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
use std::convert::{TryFrom, TryInto};
use std::fmt;

use either::{Either, Left, Right};

use rustc_apfloat::{
    ieee::{Double, Single},
    Float,
};
use rustc_macros::HashStable;
use rustc_target::abi::{HasDataLayout, Size};

use crate::ty::{ParamEnv, ScalarInt, Ty, TyCtxt};

use super::{
    AllocId, AllocRange, ConstAllocation, InterpResult, Pointer, PointerArithmetic, Provenance,
    ScalarSizeMismatch,
};

/// Represents the result of const evaluation via the `eval_to_allocation` query.
#[derive(Copy, Clone, HashStable, TyEncodable, TyDecodable, Debug, Hash, Eq, PartialEq)]
pub struct ConstAlloc<'tcx> {
    /// The value lives here, at offset 0, and that allocation definitely is an `AllocKind::Memory`
    /// (so you can use `AllocMap::unwrap_memory`).
    pub alloc_id: AllocId,
    pub ty: Ty<'tcx>,
}

/// Represents a constant value in Rust. `Scalar` and `Slice` are optimizations for
/// array length computations, enum discriminants and the pattern matching logic.
#[derive(Copy, Clone, Debug, Eq, PartialEq, TyEncodable, TyDecodable, Hash)]
#[derive(HashStable, Lift)]
pub enum ConstValue<'tcx> {
    /// Used only for types with `layout::abi::Scalar` ABI.
    ///
    /// Not using the enum `Value` to encode that this must not be `Uninit`.
    Scalar(Scalar),

    /// Only used for ZSTs.
    ZeroSized,

    /// Used only for `&[u8]` and `&str`
    Slice { data: ConstAllocation<'tcx>, start: usize, end: usize },

    /// A value not represented/representable by `Scalar` or `Slice`
    ByRef {
        /// The backing memory of the value, may contain more memory than needed for just the value
        /// in order to share `ConstAllocation`s between values
        alloc: ConstAllocation<'tcx>,
        /// Offset into `alloc`
        offset: Size,
    },
}

#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
static_assert_size!(ConstValue<'_>, 32);

impl<'tcx> ConstValue<'tcx> {
    #[inline]
    pub fn try_to_scalar(&self) -> Option<Scalar<AllocId>> {
        match *self {
            ConstValue::ByRef { .. } | ConstValue::Slice { .. } | ConstValue::ZeroSized => None,
            ConstValue::Scalar(val) => Some(val),
        }
    }

    pub fn try_to_scalar_int(&self) -> Option<ScalarInt> {
        self.try_to_scalar()?.try_to_int().ok()
    }

    pub fn try_to_bits(&self, size: Size) -> Option<u128> {
        self.try_to_scalar_int()?.to_bits(size).ok()
    }

    pub fn try_to_bool(&self) -> Option<bool> {
        self.try_to_scalar_int()?.try_into().ok()
    }

    pub fn try_to_machine_usize(&self, tcx: TyCtxt<'tcx>) -> Option<u64> {
        self.try_to_scalar_int()?.try_to_machine_usize(tcx).ok()
    }

    pub fn try_to_bits_for_ty(
        &self,
        tcx: TyCtxt<'tcx>,
        param_env: ParamEnv<'tcx>,
        ty: Ty<'tcx>,
    ) -> Option<u128> {
        let size = tcx.layout_of(param_env.with_reveal_all_normalized(tcx).and(ty)).ok()?.size;
        self.try_to_bits(size)
    }

    pub fn from_bool(b: bool) -> Self {
        ConstValue::Scalar(Scalar::from_bool(b))
    }

    pub fn from_u64(i: u64) -> Self {
        ConstValue::Scalar(Scalar::from_u64(i))
    }

    pub fn from_machine_usize(i: u64, cx: &impl HasDataLayout) -> Self {
        ConstValue::Scalar(Scalar::from_machine_usize(i, cx))
    }
}

/// A `Scalar` represents an immediate, primitive value existing outside of a
/// `memory::Allocation`. It is in many ways like a small chunk of an `Allocation`, up to 16 bytes in
/// size. Like a range of bytes in an `Allocation`, a `Scalar` can either represent the raw bytes
/// of a simple value or a pointer into another `Allocation`
///
/// These variants would be private if there was a convenient way to achieve that in Rust.
/// Do *not* match on a `Scalar`! Use the various `to_*` methods instead.
#[derive(Clone, Copy, Eq, PartialEq, TyEncodable, TyDecodable, Hash)]
#[derive(HashStable)]
pub enum Scalar<Prov = AllocId> {
    /// The raw bytes of a simple value.
    Int(ScalarInt),

    /// A pointer.
    ///
    /// We also store the size of the pointer, such that a `Scalar` always knows how big it is.
    /// The size is always the pointer size of the current target, but this is not information
    /// that we always have readily available.
    Ptr(Pointer<Prov>, u8),
}

#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
static_assert_size!(Scalar, 24);

// We want the `Debug` output to be readable as it is used by `derive(Debug)` for
// all the Miri types.
impl<Prov: Provenance> fmt::Debug for Scalar<Prov> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Scalar::Ptr(ptr, _size) => write!(f, "{:?}", ptr),
            Scalar::Int(int) => write!(f, "{:?}", int),
        }
    }
}

impl<Prov: Provenance> fmt::Display for Scalar<Prov> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Scalar::Ptr(ptr, _size) => write!(f, "pointer to {:?}", ptr),
            Scalar::Int(int) => write!(f, "{}", int),
        }
    }
}

impl<Prov: Provenance> fmt::LowerHex for Scalar<Prov> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Scalar::Ptr(ptr, _size) => write!(f, "pointer to {:?}", ptr),
            Scalar::Int(int) => write!(f, "{:#x}", int),
        }
    }
}

impl<Prov> From<Single> for Scalar<Prov> {
    #[inline(always)]
    fn from(f: Single) -> Self {
        Scalar::from_f32(f)
    }
}

impl<Prov> From<Double> for Scalar<Prov> {
    #[inline(always)]
    fn from(f: Double) -> Self {
        Scalar::from_f64(f)
    }
}

impl<Prov> From<ScalarInt> for Scalar<Prov> {
    #[inline(always)]
    fn from(ptr: ScalarInt) -> Self {
        Scalar::Int(ptr)
    }
}

impl<Prov> Scalar<Prov> {
    #[inline(always)]
    pub fn from_pointer(ptr: Pointer<Prov>, cx: &impl HasDataLayout) -> Self {
        Scalar::Ptr(ptr, u8::try_from(cx.pointer_size().bytes()).unwrap())
    }

    /// Create a Scalar from a pointer with an `Option<_>` provenance (where `None` represents a
    /// plain integer / "invalid" pointer).
    pub fn from_maybe_pointer(ptr: Pointer<Option<Prov>>, cx: &impl HasDataLayout) -> Self {
        match ptr.into_parts() {
            (Some(prov), offset) => Scalar::from_pointer(Pointer::new(prov, offset), cx),
            (None, offset) => {
                Scalar::Int(ScalarInt::try_from_uint(offset.bytes(), cx.pointer_size()).unwrap())
            }
        }
    }

    #[inline]
    pub fn null_ptr(cx: &impl HasDataLayout) -> Self {
        Scalar::Int(ScalarInt::null(cx.pointer_size()))
    }

    #[inline]
    pub fn from_bool(b: bool) -> Self {
        Scalar::Int(b.into())
    }

    #[inline]
    pub fn from_char(c: char) -> Self {
        Scalar::Int(c.into())
    }

    #[inline]
    pub fn try_from_uint(i: impl Into<u128>, size: Size) -> Option<Self> {
        ScalarInt::try_from_uint(i, size).map(Scalar::Int)
    }

    #[inline]
    pub fn from_uint(i: impl Into<u128>, size: Size) -> Self {
        let i = i.into();
        Self::try_from_uint(i, size)
            .unwrap_or_else(|| bug!("Unsigned value {:#x} does not fit in {} bits", i, size.bits()))
    }

    #[inline]
    pub fn from_u8(i: u8) -> Self {
        Scalar::Int(i.into())
    }

    #[inline]
    pub fn from_u16(i: u16) -> Self {
        Scalar::Int(i.into())
    }

    #[inline]
    pub fn from_u32(i: u32) -> Self {
        Scalar::Int(i.into())
    }

    #[inline]
    pub fn from_u64(i: u64) -> Self {
        Scalar::Int(i.into())
    }

    #[inline]
    pub fn from_machine_usize(i: u64, cx: &impl HasDataLayout) -> Self {
        Self::from_uint(i, cx.data_layout().pointer_size)
    }

    #[inline]
    pub fn try_from_int(i: impl Into<i128>, size: Size) -> Option<Self> {
        ScalarInt::try_from_int(i, size).map(Scalar::Int)
    }

    #[inline]
    pub fn from_int(i: impl Into<i128>, size: Size) -> Self {
        let i = i.into();
        Self::try_from_int(i, size)
            .unwrap_or_else(|| bug!("Signed value {:#x} does not fit in {} bits", i, size.bits()))
    }

    #[inline]
    pub fn from_i32(i: i32) -> Self {
        Self::from_int(i, Size::from_bits(32))
    }

    #[inline]
    pub fn from_i64(i: i64) -> Self {
        Self::from_int(i, Size::from_bits(64))
    }

    #[inline]
    pub fn from_machine_isize(i: i64, cx: &impl HasDataLayout) -> Self {
        Self::from_int(i, cx.data_layout().pointer_size)
    }

    #[inline]
    pub fn from_f32(f: Single) -> Self {
        Scalar::Int(f.into())
    }

    #[inline]
    pub fn from_f64(f: Double) -> Self {
        Scalar::Int(f.into())
    }

    /// This is almost certainly not the method you want!  You should dispatch on the type
    /// and use `to_{u8,u16,...}`/`scalar_to_ptr` to perform ptr-to-int / int-to-ptr casts as needed.
    ///
    /// This method only exists for the benefit of low-level operations that truly need to treat the
    /// scalar in whatever form it is.
    ///
    /// This throws UB (instead of ICEing) on a size mismatch since size mismatches can arise in
    /// Miri when someone declares a function that we shim (such as `malloc`) with a wrong type.
    #[inline]
    pub fn to_bits_or_ptr_internal(
        self,
        target_size: Size,
    ) -> Result<Either<u128, Pointer<Prov>>, ScalarSizeMismatch> {
        assert_ne!(target_size.bytes(), 0, "you should never look at the bits of a ZST");
        Ok(match self {
            Scalar::Int(int) => Left(int.to_bits(target_size).map_err(|size| {
                ScalarSizeMismatch { target_size: target_size.bytes(), data_size: size.bytes() }
            })?),
            Scalar::Ptr(ptr, sz) => {
                if target_size.bytes() != u64::from(sz) {
                    return Err(ScalarSizeMismatch {
                        target_size: target_size.bytes(),
                        data_size: sz.into(),
                    });
                }
                Right(ptr)
            }
        })
    }
}

impl<'tcx, Prov: Provenance> Scalar<Prov> {
    pub fn to_pointer(self, cx: &impl HasDataLayout) -> InterpResult<'tcx, Pointer<Option<Prov>>> {
        match self
            .to_bits_or_ptr_internal(cx.pointer_size())
            .map_err(|s| err_ub!(ScalarSizeMismatch(s)))?
        {
            Right(ptr) => Ok(ptr.into()),
            Left(bits) => {
                let addr = u64::try_from(bits).unwrap();
                Ok(Pointer::from_addr(addr))
            }
        }
    }

    /// Fundamental scalar-to-int (cast) operation. Many convenience wrappers exist below, that you
    /// likely want to use instead.
    ///
    /// Will perform ptr-to-int casts if needed and possible.
    /// If that fails, we know the offset is relative, so we return an "erased" Scalar
    /// (which is useful for error messages but not much else).
    #[inline]
    pub fn try_to_int(self) -> Result<ScalarInt, Scalar<AllocId>> {
        match self {
            Scalar::Int(int) => Ok(int),
            Scalar::Ptr(ptr, sz) => {
                if Prov::OFFSET_IS_ADDR {
                    Ok(ScalarInt::try_from_uint(ptr.offset.bytes(), Size::from_bytes(sz)).unwrap())
                } else {
                    // We know `offset` is relative, since `OFFSET_IS_ADDR == false`.
                    let (prov, offset) = ptr.into_parts();
                    // Because `OFFSET_IS_ADDR == false`, this unwrap can never fail.
                    Err(Scalar::Ptr(Pointer::new(prov.get_alloc_id().unwrap(), offset), sz))
                }
            }
        }
    }

    #[inline(always)]
    #[cfg_attr(debug_assertions, track_caller)] // only in debug builds due to perf (see #98980)
    pub fn assert_int(self) -> ScalarInt {
        self.try_to_int().unwrap()
    }

    /// This throws UB (instead of ICEing) on a size mismatch since size mismatches can arise in
    /// Miri when someone declares a function that we shim (such as `malloc`) with a wrong type.
    #[inline]
    pub fn to_bits(self, target_size: Size) -> InterpResult<'tcx, u128> {
        assert_ne!(target_size.bytes(), 0, "you should never look at the bits of a ZST");
        self.try_to_int().map_err(|_| err_unsup!(ReadPointerAsBytes))?.to_bits(target_size).map_err(
            |size| {
                err_ub!(ScalarSizeMismatch(ScalarSizeMismatch {
                    target_size: target_size.bytes(),
                    data_size: size.bytes(),
                }))
                .into()
            },
        )
    }

    #[inline(always)]
    #[cfg_attr(debug_assertions, track_caller)] // only in debug builds due to perf (see #98980)
    pub fn assert_bits(self, target_size: Size) -> u128 {
        self.to_bits(target_size).unwrap()
    }

    pub fn to_bool(self) -> InterpResult<'tcx, bool> {
        let val = self.to_u8()?;
        match val {
            0 => Ok(false),
            1 => Ok(true),
            _ => throw_ub!(InvalidBool(val)),
        }
    }

    pub fn to_char(self) -> InterpResult<'tcx, char> {
        let val = self.to_u32()?;
        match std::char::from_u32(val) {
            Some(c) => Ok(c),
            None => throw_ub!(InvalidChar(val)),
        }
    }

    /// Converts the scalar to produce an unsigned integer of the given size.
    /// Fails if the scalar is a pointer.
    #[inline]
    pub fn to_uint(self, size: Size) -> InterpResult<'tcx, u128> {
        self.to_bits(size)
    }

    /// Converts the scalar to produce a `u8`. Fails if the scalar is a pointer.
    pub fn to_u8(self) -> InterpResult<'tcx, u8> {
        self.to_uint(Size::from_bits(8)).map(|v| u8::try_from(v).unwrap())
    }

    /// Converts the scalar to produce a `u16`. Fails if the scalar is a pointer.
    pub fn to_u16(self) -> InterpResult<'tcx, u16> {
        self.to_uint(Size::from_bits(16)).map(|v| u16::try_from(v).unwrap())
    }

    /// Converts the scalar to produce a `u32`. Fails if the scalar is a pointer.
    pub fn to_u32(self) -> InterpResult<'tcx, u32> {
        self.to_uint(Size::from_bits(32)).map(|v| u32::try_from(v).unwrap())
    }

    /// Converts the scalar to produce a `u64`. Fails if the scalar is a pointer.
    pub fn to_u64(self) -> InterpResult<'tcx, u64> {
        self.to_uint(Size::from_bits(64)).map(|v| u64::try_from(v).unwrap())
    }

    /// Converts the scalar to produce a `u128`. Fails if the scalar is a pointer.
    pub fn to_u128(self) -> InterpResult<'tcx, u128> {
        self.to_uint(Size::from_bits(128))
    }

    /// Converts the scalar to produce a machine-pointer-sized unsigned integer.
    /// Fails if the scalar is a pointer.
    pub fn to_machine_usize(self, cx: &impl HasDataLayout) -> InterpResult<'tcx, u64> {
        let b = self.to_uint(cx.data_layout().pointer_size)?;
        Ok(u64::try_from(b).unwrap())
    }

    /// Converts the scalar to produce a signed integer of the given size.
    /// Fails if the scalar is a pointer.
    #[inline]
    pub fn to_int(self, size: Size) -> InterpResult<'tcx, i128> {
        let b = self.to_bits(size)?;
        Ok(size.sign_extend(b) as i128)
    }

    /// Converts the scalar to produce an `i8`. Fails if the scalar is a pointer.
    pub fn to_i8(self) -> InterpResult<'tcx, i8> {
        self.to_int(Size::from_bits(8)).map(|v| i8::try_from(v).unwrap())
    }

    /// Converts the scalar to produce an `i16`. Fails if the scalar is a pointer.
    pub fn to_i16(self) -> InterpResult<'tcx, i16> {
        self.to_int(Size::from_bits(16)).map(|v| i16::try_from(v).unwrap())
    }

    /// Converts the scalar to produce an `i32`. Fails if the scalar is a pointer.
    pub fn to_i32(self) -> InterpResult<'tcx, i32> {
        self.to_int(Size::from_bits(32)).map(|v| i32::try_from(v).unwrap())
    }

    /// Converts the scalar to produce an `i64`. Fails if the scalar is a pointer.
    pub fn to_i64(self) -> InterpResult<'tcx, i64> {
        self.to_int(Size::from_bits(64)).map(|v| i64::try_from(v).unwrap())
    }

    /// Converts the scalar to produce an `i128`. Fails if the scalar is a pointer.
    pub fn to_i128(self) -> InterpResult<'tcx, i128> {
        self.to_int(Size::from_bits(128))
    }

    /// Converts the scalar to produce a machine-pointer-sized signed integer.
    /// Fails if the scalar is a pointer.
    pub fn to_machine_isize(self, cx: &impl HasDataLayout) -> InterpResult<'tcx, i64> {
        let b = self.to_int(cx.data_layout().pointer_size)?;
        Ok(i64::try_from(b).unwrap())
    }

    #[inline]
    pub fn to_f32(self) -> InterpResult<'tcx, Single> {
        // Going through `u32` to check size and truncation.
        Ok(Single::from_bits(self.to_u32()?.into()))
    }

    #[inline]
    pub fn to_f64(self) -> InterpResult<'tcx, Double> {
        // Going through `u64` to check size and truncation.
        Ok(Double::from_bits(self.to_u64()?.into()))
    }
}

/// Gets the bytes of a constant slice value.
pub fn get_slice_bytes<'tcx>(cx: &impl HasDataLayout, val: ConstValue<'tcx>) -> &'tcx [u8] {
    if let ConstValue::Slice { data, start, end } = val {
        let len = end - start;
        data.inner()
            .get_bytes_strip_provenance(
                cx,
                AllocRange { start: Size::from_bytes(start), size: Size::from_bytes(len) },
            )
            .unwrap_or_else(|err| bug!("const slice is invalid: {:?}", err))
    } else {
        bug!("expected const slice, but found another const value");
    }
}