rustc_codegen_ssa/mir/
block.rs

1use std::cmp;
2
3use rustc_abi::{BackendRepr, ExternAbi, HasDataLayout, Reg, Size, WrappingRange};
4use rustc_ast as ast;
5use rustc_ast::{InlineAsmOptions, InlineAsmTemplatePiece};
6use rustc_data_structures::packed::Pu128;
7use rustc_hir::lang_items::LangItem;
8use rustc_middle::mir::{self, AssertKind, InlineAsmMacro, SwitchTargets, UnwindTerminateReason};
9use rustc_middle::ty::layout::{HasTyCtxt, LayoutOf, ValidityRequirement};
10use rustc_middle::ty::print::{with_no_trimmed_paths, with_no_visible_paths};
11use rustc_middle::ty::{self, Instance, Ty};
12use rustc_middle::{bug, span_bug};
13use rustc_session::config::OptLevel;
14use rustc_span::Span;
15use rustc_span::source_map::Spanned;
16use rustc_target::callconv::{ArgAbi, FnAbi, PassMode};
17use tracing::{debug, info};
18
19use super::operand::OperandRef;
20use super::operand::OperandValue::{Immediate, Pair, Ref, ZeroSized};
21use super::place::{PlaceRef, PlaceValue};
22use super::{CachedLlbb, FunctionCx, LocalRef};
23use crate::base::{self, is_call_from_compiler_builtins_to_upstream_monomorphization};
24use crate::common::{self, IntPredicate};
25use crate::errors::CompilerBuiltinsCannotCall;
26use crate::traits::*;
27use crate::{MemFlags, meth};
28
29// Indicates if we are in the middle of merging a BB's successor into it. This
30// can happen when BB jumps directly to its successor and the successor has no
31// other predecessors.
32#[derive(Debug, PartialEq)]
33enum MergingSucc {
34    False,
35    True,
36}
37
38/// Used by `FunctionCx::codegen_terminator` for emitting common patterns
39/// e.g., creating a basic block, calling a function, etc.
40struct TerminatorCodegenHelper<'tcx> {
41    bb: mir::BasicBlock,
42    terminator: &'tcx mir::Terminator<'tcx>,
43}
44
45impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> {
46    /// Returns the appropriate `Funclet` for the current funclet, if on MSVC,
47    /// either already previously cached, or newly created, by `landing_pad_for`.
48    fn funclet<'b, Bx: BuilderMethods<'a, 'tcx>>(
49        &self,
50        fx: &'b mut FunctionCx<'a, 'tcx, Bx>,
51    ) -> Option<&'b Bx::Funclet> {
52        let cleanup_kinds = fx.cleanup_kinds.as_ref()?;
53        let funclet_bb = cleanup_kinds[self.bb].funclet_bb(self.bb)?;
54        // If `landing_pad_for` hasn't been called yet to create the `Funclet`,
55        // it has to be now. This may not seem necessary, as RPO should lead
56        // to all the unwind edges being visited (and so to `landing_pad_for`
57        // getting called for them), before building any of the blocks inside
58        // the funclet itself - however, if MIR contains edges that end up not
59        // being needed in the LLVM IR after monomorphization, the funclet may
60        // be unreachable, and we don't have yet a way to skip building it in
61        // such an eventuality (which may be a better solution than this).
62        if fx.funclets[funclet_bb].is_none() {
63            fx.landing_pad_for(funclet_bb);
64        }
65        Some(
66            fx.funclets[funclet_bb]
67                .as_ref()
68                .expect("landing_pad_for didn't also create funclets entry"),
69        )
70    }
71
72    /// Get a basic block (creating it if necessary), possibly with cleanup
73    /// stuff in it or next to it.
74    fn llbb_with_cleanup<Bx: BuilderMethods<'a, 'tcx>>(
75        &self,
76        fx: &mut FunctionCx<'a, 'tcx, Bx>,
77        target: mir::BasicBlock,
78    ) -> Bx::BasicBlock {
79        let (needs_landing_pad, is_cleanupret) = self.llbb_characteristics(fx, target);
80        let mut lltarget = fx.llbb(target);
81        if needs_landing_pad {
82            lltarget = fx.landing_pad_for(target);
83        }
84        if is_cleanupret {
85            // Cross-funclet jump - need a trampoline
86            assert!(base::wants_new_eh_instructions(fx.cx.tcx().sess));
87            debug!("llbb_with_cleanup: creating cleanup trampoline for {:?}", target);
88            let name = &format!("{:?}_cleanup_trampoline_{:?}", self.bb, target);
89            let trampoline_llbb = Bx::append_block(fx.cx, fx.llfn, name);
90            let mut trampoline_bx = Bx::build(fx.cx, trampoline_llbb);
91            trampoline_bx.cleanup_ret(self.funclet(fx).unwrap(), Some(lltarget));
92            trampoline_llbb
93        } else {
94            lltarget
95        }
96    }
97
98    fn llbb_characteristics<Bx: BuilderMethods<'a, 'tcx>>(
99        &self,
100        fx: &mut FunctionCx<'a, 'tcx, Bx>,
101        target: mir::BasicBlock,
102    ) -> (bool, bool) {
103        if let Some(ref cleanup_kinds) = fx.cleanup_kinds {
104            let funclet_bb = cleanup_kinds[self.bb].funclet_bb(self.bb);
105            let target_funclet = cleanup_kinds[target].funclet_bb(target);
106            let (needs_landing_pad, is_cleanupret) = match (funclet_bb, target_funclet) {
107                (None, None) => (false, false),
108                (None, Some(_)) => (true, false),
109                (Some(f), Some(t_f)) => (f != t_f, f != t_f),
110                (Some(_), None) => {
111                    let span = self.terminator.source_info.span;
112                    span_bug!(span, "{:?} - jump out of cleanup?", self.terminator);
113                }
114            };
115            (needs_landing_pad, is_cleanupret)
116        } else {
117            let needs_landing_pad = !fx.mir[self.bb].is_cleanup && fx.mir[target].is_cleanup;
118            let is_cleanupret = false;
119            (needs_landing_pad, is_cleanupret)
120        }
121    }
122
123    fn funclet_br<Bx: BuilderMethods<'a, 'tcx>>(
124        &self,
125        fx: &mut FunctionCx<'a, 'tcx, Bx>,
126        bx: &mut Bx,
127        target: mir::BasicBlock,
128        mergeable_succ: bool,
129    ) -> MergingSucc {
130        let (needs_landing_pad, is_cleanupret) = self.llbb_characteristics(fx, target);
131        if mergeable_succ && !needs_landing_pad && !is_cleanupret {
132            // We can merge the successor into this bb, so no need for a `br`.
133            MergingSucc::True
134        } else {
135            let mut lltarget = fx.llbb(target);
136            if needs_landing_pad {
137                lltarget = fx.landing_pad_for(target);
138            }
139            if is_cleanupret {
140                // micro-optimization: generate a `ret` rather than a jump
141                // to a trampoline.
142                bx.cleanup_ret(self.funclet(fx).unwrap(), Some(lltarget));
143            } else {
144                bx.br(lltarget);
145            }
146            MergingSucc::False
147        }
148    }
149
150    /// Call `fn_ptr` of `fn_abi` with the arguments `llargs`, the optional
151    /// return destination `destination` and the unwind action `unwind`.
152    fn do_call<Bx: BuilderMethods<'a, 'tcx>>(
153        &self,
154        fx: &mut FunctionCx<'a, 'tcx, Bx>,
155        bx: &mut Bx,
156        fn_abi: &'tcx FnAbi<'tcx, Ty<'tcx>>,
157        fn_ptr: Bx::Value,
158        llargs: &[Bx::Value],
159        destination: Option<(ReturnDest<'tcx, Bx::Value>, mir::BasicBlock)>,
160        mut unwind: mir::UnwindAction,
161        lifetime_ends_after_call: &[(Bx::Value, Size)],
162        instance: Option<Instance<'tcx>>,
163        mergeable_succ: bool,
164    ) -> MergingSucc {
165        let tcx = bx.tcx();
166        if let Some(instance) = instance
167            && is_call_from_compiler_builtins_to_upstream_monomorphization(tcx, instance)
168        {
169            if destination.is_some() {
170                let caller_def = fx.instance.def_id();
171                let e = CompilerBuiltinsCannotCall {
172                    span: tcx.def_span(caller_def),
173                    caller: with_no_trimmed_paths!(tcx.def_path_str(caller_def)),
174                    callee: with_no_trimmed_paths!(tcx.def_path_str(instance.def_id())),
175                };
176                tcx.dcx().emit_err(e);
177            } else {
178                info!(
179                    "compiler_builtins call to diverging function {:?} replaced with abort",
180                    instance.def_id()
181                );
182                bx.abort();
183                bx.unreachable();
184                return MergingSucc::False;
185            }
186        }
187
188        // If there is a cleanup block and the function we're calling can unwind, then
189        // do an invoke, otherwise do a call.
190        let fn_ty = bx.fn_decl_backend_type(fn_abi);
191
192        let fn_attrs = if bx.tcx().def_kind(fx.instance.def_id()).has_codegen_attrs() {
193            Some(bx.tcx().codegen_fn_attrs(fx.instance.def_id()))
194        } else {
195            None
196        };
197
198        if !fn_abi.can_unwind {
199            unwind = mir::UnwindAction::Unreachable;
200        }
201
202        let unwind_block = match unwind {
203            mir::UnwindAction::Cleanup(cleanup) => Some(self.llbb_with_cleanup(fx, cleanup)),
204            mir::UnwindAction::Continue => None,
205            mir::UnwindAction::Unreachable => None,
206            mir::UnwindAction::Terminate(reason) => {
207                if fx.mir[self.bb].is_cleanup && base::wants_new_eh_instructions(fx.cx.tcx().sess) {
208                    // MSVC SEH will abort automatically if an exception tries to
209                    // propagate out from cleanup.
210
211                    // FIXME(@mirkootter): For wasm, we currently do not support terminate during
212                    // cleanup, because this requires a few more changes: The current code
213                    // caches the `terminate_block` for each function; funclet based code - however -
214                    // requires a different terminate_block for each funclet
215                    // Until this is implemented, we just do not unwind inside cleanup blocks
216
217                    None
218                } else {
219                    Some(fx.terminate_block(reason))
220                }
221            }
222        };
223
224        if let Some(unwind_block) = unwind_block {
225            let ret_llbb = if let Some((_, target)) = destination {
226                fx.llbb(target)
227            } else {
228                fx.unreachable_block()
229            };
230            let invokeret = bx.invoke(
231                fn_ty,
232                fn_attrs,
233                Some(fn_abi),
234                fn_ptr,
235                llargs,
236                ret_llbb,
237                unwind_block,
238                self.funclet(fx),
239                instance,
240            );
241            if fx.mir[self.bb].is_cleanup {
242                bx.apply_attrs_to_cleanup_callsite(invokeret);
243            }
244
245            if let Some((ret_dest, target)) = destination {
246                bx.switch_to_block(fx.llbb(target));
247                fx.set_debug_loc(bx, self.terminator.source_info);
248                for &(tmp, size) in lifetime_ends_after_call {
249                    bx.lifetime_end(tmp, size);
250                }
251                fx.store_return(bx, ret_dest, &fn_abi.ret, invokeret);
252            }
253            MergingSucc::False
254        } else {
255            let llret =
256                bx.call(fn_ty, fn_attrs, Some(fn_abi), fn_ptr, llargs, self.funclet(fx), instance);
257            if fx.mir[self.bb].is_cleanup {
258                bx.apply_attrs_to_cleanup_callsite(llret);
259            }
260
261            if let Some((ret_dest, target)) = destination {
262                for &(tmp, size) in lifetime_ends_after_call {
263                    bx.lifetime_end(tmp, size);
264                }
265                fx.store_return(bx, ret_dest, &fn_abi.ret, llret);
266                self.funclet_br(fx, bx, target, mergeable_succ)
267            } else {
268                bx.unreachable();
269                MergingSucc::False
270            }
271        }
272    }
273
274    /// Generates inline assembly with optional `destination` and `unwind`.
275    fn do_inlineasm<Bx: BuilderMethods<'a, 'tcx>>(
276        &self,
277        fx: &mut FunctionCx<'a, 'tcx, Bx>,
278        bx: &mut Bx,
279        template: &[InlineAsmTemplatePiece],
280        operands: &[InlineAsmOperandRef<'tcx, Bx>],
281        options: InlineAsmOptions,
282        line_spans: &[Span],
283        destination: Option<mir::BasicBlock>,
284        unwind: mir::UnwindAction,
285        instance: Instance<'_>,
286        mergeable_succ: bool,
287    ) -> MergingSucc {
288        let unwind_target = match unwind {
289            mir::UnwindAction::Cleanup(cleanup) => Some(self.llbb_with_cleanup(fx, cleanup)),
290            mir::UnwindAction::Terminate(reason) => Some(fx.terminate_block(reason)),
291            mir::UnwindAction::Continue => None,
292            mir::UnwindAction::Unreachable => None,
293        };
294
295        if operands.iter().any(|x| matches!(x, InlineAsmOperandRef::Label { .. })) {
296            assert!(unwind_target.is_none());
297            let ret_llbb = if let Some(target) = destination {
298                fx.llbb(target)
299            } else {
300                fx.unreachable_block()
301            };
302
303            bx.codegen_inline_asm(
304                template,
305                operands,
306                options,
307                line_spans,
308                instance,
309                Some(ret_llbb),
310                None,
311            );
312            MergingSucc::False
313        } else if let Some(cleanup) = unwind_target {
314            let ret_llbb = if let Some(target) = destination {
315                fx.llbb(target)
316            } else {
317                fx.unreachable_block()
318            };
319
320            bx.codegen_inline_asm(
321                template,
322                operands,
323                options,
324                line_spans,
325                instance,
326                Some(ret_llbb),
327                Some((cleanup, self.funclet(fx))),
328            );
329            MergingSucc::False
330        } else {
331            bx.codegen_inline_asm(template, operands, options, line_spans, instance, None, None);
332
333            if let Some(target) = destination {
334                self.funclet_br(fx, bx, target, mergeable_succ)
335            } else {
336                bx.unreachable();
337                MergingSucc::False
338            }
339        }
340    }
341}
342
343/// Codegen implementations for some terminator variants.
344impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
345    /// Generates code for a `Resume` terminator.
346    fn codegen_resume_terminator(&mut self, helper: TerminatorCodegenHelper<'tcx>, bx: &mut Bx) {
347        if let Some(funclet) = helper.funclet(self) {
348            bx.cleanup_ret(funclet, None);
349        } else {
350            let slot = self.get_personality_slot(bx);
351            let exn0 = slot.project_field(bx, 0);
352            let exn0 = bx.load_operand(exn0).immediate();
353            let exn1 = slot.project_field(bx, 1);
354            let exn1 = bx.load_operand(exn1).immediate();
355            slot.storage_dead(bx);
356
357            bx.resume(exn0, exn1);
358        }
359    }
360
361    fn codegen_switchint_terminator(
362        &mut self,
363        helper: TerminatorCodegenHelper<'tcx>,
364        bx: &mut Bx,
365        discr: &mir::Operand<'tcx>,
366        targets: &SwitchTargets,
367    ) {
368        let discr = self.codegen_operand(bx, discr);
369        let discr_value = discr.immediate();
370        let switch_ty = discr.layout.ty;
371        // If our discriminant is a constant we can branch directly
372        if let Some(const_discr) = bx.const_to_opt_u128(discr_value, false) {
373            let target = targets.target_for_value(const_discr);
374            bx.br(helper.llbb_with_cleanup(self, target));
375            return;
376        };
377
378        let mut target_iter = targets.iter();
379        if target_iter.len() == 1 {
380            // If there are two targets (one conditional, one fallback), emit `br` instead of
381            // `switch`.
382            let (test_value, target) = target_iter.next().unwrap();
383            let otherwise = targets.otherwise();
384            let lltarget = helper.llbb_with_cleanup(self, target);
385            let llotherwise = helper.llbb_with_cleanup(self, otherwise);
386            let target_cold = self.cold_blocks[target];
387            let otherwise_cold = self.cold_blocks[otherwise];
388            // If `target_cold == otherwise_cold`, the branches have the same weight
389            // so there is no expectation. If they differ, the `target` branch is expected
390            // when the `otherwise` branch is cold.
391            let expect = if target_cold == otherwise_cold { None } else { Some(otherwise_cold) };
392            if switch_ty == bx.tcx().types.bool {
393                // Don't generate trivial icmps when switching on bool.
394                match test_value {
395                    0 => {
396                        let expect = expect.map(|e| !e);
397                        bx.cond_br_with_expect(discr_value, llotherwise, lltarget, expect);
398                    }
399                    1 => {
400                        bx.cond_br_with_expect(discr_value, lltarget, llotherwise, expect);
401                    }
402                    _ => bug!(),
403                }
404            } else {
405                let switch_llty = bx.immediate_backend_type(bx.layout_of(switch_ty));
406                let llval = bx.const_uint_big(switch_llty, test_value);
407                let cmp = bx.icmp(IntPredicate::IntEQ, discr_value, llval);
408                bx.cond_br_with_expect(cmp, lltarget, llotherwise, expect);
409            }
410        } else if target_iter.len() == 2
411            && self.mir[targets.otherwise()].is_empty_unreachable()
412            && targets.all_values().contains(&Pu128(0))
413            && targets.all_values().contains(&Pu128(1))
414        {
415            // This is the really common case for `bool`, `Option`, etc.
416            // By using `trunc nuw` we communicate that other values are
417            // impossible without needing `switch` or `assume`s.
418            let true_bb = targets.target_for_value(1);
419            let false_bb = targets.target_for_value(0);
420            let true_ll = helper.llbb_with_cleanup(self, true_bb);
421            let false_ll = helper.llbb_with_cleanup(self, false_bb);
422
423            let expected_cond_value = if self.cx.sess().opts.optimize == OptLevel::No {
424                None
425            } else {
426                match (self.cold_blocks[true_bb], self.cold_blocks[false_bb]) {
427                    // Same coldness, no expectation
428                    (true, true) | (false, false) => None,
429                    // Different coldness, expect the non-cold one
430                    (true, false) => Some(false),
431                    (false, true) => Some(true),
432                }
433            };
434
435            let bool_ty = bx.tcx().types.bool;
436            let cond = if switch_ty == bool_ty {
437                discr_value
438            } else {
439                let bool_llty = bx.immediate_backend_type(bx.layout_of(bool_ty));
440                bx.unchecked_utrunc(discr_value, bool_llty)
441            };
442            bx.cond_br_with_expect(cond, true_ll, false_ll, expected_cond_value);
443        } else if self.cx.sess().opts.optimize == OptLevel::No
444            && target_iter.len() == 2
445            && self.mir[targets.otherwise()].is_empty_unreachable()
446        {
447            // In unoptimized builds, if there are two normal targets and the `otherwise` target is
448            // an unreachable BB, emit `br` instead of `switch`. This leaves behind the unreachable
449            // BB, which will usually (but not always) be dead code.
450            //
451            // Why only in unoptimized builds?
452            // - In unoptimized builds LLVM uses FastISel which does not support switches, so it
453            //   must fall back to the slower SelectionDAG isel. Therefore, using `br` gives
454            //   significant compile time speedups for unoptimized builds.
455            // - In optimized builds the above doesn't hold, and using `br` sometimes results in
456            //   worse generated code because LLVM can no longer tell that the value being switched
457            //   on can only have two values, e.g. 0 and 1.
458            //
459            let (test_value1, target1) = target_iter.next().unwrap();
460            let (_test_value2, target2) = target_iter.next().unwrap();
461            let ll1 = helper.llbb_with_cleanup(self, target1);
462            let ll2 = helper.llbb_with_cleanup(self, target2);
463            let switch_llty = bx.immediate_backend_type(bx.layout_of(switch_ty));
464            let llval = bx.const_uint_big(switch_llty, test_value1);
465            let cmp = bx.icmp(IntPredicate::IntEQ, discr_value, llval);
466            bx.cond_br(cmp, ll1, ll2);
467        } else {
468            let otherwise = targets.otherwise();
469            let otherwise_cold = self.cold_blocks[otherwise];
470            let otherwise_unreachable = self.mir[otherwise].is_empty_unreachable();
471            let cold_count = targets.iter().filter(|(_, target)| self.cold_blocks[*target]).count();
472            let none_cold = cold_count == 0;
473            let all_cold = cold_count == targets.iter().len();
474            if (none_cold && (!otherwise_cold || otherwise_unreachable))
475                || (all_cold && (otherwise_cold || otherwise_unreachable))
476            {
477                // All targets have the same weight,
478                // or `otherwise` is unreachable and it's the only target with a different weight.
479                bx.switch(
480                    discr_value,
481                    helper.llbb_with_cleanup(self, targets.otherwise()),
482                    target_iter
483                        .map(|(value, target)| (value, helper.llbb_with_cleanup(self, target))),
484                );
485            } else {
486                // Targets have different weights
487                bx.switch_with_weights(
488                    discr_value,
489                    helper.llbb_with_cleanup(self, targets.otherwise()),
490                    otherwise_cold,
491                    target_iter.map(|(value, target)| {
492                        (value, helper.llbb_with_cleanup(self, target), self.cold_blocks[target])
493                    }),
494                );
495            }
496        }
497    }
498
499    fn codegen_return_terminator(&mut self, bx: &mut Bx) {
500        // Call `va_end` if this is the definition of a C-variadic function.
501        if self.fn_abi.c_variadic {
502            // The `VaList` "spoofed" argument is just after all the real arguments.
503            let va_list_arg_idx = self.fn_abi.args.len();
504            match self.locals[mir::Local::from_usize(1 + va_list_arg_idx)] {
505                LocalRef::Place(va_list) => {
506                    bx.va_end(va_list.val.llval);
507                }
508                _ => bug!("C-variadic function must have a `VaList` place"),
509            }
510        }
511        if self.fn_abi.ret.layout.is_uninhabited() {
512            // Functions with uninhabited return values are marked `noreturn`,
513            // so we should make sure that we never actually do.
514            // We play it safe by using a well-defined `abort`, but we could go for immediate UB
515            // if that turns out to be helpful.
516            bx.abort();
517            // `abort` does not terminate the block, so we still need to generate
518            // an `unreachable` terminator after it.
519            bx.unreachable();
520            return;
521        }
522        let llval = match &self.fn_abi.ret.mode {
523            PassMode::Ignore | PassMode::Indirect { .. } => {
524                bx.ret_void();
525                return;
526            }
527
528            PassMode::Direct(_) | PassMode::Pair(..) => {
529                let op = self.codegen_consume(bx, mir::Place::return_place().as_ref());
530                if let Ref(place_val) = op.val {
531                    bx.load_from_place(bx.backend_type(op.layout), place_val)
532                } else {
533                    op.immediate_or_packed_pair(bx)
534                }
535            }
536
537            PassMode::Cast { cast: cast_ty, pad_i32: _ } => {
538                let op = match self.locals[mir::RETURN_PLACE] {
539                    LocalRef::Operand(op) => op,
540                    LocalRef::PendingOperand => bug!("use of return before def"),
541                    LocalRef::Place(cg_place) => {
542                        OperandRef { val: Ref(cg_place.val), layout: cg_place.layout }
543                    }
544                    LocalRef::UnsizedPlace(_) => bug!("return type must be sized"),
545                };
546                let llslot = match op.val {
547                    Immediate(_) | Pair(..) => {
548                        let scratch = PlaceRef::alloca(bx, self.fn_abi.ret.layout);
549                        op.val.store(bx, scratch);
550                        scratch.val.llval
551                    }
552                    Ref(place_val) => {
553                        assert_eq!(
554                            place_val.align, op.layout.align.abi,
555                            "return place is unaligned!"
556                        );
557                        place_val.llval
558                    }
559                    ZeroSized => bug!("ZST return value shouldn't be in PassMode::Cast"),
560                };
561                let ty = bx.cast_backend_type(cast_ty);
562                bx.load(ty, llslot, self.fn_abi.ret.layout.align.abi)
563            }
564        };
565        bx.ret(llval);
566    }
567
568    #[tracing::instrument(level = "trace", skip(self, helper, bx))]
569    fn codegen_drop_terminator(
570        &mut self,
571        helper: TerminatorCodegenHelper<'tcx>,
572        bx: &mut Bx,
573        source_info: &mir::SourceInfo,
574        location: mir::Place<'tcx>,
575        target: mir::BasicBlock,
576        unwind: mir::UnwindAction,
577        mergeable_succ: bool,
578    ) -> MergingSucc {
579        let ty = location.ty(self.mir, bx.tcx()).ty;
580        let ty = self.monomorphize(ty);
581        let drop_fn = Instance::resolve_drop_in_place(bx.tcx(), ty);
582
583        if let ty::InstanceKind::DropGlue(_, None) = drop_fn.def {
584            // we don't actually need to drop anything.
585            return helper.funclet_br(self, bx, target, mergeable_succ);
586        }
587
588        let place = self.codegen_place(bx, location.as_ref());
589        let (args1, args2);
590        let mut args = if let Some(llextra) = place.val.llextra {
591            args2 = [place.val.llval, llextra];
592            &args2[..]
593        } else {
594            args1 = [place.val.llval];
595            &args1[..]
596        };
597        let (maybe_null, drop_fn, fn_abi, drop_instance) = match ty.kind() {
598            // FIXME(eddyb) perhaps move some of this logic into
599            // `Instance::resolve_drop_in_place`?
600            ty::Dynamic(_, _, ty::Dyn) => {
601                // IN THIS ARM, WE HAVE:
602                // ty = *mut (dyn Trait)
603                // which is: exists<T> ( *mut T,    Vtable<T: Trait> )
604                //                       args[0]    args[1]
605                //
606                // args = ( Data, Vtable )
607                //                  |
608                //                  v
609                //                /-------\
610                //                | ...   |
611                //                \-------/
612                //
613                let virtual_drop = Instance {
614                    def: ty::InstanceKind::Virtual(drop_fn.def_id(), 0), // idx 0: the drop function
615                    args: drop_fn.args,
616                };
617                debug!("ty = {:?}", ty);
618                debug!("drop_fn = {:?}", drop_fn);
619                debug!("args = {:?}", args);
620                let fn_abi = bx.fn_abi_of_instance(virtual_drop, ty::List::empty());
621                let vtable = args[1];
622                // Truncate vtable off of args list
623                args = &args[..1];
624                (
625                    true,
626                    meth::VirtualIndex::from_index(ty::COMMON_VTABLE_ENTRIES_DROPINPLACE)
627                        .get_optional_fn(bx, vtable, ty, fn_abi),
628                    fn_abi,
629                    virtual_drop,
630                )
631            }
632            ty::Dynamic(_, _, ty::DynStar) => {
633                // IN THIS ARM, WE HAVE:
634                // ty = *mut (dyn* Trait)
635                // which is: *mut exists<T: sizeof(T) == sizeof(usize)> (T, Vtable<T: Trait>)
636                //
637                // args = [ * ]
638                //          |
639                //          v
640                //      ( Data, Vtable )
641                //                |
642                //                v
643                //              /-------\
644                //              | ...   |
645                //              \-------/
646                //
647                //
648                // WE CAN CONVERT THIS INTO THE ABOVE LOGIC BY DOING
649                //
650                // data = &(*args[0]).0    // gives a pointer to Data above (really the same pointer)
651                // vtable = (*args[0]).1   // loads the vtable out
652                // (data, vtable)          // an equivalent Rust `*mut dyn Trait`
653                //
654                // SO THEN WE CAN USE THE ABOVE CODE.
655                let virtual_drop = Instance {
656                    def: ty::InstanceKind::Virtual(drop_fn.def_id(), 0), // idx 0: the drop function
657                    args: drop_fn.args,
658                };
659                debug!("ty = {:?}", ty);
660                debug!("drop_fn = {:?}", drop_fn);
661                debug!("args = {:?}", args);
662                let fn_abi = bx.fn_abi_of_instance(virtual_drop, ty::List::empty());
663                let meta_ptr = place.project_field(bx, 1);
664                let meta = bx.load_operand(meta_ptr);
665                // Truncate vtable off of args list
666                args = &args[..1];
667                debug!("args' = {:?}", args);
668                (
669                    true,
670                    meth::VirtualIndex::from_index(ty::COMMON_VTABLE_ENTRIES_DROPINPLACE)
671                        .get_optional_fn(bx, meta.immediate(), ty, fn_abi),
672                    fn_abi,
673                    virtual_drop,
674                )
675            }
676            _ => (
677                false,
678                bx.get_fn_addr(drop_fn),
679                bx.fn_abi_of_instance(drop_fn, ty::List::empty()),
680                drop_fn,
681            ),
682        };
683
684        // We generate a null check for the drop_fn. This saves a bunch of relocations being
685        // generated for no-op drops.
686        if maybe_null {
687            let is_not_null = bx.append_sibling_block("is_not_null");
688            let llty = bx.fn_ptr_backend_type(fn_abi);
689            let null = bx.const_null(llty);
690            let non_null =
691                bx.icmp(base::bin_op_to_icmp_predicate(mir::BinOp::Ne, false), drop_fn, null);
692            bx.cond_br(non_null, is_not_null, helper.llbb_with_cleanup(self, target));
693            bx.switch_to_block(is_not_null);
694            self.set_debug_loc(bx, *source_info);
695        }
696
697        helper.do_call(
698            self,
699            bx,
700            fn_abi,
701            drop_fn,
702            args,
703            Some((ReturnDest::Nothing, target)),
704            unwind,
705            &[],
706            Some(drop_instance),
707            !maybe_null && mergeable_succ,
708        )
709    }
710
711    fn codegen_assert_terminator(
712        &mut self,
713        helper: TerminatorCodegenHelper<'tcx>,
714        bx: &mut Bx,
715        terminator: &mir::Terminator<'tcx>,
716        cond: &mir::Operand<'tcx>,
717        expected: bool,
718        msg: &mir::AssertMessage<'tcx>,
719        target: mir::BasicBlock,
720        unwind: mir::UnwindAction,
721        mergeable_succ: bool,
722    ) -> MergingSucc {
723        let span = terminator.source_info.span;
724        let cond = self.codegen_operand(bx, cond).immediate();
725        let mut const_cond = bx.const_to_opt_u128(cond, false).map(|c| c == 1);
726
727        // This case can currently arise only from functions marked
728        // with #[rustc_inherit_overflow_checks] and inlined from
729        // another crate (mostly core::num generic/#[inline] fns),
730        // while the current crate doesn't use overflow checks.
731        if !bx.sess().overflow_checks() && msg.is_optional_overflow_check() {
732            const_cond = Some(expected);
733        }
734
735        // Don't codegen the panic block if success if known.
736        if const_cond == Some(expected) {
737            return helper.funclet_br(self, bx, target, mergeable_succ);
738        }
739
740        // Because we're branching to a panic block (either a `#[cold]` one
741        // or an inlined abort), there's no need to `expect` it.
742
743        // Create the failure block and the conditional branch to it.
744        let lltarget = helper.llbb_with_cleanup(self, target);
745        let panic_block = bx.append_sibling_block("panic");
746        if expected {
747            bx.cond_br(cond, lltarget, panic_block);
748        } else {
749            bx.cond_br(cond, panic_block, lltarget);
750        }
751
752        // After this point, bx is the block for the call to panic.
753        bx.switch_to_block(panic_block);
754        self.set_debug_loc(bx, terminator.source_info);
755
756        // Get the location information.
757        let location = self.get_caller_location(bx, terminator.source_info).immediate();
758
759        // Put together the arguments to the panic entry point.
760        let (lang_item, args) = match msg {
761            AssertKind::BoundsCheck { len, index } => {
762                let len = self.codegen_operand(bx, len).immediate();
763                let index = self.codegen_operand(bx, index).immediate();
764                // It's `fn panic_bounds_check(index: usize, len: usize)`,
765                // and `#[track_caller]` adds an implicit third argument.
766                (LangItem::PanicBoundsCheck, vec![index, len, location])
767            }
768            AssertKind::MisalignedPointerDereference { required, found } => {
769                let required = self.codegen_operand(bx, required).immediate();
770                let found = self.codegen_operand(bx, found).immediate();
771                // It's `fn panic_misaligned_pointer_dereference(required: usize, found: usize)`,
772                // and `#[track_caller]` adds an implicit third argument.
773                (LangItem::PanicMisalignedPointerDereference, vec![required, found, location])
774            }
775            AssertKind::NullPointerDereference => {
776                // It's `fn panic_null_pointer_dereference()`,
777                // `#[track_caller]` adds an implicit argument.
778                (LangItem::PanicNullPointerDereference, vec![location])
779            }
780            _ => {
781                // It's `pub fn panic_...()` and `#[track_caller]` adds an implicit argument.
782                (msg.panic_function(), vec![location])
783            }
784        };
785
786        let (fn_abi, llfn, instance) = common::build_langcall(bx, span, lang_item);
787
788        // Codegen the actual panic invoke/call.
789        let merging_succ =
790            helper.do_call(self, bx, fn_abi, llfn, &args, None, unwind, &[], Some(instance), false);
791        assert_eq!(merging_succ, MergingSucc::False);
792        MergingSucc::False
793    }
794
795    fn codegen_terminate_terminator(
796        &mut self,
797        helper: TerminatorCodegenHelper<'tcx>,
798        bx: &mut Bx,
799        terminator: &mir::Terminator<'tcx>,
800        reason: UnwindTerminateReason,
801    ) {
802        let span = terminator.source_info.span;
803        self.set_debug_loc(bx, terminator.source_info);
804
805        // Obtain the panic entry point.
806        let (fn_abi, llfn, instance) = common::build_langcall(bx, span, reason.lang_item());
807
808        // Codegen the actual panic invoke/call.
809        let merging_succ = helper.do_call(
810            self,
811            bx,
812            fn_abi,
813            llfn,
814            &[],
815            None,
816            mir::UnwindAction::Unreachable,
817            &[],
818            Some(instance),
819            false,
820        );
821        assert_eq!(merging_succ, MergingSucc::False);
822    }
823
824    /// Returns `Some` if this is indeed a panic intrinsic and codegen is done.
825    fn codegen_panic_intrinsic(
826        &mut self,
827        helper: &TerminatorCodegenHelper<'tcx>,
828        bx: &mut Bx,
829        intrinsic: ty::IntrinsicDef,
830        instance: Instance<'tcx>,
831        source_info: mir::SourceInfo,
832        target: Option<mir::BasicBlock>,
833        unwind: mir::UnwindAction,
834        mergeable_succ: bool,
835    ) -> Option<MergingSucc> {
836        // Emit a panic or a no-op for `assert_*` intrinsics.
837        // These are intrinsics that compile to panics so that we can get a message
838        // which mentions the offending type, even from a const context.
839        let Some(requirement) = ValidityRequirement::from_intrinsic(intrinsic.name) else {
840            return None;
841        };
842
843        let ty = instance.args.type_at(0);
844
845        let is_valid = bx
846            .tcx()
847            .check_validity_requirement((requirement, bx.typing_env().as_query_input(ty)))
848            .expect("expect to have layout during codegen");
849
850        if is_valid {
851            // a NOP
852            let target = target.unwrap();
853            return Some(helper.funclet_br(self, bx, target, mergeable_succ));
854        }
855
856        let layout = bx.layout_of(ty);
857
858        let msg_str = with_no_visible_paths!({
859            with_no_trimmed_paths!({
860                if layout.is_uninhabited() {
861                    // Use this error even for the other intrinsics as it is more precise.
862                    format!("attempted to instantiate uninhabited type `{ty}`")
863                } else if requirement == ValidityRequirement::Zero {
864                    format!("attempted to zero-initialize type `{ty}`, which is invalid")
865                } else {
866                    format!("attempted to leave type `{ty}` uninitialized, which is invalid")
867                }
868            })
869        });
870        let msg = bx.const_str(&msg_str);
871
872        // Obtain the panic entry point.
873        let (fn_abi, llfn, instance) =
874            common::build_langcall(bx, source_info.span, LangItem::PanicNounwind);
875
876        // Codegen the actual panic invoke/call.
877        Some(helper.do_call(
878            self,
879            bx,
880            fn_abi,
881            llfn,
882            &[msg.0, msg.1],
883            target.as_ref().map(|bb| (ReturnDest::Nothing, *bb)),
884            unwind,
885            &[],
886            Some(instance),
887            mergeable_succ,
888        ))
889    }
890
891    fn codegen_call_terminator(
892        &mut self,
893        helper: TerminatorCodegenHelper<'tcx>,
894        bx: &mut Bx,
895        terminator: &mir::Terminator<'tcx>,
896        func: &mir::Operand<'tcx>,
897        args: &[Spanned<mir::Operand<'tcx>>],
898        destination: mir::Place<'tcx>,
899        target: Option<mir::BasicBlock>,
900        unwind: mir::UnwindAction,
901        fn_span: Span,
902        mergeable_succ: bool,
903    ) -> MergingSucc {
904        let source_info = mir::SourceInfo { span: fn_span, ..terminator.source_info };
905
906        // Create the callee. This is a fn ptr or zero-sized and hence a kind of scalar.
907        let callee = self.codegen_operand(bx, func);
908
909        let (instance, mut llfn) = match *callee.layout.ty.kind() {
910            ty::FnDef(def_id, generic_args) => {
911                let instance = ty::Instance::expect_resolve(
912                    bx.tcx(),
913                    bx.typing_env(),
914                    def_id,
915                    generic_args,
916                    fn_span,
917                );
918
919                let instance = match instance.def {
920                    // We don't need AsyncDropGlueCtorShim here because it is not `noop func`,
921                    // it is `func returning noop future`
922                    ty::InstanceKind::DropGlue(_, None) => {
923                        // Empty drop glue; a no-op.
924                        let target = target.unwrap();
925                        return helper.funclet_br(self, bx, target, mergeable_succ);
926                    }
927                    ty::InstanceKind::Intrinsic(def_id) => {
928                        let intrinsic = bx.tcx().intrinsic(def_id).unwrap();
929                        if let Some(merging_succ) = self.codegen_panic_intrinsic(
930                            &helper,
931                            bx,
932                            intrinsic,
933                            instance,
934                            source_info,
935                            target,
936                            unwind,
937                            mergeable_succ,
938                        ) {
939                            return merging_succ;
940                        }
941
942                        let result_layout =
943                            self.cx.layout_of(self.monomorphized_place_ty(destination.as_ref()));
944
945                        let (result, store_in_local) = if result_layout.is_zst() {
946                            (
947                                PlaceRef::new_sized(bx.const_undef(bx.type_ptr()), result_layout),
948                                None,
949                            )
950                        } else if let Some(local) = destination.as_local() {
951                            match self.locals[local] {
952                                LocalRef::Place(dest) => (dest, None),
953                                LocalRef::UnsizedPlace(_) => bug!("return type must be sized"),
954                                LocalRef::PendingOperand => {
955                                    // Currently, intrinsics always need a location to store
956                                    // the result, so we create a temporary `alloca` for the
957                                    // result.
958                                    let tmp = PlaceRef::alloca(bx, result_layout);
959                                    tmp.storage_live(bx);
960                                    (tmp, Some(local))
961                                }
962                                LocalRef::Operand(_) => {
963                                    bug!("place local already assigned to");
964                                }
965                            }
966                        } else {
967                            (self.codegen_place(bx, destination.as_ref()), None)
968                        };
969
970                        if result.val.align < result.layout.align.abi {
971                            // Currently, MIR code generation does not create calls
972                            // that store directly to fields of packed structs (in
973                            // fact, the calls it creates write only to temps).
974                            //
975                            // If someone changes that, please update this code path
976                            // to create a temporary.
977                            span_bug!(self.mir.span, "can't directly store to unaligned value");
978                        }
979
980                        let args: Vec<_> =
981                            args.iter().map(|arg| self.codegen_operand(bx, &arg.node)).collect();
982
983                        match self.codegen_intrinsic_call(bx, instance, &args, result, source_info)
984                        {
985                            Ok(()) => {
986                                if let Some(local) = store_in_local {
987                                    let op = bx.load_operand(result);
988                                    result.storage_dead(bx);
989                                    self.overwrite_local(local, LocalRef::Operand(op));
990                                    self.debug_introduce_local(bx, local);
991                                }
992
993                                return if let Some(target) = target {
994                                    helper.funclet_br(self, bx, target, mergeable_succ)
995                                } else {
996                                    bx.unreachable();
997                                    MergingSucc::False
998                                };
999                            }
1000                            Err(instance) => {
1001                                if intrinsic.must_be_overridden {
1002                                    span_bug!(
1003                                        fn_span,
1004                                        "intrinsic {} must be overridden by codegen backend, but isn't",
1005                                        intrinsic.name,
1006                                    );
1007                                }
1008                                instance
1009                            }
1010                        }
1011                    }
1012                    _ => instance,
1013                };
1014
1015                (Some(instance), None)
1016            }
1017            ty::FnPtr(..) => (None, Some(callee.immediate())),
1018            _ => bug!("{} is not callable", callee.layout.ty),
1019        };
1020
1021        // FIXME(eddyb) avoid computing this if possible, when `instance` is
1022        // available - right now `sig` is only needed for getting the `abi`
1023        // and figuring out how many extra args were passed to a C-variadic `fn`.
1024        let sig = callee.layout.ty.fn_sig(bx.tcx());
1025
1026        let extra_args = &args[sig.inputs().skip_binder().len()..];
1027        let extra_args = bx.tcx().mk_type_list_from_iter(extra_args.iter().map(|op_arg| {
1028            let op_ty = op_arg.node.ty(self.mir, bx.tcx());
1029            self.monomorphize(op_ty)
1030        }));
1031
1032        let fn_abi = match instance {
1033            Some(instance) => bx.fn_abi_of_instance(instance, extra_args),
1034            None => bx.fn_abi_of_fn_ptr(sig, extra_args),
1035        };
1036
1037        // The arguments we'll be passing. Plus one to account for outptr, if used.
1038        let arg_count = fn_abi.args.len() + fn_abi.ret.is_indirect() as usize;
1039
1040        let mut llargs = Vec::with_capacity(arg_count);
1041
1042        // We still need to call `make_return_dest` even if there's no `target`, since
1043        // `fn_abi.ret` could be `PassMode::Indirect`, even if it is uninhabited,
1044        // and `make_return_dest` adds the return-place indirect pointer to `llargs`.
1045        let return_dest = self.make_return_dest(bx, destination, &fn_abi.ret, &mut llargs);
1046        let destination = target.map(|target| (return_dest, target));
1047
1048        // Split the rust-call tupled arguments off.
1049        let (first_args, untuple) = if sig.abi() == ExternAbi::RustCall
1050            && let Some((tup, args)) = args.split_last()
1051        {
1052            (args, Some(tup))
1053        } else {
1054            (args, None)
1055        };
1056
1057        // When generating arguments we sometimes introduce temporary allocations with lifetime
1058        // that extend for the duration of a call. Keep track of those allocations and their sizes
1059        // to generate `lifetime_end` when the call returns.
1060        let mut lifetime_ends_after_call: Vec<(Bx::Value, Size)> = Vec::new();
1061        'make_args: for (i, arg) in first_args.iter().enumerate() {
1062            let mut op = self.codegen_operand(bx, &arg.node);
1063
1064            if let (0, Some(ty::InstanceKind::Virtual(_, idx))) = (i, instance.map(|i| i.def)) {
1065                match op.val {
1066                    Pair(data_ptr, meta) => {
1067                        // In the case of Rc<Self>, we need to explicitly pass a
1068                        // *mut RcInner<Self> with a Scalar (not ScalarPair) ABI. This is a hack
1069                        // that is understood elsewhere in the compiler as a method on
1070                        // `dyn Trait`.
1071                        // To get a `*mut RcInner<Self>`, we just keep unwrapping newtypes until
1072                        // we get a value of a built-in pointer type.
1073                        //
1074                        // This is also relevant for `Pin<&mut Self>`, where we need to peel the
1075                        // `Pin`.
1076                        while !op.layout.ty.is_raw_ptr() && !op.layout.ty.is_ref() {
1077                            let (idx, _) = op.layout.non_1zst_field(bx).expect(
1078                                "not exactly one non-1-ZST field in a `DispatchFromDyn` type",
1079                            );
1080                            op = op.extract_field(self, bx, idx.as_usize());
1081                        }
1082
1083                        // Now that we have `*dyn Trait` or `&dyn Trait`, split it up into its
1084                        // data pointer and vtable. Look up the method in the vtable, and pass
1085                        // the data pointer as the first argument.
1086                        llfn = Some(meth::VirtualIndex::from_index(idx).get_fn(
1087                            bx,
1088                            meta,
1089                            op.layout.ty,
1090                            fn_abi,
1091                        ));
1092                        llargs.push(data_ptr);
1093                        continue 'make_args;
1094                    }
1095                    Ref(PlaceValue { llval: data_ptr, llextra: Some(meta), .. }) => {
1096                        // by-value dynamic dispatch
1097                        llfn = Some(meth::VirtualIndex::from_index(idx).get_fn(
1098                            bx,
1099                            meta,
1100                            op.layout.ty,
1101                            fn_abi,
1102                        ));
1103                        llargs.push(data_ptr);
1104                        continue;
1105                    }
1106                    Immediate(_) => {
1107                        // See comment above explaining why we peel these newtypes
1108                        while !op.layout.ty.is_raw_ptr() && !op.layout.ty.is_ref() {
1109                            let (idx, _) = op.layout.non_1zst_field(bx).expect(
1110                                "not exactly one non-1-ZST field in a `DispatchFromDyn` type",
1111                            );
1112                            op = op.extract_field(self, bx, idx.as_usize());
1113                        }
1114
1115                        // Make sure that we've actually unwrapped the rcvr down
1116                        // to a pointer or ref to `dyn* Trait`.
1117                        if !op.layout.ty.builtin_deref(true).unwrap().is_dyn_star() {
1118                            span_bug!(fn_span, "can't codegen a virtual call on {:#?}", op);
1119                        }
1120                        let place = op.deref(bx.cx());
1121                        let data_place = place.project_field(bx, 0);
1122                        let meta_place = place.project_field(bx, 1);
1123                        let meta = bx.load_operand(meta_place);
1124                        llfn = Some(meth::VirtualIndex::from_index(idx).get_fn(
1125                            bx,
1126                            meta.immediate(),
1127                            op.layout.ty,
1128                            fn_abi,
1129                        ));
1130                        llargs.push(data_place.val.llval);
1131                        continue;
1132                    }
1133                    _ => {
1134                        span_bug!(fn_span, "can't codegen a virtual call on {:#?}", op);
1135                    }
1136                }
1137            }
1138
1139            // The callee needs to own the argument memory if we pass it
1140            // by-ref, so make a local copy of non-immediate constants.
1141            match (&arg.node, op.val) {
1142                (&mir::Operand::Copy(_), Ref(PlaceValue { llextra: None, .. }))
1143                | (&mir::Operand::Constant(_), Ref(PlaceValue { llextra: None, .. })) => {
1144                    let tmp = PlaceRef::alloca(bx, op.layout);
1145                    bx.lifetime_start(tmp.val.llval, tmp.layout.size);
1146                    op.val.store(bx, tmp);
1147                    op.val = Ref(tmp.val);
1148                    lifetime_ends_after_call.push((tmp.val.llval, tmp.layout.size));
1149                }
1150                _ => {}
1151            }
1152
1153            self.codegen_argument(
1154                bx,
1155                op,
1156                &mut llargs,
1157                &fn_abi.args[i],
1158                &mut lifetime_ends_after_call,
1159            );
1160        }
1161        let num_untupled = untuple.map(|tup| {
1162            self.codegen_arguments_untupled(
1163                bx,
1164                &tup.node,
1165                &mut llargs,
1166                &fn_abi.args[first_args.len()..],
1167                &mut lifetime_ends_after_call,
1168            )
1169        });
1170
1171        let needs_location =
1172            instance.is_some_and(|i| i.def.requires_caller_location(self.cx.tcx()));
1173        if needs_location {
1174            let mir_args = if let Some(num_untupled) = num_untupled {
1175                first_args.len() + num_untupled
1176            } else {
1177                args.len()
1178            };
1179            assert_eq!(
1180                fn_abi.args.len(),
1181                mir_args + 1,
1182                "#[track_caller] fn's must have 1 more argument in their ABI than in their MIR: {instance:?} {fn_span:?} {fn_abi:?}",
1183            );
1184            let location = self.get_caller_location(bx, source_info);
1185            debug!(
1186                "codegen_call_terminator({:?}): location={:?} (fn_span {:?})",
1187                terminator, location, fn_span
1188            );
1189
1190            let last_arg = fn_abi.args.last().unwrap();
1191            self.codegen_argument(
1192                bx,
1193                location,
1194                &mut llargs,
1195                last_arg,
1196                &mut lifetime_ends_after_call,
1197            );
1198        }
1199
1200        let fn_ptr = match (instance, llfn) {
1201            (Some(instance), None) => bx.get_fn_addr(instance),
1202            (_, Some(llfn)) => llfn,
1203            _ => span_bug!(fn_span, "no instance or llfn for call"),
1204        };
1205        self.set_debug_loc(bx, source_info);
1206        helper.do_call(
1207            self,
1208            bx,
1209            fn_abi,
1210            fn_ptr,
1211            &llargs,
1212            destination,
1213            unwind,
1214            &lifetime_ends_after_call,
1215            instance,
1216            mergeable_succ,
1217        )
1218    }
1219
1220    fn codegen_asm_terminator(
1221        &mut self,
1222        helper: TerminatorCodegenHelper<'tcx>,
1223        bx: &mut Bx,
1224        asm_macro: InlineAsmMacro,
1225        terminator: &mir::Terminator<'tcx>,
1226        template: &[ast::InlineAsmTemplatePiece],
1227        operands: &[mir::InlineAsmOperand<'tcx>],
1228        options: ast::InlineAsmOptions,
1229        line_spans: &[Span],
1230        targets: &[mir::BasicBlock],
1231        unwind: mir::UnwindAction,
1232        instance: Instance<'_>,
1233        mergeable_succ: bool,
1234    ) -> MergingSucc {
1235        let span = terminator.source_info.span;
1236
1237        let operands: Vec<_> = operands
1238            .iter()
1239            .map(|op| match *op {
1240                mir::InlineAsmOperand::In { reg, ref value } => {
1241                    let value = self.codegen_operand(bx, value);
1242                    InlineAsmOperandRef::In { reg, value }
1243                }
1244                mir::InlineAsmOperand::Out { reg, late, ref place } => {
1245                    let place = place.map(|place| self.codegen_place(bx, place.as_ref()));
1246                    InlineAsmOperandRef::Out { reg, late, place }
1247                }
1248                mir::InlineAsmOperand::InOut { reg, late, ref in_value, ref out_place } => {
1249                    let in_value = self.codegen_operand(bx, in_value);
1250                    let out_place =
1251                        out_place.map(|out_place| self.codegen_place(bx, out_place.as_ref()));
1252                    InlineAsmOperandRef::InOut { reg, late, in_value, out_place }
1253                }
1254                mir::InlineAsmOperand::Const { ref value } => {
1255                    let const_value = self.eval_mir_constant(value);
1256                    let string = common::asm_const_to_str(
1257                        bx.tcx(),
1258                        span,
1259                        const_value,
1260                        bx.layout_of(value.ty()),
1261                    );
1262                    InlineAsmOperandRef::Const { string }
1263                }
1264                mir::InlineAsmOperand::SymFn { ref value } => {
1265                    let const_ = self.monomorphize(value.const_);
1266                    if let ty::FnDef(def_id, args) = *const_.ty().kind() {
1267                        let instance = ty::Instance::resolve_for_fn_ptr(
1268                            bx.tcx(),
1269                            bx.typing_env(),
1270                            def_id,
1271                            args,
1272                        )
1273                        .unwrap();
1274                        InlineAsmOperandRef::SymFn { instance }
1275                    } else {
1276                        span_bug!(span, "invalid type for asm sym (fn)");
1277                    }
1278                }
1279                mir::InlineAsmOperand::SymStatic { def_id } => {
1280                    InlineAsmOperandRef::SymStatic { def_id }
1281                }
1282                mir::InlineAsmOperand::Label { target_index } => {
1283                    InlineAsmOperandRef::Label { label: self.llbb(targets[target_index]) }
1284                }
1285            })
1286            .collect();
1287
1288        helper.do_inlineasm(
1289            self,
1290            bx,
1291            template,
1292            &operands,
1293            options,
1294            line_spans,
1295            if asm_macro.diverges(options) { None } else { targets.get(0).copied() },
1296            unwind,
1297            instance,
1298            mergeable_succ,
1299        )
1300    }
1301
1302    pub(crate) fn codegen_block(&mut self, mut bb: mir::BasicBlock) {
1303        let llbb = match self.try_llbb(bb) {
1304            Some(llbb) => llbb,
1305            None => return,
1306        };
1307        let bx = &mut Bx::build(self.cx, llbb);
1308        let mir = self.mir;
1309
1310        // MIR basic blocks stop at any function call. This may not be the case
1311        // for the backend's basic blocks, in which case we might be able to
1312        // combine multiple MIR basic blocks into a single backend basic block.
1313        loop {
1314            let data = &mir[bb];
1315
1316            debug!("codegen_block({:?}={:?})", bb, data);
1317
1318            for statement in &data.statements {
1319                self.codegen_statement(bx, statement);
1320            }
1321
1322            let merging_succ = self.codegen_terminator(bx, bb, data.terminator());
1323            if let MergingSucc::False = merging_succ {
1324                break;
1325            }
1326
1327            // We are merging the successor into the produced backend basic
1328            // block. Record that the successor should be skipped when it is
1329            // reached.
1330            //
1331            // Note: we must not have already generated code for the successor.
1332            // This is implicitly ensured by the reverse postorder traversal,
1333            // and the assertion explicitly guarantees that.
1334            let mut successors = data.terminator().successors();
1335            let succ = successors.next().unwrap();
1336            assert!(matches!(self.cached_llbbs[succ], CachedLlbb::None));
1337            self.cached_llbbs[succ] = CachedLlbb::Skip;
1338            bb = succ;
1339        }
1340    }
1341
1342    pub(crate) fn codegen_block_as_unreachable(&mut self, bb: mir::BasicBlock) {
1343        let llbb = match self.try_llbb(bb) {
1344            Some(llbb) => llbb,
1345            None => return,
1346        };
1347        let bx = &mut Bx::build(self.cx, llbb);
1348        debug!("codegen_block_as_unreachable({:?})", bb);
1349        bx.unreachable();
1350    }
1351
1352    fn codegen_terminator(
1353        &mut self,
1354        bx: &mut Bx,
1355        bb: mir::BasicBlock,
1356        terminator: &'tcx mir::Terminator<'tcx>,
1357    ) -> MergingSucc {
1358        debug!("codegen_terminator: {:?}", terminator);
1359
1360        let helper = TerminatorCodegenHelper { bb, terminator };
1361
1362        let mergeable_succ = || {
1363            // Note: any call to `switch_to_block` will invalidate a `true` value
1364            // of `mergeable_succ`.
1365            let mut successors = terminator.successors();
1366            if let Some(succ) = successors.next()
1367                && successors.next().is_none()
1368                && let &[succ_pred] = self.mir.basic_blocks.predecessors()[succ].as_slice()
1369            {
1370                // bb has a single successor, and bb is its only predecessor. This
1371                // makes it a candidate for merging.
1372                assert_eq!(succ_pred, bb);
1373                true
1374            } else {
1375                false
1376            }
1377        };
1378
1379        self.set_debug_loc(bx, terminator.source_info);
1380        match terminator.kind {
1381            mir::TerminatorKind::UnwindResume => {
1382                self.codegen_resume_terminator(helper, bx);
1383                MergingSucc::False
1384            }
1385
1386            mir::TerminatorKind::UnwindTerminate(reason) => {
1387                self.codegen_terminate_terminator(helper, bx, terminator, reason);
1388                MergingSucc::False
1389            }
1390
1391            mir::TerminatorKind::Goto { target } => {
1392                helper.funclet_br(self, bx, target, mergeable_succ())
1393            }
1394
1395            mir::TerminatorKind::SwitchInt { ref discr, ref targets } => {
1396                self.codegen_switchint_terminator(helper, bx, discr, targets);
1397                MergingSucc::False
1398            }
1399
1400            mir::TerminatorKind::Return => {
1401                self.codegen_return_terminator(bx);
1402                MergingSucc::False
1403            }
1404
1405            mir::TerminatorKind::Unreachable => {
1406                bx.unreachable();
1407                MergingSucc::False
1408            }
1409
1410            mir::TerminatorKind::Drop { place, target, unwind, replace: _, drop, async_fut } => {
1411                assert!(
1412                    async_fut.is_none() && drop.is_none(),
1413                    "Async Drop must be expanded or reset to sync before codegen"
1414                );
1415                self.codegen_drop_terminator(
1416                    helper,
1417                    bx,
1418                    &terminator.source_info,
1419                    place,
1420                    target,
1421                    unwind,
1422                    mergeable_succ(),
1423                )
1424            }
1425
1426            mir::TerminatorKind::Assert { ref cond, expected, ref msg, target, unwind } => self
1427                .codegen_assert_terminator(
1428                    helper,
1429                    bx,
1430                    terminator,
1431                    cond,
1432                    expected,
1433                    msg,
1434                    target,
1435                    unwind,
1436                    mergeable_succ(),
1437                ),
1438
1439            mir::TerminatorKind::Call {
1440                ref func,
1441                ref args,
1442                destination,
1443                target,
1444                unwind,
1445                call_source: _,
1446                fn_span,
1447            } => self.codegen_call_terminator(
1448                helper,
1449                bx,
1450                terminator,
1451                func,
1452                args,
1453                destination,
1454                target,
1455                unwind,
1456                fn_span,
1457                mergeable_succ(),
1458            ),
1459            mir::TerminatorKind::TailCall { .. } => {
1460                // FIXME(explicit_tail_calls): implement tail calls in ssa backend
1461                span_bug!(
1462                    terminator.source_info.span,
1463                    "`TailCall` terminator is not yet supported by `rustc_codegen_ssa`"
1464                )
1465            }
1466            mir::TerminatorKind::CoroutineDrop | mir::TerminatorKind::Yield { .. } => {
1467                bug!("coroutine ops in codegen")
1468            }
1469            mir::TerminatorKind::FalseEdge { .. } | mir::TerminatorKind::FalseUnwind { .. } => {
1470                bug!("borrowck false edges in codegen")
1471            }
1472
1473            mir::TerminatorKind::InlineAsm {
1474                asm_macro,
1475                template,
1476                ref operands,
1477                options,
1478                line_spans,
1479                ref targets,
1480                unwind,
1481            } => self.codegen_asm_terminator(
1482                helper,
1483                bx,
1484                asm_macro,
1485                terminator,
1486                template,
1487                operands,
1488                options,
1489                line_spans,
1490                targets,
1491                unwind,
1492                self.instance,
1493                mergeable_succ(),
1494            ),
1495        }
1496    }
1497
1498    fn codegen_argument(
1499        &mut self,
1500        bx: &mut Bx,
1501        op: OperandRef<'tcx, Bx::Value>,
1502        llargs: &mut Vec<Bx::Value>,
1503        arg: &ArgAbi<'tcx, Ty<'tcx>>,
1504        lifetime_ends_after_call: &mut Vec<(Bx::Value, Size)>,
1505    ) {
1506        match arg.mode {
1507            PassMode::Ignore => return,
1508            PassMode::Cast { pad_i32: true, .. } => {
1509                // Fill padding with undef value, where applicable.
1510                llargs.push(bx.const_undef(bx.reg_backend_type(&Reg::i32())));
1511            }
1512            PassMode::Pair(..) => match op.val {
1513                Pair(a, b) => {
1514                    llargs.push(a);
1515                    llargs.push(b);
1516                    return;
1517                }
1518                _ => bug!("codegen_argument: {:?} invalid for pair argument", op),
1519            },
1520            PassMode::Indirect { attrs: _, meta_attrs: Some(_), on_stack: _ } => match op.val {
1521                Ref(PlaceValue { llval: a, llextra: Some(b), .. }) => {
1522                    llargs.push(a);
1523                    llargs.push(b);
1524                    return;
1525                }
1526                _ => bug!("codegen_argument: {:?} invalid for unsized indirect argument", op),
1527            },
1528            _ => {}
1529        }
1530
1531        // Force by-ref if we have to load through a cast pointer.
1532        let (mut llval, align, by_ref) = match op.val {
1533            Immediate(_) | Pair(..) => match arg.mode {
1534                PassMode::Indirect { attrs, .. } => {
1535                    // Indirect argument may have higher alignment requirements than the type's
1536                    // alignment. This can happen, e.g. when passing types with <4 byte alignment
1537                    // on the stack on x86.
1538                    let required_align = match attrs.pointee_align {
1539                        Some(pointee_align) => cmp::max(pointee_align, arg.layout.align.abi),
1540                        None => arg.layout.align.abi,
1541                    };
1542                    let scratch = PlaceValue::alloca(bx, arg.layout.size, required_align);
1543                    bx.lifetime_start(scratch.llval, arg.layout.size);
1544                    op.val.store(bx, scratch.with_type(arg.layout));
1545                    lifetime_ends_after_call.push((scratch.llval, arg.layout.size));
1546                    (scratch.llval, scratch.align, true)
1547                }
1548                PassMode::Cast { .. } => {
1549                    let scratch = PlaceRef::alloca(bx, arg.layout);
1550                    op.val.store(bx, scratch);
1551                    (scratch.val.llval, scratch.val.align, true)
1552                }
1553                _ => (op.immediate_or_packed_pair(bx), arg.layout.align.abi, false),
1554            },
1555            Ref(op_place_val) => match arg.mode {
1556                PassMode::Indirect { attrs, .. } => {
1557                    let required_align = match attrs.pointee_align {
1558                        Some(pointee_align) => cmp::max(pointee_align, arg.layout.align.abi),
1559                        None => arg.layout.align.abi,
1560                    };
1561                    if op_place_val.align < required_align {
1562                        // For `foo(packed.large_field)`, and types with <4 byte alignment on x86,
1563                        // alignment requirements may be higher than the type's alignment, so copy
1564                        // to a higher-aligned alloca.
1565                        let scratch = PlaceValue::alloca(bx, arg.layout.size, required_align);
1566                        bx.lifetime_start(scratch.llval, arg.layout.size);
1567                        bx.typed_place_copy(scratch, op_place_val, op.layout);
1568                        lifetime_ends_after_call.push((scratch.llval, arg.layout.size));
1569                        (scratch.llval, scratch.align, true)
1570                    } else {
1571                        (op_place_val.llval, op_place_val.align, true)
1572                    }
1573                }
1574                _ => (op_place_val.llval, op_place_val.align, true),
1575            },
1576            ZeroSized => match arg.mode {
1577                PassMode::Indirect { on_stack, .. } => {
1578                    if on_stack {
1579                        // It doesn't seem like any target can have `byval` ZSTs, so this assert
1580                        // is here to replace a would-be untested codepath.
1581                        bug!("ZST {op:?} passed on stack with abi {arg:?}");
1582                    }
1583                    // Though `extern "Rust"` doesn't pass ZSTs, some ABIs pass
1584                    // a pointer for `repr(C)` structs even when empty, so get
1585                    // one from an `alloca` (which can be left uninitialized).
1586                    let scratch = PlaceRef::alloca(bx, arg.layout);
1587                    (scratch.val.llval, scratch.val.align, true)
1588                }
1589                _ => bug!("ZST {op:?} wasn't ignored, but was passed with abi {arg:?}"),
1590            },
1591        };
1592
1593        if by_ref && !arg.is_indirect() {
1594            // Have to load the argument, maybe while casting it.
1595            if let PassMode::Cast { cast, pad_i32: _ } = &arg.mode {
1596                // The ABI mandates that the value is passed as a different struct representation.
1597                // Spill and reload it from the stack to convert from the Rust representation to
1598                // the ABI representation.
1599                let scratch_size = cast.size(bx);
1600                let scratch_align = cast.align(bx);
1601                // Note that the ABI type may be either larger or smaller than the Rust type,
1602                // due to the presence or absence of trailing padding. For example:
1603                // - On some ABIs, the Rust layout { f64, f32, <f32 padding> } may omit padding
1604                //   when passed by value, making it smaller.
1605                // - On some ABIs, the Rust layout { u16, u16, u16 } may be padded up to 8 bytes
1606                //   when passed by value, making it larger.
1607                let copy_bytes = cmp::min(cast.unaligned_size(bx).bytes(), arg.layout.size.bytes());
1608                // Allocate some scratch space...
1609                let llscratch = bx.alloca(scratch_size, scratch_align);
1610                bx.lifetime_start(llscratch, scratch_size);
1611                // ...memcpy the value...
1612                bx.memcpy(
1613                    llscratch,
1614                    scratch_align,
1615                    llval,
1616                    align,
1617                    bx.const_usize(copy_bytes),
1618                    MemFlags::empty(),
1619                );
1620                // ...and then load it with the ABI type.
1621                let cast_ty = bx.cast_backend_type(cast);
1622                llval = bx.load(cast_ty, llscratch, scratch_align);
1623                bx.lifetime_end(llscratch, scratch_size);
1624            } else {
1625                // We can't use `PlaceRef::load` here because the argument
1626                // may have a type we don't treat as immediate, but the ABI
1627                // used for this call is passing it by-value. In that case,
1628                // the load would just produce `OperandValue::Ref` instead
1629                // of the `OperandValue::Immediate` we need for the call.
1630                llval = bx.load(bx.backend_type(arg.layout), llval, align);
1631                if let BackendRepr::Scalar(scalar) = arg.layout.backend_repr {
1632                    if scalar.is_bool() {
1633                        bx.range_metadata(llval, WrappingRange { start: 0, end: 1 });
1634                    }
1635                    // We store bools as `i8` so we need to truncate to `i1`.
1636                    llval = bx.to_immediate_scalar(llval, scalar);
1637                }
1638            }
1639        }
1640
1641        llargs.push(llval);
1642    }
1643
1644    fn codegen_arguments_untupled(
1645        &mut self,
1646        bx: &mut Bx,
1647        operand: &mir::Operand<'tcx>,
1648        llargs: &mut Vec<Bx::Value>,
1649        args: &[ArgAbi<'tcx, Ty<'tcx>>],
1650        lifetime_ends_after_call: &mut Vec<(Bx::Value, Size)>,
1651    ) -> usize {
1652        let tuple = self.codegen_operand(bx, operand);
1653
1654        // Handle both by-ref and immediate tuples.
1655        if let Ref(place_val) = tuple.val {
1656            if place_val.llextra.is_some() {
1657                bug!("closure arguments must be sized");
1658            }
1659            let tuple_ptr = place_val.with_type(tuple.layout);
1660            for i in 0..tuple.layout.fields.count() {
1661                let field_ptr = tuple_ptr.project_field(bx, i);
1662                let field = bx.load_operand(field_ptr);
1663                self.codegen_argument(bx, field, llargs, &args[i], lifetime_ends_after_call);
1664            }
1665        } else {
1666            // If the tuple is immediate, the elements are as well.
1667            for i in 0..tuple.layout.fields.count() {
1668                let op = tuple.extract_field(self, bx, i);
1669                self.codegen_argument(bx, op, llargs, &args[i], lifetime_ends_after_call);
1670            }
1671        }
1672        tuple.layout.fields.count()
1673    }
1674
1675    pub(super) fn get_caller_location(
1676        &mut self,
1677        bx: &mut Bx,
1678        source_info: mir::SourceInfo,
1679    ) -> OperandRef<'tcx, Bx::Value> {
1680        self.mir.caller_location_span(source_info, self.caller_location, bx.tcx(), |span: Span| {
1681            let const_loc = bx.tcx().span_as_caller_location(span);
1682            OperandRef::from_const(bx, const_loc, bx.tcx().caller_location_ty())
1683        })
1684    }
1685
1686    fn get_personality_slot(&mut self, bx: &mut Bx) -> PlaceRef<'tcx, Bx::Value> {
1687        let cx = bx.cx();
1688        if let Some(slot) = self.personality_slot {
1689            slot
1690        } else {
1691            let layout = cx.layout_of(Ty::new_tup(
1692                cx.tcx(),
1693                &[Ty::new_mut_ptr(cx.tcx(), cx.tcx().types.u8), cx.tcx().types.i32],
1694            ));
1695            let slot = PlaceRef::alloca(bx, layout);
1696            self.personality_slot = Some(slot);
1697            slot
1698        }
1699    }
1700
1701    /// Returns the landing/cleanup pad wrapper around the given basic block.
1702    // FIXME(eddyb) rename this to `eh_pad_for`.
1703    fn landing_pad_for(&mut self, bb: mir::BasicBlock) -> Bx::BasicBlock {
1704        if let Some(landing_pad) = self.landing_pads[bb] {
1705            return landing_pad;
1706        }
1707
1708        let landing_pad = self.landing_pad_for_uncached(bb);
1709        self.landing_pads[bb] = Some(landing_pad);
1710        landing_pad
1711    }
1712
1713    // FIXME(eddyb) rename this to `eh_pad_for_uncached`.
1714    fn landing_pad_for_uncached(&mut self, bb: mir::BasicBlock) -> Bx::BasicBlock {
1715        let llbb = self.llbb(bb);
1716        if base::wants_new_eh_instructions(self.cx.sess()) {
1717            let cleanup_bb = Bx::append_block(self.cx, self.llfn, &format!("funclet_{bb:?}"));
1718            let mut cleanup_bx = Bx::build(self.cx, cleanup_bb);
1719            let funclet = cleanup_bx.cleanup_pad(None, &[]);
1720            cleanup_bx.br(llbb);
1721            self.funclets[bb] = Some(funclet);
1722            cleanup_bb
1723        } else {
1724            let cleanup_llbb = Bx::append_block(self.cx, self.llfn, "cleanup");
1725            let mut cleanup_bx = Bx::build(self.cx, cleanup_llbb);
1726
1727            let llpersonality = self.cx.eh_personality();
1728            let (exn0, exn1) = cleanup_bx.cleanup_landing_pad(llpersonality);
1729
1730            let slot = self.get_personality_slot(&mut cleanup_bx);
1731            slot.storage_live(&mut cleanup_bx);
1732            Pair(exn0, exn1).store(&mut cleanup_bx, slot);
1733
1734            cleanup_bx.br(llbb);
1735            cleanup_llbb
1736        }
1737    }
1738
1739    fn unreachable_block(&mut self) -> Bx::BasicBlock {
1740        self.unreachable_block.unwrap_or_else(|| {
1741            let llbb = Bx::append_block(self.cx, self.llfn, "unreachable");
1742            let mut bx = Bx::build(self.cx, llbb);
1743            bx.unreachable();
1744            self.unreachable_block = Some(llbb);
1745            llbb
1746        })
1747    }
1748
1749    fn terminate_block(&mut self, reason: UnwindTerminateReason) -> Bx::BasicBlock {
1750        if let Some((cached_bb, cached_reason)) = self.terminate_block
1751            && reason == cached_reason
1752        {
1753            return cached_bb;
1754        }
1755
1756        let funclet;
1757        let llbb;
1758        let mut bx;
1759        if base::wants_new_eh_instructions(self.cx.sess()) {
1760            // This is a basic block that we're aborting the program for,
1761            // notably in an `extern` function. These basic blocks are inserted
1762            // so that we assert that `extern` functions do indeed not panic,
1763            // and if they do we abort the process.
1764            //
1765            // On MSVC these are tricky though (where we're doing funclets). If
1766            // we were to do a cleanuppad (like below) the normal functions like
1767            // `longjmp` would trigger the abort logic, terminating the
1768            // program. Instead we insert the equivalent of `catch(...)` for C++
1769            // which magically doesn't trigger when `longjmp` files over this
1770            // frame.
1771            //
1772            // Lots more discussion can be found on #48251 but this codegen is
1773            // modeled after clang's for:
1774            //
1775            //      try {
1776            //          foo();
1777            //      } catch (...) {
1778            //          bar();
1779            //      }
1780            //
1781            // which creates an IR snippet like
1782            //
1783            //      cs_terminate:
1784            //         %cs = catchswitch within none [%cp_terminate] unwind to caller
1785            //      cp_terminate:
1786            //         %cp = catchpad within %cs [null, i32 64, null]
1787            //         ...
1788
1789            llbb = Bx::append_block(self.cx, self.llfn, "cs_terminate");
1790            let cp_llbb = Bx::append_block(self.cx, self.llfn, "cp_terminate");
1791
1792            let mut cs_bx = Bx::build(self.cx, llbb);
1793            let cs = cs_bx.catch_switch(None, None, &[cp_llbb]);
1794
1795            bx = Bx::build(self.cx, cp_llbb);
1796            let null =
1797                bx.const_null(bx.type_ptr_ext(bx.cx().data_layout().instruction_address_space));
1798
1799            // The `null` in first argument here is actually a RTTI type
1800            // descriptor for the C++ personality function, but `catch (...)`
1801            // has no type so it's null.
1802            let args = if base::wants_msvc_seh(self.cx.sess()) {
1803                // This bitmask is a single `HT_IsStdDotDot` flag, which
1804                // represents that this is a C++-style `catch (...)` block that
1805                // only captures programmatic exceptions, not all SEH
1806                // exceptions. The second `null` points to a non-existent
1807                // `alloca` instruction, which an LLVM pass would inline into
1808                // the initial SEH frame allocation.
1809                let adjectives = bx.const_i32(0x40);
1810                &[null, adjectives, null] as &[_]
1811            } else {
1812                // Specifying more arguments than necessary usually doesn't
1813                // hurt, but the `WasmEHPrepare` LLVM pass does not recognize
1814                // anything other than a single `null` as a `catch (...)` block,
1815                // leading to problems down the line during instruction
1816                // selection.
1817                &[null] as &[_]
1818            };
1819
1820            funclet = Some(bx.catch_pad(cs, args));
1821        } else {
1822            llbb = Bx::append_block(self.cx, self.llfn, "terminate");
1823            bx = Bx::build(self.cx, llbb);
1824
1825            let llpersonality = self.cx.eh_personality();
1826            bx.filter_landing_pad(llpersonality);
1827
1828            funclet = None;
1829        }
1830
1831        self.set_debug_loc(&mut bx, mir::SourceInfo::outermost(self.mir.span));
1832
1833        let (fn_abi, fn_ptr, instance) =
1834            common::build_langcall(&bx, self.mir.span, reason.lang_item());
1835        if is_call_from_compiler_builtins_to_upstream_monomorphization(bx.tcx(), instance) {
1836            bx.abort();
1837        } else {
1838            let fn_ty = bx.fn_decl_backend_type(fn_abi);
1839
1840            let llret = bx.call(fn_ty, None, Some(fn_abi), fn_ptr, &[], funclet.as_ref(), None);
1841            bx.apply_attrs_to_cleanup_callsite(llret);
1842        }
1843
1844        bx.unreachable();
1845
1846        self.terminate_block = Some((llbb, reason));
1847        llbb
1848    }
1849
1850    /// Get the backend `BasicBlock` for a MIR `BasicBlock`, either already
1851    /// cached in `self.cached_llbbs`, or created on demand (and cached).
1852    // FIXME(eddyb) rename `llbb` and other `ll`-prefixed things to use a
1853    // more backend-agnostic prefix such as `cg` (i.e. this would be `cgbb`).
1854    pub fn llbb(&mut self, bb: mir::BasicBlock) -> Bx::BasicBlock {
1855        self.try_llbb(bb).unwrap()
1856    }
1857
1858    /// Like `llbb`, but may fail if the basic block should be skipped.
1859    pub(crate) fn try_llbb(&mut self, bb: mir::BasicBlock) -> Option<Bx::BasicBlock> {
1860        match self.cached_llbbs[bb] {
1861            CachedLlbb::None => {
1862                let llbb = Bx::append_block(self.cx, self.llfn, &format!("{bb:?}"));
1863                self.cached_llbbs[bb] = CachedLlbb::Some(llbb);
1864                Some(llbb)
1865            }
1866            CachedLlbb::Some(llbb) => Some(llbb),
1867            CachedLlbb::Skip => None,
1868        }
1869    }
1870
1871    fn make_return_dest(
1872        &mut self,
1873        bx: &mut Bx,
1874        dest: mir::Place<'tcx>,
1875        fn_ret: &ArgAbi<'tcx, Ty<'tcx>>,
1876        llargs: &mut Vec<Bx::Value>,
1877    ) -> ReturnDest<'tcx, Bx::Value> {
1878        // If the return is ignored, we can just return a do-nothing `ReturnDest`.
1879        if fn_ret.is_ignore() {
1880            return ReturnDest::Nothing;
1881        }
1882        let dest = if let Some(index) = dest.as_local() {
1883            match self.locals[index] {
1884                LocalRef::Place(dest) => dest,
1885                LocalRef::UnsizedPlace(_) => bug!("return type must be sized"),
1886                LocalRef::PendingOperand => {
1887                    // Handle temporary places, specifically `Operand` ones, as
1888                    // they don't have `alloca`s.
1889                    return if fn_ret.is_indirect() {
1890                        // Odd, but possible, case, we have an operand temporary,
1891                        // but the calling convention has an indirect return.
1892                        let tmp = PlaceRef::alloca(bx, fn_ret.layout);
1893                        tmp.storage_live(bx);
1894                        llargs.push(tmp.val.llval);
1895                        ReturnDest::IndirectOperand(tmp, index)
1896                    } else {
1897                        ReturnDest::DirectOperand(index)
1898                    };
1899                }
1900                LocalRef::Operand(_) => {
1901                    bug!("place local already assigned to");
1902                }
1903            }
1904        } else {
1905            self.codegen_place(bx, dest.as_ref())
1906        };
1907        if fn_ret.is_indirect() {
1908            if dest.val.align < dest.layout.align.abi {
1909                // Currently, MIR code generation does not create calls
1910                // that store directly to fields of packed structs (in
1911                // fact, the calls it creates write only to temps).
1912                //
1913                // If someone changes that, please update this code path
1914                // to create a temporary.
1915                span_bug!(self.mir.span, "can't directly store to unaligned value");
1916            }
1917            llargs.push(dest.val.llval);
1918            ReturnDest::Nothing
1919        } else {
1920            ReturnDest::Store(dest)
1921        }
1922    }
1923
1924    // Stores the return value of a function call into it's final location.
1925    fn store_return(
1926        &mut self,
1927        bx: &mut Bx,
1928        dest: ReturnDest<'tcx, Bx::Value>,
1929        ret_abi: &ArgAbi<'tcx, Ty<'tcx>>,
1930        llval: Bx::Value,
1931    ) {
1932        use self::ReturnDest::*;
1933
1934        match dest {
1935            Nothing => (),
1936            Store(dst) => bx.store_arg(ret_abi, llval, dst),
1937            IndirectOperand(tmp, index) => {
1938                let op = bx.load_operand(tmp);
1939                tmp.storage_dead(bx);
1940                self.overwrite_local(index, LocalRef::Operand(op));
1941                self.debug_introduce_local(bx, index);
1942            }
1943            DirectOperand(index) => {
1944                // If there is a cast, we have to store and reload.
1945                let op = if let PassMode::Cast { .. } = ret_abi.mode {
1946                    let tmp = PlaceRef::alloca(bx, ret_abi.layout);
1947                    tmp.storage_live(bx);
1948                    bx.store_arg(ret_abi, llval, tmp);
1949                    let op = bx.load_operand(tmp);
1950                    tmp.storage_dead(bx);
1951                    op
1952                } else {
1953                    OperandRef::from_immediate_or_packed_pair(bx, llval, ret_abi.layout)
1954                };
1955                self.overwrite_local(index, LocalRef::Operand(op));
1956                self.debug_introduce_local(bx, index);
1957            }
1958        }
1959    }
1960}
1961
1962enum ReturnDest<'tcx, V> {
1963    /// Do nothing; the return value is indirect or ignored.
1964    Nothing,
1965    /// Store the return value to the pointer.
1966    Store(PlaceRef<'tcx, V>),
1967    /// Store an indirect return value to an operand local place.
1968    IndirectOperand(PlaceRef<'tcx, V>, mir::Local),
1969    /// Store a direct return value to an operand local place.
1970    DirectOperand(mir::Local),
1971}