1 //! Inlining pass for MIR functions
2 use crate::deref_separator::deref_finder;
3 use rustc_attr::InlineAttr;
4 use rustc_hir::def_id::DefId;
5 use rustc_index::bit_set::BitSet;
6 use rustc_index::vec::Idx;
7 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
8 use rustc_middle::mir::visit::*;
9 use rustc_middle::mir::*;
10 use rustc_middle::ty::{self, Instance, InstanceDef, ParamEnv, Ty, TyCtxt};
11 use rustc_session::config::OptLevel;
12 use rustc_span::{hygiene::ExpnKind, ExpnData, LocalExpnId, Span};
13 use rustc_target::abi::VariantIdx;
14 use rustc_target::spec::abi::Abi;
16 use crate::simplify::{remove_dead_blocks, CfgSimplifier};
20 use std::ops::{Range, RangeFrom};
24 const INSTR_COST: usize = 5;
25 const CALL_PENALTY: usize = 25;
26 const LANDINGPAD_PENALTY: usize = 50;
27 const RESUME_PENALTY: usize = 45;
29 const UNKNOWN_SIZE_COST: usize = 10;
31 const TOP_DOWN_DEPTH_LIMIT: usize = 5;
35 #[derive(Copy, Clone, Debug)]
36 struct CallSite<'tcx> {
37 callee: Instance<'tcx>,
38 fn_sig: ty::PolyFnSig<'tcx>,
40 target: Option<BasicBlock>,
41 source_info: SourceInfo,
44 impl<'tcx> MirPass<'tcx> for Inline {
45 fn is_enabled(&self, sess: &rustc_session::Session) -> bool {
46 if let Some(enabled) = sess.opts.unstable_opts.inline_mir {
50 match sess.mir_opt_level() {
53 (sess.opts.optimize == OptLevel::Default
54 || sess.opts.optimize == OptLevel::Aggressive)
55 && sess.opts.incremental == None
61 fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
62 let span = trace_span!("inline", body = %tcx.def_path_str(body.source.def_id()));
63 let _guard = span.enter();
64 if inline(tcx, body) {
65 debug!("running simplify cfg on {:?}", body.source);
66 CfgSimplifier::new(body).simplify();
67 remove_dead_blocks(tcx, body);
68 deref_finder(tcx, body);
73 fn inline<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) -> bool {
74 let def_id = body.source.def_id().expect_local();
76 // Only do inlining into fn bodies.
77 if !tcx.hir().body_owner_kind(def_id).is_fn_or_closure() {
80 if body.source.promoted.is_some() {
83 // Avoid inlining into generators, since their `optimized_mir` is used for layout computation,
84 // which can create a cycle, even when no attempt is made to inline the function in the other
86 if body.generator.is_some() {
90 let param_env = tcx.param_env_reveal_all_normalized(def_id);
92 let mut this = Inliner {
95 codegen_fn_attrs: tcx.codegen_fn_attrs(def_id),
99 let blocks = BasicBlock::new(0)..body.basic_blocks.next_index();
100 this.process_blocks(body, blocks);
104 struct Inliner<'tcx> {
106 param_env: ParamEnv<'tcx>,
107 /// Caller codegen attributes.
108 codegen_fn_attrs: &'tcx CodegenFnAttrs,
109 /// Stack of inlined instances.
110 /// We only check the `DefId` and not the substs because we want to
111 /// avoid inlining cases of polymorphic recursion.
112 /// The number of `DefId`s is finite, so checking history is enough
113 /// to ensure that we do not loop endlessly while inlining.
115 /// Indicates that the caller body has been modified.
119 impl<'tcx> Inliner<'tcx> {
120 fn process_blocks(&mut self, caller_body: &mut Body<'tcx>, blocks: Range<BasicBlock>) {
121 // How many callsites in this body are we allowed to inline? We need to limit this in order
122 // to prevent super-linear growth in MIR size
123 let inline_limit = match self.history.len() {
125 1..=TOP_DOWN_DEPTH_LIMIT => 1,
128 let mut inlined_count = 0;
130 let bb_data = &caller_body[bb];
131 if bb_data.is_cleanup {
135 let Some(callsite) = self.resolve_callsite(caller_body, bb, bb_data) else {
139 let span = trace_span!("process_blocks", %callsite.callee, ?bb);
140 let _guard = span.enter();
142 match self.try_inlining(caller_body, &callsite) {
144 debug!("not-inlined {} [{}]", callsite.callee, reason);
148 debug!("inlined {}", callsite.callee);
151 if inlined_count == inline_limit {
154 self.history.push(callsite.callee.def_id());
155 self.process_blocks(caller_body, new_blocks);
162 /// Attempts to inline a callsite into the caller body. When successful returns basic blocks
163 /// containing the inlined body. Otherwise returns an error describing why inlining didn't take
167 caller_body: &mut Body<'tcx>,
168 callsite: &CallSite<'tcx>,
169 ) -> Result<std::ops::Range<BasicBlock>, &'static str> {
170 let callee_attrs = self.tcx.codegen_fn_attrs(callsite.callee.def_id());
171 self.check_codegen_attributes(callsite, callee_attrs)?;
172 self.check_mir_is_available(caller_body, &callsite.callee)?;
173 let callee_body = self.tcx.instance_mir(callsite.callee.def);
174 self.check_mir_body(callsite, callee_body, callee_attrs)?;
176 if !self.tcx.consider_optimizing(|| {
177 format!("Inline {:?} into {:?}", callsite.callee, caller_body.source)
179 return Err("optimization fuel exhausted");
182 let Ok(callee_body) = callsite.callee.try_subst_mir_and_normalize_erasing_regions(
187 return Err("failed to normalize callee body");
190 // Check call signature compatibility.
191 // Normally, this shouldn't be required, but trait normalization failure can create a
193 let terminator = caller_body[callsite.block].terminator.as_ref().unwrap();
194 let TerminatorKind::Call { args, destination, .. } = &terminator.kind else { bug!() };
195 let destination_ty = destination.ty(&caller_body.local_decls, self.tcx).ty;
196 let output_type = callee_body.return_ty();
197 if !util::is_subtype(self.tcx, self.param_env, output_type, destination_ty) {
198 trace!(?output_type, ?destination_ty);
199 return Err("failed to normalize return type");
201 if callsite.fn_sig.abi() == Abi::RustCall {
202 let (arg_tuple, skipped_args) = match &args[..] {
203 [arg_tuple] => (arg_tuple, 0),
204 [_, arg_tuple] => (arg_tuple, 1),
205 _ => bug!("Expected `rust-call` to have 1 or 2 args"),
208 let arg_tuple_ty = arg_tuple.ty(&caller_body.local_decls, self.tcx);
209 let ty::Tuple(arg_tuple_tys) = arg_tuple_ty.kind() else {
210 bug!("Closure arguments are not passed as a tuple");
213 for (arg_ty, input) in
214 arg_tuple_tys.iter().zip(callee_body.args_iter().skip(skipped_args))
216 let input_type = callee_body.local_decls[input].ty;
217 if !util::is_subtype(self.tcx, self.param_env, input_type, arg_ty) {
218 trace!(?arg_ty, ?input_type);
219 return Err("failed to normalize tuple argument type");
223 for (arg, input) in args.iter().zip(callee_body.args_iter()) {
224 let input_type = callee_body.local_decls[input].ty;
225 let arg_ty = arg.ty(&caller_body.local_decls, self.tcx);
226 if !util::is_subtype(self.tcx, self.param_env, input_type, arg_ty) {
227 trace!(?arg_ty, ?input_type);
228 return Err("failed to normalize argument type");
233 let old_blocks = caller_body.basic_blocks.next_index();
234 self.inline_call(caller_body, &callsite, callee_body);
235 let new_blocks = old_blocks..caller_body.basic_blocks.next_index();
240 fn check_mir_is_available(
242 caller_body: &Body<'tcx>,
243 callee: &Instance<'tcx>,
244 ) -> Result<(), &'static str> {
245 let caller_def_id = caller_body.source.def_id();
246 let callee_def_id = callee.def_id();
247 if callee_def_id == caller_def_id {
248 return Err("self-recursion");
252 InstanceDef::Item(_) => {
253 // If there is no MIR available (either because it was not in metadata or
254 // because it has no MIR because it's an extern function), then the inliner
255 // won't cause cycles on this.
256 if !self.tcx.is_mir_available(callee_def_id) {
257 return Err("item MIR unavailable");
260 // These have no own callable MIR.
261 InstanceDef::Intrinsic(_) | InstanceDef::Virtual(..) => {
262 return Err("instance without MIR (intrinsic / virtual)");
264 // This cannot result in an immediate cycle since the callee MIR is a shim, which does
265 // not get any optimizations run on it. Any subsequent inlining may cause cycles, but we
266 // do not need to catch this here, we can wait until the inliner decides to continue
267 // inlining a second time.
268 InstanceDef::VTableShim(_)
269 | InstanceDef::ReifyShim(_)
270 | InstanceDef::FnPtrShim(..)
271 | InstanceDef::ClosureOnceShim { .. }
272 | InstanceDef::DropGlue(..)
273 | InstanceDef::CloneShim(..) => return Ok(()),
276 if self.tcx.is_constructor(callee_def_id) {
277 trace!("constructors always have MIR");
278 // Constructor functions cannot cause a query cycle.
282 if callee_def_id.is_local() {
283 // Avoid a cycle here by only using `instance_mir` only if we have
284 // a lower `DefPathHash` than the callee. This ensures that the callee will
285 // not inline us. This trick even works with incremental compilation,
286 // since `DefPathHash` is stable.
287 if self.tcx.def_path_hash(caller_def_id).local_hash()
288 < self.tcx.def_path_hash(callee_def_id).local_hash()
293 // If we know for sure that the function we're calling will itself try to
294 // call us, then we avoid inlining that function.
295 if self.tcx.mir_callgraph_reachable((*callee, caller_def_id.expect_local())) {
296 return Err("caller might be reachable from callee (query cycle avoidance)");
301 // This cannot result in an immediate cycle since the callee MIR is from another crate
302 // and is already optimized. Any subsequent inlining may cause cycles, but we do
303 // not need to catch this here, we can wait until the inliner decides to continue
304 // inlining a second time.
305 trace!("functions from other crates always have MIR");
312 caller_body: &Body<'tcx>,
314 bb_data: &BasicBlockData<'tcx>,
315 ) -> Option<CallSite<'tcx>> {
316 // Only consider direct calls to functions
317 let terminator = bb_data.terminator();
318 if let TerminatorKind::Call { ref func, target, fn_span, .. } = terminator.kind {
319 let func_ty = func.ty(caller_body, self.tcx);
320 if let ty::FnDef(def_id, substs) = *func_ty.kind() {
321 // To resolve an instance its substs have to be fully normalized.
322 let substs = self.tcx.try_normalize_erasing_regions(self.param_env, substs).ok()?;
324 Instance::resolve(self.tcx, self.param_env, def_id, substs).ok().flatten()?;
326 if let InstanceDef::Virtual(..) | InstanceDef::Intrinsic(_) = callee.def {
330 if self.history.contains(&callee.def_id()) {
334 let fn_sig = self.tcx.bound_fn_sig(def_id).subst(self.tcx, substs);
335 let source_info = SourceInfo { span: fn_span, ..terminator.source_info };
337 return Some(CallSite { callee, fn_sig, block: bb, target, source_info });
344 /// Returns an error if inlining is not possible based on codegen attributes alone. A success
345 /// indicates that inlining decision should be based on other criteria.
346 fn check_codegen_attributes(
348 callsite: &CallSite<'tcx>,
349 callee_attrs: &CodegenFnAttrs,
350 ) -> Result<(), &'static str> {
351 match callee_attrs.inline {
352 InlineAttr::Never => return Err("never inline hint"),
353 InlineAttr::Always | InlineAttr::Hint => {}
354 InlineAttr::None => {
355 if self.tcx.sess.mir_opt_level() <= 2 {
356 return Err("at mir-opt-level=2, only #[inline] is inlined");
361 // Only inline local functions if they would be eligible for cross-crate
362 // inlining. This is to ensure that the final crate doesn't have MIR that
363 // reference unexported symbols
364 if callsite.callee.def_id().is_local() {
365 let is_generic = callsite.callee.substs.non_erasable_generics().next().is_some();
366 if !is_generic && !callee_attrs.requests_inline() {
367 return Err("not exported");
371 if callsite.fn_sig.c_variadic() {
372 return Err("C variadic");
375 if callee_attrs.flags.contains(CodegenFnAttrFlags::COLD) {
379 if callee_attrs.no_sanitize != self.codegen_fn_attrs.no_sanitize {
380 return Err("incompatible sanitizer set");
383 // Two functions are compatible if the callee has no attribute (meaning
384 // that it's codegen agnostic), or sets an attribute that is identical
385 // to this function's attribute.
386 if callee_attrs.instruction_set.is_some()
387 && callee_attrs.instruction_set != self.codegen_fn_attrs.instruction_set
389 return Err("incompatible instruction set");
392 for feature in &callee_attrs.target_features {
393 if !self.codegen_fn_attrs.target_features.contains(feature) {
394 return Err("incompatible target feature");
401 /// Returns inlining decision that is based on the examination of callee MIR body.
402 /// Assumes that codegen attributes have been checked for compatibility already.
403 #[instrument(level = "debug", skip(self, callee_body))]
406 callsite: &CallSite<'tcx>,
407 callee_body: &Body<'tcx>,
408 callee_attrs: &CodegenFnAttrs,
409 ) -> Result<(), &'static str> {
412 let mut threshold = if callee_attrs.requests_inline() {
413 self.tcx.sess.opts.unstable_opts.inline_mir_hint_threshold.unwrap_or(100)
415 self.tcx.sess.opts.unstable_opts.inline_mir_threshold.unwrap_or(50)
418 // Give a bonus functions with a small number of blocks,
419 // We normally have two or three blocks for even
420 // very small functions.
421 if callee_body.basic_blocks.len() <= 3 {
422 threshold += threshold / 4;
424 debug!(" final inline threshold = {}", threshold);
426 // FIXME: Give a bonus to functions with only a single caller
427 let diverges = matches!(
428 callee_body.basic_blocks[START_BLOCK].terminator().kind,
429 TerminatorKind::Unreachable | TerminatorKind::Call { target: None, .. }
431 if diverges && !matches!(callee_attrs.inline, InlineAttr::Always) {
432 return Err("callee diverges unconditionally");
435 let mut checker = CostChecker {
437 param_env: self.param_env,
438 instance: callsite.callee,
444 // Traverse the MIR manually so we can account for the effects of inlining on the CFG.
445 let mut work_list = vec![START_BLOCK];
446 let mut visited = BitSet::new_empty(callee_body.basic_blocks.len());
447 while let Some(bb) = work_list.pop() {
448 if !visited.insert(bb.index()) {
452 let blk = &callee_body.basic_blocks[bb];
453 checker.visit_basic_block_data(bb, blk);
455 let term = blk.terminator();
456 if let TerminatorKind::Drop { ref place, target, unwind }
457 | TerminatorKind::DropAndReplace { ref place, target, unwind, .. } = term.kind
459 work_list.push(target);
461 // If the place doesn't actually need dropping, treat it like a regular goto.
462 let ty = callsite.callee.subst_mir(self.tcx, &place.ty(callee_body, tcx).ty);
463 if ty.needs_drop(tcx, self.param_env) && let Some(unwind) = unwind {
464 work_list.push(unwind);
466 } else if callee_attrs.instruction_set != self.codegen_fn_attrs.instruction_set
467 && matches!(term.kind, TerminatorKind::InlineAsm { .. })
469 // During the attribute checking stage we allow a callee with no
470 // instruction_set assigned to count as compatible with a function that does
471 // assign one. However, during this stage we require an exact match when any
472 // inline-asm is detected. LLVM will still possibly do an inline later on
473 // if the no-attribute function ends up with the same instruction set anyway.
474 return Err("Cannot move inline-asm across instruction sets");
476 work_list.extend(term.successors())
480 // Count up the cost of local variables and temps, if we know the size
481 // use that, otherwise we use a moderately-large dummy cost.
482 for v in callee_body.vars_and_temps_iter() {
483 checker.visit_local_decl(v, &callee_body.local_decls[v]);
486 // Abort if type validation found anything fishy.
489 let cost = checker.cost;
490 if let InlineAttr::Always = callee_attrs.inline {
491 debug!("INLINING {:?} because inline(always) [cost={}]", callsite, cost);
493 } else if cost <= threshold {
494 debug!("INLINING {:?} [cost={} <= threshold={}]", callsite, cost, threshold);
497 debug!("NOT inlining {:?} [cost={} > threshold={}]", callsite, cost, threshold);
498 Err("cost above threshold")
504 caller_body: &mut Body<'tcx>,
505 callsite: &CallSite<'tcx>,
506 mut callee_body: Body<'tcx>,
508 let terminator = caller_body[callsite.block].terminator.take().unwrap();
509 match terminator.kind {
510 TerminatorKind::Call { args, destination, cleanup, .. } => {
511 // If the call is something like `a[*i] = f(i)`, where
512 // `i : &mut usize`, then just duplicating the `a[*i]`
513 // Place could result in two different locations if `f`
514 // writes to `i`. To prevent this we need to create a temporary
515 // borrow of the place and pass the destination as `*temp` instead.
516 fn dest_needs_borrow(place: Place<'_>) -> bool {
517 for elem in place.projection.iter() {
519 ProjectionElem::Deref | ProjectionElem::Index(_) => return true,
527 let dest = if dest_needs_borrow(destination) {
528 trace!("creating temp for return destination");
529 let dest = Rvalue::Ref(
530 self.tcx.lifetimes.re_erased,
531 BorrowKind::Mut { allow_two_phase_borrow: false },
534 let dest_ty = dest.ty(caller_body, self.tcx);
535 let temp = Place::from(self.new_call_temp(caller_body, &callsite, dest_ty));
536 caller_body[callsite.block].statements.push(Statement {
537 source_info: callsite.source_info,
538 kind: StatementKind::Assign(Box::new((temp, dest))),
540 self.tcx.mk_place_deref(temp)
545 // Always create a local to hold the destination, as `RETURN_PLACE` may appear
546 // where a full `Place` is not allowed.
547 let (remap_destination, destination_local) = if let Some(d) = dest.as_local() {
555 destination.ty(caller_body, self.tcx).ty,
560 // Copy the arguments if needed.
561 let args: Vec<_> = self.make_call_args(args, &callsite, caller_body, &callee_body);
563 let mut expn_data = ExpnData::default(
565 callsite.source_info.span,
566 self.tcx.sess.edition(),
570 expn_data.def_site = callee_body.span;
572 self.tcx.with_stable_hashing_context(|hcx| LocalExpnId::fresh(expn_data, hcx));
573 let mut integrator = Integrator {
575 new_locals: Local::new(caller_body.local_decls.len())..,
576 new_scopes: SourceScope::new(caller_body.source_scopes.len())..,
577 new_blocks: BasicBlock::new(caller_body.basic_blocks.len())..,
578 destination: destination_local,
579 callsite_scope: caller_body.source_scopes[callsite.source_info.scope].clone(),
581 cleanup_block: cleanup,
582 in_cleanup_block: false,
585 always_live_locals: BitSet::new_filled(callee_body.local_decls.len()),
588 // Map all `Local`s, `SourceScope`s and `BasicBlock`s to new ones
589 // (or existing ones, in a few special cases) in the caller.
590 integrator.visit_body(&mut callee_body);
592 // If there are any locals without storage markers, give them storage only for the
593 // duration of the call.
594 for local in callee_body.vars_and_temps_iter() {
595 if !callee_body.local_decls[local].internal
596 && integrator.always_live_locals.contains(local)
598 let new_local = integrator.map_local(local);
599 caller_body[callsite.block].statements.push(Statement {
600 source_info: callsite.source_info,
601 kind: StatementKind::StorageLive(new_local),
605 if let Some(block) = callsite.target {
606 // To avoid repeated O(n) insert, push any new statements to the end and rotate
609 if remap_destination {
610 caller_body[block].statements.push(Statement {
611 source_info: callsite.source_info,
612 kind: StatementKind::Assign(Box::new((
614 Rvalue::Use(Operand::Move(destination_local.into())),
619 for local in callee_body.vars_and_temps_iter().rev() {
620 if !callee_body.local_decls[local].internal
621 && integrator.always_live_locals.contains(local)
623 let new_local = integrator.map_local(local);
624 caller_body[block].statements.push(Statement {
625 source_info: callsite.source_info,
626 kind: StatementKind::StorageDead(new_local),
631 caller_body[block].statements.rotate_right(n);
634 // Insert all of the (mapped) parts of the callee body into the caller.
635 caller_body.local_decls.extend(callee_body.drain_vars_and_temps());
636 caller_body.source_scopes.extend(&mut callee_body.source_scopes.drain(..));
637 caller_body.var_debug_info.append(&mut callee_body.var_debug_info);
638 caller_body.basic_blocks_mut().extend(callee_body.basic_blocks_mut().drain(..));
640 caller_body[callsite.block].terminator = Some(Terminator {
641 source_info: callsite.source_info,
642 kind: TerminatorKind::Goto { target: integrator.map_block(START_BLOCK) },
645 // Copy only unevaluated constants from the callee_body into the caller_body.
646 // Although we are only pushing `ConstKind::Unevaluated` consts to
647 // `required_consts`, here we may not only have `ConstKind::Unevaluated`
648 // because we are calling `subst_and_normalize_erasing_regions`.
649 caller_body.required_consts.extend(
650 callee_body.required_consts.iter().copied().filter(|&ct| match ct.literal {
651 ConstantKind::Ty(_) => {
652 bug!("should never encounter ty::UnevaluatedConst in `required_consts`")
654 ConstantKind::Val(..) | ConstantKind::Unevaluated(..) => true,
658 kind => bug!("unexpected terminator kind {:?}", kind),
664 args: Vec<Operand<'tcx>>,
665 callsite: &CallSite<'tcx>,
666 caller_body: &mut Body<'tcx>,
667 callee_body: &Body<'tcx>,
671 // There is a bit of a mismatch between the *caller* of a closure and the *callee*.
672 // The caller provides the arguments wrapped up in a tuple:
674 // tuple_tmp = (a, b, c)
675 // Fn::call(closure_ref, tuple_tmp)
677 // meanwhile the closure body expects the arguments (here, `a`, `b`, and `c`)
678 // as distinct arguments. (This is the "rust-call" ABI hack.) Normally, codegen has
679 // the job of unpacking this tuple. But here, we are codegen. =) So we want to create
682 // [closure_ref, tuple_tmp.0, tuple_tmp.1, tuple_tmp.2]
684 // Except for one tiny wrinkle: we don't actually want `tuple_tmp.0`. It's more convenient
685 // if we "spill" that into *another* temporary, so that we can map the argument
686 // variable in the callee MIR directly to an argument variable on our side.
687 // So we introduce temporaries like:
689 // tmp0 = tuple_tmp.0
690 // tmp1 = tuple_tmp.1
691 // tmp2 = tuple_tmp.2
693 // and the vector is `[closure_ref, tmp0, tmp1, tmp2]`.
694 if callsite.fn_sig.abi() == Abi::RustCall && callee_body.spread_arg.is_none() {
695 let mut args = args.into_iter();
696 let self_ = self.create_temp_if_necessary(args.next().unwrap(), callsite, caller_body);
697 let tuple = self.create_temp_if_necessary(args.next().unwrap(), callsite, caller_body);
698 assert!(args.next().is_none());
700 let tuple = Place::from(tuple);
701 let ty::Tuple(tuple_tys) = tuple.ty(caller_body, tcx).ty.kind() else {
702 bug!("Closure arguments are not passed as a tuple");
705 // The `closure_ref` in our example above.
706 let closure_ref_arg = iter::once(self_);
708 // The `tmp0`, `tmp1`, and `tmp2` in our example above.
709 let tuple_tmp_args = tuple_tys.iter().enumerate().map(|(i, ty)| {
710 // This is e.g., `tuple_tmp.0` in our example above.
711 let tuple_field = Operand::Move(tcx.mk_place_field(tuple, Field::new(i), ty));
713 // Spill to a local to make e.g., `tmp0`.
714 self.create_temp_if_necessary(tuple_field, callsite, caller_body)
717 closure_ref_arg.chain(tuple_tmp_args).collect()
720 .map(|a| self.create_temp_if_necessary(a, callsite, caller_body))
725 /// If `arg` is already a temporary, returns it. Otherwise, introduces a fresh
726 /// temporary `T` and an instruction `T = arg`, and returns `T`.
727 fn create_temp_if_necessary(
730 callsite: &CallSite<'tcx>,
731 caller_body: &mut Body<'tcx>,
733 // Reuse the operand if it is a moved temporary.
734 if let Operand::Move(place) = &arg
735 && let Some(local) = place.as_local()
736 && caller_body.local_kind(local) == LocalKind::Temp
741 // Otherwise, create a temporary for the argument.
742 trace!("creating temp for argument {:?}", arg);
743 let arg_ty = arg.ty(caller_body, self.tcx);
744 let local = self.new_call_temp(caller_body, callsite, arg_ty);
745 caller_body[callsite.block].statements.push(Statement {
746 source_info: callsite.source_info,
747 kind: StatementKind::Assign(Box::new((Place::from(local), Rvalue::Use(arg)))),
752 /// Introduces a new temporary into the caller body that is live for the duration of the call.
755 caller_body: &mut Body<'tcx>,
756 callsite: &CallSite<'tcx>,
759 let local = caller_body.local_decls.push(LocalDecl::new(ty, callsite.source_info.span));
761 caller_body[callsite.block].statements.push(Statement {
762 source_info: callsite.source_info,
763 kind: StatementKind::StorageLive(local),
766 if let Some(block) = callsite.target {
767 caller_body[block].statements.insert(
770 source_info: callsite.source_info,
771 kind: StatementKind::StorageDead(local),
780 fn type_size_of<'tcx>(
782 param_env: ty::ParamEnv<'tcx>,
785 tcx.layout_of(param_env.and(ty)).ok().map(|layout| layout.size.bytes())
788 /// Verify that the callee body is compatible with the caller.
790 /// This visitor mostly computes the inlining cost,
791 /// but also needs to verify that types match because of normalization failure.
792 struct CostChecker<'b, 'tcx> {
794 param_env: ParamEnv<'tcx>,
796 callee_body: &'b Body<'tcx>,
797 instance: ty::Instance<'tcx>,
798 validation: Result<(), &'static str>,
801 impl<'tcx> Visitor<'tcx> for CostChecker<'_, 'tcx> {
802 fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) {
803 // Don't count StorageLive/StorageDead in the inlining cost.
804 match statement.kind {
805 StatementKind::StorageLive(_)
806 | StatementKind::StorageDead(_)
807 | StatementKind::Deinit(_)
808 | StatementKind::Nop => {}
809 _ => self.cost += INSTR_COST,
812 self.super_statement(statement, location);
815 fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location) {
817 match terminator.kind {
818 TerminatorKind::Drop { ref place, unwind, .. }
819 | TerminatorKind::DropAndReplace { ref place, unwind, .. } => {
820 // If the place doesn't actually need dropping, treat it like a regular goto.
821 let ty = self.instance.subst_mir(tcx, &place.ty(self.callee_body, tcx).ty);
822 if ty.needs_drop(tcx, self.param_env) {
823 self.cost += CALL_PENALTY;
824 if unwind.is_some() {
825 self.cost += LANDINGPAD_PENALTY;
828 self.cost += INSTR_COST;
831 TerminatorKind::Call { func: Operand::Constant(ref f), cleanup, .. } => {
832 let fn_ty = self.instance.subst_mir(tcx, &f.literal.ty());
833 self.cost += if let ty::FnDef(def_id, _) = *fn_ty.kind() && tcx.is_intrinsic(def_id) {
834 // Don't give intrinsics the extra penalty for calls
839 if cleanup.is_some() {
840 self.cost += LANDINGPAD_PENALTY;
843 TerminatorKind::Assert { cleanup, .. } => {
844 self.cost += CALL_PENALTY;
845 if cleanup.is_some() {
846 self.cost += LANDINGPAD_PENALTY;
849 TerminatorKind::Resume => self.cost += RESUME_PENALTY,
850 TerminatorKind::InlineAsm { cleanup, .. } => {
851 self.cost += INSTR_COST;
852 if cleanup.is_some() {
853 self.cost += LANDINGPAD_PENALTY;
856 _ => self.cost += INSTR_COST,
859 self.super_terminator(terminator, location);
862 /// Count up the cost of local variables and temps, if we know the size
863 /// use that, otherwise we use a moderately-large dummy cost.
864 fn visit_local_decl(&mut self, local: Local, local_decl: &LocalDecl<'tcx>) {
866 let ptr_size = tcx.data_layout.pointer_size.bytes();
868 let ty = self.instance.subst_mir(tcx, &local_decl.ty);
869 // Cost of the var is the size in machine-words, if we know
871 if let Some(size) = type_size_of(tcx, self.param_env, ty) {
872 self.cost += ((size + ptr_size - 1) / ptr_size) as usize;
874 self.cost += UNKNOWN_SIZE_COST;
877 self.super_local_decl(local, local_decl)
880 /// This method duplicates code from MIR validation in an attempt to detect type mismatches due
881 /// to normalization failure.
882 fn visit_projection_elem(
885 proj_base: &[PlaceElem<'tcx>],
886 elem: PlaceElem<'tcx>,
887 context: PlaceContext,
890 if let ProjectionElem::Field(f, ty) = elem {
891 let parent = Place { local, projection: self.tcx.intern_place_elems(proj_base) };
892 let parent_ty = parent.ty(&self.callee_body.local_decls, self.tcx);
893 let check_equal = |this: &mut Self, f_ty| {
894 if !util::is_equal_up_to_subtyping(this.tcx, this.param_env, ty, f_ty) {
896 this.validation = Err("failed to normalize projection type");
901 let kind = match parent_ty.ty.kind() {
902 &ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => {
903 self.tcx.bound_type_of(def_id).subst(self.tcx, substs).kind()
909 ty::Tuple(fields) => {
910 let Some(f_ty) = fields.get(f.as_usize()) else {
911 self.validation = Err("malformed MIR");
914 check_equal(self, *f_ty);
916 ty::Adt(adt_def, substs) => {
917 let var = parent_ty.variant_index.unwrap_or(VariantIdx::from_u32(0));
918 let Some(field) = adt_def.variant(var).fields.get(f.as_usize()) else {
919 self.validation = Err("malformed MIR");
922 check_equal(self, field.ty(self.tcx, substs));
924 ty::Closure(_, substs) => {
925 let substs = substs.as_closure();
926 let Some(f_ty) = substs.upvar_tys().nth(f.as_usize()) else {
927 self.validation = Err("malformed MIR");
930 check_equal(self, f_ty);
932 &ty::Generator(def_id, substs, _) => {
933 let f_ty = if let Some(var) = parent_ty.variant_index {
934 let gen_body = if def_id == self.callee_body.source.def_id() {
937 self.tcx.optimized_mir(def_id)
940 let Some(layout) = gen_body.generator_layout() else {
941 self.validation = Err("malformed MIR");
945 let Some(&local) = layout.variant_fields[var].get(f) else {
946 self.validation = Err("malformed MIR");
950 let Some(&f_ty) = layout.field_tys.get(local) else {
951 self.validation = Err("malformed MIR");
957 let Some(f_ty) = substs.as_generator().prefix_tys().nth(f.index()) else {
958 self.validation = Err("malformed MIR");
965 check_equal(self, f_ty);
967 _ => self.validation = Err("malformed MIR"),
971 self.super_projection_elem(local, proj_base, elem, context, location);
978 * Integrates blocks from the callee function into the calling function.
979 * Updates block indices, references to locals and other control flow
982 struct Integrator<'a, 'tcx> {
984 new_locals: RangeFrom<Local>,
985 new_scopes: RangeFrom<SourceScope>,
986 new_blocks: RangeFrom<BasicBlock>,
988 callsite_scope: SourceScopeData<'tcx>,
989 callsite: &'a CallSite<'tcx>,
990 cleanup_block: Option<BasicBlock>,
991 in_cleanup_block: bool,
993 expn_data: LocalExpnId,
994 always_live_locals: BitSet<Local>,
997 impl Integrator<'_, '_> {
998 fn map_local(&self, local: Local) -> Local {
999 let new = if local == RETURN_PLACE {
1002 let idx = local.index() - 1;
1003 if idx < self.args.len() {
1006 Local::new(self.new_locals.start.index() + (idx - self.args.len()))
1009 trace!("mapping local `{:?}` to `{:?}`", local, new);
1013 fn map_scope(&self, scope: SourceScope) -> SourceScope {
1014 let new = SourceScope::new(self.new_scopes.start.index() + scope.index());
1015 trace!("mapping scope `{:?}` to `{:?}`", scope, new);
1019 fn map_block(&self, block: BasicBlock) -> BasicBlock {
1020 let new = BasicBlock::new(self.new_blocks.start.index() + block.index());
1021 trace!("mapping block `{:?}` to `{:?}`", block, new);
1025 fn map_unwind(&self, unwind: Option<BasicBlock>) -> Option<BasicBlock> {
1026 if self.in_cleanup_block {
1027 if unwind.is_some() {
1028 bug!("cleanup on cleanup block");
1034 Some(target) => Some(self.map_block(target)),
1035 // Add an unwind edge to the original call's cleanup block
1036 None => self.cleanup_block,
1041 impl<'tcx> MutVisitor<'tcx> for Integrator<'_, 'tcx> {
1042 fn tcx(&self) -> TyCtxt<'tcx> {
1046 fn visit_local(&mut self, local: &mut Local, _ctxt: PlaceContext, _location: Location) {
1047 *local = self.map_local(*local);
1050 fn visit_source_scope_data(&mut self, scope_data: &mut SourceScopeData<'tcx>) {
1051 self.super_source_scope_data(scope_data);
1052 if scope_data.parent_scope.is_none() {
1053 // Attach the outermost callee scope as a child of the callsite
1054 // scope, via the `parent_scope` and `inlined_parent_scope` chains.
1055 scope_data.parent_scope = Some(self.callsite.source_info.scope);
1056 assert_eq!(scope_data.inlined_parent_scope, None);
1057 scope_data.inlined_parent_scope = if self.callsite_scope.inlined.is_some() {
1058 Some(self.callsite.source_info.scope)
1060 self.callsite_scope.inlined_parent_scope
1063 // Mark the outermost callee scope as an inlined one.
1064 assert_eq!(scope_data.inlined, None);
1065 scope_data.inlined = Some((self.callsite.callee, self.callsite.source_info.span));
1066 } else if scope_data.inlined_parent_scope.is_none() {
1067 // Make it easy to find the scope with `inlined` set above.
1068 scope_data.inlined_parent_scope = Some(self.map_scope(OUTERMOST_SOURCE_SCOPE));
1072 fn visit_source_scope(&mut self, scope: &mut SourceScope) {
1073 *scope = self.map_scope(*scope);
1076 fn visit_span(&mut self, span: &mut Span) {
1077 // Make sure that all spans track the fact that they were inlined.
1078 *span = span.fresh_expansion(self.expn_data);
1081 fn visit_basic_block_data(&mut self, block: BasicBlock, data: &mut BasicBlockData<'tcx>) {
1082 self.in_cleanup_block = data.is_cleanup;
1083 self.super_basic_block_data(block, data);
1084 self.in_cleanup_block = false;
1087 fn visit_retag(&mut self, kind: &mut RetagKind, place: &mut Place<'tcx>, loc: Location) {
1088 self.super_retag(kind, place, loc);
1090 // We have to patch all inlined retags to be aware that they are no longer
1091 // happening on function entry.
1092 if *kind == RetagKind::FnEntry {
1093 *kind = RetagKind::Default;
1097 fn visit_statement(&mut self, statement: &mut Statement<'tcx>, location: Location) {
1098 if let StatementKind::StorageLive(local) | StatementKind::StorageDead(local) =
1101 self.always_live_locals.remove(local);
1103 self.super_statement(statement, location);
1106 fn visit_terminator(&mut self, terminator: &mut Terminator<'tcx>, loc: Location) {
1107 // Don't try to modify the implicit `_0` access on return (`return` terminators are
1108 // replaced down below anyways).
1109 if !matches!(terminator.kind, TerminatorKind::Return) {
1110 self.super_terminator(terminator, loc);
1113 match terminator.kind {
1114 TerminatorKind::GeneratorDrop | TerminatorKind::Yield { .. } => bug!(),
1115 TerminatorKind::Goto { ref mut target } => {
1116 *target = self.map_block(*target);
1118 TerminatorKind::SwitchInt { ref mut targets, .. } => {
1119 for tgt in targets.all_targets_mut() {
1120 *tgt = self.map_block(*tgt);
1123 TerminatorKind::Drop { ref mut target, ref mut unwind, .. }
1124 | TerminatorKind::DropAndReplace { ref mut target, ref mut unwind, .. } => {
1125 *target = self.map_block(*target);
1126 *unwind = self.map_unwind(*unwind);
1128 TerminatorKind::Call { ref mut target, ref mut cleanup, .. } => {
1129 if let Some(ref mut tgt) = *target {
1130 *tgt = self.map_block(*tgt);
1132 *cleanup = self.map_unwind(*cleanup);
1134 TerminatorKind::Assert { ref mut target, ref mut cleanup, .. } => {
1135 *target = self.map_block(*target);
1136 *cleanup = self.map_unwind(*cleanup);
1138 TerminatorKind::Return => {
1139 terminator.kind = if let Some(tgt) = self.callsite.target {
1140 TerminatorKind::Goto { target: tgt }
1142 TerminatorKind::Unreachable
1145 TerminatorKind::Resume => {
1146 if let Some(tgt) = self.cleanup_block {
1147 terminator.kind = TerminatorKind::Goto { target: tgt }
1150 TerminatorKind::Abort => {}
1151 TerminatorKind::Unreachable => {}
1152 TerminatorKind::FalseEdge { ref mut real_target, ref mut imaginary_target } => {
1153 *real_target = self.map_block(*real_target);
1154 *imaginary_target = self.map_block(*imaginary_target);
1156 TerminatorKind::FalseUnwind { real_target: _, unwind: _ } =>
1157 // see the ordering of passes in the optimized_mir query.
1159 bug!("False unwinds should have been removed before inlining")
1161 TerminatorKind::InlineAsm { ref mut destination, ref mut cleanup, .. } => {
1162 if let Some(ref mut tgt) = *destination {
1163 *tgt = self.map_block(*tgt);
1165 *cleanup = self.map_unwind(*cleanup);