1 use super::operand::OperandRef;
2 use super::operand::OperandValue::{Immediate, Pair, Ref};
3 use super::place::PlaceRef;
4 use super::{FunctionCx, LocalRef};
7 use crate::common::{self, IntPredicate};
13 use rustc_hir::lang_items::LangItem;
14 use rustc_index::vec::Idx;
15 use rustc_middle::mir::AssertKind;
16 use rustc_middle::mir::{self, SwitchTargets};
17 use rustc_middle::ty::layout::{FnAbiExt, HasTyCtxt, LayoutOf};
18 use rustc_middle::ty::print::with_no_trimmed_paths;
19 use rustc_middle::ty::{self, Instance, Ty, TypeFoldable};
20 use rustc_span::source_map::Span;
21 use rustc_span::{sym, Symbol};
22 use rustc_target::abi::call::{ArgAbi, FnAbi, PassMode};
23 use rustc_target::abi::{self, HasDataLayout};
24 use rustc_target::spec::abi::Abi;
26 /// Used by `FunctionCx::codegen_terminator` for emitting common patterns
27 /// e.g., creating a basic block, calling a function, etc.
28 struct TerminatorCodegenHelper<'tcx> {
30 terminator: &'tcx mir::Terminator<'tcx>,
31 funclet_bb: Option<mir::BasicBlock>,
34 impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> {
35 /// Returns the appropriate `Funclet` for the current funclet, if on MSVC,
36 /// either already previously cached, or newly created, by `landing_pad_for`.
37 fn funclet<'b, Bx: BuilderMethods<'a, 'tcx>>(
39 fx: &'b mut FunctionCx<'a, 'tcx, Bx>,
40 ) -> Option<&'b Bx::Funclet> {
41 let funclet_bb = self.funclet_bb?;
42 if base::wants_msvc_seh(fx.cx.tcx().sess) {
43 // If `landing_pad_for` hasn't been called yet to create the `Funclet`,
44 // it has to be now. This may not seem necessary, as RPO should lead
45 // to all the unwind edges being visited (and so to `landing_pad_for`
46 // getting called for them), before building any of the blocks inside
47 // the funclet itself - however, if MIR contains edges that end up not
48 // being needed in the LLVM IR after monomorphization, the funclet may
49 // be unreachable, and we don't have yet a way to skip building it in
50 // such an eventuality (which may be a better solution than this).
51 if fx.funclets[funclet_bb].is_none() {
52 fx.landing_pad_for(funclet_bb);
56 fx.funclets[funclet_bb]
58 .expect("landing_pad_for didn't also create funclets entry"),
65 fn lltarget<Bx: BuilderMethods<'a, 'tcx>>(
67 fx: &mut FunctionCx<'a, 'tcx, Bx>,
68 target: mir::BasicBlock,
69 ) -> (Bx::BasicBlock, bool) {
70 let span = self.terminator.source_info.span;
71 let lltarget = fx.llbb(target);
72 let target_funclet = fx.cleanup_kinds[target].funclet_bb(target);
73 match (self.funclet_bb, target_funclet) {
74 (None, None) => (lltarget, false),
75 (Some(f), Some(t_f)) if f == t_f || !base::wants_msvc_seh(fx.cx.tcx().sess) => {
78 // jump *into* cleanup - need a landing pad if GNU, cleanup pad if MSVC
79 (None, Some(_)) => (fx.landing_pad_for(target), false),
80 (Some(_), None) => span_bug!(span, "{:?} - jump out of cleanup?", self.terminator),
81 (Some(_), Some(_)) => (fx.landing_pad_for(target), true),
85 /// Create a basic block.
86 fn llblock<Bx: BuilderMethods<'a, 'tcx>>(
88 fx: &mut FunctionCx<'a, 'tcx, Bx>,
89 target: mir::BasicBlock,
91 let (lltarget, is_cleanupret) = self.lltarget(fx, target);
93 // MSVC cross-funclet jump - need a trampoline
95 debug!("llblock: creating cleanup trampoline for {:?}", target);
96 let name = &format!("{:?}_cleanup_trampoline_{:?}", self.bb, target);
97 let mut trampoline = fx.new_block(name);
98 trampoline.cleanup_ret(self.funclet(fx).unwrap(), Some(lltarget));
105 fn funclet_br<Bx: BuilderMethods<'a, 'tcx>>(
107 fx: &mut FunctionCx<'a, 'tcx, Bx>,
109 target: mir::BasicBlock,
111 let (lltarget, is_cleanupret) = self.lltarget(fx, target);
113 // micro-optimization: generate a `ret` rather than a jump
115 bx.cleanup_ret(self.funclet(fx).unwrap(), Some(lltarget));
121 /// Call `fn_ptr` of `fn_abi` with the arguments `llargs`, the optional
122 /// return destination `destination` and the cleanup function `cleanup`.
123 fn do_call<Bx: BuilderMethods<'a, 'tcx>>(
125 fx: &mut FunctionCx<'a, 'tcx, Bx>,
127 fn_abi: FnAbi<'tcx, Ty<'tcx>>,
129 llargs: &[Bx::Value],
130 destination: Option<(ReturnDest<'tcx, Bx::Value>, mir::BasicBlock)>,
131 cleanup: Option<mir::BasicBlock>,
133 // If there is a cleanup block and the function we're calling can unwind, then
134 // do an invoke, otherwise do a call.
135 let fn_ty = bx.fn_decl_backend_type(&fn_abi);
136 if let Some(cleanup) = cleanup.filter(|_| fn_abi.can_unwind) {
137 let ret_llbb = if let Some((_, target)) = destination {
140 fx.unreachable_block()
142 let invokeret = bx.invoke(
147 self.llblock(fx, cleanup),
150 bx.apply_attrs_callsite(&fn_abi, invokeret);
152 if let Some((ret_dest, target)) = destination {
153 let mut ret_bx = fx.build_block(target);
154 fx.set_debug_loc(&mut ret_bx, self.terminator.source_info);
155 fx.store_return(&mut ret_bx, ret_dest, &fn_abi.ret, invokeret);
158 let llret = bx.call(fn_ty, fn_ptr, &llargs, self.funclet(fx));
159 bx.apply_attrs_callsite(&fn_abi, llret);
160 if fx.mir[self.bb].is_cleanup {
161 // Cleanup is always the cold path. Don't inline
162 // drop glue. Also, when there is a deeply-nested
163 // struct, there are "symmetry" issues that cause
164 // exponential inlining - see issue #41696.
165 bx.do_not_inline(llret);
168 if let Some((ret_dest, target)) = destination {
169 fx.store_return(bx, ret_dest, &fn_abi.ret, llret);
170 self.funclet_br(fx, bx, target);
178 /// Codegen implementations for some terminator variants.
179 impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
180 /// Generates code for a `Resume` terminator.
181 fn codegen_resume_terminator(&mut self, helper: TerminatorCodegenHelper<'tcx>, mut bx: Bx) {
182 if let Some(funclet) = helper.funclet(self) {
183 bx.cleanup_ret(funclet, None);
185 let slot = self.get_personality_slot(&mut bx);
186 let lp0 = slot.project_field(&mut bx, 0);
187 let lp0 = bx.load_operand(lp0).immediate();
188 let lp1 = slot.project_field(&mut bx, 1);
189 let lp1 = bx.load_operand(lp1).immediate();
190 slot.storage_dead(&mut bx);
192 let mut lp = bx.const_undef(self.landing_pad_type());
193 lp = bx.insert_value(lp, lp0, 0);
194 lp = bx.insert_value(lp, lp1, 1);
199 fn codegen_switchint_terminator(
201 helper: TerminatorCodegenHelper<'tcx>,
203 discr: &mir::Operand<'tcx>,
205 targets: &SwitchTargets,
207 let discr = self.codegen_operand(&mut bx, &discr);
208 // `switch_ty` is redundant, sanity-check that.
209 assert_eq!(discr.layout.ty, switch_ty);
210 let mut target_iter = targets.iter();
211 if target_iter.len() == 1 {
212 // If there are two targets (one conditional, one fallback), emit br instead of switch
213 let (test_value, target) = target_iter.next().unwrap();
214 let lltrue = helper.llblock(self, target);
215 let llfalse = helper.llblock(self, targets.otherwise());
216 if switch_ty == bx.tcx().types.bool {
217 // Don't generate trivial icmps when switching on bool
219 0 => bx.cond_br(discr.immediate(), llfalse, lltrue),
220 1 => bx.cond_br(discr.immediate(), lltrue, llfalse),
224 let switch_llty = bx.immediate_backend_type(bx.layout_of(switch_ty));
225 let llval = bx.const_uint_big(switch_llty, test_value);
226 let cmp = bx.icmp(IntPredicate::IntEQ, discr.immediate(), llval);
227 bx.cond_br(cmp, lltrue, llfalse);
232 helper.llblock(self, targets.otherwise()),
233 target_iter.map(|(value, target)| (value, helper.llblock(self, target))),
238 fn codegen_return_terminator(&mut self, mut bx: Bx) {
239 // Call `va_end` if this is the definition of a C-variadic function.
240 if self.fn_abi.c_variadic {
241 // The `VaList` "spoofed" argument is just after all the real arguments.
242 let va_list_arg_idx = self.fn_abi.args.len();
243 match self.locals[mir::Local::new(1 + va_list_arg_idx)] {
244 LocalRef::Place(va_list) => {
245 bx.va_end(va_list.llval);
247 _ => bug!("C-variadic function must have a `VaList` place"),
250 if self.fn_abi.ret.layout.abi.is_uninhabited() {
251 // Functions with uninhabited return values are marked `noreturn`,
252 // so we should make sure that we never actually do.
253 // We play it safe by using a well-defined `abort`, but we could go for immediate UB
254 // if that turns out to be helpful.
256 // `abort` does not terminate the block, so we still need to generate
257 // an `unreachable` terminator after it.
261 let llval = match self.fn_abi.ret.mode {
262 PassMode::Ignore | PassMode::Indirect { .. } => {
267 PassMode::Direct(_) | PassMode::Pair(..) => {
268 let op = self.codegen_consume(&mut bx, mir::Place::return_place().as_ref());
269 if let Ref(llval, _, align) = op.val {
270 bx.load(bx.backend_type(op.layout), llval, align)
272 op.immediate_or_packed_pair(&mut bx)
276 PassMode::Cast(cast_ty) => {
277 let op = match self.locals[mir::RETURN_PLACE] {
278 LocalRef::Operand(Some(op)) => op,
279 LocalRef::Operand(None) => bug!("use of return before def"),
280 LocalRef::Place(cg_place) => OperandRef {
281 val: Ref(cg_place.llval, None, cg_place.align),
282 layout: cg_place.layout,
284 LocalRef::UnsizedPlace(_) => bug!("return type must be sized"),
286 let llslot = match op.val {
287 Immediate(_) | Pair(..) => {
288 let scratch = PlaceRef::alloca(&mut bx, self.fn_abi.ret.layout);
289 op.val.store(&mut bx, scratch);
292 Ref(llval, _, align) => {
293 assert_eq!(align, op.layout.align.abi, "return place is unaligned!");
297 let ty = bx.cast_backend_type(&cast_ty);
298 let addr = bx.pointercast(llslot, bx.type_ptr_to(ty));
299 bx.load(ty, addr, self.fn_abi.ret.layout.align.abi)
305 fn codegen_drop_terminator(
307 helper: TerminatorCodegenHelper<'tcx>,
309 location: mir::Place<'tcx>,
310 target: mir::BasicBlock,
311 unwind: Option<mir::BasicBlock>,
313 let ty = location.ty(self.mir, bx.tcx()).ty;
314 let ty = self.monomorphize(ty);
315 let drop_fn = Instance::resolve_drop_in_place(bx.tcx(), ty);
317 if let ty::InstanceDef::DropGlue(_, None) = drop_fn.def {
318 // we don't actually need to drop anything.
319 helper.funclet_br(self, &mut bx, target);
323 let place = self.codegen_place(&mut bx, location.as_ref());
325 let mut args = if let Some(llextra) = place.llextra {
326 args2 = [place.llval, llextra];
329 args1 = [place.llval];
332 let (drop_fn, fn_abi) = match ty.kind() {
333 // FIXME(eddyb) perhaps move some of this logic into
334 // `Instance::resolve_drop_in_place`?
336 let virtual_drop = Instance {
337 def: ty::InstanceDef::Virtual(drop_fn.def_id(), 0),
338 substs: drop_fn.substs,
340 let fn_abi = FnAbi::of_instance(&bx, virtual_drop, &[]);
341 let vtable = args[1];
344 meth::VirtualIndex::from_index(ty::COMMON_VTABLE_ENTRIES_DROPINPLACE)
345 .get_fn(&mut bx, vtable, &fn_abi),
349 _ => (bx.get_fn_addr(drop_fn), FnAbi::of_instance(&bx, drop_fn, &[])),
357 Some((ReturnDest::Nothing, target)),
362 fn codegen_assert_terminator(
364 helper: TerminatorCodegenHelper<'tcx>,
366 terminator: &mir::Terminator<'tcx>,
367 cond: &mir::Operand<'tcx>,
369 msg: &mir::AssertMessage<'tcx>,
370 target: mir::BasicBlock,
371 cleanup: Option<mir::BasicBlock>,
373 let span = terminator.source_info.span;
374 let cond = self.codegen_operand(&mut bx, cond).immediate();
375 let mut const_cond = bx.const_to_opt_u128(cond, false).map(|c| c == 1);
377 // This case can currently arise only from functions marked
378 // with #[rustc_inherit_overflow_checks] and inlined from
379 // another crate (mostly core::num generic/#[inline] fns),
380 // while the current crate doesn't use overflow checks.
381 // NOTE: Unlike binops, negation doesn't have its own
382 // checked operation, just a comparison with the minimum
383 // value, so we have to check for the assert message.
384 if !bx.check_overflow() {
385 if let AssertKind::OverflowNeg(_) = *msg {
386 const_cond = Some(expected);
390 // Don't codegen the panic block if success if known.
391 if const_cond == Some(expected) {
392 helper.funclet_br(self, &mut bx, target);
396 // Pass the condition through llvm.expect for branch hinting.
397 let cond = bx.expect(cond, expected);
399 // Create the failure block and the conditional branch to it.
400 let lltarget = helper.llblock(self, target);
401 let panic_block = bx.build_sibling_block("panic");
403 bx.cond_br(cond, lltarget, panic_block.llbb());
405 bx.cond_br(cond, panic_block.llbb(), lltarget);
408 // After this point, bx is the block for the call to panic.
410 self.set_debug_loc(&mut bx, terminator.source_info);
412 // Get the location information.
413 let location = self.get_caller_location(&mut bx, terminator.source_info).immediate();
415 // Put together the arguments to the panic entry point.
416 let (lang_item, args) = match msg {
417 AssertKind::BoundsCheck { ref len, ref index } => {
418 let len = self.codegen_operand(&mut bx, len).immediate();
419 let index = self.codegen_operand(&mut bx, index).immediate();
420 // It's `fn panic_bounds_check(index: usize, len: usize)`,
421 // and `#[track_caller]` adds an implicit third argument.
422 (LangItem::PanicBoundsCheck, vec![index, len, location])
425 let msg_str = Symbol::intern(msg.description());
426 let msg = bx.const_str(msg_str);
427 // It's `pub fn panic(expr: &str)`, with the wide reference being passed
428 // as two arguments, and `#[track_caller]` adds an implicit third argument.
429 (LangItem::Panic, vec![msg.0, msg.1, location])
433 // Obtain the panic entry point.
434 let def_id = common::langcall(bx.tcx(), Some(span), "", lang_item);
435 let instance = ty::Instance::mono(bx.tcx(), def_id);
436 let fn_abi = FnAbi::of_instance(&bx, instance, &[]);
437 let llfn = bx.get_fn_addr(instance);
439 // Codegen the actual panic invoke/call.
440 helper.do_call(self, &mut bx, fn_abi, llfn, &args, None, cleanup);
443 /// Returns `true` if this is indeed a panic intrinsic and codegen is done.
444 fn codegen_panic_intrinsic(
446 helper: &TerminatorCodegenHelper<'tcx>,
448 intrinsic: Option<Symbol>,
449 instance: Option<Instance<'tcx>>,
450 source_info: mir::SourceInfo,
451 destination: &Option<(mir::Place<'tcx>, mir::BasicBlock)>,
452 cleanup: Option<mir::BasicBlock>,
454 // Emit a panic or a no-op for `assert_*` intrinsics.
455 // These are intrinsics that compile to panics so that we can get a message
456 // which mentions the offending type, even from a const context.
457 #[derive(Debug, PartialEq)]
458 enum AssertIntrinsic {
463 let panic_intrinsic = intrinsic.and_then(|i| match i {
464 sym::assert_inhabited => Some(AssertIntrinsic::Inhabited),
465 sym::assert_zero_valid => Some(AssertIntrinsic::ZeroValid),
466 sym::assert_uninit_valid => Some(AssertIntrinsic::UninitValid),
469 if let Some(intrinsic) = panic_intrinsic {
470 use AssertIntrinsic::*;
471 let ty = instance.unwrap().substs.type_at(0);
472 let layout = bx.layout_of(ty);
473 let do_panic = match intrinsic {
474 Inhabited => layout.abi.is_uninhabited(),
475 ZeroValid => !layout.might_permit_raw_init(bx, /*zero:*/ true),
476 UninitValid => !layout.might_permit_raw_init(bx, /*zero:*/ false),
479 let msg_str = with_no_trimmed_paths(|| {
480 if layout.abi.is_uninhabited() {
481 // Use this error even for the other intrinsics as it is more precise.
482 format!("attempted to instantiate uninhabited type `{}`", ty)
483 } else if intrinsic == ZeroValid {
484 format!("attempted to zero-initialize type `{}`, which is invalid", ty)
486 format!("attempted to leave type `{}` uninitialized, which is invalid", ty)
489 let msg = bx.const_str(Symbol::intern(&msg_str));
490 let location = self.get_caller_location(bx, source_info).immediate();
492 // Obtain the panic entry point.
493 // FIXME: dedup this with `codegen_assert_terminator` above.
495 common::langcall(bx.tcx(), Some(source_info.span), "", LangItem::Panic);
496 let instance = ty::Instance::mono(bx.tcx(), def_id);
497 let fn_abi = FnAbi::of_instance(bx, instance, &[]);
498 let llfn = bx.get_fn_addr(instance);
500 // Codegen the actual panic invoke/call.
506 &[msg.0, msg.1, location],
507 destination.as_ref().map(|(_, bb)| (ReturnDest::Nothing, *bb)),
512 let target = destination.as_ref().unwrap().1;
513 helper.funclet_br(self, bx, target)
521 fn codegen_call_terminator(
523 helper: TerminatorCodegenHelper<'tcx>,
525 terminator: &mir::Terminator<'tcx>,
526 func: &mir::Operand<'tcx>,
527 args: &[mir::Operand<'tcx>],
528 destination: &Option<(mir::Place<'tcx>, mir::BasicBlock)>,
529 cleanup: Option<mir::BasicBlock>,
532 let source_info = terminator.source_info;
533 let span = source_info.span;
535 // Create the callee. This is a fn ptr or zero-sized and hence a kind of scalar.
536 let callee = self.codegen_operand(&mut bx, func);
538 let (instance, mut llfn) = match *callee.layout.ty.kind() {
539 ty::FnDef(def_id, substs) => (
541 ty::Instance::resolve(bx.tcx(), ty::ParamEnv::reveal_all(), def_id, substs)
544 .polymorphize(bx.tcx()),
548 ty::FnPtr(_) => (None, Some(callee.immediate())),
549 _ => bug!("{} is not callable", callee.layout.ty),
551 let def = instance.map(|i| i.def);
553 if let Some(ty::InstanceDef::DropGlue(_, None)) = def {
554 // Empty drop glue; a no-op.
555 let &(_, target) = destination.as_ref().unwrap();
556 helper.funclet_br(self, &mut bx, target);
560 // FIXME(eddyb) avoid computing this if possible, when `instance` is
561 // available - right now `sig` is only needed for getting the `abi`
562 // and figuring out how many extra args were passed to a C-variadic `fn`.
563 let sig = callee.layout.ty.fn_sig(bx.tcx());
566 // Handle intrinsics old codegen wants Expr's for, ourselves.
567 let intrinsic = match def {
568 Some(ty::InstanceDef::Intrinsic(def_id)) => Some(bx.tcx().item_name(def_id)),
572 let extra_args = &args[sig.inputs().skip_binder().len()..];
573 let extra_args = extra_args
576 let op_ty = op_arg.ty(self.mir, bx.tcx());
577 self.monomorphize(op_ty)
579 .collect::<Vec<_>>();
581 let fn_abi = match instance {
582 Some(instance) => FnAbi::of_instance(&bx, instance, &extra_args),
583 None => FnAbi::of_fn_ptr(&bx, sig, &extra_args),
586 if intrinsic == Some(sym::transmute) {
587 if let Some(destination_ref) = destination.as_ref() {
588 let &(dest, target) = destination_ref;
589 self.codegen_transmute(&mut bx, &args[0], dest);
590 helper.funclet_br(self, &mut bx, target);
592 // If we are trying to transmute to an uninhabited type,
593 // it is likely there is no allotted destination. In fact,
594 // transmuting to an uninhabited type is UB, which means
595 // we can do what we like. Here, we declare that transmuting
596 // into an uninhabited type is impossible, so anything following
597 // it must be unreachable.
598 assert_eq!(fn_abi.ret.layout.abi, abi::Abi::Uninhabited);
604 if self.codegen_panic_intrinsic(
616 // The arguments we'll be passing. Plus one to account for outptr, if used.
617 let arg_count = fn_abi.args.len() + fn_abi.ret.is_indirect() as usize;
618 let mut llargs = Vec::with_capacity(arg_count);
620 // Prepare the return value destination
621 let ret_dest = if let Some((dest, _)) = *destination {
622 let is_intrinsic = intrinsic.is_some();
623 self.make_return_dest(&mut bx, dest, &fn_abi.ret, &mut llargs, is_intrinsic)
628 if intrinsic == Some(sym::caller_location) {
629 if let Some((_, target)) = destination.as_ref() {
631 .get_caller_location(&mut bx, mir::SourceInfo { span: fn_span, ..source_info });
633 if let ReturnDest::IndirectOperand(tmp, _) = ret_dest {
634 location.val.store(&mut bx, tmp);
636 self.store_return(&mut bx, ret_dest, &fn_abi.ret, location.immediate());
637 helper.funclet_br(self, &mut bx, *target);
643 None | Some(sym::drop_in_place) => {}
644 Some(sym::copy_nonoverlapping) => unreachable!(),
646 let dest = match ret_dest {
647 _ if fn_abi.ret.is_indirect() => llargs[0],
648 ReturnDest::Nothing => {
649 bx.const_undef(bx.type_ptr_to(bx.arg_memory_ty(&fn_abi.ret)))
651 ReturnDest::IndirectOperand(dst, _) | ReturnDest::Store(dst) => dst.llval,
652 ReturnDest::DirectOperand(_) => {
653 bug!("Cannot use direct operand with an intrinsic call")
657 let args: Vec<_> = args
661 // The indices passed to simd_shuffle* in the
662 // third argument must be constant. This is
663 // checked by const-qualification, which also
664 // promotes any complex rvalues to constants.
665 if i == 2 && intrinsic.as_str().starts_with("simd_shuffle") {
666 if let mir::Operand::Constant(constant) = arg {
667 let c = self.eval_mir_constant(constant);
669 self.simd_shuffle_indices(&bx, constant.span, constant.ty(), c);
671 val: Immediate(llval),
672 layout: bx.layout_of(ty),
675 span_bug!(span, "shuffle indices must be constant");
679 self.codegen_operand(&mut bx, arg)
683 Self::codegen_intrinsic_call(
685 *instance.as_ref().unwrap(),
692 if let ReturnDest::IndirectOperand(dst, _) = ret_dest {
693 self.store_return(&mut bx, ret_dest, &fn_abi.ret, dst.llval);
696 if let Some((_, target)) = *destination {
697 helper.funclet_br(self, &mut bx, target);
706 // Split the rust-call tupled arguments off.
707 let (first_args, untuple) = if abi == Abi::RustCall && !args.is_empty() {
708 let (tup, args) = args.split_last().unwrap();
714 'make_args: for (i, arg) in first_args.iter().enumerate() {
715 let mut op = self.codegen_operand(&mut bx, arg);
717 if let (0, Some(ty::InstanceDef::Virtual(_, idx))) = (i, def) {
718 if let Pair(..) = op.val {
719 // In the case of Rc<Self>, we need to explicitly pass a
720 // *mut RcBox<Self> with a Scalar (not ScalarPair) ABI. This is a hack
721 // that is understood elsewhere in the compiler as a method on
723 // To get a `*mut RcBox<Self>`, we just keep unwrapping newtypes until
724 // we get a value of a built-in pointer type
725 'descend_newtypes: while !op.layout.ty.is_unsafe_ptr()
726 && !op.layout.ty.is_region_ptr()
728 for i in 0..op.layout.fields.count() {
729 let field = op.extract_field(&mut bx, i);
730 if !field.layout.is_zst() {
731 // we found the one non-zero-sized field that is allowed
732 // now find *its* non-zero-sized field, or stop if it's a
735 continue 'descend_newtypes;
739 span_bug!(span, "receiver has no non-zero-sized fields {:?}", op);
742 // now that we have `*dyn Trait` or `&dyn Trait`, split it up into its
743 // data pointer and vtable. Look up the method in the vtable, and pass
744 // the data pointer as the first argument
746 Pair(data_ptr, meta) => {
748 meth::VirtualIndex::from_index(idx).get_fn(&mut bx, meta, &fn_abi),
750 llargs.push(data_ptr);
753 other => bug!("expected a Pair, got {:?}", other),
755 } else if let Ref(data_ptr, Some(meta), _) = op.val {
756 // by-value dynamic dispatch
757 llfn = Some(meth::VirtualIndex::from_index(idx).get_fn(&mut bx, meta, &fn_abi));
758 llargs.push(data_ptr);
761 span_bug!(span, "can't codegen a virtual call on {:?}", op);
765 // The callee needs to own the argument memory if we pass it
766 // by-ref, so make a local copy of non-immediate constants.
767 match (arg, op.val) {
768 (&mir::Operand::Copy(_), Ref(_, None, _))
769 | (&mir::Operand::Constant(_), Ref(_, None, _)) => {
770 let tmp = PlaceRef::alloca(&mut bx, op.layout);
771 op.val.store(&mut bx, tmp);
772 op.val = Ref(tmp.llval, None, tmp.align);
777 self.codegen_argument(&mut bx, op, &mut llargs, &fn_abi.args[i]);
779 if let Some(tup) = untuple {
780 self.codegen_arguments_untupled(
784 &fn_abi.args[first_args.len()..],
789 instance.map_or(false, |i| i.def.requires_caller_location(self.cx.tcx()));
794 "#[track_caller] fn's must have 1 more argument in their ABI than in their MIR",
797 self.get_caller_location(&mut bx, mir::SourceInfo { span: fn_span, ..source_info });
799 "codegen_call_terminator({:?}): location={:?} (fn_span {:?})",
800 terminator, location, fn_span
803 let last_arg = fn_abi.args.last().unwrap();
804 self.codegen_argument(&mut bx, location, &mut llargs, last_arg);
807 let fn_ptr = match (llfn, instance) {
808 (Some(llfn), _) => llfn,
809 (None, Some(instance)) => bx.get_fn_addr(instance),
810 _ => span_bug!(span, "no llfn for call"),
819 destination.as_ref().map(|&(_, target)| (ret_dest, target)),
824 fn codegen_asm_terminator(
826 helper: TerminatorCodegenHelper<'tcx>,
828 terminator: &mir::Terminator<'tcx>,
829 template: &[ast::InlineAsmTemplatePiece],
830 operands: &[mir::InlineAsmOperand<'tcx>],
831 options: ast::InlineAsmOptions,
833 destination: Option<mir::BasicBlock>,
835 let span = terminator.source_info.span;
837 let operands: Vec<_> = operands
839 .map(|op| match *op {
840 mir::InlineAsmOperand::In { reg, ref value } => {
841 let value = self.codegen_operand(&mut bx, value);
842 InlineAsmOperandRef::In { reg, value }
844 mir::InlineAsmOperand::Out { reg, late, ref place } => {
845 let place = place.map(|place| self.codegen_place(&mut bx, place.as_ref()));
846 InlineAsmOperandRef::Out { reg, late, place }
848 mir::InlineAsmOperand::InOut { reg, late, ref in_value, ref out_place } => {
849 let in_value = self.codegen_operand(&mut bx, in_value);
851 out_place.map(|out_place| self.codegen_place(&mut bx, out_place.as_ref()));
852 InlineAsmOperandRef::InOut { reg, late, in_value, out_place }
854 mir::InlineAsmOperand::Const { ref value } => {
855 let const_value = self
856 .eval_mir_constant(value)
857 .unwrap_or_else(|_| span_bug!(span, "asm const cannot be resolved"));
858 let string = common::asm_const_to_str(
862 bx.layout_of(value.ty()),
864 InlineAsmOperandRef::Const { string }
866 mir::InlineAsmOperand::SymFn { ref value } => {
867 let literal = self.monomorphize(value.literal);
868 if let ty::FnDef(def_id, substs) = *literal.ty().kind() {
869 let instance = ty::Instance::resolve_for_fn_ptr(
871 ty::ParamEnv::reveal_all(),
876 InlineAsmOperandRef::SymFn { instance }
878 span_bug!(span, "invalid type for asm sym (fn)");
881 mir::InlineAsmOperand::SymStatic { def_id } => {
882 InlineAsmOperandRef::SymStatic { def_id }
887 bx.codegen_inline_asm(template, &operands, options, line_spans);
889 if let Some(target) = destination {
890 helper.funclet_br(self, &mut bx, target);
897 impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
898 pub fn codegen_block(&mut self, bb: mir::BasicBlock) {
899 let mut bx = self.build_block(bb);
903 debug!("codegen_block({:?}={:?})", bb, data);
905 for statement in &data.statements {
906 bx = self.codegen_statement(bx, statement);
909 self.codegen_terminator(bx, bb, data.terminator());
912 fn codegen_terminator(
916 terminator: &'tcx mir::Terminator<'tcx>,
918 debug!("codegen_terminator: {:?}", terminator);
920 // Create the cleanup bundle, if needed.
921 let funclet_bb = self.cleanup_kinds[bb].funclet_bb(bb);
922 let helper = TerminatorCodegenHelper { bb, terminator, funclet_bb };
924 self.set_debug_loc(&mut bx, terminator.source_info);
925 match terminator.kind {
926 mir::TerminatorKind::Resume => self.codegen_resume_terminator(helper, bx),
928 mir::TerminatorKind::Abort => {
930 // `abort` does not terminate the block, so we still need to generate
931 // an `unreachable` terminator after it.
935 mir::TerminatorKind::Goto { target } => {
937 // This is an unconditional branch back to this same basic block. That means we
938 // have something like a `loop {}` statement. LLVM versions before 12.0
939 // miscompile this because they assume forward progress. For older versions
940 // try to handle just this specific case which comes up commonly in practice
941 // (e.g., in embedded code).
943 // NB: the `sideeffect` currently checks for the LLVM version used internally.
947 helper.funclet_br(self, &mut bx, target);
950 mir::TerminatorKind::SwitchInt { ref discr, switch_ty, ref targets } => {
951 self.codegen_switchint_terminator(helper, bx, discr, switch_ty, targets);
954 mir::TerminatorKind::Return => {
955 self.codegen_return_terminator(bx);
958 mir::TerminatorKind::Unreachable => {
962 mir::TerminatorKind::Drop { place, target, unwind } => {
963 self.codegen_drop_terminator(helper, bx, place, target, unwind);
966 mir::TerminatorKind::Assert { ref cond, expected, ref msg, target, cleanup } => {
967 self.codegen_assert_terminator(
968 helper, bx, terminator, cond, expected, msg, target, cleanup,
972 mir::TerminatorKind::DropAndReplace { .. } => {
973 bug!("undesugared DropAndReplace in codegen: {:?}", terminator);
976 mir::TerminatorKind::Call {
984 self.codegen_call_terminator(
995 mir::TerminatorKind::GeneratorDrop | mir::TerminatorKind::Yield { .. } => {
996 bug!("generator ops in codegen")
998 mir::TerminatorKind::FalseEdge { .. } | mir::TerminatorKind::FalseUnwind { .. } => {
999 bug!("borrowck false edges in codegen")
1002 mir::TerminatorKind::InlineAsm {
1009 self.codegen_asm_terminator(
1023 fn codegen_argument(
1026 op: OperandRef<'tcx, Bx::Value>,
1027 llargs: &mut Vec<Bx::Value>,
1028 arg: &ArgAbi<'tcx, Ty<'tcx>>,
1030 // Fill padding with undef value, where applicable.
1031 if let Some(ty) = arg.pad {
1032 llargs.push(bx.const_undef(bx.reg_backend_type(&ty)))
1035 if arg.is_ignore() {
1039 if let PassMode::Pair(..) = arg.mode {
1046 _ => bug!("codegen_argument: {:?} invalid for pair argument", op),
1048 } else if arg.is_unsized_indirect() {
1050 Ref(a, Some(b), _) => {
1055 _ => bug!("codegen_argument: {:?} invalid for unsized indirect argument", op),
1059 // Force by-ref if we have to load through a cast pointer.
1060 let (mut llval, align, by_ref) = match op.val {
1061 Immediate(_) | Pair(..) => match arg.mode {
1062 PassMode::Indirect { .. } | PassMode::Cast(_) => {
1063 let scratch = PlaceRef::alloca(bx, arg.layout);
1064 op.val.store(bx, scratch);
1065 (scratch.llval, scratch.align, true)
1067 _ => (op.immediate_or_packed_pair(bx), arg.layout.align.abi, false),
1069 Ref(llval, _, align) => {
1070 if arg.is_indirect() && align < arg.layout.align.abi {
1071 // `foo(packed.large_field)`. We can't pass the (unaligned) field directly. I
1072 // think that ATM (Rust 1.16) we only pass temporaries, but we shouldn't
1073 // have scary latent bugs around.
1075 let scratch = PlaceRef::alloca(bx, arg.layout);
1085 (scratch.llval, scratch.align, true)
1087 (llval, align, true)
1092 if by_ref && !arg.is_indirect() {
1093 // Have to load the argument, maybe while casting it.
1094 if let PassMode::Cast(ty) = arg.mode {
1095 let llty = bx.cast_backend_type(&ty);
1096 let addr = bx.pointercast(llval, bx.type_ptr_to(llty));
1097 llval = bx.load(llty, addr, align.min(arg.layout.align.abi));
1099 // We can't use `PlaceRef::load` here because the argument
1100 // may have a type we don't treat as immediate, but the ABI
1101 // used for this call is passing it by-value. In that case,
1102 // the load would just produce `OperandValue::Ref` instead
1103 // of the `OperandValue::Immediate` we need for the call.
1104 llval = bx.load(bx.backend_type(arg.layout), llval, align);
1105 if let abi::Abi::Scalar(ref scalar) = arg.layout.abi {
1106 if scalar.is_bool() {
1107 bx.range_metadata(llval, 0..2);
1110 // We store bools as `i8` so we need to truncate to `i1`.
1111 llval = bx.to_immediate(llval, arg.layout);
1118 fn codegen_arguments_untupled(
1121 operand: &mir::Operand<'tcx>,
1122 llargs: &mut Vec<Bx::Value>,
1123 args: &[ArgAbi<'tcx, Ty<'tcx>>],
1125 let tuple = self.codegen_operand(bx, operand);
1127 // Handle both by-ref and immediate tuples.
1128 if let Ref(llval, None, align) = tuple.val {
1129 let tuple_ptr = PlaceRef::new_sized_aligned(llval, tuple.layout, align);
1130 for i in 0..tuple.layout.fields.count() {
1131 let field_ptr = tuple_ptr.project_field(bx, i);
1132 let field = bx.load_operand(field_ptr);
1133 self.codegen_argument(bx, field, llargs, &args[i]);
1135 } else if let Ref(_, Some(_), _) = tuple.val {
1136 bug!("closure arguments must be sized")
1138 // If the tuple is immediate, the elements are as well.
1139 for i in 0..tuple.layout.fields.count() {
1140 let op = tuple.extract_field(bx, i);
1141 self.codegen_argument(bx, op, llargs, &args[i]);
1146 fn get_caller_location(
1149 mut source_info: mir::SourceInfo,
1150 ) -> OperandRef<'tcx, Bx::Value> {
1153 let mut span_to_caller_location = |span: Span| {
1154 let topmost = span.ctxt().outer_expn().expansion_cause().unwrap_or(span);
1155 let caller = tcx.sess.source_map().lookup_char_pos(topmost.lo());
1156 let const_loc = tcx.const_caller_location((
1157 Symbol::intern(&caller.file.name.prefer_remapped().to_string_lossy()),
1159 caller.col_display as u32 + 1,
1161 OperandRef::from_const(bx, const_loc, bx.tcx().caller_location_ty())
1164 // Walk up the `SourceScope`s, in case some of them are from MIR inlining.
1165 // If so, the starting `source_info.span` is in the innermost inlined
1166 // function, and will be replaced with outer callsite spans as long
1167 // as the inlined functions were `#[track_caller]`.
1169 let scope_data = &self.mir.source_scopes[source_info.scope];
1171 if let Some((callee, callsite_span)) = scope_data.inlined {
1172 // Stop inside the most nested non-`#[track_caller]` function,
1173 // before ever reaching its caller (which is irrelevant).
1174 if !callee.def.requires_caller_location(tcx) {
1175 return span_to_caller_location(source_info.span);
1177 source_info.span = callsite_span;
1180 // Skip past all of the parents with `inlined: None`.
1181 match scope_data.inlined_parent_scope {
1182 Some(parent) => source_info.scope = parent,
1187 // No inlined `SourceScope`s, or all of them were `#[track_caller]`.
1188 self.caller_location.unwrap_or_else(|| span_to_caller_location(source_info.span))
1191 fn get_personality_slot(&mut self, bx: &mut Bx) -> PlaceRef<'tcx, Bx::Value> {
1193 if let Some(slot) = self.personality_slot {
1196 let layout = cx.layout_of(
1197 cx.tcx().intern_tup(&[cx.tcx().mk_mut_ptr(cx.tcx().types.u8), cx.tcx().types.i32]),
1199 let slot = PlaceRef::alloca(bx, layout);
1200 self.personality_slot = Some(slot);
1205 /// Returns the landing/cleanup pad wrapper around the given basic block.
1206 // FIXME(eddyb) rename this to `eh_pad_for`.
1207 fn landing_pad_for(&mut self, bb: mir::BasicBlock) -> Bx::BasicBlock {
1208 if let Some(landing_pad) = self.landing_pads[bb] {
1212 let landing_pad = self.landing_pad_for_uncached(bb);
1213 self.landing_pads[bb] = Some(landing_pad);
1217 // FIXME(eddyb) rename this to `eh_pad_for_uncached`.
1218 fn landing_pad_for_uncached(&mut self, bb: mir::BasicBlock) -> Bx::BasicBlock {
1219 let llbb = self.llbb(bb);
1220 if base::wants_msvc_seh(self.cx.sess()) {
1223 match self.mir[bb].terminator.as_ref().map(|t| &t.kind) {
1224 // This is a basic block that we're aborting the program for,
1225 // notably in an `extern` function. These basic blocks are inserted
1226 // so that we assert that `extern` functions do indeed not panic,
1227 // and if they do we abort the process.
1229 // On MSVC these are tricky though (where we're doing funclets). If
1230 // we were to do a cleanuppad (like below) the normal functions like
1231 // `longjmp` would trigger the abort logic, terminating the
1232 // program. Instead we insert the equivalent of `catch(...)` for C++
1233 // which magically doesn't trigger when `longjmp` files over this
1236 // Lots more discussion can be found on #48251 but this codegen is
1237 // modeled after clang's for:
1244 Some(&mir::TerminatorKind::Abort) => {
1245 let mut cs_bx = self.new_block(&format!("cs_funclet{:?}", bb));
1246 let mut cp_bx = self.new_block(&format!("cp_funclet{:?}", bb));
1247 ret_llbb = cs_bx.llbb();
1249 let cs = cs_bx.catch_switch(None, None, 1);
1250 cs_bx.add_handler(cs, cp_bx.llbb());
1252 // The "null" here is actually a RTTI type descriptor for the
1253 // C++ personality function, but `catch (...)` has no type so
1254 // it's null. The 64 here is actually a bitfield which
1255 // represents that this is a catch-all block.
1256 let null = cp_bx.const_null(
1257 cp_bx.type_i8p_ext(cp_bx.cx().data_layout().instruction_address_space),
1259 let sixty_four = cp_bx.const_i32(64);
1260 funclet = cp_bx.catch_pad(cs, &[null, sixty_four, null]);
1264 let mut cleanup_bx = self.new_block(&format!("funclet_{:?}", bb));
1265 ret_llbb = cleanup_bx.llbb();
1266 funclet = cleanup_bx.cleanup_pad(None, &[]);
1267 cleanup_bx.br(llbb);
1270 self.funclets[bb] = Some(funclet);
1273 let mut bx = self.new_block("cleanup");
1275 let llpersonality = self.cx.eh_personality();
1276 let llretty = self.landing_pad_type();
1277 let lp = bx.landing_pad(llretty, llpersonality, 1);
1280 let slot = self.get_personality_slot(&mut bx);
1281 slot.storage_live(&mut bx);
1282 Pair(bx.extract_value(lp, 0), bx.extract_value(lp, 1)).store(&mut bx, slot);
1289 fn landing_pad_type(&self) -> Bx::Type {
1291 cx.type_struct(&[cx.type_i8p(), cx.type_i32()], false)
1294 fn unreachable_block(&mut self) -> Bx::BasicBlock {
1295 self.unreachable_block.unwrap_or_else(|| {
1296 let mut bx = self.new_block("unreachable");
1298 self.unreachable_block = Some(bx.llbb());
1303 // FIXME(eddyb) replace with `build_sibling_block`/`append_sibling_block`
1304 // (which requires having a `Bx` already, and not all callers do).
1305 fn new_block(&self, name: &str) -> Bx {
1306 let llbb = Bx::append_block(self.cx, self.llfn, name);
1307 Bx::build(self.cx, llbb)
1310 /// Get the backend `BasicBlock` for a MIR `BasicBlock`, either already
1311 /// cached in `self.cached_llbbs`, or created on demand (and cached).
1312 // FIXME(eddyb) rename `llbb` and other `ll`-prefixed things to use a
1313 // more backend-agnostic prefix such as `cg` (i.e. this would be `cgbb`).
1314 pub fn llbb(&mut self, bb: mir::BasicBlock) -> Bx::BasicBlock {
1315 self.cached_llbbs[bb].unwrap_or_else(|| {
1316 // FIXME(eddyb) only name the block if `fewer_names` is `false`.
1317 let llbb = Bx::append_block(self.cx, self.llfn, &format!("{:?}", bb));
1318 self.cached_llbbs[bb] = Some(llbb);
1323 pub fn build_block(&mut self, bb: mir::BasicBlock) -> Bx {
1324 let llbb = self.llbb(bb);
1325 Bx::build(self.cx, llbb)
1328 fn make_return_dest(
1331 dest: mir::Place<'tcx>,
1332 fn_ret: &ArgAbi<'tcx, Ty<'tcx>>,
1333 llargs: &mut Vec<Bx::Value>,
1335 ) -> ReturnDest<'tcx, Bx::Value> {
1336 // If the return is ignored, we can just return a do-nothing `ReturnDest`.
1337 if fn_ret.is_ignore() {
1338 return ReturnDest::Nothing;
1340 let dest = if let Some(index) = dest.as_local() {
1341 match self.locals[index] {
1342 LocalRef::Place(dest) => dest,
1343 LocalRef::UnsizedPlace(_) => bug!("return type must be sized"),
1344 LocalRef::Operand(None) => {
1345 // Handle temporary places, specifically `Operand` ones, as
1346 // they don't have `alloca`s.
1347 return if fn_ret.is_indirect() {
1348 // Odd, but possible, case, we have an operand temporary,
1349 // but the calling convention has an indirect return.
1350 let tmp = PlaceRef::alloca(bx, fn_ret.layout);
1351 tmp.storage_live(bx);
1352 llargs.push(tmp.llval);
1353 ReturnDest::IndirectOperand(tmp, index)
1354 } else if is_intrinsic {
1355 // Currently, intrinsics always need a location to store
1356 // the result, so we create a temporary `alloca` for the
1358 let tmp = PlaceRef::alloca(bx, fn_ret.layout);
1359 tmp.storage_live(bx);
1360 ReturnDest::IndirectOperand(tmp, index)
1362 ReturnDest::DirectOperand(index)
1365 LocalRef::Operand(Some(_)) => {
1366 bug!("place local already assigned to");
1372 mir::PlaceRef { local: dest.local, projection: &dest.projection },
1375 if fn_ret.is_indirect() {
1376 if dest.align < dest.layout.align.abi {
1377 // Currently, MIR code generation does not create calls
1378 // that store directly to fields of packed structs (in
1379 // fact, the calls it creates write only to temps).
1381 // If someone changes that, please update this code path
1382 // to create a temporary.
1383 span_bug!(self.mir.span, "can't directly store to unaligned value");
1385 llargs.push(dest.llval);
1388 ReturnDest::Store(dest)
1392 fn codegen_transmute(&mut self, bx: &mut Bx, src: &mir::Operand<'tcx>, dst: mir::Place<'tcx>) {
1393 if let Some(index) = dst.as_local() {
1394 match self.locals[index] {
1395 LocalRef::Place(place) => self.codegen_transmute_into(bx, src, place),
1396 LocalRef::UnsizedPlace(_) => bug!("transmute must not involve unsized locals"),
1397 LocalRef::Operand(None) => {
1398 let dst_layout = bx.layout_of(self.monomorphized_place_ty(dst.as_ref()));
1399 assert!(!dst_layout.ty.has_erasable_regions(self.cx.tcx()));
1400 let place = PlaceRef::alloca(bx, dst_layout);
1401 place.storage_live(bx);
1402 self.codegen_transmute_into(bx, src, place);
1403 let op = bx.load_operand(place);
1404 place.storage_dead(bx);
1405 self.locals[index] = LocalRef::Operand(Some(op));
1406 self.debug_introduce_local(bx, index);
1408 LocalRef::Operand(Some(op)) => {
1409 assert!(op.layout.is_zst(), "assigning to initialized SSAtemp");
1413 let dst = self.codegen_place(bx, dst.as_ref());
1414 self.codegen_transmute_into(bx, src, dst);
1418 fn codegen_transmute_into(
1421 src: &mir::Operand<'tcx>,
1422 dst: PlaceRef<'tcx, Bx::Value>,
1424 let src = self.codegen_operand(bx, src);
1426 // Special-case transmutes between scalars as simple bitcasts.
1427 match (&src.layout.abi, &dst.layout.abi) {
1428 (abi::Abi::Scalar(src_scalar), abi::Abi::Scalar(dst_scalar)) => {
1429 // HACK(eddyb) LLVM doesn't like `bitcast`s between pointers and non-pointers.
1430 if (src_scalar.value == abi::Pointer) == (dst_scalar.value == abi::Pointer) {
1431 assert_eq!(src.layout.size, dst.layout.size);
1433 // NOTE(eddyb) the `from_immediate` and `to_immediate_scalar`
1434 // conversions allow handling `bool`s the same as `u8`s.
1435 let src = bx.from_immediate(src.immediate());
1436 let src_as_dst = bx.bitcast(src, bx.backend_type(dst.layout));
1437 Immediate(bx.to_immediate_scalar(src_as_dst, dst_scalar)).store(bx, dst);
1444 let llty = bx.backend_type(src.layout);
1445 let cast_ptr = bx.pointercast(dst.llval, bx.type_ptr_to(llty));
1446 let align = src.layout.align.abi.min(dst.align);
1447 src.val.store(bx, PlaceRef::new_sized_aligned(cast_ptr, src.layout, align));
1450 // Stores the return value of a function call into it's final location.
1454 dest: ReturnDest<'tcx, Bx::Value>,
1455 ret_abi: &ArgAbi<'tcx, Ty<'tcx>>,
1458 use self::ReturnDest::*;
1462 Store(dst) => bx.store_arg(&ret_abi, llval, dst),
1463 IndirectOperand(tmp, index) => {
1464 let op = bx.load_operand(tmp);
1465 tmp.storage_dead(bx);
1466 self.locals[index] = LocalRef::Operand(Some(op));
1467 self.debug_introduce_local(bx, index);
1469 DirectOperand(index) => {
1470 // If there is a cast, we have to store and reload.
1471 let op = if let PassMode::Cast(_) = ret_abi.mode {
1472 let tmp = PlaceRef::alloca(bx, ret_abi.layout);
1473 tmp.storage_live(bx);
1474 bx.store_arg(&ret_abi, llval, tmp);
1475 let op = bx.load_operand(tmp);
1476 tmp.storage_dead(bx);
1479 OperandRef::from_immediate_or_packed_pair(bx, llval, ret_abi.layout)
1481 self.locals[index] = LocalRef::Operand(Some(op));
1482 self.debug_introduce_local(bx, index);
1488 enum ReturnDest<'tcx, V> {
1489 // Do nothing; the return value is indirect or ignored.
1491 // Store the return value to the pointer.
1492 Store(PlaceRef<'tcx, V>),
1493 // Store an indirect return value to an operand local place.
1494 IndirectOperand(PlaceRef<'tcx, V>, mir::Local),
1495 // Store a direct return value to an operand local place.
1496 DirectOperand(mir::Local),