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 use crate::mir::traversal::PostorderCache;
66 pub use terminator::*;
72 pub use self::generic_graph::graphviz_safe_def_name;
73 pub use self::graphviz::write_mir_graphviz;
74 pub use self::pretty::{
75 create_dump_file, display_allocation, dump_enabled, dump_mir, write_mir_pretty, PassWhere,
79 pub type LocalDecls<'tcx> = IndexVec<Local, LocalDecl<'tcx>>;
81 pub trait HasLocalDecls<'tcx> {
82 fn local_decls(&self) -> &LocalDecls<'tcx>;
85 impl<'tcx> HasLocalDecls<'tcx> for LocalDecls<'tcx> {
87 fn local_decls(&self) -> &LocalDecls<'tcx> {
92 impl<'tcx> HasLocalDecls<'tcx> for Body<'tcx> {
94 fn local_decls(&self) -> &LocalDecls<'tcx> {
99 /// A streamlined trait that you can implement to create a pass; the
100 /// pass will be named after the type, and it will consist of a main
101 /// loop that goes over each available MIR and applies `run_pass`.
102 pub trait MirPass<'tcx> {
103 fn name(&self) -> Cow<'_, str> {
104 let name = std::any::type_name::<Self>();
105 if let Some(tail) = name.rfind(':') {
106 Cow::from(&name[tail + 1..])
112 /// Returns `true` if this pass is enabled with the current combination of compiler flags.
113 fn is_enabled(&self, _sess: &Session) -> bool {
117 fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>);
119 /// If this pass causes the MIR to enter a new phase, return that phase.
120 fn phase_change(&self) -> Option<MirPhase> {
124 fn is_mir_dump_enabled(&self) -> bool {
129 /// The various "big phases" that MIR goes through.
131 /// These phases all describe dialects of MIR. Since all MIR uses the same datastructures, the
132 /// dialects forbid certain variants or values in certain phases. The sections below summarize the
133 /// changes, but do not document them thoroughly. The full documentation is found in the appropriate
134 /// documentation for the thing the change is affecting.
136 /// Warning: ordering of variants is significant.
137 #[derive(Copy, Clone, TyEncodable, TyDecodable, Debug, PartialEq, Eq, PartialOrd, Ord)]
138 #[derive(HashStable)]
140 /// The dialect of MIR used during all phases before `DropsLowered` is the same. This is also
141 /// the MIR that analysis such as borrowck uses.
143 /// One important thing to remember about the behavior of this section of MIR is that drop terminators
144 /// (including drop and replace) are *conditional*. The elaborate drops pass will then replace each
145 /// instance of a drop terminator with a nop, an unconditional drop, or a drop conditioned on a drop
146 /// flag. Of course, this means that it is important that the drop elaboration can accurately recognize
147 /// when things are initialized and when things are de-initialized. That means any code running on this
148 /// version of MIR must be sure to produce output that drop elaboration can reason about. See the
149 /// section on the drop terminatorss for more details.
151 // FIXME(oli-obk): it's unclear whether we still need this phase (and its corresponding query).
152 // We used to have this for pre-miri MIR based const eval.
154 /// This phase checks the MIR for promotable elements and takes them out of the main MIR body
155 /// by creating a new MIR body per promoted element. After this phase (and thus the termination
156 /// of the `mir_promoted` query), these promoted elements are available in the `promoted_mir`
159 /// Beginning with this phase, the following variants are disallowed:
160 /// * [`TerminatorKind::DropAndReplace`](terminator::TerminatorKind::DropAndReplace)
161 /// * [`TerminatorKind::FalseUnwind`](terminator::TerminatorKind::FalseUnwind)
162 /// * [`TerminatorKind::FalseEdge`](terminator::TerminatorKind::FalseEdge)
163 /// * [`StatementKind::FakeRead`]
164 /// * [`StatementKind::AscribeUserType`]
165 /// * [`Rvalue::Ref`] with `BorrowKind::Shallow`
167 /// And the following variant is allowed:
168 /// * [`StatementKind::Retag`]
170 /// Furthermore, `Drop` now uses explicit drop flags visible in the MIR and reaching a `Drop`
171 /// terminator means that the auto-generated drop glue will be invoked. Also, `Copy` operands
172 /// are allowed for non-`Copy` types.
174 /// Beginning with this phase, the following variant is disallowed:
175 /// * [`Rvalue::Aggregate`] for any `AggregateKind` except `Array`
177 /// And the following variant is allowed:
178 /// * [`StatementKind::SetDiscriminant`]
180 /// Before this phase, generators are in the "source code" form, featuring `yield` statements
181 /// and such. With this phase change, they are transformed into a proper state machine. Running
182 /// optimizations before this change can be potentially dangerous because the source code is to
183 /// some extent a "lie." In particular, `yield` terminators effectively make the value of all
184 /// locals visible to the caller. This means that dead store elimination before them, or code
185 /// motion across them, is not correct in general. This is also exasperated by type checking
186 /// having pre-computed a list of the types that it thinks are ok to be live across a yield
187 /// point - this is necessary to decide eg whether autotraits are implemented. Introducing new
188 /// types across a yield point will lead to ICEs becaues of this.
190 /// Beginning with this phase, the following variants are disallowed:
191 /// * [`TerminatorKind::Yield`](terminator::TerminatorKind::Yield)
192 /// * [`TerminatorKind::GeneratorDrop](terminator::TerminatorKind::GeneratorDrop)
193 GeneratorsLowered = 5,
198 /// Gets the index of the current MirPhase within the set of all `MirPhase`s.
199 pub fn phase_index(&self) -> usize {
204 /// Where a specific `mir::Body` comes from.
205 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
206 #[derive(HashStable, TyEncodable, TyDecodable, TypeFoldable)]
207 pub struct MirSource<'tcx> {
208 pub instance: InstanceDef<'tcx>,
210 /// If `Some`, this is a promoted rvalue within the parent function.
211 pub promoted: Option<Promoted>,
214 impl<'tcx> MirSource<'tcx> {
215 pub fn item(def_id: DefId) -> Self {
217 instance: InstanceDef::Item(ty::WithOptConstParam::unknown(def_id)),
222 pub fn from_instance(instance: InstanceDef<'tcx>) -> Self {
223 MirSource { instance, promoted: None }
226 pub fn with_opt_param(self) -> ty::WithOptConstParam<DefId> {
227 self.instance.with_opt_param()
231 pub fn def_id(&self) -> DefId {
232 self.instance.def_id()
236 #[derive(Clone, TyEncodable, TyDecodable, Debug, HashStable, TypeFoldable)]
237 pub struct GeneratorInfo<'tcx> {
238 /// The yield type of the function, if it is a generator.
239 pub yield_ty: Option<Ty<'tcx>>,
241 /// Generator drop glue.
242 pub generator_drop: Option<Body<'tcx>>,
244 /// The layout of a generator. Produced by the state transformation.
245 pub generator_layout: Option<GeneratorLayout<'tcx>>,
247 /// If this is a generator then record the type of source expression that caused this generator
249 pub generator_kind: GeneratorKind,
252 /// The lowered representation of a single function.
253 #[derive(Clone, TyEncodable, TyDecodable, Debug, HashStable, TypeFoldable)]
254 pub struct Body<'tcx> {
255 /// A list of basic blocks. References to basic block use a newtyped index type [`BasicBlock`]
256 /// that indexes into this vector.
257 basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,
259 /// Records how far through the "desugaring and optimization" process this particular
260 /// MIR has traversed. This is particularly useful when inlining, since in that context
261 /// we instantiate the promoted constants and add them to our promoted vector -- but those
262 /// promoted items have already been optimized, whereas ours have not. This field allows
263 /// us to see the difference and forego optimization on the inlined promoted items.
266 pub source: MirSource<'tcx>,
268 /// A list of source scopes; these are referenced by statements
269 /// and used for debuginfo. Indexed by a `SourceScope`.
270 pub source_scopes: IndexVec<SourceScope, SourceScopeData<'tcx>>,
272 pub generator: Option<Box<GeneratorInfo<'tcx>>>,
274 /// Declarations of locals.
276 /// The first local is the return value pointer, followed by `arg_count`
277 /// locals for the function arguments, followed by any user-declared
278 /// variables and temporaries.
279 pub local_decls: LocalDecls<'tcx>,
281 /// User type annotations.
282 pub user_type_annotations: ty::CanonicalUserTypeAnnotations<'tcx>,
284 /// The number of arguments this function takes.
286 /// Starting at local 1, `arg_count` locals will be provided by the caller
287 /// and can be assumed to be initialized.
289 /// If this MIR was built for a constant, this will be 0.
290 pub arg_count: usize,
292 /// Mark an argument local (which must be a tuple) as getting passed as
293 /// its individual components at the LLVM level.
295 /// This is used for the "rust-call" ABI.
296 pub spread_arg: Option<Local>,
298 /// Debug information pertaining to user variables, including captures.
299 pub var_debug_info: Vec<VarDebugInfo<'tcx>>,
301 /// A span representing this MIR, for error reporting.
304 /// Constants that are required to evaluate successfully for this MIR to be well-formed.
305 /// We hold in this field all the constants we are not able to evaluate yet.
306 pub required_consts: Vec<Constant<'tcx>>,
308 /// Does this body use generic parameters. This is used for the `ConstEvaluatable` check.
310 /// Note that this does not actually mean that this body is not computable right now.
311 /// The repeat count in the following example is polymorphic, but can still be evaluated
312 /// without knowing anything about the type parameter `T`.
316 /// let _ = [0; std::mem::size_of::<*mut T>()];
320 /// **WARNING**: Do not change this flags after the MIR was originally created, even if an optimization
321 /// removed the last mention of all generic params. We do not want to rely on optimizations and
322 /// potentially allow things like `[u8; std::mem::size_of::<T>() * 0]` due to this.
323 pub is_polymorphic: bool,
325 predecessor_cache: PredecessorCache,
326 switch_source_cache: SwitchSourceCache,
327 is_cyclic: GraphIsCyclicCache,
328 postorder_cache: PostorderCache,
330 pub tainted_by_errors: Option<ErrorGuaranteed>,
333 impl<'tcx> Body<'tcx> {
335 source: MirSource<'tcx>,
336 basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,
337 source_scopes: IndexVec<SourceScope, SourceScopeData<'tcx>>,
338 local_decls: LocalDecls<'tcx>,
339 user_type_annotations: ty::CanonicalUserTypeAnnotations<'tcx>,
341 var_debug_info: Vec<VarDebugInfo<'tcx>>,
343 generator_kind: Option<GeneratorKind>,
344 tainted_by_errors: Option<ErrorGuaranteed>,
346 // We need `arg_count` locals, and one for the return place.
348 local_decls.len() > arg_count,
349 "expected at least {} locals, got {}",
354 let mut body = Body {
355 phase: MirPhase::Built,
359 generator: generator_kind.map(|generator_kind| {
360 Box::new(GeneratorInfo {
362 generator_drop: None,
363 generator_layout: None,
368 user_type_annotations,
373 required_consts: Vec::new(),
374 is_polymorphic: false,
375 predecessor_cache: PredecessorCache::new(),
376 switch_source_cache: SwitchSourceCache::new(),
377 is_cyclic: GraphIsCyclicCache::new(),
378 postorder_cache: PostorderCache::new(),
381 body.is_polymorphic = body.has_param_types_or_consts();
385 /// Returns a partially initialized MIR body containing only a list of basic blocks.
387 /// The returned MIR contains no `LocalDecl`s (even for the return place) or source scopes. It
388 /// is only useful for testing but cannot be `#[cfg(test)]` because it is used in a different
390 pub fn new_cfg_only(basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>) -> Self {
391 let mut body = Body {
392 phase: MirPhase::Built,
393 source: MirSource::item(CRATE_DEF_ID.to_def_id()),
395 source_scopes: IndexVec::new(),
397 local_decls: IndexVec::new(),
398 user_type_annotations: IndexVec::new(),
402 required_consts: Vec::new(),
403 var_debug_info: Vec::new(),
404 is_polymorphic: false,
405 predecessor_cache: PredecessorCache::new(),
406 switch_source_cache: SwitchSourceCache::new(),
407 is_cyclic: GraphIsCyclicCache::new(),
408 postorder_cache: PostorderCache::new(),
409 tainted_by_errors: None,
411 body.is_polymorphic = body.has_param_types_or_consts();
416 pub fn basic_blocks(&self) -> &IndexVec<BasicBlock, BasicBlockData<'tcx>> {
421 pub fn basic_blocks_mut(&mut self) -> &mut IndexVec<BasicBlock, BasicBlockData<'tcx>> {
422 // Because the user could mutate basic block terminators via this reference, we need to
423 // invalidate the caches.
425 // FIXME: Use a finer-grained API for this, so only transformations that alter terminators
426 // invalidate the caches.
427 self.predecessor_cache.invalidate();
428 self.switch_source_cache.invalidate();
429 self.is_cyclic.invalidate();
430 self.postorder_cache.invalidate();
431 &mut self.basic_blocks
435 pub fn basic_blocks_and_local_decls_mut(
437 ) -> (&mut IndexVec<BasicBlock, BasicBlockData<'tcx>>, &mut LocalDecls<'tcx>) {
438 self.predecessor_cache.invalidate();
439 self.switch_source_cache.invalidate();
440 self.is_cyclic.invalidate();
441 self.postorder_cache.invalidate();
442 (&mut self.basic_blocks, &mut self.local_decls)
446 pub fn basic_blocks_local_decls_mut_and_var_debug_info(
449 &mut IndexVec<BasicBlock, BasicBlockData<'tcx>>,
450 &mut LocalDecls<'tcx>,
451 &mut Vec<VarDebugInfo<'tcx>>,
453 self.predecessor_cache.invalidate();
454 self.switch_source_cache.invalidate();
455 self.is_cyclic.invalidate();
456 self.postorder_cache.invalidate();
457 (&mut self.basic_blocks, &mut self.local_decls, &mut self.var_debug_info)
460 /// Returns `true` if a cycle exists in the control-flow graph that is reachable from the
462 pub fn is_cfg_cyclic(&self) -> bool {
463 self.is_cyclic.is_cyclic(self)
467 pub fn local_kind(&self, local: Local) -> LocalKind {
468 let index = local.as_usize();
471 self.local_decls[local].mutability == Mutability::Mut,
472 "return place should be mutable"
475 LocalKind::ReturnPointer
476 } else if index < self.arg_count + 1 {
478 } else if self.local_decls[local].is_user_variable() {
485 /// Returns an iterator over all user-declared mutable locals.
487 pub fn mut_vars_iter<'a>(&'a self) -> impl Iterator<Item = Local> + 'a {
488 (self.arg_count + 1..self.local_decls.len()).filter_map(move |index| {
489 let local = Local::new(index);
490 let decl = &self.local_decls[local];
491 if decl.is_user_variable() && decl.mutability == Mutability::Mut {
499 /// Returns an iterator over all user-declared mutable arguments and locals.
501 pub fn mut_vars_and_args_iter<'a>(&'a self) -> impl Iterator<Item = Local> + 'a {
502 (1..self.local_decls.len()).filter_map(move |index| {
503 let local = Local::new(index);
504 let decl = &self.local_decls[local];
505 if (decl.is_user_variable() || index < self.arg_count + 1)
506 && decl.mutability == Mutability::Mut
515 /// Returns an iterator over all function arguments.
517 pub fn args_iter(&self) -> impl Iterator<Item = Local> + ExactSizeIterator {
518 (1..self.arg_count + 1).map(Local::new)
521 /// Returns an iterator over all user-defined variables and compiler-generated temporaries (all
522 /// locals that are neither arguments nor the return place).
524 pub fn vars_and_temps_iter(
526 ) -> impl DoubleEndedIterator<Item = Local> + ExactSizeIterator {
527 (self.arg_count + 1..self.local_decls.len()).map(Local::new)
531 pub fn drain_vars_and_temps<'a>(&'a mut self) -> impl Iterator<Item = LocalDecl<'tcx>> + 'a {
532 self.local_decls.drain(self.arg_count + 1..)
535 /// Changes a statement to a nop. This is both faster than deleting instructions and avoids
536 /// invalidating statement indices in `Location`s.
537 pub fn make_statement_nop(&mut self, location: Location) {
538 let block = &mut self.basic_blocks[location.block];
539 debug_assert!(location.statement_index < block.statements.len());
540 block.statements[location.statement_index].make_nop()
543 /// Returns the source info associated with `location`.
544 pub fn source_info(&self, location: Location) -> &SourceInfo {
545 let block = &self[location.block];
546 let stmts = &block.statements;
547 let idx = location.statement_index;
548 if idx < stmts.len() {
549 &stmts[idx].source_info
551 assert_eq!(idx, stmts.len());
552 &block.terminator().source_info
556 /// Returns the return type; it always return first element from `local_decls` array.
558 pub fn return_ty(&self) -> Ty<'tcx> {
559 self.local_decls[RETURN_PLACE].ty
562 /// Gets the location of the terminator for the given block.
564 pub fn terminator_loc(&self, bb: BasicBlock) -> Location {
565 Location { block: bb, statement_index: self[bb].statements.len() }
568 pub fn stmt_at(&self, location: Location) -> Either<&Statement<'tcx>, &Terminator<'tcx>> {
569 let Location { block, statement_index } = location;
570 let block_data = &self.basic_blocks[block];
573 .get(statement_index)
575 .unwrap_or_else(|| Either::Right(block_data.terminator()))
579 pub fn predecessors(&self) -> &Predecessors {
580 self.predecessor_cache.compute(&self.basic_blocks)
584 pub fn switch_sources(&self) -> &SwitchSources {
585 self.switch_source_cache.compute(&self.basic_blocks)
589 pub fn dominators(&self) -> Dominators<BasicBlock> {
594 pub fn yield_ty(&self) -> Option<Ty<'tcx>> {
595 self.generator.as_ref().and_then(|generator| generator.yield_ty)
599 pub fn generator_layout(&self) -> Option<&GeneratorLayout<'tcx>> {
600 self.generator.as_ref().and_then(|generator| generator.generator_layout.as_ref())
604 pub fn generator_drop(&self) -> Option<&Body<'tcx>> {
605 self.generator.as_ref().and_then(|generator| generator.generator_drop.as_ref())
609 pub fn generator_kind(&self) -> Option<GeneratorKind> {
610 self.generator.as_ref().map(|generator| generator.generator_kind)
614 #[derive(Copy, Clone, PartialEq, Eq, Debug, TyEncodable, TyDecodable, HashStable)]
617 /// Unsafe because of compiler-generated unsafe code, like `await` desugaring
619 /// Unsafe because of an unsafe fn
621 /// Unsafe because of an `unsafe` block
622 ExplicitUnsafe(hir::HirId),
625 impl<'tcx> Index<BasicBlock> for Body<'tcx> {
626 type Output = BasicBlockData<'tcx>;
629 fn index(&self, index: BasicBlock) -> &BasicBlockData<'tcx> {
630 &self.basic_blocks()[index]
634 impl<'tcx> IndexMut<BasicBlock> for Body<'tcx> {
636 fn index_mut(&mut self, index: BasicBlock) -> &mut BasicBlockData<'tcx> {
637 &mut self.basic_blocks_mut()[index]
641 #[derive(Copy, Clone, Debug, HashStable, TypeFoldable)]
642 pub enum ClearCrossCrate<T> {
647 impl<T> ClearCrossCrate<T> {
648 pub fn as_ref(&self) -> ClearCrossCrate<&T> {
650 ClearCrossCrate::Clear => ClearCrossCrate::Clear,
651 ClearCrossCrate::Set(v) => ClearCrossCrate::Set(v),
655 pub fn assert_crate_local(self) -> T {
657 ClearCrossCrate::Clear => bug!("unwrapping cross-crate data"),
658 ClearCrossCrate::Set(v) => v,
663 const TAG_CLEAR_CROSS_CRATE_CLEAR: u8 = 0;
664 const TAG_CLEAR_CROSS_CRATE_SET: u8 = 1;
666 impl<'tcx, E: TyEncoder<'tcx>, T: Encodable<E>> Encodable<E> for ClearCrossCrate<T> {
668 fn encode(&self, e: &mut E) -> Result<(), E::Error> {
669 if E::CLEAR_CROSS_CRATE {
674 ClearCrossCrate::Clear => TAG_CLEAR_CROSS_CRATE_CLEAR.encode(e),
675 ClearCrossCrate::Set(ref val) => {
676 TAG_CLEAR_CROSS_CRATE_SET.encode(e)?;
682 impl<'tcx, D: TyDecoder<'tcx>, T: Decodable<D>> Decodable<D> for ClearCrossCrate<T> {
684 fn decode(d: &mut D) -> ClearCrossCrate<T> {
685 if D::CLEAR_CROSS_CRATE {
686 return ClearCrossCrate::Clear;
689 let discr = u8::decode(d);
692 TAG_CLEAR_CROSS_CRATE_CLEAR => ClearCrossCrate::Clear,
693 TAG_CLEAR_CROSS_CRATE_SET => {
694 let val = T::decode(d);
695 ClearCrossCrate::Set(val)
697 tag => panic!("Invalid tag for ClearCrossCrate: {:?}", tag),
702 /// Grouped information about the source code origin of a MIR entity.
703 /// Intended to be inspected by diagnostics and debuginfo.
704 /// Most passes can work with it as a whole, within a single function.
705 // The unofficial Cranelift backend, at least as of #65828, needs `SourceInfo` to implement `Eq` and
706 // `Hash`. Please ping @bjorn3 if removing them.
707 #[derive(Copy, Clone, Debug, Eq, PartialEq, TyEncodable, TyDecodable, Hash, HashStable)]
708 pub struct SourceInfo {
709 /// The source span for the AST pertaining to this MIR entity.
712 /// The source scope, keeping track of which bindings can be
713 /// seen by debuginfo, active lint levels, `unsafe {...}`, etc.
714 pub scope: SourceScope,
719 pub fn outermost(span: Span) -> Self {
720 SourceInfo { span, scope: OUTERMOST_SOURCE_SCOPE }
724 ///////////////////////////////////////////////////////////////////////////
727 #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, TyEncodable, TyDecodable)]
728 #[derive(Hash, HashStable)]
729 pub enum BorrowKind {
730 /// Data must be immutable and is aliasable.
733 /// The immediately borrowed place must be immutable, but projections from
734 /// it don't need to be. For example, a shallow borrow of `a.b` doesn't
735 /// conflict with a mutable borrow of `a.b.c`.
737 /// This is used when lowering matches: when matching on a place we want to
738 /// ensure that place have the same value from the start of the match until
739 /// an arm is selected. This prevents this code from compiling:
740 /// ```compile_fail,E0510
741 /// let mut x = &Some(0);
744 /// Some(_) if { x = &None; false } => (),
748 /// This can't be a shared borrow because mutably borrowing (*x as Some).0
749 /// should not prevent `if let None = x { ... }`, for example, because the
750 /// mutating `(*x as Some).0` can't affect the discriminant of `x`.
751 /// We can also report errors with this kind of borrow differently.
754 /// Data must be immutable but not aliasable. This kind of borrow
755 /// cannot currently be expressed by the user and is used only in
756 /// implicit closure bindings. It is needed when the closure is
757 /// borrowing or mutating a mutable referent, e.g.:
760 /// let x: &mut isize = &mut z;
761 /// let y = || *x += 5;
763 /// If we were to try to translate this closure into a more explicit
764 /// form, we'd encounter an error with the code as written:
765 /// ```compile_fail,E0594
766 /// struct Env<'a> { x: &'a &'a mut isize }
768 /// let x: &mut isize = &mut z;
769 /// let y = (&mut Env { x: &x }, fn_ptr); // Closure is pair of env and fn
770 /// fn fn_ptr(env: &mut Env) { **env.x += 5; }
772 /// This is then illegal because you cannot mutate an `&mut` found
773 /// in an aliasable location. To solve, you'd have to translate with
774 /// an `&mut` borrow:
775 /// ```compile_fail,E0596
776 /// struct Env<'a> { x: &'a mut &'a mut isize }
778 /// let x: &mut isize = &mut z;
779 /// let y = (&mut Env { x: &mut x }, fn_ptr); // changed from &x to &mut x
780 /// fn fn_ptr(env: &mut Env) { **env.x += 5; }
782 /// Now the assignment to `**env.x` is legal, but creating a
783 /// mutable pointer to `x` is not because `x` is not mutable. We
784 /// could fix this by declaring `x` as `let mut x`. This is ok in
785 /// user code, if awkward, but extra weird for closures, since the
786 /// borrow is hidden.
788 /// So we introduce a "unique imm" borrow -- the referent is
789 /// immutable, but not aliasable. This solves the problem. For
790 /// simplicity, we don't give users the way to express this
791 /// borrow, it's just used when translating closures.
794 /// Data is mutable and not aliasable.
796 /// `true` if this borrow arose from method-call auto-ref
797 /// (i.e., `adjustment::Adjust::Borrow`).
798 allow_two_phase_borrow: bool,
803 pub fn allows_two_phase_borrow(&self) -> bool {
805 BorrowKind::Shared | BorrowKind::Shallow | BorrowKind::Unique => false,
806 BorrowKind::Mut { allow_two_phase_borrow } => allow_two_phase_borrow,
810 pub fn describe_mutability(&self) -> String {
812 BorrowKind::Shared | BorrowKind::Shallow | BorrowKind::Unique => {
813 "immutable".to_string()
815 BorrowKind::Mut { .. } => "mutable".to_string(),
820 ///////////////////////////////////////////////////////////////////////////
821 // Variables and temps
823 rustc_index::newtype_index! {
826 DEBUG_FORMAT = "_{}",
827 const RETURN_PLACE = 0,
831 impl Atom for Local {
832 fn index(self) -> usize {
837 /// Classifies locals into categories. See `Body::local_kind`.
838 #[derive(Clone, Copy, PartialEq, Eq, Debug, HashStable)]
840 /// User-declared variable binding.
842 /// Compiler-introduced temporary.
844 /// Function argument.
846 /// Location of function's return value.
850 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
851 pub struct VarBindingForm<'tcx> {
852 /// Is variable bound via `x`, `mut x`, `ref x`, or `ref mut x`?
853 pub binding_mode: ty::BindingMode,
854 /// If an explicit type was provided for this variable binding,
855 /// this holds the source Span of that type.
857 /// NOTE: if you want to change this to a `HirId`, be wary that
858 /// doing so breaks incremental compilation (as of this writing),
859 /// while a `Span` does not cause our tests to fail.
860 pub opt_ty_info: Option<Span>,
861 /// Place of the RHS of the =, or the subject of the `match` where this
862 /// variable is initialized. None in the case of `let PATTERN;`.
863 /// Some((None, ..)) in the case of and `let [mut] x = ...` because
864 /// (a) the right-hand side isn't evaluated as a place expression.
865 /// (b) it gives a way to separate this case from the remaining cases
867 pub opt_match_place: Option<(Option<Place<'tcx>>, Span)>,
868 /// The span of the pattern in which this variable was bound.
872 #[derive(Clone, Debug, TyEncodable, TyDecodable)]
873 pub enum BindingForm<'tcx> {
874 /// This is a binding for a non-`self` binding, or a `self` that has an explicit type.
875 Var(VarBindingForm<'tcx>),
876 /// Binding for a `self`/`&self`/`&mut self` binding where the type is implicit.
877 ImplicitSelf(ImplicitSelfKind),
878 /// Reference used in a guard expression to ensure immutability.
882 /// Represents what type of implicit self a function has, if any.
883 #[derive(Clone, Copy, PartialEq, Debug, TyEncodable, TyDecodable, HashStable)]
884 pub enum ImplicitSelfKind {
885 /// Represents a `fn x(self);`.
887 /// Represents a `fn x(mut self);`.
889 /// Represents a `fn x(&self);`.
891 /// Represents a `fn x(&mut self);`.
893 /// Represents when a function does not have a self argument or
894 /// when a function has a `self: X` argument.
898 TrivialTypeFoldableAndLiftImpls! { BindingForm<'tcx>, }
900 mod binding_form_impl {
901 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
902 use rustc_query_system::ich::StableHashingContext;
904 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for super::BindingForm<'tcx> {
905 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
906 use super::BindingForm::*;
907 std::mem::discriminant(self).hash_stable(hcx, hasher);
910 Var(binding) => binding.hash_stable(hcx, hasher),
911 ImplicitSelf(kind) => kind.hash_stable(hcx, hasher),
918 /// `BlockTailInfo` is attached to the `LocalDecl` for temporaries
919 /// created during evaluation of expressions in a block tail
920 /// expression; that is, a block like `{ STMT_1; STMT_2; EXPR }`.
922 /// It is used to improve diagnostics when such temporaries are
923 /// involved in borrow_check errors, e.g., explanations of where the
924 /// temporaries come from, when their destructors are run, and/or how
925 /// one might revise the code to satisfy the borrow checker's rules.
926 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
927 pub struct BlockTailInfo {
928 /// If `true`, then the value resulting from evaluating this tail
929 /// expression is ignored by the block's expression context.
931 /// Examples include `{ ...; tail };` and `let _ = { ...; tail };`
932 /// but not e.g., `let _x = { ...; tail };`
933 pub tail_result_is_ignored: bool,
935 /// `Span` of the tail expression.
941 /// This can be a binding declared by the user, a temporary inserted by the compiler, a function
942 /// argument, or the return place.
943 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
944 pub struct LocalDecl<'tcx> {
945 /// Whether this is a mutable binding (i.e., `let x` or `let mut x`).
947 /// Temporaries and the return place are always mutable.
948 pub mutability: Mutability,
950 // FIXME(matthewjasper) Don't store in this in `Body`
951 pub local_info: Option<Box<LocalInfo<'tcx>>>,
953 /// `true` if this is an internal local.
955 /// These locals are not based on types in the source code and are only used
956 /// for a few desugarings at the moment.
958 /// The generator transformation will sanity check the locals which are live
959 /// across a suspension point against the type components of the generator
960 /// which type checking knows are live across a suspension point. We need to
961 /// flag drop flags to avoid triggering this check as they are introduced
962 /// outside of type inference.
964 /// This should be sound because the drop flags are fully algebraic, and
965 /// therefore don't affect the auto-trait or outlives properties of the
969 /// If this local is a temporary and `is_block_tail` is `Some`,
970 /// then it is a temporary created for evaluation of some
971 /// subexpression of some block's tail expression (with no
972 /// intervening statement context).
973 // FIXME(matthewjasper) Don't store in this in `Body`
974 pub is_block_tail: Option<BlockTailInfo>,
976 /// The type of this local.
979 /// If the user manually ascribed a type to this variable,
980 /// e.g., via `let x: T`, then we carry that type here. The MIR
981 /// borrow checker needs this information since it can affect
982 /// region inference.
983 // FIXME(matthewjasper) Don't store in this in `Body`
984 pub user_ty: Option<Box<UserTypeProjections>>,
986 /// The *syntactic* (i.e., not visibility) source scope the local is defined
987 /// in. If the local was defined in a let-statement, this
988 /// is *within* the let-statement, rather than outside
991 /// This is needed because the visibility source scope of locals within
992 /// a let-statement is weird.
994 /// The reason is that we want the local to be *within* the let-statement
995 /// for lint purposes, but we want the local to be *after* the let-statement
996 /// for names-in-scope purposes.
998 /// That's it, if we have a let-statement like the one in this
1002 /// fn foo(x: &str) {
1003 /// #[allow(unused_mut)]
1004 /// let mut x: u32 = { // <- one unused mut
1005 /// let mut y: u32 = x.parse().unwrap();
1012 /// Then, from a lint point of view, the declaration of `x: u32`
1013 /// (and `y: u32`) are within the `#[allow(unused_mut)]` scope - the
1014 /// lint scopes are the same as the AST/HIR nesting.
1016 /// However, from a name lookup point of view, the scopes look more like
1017 /// as if the let-statements were `match` expressions:
1020 /// fn foo(x: &str) {
1022 /// match x.parse::<u32>().unwrap() {
1031 /// We care about the name-lookup scopes for debuginfo - if the
1032 /// debuginfo instruction pointer is at the call to `x.parse()`, we
1033 /// want `x` to refer to `x: &str`, but if it is at the call to
1034 /// `drop(x)`, we want it to refer to `x: u32`.
1036 /// To allow both uses to work, we need to have more than a single scope
1037 /// for a local. We have the `source_info.scope` represent the "syntactic"
1038 /// lint scope (with a variable being under its let block) while the
1039 /// `var_debug_info.source_info.scope` represents the "local variable"
1040 /// scope (where the "rest" of a block is under all prior let-statements).
1042 /// The end result looks like this:
1046 /// │{ argument x: &str }
1048 /// │ │{ #[allow(unused_mut)] } // This is actually split into 2 scopes
1049 /// │ │ // in practice because I'm lazy.
1051 /// │ │← x.source_info.scope
1052 /// │ │← `x.parse().unwrap()`
1054 /// │ │ │← y.source_info.scope
1056 /// │ │ │{ let y: u32 }
1058 /// │ │ │← y.var_debug_info.source_info.scope
1061 /// │ │{ let x: u32 }
1062 /// │ │← x.var_debug_info.source_info.scope
1063 /// │ │← `drop(x)` // This accesses `x: u32`.
1065 pub source_info: SourceInfo,
1068 // `LocalDecl` is used a lot. Make sure it doesn't unintentionally get bigger.
1069 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
1070 static_assert_size!(LocalDecl<'_>, 56);
1072 /// Extra information about a some locals that's used for diagnostics and for
1073 /// classifying variables into local variables, statics, etc, which is needed e.g.
1074 /// for unsafety checking.
1076 /// Not used for non-StaticRef temporaries, the return place, or anonymous
1077 /// function parameters.
1078 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
1079 pub enum LocalInfo<'tcx> {
1080 /// A user-defined local variable or function parameter
1082 /// The `BindingForm` is solely used for local diagnostics when generating
1083 /// warnings/errors when compiling the current crate, and therefore it need
1084 /// not be visible across crates.
1085 User(ClearCrossCrate<BindingForm<'tcx>>),
1086 /// A temporary created that references the static with the given `DefId`.
1087 StaticRef { def_id: DefId, is_thread_local: bool },
1088 /// A temporary created that references the const with the given `DefId`
1089 ConstRef { def_id: DefId },
1090 /// A temporary created during the creation of an aggregate
1091 /// (e.g. a temporary for `foo` in `MyStruct { my_field: foo }`)
1095 impl<'tcx> LocalDecl<'tcx> {
1096 /// Returns `true` only if local is a binding that can itself be
1097 /// made mutable via the addition of the `mut` keyword, namely
1098 /// something like the occurrences of `x` in:
1099 /// - `fn foo(x: Type) { ... }`,
1100 /// - `let x = ...`,
1101 /// - or `match ... { C(x) => ... }`
1102 pub fn can_be_made_mutable(&self) -> bool {
1105 Some(box LocalInfo::User(ClearCrossCrate::Set(
1106 BindingForm::Var(VarBindingForm {
1107 binding_mode: ty::BindingMode::BindByValue(_),
1111 }) | BindingForm::ImplicitSelf(ImplicitSelfKind::Imm),
1116 /// Returns `true` if local is definitely not a `ref ident` or
1117 /// `ref mut ident` binding. (Such bindings cannot be made into
1118 /// mutable bindings, but the inverse does not necessarily hold).
1119 pub fn is_nonref_binding(&self) -> bool {
1122 Some(box LocalInfo::User(ClearCrossCrate::Set(
1123 BindingForm::Var(VarBindingForm {
1124 binding_mode: ty::BindingMode::BindByValue(_),
1128 }) | BindingForm::ImplicitSelf(_),
1133 /// Returns `true` if this variable is a named variable or function
1134 /// parameter declared by the user.
1136 pub fn is_user_variable(&self) -> bool {
1137 matches!(self.local_info, Some(box LocalInfo::User(_)))
1140 /// Returns `true` if this is a reference to a variable bound in a `match`
1141 /// expression that is used to access said variable for the guard of the
1143 pub fn is_ref_for_guard(&self) -> bool {
1146 Some(box LocalInfo::User(ClearCrossCrate::Set(BindingForm::RefForGuard)))
1150 /// Returns `Some` if this is a reference to a static item that is used to
1151 /// access that static.
1152 pub fn is_ref_to_static(&self) -> bool {
1153 matches!(self.local_info, Some(box LocalInfo::StaticRef { .. }))
1156 /// Returns `Some` if this is a reference to a thread-local static item that is used to
1157 /// access that static.
1158 pub fn is_ref_to_thread_local(&self) -> bool {
1159 match self.local_info {
1160 Some(box LocalInfo::StaticRef { is_thread_local, .. }) => is_thread_local,
1165 /// Returns `true` is the local is from a compiler desugaring, e.g.,
1166 /// `__next` from a `for` loop.
1168 pub fn from_compiler_desugaring(&self) -> bool {
1169 self.source_info.span.desugaring_kind().is_some()
1172 /// Creates a new `LocalDecl` for a temporary: mutable, non-internal.
1174 pub fn new(ty: Ty<'tcx>, span: Span) -> Self {
1175 Self::with_source_info(ty, SourceInfo::outermost(span))
1178 /// Like `LocalDecl::new`, but takes a `SourceInfo` instead of a `Span`.
1180 pub fn with_source_info(ty: Ty<'tcx>, source_info: SourceInfo) -> Self {
1182 mutability: Mutability::Mut,
1185 is_block_tail: None,
1192 /// Converts `self` into same `LocalDecl` except tagged as internal.
1194 pub fn internal(mut self) -> Self {
1195 self.internal = true;
1199 /// Converts `self` into same `LocalDecl` except tagged as immutable.
1201 pub fn immutable(mut self) -> Self {
1202 self.mutability = Mutability::Not;
1206 /// Converts `self` into same `LocalDecl` except tagged as internal temporary.
1208 pub fn block_tail(mut self, info: BlockTailInfo) -> Self {
1209 assert!(self.is_block_tail.is_none());
1210 self.is_block_tail = Some(info);
1215 #[derive(Clone, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
1216 pub enum VarDebugInfoContents<'tcx> {
1217 /// NOTE(eddyb) There's an unenforced invariant that this `Place` is
1218 /// based on a `Local`, not a `Static`, and contains no indexing.
1220 Const(Constant<'tcx>),
1223 impl<'tcx> Debug for VarDebugInfoContents<'tcx> {
1224 fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
1226 VarDebugInfoContents::Const(c) => write!(fmt, "{}", c),
1227 VarDebugInfoContents::Place(p) => write!(fmt, "{:?}", p),
1232 /// Debug information pertaining to a user variable.
1233 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
1234 pub struct VarDebugInfo<'tcx> {
1237 /// Source info of the user variable, including the scope
1238 /// within which the variable is visible (to debuginfo)
1239 /// (see `LocalDecl`'s `source_info` field for more details).
1240 pub source_info: SourceInfo,
1242 /// Where the data for this user variable is to be found.
1243 pub value: VarDebugInfoContents<'tcx>,
1246 ///////////////////////////////////////////////////////////////////////////
1249 rustc_index::newtype_index! {
1250 /// A node in the MIR [control-flow graph][CFG].
1252 /// There are no branches (e.g., `if`s, function calls, etc.) within a basic block, which makes
1253 /// it easier to do [data-flow analyses] and optimizations. Instead, branches are represented
1254 /// as an edge in a graph between basic blocks.
1256 /// Basic blocks consist of a series of [statements][Statement], ending with a
1257 /// [terminator][Terminator]. Basic blocks can have multiple predecessors and successors,
1258 /// however there is a MIR pass ([`CriticalCallEdges`]) that removes *critical edges*, which
1259 /// are edges that go from a multi-successor node to a multi-predecessor node. This pass is
1260 /// needed because some analyses require that there are no critical edges in the CFG.
1262 /// Note that this type is just an index into [`Body.basic_blocks`](Body::basic_blocks);
1263 /// the actual data that a basic block holds is in [`BasicBlockData`].
1265 /// Read more about basic blocks in the [rustc-dev-guide][guide-mir].
1267 /// [CFG]: https://rustc-dev-guide.rust-lang.org/appendix/background.html#cfg
1268 /// [data-flow analyses]:
1269 /// https://rustc-dev-guide.rust-lang.org/appendix/background.html#what-is-a-dataflow-analysis
1270 /// [`CriticalCallEdges`]: ../../rustc_const_eval/transform/add_call_guards/enum.AddCallGuards.html#variant.CriticalCallEdges
1271 /// [guide-mir]: https://rustc-dev-guide.rust-lang.org/mir/
1272 pub struct BasicBlock {
1274 DEBUG_FORMAT = "bb{}",
1275 const START_BLOCK = 0,
1280 pub fn start_location(self) -> Location {
1281 Location { block: self, statement_index: 0 }
1285 ///////////////////////////////////////////////////////////////////////////
1286 // BasicBlockData and Terminator
1288 /// See [`BasicBlock`] for documentation on what basic blocks are at a high level.
1289 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
1290 pub struct BasicBlockData<'tcx> {
1291 /// List of statements in this block.
1292 pub statements: Vec<Statement<'tcx>>,
1294 /// Terminator for this block.
1296 /// N.B., this should generally ONLY be `None` during construction.
1297 /// Therefore, you should generally access it via the
1298 /// `terminator()` or `terminator_mut()` methods. The only
1299 /// exception is that certain passes, such as `simplify_cfg`, swap
1300 /// out the terminator temporarily with `None` while they continue
1301 /// to recurse over the set of basic blocks.
1302 pub terminator: Option<Terminator<'tcx>>,
1304 /// If true, this block lies on an unwind path. This is used
1305 /// during codegen where distinct kinds of basic blocks may be
1306 /// generated (particularly for MSVC cleanup). Unwind blocks must
1307 /// only branch to other unwind blocks.
1308 pub is_cleanup: bool,
1311 /// Information about an assertion failure.
1312 #[derive(Clone, TyEncodable, TyDecodable, Hash, HashStable, PartialEq, PartialOrd)]
1313 pub enum AssertKind<O> {
1314 BoundsCheck { len: O, index: O },
1315 Overflow(BinOp, O, O),
1319 ResumedAfterReturn(GeneratorKind),
1320 ResumedAfterPanic(GeneratorKind),
1323 #[derive(Clone, Debug, PartialEq, TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable)]
1324 pub enum InlineAsmOperand<'tcx> {
1326 reg: InlineAsmRegOrRegClass,
1327 value: Operand<'tcx>,
1330 reg: InlineAsmRegOrRegClass,
1332 place: Option<Place<'tcx>>,
1335 reg: InlineAsmRegOrRegClass,
1337 in_value: Operand<'tcx>,
1338 out_place: Option<Place<'tcx>>,
1341 value: Box<Constant<'tcx>>,
1344 value: Box<Constant<'tcx>>,
1351 /// Type for MIR `Assert` terminator error messages.
1352 pub type AssertMessage<'tcx> = AssertKind<Operand<'tcx>>;
1354 // FIXME: Change `Successors` to `impl Iterator<Item = BasicBlock>`.
1355 #[allow(rustc::pass_by_value)]
1356 pub type Successors<'a> =
1357 iter::Chain<option::IntoIter<&'a BasicBlock>, slice::Iter<'a, BasicBlock>>;
1358 pub type SuccessorsMut<'a> =
1359 iter::Chain<option::IntoIter<&'a mut BasicBlock>, slice::IterMut<'a, BasicBlock>>;
1361 impl<'tcx> BasicBlockData<'tcx> {
1362 pub fn new(terminator: Option<Terminator<'tcx>>) -> BasicBlockData<'tcx> {
1363 BasicBlockData { statements: vec![], terminator, is_cleanup: false }
1366 /// Accessor for terminator.
1368 /// Terminator may not be None after construction of the basic block is complete. This accessor
1369 /// provides a convenience way to reach the terminator.
1371 pub fn terminator(&self) -> &Terminator<'tcx> {
1372 self.terminator.as_ref().expect("invalid terminator state")
1376 pub fn terminator_mut(&mut self) -> &mut Terminator<'tcx> {
1377 self.terminator.as_mut().expect("invalid terminator state")
1380 pub fn retain_statements<F>(&mut self, mut f: F)
1382 F: FnMut(&mut Statement<'_>) -> bool,
1384 for s in &mut self.statements {
1391 pub fn expand_statements<F, I>(&mut self, mut f: F)
1393 F: FnMut(&mut Statement<'tcx>) -> Option<I>,
1394 I: iter::TrustedLen<Item = Statement<'tcx>>,
1396 // Gather all the iterators we'll need to splice in, and their positions.
1397 let mut splices: Vec<(usize, I)> = vec![];
1398 let mut extra_stmts = 0;
1399 for (i, s) in self.statements.iter_mut().enumerate() {
1400 if let Some(mut new_stmts) = f(s) {
1401 if let Some(first) = new_stmts.next() {
1402 // We can already store the first new statement.
1405 // Save the other statements for optimized splicing.
1406 let remaining = new_stmts.size_hint().0;
1408 splices.push((i + 1 + extra_stmts, new_stmts));
1409 extra_stmts += remaining;
1417 // Splice in the new statements, from the end of the block.
1418 // FIXME(eddyb) This could be more efficient with a "gap buffer"
1419 // where a range of elements ("gap") is left uninitialized, with
1420 // splicing adding new elements to the end of that gap and moving
1421 // existing elements from before the gap to the end of the gap.
1422 // For now, this is safe code, emulating a gap but initializing it.
1423 let mut gap = self.statements.len()..self.statements.len() + extra_stmts;
1424 self.statements.resize(
1426 Statement { source_info: SourceInfo::outermost(DUMMY_SP), kind: StatementKind::Nop },
1428 for (splice_start, new_stmts) in splices.into_iter().rev() {
1429 let splice_end = splice_start + new_stmts.size_hint().0;
1430 while gap.end > splice_end {
1433 self.statements.swap(gap.start, gap.end);
1435 self.statements.splice(splice_start..splice_end, new_stmts);
1436 gap.end = splice_start;
1440 pub fn visitable(&self, index: usize) -> &dyn MirVisitable<'tcx> {
1441 if index < self.statements.len() { &self.statements[index] } else { &self.terminator }
1445 impl<O> AssertKind<O> {
1446 /// Getting a description does not require `O` to be printable, and does not
1447 /// require allocation.
1448 /// The caller is expected to handle `BoundsCheck` separately.
1449 pub fn description(&self) -> &'static str {
1452 Overflow(BinOp::Add, _, _) => "attempt to add with overflow",
1453 Overflow(BinOp::Sub, _, _) => "attempt to subtract with overflow",
1454 Overflow(BinOp::Mul, _, _) => "attempt to multiply with overflow",
1455 Overflow(BinOp::Div, _, _) => "attempt to divide with overflow",
1456 Overflow(BinOp::Rem, _, _) => "attempt to calculate the remainder with overflow",
1457 OverflowNeg(_) => "attempt to negate with overflow",
1458 Overflow(BinOp::Shr, _, _) => "attempt to shift right with overflow",
1459 Overflow(BinOp::Shl, _, _) => "attempt to shift left with overflow",
1460 Overflow(op, _, _) => bug!("{:?} cannot overflow", op),
1461 DivisionByZero(_) => "attempt to divide by zero",
1462 RemainderByZero(_) => "attempt to calculate the remainder with a divisor of zero",
1463 ResumedAfterReturn(GeneratorKind::Gen) => "generator resumed after completion",
1464 ResumedAfterReturn(GeneratorKind::Async(_)) => "`async fn` resumed after completion",
1465 ResumedAfterPanic(GeneratorKind::Gen) => "generator resumed after panicking",
1466 ResumedAfterPanic(GeneratorKind::Async(_)) => "`async fn` resumed after panicking",
1467 BoundsCheck { .. } => bug!("Unexpected AssertKind"),
1471 /// Format the message arguments for the `assert(cond, msg..)` terminator in MIR printing.
1472 pub fn fmt_assert_args<W: Write>(&self, f: &mut W) -> fmt::Result
1478 BoundsCheck { ref len, ref index } => write!(
1480 "\"index out of bounds: the length is {{}} but the index is {{}}\", {:?}, {:?}",
1484 OverflowNeg(op) => {
1485 write!(f, "\"attempt to negate `{{}}`, which would overflow\", {:?}", op)
1487 DivisionByZero(op) => write!(f, "\"attempt to divide `{{}}` by zero\", {:?}", op),
1488 RemainderByZero(op) => write!(
1490 "\"attempt to calculate the remainder of `{{}}` with a divisor of zero\", {:?}",
1493 Overflow(BinOp::Add, l, r) => write!(
1495 "\"attempt to compute `{{}} + {{}}`, which would overflow\", {:?}, {:?}",
1498 Overflow(BinOp::Sub, l, r) => write!(
1500 "\"attempt to compute `{{}} - {{}}`, which would overflow\", {:?}, {:?}",
1503 Overflow(BinOp::Mul, l, r) => write!(
1505 "\"attempt to compute `{{}} * {{}}`, which would overflow\", {:?}, {:?}",
1508 Overflow(BinOp::Div, l, r) => write!(
1510 "\"attempt to compute `{{}} / {{}}`, which would overflow\", {:?}, {:?}",
1513 Overflow(BinOp::Rem, l, r) => write!(
1515 "\"attempt to compute the remainder of `{{}} % {{}}`, which would overflow\", {:?}, {:?}",
1518 Overflow(BinOp::Shr, _, r) => {
1519 write!(f, "\"attempt to shift right by `{{}}`, which would overflow\", {:?}", r)
1521 Overflow(BinOp::Shl, _, r) => {
1522 write!(f, "\"attempt to shift left by `{{}}`, which would overflow\", {:?}", r)
1524 _ => write!(f, "\"{}\"", self.description()),
1529 impl<O: fmt::Debug> fmt::Debug for AssertKind<O> {
1530 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1533 BoundsCheck { ref len, ref index } => write!(
1535 "index out of bounds: the length is {:?} but the index is {:?}",
1538 OverflowNeg(op) => write!(f, "attempt to negate `{:#?}`, which would overflow", op),
1539 DivisionByZero(op) => write!(f, "attempt to divide `{:#?}` by zero", op),
1540 RemainderByZero(op) => write!(
1542 "attempt to calculate the remainder of `{:#?}` with a divisor of zero",
1545 Overflow(BinOp::Add, l, r) => {
1546 write!(f, "attempt to compute `{:#?} + {:#?}`, which would overflow", l, r)
1548 Overflow(BinOp::Sub, l, r) => {
1549 write!(f, "attempt to compute `{:#?} - {:#?}`, which would overflow", l, r)
1551 Overflow(BinOp::Mul, l, r) => {
1552 write!(f, "attempt to compute `{:#?} * {:#?}`, which would overflow", l, r)
1554 Overflow(BinOp::Div, l, r) => {
1555 write!(f, "attempt to compute `{:#?} / {:#?}`, which would overflow", l, r)
1557 Overflow(BinOp::Rem, l, r) => write!(
1559 "attempt to compute the remainder of `{:#?} % {:#?}`, which would overflow",
1562 Overflow(BinOp::Shr, _, r) => {
1563 write!(f, "attempt to shift right by `{:#?}`, which would overflow", r)
1565 Overflow(BinOp::Shl, _, r) => {
1566 write!(f, "attempt to shift left by `{:#?}`, which would overflow", r)
1568 _ => write!(f, "{}", self.description()),
1573 ///////////////////////////////////////////////////////////////////////////
1576 #[derive(Clone, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
1577 pub struct Statement<'tcx> {
1578 pub source_info: SourceInfo,
1579 pub kind: StatementKind<'tcx>,
1582 // `Statement` is used a lot. Make sure it doesn't unintentionally get bigger.
1583 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
1584 static_assert_size!(Statement<'_>, 32);
1586 impl Statement<'_> {
1587 /// Changes a statement to a nop. This is both faster than deleting instructions and avoids
1588 /// invalidating statement indices in `Location`s.
1589 pub fn make_nop(&mut self) {
1590 self.kind = StatementKind::Nop
1593 /// Changes a statement to a nop and returns the original statement.
1594 #[must_use = "If you don't need the statement, use `make_nop` instead"]
1595 pub fn replace_nop(&mut self) -> Self {
1597 source_info: self.source_info,
1598 kind: mem::replace(&mut self.kind, StatementKind::Nop),
1603 /// The various kinds of statements that can appear in MIR.
1605 /// Not all of these are allowed at every [`MirPhase`]. Check the documentation there to see which
1606 /// ones you do not have to worry about. The MIR validator will generally enforce such restrictions,
1607 /// causing an ICE if they are violated.
1608 #[derive(Clone, Debug, PartialEq, TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable)]
1609 pub enum StatementKind<'tcx> {
1610 /// Assign statements roughly correspond to an assignment in Rust proper (`x = ...`) except
1611 /// without the possibility of dropping the previous value (that must be done separately, if at
1612 /// all). The *exact* way this works is undecided. It probably does something like evaluating
1613 /// the LHS to a place and the RHS to a value, and then storing the value to the place. Various
1614 /// parts of this may do type specific things that are more complicated than simply copying
1617 /// **Needs clarification**: The implication of the above idea would be that assignment implies
1618 /// that the resulting value is initialized. I believe we could commit to this separately from
1619 /// committing to whatever part of the memory model we would need to decide on to make the above
1620 /// paragragh precise. Do we want to?
1622 /// Assignments in which the types of the place and rvalue differ are not well-formed.
1624 /// **Needs clarification**: Do we ever want to worry about non-free (in the body) lifetimes for
1625 /// the typing requirement in post drop-elaboration MIR? I think probably not - I'm not sure we
1626 /// could meaningfully require this anyway. How about free lifetimes? Is ignoring this
1627 /// interesting for optimizations? Do we want to allow such optimizations?
1629 /// **Needs clarification**: We currently require that the LHS place not overlap with any place
1630 /// read as part of computation of the RHS for some rvalues (generally those not producing
1631 /// primitives). This requirement is under discussion in [#68364]. As a part of this discussion,
1632 /// it is also unclear in what order the components are evaluated.
1634 /// [#68364]: https://github.com/rust-lang/rust/issues/68364
1636 /// See [`Rvalue`] documentation for details on each of those.
1637 Assign(Box<(Place<'tcx>, Rvalue<'tcx>)>),
1639 /// This represents all the reading that a pattern match may do (e.g., inspecting constants and
1640 /// discriminant values), and the kind of pattern it comes from. This is in order to adapt
1641 /// potential error messages to these specific patterns.
1643 /// Note that this also is emitted for regular `let` bindings to ensure that locals that are
1644 /// never accessed still get some sanity checks for, e.g., `let x: ! = ..;`
1646 /// When executed at runtime this is a nop.
1648 /// Disallowed after drop elaboration.
1649 FakeRead(Box<(FakeReadCause, Place<'tcx>)>),
1651 /// Write the discriminant for a variant to the enum Place.
1653 /// This is permitted for both generators and ADTs. This does not necessarily write to the
1654 /// entire place; instead, it writes to the minimum set of bytes as required by the layout for
1656 SetDiscriminant { place: Box<Place<'tcx>>, variant_index: VariantIdx },
1658 /// Deinitializes the place.
1660 /// This writes `uninit` bytes to the entire place.
1661 Deinit(Box<Place<'tcx>>),
1663 /// `StorageLive` and `StorageDead` statements mark the live range of a local.
1665 /// Using a local before a `StorageLive` or after a `StorageDead` is not well-formed. These
1666 /// statements are not required. If the entire MIR body contains no `StorageLive`/`StorageDead`
1667 /// statements for a particular local, the local is always considered live.
1669 /// More precisely, the MIR validator currently does a `MaybeStorageLiveLocals` analysis to
1670 /// check validity of each use of a local. I believe this is equivalent to requiring for every
1671 /// use of a local, there exist at least one path from the root to that use that contains a
1672 /// `StorageLive` more recently than a `StorageDead`.
1674 /// **Needs clarification**: Is it permitted to have two `StorageLive`s without an intervening
1675 /// `StorageDead`? Two `StorageDead`s without an intervening `StorageLive`? LLVM says poison,
1676 /// yes. If the answer to any of these is "no," is breaking that rule UB or is it an error to
1677 /// have a path in the CFG that might do this?
1680 /// See `StorageLive` above.
1683 /// Retag references in the given place, ensuring they got fresh tags.
1685 /// This is part of the Stacked Borrows model. These statements are currently only interpreted
1686 /// by miri and only generated when `-Z mir-emit-retag` is passed. See
1687 /// <https://internals.rust-lang.org/t/stacked-borrows-an-aliasing-model-for-rust/8153/> for
1690 /// For code that is not specific to stacked borrows, you should consider retags to read
1691 /// and modify the place in an opaque way.
1692 Retag(RetagKind, Box<Place<'tcx>>),
1694 /// Encodes a user's type ascription. These need to be preserved
1695 /// intact so that NLL can respect them. For example:
1696 /// ```ignore (illustrative)
1699 /// The effect of this annotation is to relate the type `T_y` of the place `y`
1700 /// to the user-given type `T`. The effect depends on the specified variance:
1702 /// - `Covariant` -- requires that `T_y <: T`
1703 /// - `Contravariant` -- requires that `T_y :> T`
1704 /// - `Invariant` -- requires that `T_y == T`
1705 /// - `Bivariant` -- no effect
1707 /// When executed at runtime this is a nop.
1709 /// Disallowed after drop elaboration.
1710 AscribeUserType(Box<(Place<'tcx>, UserTypeProjection)>, ty::Variance),
1712 /// Marks the start of a "coverage region", injected with '-Cinstrument-coverage'. A
1713 /// `Coverage` statement carries metadata about the coverage region, used to inject a coverage
1714 /// map into the binary. If `Coverage::kind` is a `Counter`, the statement also generates
1715 /// executable code, to increment a counter variable at runtime, each time the code region is
1717 Coverage(Box<Coverage>),
1719 /// Denotes a call to the intrinsic function `copy_nonoverlapping`.
1721 /// First, all three operands are evaluated. `src` and `dest` must each be a reference, pointer,
1722 /// or `Box` pointing to the same type `T`. `count` must evaluate to a `usize`. Then, `src` and
1723 /// `dest` are dereferenced, and `count * size_of::<T>()` bytes beginning with the first byte of
1724 /// the `src` place are copied to the continguous range of bytes beginning with the first byte
1727 /// **Needs clarification**: In what order are operands computed and dereferenced? It should
1728 /// probably match the order for assignment, but that is also undecided.
1730 /// **Needs clarification**: Is this typed or not, ie is there a typed load and store involved?
1731 /// I vaguely remember Ralf saying somewhere that he thought it should not be.
1732 CopyNonOverlapping(Box<CopyNonOverlapping<'tcx>>),
1734 /// No-op. Useful for deleting instructions without affecting statement indices.
1738 impl<'tcx> StatementKind<'tcx> {
1739 pub fn as_assign_mut(&mut self) -> Option<&mut (Place<'tcx>, Rvalue<'tcx>)> {
1741 StatementKind::Assign(x) => Some(x),
1746 pub fn as_assign(&self) -> Option<&(Place<'tcx>, Rvalue<'tcx>)> {
1748 StatementKind::Assign(x) => Some(x),
1754 /// Describes what kind of retag is to be performed.
1755 #[derive(Copy, Clone, TyEncodable, TyDecodable, Debug, PartialEq, Eq, Hash, HashStable)]
1756 pub enum RetagKind {
1757 /// The initial retag when entering a function.
1759 /// Retag preparing for a two-phase borrow.
1761 /// Retagging raw pointers.
1763 /// A "normal" retag.
1767 /// The `FakeReadCause` describes the type of pattern why a FakeRead statement exists.
1768 #[derive(Copy, Clone, TyEncodable, TyDecodable, Debug, Hash, HashStable, PartialEq)]
1769 pub enum FakeReadCause {
1770 /// Inject a fake read of the borrowed input at the end of each guards
1773 /// This should ensure that you cannot change the variant for an enum while
1774 /// you are in the midst of matching on it.
1777 /// `let x: !; match x {}` doesn't generate any read of x so we need to
1778 /// generate a read of x to check that it is initialized and safe.
1780 /// If a closure pattern matches a Place starting with an Upvar, then we introduce a
1781 /// FakeRead for that Place outside the closure, in such a case this option would be
1782 /// Some(closure_def_id).
1783 /// Otherwise, the value of the optional DefId will be None.
1784 ForMatchedPlace(Option<DefId>),
1786 /// A fake read of the RefWithinGuard version of a bind-by-value variable
1787 /// in a match guard to ensure that its value hasn't change by the time
1788 /// we create the OutsideGuard version.
1791 /// Officially, the semantics of
1793 /// `let pattern = <expr>;`
1795 /// is that `<expr>` is evaluated into a temporary and then this temporary is
1796 /// into the pattern.
1798 /// However, if we see the simple pattern `let var = <expr>`, we optimize this to
1799 /// evaluate `<expr>` directly into the variable `var`. This is mostly unobservable,
1800 /// but in some cases it can affect the borrow checker, as in #53695.
1801 /// Therefore, we insert a "fake read" here to ensure that we get
1802 /// appropriate errors.
1804 /// If a closure pattern matches a Place starting with an Upvar, then we introduce a
1805 /// FakeRead for that Place outside the closure, in such a case this option would be
1806 /// Some(closure_def_id).
1807 /// Otherwise, the value of the optional DefId will be None.
1808 ForLet(Option<DefId>),
1810 /// If we have an index expression like
1812 /// (*x)[1][{ x = y; 4}]
1814 /// then the first bounds check is invalidated when we evaluate the second
1815 /// index expression. Thus we create a fake borrow of `x` across the second
1816 /// indexer, which will cause a borrow check error.
1820 impl Debug for Statement<'_> {
1821 fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
1822 use self::StatementKind::*;
1824 Assign(box (ref place, ref rv)) => write!(fmt, "{:?} = {:?}", place, rv),
1825 FakeRead(box (ref cause, ref place)) => {
1826 write!(fmt, "FakeRead({:?}, {:?})", cause, place)
1828 Retag(ref kind, ref place) => write!(
1832 RetagKind::FnEntry => "[fn entry] ",
1833 RetagKind::TwoPhase => "[2phase] ",
1834 RetagKind::Raw => "[raw] ",
1835 RetagKind::Default => "",
1839 StorageLive(ref place) => write!(fmt, "StorageLive({:?})", place),
1840 StorageDead(ref place) => write!(fmt, "StorageDead({:?})", place),
1841 SetDiscriminant { ref place, variant_index } => {
1842 write!(fmt, "discriminant({:?}) = {:?}", place, variant_index)
1844 Deinit(ref place) => write!(fmt, "Deinit({:?})", place),
1845 AscribeUserType(box (ref place, ref c_ty), ref variance) => {
1846 write!(fmt, "AscribeUserType({:?}, {:?}, {:?})", place, variance, c_ty)
1848 Coverage(box self::Coverage { ref kind, code_region: Some(ref rgn) }) => {
1849 write!(fmt, "Coverage::{:?} for {:?}", kind, rgn)
1851 Coverage(box ref coverage) => write!(fmt, "Coverage::{:?}", coverage.kind),
1852 CopyNonOverlapping(box crate::mir::CopyNonOverlapping {
1857 write!(fmt, "copy_nonoverlapping(src={:?}, dst={:?}, count={:?})", src, dst, count)
1859 Nop => write!(fmt, "nop"),
1864 #[derive(Clone, Debug, PartialEq, TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable)]
1865 pub struct Coverage {
1866 pub kind: CoverageKind,
1867 pub code_region: Option<CodeRegion>,
1870 #[derive(Clone, Debug, PartialEq, TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable)]
1871 pub struct CopyNonOverlapping<'tcx> {
1872 pub src: Operand<'tcx>,
1873 pub dst: Operand<'tcx>,
1874 /// Number of elements to copy from src to dest, not bytes.
1875 pub count: Operand<'tcx>,
1878 ///////////////////////////////////////////////////////////////////////////
1881 /// Places roughly correspond to a "location in memory." Places in MIR are the same mathematical
1882 /// object as places in Rust. This of course means that what exactly they are is undecided and part
1883 /// of the Rust memory model. However, they will likely contain at least the following pieces of
1884 /// information in some form:
1886 /// 1. The address in memory that the place refers to.
1887 /// 2. The provenance with which the place is being accessed.
1888 /// 3. The type of the place and an optional variant index. See [`PlaceTy`][tcx::PlaceTy].
1889 /// 4. Optionally, some metadata. This exists if and only if the type of the place is not `Sized`.
1891 /// We'll give a description below of how all pieces of the place except for the provenance are
1892 /// calculated. We cannot give a description of the provenance, because that is part of the
1893 /// undecided aliasing model - we only include it here at all to acknowledge its existence.
1895 /// Each local naturally corresponds to the place `Place { local, projection: [] }`. This place has
1896 /// the address of the local's allocation and the type of the local.
1898 /// **Needs clarification:** Unsized locals seem to present a bit of an issue. Their allocation
1899 /// can't actually be created on `StorageLive`, because it's unclear how big to make the allocation.
1900 /// Furthermore, MIR produces assignments to unsized locals, although that is not permitted under
1901 /// `#![feature(unsized_locals)]` in Rust. Besides just putting "unsized locals are special and
1902 /// different" in a bunch of places, I (JakobDegen) don't know how to incorporate this behavior into
1903 /// the current MIR semantics in a clean way - possibly this needs some design work first.
1905 /// For places that are not locals, ie they have a non-empty list of projections, we define the
1906 /// values as a function of the parent place, that is the place with its last [`ProjectionElem`]
1907 /// stripped. The way this is computed of course depends on the kind of that last projection
1910 /// - [`Downcast`](ProjectionElem::Downcast): This projection sets the place's variant index to the
1911 /// given one, and makes no other changes. A `Downcast` projection on a place with its variant
1912 /// index already set is not well-formed.
1913 /// - [`Field`](ProjectionElem::Field): `Field` projections take their parent place and create a
1914 /// place referring to one of the fields of the type. The resulting address is the parent
1915 /// address, plus the offset of the field. The type becomes the type of the field. If the parent
1916 /// was unsized and so had metadata associated with it, then the metadata is retained if the
1917 /// field is unsized and thrown out if it is sized.
1919 /// These projections are only legal for tuples, ADTs, closures, and generators. If the ADT or
1920 /// generator has more than one variant, the parent place's variant index must be set, indicating
1921 /// which variant is being used. If it has just one variant, the variant index may or may not be
1922 /// included - the single possible variant is inferred if it is not included.
1923 /// - [`ConstantIndex`](ProjectionElem::ConstantIndex): Computes an offset in units of `T` into the
1924 /// place as described in the documentation for the `ProjectionElem`. The resulting address is
1925 /// the parent's address plus that offset, and the type is `T`. This is only legal if the parent
1926 /// place has type `[T; N]` or `[T]` (*not* `&[T]`). Since such a `T` is always sized, any
1927 /// resulting metadata is thrown out.
1928 /// - [`Subslice`](ProjectionElem::Subslice): This projection calculates an offset and a new
1929 /// address in a similar manner as `ConstantIndex`. It is also only legal on `[T; N]` and `[T]`.
1930 /// However, this yields a `Place` of type `[T]`, and additionally sets the metadata to be the
1931 /// length of the subslice.
1932 /// - [`Index`](ProjectionElem::Index): Like `ConstantIndex`, only legal on `[T; N]` or `[T]`.
1933 /// However, `Index` additionally takes a local from which the value of the index is computed at
1934 /// runtime. Computing the value of the index involves interpreting the `Local` as a
1935 /// `Place { local, projection: [] }`, and then computing its value as if done via
1936 /// [`Operand::Copy`]. The array/slice is then indexed with the resulting value. The local must
1937 /// have type `usize`.
1938 /// - [`Deref`](ProjectionElem::Deref): Derefs are the last type of projection, and the most
1939 /// complicated. They are only legal on parent places that are references, pointers, or `Box`. A
1940 /// `Deref` projection begins by loading a value from the parent place, as if by
1941 /// [`Operand::Copy`]. It then dereferences the resulting pointer, creating a place of the
1942 /// pointee's type. The resulting address is the address that was stored in the pointer. If the
1943 /// pointee type is unsized, the pointer additionally stored the value of the metadata.
1945 /// Computing a place may cause UB. One possibility is that the pointer used for a `Deref` may not
1946 /// be suitably aligned. Another possibility is that the place is not in bounds, meaning it does not
1947 /// point to an actual allocation.
1949 /// However, if this is actually UB and when the UB kicks in is undecided. This is being discussed
1950 /// in [UCG#319]. The options include that every place must obey those rules, that only some places
1951 /// must obey them, or that places impose no rules of their own.
1953 /// [UCG#319]: https://github.com/rust-lang/unsafe-code-guidelines/issues/319
1955 /// Rust currently requires that every place obey those two rules. This is checked by MIRI and taken
1956 /// advantage of by codegen (via `gep inbounds`). That is possibly subject to change.
1957 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, HashStable)]
1958 pub struct Place<'tcx> {
1961 /// projection out of a place (access a field, deref a pointer, etc)
1962 pub projection: &'tcx List<PlaceElem<'tcx>>,
1965 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
1966 static_assert_size!(Place<'_>, 16);
1968 #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
1969 #[derive(TyEncodable, TyDecodable, HashStable)]
1970 pub enum ProjectionElem<V, T> {
1973 /// Index into a slice/array.
1975 /// Note that this does not also dereference, and so it does not exactly correspond to slice
1976 /// indexing in Rust. In other words, in the below Rust code:
1979 /// let x = &[1, 2, 3, 4];
1984 /// The `x[i]` is turned into a `Deref` followed by an `Index`, not just an `Index`. The same
1985 /// thing is true of the `ConstantIndex` and `Subslice` projections below.
1988 /// These indices are generated by slice patterns. Easiest to explain
1991 /// ```ignore (illustrative)
1992 /// [X, _, .._, _, _] => { offset: 0, min_length: 4, from_end: false },
1993 /// [_, X, .._, _, _] => { offset: 1, min_length: 4, from_end: false },
1994 /// [_, _, .._, X, _] => { offset: 2, min_length: 4, from_end: true },
1995 /// [_, _, .._, _, X] => { offset: 1, min_length: 4, from_end: true },
1998 /// index or -index (in Python terms), depending on from_end
2000 /// The thing being indexed must be at least this long. For arrays this
2001 /// is always the exact length.
2003 /// Counting backwards from end? This is always false when indexing an
2008 /// These indices are generated by slice patterns.
2010 /// If `from_end` is true `slice[from..slice.len() - to]`.
2011 /// Otherwise `array[from..to]`.
2015 /// Whether `to` counts from the start or end of the array/slice.
2016 /// For `PlaceElem`s this is `true` if and only if the base is a slice.
2017 /// For `ProjectionKind`, this can also be `true` for arrays.
2021 /// "Downcast" to a variant of an ADT. Currently, we only introduce
2022 /// this for ADTs with more than one variant. It may be better to
2023 /// just introduce it always, or always for enums.
2025 /// The included Symbol is the name of the variant, used for printing MIR.
2026 Downcast(Option<Symbol>, VariantIdx),
2029 impl<V, T> ProjectionElem<V, T> {
2030 /// Returns `true` if the target of this projection may refer to a different region of memory
2032 fn is_indirect(&self) -> bool {
2034 Self::Deref => true,
2038 | Self::ConstantIndex { .. }
2039 | Self::Subslice { .. }
2040 | Self::Downcast(_, _) => false,
2044 /// Returns `true` if this is a `Downcast` projection with the given `VariantIdx`.
2045 pub fn is_downcast_to(&self, v: VariantIdx) -> bool {
2046 matches!(*self, Self::Downcast(_, x) if x == v)
2049 /// Returns `true` if this is a `Field` projection with the given index.
2050 pub fn is_field_to(&self, f: Field) -> bool {
2051 matches!(*self, Self::Field(x, _) if x == f)
2055 /// Alias for projections as they appear in places, where the base is a place
2056 /// and the index is a local.
2057 pub type PlaceElem<'tcx> = ProjectionElem<Local, Ty<'tcx>>;
2059 // This type is fairly frequently used, so we shouldn't unintentionally increase
2061 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
2062 static_assert_size!(PlaceElem<'_>, 24);
2064 /// Alias for projections as they appear in `UserTypeProjection`, where we
2065 /// need neither the `V` parameter for `Index` nor the `T` for `Field`.
2066 pub type ProjectionKind = ProjectionElem<(), ()>;
2068 rustc_index::newtype_index! {
2069 /// A [newtype'd][wrapper] index type in the MIR [control-flow graph][CFG]
2071 /// A field (e.g., `f` in `_1.f`) is one variant of [`ProjectionElem`]. Conceptually,
2072 /// rustc can identify that a field projection refers to either two different regions of memory
2073 /// or the same one between the base and the 'projection element'.
2074 /// Read more about projections in the [rustc-dev-guide][mir-datatypes]
2076 /// [wrapper]: https://rustc-dev-guide.rust-lang.org/appendix/glossary.html#newtype
2077 /// [CFG]: https://rustc-dev-guide.rust-lang.org/appendix/background.html#cfg
2078 /// [mir-datatypes]: https://rustc-dev-guide.rust-lang.org/mir/index.html#mir-data-types
2081 DEBUG_FORMAT = "field[{}]"
2085 #[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
2086 pub struct PlaceRef<'tcx> {
2088 pub projection: &'tcx [PlaceElem<'tcx>],
2091 impl<'tcx> Place<'tcx> {
2092 // FIXME change this to a const fn by also making List::empty a const fn.
2093 pub fn return_place() -> Place<'tcx> {
2094 Place { local: RETURN_PLACE, projection: List::empty() }
2097 /// Returns `true` if this `Place` contains a `Deref` projection.
2099 /// If `Place::is_indirect` returns false, the caller knows that the `Place` refers to the
2100 /// same region of memory as its base.
2101 pub fn is_indirect(&self) -> bool {
2102 self.projection.iter().any(|elem| elem.is_indirect())
2105 /// Finds the innermost `Local` from this `Place`, *if* it is either a local itself or
2106 /// a single deref of a local.
2108 pub fn local_or_deref_local(&self) -> Option<Local> {
2109 self.as_ref().local_or_deref_local()
2112 /// If this place represents a local variable like `_X` with no
2113 /// projections, return `Some(_X)`.
2115 pub fn as_local(&self) -> Option<Local> {
2116 self.as_ref().as_local()
2120 pub fn as_ref(&self) -> PlaceRef<'tcx> {
2121 PlaceRef { local: self.local, projection: &self.projection }
2124 /// Iterate over the projections in evaluation order, i.e., the first element is the base with
2125 /// its projection and then subsequently more projections are added.
2126 /// As a concrete example, given the place a.b.c, this would yield:
2130 /// Given a place without projections, the iterator is empty.
2132 pub fn iter_projections(
2134 ) -> impl Iterator<Item = (PlaceRef<'tcx>, PlaceElem<'tcx>)> + DoubleEndedIterator {
2135 self.projection.iter().enumerate().map(move |(i, proj)| {
2136 let base = PlaceRef { local: self.local, projection: &self.projection[..i] };
2141 /// Generates a new place by appending `more_projections` to the existing ones
2142 /// and interning the result.
2143 pub fn project_deeper(self, more_projections: &[PlaceElem<'tcx>], tcx: TyCtxt<'tcx>) -> Self {
2144 if more_projections.is_empty() {
2148 let mut v: Vec<PlaceElem<'tcx>>;
2150 let new_projections = if self.projection.is_empty() {
2153 v = Vec::with_capacity(self.projection.len() + more_projections.len());
2154 v.extend(self.projection);
2155 v.extend(more_projections);
2159 Place { local: self.local, projection: tcx.intern_place_elems(new_projections) }
2163 impl From<Local> for Place<'_> {
2164 fn from(local: Local) -> Self {
2165 Place { local, projection: List::empty() }
2169 impl<'tcx> PlaceRef<'tcx> {
2170 /// Finds the innermost `Local` from this `Place`, *if* it is either a local itself or
2171 /// a single deref of a local.
2172 pub fn local_or_deref_local(&self) -> Option<Local> {
2174 PlaceRef { local, projection: [] }
2175 | PlaceRef { local, projection: [ProjectionElem::Deref] } => Some(local),
2180 /// If this place represents a local variable like `_X` with no
2181 /// projections, return `Some(_X)`.
2183 pub fn as_local(&self) -> Option<Local> {
2185 PlaceRef { local, projection: [] } => Some(local),
2191 pub fn last_projection(&self) -> Option<(PlaceRef<'tcx>, PlaceElem<'tcx>)> {
2192 if let &[ref proj_base @ .., elem] = self.projection {
2193 Some((PlaceRef { local: self.local, projection: proj_base }, elem))
2200 impl Debug for Place<'_> {
2201 fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
2202 for elem in self.projection.iter().rev() {
2204 ProjectionElem::Downcast(_, _) | ProjectionElem::Field(_, _) => {
2205 write!(fmt, "(").unwrap();
2207 ProjectionElem::Deref => {
2208 write!(fmt, "(*").unwrap();
2210 ProjectionElem::Index(_)
2211 | ProjectionElem::ConstantIndex { .. }
2212 | ProjectionElem::Subslice { .. } => {}
2216 write!(fmt, "{:?}", self.local)?;
2218 for elem in self.projection.iter() {
2220 ProjectionElem::Downcast(Some(name), _index) => {
2221 write!(fmt, " as {})", name)?;
2223 ProjectionElem::Downcast(None, index) => {
2224 write!(fmt, " as variant#{:?})", index)?;
2226 ProjectionElem::Deref => {
2229 ProjectionElem::Field(field, ty) => {
2230 write!(fmt, ".{:?}: {:?})", field.index(), ty)?;
2232 ProjectionElem::Index(ref index) => {
2233 write!(fmt, "[{:?}]", index)?;
2235 ProjectionElem::ConstantIndex { offset, min_length, from_end: false } => {
2236 write!(fmt, "[{:?} of {:?}]", offset, min_length)?;
2238 ProjectionElem::ConstantIndex { offset, min_length, from_end: true } => {
2239 write!(fmt, "[-{:?} of {:?}]", offset, min_length)?;
2241 ProjectionElem::Subslice { from, to, from_end: true } if to == 0 => {
2242 write!(fmt, "[{:?}:]", from)?;
2244 ProjectionElem::Subslice { from, to, from_end: true } if from == 0 => {
2245 write!(fmt, "[:-{:?}]", to)?;
2247 ProjectionElem::Subslice { from, to, from_end: true } => {
2248 write!(fmt, "[{:?}:-{:?}]", from, to)?;
2250 ProjectionElem::Subslice { from, to, from_end: false } => {
2251 write!(fmt, "[{:?}..{:?}]", from, to)?;
2260 ///////////////////////////////////////////////////////////////////////////
2263 rustc_index::newtype_index! {
2264 pub struct SourceScope {
2266 DEBUG_FORMAT = "scope[{}]",
2267 const OUTERMOST_SOURCE_SCOPE = 0,
2272 /// Finds the original HirId this MIR item came from.
2273 /// This is necessary after MIR optimizations, as otherwise we get a HirId
2274 /// from the function that was inlined instead of the function call site.
2275 pub fn lint_root<'tcx>(
2277 source_scopes: &IndexVec<SourceScope, SourceScopeData<'tcx>>,
2278 ) -> Option<HirId> {
2279 let mut data = &source_scopes[self];
2280 // FIXME(oli-obk): we should be able to just walk the `inlined_parent_scope`, but it
2281 // does not work as I thought it would. Needs more investigation and documentation.
2282 while data.inlined.is_some() {
2284 data = &source_scopes[data.parent_scope.unwrap()];
2287 match &data.local_data {
2288 ClearCrossCrate::Set(data) => Some(data.lint_root),
2289 ClearCrossCrate::Clear => None,
2294 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
2295 pub struct SourceScopeData<'tcx> {
2297 pub parent_scope: Option<SourceScope>,
2299 /// Whether this scope is the root of a scope tree of another body,
2300 /// inlined into this body by the MIR inliner.
2301 /// `ty::Instance` is the callee, and the `Span` is the call site.
2302 pub inlined: Option<(ty::Instance<'tcx>, Span)>,
2304 /// Nearest (transitive) parent scope (if any) which is inlined.
2305 /// This is an optimization over walking up `parent_scope`
2306 /// until a scope with `inlined: Some(...)` is found.
2307 pub inlined_parent_scope: Option<SourceScope>,
2309 /// Crate-local information for this source scope, that can't (and
2310 /// needn't) be tracked across crates.
2311 pub local_data: ClearCrossCrate<SourceScopeLocalData>,
2314 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
2315 pub struct SourceScopeLocalData {
2316 /// An `HirId` with lint levels equivalent to this scope's lint levels.
2317 pub lint_root: hir::HirId,
2318 /// The unsafe block that contains this node.
2322 ///////////////////////////////////////////////////////////////////////////
2325 /// An operand in MIR represents a "value" in Rust, the definition of which is undecided and part of
2326 /// the memory model. One proposal for a definition of values can be found [on UCG][value-def].
2328 /// [value-def]: https://github.com/rust-lang/unsafe-code-guidelines/blob/master/wip/value-domain.md
2330 /// The most common way to create values is via loading a place. Loading a place is an operation
2331 /// which reads the memory of the place and converts it to a value. This is a fundamentally *typed*
2332 /// operation. The nature of the value produced depends on the type of the conversion. Furthermore,
2333 /// there may be other effects: if the type has a validity constraint loading the place might be UB
2334 /// if the validity constraint is not met.
2336 /// **Needs clarification:** Ralf proposes that loading a place not have side-effects.
2337 /// This is what is implemented in miri today. Are these the semantics we want for MIR? Is this
2338 /// something we can even decide without knowing more about Rust's memory model?
2340 /// **Needs clarifiation:** Is loading a place that has its variant index set well-formed? Miri
2341 /// currently implements it, but it seems like this may be something to check against in the
2343 #[derive(Clone, PartialEq, TyEncodable, TyDecodable, Hash, HashStable)]
2344 pub enum Operand<'tcx> {
2345 /// Creates a value by loading the given place.
2347 /// Before drop elaboration, the type of the place must be `Copy`. After drop elaboration there
2348 /// is no such requirement.
2351 /// Creates a value by performing loading the place, just like the `Copy` operand.
2353 /// This *may* additionally overwrite the place with `uninit` bytes, depending on how we decide
2354 /// in [UCG#188]. You should not emit MIR that may attempt a subsequent second load of this
2355 /// place without first re-initializing it.
2357 /// [UCG#188]: https://github.com/rust-lang/unsafe-code-guidelines/issues/188
2360 /// Constants are already semantically values, and remain unchanged.
2361 Constant(Box<Constant<'tcx>>),
2364 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
2365 static_assert_size!(Operand<'_>, 24);
2367 impl<'tcx> Debug for Operand<'tcx> {
2368 fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
2369 use self::Operand::*;
2371 Constant(ref a) => write!(fmt, "{:?}", a),
2372 Copy(ref place) => write!(fmt, "{:?}", place),
2373 Move(ref place) => write!(fmt, "move {:?}", place),
2378 impl<'tcx> Operand<'tcx> {
2379 /// Convenience helper to make a constant that refers to the fn
2380 /// with given `DefId` and substs. Since this is used to synthesize
2381 /// MIR, assumes `user_ty` is None.
2382 pub fn function_handle(
2385 substs: SubstsRef<'tcx>,
2388 let ty = tcx.type_of(def_id).subst(tcx, substs);
2389 Operand::Constant(Box::new(Constant {
2392 literal: ConstantKind::Ty(ty::Const::zero_sized(tcx, ty)),
2396 pub fn is_move(&self) -> bool {
2397 matches!(self, Operand::Move(..))
2400 /// Convenience helper to make a literal-like constant from a given scalar value.
2401 /// Since this is used to synthesize MIR, assumes `user_ty` is None.
2402 pub fn const_from_scalar(
2407 ) -> Operand<'tcx> {
2409 let param_env_and_ty = ty::ParamEnv::empty().and(ty);
2411 .layout_of(param_env_and_ty)
2412 .unwrap_or_else(|e| panic!("could not compute layout for {:?}: {:?}", ty, e))
2414 let scalar_size = match val {
2415 Scalar::Int(int) => int.size(),
2416 _ => panic!("Invalid scalar type {:?}", val),
2418 scalar_size == type_size
2420 Operand::Constant(Box::new(Constant {
2423 literal: ConstantKind::Val(ConstValue::Scalar(val), ty),
2427 pub fn to_copy(&self) -> Self {
2429 Operand::Copy(_) | Operand::Constant(_) => self.clone(),
2430 Operand::Move(place) => Operand::Copy(place),
2434 /// Returns the `Place` that is the target of this `Operand`, or `None` if this `Operand` is a
2436 pub fn place(&self) -> Option<Place<'tcx>> {
2438 Operand::Copy(place) | Operand::Move(place) => Some(*place),
2439 Operand::Constant(_) => None,
2443 /// Returns the `Constant` that is the target of this `Operand`, or `None` if this `Operand` is a
2445 pub fn constant(&self) -> Option<&Constant<'tcx>> {
2447 Operand::Constant(x) => Some(&**x),
2448 Operand::Copy(_) | Operand::Move(_) => None,
2452 /// Gets the `ty::FnDef` from an operand if it's a constant function item.
2454 /// While this is unlikely in general, it's the normal case of what you'll
2455 /// find as the `func` in a [`TerminatorKind::Call`].
2456 pub fn const_fn_def(&self) -> Option<(DefId, SubstsRef<'tcx>)> {
2457 let const_ty = self.constant()?.literal.ty();
2458 if let ty::FnDef(def_id, substs) = *const_ty.kind() { Some((def_id, substs)) } else { None }
2462 ///////////////////////////////////////////////////////////////////////////
2465 #[derive(Clone, TyEncodable, TyDecodable, Hash, HashStable, PartialEq)]
2466 /// The various kinds of rvalues that can appear in MIR.
2468 /// Not all of these are allowed at every [`MirPhase`] - when this is the case, it's stated below.
2470 /// Computing any rvalue begins by evaluating the places and operands in some order (**Needs
2471 /// clarification**: Which order?). These are then used to produce a "value" - the same kind of
2472 /// value that an [`Operand`] produces.
2473 pub enum Rvalue<'tcx> {
2474 /// Yields the operand unchanged
2477 /// Creates an array where each element is the value of the operand.
2479 /// This is the cause of a bug in the case where the repetition count is zero because the value
2480 /// is not dropped, see [#74836].
2482 /// Corresponds to source code like `[x; 32]`.
2484 /// [#74836]: https://github.com/rust-lang/rust/issues/74836
2485 Repeat(Operand<'tcx>, ty::Const<'tcx>),
2487 /// Creates a reference of the indicated kind to the place.
2489 /// There is not much to document here, because besides the obvious parts the semantics of this
2490 /// are essentially entirely a part of the aliasing model. There are many UCG issues discussing
2491 /// exactly what the behavior of this operation should be.
2493 /// `Shallow` borrows are disallowed after drop lowering.
2494 Ref(Region<'tcx>, BorrowKind, Place<'tcx>),
2496 /// Creates a pointer/reference to the given thread local.
2498 /// The yielded type is a `*mut T` if the static is mutable, otherwise if the static is extern a
2499 /// `*const T`, and if neither of those apply a `&T`.
2501 /// **Note:** This is a runtime operation that actually executes code and is in this sense more
2502 /// like a function call. Also, eliminating dead stores of this rvalue causes `fn main() {}` to
2503 /// SIGILL for some reason that I (JakobDegen) never got a chance to look into.
2505 /// **Needs clarification**: Are there weird additional semantics here related to the runtime
2506 /// nature of this operation?
2507 ThreadLocalRef(DefId),
2509 /// Creates a pointer with the indicated mutability to the place.
2511 /// This is generated by pointer casts like `&v as *const _` or raw address of expressions like
2512 /// `&raw v` or `addr_of!(v)`.
2514 /// Like with references, the semantics of this operation are heavily dependent on the aliasing
2516 AddressOf(Mutability, Place<'tcx>),
2518 /// Yields the length of the place, as a `usize`.
2520 /// If the type of the place is an array, this is the array length. For slices (`[T]`, not
2521 /// `&[T]`) this accesses the place's metadata to determine the length. This rvalue is
2522 /// ill-formed for places of other types.
2525 /// Performs essentially all of the casts that can be performed via `as`.
2527 /// This allows for casts from/to a variety of types.
2529 /// **FIXME**: Document exactly which `CastKind`s allow which types of casts. Figure out why
2530 /// `ArrayToPointer` and `MutToConstPointer` are special.
2531 Cast(CastKind, Operand<'tcx>, Ty<'tcx>),
2533 /// * `Offset` has the same semantics as [`offset`](pointer::offset), except that the second
2534 /// parameter may be a `usize` as well.
2535 /// * The comparison operations accept `bool`s, `char`s, signed or unsigned integers, floats,
2536 /// raw pointers, or function pointers and return a `bool`. The types of the operands must be
2537 /// matching, up to the usual caveat of the lifetimes in function pointers.
2538 /// * Left and right shift operations accept signed or unsigned integers not necessarily of the
2539 /// same type and return a value of the same type as their LHS. Like in Rust, the RHS is
2540 /// truncated as needed.
2541 /// * The `Bit*` operations accept signed integers, unsigned integers, or bools with matching
2542 /// types and return a value of that type.
2543 /// * The remaining operations accept signed integers, unsigned integers, or floats with
2544 /// matching types and return a value of that type.
2545 BinaryOp(BinOp, Box<(Operand<'tcx>, Operand<'tcx>)>),
2547 /// Same as `BinaryOp`, but yields `(T, bool)` instead of `T`. In addition to performing the
2548 /// same computation as the matching `BinaryOp`, checks if the infinite precison result would be
2549 /// unequal to the actual result and sets the `bool` if this is the case.
2551 /// This only supports addition, subtraction, multiplication, and shift operations on integers.
2552 CheckedBinaryOp(BinOp, Box<(Operand<'tcx>, Operand<'tcx>)>),
2554 /// Computes a value as described by the operation.
2555 NullaryOp(NullOp, Ty<'tcx>),
2557 /// Exactly like `BinaryOp`, but less operands.
2559 /// Also does two's-complement arithmetic. Negation requires a signed integer or a float;
2560 /// bitwise not requires a signed integer, unsigned integer, or bool. Both operation kinds
2561 /// return a value with the same type as their operand.
2562 UnaryOp(UnOp, Operand<'tcx>),
2564 /// Computes the discriminant of the place, returning it as an integer of type
2565 /// [`discriminant_ty`].
2567 /// The validity requirements for the underlying value are undecided for this rvalue, see
2568 /// [#91095]. Note too that the value of the discriminant is not the same thing as the
2569 /// variant index; use [`discriminant_for_variant`] to convert.
2571 /// For types defined in the source code as enums, this is well behaved. This is also well
2572 /// formed for other types, but yields no particular value - there is no reason it couldn't be
2573 /// defined to yield eg zero though.
2575 /// [`discriminant_ty`]: crate::ty::Ty::discriminant_ty
2576 /// [#91095]: https://github.com/rust-lang/rust/issues/91095
2577 /// [`discriminant_for_variant`]: crate::ty::Ty::discriminant_for_variant
2578 Discriminant(Place<'tcx>),
2580 /// Creates an aggregate value, like a tuple or struct.
2582 /// This is needed because dataflow analysis needs to distinguish
2583 /// `dest = Foo { x: ..., y: ... }` from `dest.x = ...; dest.y = ...;` in the case that `Foo`
2584 /// has a destructor.
2586 /// Disallowed after deaggregation for all aggregate kinds except `Array` and `Generator`. After
2587 /// generator lowering, `Generator` aggregate kinds are disallowed too.
2588 Aggregate(Box<AggregateKind<'tcx>>, Vec<Operand<'tcx>>),
2590 /// Transmutes a `*mut u8` into shallow-initialized `Box<T>`.
2592 /// This is different from a normal transmute because dataflow analysis will treat the box as
2593 /// initialized but its content as uninitialized. Like other pointer casts, this in general
2594 /// affects alias analysis.
2595 ShallowInitBox(Operand<'tcx>, Ty<'tcx>),
2598 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
2599 static_assert_size!(Rvalue<'_>, 40);
2601 #[derive(Clone, Copy, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
2604 Pointer(PointerCast),
2607 #[derive(Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
2608 pub enum AggregateKind<'tcx> {
2609 /// The type is of the element
2613 /// The second field is the variant index. It's equal to 0 for struct
2614 /// and union expressions. The fourth field is
2615 /// active field number and is present only for union expressions
2616 /// -- e.g., for a union expression `SomeUnion { c: .. }`, the
2617 /// active field index would identity the field `c`
2618 Adt(DefId, VariantIdx, SubstsRef<'tcx>, Option<UserTypeAnnotationIndex>, Option<usize>),
2620 Closure(DefId, SubstsRef<'tcx>),
2621 Generator(DefId, SubstsRef<'tcx>, hir::Movability),
2624 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
2625 static_assert_size!(AggregateKind<'_>, 48);
2627 #[derive(Copy, Clone, Debug, PartialEq, PartialOrd, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
2629 /// The `+` operator (addition)
2631 /// The `-` operator (subtraction)
2633 /// The `*` operator (multiplication)
2635 /// The `/` operator (division)
2637 /// Division by zero is UB, because the compiler should have inserted checks
2640 /// The `%` operator (modulus)
2642 /// Using zero as the modulus (second operand) is UB, because the compiler
2643 /// should have inserted checks prior to this.
2645 /// The `^` operator (bitwise xor)
2647 /// The `&` operator (bitwise and)
2649 /// The `|` operator (bitwise or)
2651 /// The `<<` operator (shift left)
2653 /// The offset is truncated to the size of the first operand before shifting.
2655 /// The `>>` operator (shift right)
2657 /// The offset is truncated to the size of the first operand before shifting.
2659 /// The `==` operator (equality)
2661 /// The `<` operator (less than)
2663 /// The `<=` operator (less than or equal to)
2665 /// The `!=` operator (not equal to)
2667 /// The `>=` operator (greater than or equal to)
2669 /// The `>` operator (greater than)
2671 /// The `ptr.offset` operator
2676 pub fn is_checkable(self) -> bool {
2678 matches!(self, Add | Sub | Mul | Shl | Shr)
2682 #[derive(Copy, Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
2684 /// Returns the size of a value of that type
2686 /// Returns the minimum alignment of a type
2690 #[derive(Copy, Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
2692 /// The `!` operator for logical inversion
2694 /// The `-` operator for negation
2698 impl<'tcx> Debug for Rvalue<'tcx> {
2699 fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
2700 use self::Rvalue::*;
2703 Use(ref place) => write!(fmt, "{:?}", place),
2704 Repeat(ref a, b) => {
2705 write!(fmt, "[{:?}; ", a)?;
2706 pretty_print_const(b, fmt, false)?;
2709 Len(ref a) => write!(fmt, "Len({:?})", a),
2710 Cast(ref kind, ref place, ref ty) => {
2711 write!(fmt, "{:?} as {:?} ({:?})", place, ty, kind)
2713 BinaryOp(ref op, box (ref a, ref b)) => write!(fmt, "{:?}({:?}, {:?})", op, a, b),
2714 CheckedBinaryOp(ref op, box (ref a, ref b)) => {
2715 write!(fmt, "Checked{:?}({:?}, {:?})", op, a, b)
2717 UnaryOp(ref op, ref a) => write!(fmt, "{:?}({:?})", op, a),
2718 Discriminant(ref place) => write!(fmt, "discriminant({:?})", place),
2719 NullaryOp(ref op, ref t) => write!(fmt, "{:?}({:?})", op, t),
2720 ThreadLocalRef(did) => ty::tls::with(|tcx| {
2721 let muta = tcx.static_mutability(did).unwrap().prefix_str();
2722 write!(fmt, "&/*tls*/ {}{}", muta, tcx.def_path_str(did))
2724 Ref(region, borrow_kind, ref place) => {
2725 let kind_str = match borrow_kind {
2726 BorrowKind::Shared => "",
2727 BorrowKind::Shallow => "shallow ",
2728 BorrowKind::Mut { .. } | BorrowKind::Unique => "mut ",
2731 // When printing regions, add trailing space if necessary.
2732 let print_region = ty::tls::with(|tcx| {
2733 tcx.sess.verbose() || tcx.sess.opts.debugging_opts.identify_regions
2735 let region = if print_region {
2736 let mut region = region.to_string();
2737 if !region.is_empty() {
2742 // Do not even print 'static
2745 write!(fmt, "&{}{}{:?}", region, kind_str, place)
2748 AddressOf(mutability, ref place) => {
2749 let kind_str = match mutability {
2750 Mutability::Mut => "mut",
2751 Mutability::Not => "const",
2754 write!(fmt, "&raw {} {:?}", kind_str, place)
2757 Aggregate(ref kind, ref places) => {
2758 let fmt_tuple = |fmt: &mut Formatter<'_>, name: &str| {
2759 let mut tuple_fmt = fmt.debug_tuple(name);
2760 for place in places {
2761 tuple_fmt.field(place);
2767 AggregateKind::Array(_) => write!(fmt, "{:?}", places),
2769 AggregateKind::Tuple => {
2770 if places.is_empty() {
2777 AggregateKind::Adt(adt_did, variant, substs, _user_ty, _) => {
2778 ty::tls::with(|tcx| {
2779 let variant_def = &tcx.adt_def(adt_did).variant(variant);
2780 let substs = tcx.lift(substs).expect("could not lift for printing");
2781 let name = FmtPrinter::new(tcx, Namespace::ValueNS)
2782 .print_def_path(variant_def.def_id, substs)?
2785 match variant_def.ctor_kind {
2786 CtorKind::Const => fmt.write_str(&name),
2787 CtorKind::Fn => fmt_tuple(fmt, &name),
2788 CtorKind::Fictive => {
2789 let mut struct_fmt = fmt.debug_struct(&name);
2790 for (field, place) in iter::zip(&variant_def.fields, places) {
2791 struct_fmt.field(field.name.as_str(), place);
2799 AggregateKind::Closure(def_id, substs) => ty::tls::with(|tcx| {
2800 if let Some(def_id) = def_id.as_local() {
2801 let name = if tcx.sess.opts.debugging_opts.span_free_formats {
2802 let substs = tcx.lift(substs).unwrap();
2805 tcx.def_path_str_with_substs(def_id.to_def_id(), substs),
2808 let span = tcx.def_span(def_id);
2811 tcx.sess.source_map().span_to_diagnostic_string(span)
2814 let mut struct_fmt = fmt.debug_struct(&name);
2816 // FIXME(project-rfc-2229#48): This should be a list of capture names/places
2817 if let Some(upvars) = tcx.upvars_mentioned(def_id) {
2818 for (&var_id, place) in iter::zip(upvars.keys(), places) {
2819 let var_name = tcx.hir().name(var_id);
2820 struct_fmt.field(var_name.as_str(), place);
2826 write!(fmt, "[closure]")
2830 AggregateKind::Generator(def_id, _, _) => ty::tls::with(|tcx| {
2831 if let Some(def_id) = def_id.as_local() {
2832 let name = format!("[generator@{:?}]", tcx.def_span(def_id));
2833 let mut struct_fmt = fmt.debug_struct(&name);
2835 // FIXME(project-rfc-2229#48): This should be a list of capture names/places
2836 if let Some(upvars) = tcx.upvars_mentioned(def_id) {
2837 for (&var_id, place) in iter::zip(upvars.keys(), places) {
2838 let var_name = tcx.hir().name(var_id);
2839 struct_fmt.field(var_name.as_str(), place);
2845 write!(fmt, "[generator]")
2851 ShallowInitBox(ref place, ref ty) => {
2852 write!(fmt, "ShallowInitBox({:?}, {:?})", place, ty)
2858 ///////////////////////////////////////////////////////////////////////////
2861 /// Two constants are equal if they are the same constant. Note that
2862 /// this does not necessarily mean that they are `==` in Rust. In
2863 /// particular, one must be wary of `NaN`!
2865 #[derive(Clone, Copy, PartialEq, TyEncodable, TyDecodable, Hash, HashStable)]
2866 pub struct Constant<'tcx> {
2869 /// Optional user-given type: for something like
2870 /// `collect::<Vec<_>>`, this would be present and would
2871 /// indicate that `Vec<_>` was explicitly specified.
2873 /// Needed for NLL to impose user-given type constraints.
2874 pub user_ty: Option<UserTypeAnnotationIndex>,
2876 pub literal: ConstantKind<'tcx>,
2879 #[derive(Clone, Copy, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable, Debug)]
2881 pub enum ConstantKind<'tcx> {
2882 /// This constant came from the type system
2883 Ty(ty::Const<'tcx>),
2884 /// This constant cannot go back into the type system, as it represents
2885 /// something the type system cannot handle (e.g. pointers).
2886 Val(interpret::ConstValue<'tcx>, Ty<'tcx>),
2889 impl<'tcx> Constant<'tcx> {
2890 pub fn check_static_ptr(&self, tcx: TyCtxt<'_>) -> Option<DefId> {
2891 match self.literal.try_to_scalar() {
2892 Some(Scalar::Ptr(ptr, _size)) => match tcx.global_alloc(ptr.provenance) {
2893 GlobalAlloc::Static(def_id) => {
2894 assert!(!tcx.is_thread_local_static(def_id));
2903 pub fn ty(&self) -> Ty<'tcx> {
2908 impl<'tcx> From<ty::Const<'tcx>> for ConstantKind<'tcx> {
2910 fn from(ct: ty::Const<'tcx>) -> Self {
2912 ty::ConstKind::Value(cv) => {
2913 // FIXME Once valtrees are introduced we need to convert those
2914 // into `ConstValue` instances here
2915 Self::Val(cv, ct.ty())
2922 impl<'tcx> ConstantKind<'tcx> {
2923 /// Returns `None` if the constant is not trivially safe for use in the type system.
2924 pub fn const_for_ty(&self) -> Option<ty::Const<'tcx>> {
2926 ConstantKind::Ty(c) => Some(*c),
2927 ConstantKind::Val(..) => None,
2931 pub fn ty(&self) -> Ty<'tcx> {
2933 ConstantKind::Ty(c) => c.ty(),
2934 ConstantKind::Val(_, ty) => *ty,
2938 pub fn try_val(&self) -> Option<ConstValue<'tcx>> {
2940 ConstantKind::Ty(c) => match c.val() {
2941 ty::ConstKind::Value(v) => Some(v),
2944 ConstantKind::Val(v, _) => Some(*v),
2949 pub fn try_to_value(self) -> Option<interpret::ConstValue<'tcx>> {
2951 ConstantKind::Ty(c) => c.val().try_to_value(),
2952 ConstantKind::Val(val, _) => Some(val),
2957 pub fn try_to_scalar(self) -> Option<Scalar> {
2958 self.try_to_value()?.try_to_scalar()
2962 pub fn try_to_scalar_int(self) -> Option<ScalarInt> {
2963 Some(self.try_to_value()?.try_to_scalar()?.assert_int())
2967 pub fn try_to_bits(self, size: Size) -> Option<u128> {
2968 self.try_to_scalar_int()?.to_bits(size).ok()
2972 pub fn try_to_bool(self) -> Option<bool> {
2973 self.try_to_scalar_int()?.try_into().ok()
2977 pub fn eval(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Self {
2980 // FIXME Need to use a different evaluation function that directly returns a `ConstValue`
2981 // if evaluation succeeds and does not create a ValTree first
2982 if let Some(val) = c.val().try_eval(tcx, param_env) {
2984 Ok(val) => Self::Val(val, c.ty()),
2985 Err(_) => Self::Ty(tcx.const_error(self.ty())),
2991 Self::Val(_, _) => self,
2995 /// Panics if the value cannot be evaluated or doesn't contain a valid integer of the given type.
2997 pub fn eval_bits(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>, ty: Ty<'tcx>) -> u128 {
2998 self.try_eval_bits(tcx, param_env, ty)
2999 .unwrap_or_else(|| bug!("expected bits of {:#?}, got {:#?}", ty, self))
3003 pub fn try_eval_bits(
3006 param_env: ty::ParamEnv<'tcx>,
3010 Self::Ty(ct) => ct.try_eval_bits(tcx, param_env, ty),
3011 Self::Val(val, t) => {
3014 tcx.layout_of(param_env.with_reveal_all_normalized(tcx).and(ty)).ok()?.size;
3015 val.try_to_bits(size)
3021 pub fn try_eval_bool(&self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Option<bool> {
3023 Self::Ty(ct) => ct.try_eval_bool(tcx, param_env),
3024 Self::Val(val, _) => val.try_to_bool(),
3029 pub fn try_eval_usize(&self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Option<u64> {
3031 Self::Ty(ct) => ct.try_eval_usize(tcx, param_env),
3032 Self::Val(val, _) => val.try_to_machine_usize(tcx),
3039 param_env_ty: ty::ParamEnvAnd<'tcx, Ty<'tcx>>,
3042 .layout_of(param_env_ty)
3043 .unwrap_or_else(|e| {
3044 bug!("could not compute layout for {:?}: {:?}", param_env_ty.value, e)
3047 let cv = ConstValue::Scalar(Scalar::from_uint(bits, size));
3049 Self::Val(cv, param_env_ty.value)
3052 pub fn from_bool(tcx: TyCtxt<'tcx>, v: bool) -> Self {
3053 let cv = ConstValue::from_bool(v);
3054 Self::Val(cv, tcx.types.bool)
3057 pub fn zero_sized(ty: Ty<'tcx>) -> Self {
3058 let cv = ConstValue::Scalar(Scalar::ZST);
3062 pub fn from_usize(tcx: TyCtxt<'tcx>, n: u64) -> Self {
3063 let ty = tcx.types.usize;
3064 Self::from_bits(tcx, n as u128, ty::ParamEnv::empty().and(ty))
3067 /// Literals are converted to `ConstantKindVal`, const generic parameters are eagerly
3068 /// converted to a constant, everything else becomes `Unevaluated`.
3069 pub fn from_anon_const(
3072 param_env: ty::ParamEnv<'tcx>,
3074 Self::from_opt_const_arg_anon_const(tcx, ty::WithOptConstParam::unknown(def_id), param_env)
3077 #[instrument(skip(tcx), level = "debug")]
3078 fn from_opt_const_arg_anon_const(
3080 def: ty::WithOptConstParam<LocalDefId>,
3081 param_env: ty::ParamEnv<'tcx>,
3083 let body_id = match tcx.hir().get_by_def_id(def.did) {
3084 hir::Node::AnonConst(ac) => ac.body,
3086 tcx.def_span(def.did.to_def_id()),
3087 "from_anon_const can only process anonymous constants"
3091 let expr = &tcx.hir().body(body_id).value;
3094 // Unwrap a block, so that e.g. `{ P }` is recognised as a parameter. Const arguments
3095 // currently have to be wrapped in curly brackets, so it's necessary to special-case.
3096 let expr = match &expr.kind {
3097 hir::ExprKind::Block(block, _) if block.stmts.is_empty() && block.expr.is_some() => {
3098 block.expr.as_ref().unwrap()
3103 let ty = tcx.type_of(def.def_id_for_type_of());
3105 // FIXME(const_generics): We currently have to special case parameters because `min_const_generics`
3106 // does not provide the parents generics to anonymous constants. We still allow generic const
3107 // parameters by themselves however, e.g. `N`. These constants would cause an ICE if we were to
3108 // ever try to substitute the generic parameters in their bodies.
3110 // While this doesn't happen as these constants are always used as `ty::ConstKind::Param`, it does
3111 // cause issues if we were to remove that special-case and try to evaluate the constant instead.
3112 use hir::{def::DefKind::ConstParam, def::Res, ExprKind, Path, QPath};
3114 ExprKind::Path(QPath::Resolved(_, &Path { res: Res::Def(ConstParam, def_id), .. })) => {
3115 // Find the name and index of the const parameter by indexing the generics of
3116 // the parent item and construct a `ParamConst`.
3117 let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
3118 let item_id = tcx.hir().get_parent_node(hir_id);
3119 let item_def_id = tcx.hir().local_def_id(item_id);
3120 let generics = tcx.generics_of(item_def_id.to_def_id());
3121 let index = generics.param_def_id_to_index[&def_id];
3122 let name = tcx.hir().name(hir_id);
3123 let ty_const = tcx.mk_const(ty::ConstS {
3124 val: ty::ConstKind::Param(ty::ParamConst::new(index, name)),
3128 return Self::Ty(ty_const);
3133 let hir_id = tcx.hir().local_def_id_to_hir_id(def.did);
3134 let parent_substs = if let Some(parent_hir_id) = tcx.hir().find_parent_node(hir_id) {
3135 if let Some(parent_did) = tcx.hir().opt_local_def_id(parent_hir_id) {
3136 InternalSubsts::identity_for_item(tcx, parent_did.to_def_id())
3138 tcx.mk_substs(Vec::<GenericArg<'tcx>>::new().into_iter())
3141 tcx.mk_substs(Vec::<GenericArg<'tcx>>::new().into_iter())
3143 debug!(?parent_substs);
3145 let did = def.did.to_def_id();
3146 let child_substs = InternalSubsts::identity_for_item(tcx, did);
3147 let substs = tcx.mk_substs(parent_substs.into_iter().chain(child_substs.into_iter()));
3150 let hir_id = tcx.hir().local_def_id_to_hir_id(def.did);
3151 let span = tcx.hir().span(hir_id);
3152 let uneval = ty::Unevaluated::new(def.to_global(), substs);
3153 debug!(?span, ?param_env);
3155 match tcx.const_eval_resolve(param_env, uneval, Some(span)) {
3156 Ok(val) => Self::Val(val, ty),
3158 // Error was handled in `const_eval_resolve`. Here we just create a
3159 // new unevaluated const and error hard later in codegen
3160 let ty_const = tcx.mk_const(ty::ConstS {
3161 val: ty::ConstKind::Unevaluated(ty::Unevaluated {
3162 def: def.to_global(),
3163 substs: InternalSubsts::identity_for_item(tcx, def.did.to_def_id()),
3175 /// A collection of projections into user types.
3177 /// They are projections because a binding can occur a part of a
3178 /// parent pattern that has been ascribed a type.
3180 /// Its a collection because there can be multiple type ascriptions on
3181 /// the path from the root of the pattern down to the binding itself.
3185 /// ```ignore (illustrative)
3186 /// struct S<'a>((i32, &'a str), String);
3187 /// let S((_, w): (i32, &'static str), _): S = ...;
3188 /// // ------ ^^^^^^^^^^^^^^^^^^^ (1)
3189 /// // --------------------------------- ^ (2)
3192 /// The highlights labelled `(1)` show the subpattern `(_, w)` being
3193 /// ascribed the type `(i32, &'static str)`.
3195 /// The highlights labelled `(2)` show the whole pattern being
3196 /// ascribed the type `S`.
3198 /// In this example, when we descend to `w`, we will have built up the
3199 /// following two projected types:
3201 /// * base: `S`, projection: `(base.0).1`
3202 /// * base: `(i32, &'static str)`, projection: `base.1`
3204 /// The first will lead to the constraint `w: &'1 str` (for some
3205 /// inferred region `'1`). The second will lead to the constraint `w:
3207 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
3208 pub struct UserTypeProjections {
3209 pub contents: Vec<(UserTypeProjection, Span)>,
3212 impl<'tcx> UserTypeProjections {
3213 pub fn none() -> Self {
3214 UserTypeProjections { contents: vec![] }
3217 pub fn is_empty(&self) -> bool {
3218 self.contents.is_empty()
3221 pub fn projections_and_spans(
3223 ) -> impl Iterator<Item = &(UserTypeProjection, Span)> + ExactSizeIterator {
3224 self.contents.iter()
3227 pub fn projections(&self) -> impl Iterator<Item = &UserTypeProjection> + ExactSizeIterator {
3228 self.contents.iter().map(|&(ref user_type, _span)| user_type)
3231 pub fn push_projection(mut self, user_ty: &UserTypeProjection, span: Span) -> Self {
3232 self.contents.push((user_ty.clone(), span));
3238 mut f: impl FnMut(UserTypeProjection) -> UserTypeProjection,
3240 self.contents = self.contents.into_iter().map(|(proj, span)| (f(proj), span)).collect();
3244 pub fn index(self) -> Self {
3245 self.map_projections(|pat_ty_proj| pat_ty_proj.index())
3248 pub fn subslice(self, from: u64, to: u64) -> Self {
3249 self.map_projections(|pat_ty_proj| pat_ty_proj.subslice(from, to))
3252 pub fn deref(self) -> Self {
3253 self.map_projections(|pat_ty_proj| pat_ty_proj.deref())
3256 pub fn leaf(self, field: Field) -> Self {
3257 self.map_projections(|pat_ty_proj| pat_ty_proj.leaf(field))
3260 pub fn variant(self, adt_def: AdtDef<'tcx>, variant_index: VariantIdx, field: Field) -> Self {
3261 self.map_projections(|pat_ty_proj| pat_ty_proj.variant(adt_def, variant_index, field))
3265 /// Encodes the effect of a user-supplied type annotation on the
3266 /// subcomponents of a pattern. The effect is determined by applying the
3267 /// given list of projections to some underlying base type. Often,
3268 /// the projection element list `projs` is empty, in which case this
3269 /// directly encodes a type in `base`. But in the case of complex patterns with
3270 /// subpatterns and bindings, we want to apply only a *part* of the type to a variable,
3271 /// in which case the `projs` vector is used.
3275 /// * `let x: T = ...` -- here, the `projs` vector is empty.
3277 /// * `let (x, _): T = ...` -- here, the `projs` vector would contain
3278 /// `field[0]` (aka `.0`), indicating that the type of `s` is
3279 /// determined by finding the type of the `.0` field from `T`.
3280 #[derive(Clone, Debug, TyEncodable, TyDecodable, Hash, HashStable, PartialEq)]
3281 pub struct UserTypeProjection {
3282 pub base: UserTypeAnnotationIndex,
3283 pub projs: Vec<ProjectionKind>,
3286 impl Copy for ProjectionKind {}
3288 impl UserTypeProjection {
3289 pub(crate) fn index(mut self) -> Self {
3290 self.projs.push(ProjectionElem::Index(()));
3294 pub(crate) fn subslice(mut self, from: u64, to: u64) -> Self {
3295 self.projs.push(ProjectionElem::Subslice { from, to, from_end: true });
3299 pub(crate) fn deref(mut self) -> Self {
3300 self.projs.push(ProjectionElem::Deref);
3304 pub(crate) fn leaf(mut self, field: Field) -> Self {
3305 self.projs.push(ProjectionElem::Field(field, ()));
3309 pub(crate) fn variant(
3311 adt_def: AdtDef<'_>,
3312 variant_index: VariantIdx,
3315 self.projs.push(ProjectionElem::Downcast(
3316 Some(adt_def.variant(variant_index).name),
3319 self.projs.push(ProjectionElem::Field(field, ()));
3324 TrivialTypeFoldableAndLiftImpls! { ProjectionKind, }
3326 impl<'tcx> TypeFoldable<'tcx> for UserTypeProjection {
3327 fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
3330 ) -> Result<Self, F::Error> {
3331 Ok(UserTypeProjection {
3332 base: self.base.try_fold_with(folder)?,
3333 projs: self.projs.try_fold_with(folder)?,
3337 fn super_visit_with<Vs: TypeVisitor<'tcx>>(
3340 ) -> ControlFlow<Vs::BreakTy> {
3341 self.base.visit_with(visitor)
3342 // Note: there's nothing in `self.proj` to visit.
3346 rustc_index::newtype_index! {
3347 pub struct Promoted {
3349 DEBUG_FORMAT = "promoted[{}]"
3353 impl<'tcx> Debug for Constant<'tcx> {
3354 fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
3355 write!(fmt, "{}", self)
3359 impl<'tcx> Display for Constant<'tcx> {
3360 fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
3361 match self.ty().kind() {
3363 _ => write!(fmt, "const ")?,
3365 Display::fmt(&self.literal, fmt)
3369 impl<'tcx> Display for ConstantKind<'tcx> {
3370 fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
3372 ConstantKind::Ty(c) => pretty_print_const(c, fmt, true),
3373 ConstantKind::Val(val, ty) => pretty_print_const_value(val, ty, fmt, true),
3378 fn pretty_print_const<'tcx>(
3380 fmt: &mut Formatter<'_>,
3383 use crate::ty::print::PrettyPrinter;
3384 ty::tls::with(|tcx| {
3385 let literal = tcx.lift(c).unwrap();
3386 let mut cx = FmtPrinter::new(tcx, Namespace::ValueNS);
3387 cx.print_alloc_ids = true;
3388 let cx = cx.pretty_print_const(literal, print_types)?;
3389 fmt.write_str(&cx.into_buffer())?;
3394 fn pretty_print_const_value<'tcx>(
3395 val: interpret::ConstValue<'tcx>,
3397 fmt: &mut Formatter<'_>,
3400 use crate::ty::print::PrettyPrinter;
3401 ty::tls::with(|tcx| {
3402 let val = tcx.lift(val).unwrap();
3403 let ty = tcx.lift(ty).unwrap();
3404 let mut cx = FmtPrinter::new(tcx, Namespace::ValueNS);
3405 cx.print_alloc_ids = true;
3406 let cx = cx.pretty_print_const_value(val, ty, print_types)?;
3407 fmt.write_str(&cx.into_buffer())?;
3412 impl<'tcx> graph::DirectedGraph for Body<'tcx> {
3413 type Node = BasicBlock;
3416 impl<'tcx> graph::WithNumNodes for Body<'tcx> {
3418 fn num_nodes(&self) -> usize {
3419 self.basic_blocks.len()
3423 impl<'tcx> graph::WithStartNode for Body<'tcx> {
3425 fn start_node(&self) -> Self::Node {
3430 impl<'tcx> graph::WithSuccessors for Body<'tcx> {
3432 fn successors(&self, node: Self::Node) -> <Self as GraphSuccessors<'_>>::Iter {
3433 self.basic_blocks[node].terminator().successors().cloned()
3437 impl<'a, 'b> graph::GraphSuccessors<'b> for Body<'a> {
3438 type Item = BasicBlock;
3439 type Iter = iter::Cloned<Successors<'b>>;
3442 impl<'tcx, 'graph> graph::GraphPredecessors<'graph> for Body<'tcx> {
3443 type Item = BasicBlock;
3444 type Iter = std::iter::Copied<std::slice::Iter<'graph, BasicBlock>>;
3447 impl<'tcx> graph::WithPredecessors for Body<'tcx> {
3449 fn predecessors(&self, node: Self::Node) -> <Self as graph::GraphPredecessors<'_>>::Iter {
3450 self.predecessors()[node].iter().copied()
3454 /// `Location` represents the position of the start of the statement; or, if
3455 /// `statement_index` equals the number of statements, then the start of the
3457 #[derive(Copy, Clone, PartialEq, Eq, Hash, Ord, PartialOrd, HashStable)]
3458 pub struct Location {
3459 /// The block that the location is within.
3460 pub block: BasicBlock,
3462 pub statement_index: usize,
3465 impl fmt::Debug for Location {
3466 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
3467 write!(fmt, "{:?}[{}]", self.block, self.statement_index)
3472 pub const START: Location = Location { block: START_BLOCK, statement_index: 0 };
3474 /// Returns the location immediately after this one within the enclosing block.
3476 /// Note that if this location represents a terminator, then the
3477 /// resulting location would be out of bounds and invalid.
3478 pub fn successor_within_block(&self) -> Location {
3479 Location { block: self.block, statement_index: self.statement_index + 1 }
3482 /// Returns `true` if `other` is earlier in the control flow graph than `self`.
3483 pub fn is_predecessor_of<'tcx>(&self, other: Location, body: &Body<'tcx>) -> bool {
3484 // If we are in the same block as the other location and are an earlier statement
3485 // then we are a predecessor of `other`.
3486 if self.block == other.block && self.statement_index < other.statement_index {
3490 let predecessors = body.predecessors();
3492 // If we're in another block, then we want to check that block is a predecessor of `other`.
3493 let mut queue: Vec<BasicBlock> = predecessors[other.block].to_vec();
3494 let mut visited = FxHashSet::default();
3496 while let Some(block) = queue.pop() {
3497 // If we haven't visited this block before, then make sure we visit its predecessors.
3498 if visited.insert(block) {
3499 queue.extend(predecessors[block].iter().cloned());
3504 // If we found the block that `self` is in, then we are a predecessor of `other` (since
3505 // we found that block by looking at the predecessors of `other`).
3506 if self.block == block {
3514 pub fn dominates(&self, other: Location, dominators: &Dominators<BasicBlock>) -> bool {
3515 if self.block == other.block {
3516 self.statement_index <= other.statement_index
3518 dominators.is_dominated_by(other.block, self.block)