) use assert_unsafe_precondition;

/// Checks whether `ptr` is properly aligned with respect to
/// `align_of::<T>()`.
#[inline]
pub(crate) fn is_aligned_and_not_null<T>(ptr: *const T) -> bool {
    !ptr.is_null() && ptr.is_aligned()
}

/// Checks whether an allocation of `len` instances of `T` exceeds
/// the maximum allowed allocation size.
#[inline]
pub(crate) fn is_valid_allocation_size<T>(len: usize) -> bool {
    let max_len = const {
        let size = crate::mem::size_of::<T>();
        if size == 0 { usize::MAX } else { isize::MAX as usize / size }
    };
    len <= max_len
}

/// Checks whether the regions of memory starting at `src` and `dst` of size
/// `count * size_of::<T>()` do *not* overlap.
#[inline]
pub(crate) fn is_nonoverlapping<T>(src: *const T, dst: *const T, count: usize) -> bool {
    let src_usize = src.addr();
    let dst_usize = dst.addr();
    let size = mem::size_of::<T>()
        .checked_mul(count)
        .expect("is_nonoverlapping: `size_of::<T>() * count` overflows a usize");
    let diff = src_usize.abs_diff(dst_usize);
    // If the absolute distance between the ptrs is at least as big as the size of the buffer,
    // they do not overlap.
    diff >= size
}

/// Copies `count * size_of::<T>()` bytes from `src` to `dst`. The source
/// and destination must *not* overlap.
///
/// For regions of memory which might overlap, use [`copy`] instead.
///
/// `copy_nonoverlapping` is semantically equivalent to C's [`memcpy`], but
/// with the argument order swapped.
///
/// The copy is "untyped" in the sense that data may be uninitialized or otherwise violate the
/// requirements of `T`. The initialization state is preserved exactly.
///
/// [`memcpy`]: https://en.cppreference.com/w/c/string/byte/memcpy
///
/// # Safety
///
/// Behavior is undefined if any of the following conditions are violated:
///
/// * `src` must be [valid] for reads of `count * size_of::<T>()` bytes.
///
/// * `dst` must be [valid] for writes of `count * size_of::<T>()` bytes.
///
/// * Both `src` and `dst` must be properly aligned.
///
/// * The region of memory beginning at `src` with a size of `count *
///   size_of::<T>()` bytes must *not* overlap with the region of memory
///   beginning at `dst` with the same size.
///
/// Like [`read`], `copy_nonoverlapping` creates a bitwise copy of `T`, regardless of
/// whether `T` is [`Copy`]. If `T` is not [`Copy`], using *both* the values
/// in the region beginning at `*src` and the region beginning at `*dst` can
/// [violate memory safety][read-ownership].
///
/// Note that even if the effectively copied size (`count * size_of::<T>()`) is
/// `0`, the pointers must be non-null and properly aligned.
///
/// [`read`]: crate::ptr::read
/// [read-ownership]: crate::ptr::read#ownership-of-the-returned-value
/// [valid]: crate::ptr#safety
///
/// # Examples
///
/// Manually implement [`Vec::append`]:
///
/// ```
/// use std::ptr;
///
/// /// Moves all the elements of `src` into `dst`, leaving `src` empty.
/// fn append<T>(dst: &mut Vec<T>, src: &mut Vec<T>) {
///     let src_len = src.len();
///     let dst_len = dst.len();
///
///     // Ensure that `dst` has enough capacity to hold all of `src`.
///     dst.reserve(src_len);
///
///     unsafe {
///         // The call to add is always safe because `Vec` will never
///         // allocate more than `isize::MAX` bytes.
///         let dst_ptr = dst.as_mut_ptr().add(dst_len);
///         let src_ptr = src.as_ptr();
///
///         // Truncate `src` without dropping its contents. We do this first,
///         // to avoid problems in case something further down panics.
///         src.set_len(0);
///
///         // The two regions cannot overlap because mutable references do
///         // not alias, and two different vectors cannot own the same
///         // memory.
///         ptr::copy_nonoverlapping(src_ptr, dst_ptr, src_len);
///
///         // Notify `dst` that it now holds the contents of `src`.
///         dst.set_len(dst_len + src_len);
///     }
/// }
///
/// let mut a = vec!['r'];
/// let mut b = vec!['u', 's', 't'];
///
/// append(&mut a, &mut b);
///
/// assert_eq!(a, &['r', 'u', 's', 't']);
/// assert!(b.is_empty());
/// ```
///
/// [`Vec::append`]: ../../std/vec/struct.Vec.html#method.append
#[doc(alias = "memcpy")]
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_allowed_through_unstable_modules]
#[rustc_const_stable(feature = "const_intrinsic_copy", since = "1.63.0")]
#[inline(always)]
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
#[rustc_diagnostic_item = "ptr_copy_nonoverlapping"]
pub const unsafe fn copy_nonoverlapping<T>(src: *const T, dst: *mut T, count: usize) {
    extern "rust-intrinsic" {
        #[rustc_const_stable(feature = "const_intrinsic_copy", since = "1.63.0")]
        #[rustc_nounwind]
        pub fn copy_nonoverlapping<T>(src: *const T, dst: *mut T, count: usize);
    }

    // SAFETY: the safety contract for `copy_nonoverlapping` must be
    // upheld by the caller.
    unsafe {
        assert_unsafe_precondition!(
            "ptr::copy_nonoverlapping requires that both pointer arguments are aligned and non-null \
            and the specified memory ranges do not overlap",
            [T](src: *const T, dst: *mut T, count: usize) =>
            is_aligned_and_not_null(src)
                && is_aligned_and_not_null(dst)
                && is_nonoverlapping(src, dst, count)
        );
        copy_nonoverlapping(src, dst, count)
    }
}

/// Copies `count * size_of::<T>()` bytes from `src` to `dst`. The source
/// and destination may overlap.
///
/// If the source and destination will *never* overlap,
/// [`copy_nonoverlapping`] can be used instead.
///
/// `copy` is semantically equivalent to C's [`memmove`], but with the argument
/// order swapped. Copying takes place as if the bytes were copied from `src`
/// to a temporary array and then copied from the array to `dst`.
///
/// The copy is "untyped" in the sense that data may be uninitialized or otherwise violate the
/// requirements of `T`. The initialization state is preserved exactly.
///
/// [`memmove`]: https://en.cppreference.com/w/c/string/byte/memmove
///
/// # Safety
///
/// Behavior is undefined if any of the following conditions are violated:
///
/// * `src` must be [valid] for reads of `count * size_of::<T>()` bytes, and must remain valid even
///   when `dst` is written for `count * size_of::<T>()` bytes. (This means if the memory ranges
///   overlap, the two pointers must not be subject to aliasing restrictions relative to each
///   other.)
///
/// * `dst` must be [valid] for writes of `count * size_of::<T>()` bytes, and must remain valid even
///   when `src` is read for `count * size_of::<T>()` bytes.
///
/// * Both `src` and `dst` must be properly aligned.
///
/// Like [`read`], `copy` creates a bitwise copy of `T`, regardless of
/// whether `T` is [`Copy`]. If `T` is not [`Copy`], using both the values
/// in the region beginning at `*src` and the region beginning at `*dst` can
/// [violate memory safety][read-ownership].
///
/// Note that even if the effectively copied size (`count * size_of::<T>()`) is
/// `0`, the pointers must be non-null and properly aligned.
///
/// [`read`]: crate::ptr::read
/// [read-ownership]: crate::ptr::read#ownership-of-the-returned-value
/// [valid]: crate::ptr#safety
///
/// # Examples
///
/// Efficiently create a Rust vector from an unsafe buffer:
///
/// ```
/// use std::ptr;
///
/// /// # Safety
/// ///
/// /// * `ptr` must be correctly aligned for its type and non-zero.
/// /// * `ptr` must be valid for reads of `elts` contiguous elements of type `T`.
/// /// * Those elements must not be used after calling this function unless `T: Copy`.
/// # #[allow(dead_code)]
/// unsafe fn from_buf_raw<T>(ptr: *const T, elts: usize) -> Vec<T> {
///     let mut dst = Vec::with_capacity(elts);
///
///     // SAFETY: Our precondition ensures the source is aligned and valid,
///     // and `Vec::with_capacity` ensures that we have usable space to write them.
///     ptr::copy(ptr, dst.as_mut_ptr(), elts);
///
///     // SAFETY: We created it with this much capacity earlier,
///     // and the previous `copy` has initialized these elements.
///     dst.set_len(elts);
///     dst
/// }
/// ```
#[doc(alias = "memmove")]
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_allowed_through_unstable_modules]
#[rustc_const_stable(feature = "const_intrinsic_copy", since = "1.63.0")]
#[inline(always)]
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
#[rustc_diagnostic_item = "ptr_copy"]
pub const unsafe fn copy<T>(src: *const T, dst: *mut T, count: usize) {
    extern "rust-intrinsic" {
        #[rustc_const_stable(feature = "const_intrinsic_copy", since = "1.63.0")]
        #[rustc_nounwind]
        fn copy<T>(src: *const T, dst: *mut T, count: usize);
    }

    // SAFETY: the safety contract for `copy` must be upheld by the caller.
    unsafe {
        assert_unsafe_precondition!(
            "ptr::copy requires that both pointer arguments are aligned and non-null",
            [T](src: *const T, dst: *mut T) =>
            is_aligned_and_not_null(src) && is_aligned_and_not_null(dst)
        );
        copy(src, dst, count)
    }
}

/// Sets `count * size_of::<T>()` bytes of memory starting at `dst` to
/// `val`.
///
/// `write_bytes` is similar to C's [`memset`], but sets `count *
/// size_of::<T>()` bytes to `val`.
///
/// [`memset`]: https://en.cppreference.com/w/c/string/byte/memset
///
/// # Safety
///
/// Behavior is undefined if any of the following conditions are violated:
///
/// * `dst` must be [valid] for writes of `count * size_of::<T>()` bytes.
///
/// * `dst` must be properly aligned.
///
/// Note that even if the effectively copied size (`count * size_of::<T>()`) is
/// `0`, the pointer must be non-null and properly aligned.
///
/// Additionally, note that changing `*dst` in this way can easily lead to undefined behavior (UB)
/// later if the written bytes are not a valid representation of some `T`. For instance, the
/// following is an **incorrect** use of this function:
///
/// ```rust,no_run
/// unsafe {
///     let mut value: u8 = 0;
///     let ptr: *mut bool = &mut value as *mut u8 as *mut bool;
///     let _bool = ptr.read(); // This is fine, `ptr` points to a valid `bool`.
///     ptr.write_bytes(42u8, 1); // This function itself does not cause UB...
///     let _bool = ptr.read(); // ...but it makes this operation UB! ⚠️
/// }
/// ```
///
/// [valid]: crate::ptr#safety
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use std::ptr;
///
/// let mut vec = vec![0u32; 4];
/// unsafe {
///     let vec_ptr = vec.as_mut_ptr();
///     ptr::write_bytes(vec_ptr, 0xfe, 2);
/// }
/// assert_eq!(vec, [0xfefefefe, 0xfefefefe, 0, 0]);
/// ```
#[doc(alias = "memset")]
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_allowed_through_unstable_modules]
#[rustc_const_unstable(feature = "const_ptr_write", issue = "86302")]
#[inline(always)]
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
#[rustc_diagnostic_item = "ptr_write_bytes"]
pub const unsafe fn write_bytes<T>(dst: *mut T, val: u8, count: usize) {
    extern "rust-intrinsic" {
        #[rustc_const_unstable(feature = "const_ptr_write", issue = "86302")]
        #[rustc_nounwind]
        fn write_bytes<T>(dst: *mut T, val: u8, count: usize);
    }

    // SAFETY: the safety contract for `write_bytes` must be upheld by the caller.
    unsafe {
        assert_unsafe_precondition!(
            "ptr::write_bytes requires that the destination pointer is aligned and non-null",
            [T](dst: *mut T) => is_aligned_and_not_null(dst)
        );
        write_bytes(dst, val, count)
    }
}

/// Inform Miri that a given pointer definitely has a certain alignment.
#[cfg(miri)]
pub(crate) const fn miri_promise_symbolic_alignment(ptr: *const (), align: usize) {
    extern "Rust" {
        /// Miri-provided extern function to promise that a given pointer is properly aligned for
        /// "symbolic" alignment checks. Will fail if the pointer is not actually aligned or `align` is
        /// not a power of two. Has no effect when alignment checks are concrete (which is the default).
        fn miri_promise_symbolic_alignment(ptr: *const (), align: usize);
    }

    fn runtime(ptr: *const (), align: usize) {
        // SAFETY: this call is always safe.
        unsafe {
            miri_promise_symbolic_alignment(ptr, align);
        }
    }

    const fn compiletime(_ptr: *const (), _align: usize) {}

    // SAFETY: the extra behavior at runtime is for UB checks only.
    unsafe {
        const_eval_select((ptr, align), compiletime, runtime);
    }
}