1 //! MIR datatypes and passes. See the [rustc dev guide] for more info.
3 //! [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/mir/index.html
5 use crate::mir::coverage::{CodeRegion, CoverageKind};
6 use crate::mir::interpret::{ConstAllocation, ConstValue, GlobalAlloc, Scalar};
7 use crate::mir::visit::MirVisitable;
8 use crate::ty::adjustment::PointerCast;
9 use crate::ty::codec::{TyDecoder, TyEncoder};
10 use crate::ty::fold::{FallibleTypeFolder, TypeFoldable, TypeVisitor};
11 use crate::ty::print::{FmtPrinter, Printer};
12 use crate::ty::subst::{GenericArg, InternalSubsts, Subst, SubstsRef};
13 use crate::ty::{self, List, Ty, TyCtxt};
14 use crate::ty::{AdtDef, InstanceDef, Region, ScalarInt, UserTypeAnnotationIndex};
16 use rustc_errors::ErrorGuaranteed;
17 use rustc_hir::def::{CtorKind, Namespace};
18 use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_ID};
19 use rustc_hir::{self, GeneratorKind};
20 use rustc_hir::{self as hir, HirId};
21 use rustc_session::Session;
22 use rustc_target::abi::{Size, VariantIdx};
24 use polonius_engine::Atom;
25 pub use rustc_ast::Mutability;
26 use rustc_data_structures::fx::FxHashSet;
27 use rustc_data_structures::graph::dominators::{dominators, Dominators};
28 use rustc_data_structures::graph::{self, GraphSuccessors};
29 use rustc_index::bit_set::BitMatrix;
30 use rustc_index::vec::{Idx, IndexVec};
31 use rustc_serialize::{Decodable, Encodable};
32 use rustc_span::symbol::Symbol;
33 use rustc_span::{Span, DUMMY_SP};
34 use rustc_target::asm::InlineAsmRegOrRegClass;
39 use std::convert::TryInto;
40 use std::fmt::{self, Debug, Display, Formatter, Write};
41 use std::ops::{ControlFlow, Index, IndexMut};
43 use std::{iter, mem, option};
45 use self::graph_cyclic_cache::GraphIsCyclicCache;
46 use self::predecessors::{PredecessorCache, Predecessors};
47 pub use self::query::*;
48 use self::switch_sources::{SwitchSourceCache, SwitchSources};
52 pub mod generic_graphviz;
53 mod graph_cyclic_cache;
65 pub use terminator::*;
70 pub use self::generic_graph::graphviz_safe_def_name;
71 pub use self::graphviz::write_mir_graphviz;
72 pub use self::pretty::{
73 create_dump_file, display_allocation, dump_enabled, dump_mir, write_mir_pretty, PassWhere,
77 pub type LocalDecls<'tcx> = IndexVec<Local, LocalDecl<'tcx>>;
79 pub trait HasLocalDecls<'tcx> {
80 fn local_decls(&self) -> &LocalDecls<'tcx>;
83 impl<'tcx> HasLocalDecls<'tcx> for LocalDecls<'tcx> {
85 fn local_decls(&self) -> &LocalDecls<'tcx> {
90 impl<'tcx> HasLocalDecls<'tcx> for Body<'tcx> {
92 fn local_decls(&self) -> &LocalDecls<'tcx> {
97 /// A streamlined trait that you can implement to create a pass; the
98 /// pass will be named after the type, and it will consist of a main
99 /// loop that goes over each available MIR and applies `run_pass`.
100 pub trait MirPass<'tcx> {
101 fn name(&self) -> Cow<'_, str> {
102 let name = std::any::type_name::<Self>();
103 if let Some(tail) = name.rfind(':') {
104 Cow::from(&name[tail + 1..])
110 /// Returns `true` if this pass is enabled with the current combination of compiler flags.
111 fn is_enabled(&self, _sess: &Session) -> bool {
115 fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>);
117 /// If this pass causes the MIR to enter a new phase, return that phase.
118 fn phase_change(&self) -> Option<MirPhase> {
122 fn is_mir_dump_enabled(&self) -> bool {
127 /// The various "big phases" that MIR goes through.
129 /// These phases all describe dialects of MIR. Since all MIR uses the same datastructures, the
130 /// dialects forbid certain variants or values in certain phases. The sections below summarize the
131 /// changes, but do not document them thoroughly. The full documentation is found in the appropriate
132 /// documentation for the thing the change is affecting.
134 /// Warning: ordering of variants is significant.
135 #[derive(Copy, Clone, TyEncodable, TyDecodable, Debug, PartialEq, Eq, PartialOrd, Ord)]
136 #[derive(HashStable)]
138 /// The dialect of MIR used during all phases before `DropsLowered` is the same. This is also
139 /// the MIR that analysis such as borrowck uses.
141 /// One important thing to remember about the behavior of this section of MIR is that drop terminators
142 /// (including drop and replace) are *conditional*. The elaborate drops pass will then replace each
143 /// instance of a drop terminator with a nop, an unconditional drop, or a drop conditioned on a drop
144 /// flag. Of course, this means that it is important that the drop elaboration can accurately recognize
145 /// when things are initialized and when things are de-initialized. That means any code running on this
146 /// version of MIR must be sure to produce output that drop elaboration can reason about. See the
147 /// section on the drop terminatorss for more details.
149 // FIXME(oli-obk): it's unclear whether we still need this phase (and its corresponding query).
150 // We used to have this for pre-miri MIR based const eval.
152 /// This phase checks the MIR for promotable elements and takes them out of the main MIR body
153 /// by creating a new MIR body per promoted element. After this phase (and thus the termination
154 /// of the `mir_promoted` query), these promoted elements are available in the `promoted_mir`
157 /// Beginning with this phase, the following variants are disallowed:
158 /// * [`TerminatorKind::DropAndReplace`](terminator::TerminatorKind::DropAndReplace)
159 /// * [`TerminatorKind::FalseUnwind`](terminator::TerminatorKind::FalseUnwind)
160 /// * [`TerminatorKind::FalseEdge`](terminator::TerminatorKind::FalseEdge)
161 /// * [`StatementKind::FakeRead`]
162 /// * [`StatementKind::AscribeUserType`]
163 /// * [`Rvalue::Ref`] with `BorrowKind::Shallow`
165 /// And the following variant is allowed:
166 /// * [`StatementKind::Retag`]
168 /// Furthermore, `Drop` now uses explicit drop flags visible in the MIR and reaching a `Drop`
169 /// terminator means that the auto-generated drop glue will be invoked. Also, `Copy` operands
170 /// are allowed for non-`Copy` types.
172 /// Beginning with this phase, the following variant is disallowed:
173 /// * [`Rvalue::Aggregate`] for any `AggregateKind` except `Array`
175 /// And the following variant is allowed:
176 /// * [`StatementKind::SetDiscriminant`]
178 /// Before this phase, generators are in the "source code" form, featuring `yield` statements
179 /// and such. With this phase change, they are transformed into a proper state machine. Running
180 /// optimizations before this change can be potentially dangerous because the source code is to
181 /// some extent a "lie." In particular, `yield` terminators effectively make the value of all
182 /// locals visible to the caller. This means that dead store elimination before them, or code
183 /// motion across them, is not correct in general. This is also exasperated by type checking
184 /// having pre-computed a list of the types that it thinks are ok to be live across a yield
185 /// point - this is necessary to decide eg whether autotraits are implemented. Introducing new
186 /// types across a yield point will lead to ICEs becaues of this.
188 /// Beginning with this phase, the following variants are disallowed:
189 /// * [`TerminatorKind::Yield`](terminator::TerminatorKind::Yield)
190 /// * [`TerminatorKind::GeneratorDrop](terminator::TerminatorKind::GeneratorDrop)
191 GeneratorsLowered = 5,
196 /// Gets the index of the current MirPhase within the set of all `MirPhase`s.
197 pub fn phase_index(&self) -> usize {
202 /// Where a specific `mir::Body` comes from.
203 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
204 #[derive(HashStable, TyEncodable, TyDecodable, TypeFoldable)]
205 pub struct MirSource<'tcx> {
206 pub instance: InstanceDef<'tcx>,
208 /// If `Some`, this is a promoted rvalue within the parent function.
209 pub promoted: Option<Promoted>,
212 impl<'tcx> MirSource<'tcx> {
213 pub fn item(def_id: DefId) -> Self {
215 instance: InstanceDef::Item(ty::WithOptConstParam::unknown(def_id)),
220 pub fn from_instance(instance: InstanceDef<'tcx>) -> Self {
221 MirSource { instance, promoted: None }
224 pub fn with_opt_param(self) -> ty::WithOptConstParam<DefId> {
225 self.instance.with_opt_param()
229 pub fn def_id(&self) -> DefId {
230 self.instance.def_id()
234 #[derive(Clone, TyEncodable, TyDecodable, Debug, HashStable, TypeFoldable)]
235 pub struct GeneratorInfo<'tcx> {
236 /// The yield type of the function, if it is a generator.
237 pub yield_ty: Option<Ty<'tcx>>,
239 /// Generator drop glue.
240 pub generator_drop: Option<Body<'tcx>>,
242 /// The layout of a generator. Produced by the state transformation.
243 pub generator_layout: Option<GeneratorLayout<'tcx>>,
245 /// If this is a generator then record the type of source expression that caused this generator
247 pub generator_kind: GeneratorKind,
250 /// The lowered representation of a single function.
251 #[derive(Clone, TyEncodable, TyDecodable, Debug, HashStable, TypeFoldable)]
252 pub struct Body<'tcx> {
253 /// A list of basic blocks. References to basic block use a newtyped index type [`BasicBlock`]
254 /// that indexes into this vector.
255 basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,
257 /// Records how far through the "desugaring and optimization" process this particular
258 /// MIR has traversed. This is particularly useful when inlining, since in that context
259 /// we instantiate the promoted constants and add them to our promoted vector -- but those
260 /// promoted items have already been optimized, whereas ours have not. This field allows
261 /// us to see the difference and forego optimization on the inlined promoted items.
264 pub source: MirSource<'tcx>,
266 /// A list of source scopes; these are referenced by statements
267 /// and used for debuginfo. Indexed by a `SourceScope`.
268 pub source_scopes: IndexVec<SourceScope, SourceScopeData<'tcx>>,
270 pub generator: Option<Box<GeneratorInfo<'tcx>>>,
272 /// Declarations of locals.
274 /// The first local is the return value pointer, followed by `arg_count`
275 /// locals for the function arguments, followed by any user-declared
276 /// variables and temporaries.
277 pub local_decls: LocalDecls<'tcx>,
279 /// User type annotations.
280 pub user_type_annotations: ty::CanonicalUserTypeAnnotations<'tcx>,
282 /// The number of arguments this function takes.
284 /// Starting at local 1, `arg_count` locals will be provided by the caller
285 /// and can be assumed to be initialized.
287 /// If this MIR was built for a constant, this will be 0.
288 pub arg_count: usize,
290 /// Mark an argument local (which must be a tuple) as getting passed as
291 /// its individual components at the LLVM level.
293 /// This is used for the "rust-call" ABI.
294 pub spread_arg: Option<Local>,
296 /// Debug information pertaining to user variables, including captures.
297 pub var_debug_info: Vec<VarDebugInfo<'tcx>>,
299 /// A span representing this MIR, for error reporting.
302 /// Constants that are required to evaluate successfully for this MIR to be well-formed.
303 /// We hold in this field all the constants we are not able to evaluate yet.
304 pub required_consts: Vec<Constant<'tcx>>,
306 /// Does this body use generic parameters. This is used for the `ConstEvaluatable` check.
308 /// Note that this does not actually mean that this body is not computable right now.
309 /// The repeat count in the following example is polymorphic, but can still be evaluated
310 /// without knowing anything about the type parameter `T`.
314 /// let _ = [0; std::mem::size_of::<*mut T>()];
318 /// **WARNING**: Do not change this flags after the MIR was originally created, even if an optimization
319 /// removed the last mention of all generic params. We do not want to rely on optimizations and
320 /// potentially allow things like `[u8; std::mem::size_of::<T>() * 0]` due to this.
321 pub is_polymorphic: bool,
323 predecessor_cache: PredecessorCache,
324 switch_source_cache: SwitchSourceCache,
325 is_cyclic: GraphIsCyclicCache,
327 pub tainted_by_errors: Option<ErrorGuaranteed>,
330 impl<'tcx> Body<'tcx> {
332 source: MirSource<'tcx>,
333 basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,
334 source_scopes: IndexVec<SourceScope, SourceScopeData<'tcx>>,
335 local_decls: LocalDecls<'tcx>,
336 user_type_annotations: ty::CanonicalUserTypeAnnotations<'tcx>,
338 var_debug_info: Vec<VarDebugInfo<'tcx>>,
340 generator_kind: Option<GeneratorKind>,
341 tainted_by_errors: Option<ErrorGuaranteed>,
343 // We need `arg_count` locals, and one for the return place.
345 local_decls.len() > arg_count,
346 "expected at least {} locals, got {}",
351 let mut body = Body {
352 phase: MirPhase::Built,
356 generator: generator_kind.map(|generator_kind| {
357 Box::new(GeneratorInfo {
359 generator_drop: None,
360 generator_layout: None,
365 user_type_annotations,
370 required_consts: Vec::new(),
371 is_polymorphic: false,
372 predecessor_cache: PredecessorCache::new(),
373 switch_source_cache: SwitchSourceCache::new(),
374 is_cyclic: GraphIsCyclicCache::new(),
377 body.is_polymorphic = body.has_param_types_or_consts();
381 /// Returns a partially initialized MIR body containing only a list of basic blocks.
383 /// The returned MIR contains no `LocalDecl`s (even for the return place) or source scopes. It
384 /// is only useful for testing but cannot be `#[cfg(test)]` because it is used in a different
386 pub fn new_cfg_only(basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>) -> Self {
387 let mut body = Body {
388 phase: MirPhase::Built,
389 source: MirSource::item(CRATE_DEF_ID.to_def_id()),
391 source_scopes: IndexVec::new(),
393 local_decls: IndexVec::new(),
394 user_type_annotations: IndexVec::new(),
398 required_consts: Vec::new(),
399 var_debug_info: Vec::new(),
400 is_polymorphic: false,
401 predecessor_cache: PredecessorCache::new(),
402 switch_source_cache: SwitchSourceCache::new(),
403 is_cyclic: GraphIsCyclicCache::new(),
404 tainted_by_errors: None,
406 body.is_polymorphic = body.has_param_types_or_consts();
411 pub fn basic_blocks(&self) -> &IndexVec<BasicBlock, BasicBlockData<'tcx>> {
416 pub fn basic_blocks_mut(&mut self) -> &mut IndexVec<BasicBlock, BasicBlockData<'tcx>> {
417 // Because the user could mutate basic block terminators via this reference, we need to
418 // invalidate the caches.
420 // FIXME: Use a finer-grained API for this, so only transformations that alter terminators
421 // invalidate the caches.
422 self.predecessor_cache.invalidate();
423 self.switch_source_cache.invalidate();
424 self.is_cyclic.invalidate();
425 &mut self.basic_blocks
429 pub fn basic_blocks_and_local_decls_mut(
431 ) -> (&mut IndexVec<BasicBlock, BasicBlockData<'tcx>>, &mut LocalDecls<'tcx>) {
432 self.predecessor_cache.invalidate();
433 self.switch_source_cache.invalidate();
434 self.is_cyclic.invalidate();
435 (&mut self.basic_blocks, &mut self.local_decls)
439 pub fn basic_blocks_local_decls_mut_and_var_debug_info(
442 &mut IndexVec<BasicBlock, BasicBlockData<'tcx>>,
443 &mut LocalDecls<'tcx>,
444 &mut Vec<VarDebugInfo<'tcx>>,
446 self.predecessor_cache.invalidate();
447 self.switch_source_cache.invalidate();
448 self.is_cyclic.invalidate();
449 (&mut self.basic_blocks, &mut self.local_decls, &mut self.var_debug_info)
452 /// Returns `true` if a cycle exists in the control-flow graph that is reachable from the
454 pub fn is_cfg_cyclic(&self) -> bool {
455 self.is_cyclic.is_cyclic(self)
459 pub fn local_kind(&self, local: Local) -> LocalKind {
460 let index = local.as_usize();
463 self.local_decls[local].mutability == Mutability::Mut,
464 "return place should be mutable"
467 LocalKind::ReturnPointer
468 } else if index < self.arg_count + 1 {
470 } else if self.local_decls[local].is_user_variable() {
477 /// Returns an iterator over all user-declared mutable locals.
479 pub fn mut_vars_iter<'a>(&'a self) -> impl Iterator<Item = Local> + 'a {
480 (self.arg_count + 1..self.local_decls.len()).filter_map(move |index| {
481 let local = Local::new(index);
482 let decl = &self.local_decls[local];
483 if decl.is_user_variable() && decl.mutability == Mutability::Mut {
491 /// Returns an iterator over all user-declared mutable arguments and locals.
493 pub fn mut_vars_and_args_iter<'a>(&'a self) -> impl Iterator<Item = Local> + 'a {
494 (1..self.local_decls.len()).filter_map(move |index| {
495 let local = Local::new(index);
496 let decl = &self.local_decls[local];
497 if (decl.is_user_variable() || index < self.arg_count + 1)
498 && decl.mutability == Mutability::Mut
507 /// Returns an iterator over all function arguments.
509 pub fn args_iter(&self) -> impl Iterator<Item = Local> + ExactSizeIterator {
510 (1..self.arg_count + 1).map(Local::new)
513 /// Returns an iterator over all user-defined variables and compiler-generated temporaries (all
514 /// locals that are neither arguments nor the return place).
516 pub fn vars_and_temps_iter(
518 ) -> impl DoubleEndedIterator<Item = Local> + ExactSizeIterator {
519 (self.arg_count + 1..self.local_decls.len()).map(Local::new)
523 pub fn drain_vars_and_temps<'a>(&'a mut self) -> impl Iterator<Item = LocalDecl<'tcx>> + 'a {
524 self.local_decls.drain(self.arg_count + 1..)
527 /// Changes a statement to a nop. This is both faster than deleting instructions and avoids
528 /// invalidating statement indices in `Location`s.
529 pub fn make_statement_nop(&mut self, location: Location) {
530 let block = &mut self.basic_blocks[location.block];
531 debug_assert!(location.statement_index < block.statements.len());
532 block.statements[location.statement_index].make_nop()
535 /// Returns the source info associated with `location`.
536 pub fn source_info(&self, location: Location) -> &SourceInfo {
537 let block = &self[location.block];
538 let stmts = &block.statements;
539 let idx = location.statement_index;
540 if idx < stmts.len() {
541 &stmts[idx].source_info
543 assert_eq!(idx, stmts.len());
544 &block.terminator().source_info
548 /// Returns the return type; it always return first element from `local_decls` array.
550 pub fn return_ty(&self) -> Ty<'tcx> {
551 self.local_decls[RETURN_PLACE].ty
554 /// Gets the location of the terminator for the given block.
556 pub fn terminator_loc(&self, bb: BasicBlock) -> Location {
557 Location { block: bb, statement_index: self[bb].statements.len() }
560 pub fn stmt_at(&self, location: Location) -> Either<&Statement<'tcx>, &Terminator<'tcx>> {
561 let Location { block, statement_index } = location;
562 let block_data = &self.basic_blocks[block];
565 .get(statement_index)
567 .unwrap_or_else(|| Either::Right(block_data.terminator()))
571 pub fn predecessors(&self) -> &Predecessors {
572 self.predecessor_cache.compute(&self.basic_blocks)
576 pub fn switch_sources(&self) -> &SwitchSources {
577 self.switch_source_cache.compute(&self.basic_blocks)
581 pub fn dominators(&self) -> Dominators<BasicBlock> {
586 pub fn yield_ty(&self) -> Option<Ty<'tcx>> {
587 self.generator.as_ref().and_then(|generator| generator.yield_ty)
591 pub fn generator_layout(&self) -> Option<&GeneratorLayout<'tcx>> {
592 self.generator.as_ref().and_then(|generator| generator.generator_layout.as_ref())
596 pub fn generator_drop(&self) -> Option<&Body<'tcx>> {
597 self.generator.as_ref().and_then(|generator| generator.generator_drop.as_ref())
601 pub fn generator_kind(&self) -> Option<GeneratorKind> {
602 self.generator.as_ref().map(|generator| generator.generator_kind)
606 #[derive(Copy, Clone, PartialEq, Eq, Debug, TyEncodable, TyDecodable, HashStable)]
609 /// Unsafe because of compiler-generated unsafe code, like `await` desugaring
611 /// Unsafe because of an unsafe fn
613 /// Unsafe because of an `unsafe` block
614 ExplicitUnsafe(hir::HirId),
617 impl<'tcx> Index<BasicBlock> for Body<'tcx> {
618 type Output = BasicBlockData<'tcx>;
621 fn index(&self, index: BasicBlock) -> &BasicBlockData<'tcx> {
622 &self.basic_blocks()[index]
626 impl<'tcx> IndexMut<BasicBlock> for Body<'tcx> {
628 fn index_mut(&mut self, index: BasicBlock) -> &mut BasicBlockData<'tcx> {
629 &mut self.basic_blocks_mut()[index]
633 #[derive(Copy, Clone, Debug, HashStable, TypeFoldable)]
634 pub enum ClearCrossCrate<T> {
639 impl<T> ClearCrossCrate<T> {
640 pub fn as_ref(&self) -> ClearCrossCrate<&T> {
642 ClearCrossCrate::Clear => ClearCrossCrate::Clear,
643 ClearCrossCrate::Set(v) => ClearCrossCrate::Set(v),
647 pub fn assert_crate_local(self) -> T {
649 ClearCrossCrate::Clear => bug!("unwrapping cross-crate data"),
650 ClearCrossCrate::Set(v) => v,
655 const TAG_CLEAR_CROSS_CRATE_CLEAR: u8 = 0;
656 const TAG_CLEAR_CROSS_CRATE_SET: u8 = 1;
658 impl<'tcx, E: TyEncoder<'tcx>, T: Encodable<E>> Encodable<E> for ClearCrossCrate<T> {
660 fn encode(&self, e: &mut E) -> Result<(), E::Error> {
661 if E::CLEAR_CROSS_CRATE {
666 ClearCrossCrate::Clear => TAG_CLEAR_CROSS_CRATE_CLEAR.encode(e),
667 ClearCrossCrate::Set(ref val) => {
668 TAG_CLEAR_CROSS_CRATE_SET.encode(e)?;
674 impl<'tcx, D: TyDecoder<'tcx>, T: Decodable<D>> Decodable<D> for ClearCrossCrate<T> {
676 fn decode(d: &mut D) -> ClearCrossCrate<T> {
677 if D::CLEAR_CROSS_CRATE {
678 return ClearCrossCrate::Clear;
681 let discr = u8::decode(d);
684 TAG_CLEAR_CROSS_CRATE_CLEAR => ClearCrossCrate::Clear,
685 TAG_CLEAR_CROSS_CRATE_SET => {
686 let val = T::decode(d);
687 ClearCrossCrate::Set(val)
689 tag => panic!("Invalid tag for ClearCrossCrate: {:?}", tag),
694 /// Grouped information about the source code origin of a MIR entity.
695 /// Intended to be inspected by diagnostics and debuginfo.
696 /// Most passes can work with it as a whole, within a single function.
697 // The unofficial Cranelift backend, at least as of #65828, needs `SourceInfo` to implement `Eq` and
698 // `Hash`. Please ping @bjorn3 if removing them.
699 #[derive(Copy, Clone, Debug, Eq, PartialEq, TyEncodable, TyDecodable, Hash, HashStable)]
700 pub struct SourceInfo {
701 /// The source span for the AST pertaining to this MIR entity.
704 /// The source scope, keeping track of which bindings can be
705 /// seen by debuginfo, active lint levels, `unsafe {...}`, etc.
706 pub scope: SourceScope,
711 pub fn outermost(span: Span) -> Self {
712 SourceInfo { span, scope: OUTERMOST_SOURCE_SCOPE }
716 ///////////////////////////////////////////////////////////////////////////
719 #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, TyEncodable, TyDecodable)]
720 #[derive(Hash, HashStable)]
721 pub enum BorrowKind {
722 /// Data must be immutable and is aliasable.
725 /// The immediately borrowed place must be immutable, but projections from
726 /// it don't need to be. For example, a shallow borrow of `a.b` doesn't
727 /// conflict with a mutable borrow of `a.b.c`.
729 /// This is used when lowering matches: when matching on a place we want to
730 /// ensure that place have the same value from the start of the match until
731 /// an arm is selected. This prevents this code from compiling:
733 /// let mut x = &Some(0);
736 /// Some(_) if { x = &None; false } => (),
740 /// This can't be a shared borrow because mutably borrowing (*x as Some).0
741 /// should not prevent `if let None = x { ... }`, for example, because the
742 /// mutating `(*x as Some).0` can't affect the discriminant of `x`.
743 /// We can also report errors with this kind of borrow differently.
746 /// Data must be immutable but not aliasable. This kind of borrow
747 /// cannot currently be expressed by the user and is used only in
748 /// implicit closure bindings. It is needed when the closure is
749 /// borrowing or mutating a mutable referent, e.g.:
751 /// let x: &mut isize = ...;
752 /// let y = || *x += 5;
754 /// If we were to try to translate this closure into a more explicit
755 /// form, we'd encounter an error with the code as written:
757 /// struct Env { x: & &mut isize }
758 /// let x: &mut isize = ...;
759 /// let y = (&mut Env { &x }, fn_ptr); // Closure is pair of env and fn
760 /// fn fn_ptr(env: &mut Env) { **env.x += 5; }
762 /// This is then illegal because you cannot mutate an `&mut` found
763 /// in an aliasable location. To solve, you'd have to translate with
764 /// an `&mut` borrow:
766 /// struct Env { x: &mut &mut isize }
767 /// let x: &mut isize = ...;
768 /// let y = (&mut Env { &mut x }, fn_ptr); // changed from &x to &mut x
769 /// fn fn_ptr(env: &mut Env) { **env.x += 5; }
771 /// Now the assignment to `**env.x` is legal, but creating a
772 /// mutable pointer to `x` is not because `x` is not mutable. We
773 /// could fix this by declaring `x` as `let mut x`. This is ok in
774 /// user code, if awkward, but extra weird for closures, since the
775 /// borrow is hidden.
777 /// So we introduce a "unique imm" borrow -- the referent is
778 /// immutable, but not aliasable. This solves the problem. For
779 /// simplicity, we don't give users the way to express this
780 /// borrow, it's just used when translating closures.
783 /// Data is mutable and not aliasable.
785 /// `true` if this borrow arose from method-call auto-ref
786 /// (i.e., `adjustment::Adjust::Borrow`).
787 allow_two_phase_borrow: bool,
792 pub fn allows_two_phase_borrow(&self) -> bool {
794 BorrowKind::Shared | BorrowKind::Shallow | BorrowKind::Unique => false,
795 BorrowKind::Mut { allow_two_phase_borrow } => allow_two_phase_borrow,
799 pub fn describe_mutability(&self) -> String {
801 BorrowKind::Shared | BorrowKind::Shallow | BorrowKind::Unique => {
802 "immutable".to_string()
804 BorrowKind::Mut { .. } => "mutable".to_string(),
809 ///////////////////////////////////////////////////////////////////////////
810 // Variables and temps
812 rustc_index::newtype_index! {
815 DEBUG_FORMAT = "_{}",
816 const RETURN_PLACE = 0,
820 impl Atom for Local {
821 fn index(self) -> usize {
826 /// Classifies locals into categories. See `Body::local_kind`.
827 #[derive(Clone, Copy, PartialEq, Eq, Debug, HashStable)]
829 /// User-declared variable binding.
831 /// Compiler-introduced temporary.
833 /// Function argument.
835 /// Location of function's return value.
839 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
840 pub struct VarBindingForm<'tcx> {
841 /// Is variable bound via `x`, `mut x`, `ref x`, or `ref mut x`?
842 pub binding_mode: ty::BindingMode,
843 /// If an explicit type was provided for this variable binding,
844 /// this holds the source Span of that type.
846 /// NOTE: if you want to change this to a `HirId`, be wary that
847 /// doing so breaks incremental compilation (as of this writing),
848 /// while a `Span` does not cause our tests to fail.
849 pub opt_ty_info: Option<Span>,
850 /// Place of the RHS of the =, or the subject of the `match` where this
851 /// variable is initialized. None in the case of `let PATTERN;`.
852 /// Some((None, ..)) in the case of and `let [mut] x = ...` because
853 /// (a) the right-hand side isn't evaluated as a place expression.
854 /// (b) it gives a way to separate this case from the remaining cases
856 pub opt_match_place: Option<(Option<Place<'tcx>>, Span)>,
857 /// The span of the pattern in which this variable was bound.
861 #[derive(Clone, Debug, TyEncodable, TyDecodable)]
862 pub enum BindingForm<'tcx> {
863 /// This is a binding for a non-`self` binding, or a `self` that has an explicit type.
864 Var(VarBindingForm<'tcx>),
865 /// Binding for a `self`/`&self`/`&mut self` binding where the type is implicit.
866 ImplicitSelf(ImplicitSelfKind),
867 /// Reference used in a guard expression to ensure immutability.
871 /// Represents what type of implicit self a function has, if any.
872 #[derive(Clone, Copy, PartialEq, Debug, TyEncodable, TyDecodable, HashStable)]
873 pub enum ImplicitSelfKind {
874 /// Represents a `fn x(self);`.
876 /// Represents a `fn x(mut self);`.
878 /// Represents a `fn x(&self);`.
880 /// Represents a `fn x(&mut self);`.
882 /// Represents when a function does not have a self argument or
883 /// when a function has a `self: X` argument.
887 TrivialTypeFoldableAndLiftImpls! { BindingForm<'tcx>, }
889 mod binding_form_impl {
890 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
891 use rustc_query_system::ich::StableHashingContext;
893 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for super::BindingForm<'tcx> {
894 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
895 use super::BindingForm::*;
896 std::mem::discriminant(self).hash_stable(hcx, hasher);
899 Var(binding) => binding.hash_stable(hcx, hasher),
900 ImplicitSelf(kind) => kind.hash_stable(hcx, hasher),
907 /// `BlockTailInfo` is attached to the `LocalDecl` for temporaries
908 /// created during evaluation of expressions in a block tail
909 /// expression; that is, a block like `{ STMT_1; STMT_2; EXPR }`.
911 /// It is used to improve diagnostics when such temporaries are
912 /// involved in borrow_check errors, e.g., explanations of where the
913 /// temporaries come from, when their destructors are run, and/or how
914 /// one might revise the code to satisfy the borrow checker's rules.
915 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
916 pub struct BlockTailInfo {
917 /// If `true`, then the value resulting from evaluating this tail
918 /// expression is ignored by the block's expression context.
920 /// Examples include `{ ...; tail };` and `let _ = { ...; tail };`
921 /// but not e.g., `let _x = { ...; tail };`
922 pub tail_result_is_ignored: bool,
924 /// `Span` of the tail expression.
930 /// This can be a binding declared by the user, a temporary inserted by the compiler, a function
931 /// argument, or the return place.
932 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
933 pub struct LocalDecl<'tcx> {
934 /// Whether this is a mutable binding (i.e., `let x` or `let mut x`).
936 /// Temporaries and the return place are always mutable.
937 pub mutability: Mutability,
939 // FIXME(matthewjasper) Don't store in this in `Body`
940 pub local_info: Option<Box<LocalInfo<'tcx>>>,
942 /// `true` if this is an internal local.
944 /// These locals are not based on types in the source code and are only used
945 /// for a few desugarings at the moment.
947 /// The generator transformation will sanity check the locals which are live
948 /// across a suspension point against the type components of the generator
949 /// which type checking knows are live across a suspension point. We need to
950 /// flag drop flags to avoid triggering this check as they are introduced
951 /// outside of type inference.
953 /// This should be sound because the drop flags are fully algebraic, and
954 /// therefore don't affect the auto-trait or outlives properties of the
958 /// If this local is a temporary and `is_block_tail` is `Some`,
959 /// then it is a temporary created for evaluation of some
960 /// subexpression of some block's tail expression (with no
961 /// intervening statement context).
962 // FIXME(matthewjasper) Don't store in this in `Body`
963 pub is_block_tail: Option<BlockTailInfo>,
965 /// The type of this local.
968 /// If the user manually ascribed a type to this variable,
969 /// e.g., via `let x: T`, then we carry that type here. The MIR
970 /// borrow checker needs this information since it can affect
971 /// region inference.
972 // FIXME(matthewjasper) Don't store in this in `Body`
973 pub user_ty: Option<Box<UserTypeProjections>>,
975 /// The *syntactic* (i.e., not visibility) source scope the local is defined
976 /// in. If the local was defined in a let-statement, this
977 /// is *within* the let-statement, rather than outside
980 /// This is needed because the visibility source scope of locals within
981 /// a let-statement is weird.
983 /// The reason is that we want the local to be *within* the let-statement
984 /// for lint purposes, but we want the local to be *after* the let-statement
985 /// for names-in-scope purposes.
987 /// That's it, if we have a let-statement like the one in this
991 /// fn foo(x: &str) {
992 /// #[allow(unused_mut)]
993 /// let mut x: u32 = { // <- one unused mut
994 /// let mut y: u32 = x.parse().unwrap();
1001 /// Then, from a lint point of view, the declaration of `x: u32`
1002 /// (and `y: u32`) are within the `#[allow(unused_mut)]` scope - the
1003 /// lint scopes are the same as the AST/HIR nesting.
1005 /// However, from a name lookup point of view, the scopes look more like
1006 /// as if the let-statements were `match` expressions:
1009 /// fn foo(x: &str) {
1011 /// match x.parse().unwrap() {
1020 /// We care about the name-lookup scopes for debuginfo - if the
1021 /// debuginfo instruction pointer is at the call to `x.parse()`, we
1022 /// want `x` to refer to `x: &str`, but if it is at the call to
1023 /// `drop(x)`, we want it to refer to `x: u32`.
1025 /// To allow both uses to work, we need to have more than a single scope
1026 /// for a local. We have the `source_info.scope` represent the "syntactic"
1027 /// lint scope (with a variable being under its let block) while the
1028 /// `var_debug_info.source_info.scope` represents the "local variable"
1029 /// scope (where the "rest" of a block is under all prior let-statements).
1031 /// The end result looks like this:
1035 /// │{ argument x: &str }
1037 /// │ │{ #[allow(unused_mut)] } // This is actually split into 2 scopes
1038 /// │ │ // in practice because I'm lazy.
1040 /// │ │← x.source_info.scope
1041 /// │ │← `x.parse().unwrap()`
1043 /// │ │ │← y.source_info.scope
1045 /// │ │ │{ let y: u32 }
1047 /// │ │ │← y.var_debug_info.source_info.scope
1050 /// │ │{ let x: u32 }
1051 /// │ │← x.var_debug_info.source_info.scope
1052 /// │ │← `drop(x)` // This accesses `x: u32`.
1054 pub source_info: SourceInfo,
1057 // `LocalDecl` is used a lot. Make sure it doesn't unintentionally get bigger.
1058 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
1059 static_assert_size!(LocalDecl<'_>, 56);
1061 /// Extra information about a some locals that's used for diagnostics and for
1062 /// classifying variables into local variables, statics, etc, which is needed e.g.
1063 /// for unsafety checking.
1065 /// Not used for non-StaticRef temporaries, the return place, or anonymous
1066 /// function parameters.
1067 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
1068 pub enum LocalInfo<'tcx> {
1069 /// A user-defined local variable or function parameter
1071 /// The `BindingForm` is solely used for local diagnostics when generating
1072 /// warnings/errors when compiling the current crate, and therefore it need
1073 /// not be visible across crates.
1074 User(ClearCrossCrate<BindingForm<'tcx>>),
1075 /// A temporary created that references the static with the given `DefId`.
1076 StaticRef { def_id: DefId, is_thread_local: bool },
1077 /// A temporary created that references the const with the given `DefId`
1078 ConstRef { def_id: DefId },
1079 /// A temporary created during the creation of an aggregate
1080 /// (e.g. a temporary for `foo` in `MyStruct { my_field: foo }`)
1084 impl<'tcx> LocalDecl<'tcx> {
1085 /// Returns `true` only if local is a binding that can itself be
1086 /// made mutable via the addition of the `mut` keyword, namely
1087 /// something like the occurrences of `x` in:
1088 /// - `fn foo(x: Type) { ... }`,
1089 /// - `let x = ...`,
1090 /// - or `match ... { C(x) => ... }`
1091 pub fn can_be_made_mutable(&self) -> bool {
1094 Some(box LocalInfo::User(ClearCrossCrate::Set(
1095 BindingForm::Var(VarBindingForm {
1096 binding_mode: ty::BindingMode::BindByValue(_),
1100 }) | BindingForm::ImplicitSelf(ImplicitSelfKind::Imm),
1105 /// Returns `true` if local is definitely not a `ref ident` or
1106 /// `ref mut ident` binding. (Such bindings cannot be made into
1107 /// mutable bindings, but the inverse does not necessarily hold).
1108 pub fn is_nonref_binding(&self) -> bool {
1111 Some(box LocalInfo::User(ClearCrossCrate::Set(
1112 BindingForm::Var(VarBindingForm {
1113 binding_mode: ty::BindingMode::BindByValue(_),
1117 }) | BindingForm::ImplicitSelf(_),
1122 /// Returns `true` if this variable is a named variable or function
1123 /// parameter declared by the user.
1125 pub fn is_user_variable(&self) -> bool {
1126 matches!(self.local_info, Some(box LocalInfo::User(_)))
1129 /// Returns `true` if this is a reference to a variable bound in a `match`
1130 /// expression that is used to access said variable for the guard of the
1132 pub fn is_ref_for_guard(&self) -> bool {
1135 Some(box LocalInfo::User(ClearCrossCrate::Set(BindingForm::RefForGuard)))
1139 /// Returns `Some` if this is a reference to a static item that is used to
1140 /// access that static.
1141 pub fn is_ref_to_static(&self) -> bool {
1142 matches!(self.local_info, Some(box LocalInfo::StaticRef { .. }))
1145 /// Returns `Some` if this is a reference to a thread-local static item that is used to
1146 /// access that static.
1147 pub fn is_ref_to_thread_local(&self) -> bool {
1148 match self.local_info {
1149 Some(box LocalInfo::StaticRef { is_thread_local, .. }) => is_thread_local,
1154 /// Returns `true` is the local is from a compiler desugaring, e.g.,
1155 /// `__next` from a `for` loop.
1157 pub fn from_compiler_desugaring(&self) -> bool {
1158 self.source_info.span.desugaring_kind().is_some()
1161 /// Creates a new `LocalDecl` for a temporary: mutable, non-internal.
1163 pub fn new(ty: Ty<'tcx>, span: Span) -> Self {
1164 Self::with_source_info(ty, SourceInfo::outermost(span))
1167 /// Like `LocalDecl::new`, but takes a `SourceInfo` instead of a `Span`.
1169 pub fn with_source_info(ty: Ty<'tcx>, source_info: SourceInfo) -> Self {
1171 mutability: Mutability::Mut,
1174 is_block_tail: None,
1181 /// Converts `self` into same `LocalDecl` except tagged as internal.
1183 pub fn internal(mut self) -> Self {
1184 self.internal = true;
1188 /// Converts `self` into same `LocalDecl` except tagged as immutable.
1190 pub fn immutable(mut self) -> Self {
1191 self.mutability = Mutability::Not;
1195 /// Converts `self` into same `LocalDecl` except tagged as internal temporary.
1197 pub fn block_tail(mut self, info: BlockTailInfo) -> Self {
1198 assert!(self.is_block_tail.is_none());
1199 self.is_block_tail = Some(info);
1204 #[derive(Clone, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
1205 pub enum VarDebugInfoContents<'tcx> {
1206 /// NOTE(eddyb) There's an unenforced invariant that this `Place` is
1207 /// based on a `Local`, not a `Static`, and contains no indexing.
1209 Const(Constant<'tcx>),
1212 impl<'tcx> Debug for VarDebugInfoContents<'tcx> {
1213 fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
1215 VarDebugInfoContents::Const(c) => write!(fmt, "{}", c),
1216 VarDebugInfoContents::Place(p) => write!(fmt, "{:?}", p),
1221 /// Debug information pertaining to a user variable.
1222 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
1223 pub struct VarDebugInfo<'tcx> {
1226 /// Source info of the user variable, including the scope
1227 /// within which the variable is visible (to debuginfo)
1228 /// (see `LocalDecl`'s `source_info` field for more details).
1229 pub source_info: SourceInfo,
1231 /// Where the data for this user variable is to be found.
1232 pub value: VarDebugInfoContents<'tcx>,
1235 ///////////////////////////////////////////////////////////////////////////
1238 rustc_index::newtype_index! {
1239 /// A node in the MIR [control-flow graph][CFG].
1241 /// There are no branches (e.g., `if`s, function calls, etc.) within a basic block, which makes
1242 /// it easier to do [data-flow analyses] and optimizations. Instead, branches are represented
1243 /// as an edge in a graph between basic blocks.
1245 /// Basic blocks consist of a series of [statements][Statement], ending with a
1246 /// [terminator][Terminator]. Basic blocks can have multiple predecessors and successors,
1247 /// however there is a MIR pass ([`CriticalCallEdges`]) that removes *critical edges*, which
1248 /// are edges that go from a multi-successor node to a multi-predecessor node. This pass is
1249 /// needed because some analyses require that there are no critical edges in the CFG.
1251 /// Note that this type is just an index into [`Body.basic_blocks`](Body::basic_blocks);
1252 /// the actual data that a basic block holds is in [`BasicBlockData`].
1254 /// Read more about basic blocks in the [rustc-dev-guide][guide-mir].
1256 /// [CFG]: https://rustc-dev-guide.rust-lang.org/appendix/background.html#cfg
1257 /// [data-flow analyses]:
1258 /// https://rustc-dev-guide.rust-lang.org/appendix/background.html#what-is-a-dataflow-analysis
1259 /// [`CriticalCallEdges`]: ../../rustc_const_eval/transform/add_call_guards/enum.AddCallGuards.html#variant.CriticalCallEdges
1260 /// [guide-mir]: https://rustc-dev-guide.rust-lang.org/mir/
1261 pub struct BasicBlock {
1263 DEBUG_FORMAT = "bb{}",
1264 const START_BLOCK = 0,
1269 pub fn start_location(self) -> Location {
1270 Location { block: self, statement_index: 0 }
1274 ///////////////////////////////////////////////////////////////////////////
1275 // BasicBlockData and Terminator
1277 /// See [`BasicBlock`] for documentation on what basic blocks are at a high level.
1278 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
1279 pub struct BasicBlockData<'tcx> {
1280 /// List of statements in this block.
1281 pub statements: Vec<Statement<'tcx>>,
1283 /// Terminator for this block.
1285 /// N.B., this should generally ONLY be `None` during construction.
1286 /// Therefore, you should generally access it via the
1287 /// `terminator()` or `terminator_mut()` methods. The only
1288 /// exception is that certain passes, such as `simplify_cfg`, swap
1289 /// out the terminator temporarily with `None` while they continue
1290 /// to recurse over the set of basic blocks.
1291 pub terminator: Option<Terminator<'tcx>>,
1293 /// If true, this block lies on an unwind path. This is used
1294 /// during codegen where distinct kinds of basic blocks may be
1295 /// generated (particularly for MSVC cleanup). Unwind blocks must
1296 /// only branch to other unwind blocks.
1297 pub is_cleanup: bool,
1300 /// Information about an assertion failure.
1301 #[derive(Clone, TyEncodable, TyDecodable, Hash, HashStable, PartialEq, PartialOrd)]
1302 pub enum AssertKind<O> {
1303 BoundsCheck { len: O, index: O },
1304 Overflow(BinOp, O, O),
1308 ResumedAfterReturn(GeneratorKind),
1309 ResumedAfterPanic(GeneratorKind),
1312 #[derive(Clone, Debug, PartialEq, TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable)]
1313 pub enum InlineAsmOperand<'tcx> {
1315 reg: InlineAsmRegOrRegClass,
1316 value: Operand<'tcx>,
1319 reg: InlineAsmRegOrRegClass,
1321 place: Option<Place<'tcx>>,
1324 reg: InlineAsmRegOrRegClass,
1326 in_value: Operand<'tcx>,
1327 out_place: Option<Place<'tcx>>,
1330 value: Box<Constant<'tcx>>,
1333 value: Box<Constant<'tcx>>,
1340 /// Type for MIR `Assert` terminator error messages.
1341 pub type AssertMessage<'tcx> = AssertKind<Operand<'tcx>>;
1343 // FIXME: Change `Successors` to `impl Iterator<Item = BasicBlock>`.
1344 #[allow(rustc::pass_by_value)]
1345 pub type Successors<'a> =
1346 iter::Chain<option::IntoIter<&'a BasicBlock>, slice::Iter<'a, BasicBlock>>;
1347 pub type SuccessorsMut<'a> =
1348 iter::Chain<option::IntoIter<&'a mut BasicBlock>, slice::IterMut<'a, BasicBlock>>;
1350 impl<'tcx> BasicBlockData<'tcx> {
1351 pub fn new(terminator: Option<Terminator<'tcx>>) -> BasicBlockData<'tcx> {
1352 BasicBlockData { statements: vec![], terminator, is_cleanup: false }
1355 /// Accessor for terminator.
1357 /// Terminator may not be None after construction of the basic block is complete. This accessor
1358 /// provides a convenience way to reach the terminator.
1360 pub fn terminator(&self) -> &Terminator<'tcx> {
1361 self.terminator.as_ref().expect("invalid terminator state")
1365 pub fn terminator_mut(&mut self) -> &mut Terminator<'tcx> {
1366 self.terminator.as_mut().expect("invalid terminator state")
1369 pub fn retain_statements<F>(&mut self, mut f: F)
1371 F: FnMut(&mut Statement<'_>) -> bool,
1373 for s in &mut self.statements {
1380 pub fn expand_statements<F, I>(&mut self, mut f: F)
1382 F: FnMut(&mut Statement<'tcx>) -> Option<I>,
1383 I: iter::TrustedLen<Item = Statement<'tcx>>,
1385 // Gather all the iterators we'll need to splice in, and their positions.
1386 let mut splices: Vec<(usize, I)> = vec![];
1387 let mut extra_stmts = 0;
1388 for (i, s) in self.statements.iter_mut().enumerate() {
1389 if let Some(mut new_stmts) = f(s) {
1390 if let Some(first) = new_stmts.next() {
1391 // We can already store the first new statement.
1394 // Save the other statements for optimized splicing.
1395 let remaining = new_stmts.size_hint().0;
1397 splices.push((i + 1 + extra_stmts, new_stmts));
1398 extra_stmts += remaining;
1406 // Splice in the new statements, from the end of the block.
1407 // FIXME(eddyb) This could be more efficient with a "gap buffer"
1408 // where a range of elements ("gap") is left uninitialized, with
1409 // splicing adding new elements to the end of that gap and moving
1410 // existing elements from before the gap to the end of the gap.
1411 // For now, this is safe code, emulating a gap but initializing it.
1412 let mut gap = self.statements.len()..self.statements.len() + extra_stmts;
1413 self.statements.resize(
1415 Statement { source_info: SourceInfo::outermost(DUMMY_SP), kind: StatementKind::Nop },
1417 for (splice_start, new_stmts) in splices.into_iter().rev() {
1418 let splice_end = splice_start + new_stmts.size_hint().0;
1419 while gap.end > splice_end {
1422 self.statements.swap(gap.start, gap.end);
1424 self.statements.splice(splice_start..splice_end, new_stmts);
1425 gap.end = splice_start;
1429 pub fn visitable(&self, index: usize) -> &dyn MirVisitable<'tcx> {
1430 if index < self.statements.len() { &self.statements[index] } else { &self.terminator }
1434 impl<O> AssertKind<O> {
1435 /// Getting a description does not require `O` to be printable, and does not
1436 /// require allocation.
1437 /// The caller is expected to handle `BoundsCheck` separately.
1438 pub fn description(&self) -> &'static str {
1441 Overflow(BinOp::Add, _, _) => "attempt to add with overflow",
1442 Overflow(BinOp::Sub, _, _) => "attempt to subtract with overflow",
1443 Overflow(BinOp::Mul, _, _) => "attempt to multiply with overflow",
1444 Overflow(BinOp::Div, _, _) => "attempt to divide with overflow",
1445 Overflow(BinOp::Rem, _, _) => "attempt to calculate the remainder with overflow",
1446 OverflowNeg(_) => "attempt to negate with overflow",
1447 Overflow(BinOp::Shr, _, _) => "attempt to shift right with overflow",
1448 Overflow(BinOp::Shl, _, _) => "attempt to shift left with overflow",
1449 Overflow(op, _, _) => bug!("{:?} cannot overflow", op),
1450 DivisionByZero(_) => "attempt to divide by zero",
1451 RemainderByZero(_) => "attempt to calculate the remainder with a divisor of zero",
1452 ResumedAfterReturn(GeneratorKind::Gen) => "generator resumed after completion",
1453 ResumedAfterReturn(GeneratorKind::Async(_)) => "`async fn` resumed after completion",
1454 ResumedAfterPanic(GeneratorKind::Gen) => "generator resumed after panicking",
1455 ResumedAfterPanic(GeneratorKind::Async(_)) => "`async fn` resumed after panicking",
1456 BoundsCheck { .. } => bug!("Unexpected AssertKind"),
1460 /// Format the message arguments for the `assert(cond, msg..)` terminator in MIR printing.
1461 pub fn fmt_assert_args<W: Write>(&self, f: &mut W) -> fmt::Result
1467 BoundsCheck { ref len, ref index } => write!(
1469 "\"index out of bounds: the length is {{}} but the index is {{}}\", {:?}, {:?}",
1473 OverflowNeg(op) => {
1474 write!(f, "\"attempt to negate `{{}}`, which would overflow\", {:?}", op)
1476 DivisionByZero(op) => write!(f, "\"attempt to divide `{{}}` by zero\", {:?}", op),
1477 RemainderByZero(op) => write!(
1479 "\"attempt to calculate the remainder of `{{}}` with a divisor of zero\", {:?}",
1482 Overflow(BinOp::Add, l, r) => write!(
1484 "\"attempt to compute `{{}} + {{}}`, which would overflow\", {:?}, {:?}",
1487 Overflow(BinOp::Sub, l, r) => write!(
1489 "\"attempt to compute `{{}} - {{}}`, which would overflow\", {:?}, {:?}",
1492 Overflow(BinOp::Mul, l, r) => write!(
1494 "\"attempt to compute `{{}} * {{}}`, which would overflow\", {:?}, {:?}",
1497 Overflow(BinOp::Div, l, r) => write!(
1499 "\"attempt to compute `{{}} / {{}}`, which would overflow\", {:?}, {:?}",
1502 Overflow(BinOp::Rem, l, r) => write!(
1504 "\"attempt to compute the remainder of `{{}} % {{}}`, which would overflow\", {:?}, {:?}",
1507 Overflow(BinOp::Shr, _, r) => {
1508 write!(f, "\"attempt to shift right by `{{}}`, which would overflow\", {:?}", r)
1510 Overflow(BinOp::Shl, _, r) => {
1511 write!(f, "\"attempt to shift left by `{{}}`, which would overflow\", {:?}", r)
1513 _ => write!(f, "\"{}\"", self.description()),
1518 impl<O: fmt::Debug> fmt::Debug for AssertKind<O> {
1519 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1522 BoundsCheck { ref len, ref index } => write!(
1524 "index out of bounds: the length is {:?} but the index is {:?}",
1527 OverflowNeg(op) => write!(f, "attempt to negate `{:#?}`, which would overflow", op),
1528 DivisionByZero(op) => write!(f, "attempt to divide `{:#?}` by zero", op),
1529 RemainderByZero(op) => write!(
1531 "attempt to calculate the remainder of `{:#?}` with a divisor of zero",
1534 Overflow(BinOp::Add, l, r) => {
1535 write!(f, "attempt to compute `{:#?} + {:#?}`, which would overflow", l, r)
1537 Overflow(BinOp::Sub, l, r) => {
1538 write!(f, "attempt to compute `{:#?} - {:#?}`, which would overflow", l, r)
1540 Overflow(BinOp::Mul, l, r) => {
1541 write!(f, "attempt to compute `{:#?} * {:#?}`, which would overflow", l, r)
1543 Overflow(BinOp::Div, l, r) => {
1544 write!(f, "attempt to compute `{:#?} / {:#?}`, which would overflow", l, r)
1546 Overflow(BinOp::Rem, l, r) => write!(
1548 "attempt to compute the remainder of `{:#?} % {:#?}`, which would overflow",
1551 Overflow(BinOp::Shr, _, r) => {
1552 write!(f, "attempt to shift right by `{:#?}`, which would overflow", r)
1554 Overflow(BinOp::Shl, _, r) => {
1555 write!(f, "attempt to shift left by `{:#?}`, which would overflow", r)
1557 _ => write!(f, "{}", self.description()),
1562 ///////////////////////////////////////////////////////////////////////////
1565 #[derive(Clone, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
1566 pub struct Statement<'tcx> {
1567 pub source_info: SourceInfo,
1568 pub kind: StatementKind<'tcx>,
1571 // `Statement` is used a lot. Make sure it doesn't unintentionally get bigger.
1572 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
1573 static_assert_size!(Statement<'_>, 32);
1575 impl Statement<'_> {
1576 /// Changes a statement to a nop. This is both faster than deleting instructions and avoids
1577 /// invalidating statement indices in `Location`s.
1578 pub fn make_nop(&mut self) {
1579 self.kind = StatementKind::Nop
1582 /// Changes a statement to a nop and returns the original statement.
1583 #[must_use = "If you don't need the statement, use `make_nop` instead"]
1584 pub fn replace_nop(&mut self) -> Self {
1586 source_info: self.source_info,
1587 kind: mem::replace(&mut self.kind, StatementKind::Nop),
1592 /// The various kinds of statements that can appear in MIR.
1594 /// Not all of these are allowed at every [`MirPhase`]. Check the documentation there to see which
1595 /// ones you do not have to worry about. The MIR validator will generally enforce such restrictions,
1596 /// causing an ICE if they are violated.
1597 #[derive(Clone, Debug, PartialEq, TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable)]
1598 pub enum StatementKind<'tcx> {
1599 /// Assign statements roughly correspond to an assignment in Rust proper (`x = ...`) except
1600 /// without the possibility of dropping the previous value (that must be done separately, if at
1601 /// all). The *exact* way this works is undecided. It probably does something like evaluating
1602 /// the LHS to a place and the RHS to a value, and then storing the value to the place. Various
1603 /// parts of this may do type specific things that are more complicated than simply copying
1606 /// **Needs clarification**: The implication of the above idea would be that assignment implies
1607 /// that the resulting value is initialized. I believe we could commit to this separately from
1608 /// committing to whatever part of the memory model we would need to decide on to make the above
1609 /// paragragh precise. Do we want to?
1611 /// Assignments in which the types of the place and rvalue differ are not well-formed.
1613 /// **Needs clarification**: Do we ever want to worry about non-free (in the body) lifetimes for
1614 /// the typing requirement in post drop-elaboration MIR? I think probably not - I'm not sure we
1615 /// could meaningfully require this anyway. How about free lifetimes? Is ignoring this
1616 /// interesting for optimizations? Do we want to allow such optimizations?
1618 /// **Needs clarification**: We currently require that the LHS place not overlap with any place
1619 /// read as part of computation of the RHS for some rvalues (generally those not producing
1620 /// primitives). This requirement is under discussion in [#68364]. As a part of this discussion,
1621 /// it is also unclear in what order the components are evaluated.
1623 /// [#68364]: https://github.com/rust-lang/rust/issues/68364
1625 /// See [`Rvalue`] documentation for details on each of those.
1626 Assign(Box<(Place<'tcx>, Rvalue<'tcx>)>),
1628 /// This represents all the reading that a pattern match may do (e.g., inspecting constants and
1629 /// discriminant values), and the kind of pattern it comes from. This is in order to adapt
1630 /// potential error messages to these specific patterns.
1632 /// Note that this also is emitted for regular `let` bindings to ensure that locals that are
1633 /// never accessed still get some sanity checks for, e.g., `let x: ! = ..;`
1635 /// When executed at runtime this is a nop.
1637 /// Disallowed after drop elaboration.
1638 FakeRead(Box<(FakeReadCause, Place<'tcx>)>),
1640 /// Write the discriminant for a variant to the enum Place.
1642 /// This is permitted for both generators and ADTs. This does not necessarily write to the
1643 /// entire place; instead, it writes to the minimum set of bytes as required by the layout for
1645 SetDiscriminant { place: Box<Place<'tcx>>, variant_index: VariantIdx },
1647 /// Deinitializes the place.
1649 /// This writes `uninit` bytes to the entire place.
1650 Deinit(Box<Place<'tcx>>),
1652 /// `StorageLive` and `StorageDead` statements mark the live range of a local.
1654 /// Using a local before a `StorageLive` or after a `StorageDead` is not well-formed. These
1655 /// statements are not required. If the entire MIR body contains no `StorageLive`/`StorageDead`
1656 /// statements for a particular local, the local is always considered live.
1658 /// More precisely, the MIR validator currently does a `MaybeStorageLiveLocals` analysis to
1659 /// check validity of each use of a local. I believe this is equivalent to requiring for every
1660 /// use of a local, there exist at least one path from the root to that use that contains a
1661 /// `StorageLive` more recently than a `StorageDead`.
1663 /// **Needs clarification**: Is it permitted to have two `StorageLive`s without an intervening
1664 /// `StorageDead`? Two `StorageDead`s without an intervening `StorageLive`? LLVM says poison,
1665 /// yes. If the answer to any of these is "no," is breaking that rule UB or is it an error to
1666 /// have a path in the CFG that might do this?
1669 /// See `StorageLive` above.
1672 /// Retag references in the given place, ensuring they got fresh tags.
1674 /// This is part of the Stacked Borrows model. These statements are currently only interpreted
1675 /// by miri and only generated when `-Z mir-emit-retag` is passed. See
1676 /// <https://internals.rust-lang.org/t/stacked-borrows-an-aliasing-model-for-rust/8153/> for
1679 /// For code that is not specific to stacked borrows, you should consider retags to read
1680 /// and modify the place in an opaque way.
1681 Retag(RetagKind, Box<Place<'tcx>>),
1683 /// Encodes a user's type ascription. These need to be preserved
1684 /// intact so that NLL can respect them. For example:
1688 /// The effect of this annotation is to relate the type `T_y` of the place `y`
1689 /// to the user-given type `T`. The effect depends on the specified variance:
1691 /// - `Covariant` -- requires that `T_y <: T`
1692 /// - `Contravariant` -- requires that `T_y :> T`
1693 /// - `Invariant` -- requires that `T_y == T`
1694 /// - `Bivariant` -- no effect
1696 /// When executed at runtime this is a nop.
1698 /// Disallowed after drop elaboration.
1699 AscribeUserType(Box<(Place<'tcx>, UserTypeProjection)>, ty::Variance),
1701 /// Marks the start of a "coverage region", injected with '-Cinstrument-coverage'. A
1702 /// `Coverage` statement carries metadata about the coverage region, used to inject a coverage
1703 /// map into the binary. If `Coverage::kind` is a `Counter`, the statement also generates
1704 /// executable code, to increment a counter variable at runtime, each time the code region is
1706 Coverage(Box<Coverage>),
1708 /// Denotes a call to the intrinsic function `copy_nonoverlapping`.
1710 /// First, all three operands are evaluated. `src` and `dest` must each be a reference, pointer,
1711 /// or `Box` pointing to the same type `T`. `count` must evaluate to a `usize`. Then, `src` and
1712 /// `dest` are dereferenced, and `count * size_of::<T>()` bytes beginning with the first byte of
1713 /// the `src` place are copied to the continguous range of bytes beginning with the first byte
1716 /// **Needs clarification**: In what order are operands computed and dereferenced? It should
1717 /// probably match the order for assignment, but that is also undecided.
1719 /// **Needs clarification**: Is this typed or not, ie is there a typed load and store involved?
1720 /// I vaguely remember Ralf saying somewhere that he thought it should not be.
1721 CopyNonOverlapping(Box<CopyNonOverlapping<'tcx>>),
1723 /// No-op. Useful for deleting instructions without affecting statement indices.
1727 impl<'tcx> StatementKind<'tcx> {
1728 pub fn as_assign_mut(&mut self) -> Option<&mut (Place<'tcx>, Rvalue<'tcx>)> {
1730 StatementKind::Assign(x) => Some(x),
1735 pub fn as_assign(&self) -> Option<&(Place<'tcx>, Rvalue<'tcx>)> {
1737 StatementKind::Assign(x) => Some(x),
1743 /// Describes what kind of retag is to be performed.
1744 #[derive(Copy, Clone, TyEncodable, TyDecodable, Debug, PartialEq, Eq, Hash, HashStable)]
1745 pub enum RetagKind {
1746 /// The initial retag when entering a function.
1748 /// Retag preparing for a two-phase borrow.
1750 /// Retagging raw pointers.
1752 /// A "normal" retag.
1756 /// The `FakeReadCause` describes the type of pattern why a FakeRead statement exists.
1757 #[derive(Copy, Clone, TyEncodable, TyDecodable, Debug, Hash, HashStable, PartialEq)]
1758 pub enum FakeReadCause {
1759 /// Inject a fake read of the borrowed input at the end of each guards
1762 /// This should ensure that you cannot change the variant for an enum while
1763 /// you are in the midst of matching on it.
1766 /// `let x: !; match x {}` doesn't generate any read of x so we need to
1767 /// generate a read of x to check that it is initialized and safe.
1769 /// If a closure pattern matches a Place starting with an Upvar, then we introduce a
1770 /// FakeRead for that Place outside the closure, in such a case this option would be
1771 /// Some(closure_def_id).
1772 /// Otherwise, the value of the optional DefId will be None.
1773 ForMatchedPlace(Option<DefId>),
1775 /// A fake read of the RefWithinGuard version of a bind-by-value variable
1776 /// in a match guard to ensure that its value hasn't change by the time
1777 /// we create the OutsideGuard version.
1780 /// Officially, the semantics of
1782 /// `let pattern = <expr>;`
1784 /// is that `<expr>` is evaluated into a temporary and then this temporary is
1785 /// into the pattern.
1787 /// However, if we see the simple pattern `let var = <expr>`, we optimize this to
1788 /// evaluate `<expr>` directly into the variable `var`. This is mostly unobservable,
1789 /// but in some cases it can affect the borrow checker, as in #53695.
1790 /// Therefore, we insert a "fake read" here to ensure that we get
1791 /// appropriate errors.
1793 /// If a closure pattern matches a Place starting with an Upvar, then we introduce a
1794 /// FakeRead for that Place outside the closure, in such a case this option would be
1795 /// Some(closure_def_id).
1796 /// Otherwise, the value of the optional DefId will be None.
1797 ForLet(Option<DefId>),
1799 /// If we have an index expression like
1801 /// (*x)[1][{ x = y; 4}]
1803 /// then the first bounds check is invalidated when we evaluate the second
1804 /// index expression. Thus we create a fake borrow of `x` across the second
1805 /// indexer, which will cause a borrow check error.
1809 impl Debug for Statement<'_> {
1810 fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
1811 use self::StatementKind::*;
1813 Assign(box (ref place, ref rv)) => write!(fmt, "{:?} = {:?}", place, rv),
1814 FakeRead(box (ref cause, ref place)) => {
1815 write!(fmt, "FakeRead({:?}, {:?})", cause, place)
1817 Retag(ref kind, ref place) => write!(
1821 RetagKind::FnEntry => "[fn entry] ",
1822 RetagKind::TwoPhase => "[2phase] ",
1823 RetagKind::Raw => "[raw] ",
1824 RetagKind::Default => "",
1828 StorageLive(ref place) => write!(fmt, "StorageLive({:?})", place),
1829 StorageDead(ref place) => write!(fmt, "StorageDead({:?})", place),
1830 SetDiscriminant { ref place, variant_index } => {
1831 write!(fmt, "discriminant({:?}) = {:?}", place, variant_index)
1833 Deinit(ref place) => write!(fmt, "Deinit({:?})", place),
1834 AscribeUserType(box (ref place, ref c_ty), ref variance) => {
1835 write!(fmt, "AscribeUserType({:?}, {:?}, {:?})", place, variance, c_ty)
1837 Coverage(box self::Coverage { ref kind, code_region: Some(ref rgn) }) => {
1838 write!(fmt, "Coverage::{:?} for {:?}", kind, rgn)
1840 Coverage(box ref coverage) => write!(fmt, "Coverage::{:?}", coverage.kind),
1841 CopyNonOverlapping(box crate::mir::CopyNonOverlapping {
1846 write!(fmt, "copy_nonoverlapping(src={:?}, dst={:?}, count={:?})", src, dst, count)
1848 Nop => write!(fmt, "nop"),
1853 #[derive(Clone, Debug, PartialEq, TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable)]
1854 pub struct Coverage {
1855 pub kind: CoverageKind,
1856 pub code_region: Option<CodeRegion>,
1859 #[derive(Clone, Debug, PartialEq, TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable)]
1860 pub struct CopyNonOverlapping<'tcx> {
1861 pub src: Operand<'tcx>,
1862 pub dst: Operand<'tcx>,
1863 /// Number of elements to copy from src to dest, not bytes.
1864 pub count: Operand<'tcx>,
1867 ///////////////////////////////////////////////////////////////////////////
1870 /// Places roughly correspond to a "location in memory." Places in MIR are the same mathematical
1871 /// object as places in Rust. This of course means that what exactly they are is undecided and part
1872 /// of the Rust memory model. However, they will likely contain at least the following pieces of
1873 /// information in some form:
1875 /// 1. The address in memory that the place refers to.
1876 /// 2. The provenance with which the place is being accessed.
1877 /// 3. The type of the place and an optional variant index. See [`PlaceTy`][tcx::PlaceTy].
1878 /// 4. Optionally, some metadata. This exists if and only if the type of the place is not `Sized`.
1880 /// We'll give a description below of how all pieces of the place except for the provenance are
1881 /// calculated. We cannot give a description of the provenance, because that is part of the
1882 /// undecided aliasing model - we only include it here at all to acknowledge its existence.
1884 /// Each local naturally corresponds to the place `Place { local, projection: [] }`. This place has
1885 /// the address of the local's allocation and the type of the local.
1887 /// **Needs clarification:** Unsized locals seem to present a bit of an issue. Their allocation
1888 /// can't actually be created on `StorageLive`, because it's unclear how big to make the allocation.
1889 /// Furthermore, MIR produces assignments to unsized locals, although that is not permitted under
1890 /// `#![feature(unsized_locals)]` in Rust. Besides just putting "unsized locals are special and
1891 /// different" in a bunch of places, I (JakobDegen) don't know how to incorporate this behavior into
1892 /// the current MIR semantics in a clean way - possibly this needs some design work first.
1894 /// For places that are not locals, ie they have a non-empty list of projections, we define the
1895 /// values as a function of the parent place, that is the place with its last [`ProjectionElem`]
1896 /// stripped. The way this is computed of course depends on the kind of that last projection
1899 /// - [`Downcast`](ProjectionElem::Downcast): This projection sets the place's variant index to the
1900 /// given one, and makes no other changes. A `Downcast` projection on a place with its variant
1901 /// index already set is not well-formed.
1902 /// - [`Field`](ProjectionElem::Field): `Field` projections take their parent place and create a
1903 /// place referring to one of the fields of the type. The resulting address is the parent
1904 /// address, plus the offset of the field. The type becomes the type of the field. If the parent
1905 /// was unsized and so had metadata associated with it, then the metadata is retained if the
1906 /// field is unsized and thrown out if it is sized.
1908 /// These projections are only legal for tuples, ADTs, closures, and generators. If the ADT or
1909 /// generator has more than one variant, the parent place's variant index must be set, indicating
1910 /// which variant is being used. If it has just one variant, the variant index may or may not be
1911 /// included - the single possible variant is inferred if it is not included.
1912 /// - [`ConstantIndex`](ProjectionElem::ConstantIndex): Computes an offset in units of `T` into the
1913 /// place as described in the documentation for the `ProjectionElem`. The resulting address is
1914 /// the parent's address plus that offset, and the type is `T`. This is only legal if the parent
1915 /// place has type `[T; N]` or `[T]` (*not* `&[T]`). Since such a `T` is always sized, any
1916 /// resulting metadata is thrown out.
1917 /// - [`Subslice`](ProjectionElem::Subslice): This projection calculates an offset and a new
1918 /// address in a similar manner as `ConstantIndex`. It is also only legal on `[T; N]` and `[T]`.
1919 /// However, this yields a `Place` of type `[T]`, and additionally sets the metadata to be the
1920 /// length of the subslice.
1921 /// - [`Index`](ProjectionElem::Index): Like `ConstantIndex`, only legal on `[T; N]` or `[T]`.
1922 /// However, `Index` additionally takes a local from which the value of the index is computed at
1923 /// runtime. Computing the value of the index involves interpreting the `Local` as a
1924 /// `Place { local, projection: [] }`, and then computing its value as if done via
1925 /// [`Operand::Copy`]. The array/slice is then indexed with the resulting value. The local must
1926 /// have type `usize`.
1927 /// - [`Deref`](ProjectionElem::Deref): Derefs are the last type of projection, and the most
1928 /// complicated. They are only legal on parent places that are references, pointers, or `Box`. A
1929 /// `Deref` projection begins by loading a value from the parent place, as if by
1930 /// [`Operand::Copy`]. It then dereferences the resulting pointer, creating a place of the
1931 /// pointee's type. The resulting address is the address that was stored in the pointer. If the
1932 /// pointee type is unsized, the pointer additionally stored the value of the metadata.
1934 /// Computing a place may cause UB. One possibility is that the pointer used for a `Deref` may not
1935 /// be suitably aligned. Another possibility is that the place is not in bounds, meaning it does not
1936 /// point to an actual allocation.
1938 /// However, if this is actually UB and when the UB kicks in is undecided. This is being discussed
1939 /// in [UCG#319]. The options include that every place must obey those rules, that only some places
1940 /// must obey them, or that places impose no rules of their own.
1942 /// [UCG#319]: https://github.com/rust-lang/unsafe-code-guidelines/issues/319
1944 /// Rust currently requires that every place obey those two rules. This is checked by MIRI and taken
1945 /// advantage of by codegen (via `gep inbounds`). That is possibly subject to change.
1946 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, HashStable)]
1947 pub struct Place<'tcx> {
1950 /// projection out of a place (access a field, deref a pointer, etc)
1951 pub projection: &'tcx List<PlaceElem<'tcx>>,
1954 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
1955 static_assert_size!(Place<'_>, 16);
1957 #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
1958 #[derive(TyEncodable, TyDecodable, HashStable)]
1959 pub enum ProjectionElem<V, T> {
1962 /// Index into a slice/array.
1964 /// Note that this does not also dereference, and so it does not exactly correspond to slice
1965 /// indexing in Rust. In other words, in the below Rust code:
1968 /// let x = &[1, 2, 3, 4];
1973 /// The `x[i]` is turned into a `Deref` followed by an `Index`, not just an `Index`. The same
1974 /// thing is true of the `ConstantIndex` and `Subslice` projections below.
1977 /// These indices are generated by slice patterns. Easiest to explain
1981 /// [X, _, .._, _, _] => { offset: 0, min_length: 4, from_end: false },
1982 /// [_, X, .._, _, _] => { offset: 1, min_length: 4, from_end: false },
1983 /// [_, _, .._, X, _] => { offset: 2, min_length: 4, from_end: true },
1984 /// [_, _, .._, _, X] => { offset: 1, min_length: 4, from_end: true },
1987 /// index or -index (in Python terms), depending on from_end
1989 /// The thing being indexed must be at least this long. For arrays this
1990 /// is always the exact length.
1992 /// Counting backwards from end? This is always false when indexing an
1997 /// These indices are generated by slice patterns.
1999 /// If `from_end` is true `slice[from..slice.len() - to]`.
2000 /// Otherwise `array[from..to]`.
2004 /// Whether `to` counts from the start or end of the array/slice.
2005 /// For `PlaceElem`s this is `true` if and only if the base is a slice.
2006 /// For `ProjectionKind`, this can also be `true` for arrays.
2010 /// "Downcast" to a variant of an ADT. Currently, we only introduce
2011 /// this for ADTs with more than one variant. It may be better to
2012 /// just introduce it always, or always for enums.
2014 /// The included Symbol is the name of the variant, used for printing MIR.
2015 Downcast(Option<Symbol>, VariantIdx),
2018 impl<V, T> ProjectionElem<V, T> {
2019 /// Returns `true` if the target of this projection may refer to a different region of memory
2021 fn is_indirect(&self) -> bool {
2023 Self::Deref => true,
2027 | Self::ConstantIndex { .. }
2028 | Self::Subslice { .. }
2029 | Self::Downcast(_, _) => false,
2033 /// Returns `true` if this is a `Downcast` projection with the given `VariantIdx`.
2034 pub fn is_downcast_to(&self, v: VariantIdx) -> bool {
2035 matches!(*self, Self::Downcast(_, x) if x == v)
2038 /// Returns `true` if this is a `Field` projection with the given index.
2039 pub fn is_field_to(&self, f: Field) -> bool {
2040 matches!(*self, Self::Field(x, _) if x == f)
2044 /// Alias for projections as they appear in places, where the base is a place
2045 /// and the index is a local.
2046 pub type PlaceElem<'tcx> = ProjectionElem<Local, Ty<'tcx>>;
2048 // This type is fairly frequently used, so we shouldn't unintentionally increase
2050 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
2051 static_assert_size!(PlaceElem<'_>, 24);
2053 /// Alias for projections as they appear in `UserTypeProjection`, where we
2054 /// need neither the `V` parameter for `Index` nor the `T` for `Field`.
2055 pub type ProjectionKind = ProjectionElem<(), ()>;
2057 rustc_index::newtype_index! {
2058 /// A [newtype'd][wrapper] index type in the MIR [control-flow graph][CFG]
2060 /// A field (e.g., `f` in `_1.f`) is one variant of [`ProjectionElem`]. Conceptually,
2061 /// rustc can identify that a field projection refers to either two different regions of memory
2062 /// or the same one between the base and the 'projection element'.
2063 /// Read more about projections in the [rustc-dev-guide][mir-datatypes]
2065 /// [wrapper]: https://rustc-dev-guide.rust-lang.org/appendix/glossary.html#newtype
2066 /// [CFG]: https://rustc-dev-guide.rust-lang.org/appendix/background.html#cfg
2067 /// [mir-datatypes]: https://rustc-dev-guide.rust-lang.org/mir/index.html#mir-data-types
2070 DEBUG_FORMAT = "field[{}]"
2074 #[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
2075 pub struct PlaceRef<'tcx> {
2077 pub projection: &'tcx [PlaceElem<'tcx>],
2080 impl<'tcx> Place<'tcx> {
2081 // FIXME change this to a const fn by also making List::empty a const fn.
2082 pub fn return_place() -> Place<'tcx> {
2083 Place { local: RETURN_PLACE, projection: List::empty() }
2086 /// Returns `true` if this `Place` contains a `Deref` projection.
2088 /// If `Place::is_indirect` returns false, the caller knows that the `Place` refers to the
2089 /// same region of memory as its base.
2090 pub fn is_indirect(&self) -> bool {
2091 self.projection.iter().any(|elem| elem.is_indirect())
2094 /// Finds the innermost `Local` from this `Place`, *if* it is either a local itself or
2095 /// a single deref of a local.
2097 pub fn local_or_deref_local(&self) -> Option<Local> {
2098 self.as_ref().local_or_deref_local()
2101 /// If this place represents a local variable like `_X` with no
2102 /// projections, return `Some(_X)`.
2104 pub fn as_local(&self) -> Option<Local> {
2105 self.as_ref().as_local()
2109 pub fn as_ref(&self) -> PlaceRef<'tcx> {
2110 PlaceRef { local: self.local, projection: &self.projection }
2113 /// Iterate over the projections in evaluation order, i.e., the first element is the base with
2114 /// its projection and then subsequently more projections are added.
2115 /// As a concrete example, given the place a.b.c, this would yield:
2119 /// Given a place without projections, the iterator is empty.
2121 pub fn iter_projections(
2123 ) -> impl Iterator<Item = (PlaceRef<'tcx>, PlaceElem<'tcx>)> + DoubleEndedIterator {
2124 self.projection.iter().enumerate().map(move |(i, proj)| {
2125 let base = PlaceRef { local: self.local, projection: &self.projection[..i] };
2130 /// Generates a new place by appending `more_projections` to the existing ones
2131 /// and interning the result.
2132 pub fn project_deeper(self, more_projections: &[PlaceElem<'tcx>], tcx: TyCtxt<'tcx>) -> Self {
2133 if more_projections.is_empty() {
2137 let mut v: Vec<PlaceElem<'tcx>>;
2139 let new_projections = if self.projection.is_empty() {
2142 v = Vec::with_capacity(self.projection.len() + more_projections.len());
2143 v.extend(self.projection);
2144 v.extend(more_projections);
2148 Place { local: self.local, projection: tcx.intern_place_elems(new_projections) }
2152 impl From<Local> for Place<'_> {
2153 fn from(local: Local) -> Self {
2154 Place { local, projection: List::empty() }
2158 impl<'tcx> PlaceRef<'tcx> {
2159 /// Finds the innermost `Local` from this `Place`, *if* it is either a local itself or
2160 /// a single deref of a local.
2161 pub fn local_or_deref_local(&self) -> Option<Local> {
2163 PlaceRef { local, projection: [] }
2164 | PlaceRef { local, projection: [ProjectionElem::Deref] } => Some(local),
2169 /// If this place represents a local variable like `_X` with no
2170 /// projections, return `Some(_X)`.
2172 pub fn as_local(&self) -> Option<Local> {
2174 PlaceRef { local, projection: [] } => Some(local),
2180 pub fn last_projection(&self) -> Option<(PlaceRef<'tcx>, PlaceElem<'tcx>)> {
2181 if let &[ref proj_base @ .., elem] = self.projection {
2182 Some((PlaceRef { local: self.local, projection: proj_base }, elem))
2189 impl Debug for Place<'_> {
2190 fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
2191 for elem in self.projection.iter().rev() {
2193 ProjectionElem::Downcast(_, _) | ProjectionElem::Field(_, _) => {
2194 write!(fmt, "(").unwrap();
2196 ProjectionElem::Deref => {
2197 write!(fmt, "(*").unwrap();
2199 ProjectionElem::Index(_)
2200 | ProjectionElem::ConstantIndex { .. }
2201 | ProjectionElem::Subslice { .. } => {}
2205 write!(fmt, "{:?}", self.local)?;
2207 for elem in self.projection.iter() {
2209 ProjectionElem::Downcast(Some(name), _index) => {
2210 write!(fmt, " as {})", name)?;
2212 ProjectionElem::Downcast(None, index) => {
2213 write!(fmt, " as variant#{:?})", index)?;
2215 ProjectionElem::Deref => {
2218 ProjectionElem::Field(field, ty) => {
2219 write!(fmt, ".{:?}: {:?})", field.index(), ty)?;
2221 ProjectionElem::Index(ref index) => {
2222 write!(fmt, "[{:?}]", index)?;
2224 ProjectionElem::ConstantIndex { offset, min_length, from_end: false } => {
2225 write!(fmt, "[{:?} of {:?}]", offset, min_length)?;
2227 ProjectionElem::ConstantIndex { offset, min_length, from_end: true } => {
2228 write!(fmt, "[-{:?} of {:?}]", offset, min_length)?;
2230 ProjectionElem::Subslice { from, to, from_end: true } if to == 0 => {
2231 write!(fmt, "[{:?}:]", from)?;
2233 ProjectionElem::Subslice { from, to, from_end: true } if from == 0 => {
2234 write!(fmt, "[:-{:?}]", to)?;
2236 ProjectionElem::Subslice { from, to, from_end: true } => {
2237 write!(fmt, "[{:?}:-{:?}]", from, to)?;
2239 ProjectionElem::Subslice { from, to, from_end: false } => {
2240 write!(fmt, "[{:?}..{:?}]", from, to)?;
2249 ///////////////////////////////////////////////////////////////////////////
2252 rustc_index::newtype_index! {
2253 pub struct SourceScope {
2255 DEBUG_FORMAT = "scope[{}]",
2256 const OUTERMOST_SOURCE_SCOPE = 0,
2261 /// Finds the original HirId this MIR item came from.
2262 /// This is necessary after MIR optimizations, as otherwise we get a HirId
2263 /// from the function that was inlined instead of the function call site.
2264 pub fn lint_root<'tcx>(
2266 source_scopes: &IndexVec<SourceScope, SourceScopeData<'tcx>>,
2267 ) -> Option<HirId> {
2268 let mut data = &source_scopes[self];
2269 // FIXME(oli-obk): we should be able to just walk the `inlined_parent_scope`, but it
2270 // does not work as I thought it would. Needs more investigation and documentation.
2271 while data.inlined.is_some() {
2273 data = &source_scopes[data.parent_scope.unwrap()];
2276 match &data.local_data {
2277 ClearCrossCrate::Set(data) => Some(data.lint_root),
2278 ClearCrossCrate::Clear => None,
2283 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
2284 pub struct SourceScopeData<'tcx> {
2286 pub parent_scope: Option<SourceScope>,
2288 /// Whether this scope is the root of a scope tree of another body,
2289 /// inlined into this body by the MIR inliner.
2290 /// `ty::Instance` is the callee, and the `Span` is the call site.
2291 pub inlined: Option<(ty::Instance<'tcx>, Span)>,
2293 /// Nearest (transitive) parent scope (if any) which is inlined.
2294 /// This is an optimization over walking up `parent_scope`
2295 /// until a scope with `inlined: Some(...)` is found.
2296 pub inlined_parent_scope: Option<SourceScope>,
2298 /// Crate-local information for this source scope, that can't (and
2299 /// needn't) be tracked across crates.
2300 pub local_data: ClearCrossCrate<SourceScopeLocalData>,
2303 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
2304 pub struct SourceScopeLocalData {
2305 /// An `HirId` with lint levels equivalent to this scope's lint levels.
2306 pub lint_root: hir::HirId,
2307 /// The unsafe block that contains this node.
2311 ///////////////////////////////////////////////////////////////////////////
2314 /// An operand in MIR represents a "value" in Rust, the definition of which is undecided and part of
2315 /// the memory model. One proposal for a definition of values can be found [on UCG][value-def].
2317 /// [value-def]: https://github.com/rust-lang/unsafe-code-guidelines/blob/master/wip/value-domain.md
2319 /// The most common way to create values is via loading a place. Loading a place is an operation
2320 /// which reads the memory of the place and converts it to a value. This is a fundamentally *typed*
2321 /// operation. The nature of the value produced depends on the type of the conversion. Furthermore,
2322 /// there may be other effects: if the type has a validity constraint loading the place might be UB
2323 /// if the validity constraint is not met.
2325 /// **Needs clarification:** Ralf proposes that loading a place not have side-effects.
2326 /// This is what is implemented in miri today. Are these the semantics we want for MIR? Is this
2327 /// something we can even decide without knowing more about Rust's memory model?
2329 /// **Needs clarifiation:** Is loading a place that has its variant index set well-formed? Miri
2330 /// currently implements it, but it seems like this may be something to check against in the
2332 #[derive(Clone, PartialEq, TyEncodable, TyDecodable, Hash, HashStable)]
2333 pub enum Operand<'tcx> {
2334 /// Creates a value by loading the given place.
2336 /// Before drop elaboration, the type of the place must be `Copy`. After drop elaboration there
2337 /// is no such requirement.
2340 /// Creates a value by performing loading the place, just like the `Copy` operand.
2342 /// This *may* additionally overwrite the place with `uninit` bytes, depending on how we decide
2343 /// in [UCG#188]. You should not emit MIR that may attempt a subsequent second load of this
2344 /// place without first re-initializing it.
2346 /// [UCG#188]: https://github.com/rust-lang/unsafe-code-guidelines/issues/188
2349 /// Constants are already semantically values, and remain unchanged.
2350 Constant(Box<Constant<'tcx>>),
2353 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
2354 static_assert_size!(Operand<'_>, 24);
2356 impl<'tcx> Debug for Operand<'tcx> {
2357 fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
2358 use self::Operand::*;
2360 Constant(ref a) => write!(fmt, "{:?}", a),
2361 Copy(ref place) => write!(fmt, "{:?}", place),
2362 Move(ref place) => write!(fmt, "move {:?}", place),
2367 impl<'tcx> Operand<'tcx> {
2368 /// Convenience helper to make a constant that refers to the fn
2369 /// with given `DefId` and substs. Since this is used to synthesize
2370 /// MIR, assumes `user_ty` is None.
2371 pub fn function_handle(
2374 substs: SubstsRef<'tcx>,
2377 let ty = tcx.type_of(def_id).subst(tcx, substs);
2378 Operand::Constant(Box::new(Constant {
2381 literal: ConstantKind::Ty(ty::Const::zero_sized(tcx, ty)),
2385 pub fn is_move(&self) -> bool {
2386 matches!(self, Operand::Move(..))
2389 /// Convenience helper to make a literal-like constant from a given scalar value.
2390 /// Since this is used to synthesize MIR, assumes `user_ty` is None.
2391 pub fn const_from_scalar(
2396 ) -> Operand<'tcx> {
2398 let param_env_and_ty = ty::ParamEnv::empty().and(ty);
2400 .layout_of(param_env_and_ty)
2401 .unwrap_or_else(|e| panic!("could not compute layout for {:?}: {:?}", ty, e))
2403 let scalar_size = match val {
2404 Scalar::Int(int) => int.size(),
2405 _ => panic!("Invalid scalar type {:?}", val),
2407 scalar_size == type_size
2409 Operand::Constant(Box::new(Constant {
2412 literal: ConstantKind::Val(ConstValue::Scalar(val), ty),
2416 pub fn to_copy(&self) -> Self {
2418 Operand::Copy(_) | Operand::Constant(_) => self.clone(),
2419 Operand::Move(place) => Operand::Copy(place),
2423 /// Returns the `Place` that is the target of this `Operand`, or `None` if this `Operand` is a
2425 pub fn place(&self) -> Option<Place<'tcx>> {
2427 Operand::Copy(place) | Operand::Move(place) => Some(*place),
2428 Operand::Constant(_) => None,
2432 /// Returns the `Constant` that is the target of this `Operand`, or `None` if this `Operand` is a
2434 pub fn constant(&self) -> Option<&Constant<'tcx>> {
2436 Operand::Constant(x) => Some(&**x),
2437 Operand::Copy(_) | Operand::Move(_) => None,
2441 /// Gets the `ty::FnDef` from an operand if it's a constant function item.
2443 /// While this is unlikely in general, it's the normal case of what you'll
2444 /// find as the `func` in a [`TerminatorKind::Call`].
2445 pub fn const_fn_def(&self) -> Option<(DefId, SubstsRef<'tcx>)> {
2446 let const_ty = self.constant()?.literal.ty();
2447 if let ty::FnDef(def_id, substs) = *const_ty.kind() { Some((def_id, substs)) } else { None }
2451 ///////////////////////////////////////////////////////////////////////////
2454 #[derive(Clone, TyEncodable, TyDecodable, Hash, HashStable, PartialEq)]
2455 /// The various kinds of rvalues that can appear in MIR.
2457 /// Not all of these are allowed at every [`MirPhase`] - when this is the case, it's stated below.
2459 /// Computing any rvalue begins by evaluating the places and operands in some order (**Needs
2460 /// clarification**: Which order?). These are then used to produce a "value" - the same kind of
2461 /// value that an [`Operand`] produces.
2462 pub enum Rvalue<'tcx> {
2463 /// Yields the operand unchanged
2466 /// Creates an array where each element is the value of the operand.
2468 /// This is the cause of a bug in the case where the repetition count is zero because the value
2469 /// is not dropped, see [#74836].
2471 /// Corresponds to source code like `[x; 32]`.
2473 /// [#74836]: https://github.com/rust-lang/rust/issues/74836
2474 Repeat(Operand<'tcx>, ty::Const<'tcx>),
2476 /// Creates a reference of the indicated kind to the place.
2478 /// There is not much to document here, because besides the obvious parts the semantics of this
2479 /// are essentially entirely a part of the aliasing model. There are many UCG issues discussing
2480 /// exactly what the behavior of this operation should be.
2482 /// `Shallow` borrows are disallowed after drop lowering.
2483 Ref(Region<'tcx>, BorrowKind, Place<'tcx>),
2485 /// Creates a pointer/reference to the given thread local.
2487 /// The yielded type is a `*mut T` if the static is mutable, otherwise if the static is extern a
2488 /// `*const T`, and if neither of those apply a `&T`.
2490 /// **Note:** This is a runtime operation that actually executes code and is in this sense more
2491 /// like a function call. Also, eliminating dead stores of this rvalue causes `fn main() {}` to
2492 /// SIGILL for some reason that I (JakobDegen) never got a chance to look into.
2494 /// **Needs clarification**: Are there weird additional semantics here related to the runtime
2495 /// nature of this operation?
2496 ThreadLocalRef(DefId),
2498 /// Creates a pointer with the indicated mutability to the place.
2500 /// This is generated by pointer casts like `&v as *const _` or raw address of expressions like
2501 /// `&raw v` or `addr_of!(v)`.
2503 /// Like with references, the semantics of this operation are heavily dependent on the aliasing
2505 AddressOf(Mutability, Place<'tcx>),
2507 /// Yields the length of the place, as a `usize`.
2509 /// If the type of the place is an array, this is the array length. For slices (`[T]`, not
2510 /// `&[T]`) this accesses the place's metadata to determine the length. This rvalue is
2511 /// ill-formed for places of other types.
2514 /// Performs essentially all of the casts that can be performed via `as`.
2516 /// This allows for casts from/to a variety of types.
2518 /// **FIXME**: Document exactly which `CastKind`s allow which types of casts. Figure out why
2519 /// `ArrayToPointer` and `MutToConstPointer` are special.
2520 Cast(CastKind, Operand<'tcx>, Ty<'tcx>),
2522 /// * `Offset` has the same semantics as [`offset`](pointer::offset), except that the second
2523 /// parameter may be a `usize` as well.
2524 /// * The comparison operations accept `bool`s, `char`s, signed or unsigned integers, floats,
2525 /// raw pointers, or function pointers and return a `bool`. The types of the operands must be
2526 /// matching, up to the usual caveat of the lifetimes in function pointers.
2527 /// * Left and right shift operations accept signed or unsigned integers not necessarily of the
2528 /// same type and return a value of the same type as their LHS. Like in Rust, the RHS is
2529 /// truncated as needed.
2530 /// * The `Bit*` operations accept signed integers, unsigned integers, or bools with matching
2531 /// types and return a value of that type.
2532 /// * The remaining operations accept signed integers, unsigned integers, or floats with
2533 /// matching types and return a value of that type.
2534 BinaryOp(BinOp, Box<(Operand<'tcx>, Operand<'tcx>)>),
2536 /// Same as `BinaryOp`, but yields `(T, bool)` instead of `T`. In addition to performing the
2537 /// same computation as the matching `BinaryOp`, checks if the infinite precison result would be
2538 /// unequal to the actual result and sets the `bool` if this is the case.
2540 /// This only supports addition, subtraction, multiplication, and shift operations on integers.
2541 CheckedBinaryOp(BinOp, Box<(Operand<'tcx>, Operand<'tcx>)>),
2543 /// Computes a value as described by the operation.
2544 NullaryOp(NullOp, Ty<'tcx>),
2546 /// Exactly like `BinaryOp`, but less operands.
2548 /// Also does two's-complement arithmetic. Negation requires a signed integer or a float;
2549 /// bitwise not requires a signed integer, unsigned integer, or bool. Both operation kinds
2550 /// return a value with the same type as their operand.
2551 UnaryOp(UnOp, Operand<'tcx>),
2553 /// Computes the discriminant of the place, returning it as an integer of type
2554 /// [`discriminant_ty`].
2556 /// The validity requirements for the underlying value are undecided for this rvalue, see
2557 /// [#91095]. Note too that the value of the discriminant is not the same thing as the
2558 /// variant index; use [`discriminant_for_variant`] to convert.
2560 /// For types defined in the source code as enums, this is well behaved. This is also well
2561 /// formed for other types, but yields no particular value - there is no reason it couldn't be
2562 /// defined to yield eg zero though.
2564 /// [`discriminant_ty`]: crate::ty::Ty::discriminant_ty
2565 /// [#91095]: https://github.com/rust-lang/rust/issues/91095
2566 /// [`discriminant_for_variant`]: crate::ty::Ty::discriminant_for_variant
2567 Discriminant(Place<'tcx>),
2569 /// Creates an aggregate value, like a tuple or struct.
2571 /// This is needed because dataflow analysis needs to distinguish
2572 /// `dest = Foo { x: ..., y: ... }` from `dest.x = ...; dest.y = ...;` in the case that `Foo`
2573 /// has a destructor.
2575 /// Disallowed after deaggregation for all aggregate kinds except `Array` and `Generator`. After
2576 /// generator lowering, `Generator` aggregate kinds are disallowed too.
2577 Aggregate(Box<AggregateKind<'tcx>>, Vec<Operand<'tcx>>),
2579 /// Transmutes a `*mut u8` into shallow-initialized `Box<T>`.
2581 /// This is different from a normal transmute because dataflow analysis will treat the box as
2582 /// initialized but its content as uninitialized. Like other pointer casts, this in general
2583 /// affects alias analysis.
2585 /// Disallowed after drop elaboration.
2586 ShallowInitBox(Operand<'tcx>, Ty<'tcx>),
2589 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
2590 static_assert_size!(Rvalue<'_>, 40);
2592 #[derive(Clone, Copy, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
2595 Pointer(PointerCast),
2598 #[derive(Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
2599 pub enum AggregateKind<'tcx> {
2600 /// The type is of the element
2604 /// The second field is the variant index. It's equal to 0 for struct
2605 /// and union expressions. The fourth field is
2606 /// active field number and is present only for union expressions
2607 /// -- e.g., for a union expression `SomeUnion { c: .. }`, the
2608 /// active field index would identity the field `c`
2609 Adt(DefId, VariantIdx, SubstsRef<'tcx>, Option<UserTypeAnnotationIndex>, Option<usize>),
2611 Closure(DefId, SubstsRef<'tcx>),
2612 Generator(DefId, SubstsRef<'tcx>, hir::Movability),
2615 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
2616 static_assert_size!(AggregateKind<'_>, 48);
2618 #[derive(Copy, Clone, Debug, PartialEq, PartialOrd, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
2620 /// The `+` operator (addition)
2622 /// The `-` operator (subtraction)
2624 /// The `*` operator (multiplication)
2626 /// The `/` operator (division)
2628 /// Division by zero is UB, because the compiler should have inserted checks
2631 /// The `%` operator (modulus)
2633 /// Using zero as the modulus (second operand) is UB, because the compiler
2634 /// should have inserted checks prior to this.
2636 /// The `^` operator (bitwise xor)
2638 /// The `&` operator (bitwise and)
2640 /// The `|` operator (bitwise or)
2642 /// The `<<` operator (shift left)
2644 /// The offset is truncated to the size of the first operand before shifting.
2646 /// The `>>` operator (shift right)
2648 /// The offset is truncated to the size of the first operand before shifting.
2650 /// The `==` operator (equality)
2652 /// The `<` operator (less than)
2654 /// The `<=` operator (less than or equal to)
2656 /// The `!=` operator (not equal to)
2658 /// The `>=` operator (greater than or equal to)
2660 /// The `>` operator (greater than)
2662 /// The `ptr.offset` operator
2667 pub fn is_checkable(self) -> bool {
2669 matches!(self, Add | Sub | Mul | Shl | Shr)
2673 #[derive(Copy, Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
2675 /// Returns the size of a value of that type
2677 /// Returns the minimum alignment of a type
2681 #[derive(Copy, Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
2683 /// The `!` operator for logical inversion
2685 /// The `-` operator for negation
2689 impl<'tcx> Debug for Rvalue<'tcx> {
2690 fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
2691 use self::Rvalue::*;
2694 Use(ref place) => write!(fmt, "{:?}", place),
2695 Repeat(ref a, b) => {
2696 write!(fmt, "[{:?}; ", a)?;
2697 pretty_print_const(b, fmt, false)?;
2700 Len(ref a) => write!(fmt, "Len({:?})", a),
2701 Cast(ref kind, ref place, ref ty) => {
2702 write!(fmt, "{:?} as {:?} ({:?})", place, ty, kind)
2704 BinaryOp(ref op, box (ref a, ref b)) => write!(fmt, "{:?}({:?}, {:?})", op, a, b),
2705 CheckedBinaryOp(ref op, box (ref a, ref b)) => {
2706 write!(fmt, "Checked{:?}({:?}, {:?})", op, a, b)
2708 UnaryOp(ref op, ref a) => write!(fmt, "{:?}({:?})", op, a),
2709 Discriminant(ref place) => write!(fmt, "discriminant({:?})", place),
2710 NullaryOp(ref op, ref t) => write!(fmt, "{:?}({:?})", op, t),
2711 ThreadLocalRef(did) => ty::tls::with(|tcx| {
2712 let muta = tcx.static_mutability(did).unwrap().prefix_str();
2713 write!(fmt, "&/*tls*/ {}{}", muta, tcx.def_path_str(did))
2715 Ref(region, borrow_kind, ref place) => {
2716 let kind_str = match borrow_kind {
2717 BorrowKind::Shared => "",
2718 BorrowKind::Shallow => "shallow ",
2719 BorrowKind::Mut { .. } | BorrowKind::Unique => "mut ",
2722 // When printing regions, add trailing space if necessary.
2723 let print_region = ty::tls::with(|tcx| {
2724 tcx.sess.verbose() || tcx.sess.opts.debugging_opts.identify_regions
2726 let region = if print_region {
2727 let mut region = region.to_string();
2728 if !region.is_empty() {
2733 // Do not even print 'static
2736 write!(fmt, "&{}{}{:?}", region, kind_str, place)
2739 AddressOf(mutability, ref place) => {
2740 let kind_str = match mutability {
2741 Mutability::Mut => "mut",
2742 Mutability::Not => "const",
2745 write!(fmt, "&raw {} {:?}", kind_str, place)
2748 Aggregate(ref kind, ref places) => {
2749 let fmt_tuple = |fmt: &mut Formatter<'_>, name: &str| {
2750 let mut tuple_fmt = fmt.debug_tuple(name);
2751 for place in places {
2752 tuple_fmt.field(place);
2758 AggregateKind::Array(_) => write!(fmt, "{:?}", places),
2760 AggregateKind::Tuple => {
2761 if places.is_empty() {
2768 AggregateKind::Adt(adt_did, variant, substs, _user_ty, _) => {
2769 ty::tls::with(|tcx| {
2770 let variant_def = &tcx.adt_def(adt_did).variant(variant);
2771 let substs = tcx.lift(substs).expect("could not lift for printing");
2772 let name = FmtPrinter::new(tcx, Namespace::ValueNS)
2773 .print_def_path(variant_def.def_id, substs)?
2776 match variant_def.ctor_kind {
2777 CtorKind::Const => fmt.write_str(&name),
2778 CtorKind::Fn => fmt_tuple(fmt, &name),
2779 CtorKind::Fictive => {
2780 let mut struct_fmt = fmt.debug_struct(&name);
2781 for (field, place) in iter::zip(&variant_def.fields, places) {
2782 struct_fmt.field(field.name.as_str(), place);
2790 AggregateKind::Closure(def_id, substs) => ty::tls::with(|tcx| {
2791 if let Some(def_id) = def_id.as_local() {
2792 let name = if tcx.sess.opts.debugging_opts.span_free_formats {
2793 let substs = tcx.lift(substs).unwrap();
2796 tcx.def_path_str_with_substs(def_id.to_def_id(), substs),
2799 let span = tcx.def_span(def_id);
2802 tcx.sess.source_map().span_to_diagnostic_string(span)
2805 let mut struct_fmt = fmt.debug_struct(&name);
2807 // FIXME(project-rfc-2229#48): This should be a list of capture names/places
2808 if let Some(upvars) = tcx.upvars_mentioned(def_id) {
2809 for (&var_id, place) in iter::zip(upvars.keys(), places) {
2810 let var_name = tcx.hir().name(var_id);
2811 struct_fmt.field(var_name.as_str(), place);
2817 write!(fmt, "[closure]")
2821 AggregateKind::Generator(def_id, _, _) => ty::tls::with(|tcx| {
2822 if let Some(def_id) = def_id.as_local() {
2823 let name = format!("[generator@{:?}]", tcx.def_span(def_id));
2824 let mut struct_fmt = fmt.debug_struct(&name);
2826 // FIXME(project-rfc-2229#48): This should be a list of capture names/places
2827 if let Some(upvars) = tcx.upvars_mentioned(def_id) {
2828 for (&var_id, place) in iter::zip(upvars.keys(), places) {
2829 let var_name = tcx.hir().name(var_id);
2830 struct_fmt.field(var_name.as_str(), place);
2836 write!(fmt, "[generator]")
2842 ShallowInitBox(ref place, ref ty) => {
2843 write!(fmt, "ShallowInitBox({:?}, {:?})", place, ty)
2849 ///////////////////////////////////////////////////////////////////////////
2852 /// Two constants are equal if they are the same constant. Note that
2853 /// this does not necessarily mean that they are `==` in Rust. In
2854 /// particular, one must be wary of `NaN`!
2856 #[derive(Clone, Copy, PartialEq, TyEncodable, TyDecodable, Hash, HashStable)]
2857 pub struct Constant<'tcx> {
2860 /// Optional user-given type: for something like
2861 /// `collect::<Vec<_>>`, this would be present and would
2862 /// indicate that `Vec<_>` was explicitly specified.
2864 /// Needed for NLL to impose user-given type constraints.
2865 pub user_ty: Option<UserTypeAnnotationIndex>,
2867 pub literal: ConstantKind<'tcx>,
2870 #[derive(Clone, Copy, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable, Debug)]
2872 pub enum ConstantKind<'tcx> {
2873 /// This constant came from the type system
2874 Ty(ty::Const<'tcx>),
2875 /// This constant cannot go back into the type system, as it represents
2876 /// something the type system cannot handle (e.g. pointers).
2877 Val(interpret::ConstValue<'tcx>, Ty<'tcx>),
2880 impl<'tcx> Constant<'tcx> {
2881 pub fn check_static_ptr(&self, tcx: TyCtxt<'_>) -> Option<DefId> {
2882 match self.literal.try_to_scalar() {
2883 Some(Scalar::Ptr(ptr, _size)) => match tcx.global_alloc(ptr.provenance) {
2884 GlobalAlloc::Static(def_id) => {
2885 assert!(!tcx.is_thread_local_static(def_id));
2894 pub fn ty(&self) -> Ty<'tcx> {
2899 impl<'tcx> From<ty::Const<'tcx>> for ConstantKind<'tcx> {
2901 fn from(ct: ty::Const<'tcx>) -> Self {
2903 ty::ConstKind::Value(cv) => {
2904 // FIXME Once valtrees are introduced we need to convert those
2905 // into `ConstValue` instances here
2906 Self::Val(cv, ct.ty())
2913 impl<'tcx> ConstantKind<'tcx> {
2914 /// Returns `None` if the constant is not trivially safe for use in the type system.
2915 pub fn const_for_ty(&self) -> Option<ty::Const<'tcx>> {
2917 ConstantKind::Ty(c) => Some(*c),
2918 ConstantKind::Val(..) => None,
2922 pub fn ty(&self) -> Ty<'tcx> {
2924 ConstantKind::Ty(c) => c.ty(),
2925 ConstantKind::Val(_, ty) => *ty,
2929 pub fn try_val(&self) -> Option<ConstValue<'tcx>> {
2931 ConstantKind::Ty(c) => match c.val() {
2932 ty::ConstKind::Value(v) => Some(v),
2935 ConstantKind::Val(v, _) => Some(*v),
2940 pub fn try_to_value(self) -> Option<interpret::ConstValue<'tcx>> {
2942 ConstantKind::Ty(c) => c.val().try_to_value(),
2943 ConstantKind::Val(val, _) => Some(val),
2948 pub fn try_to_scalar(self) -> Option<Scalar> {
2949 self.try_to_value()?.try_to_scalar()
2953 pub fn try_to_scalar_int(self) -> Option<ScalarInt> {
2954 Some(self.try_to_value()?.try_to_scalar()?.assert_int())
2958 pub fn try_to_bits(self, size: Size) -> Option<u128> {
2959 self.try_to_scalar_int()?.to_bits(size).ok()
2963 pub fn try_to_bool(self) -> Option<bool> {
2964 self.try_to_scalar_int()?.try_into().ok()
2968 pub fn eval(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Self {
2971 // FIXME Need to use a different evaluation function that directly returns a `ConstValue`
2972 // if evaluation succeeds and does not create a ValTree first
2973 if let Some(val) = c.val().try_eval(tcx, param_env) {
2975 Ok(val) => Self::Val(val, c.ty()),
2976 Err(_) => Self::Ty(tcx.const_error(self.ty())),
2982 Self::Val(_, _) => self,
2986 /// Panics if the value cannot be evaluated or doesn't contain a valid integer of the given type.
2988 pub fn eval_bits(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>, ty: Ty<'tcx>) -> u128 {
2989 self.try_eval_bits(tcx, param_env, ty)
2990 .unwrap_or_else(|| bug!("expected bits of {:#?}, got {:#?}", ty, self))
2994 pub fn try_eval_bits(
2997 param_env: ty::ParamEnv<'tcx>,
3001 Self::Ty(ct) => ct.try_eval_bits(tcx, param_env, ty),
3002 Self::Val(val, t) => {
3005 tcx.layout_of(param_env.with_reveal_all_normalized(tcx).and(ty)).ok()?.size;
3006 val.try_to_bits(size)
3012 pub fn try_eval_bool(&self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Option<bool> {
3014 Self::Ty(ct) => ct.try_eval_bool(tcx, param_env),
3015 Self::Val(val, _) => val.try_to_bool(),
3020 pub fn try_eval_usize(&self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Option<u64> {
3022 Self::Ty(ct) => ct.try_eval_usize(tcx, param_env),
3023 Self::Val(val, _) => val.try_to_machine_usize(tcx),
3030 param_env_ty: ty::ParamEnvAnd<'tcx, Ty<'tcx>>,
3033 .layout_of(param_env_ty)
3034 .unwrap_or_else(|e| {
3035 bug!("could not compute layout for {:?}: {:?}", param_env_ty.value, e)
3038 let cv = ConstValue::Scalar(Scalar::from_uint(bits, size));
3040 Self::Val(cv, param_env_ty.value)
3043 pub fn from_bool(tcx: TyCtxt<'tcx>, v: bool) -> Self {
3044 let cv = ConstValue::from_bool(v);
3045 Self::Val(cv, tcx.types.bool)
3048 pub fn zero_sized(ty: Ty<'tcx>) -> Self {
3049 let cv = ConstValue::Scalar(Scalar::ZST);
3053 pub fn from_usize(tcx: TyCtxt<'tcx>, n: u64) -> Self {
3054 let ty = tcx.types.usize;
3055 Self::from_bits(tcx, n as u128, ty::ParamEnv::empty().and(ty))
3058 /// Literals are converted to `ConstantKindVal`, const generic parameters are eagerly
3059 /// converted to a constant, everything else becomes `Unevaluated`.
3060 pub fn from_anon_const(
3063 param_env: ty::ParamEnv<'tcx>,
3065 Self::from_opt_const_arg_anon_const(tcx, ty::WithOptConstParam::unknown(def_id), param_env)
3068 #[instrument(skip(tcx), level = "debug")]
3069 fn from_opt_const_arg_anon_const(
3071 def: ty::WithOptConstParam<LocalDefId>,
3072 param_env: ty::ParamEnv<'tcx>,
3074 let body_id = match tcx.hir().get_by_def_id(def.did) {
3075 hir::Node::AnonConst(ac) => ac.body,
3077 tcx.def_span(def.did.to_def_id()),
3078 "from_anon_const can only process anonymous constants"
3082 let expr = &tcx.hir().body(body_id).value;
3085 // Unwrap a block, so that e.g. `{ P }` is recognised as a parameter. Const arguments
3086 // currently have to be wrapped in curly brackets, so it's necessary to special-case.
3087 let expr = match &expr.kind {
3088 hir::ExprKind::Block(block, _) if block.stmts.is_empty() && block.expr.is_some() => {
3089 block.expr.as_ref().unwrap()
3094 let ty = tcx.type_of(def.def_id_for_type_of());
3096 // FIXME(const_generics): We currently have to special case parameters because `min_const_generics`
3097 // does not provide the parents generics to anonymous constants. We still allow generic const
3098 // parameters by themselves however, e.g. `N`. These constants would cause an ICE if we were to
3099 // ever try to substitute the generic parameters in their bodies.
3101 // While this doesn't happen as these constants are always used as `ty::ConstKind::Param`, it does
3102 // cause issues if we were to remove that special-case and try to evaluate the constant instead.
3103 use hir::{def::DefKind::ConstParam, def::Res, ExprKind, Path, QPath};
3105 ExprKind::Path(QPath::Resolved(_, &Path { res: Res::Def(ConstParam, def_id), .. })) => {
3106 // Find the name and index of the const parameter by indexing the generics of
3107 // the parent item and construct a `ParamConst`.
3108 let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
3109 let item_id = tcx.hir().get_parent_node(hir_id);
3110 let item_def_id = tcx.hir().local_def_id(item_id);
3111 let generics = tcx.generics_of(item_def_id.to_def_id());
3112 let index = generics.param_def_id_to_index[&def_id];
3113 let name = tcx.hir().name(hir_id);
3114 let ty_const = tcx.mk_const(ty::ConstS {
3115 val: ty::ConstKind::Param(ty::ParamConst::new(index, name)),
3119 return Self::Ty(ty_const);
3124 let hir_id = tcx.hir().local_def_id_to_hir_id(def.did);
3125 let parent_substs = if let Some(parent_hir_id) = tcx.hir().find_parent_node(hir_id) {
3126 if let Some(parent_did) = tcx.hir().opt_local_def_id(parent_hir_id) {
3127 InternalSubsts::identity_for_item(tcx, parent_did.to_def_id())
3129 tcx.mk_substs(Vec::<GenericArg<'tcx>>::new().into_iter())
3132 tcx.mk_substs(Vec::<GenericArg<'tcx>>::new().into_iter())
3134 debug!(?parent_substs);
3136 let did = def.did.to_def_id();
3137 let child_substs = InternalSubsts::identity_for_item(tcx, did);
3138 let substs = tcx.mk_substs(parent_substs.into_iter().chain(child_substs.into_iter()));
3141 let hir_id = tcx.hir().local_def_id_to_hir_id(def.did);
3142 let span = tcx.hir().span(hir_id);
3143 let uneval = ty::Unevaluated::new(def.to_global(), substs);
3144 debug!(?span, ?param_env);
3146 match tcx.const_eval_resolve(param_env, uneval, Some(span)) {
3147 Ok(val) => Self::Val(val, ty),
3149 // Error was handled in `const_eval_resolve`. Here we just create a
3150 // new unevaluated const and error hard later in codegen
3151 let ty_const = tcx.mk_const(ty::ConstS {
3152 val: ty::ConstKind::Unevaluated(ty::Unevaluated {
3153 def: def.to_global(),
3154 substs: InternalSubsts::identity_for_item(tcx, def.did.to_def_id()),
3166 /// A collection of projections into user types.
3168 /// They are projections because a binding can occur a part of a
3169 /// parent pattern that has been ascribed a type.
3171 /// Its a collection because there can be multiple type ascriptions on
3172 /// the path from the root of the pattern down to the binding itself.
3177 /// struct S<'a>((i32, &'a str), String);
3178 /// let S((_, w): (i32, &'static str), _): S = ...;
3179 /// // ------ ^^^^^^^^^^^^^^^^^^^ (1)
3180 /// // --------------------------------- ^ (2)
3183 /// The highlights labelled `(1)` show the subpattern `(_, w)` being
3184 /// ascribed the type `(i32, &'static str)`.
3186 /// The highlights labelled `(2)` show the whole pattern being
3187 /// ascribed the type `S`.
3189 /// In this example, when we descend to `w`, we will have built up the
3190 /// following two projected types:
3192 /// * base: `S`, projection: `(base.0).1`
3193 /// * base: `(i32, &'static str)`, projection: `base.1`
3195 /// The first will lead to the constraint `w: &'1 str` (for some
3196 /// inferred region `'1`). The second will lead to the constraint `w:
3198 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
3199 pub struct UserTypeProjections {
3200 pub contents: Vec<(UserTypeProjection, Span)>,
3203 impl<'tcx> UserTypeProjections {
3204 pub fn none() -> Self {
3205 UserTypeProjections { contents: vec![] }
3208 pub fn is_empty(&self) -> bool {
3209 self.contents.is_empty()
3212 pub fn projections_and_spans(
3214 ) -> impl Iterator<Item = &(UserTypeProjection, Span)> + ExactSizeIterator {
3215 self.contents.iter()
3218 pub fn projections(&self) -> impl Iterator<Item = &UserTypeProjection> + ExactSizeIterator {
3219 self.contents.iter().map(|&(ref user_type, _span)| user_type)
3222 pub fn push_projection(mut self, user_ty: &UserTypeProjection, span: Span) -> Self {
3223 self.contents.push((user_ty.clone(), span));
3229 mut f: impl FnMut(UserTypeProjection) -> UserTypeProjection,
3231 self.contents = self.contents.into_iter().map(|(proj, span)| (f(proj), span)).collect();
3235 pub fn index(self) -> Self {
3236 self.map_projections(|pat_ty_proj| pat_ty_proj.index())
3239 pub fn subslice(self, from: u64, to: u64) -> Self {
3240 self.map_projections(|pat_ty_proj| pat_ty_proj.subslice(from, to))
3243 pub fn deref(self) -> Self {
3244 self.map_projections(|pat_ty_proj| pat_ty_proj.deref())
3247 pub fn leaf(self, field: Field) -> Self {
3248 self.map_projections(|pat_ty_proj| pat_ty_proj.leaf(field))
3251 pub fn variant(self, adt_def: AdtDef<'tcx>, variant_index: VariantIdx, field: Field) -> Self {
3252 self.map_projections(|pat_ty_proj| pat_ty_proj.variant(adt_def, variant_index, field))
3256 /// Encodes the effect of a user-supplied type annotation on the
3257 /// subcomponents of a pattern. The effect is determined by applying the
3258 /// given list of projections to some underlying base type. Often,
3259 /// the projection element list `projs` is empty, in which case this
3260 /// directly encodes a type in `base`. But in the case of complex patterns with
3261 /// subpatterns and bindings, we want to apply only a *part* of the type to a variable,
3262 /// in which case the `projs` vector is used.
3266 /// * `let x: T = ...` -- here, the `projs` vector is empty.
3268 /// * `let (x, _): T = ...` -- here, the `projs` vector would contain
3269 /// `field[0]` (aka `.0`), indicating that the type of `s` is
3270 /// determined by finding the type of the `.0` field from `T`.
3271 #[derive(Clone, Debug, TyEncodable, TyDecodable, Hash, HashStable, PartialEq)]
3272 pub struct UserTypeProjection {
3273 pub base: UserTypeAnnotationIndex,
3274 pub projs: Vec<ProjectionKind>,
3277 impl Copy for ProjectionKind {}
3279 impl UserTypeProjection {
3280 pub(crate) fn index(mut self) -> Self {
3281 self.projs.push(ProjectionElem::Index(()));
3285 pub(crate) fn subslice(mut self, from: u64, to: u64) -> Self {
3286 self.projs.push(ProjectionElem::Subslice { from, to, from_end: true });
3290 pub(crate) fn deref(mut self) -> Self {
3291 self.projs.push(ProjectionElem::Deref);
3295 pub(crate) fn leaf(mut self, field: Field) -> Self {
3296 self.projs.push(ProjectionElem::Field(field, ()));
3300 pub(crate) fn variant(
3302 adt_def: AdtDef<'_>,
3303 variant_index: VariantIdx,
3306 self.projs.push(ProjectionElem::Downcast(
3307 Some(adt_def.variant(variant_index).name),
3310 self.projs.push(ProjectionElem::Field(field, ()));
3315 TrivialTypeFoldableAndLiftImpls! { ProjectionKind, }
3317 impl<'tcx> TypeFoldable<'tcx> for UserTypeProjection {
3318 fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
3321 ) -> Result<Self, F::Error> {
3322 Ok(UserTypeProjection {
3323 base: self.base.try_fold_with(folder)?,
3324 projs: self.projs.try_fold_with(folder)?,
3328 fn super_visit_with<Vs: TypeVisitor<'tcx>>(
3331 ) -> ControlFlow<Vs::BreakTy> {
3332 self.base.visit_with(visitor)
3333 // Note: there's nothing in `self.proj` to visit.
3337 rustc_index::newtype_index! {
3338 pub struct Promoted {
3340 DEBUG_FORMAT = "promoted[{}]"
3344 impl<'tcx> Debug for Constant<'tcx> {
3345 fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
3346 write!(fmt, "{}", self)
3350 impl<'tcx> Display for Constant<'tcx> {
3351 fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
3352 match self.ty().kind() {
3354 _ => write!(fmt, "const ")?,
3356 Display::fmt(&self.literal, fmt)
3360 impl<'tcx> Display for ConstantKind<'tcx> {
3361 fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
3363 ConstantKind::Ty(c) => pretty_print_const(c, fmt, true),
3364 ConstantKind::Val(val, ty) => pretty_print_const_value(val, ty, fmt, true),
3369 fn pretty_print_const<'tcx>(
3371 fmt: &mut Formatter<'_>,
3374 use crate::ty::print::PrettyPrinter;
3375 ty::tls::with(|tcx| {
3376 let literal = tcx.lift(c).unwrap();
3377 let mut cx = FmtPrinter::new(tcx, Namespace::ValueNS);
3378 cx.print_alloc_ids = true;
3379 let cx = cx.pretty_print_const(literal, print_types)?;
3380 fmt.write_str(&cx.into_buffer())?;
3385 fn pretty_print_const_value<'tcx>(
3386 val: interpret::ConstValue<'tcx>,
3388 fmt: &mut Formatter<'_>,
3391 use crate::ty::print::PrettyPrinter;
3392 ty::tls::with(|tcx| {
3393 let val = tcx.lift(val).unwrap();
3394 let ty = tcx.lift(ty).unwrap();
3395 let mut cx = FmtPrinter::new(tcx, Namespace::ValueNS);
3396 cx.print_alloc_ids = true;
3397 let cx = cx.pretty_print_const_value(val, ty, print_types)?;
3398 fmt.write_str(&cx.into_buffer())?;
3403 impl<'tcx> graph::DirectedGraph for Body<'tcx> {
3404 type Node = BasicBlock;
3407 impl<'tcx> graph::WithNumNodes for Body<'tcx> {
3409 fn num_nodes(&self) -> usize {
3410 self.basic_blocks.len()
3414 impl<'tcx> graph::WithStartNode for Body<'tcx> {
3416 fn start_node(&self) -> Self::Node {
3421 impl<'tcx> graph::WithSuccessors for Body<'tcx> {
3423 fn successors(&self, node: Self::Node) -> <Self as GraphSuccessors<'_>>::Iter {
3424 self.basic_blocks[node].terminator().successors().cloned()
3428 impl<'a, 'b> graph::GraphSuccessors<'b> for Body<'a> {
3429 type Item = BasicBlock;
3430 type Iter = iter::Cloned<Successors<'b>>;
3433 impl<'tcx, 'graph> graph::GraphPredecessors<'graph> for Body<'tcx> {
3434 type Item = BasicBlock;
3435 type Iter = std::iter::Copied<std::slice::Iter<'graph, BasicBlock>>;
3438 impl<'tcx> graph::WithPredecessors for Body<'tcx> {
3440 fn predecessors(&self, node: Self::Node) -> <Self as graph::GraphPredecessors<'_>>::Iter {
3441 self.predecessors()[node].iter().copied()
3445 /// `Location` represents the position of the start of the statement; or, if
3446 /// `statement_index` equals the number of statements, then the start of the
3448 #[derive(Copy, Clone, PartialEq, Eq, Hash, Ord, PartialOrd, HashStable)]
3449 pub struct Location {
3450 /// The block that the location is within.
3451 pub block: BasicBlock,
3453 pub statement_index: usize,
3456 impl fmt::Debug for Location {
3457 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
3458 write!(fmt, "{:?}[{}]", self.block, self.statement_index)
3463 pub const START: Location = Location { block: START_BLOCK, statement_index: 0 };
3465 /// Returns the location immediately after this one within the enclosing block.
3467 /// Note that if this location represents a terminator, then the
3468 /// resulting location would be out of bounds and invalid.
3469 pub fn successor_within_block(&self) -> Location {
3470 Location { block: self.block, statement_index: self.statement_index + 1 }
3473 /// Returns `true` if `other` is earlier in the control flow graph than `self`.
3474 pub fn is_predecessor_of<'tcx>(&self, other: Location, body: &Body<'tcx>) -> bool {
3475 // If we are in the same block as the other location and are an earlier statement
3476 // then we are a predecessor of `other`.
3477 if self.block == other.block && self.statement_index < other.statement_index {
3481 let predecessors = body.predecessors();
3483 // If we're in another block, then we want to check that block is a predecessor of `other`.
3484 let mut queue: Vec<BasicBlock> = predecessors[other.block].to_vec();
3485 let mut visited = FxHashSet::default();
3487 while let Some(block) = queue.pop() {
3488 // If we haven't visited this block before, then make sure we visit its predecessors.
3489 if visited.insert(block) {
3490 queue.extend(predecessors[block].iter().cloned());
3495 // If we found the block that `self` is in, then we are a predecessor of `other` (since
3496 // we found that block by looking at the predecessors of `other`).
3497 if self.block == block {
3505 pub fn dominates(&self, other: Location, dominators: &Dominators<BasicBlock>) -> bool {
3506 if self.block == other.block {
3507 self.statement_index <= other.statement_index
3509 dominators.is_dominated_by(other.block, self.block)