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::{
7 AllocRange, ConstAllocation, ConstValue, GlobalAlloc, LitToConstInput, Scalar,
9 use crate::mir::visit::MirVisitable;
10 use crate::ty::adjustment::PointerCast;
11 use crate::ty::codec::{TyDecoder, TyEncoder};
12 use crate::ty::fold::{FallibleTypeFolder, TypeFoldable, TypeSuperFoldable, TypeVisitor};
13 use crate::ty::print::{FmtPrinter, Printer};
14 use crate::ty::subst::{GenericArg, InternalSubsts, Subst, SubstsRef};
15 use crate::ty::{self, List, Ty, TyCtxt};
16 use crate::ty::{AdtDef, InstanceDef, Region, ScalarInt, UserTypeAnnotationIndex};
18 use rustc_data_structures::captures::Captures;
19 use rustc_errors::ErrorGuaranteed;
20 use rustc_hir::def::{CtorKind, Namespace};
21 use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_ID};
22 use rustc_hir::{self, GeneratorKind};
23 use rustc_hir::{self as hir, HirId};
24 use rustc_session::Session;
25 use rustc_target::abi::{Size, VariantIdx};
27 use polonius_engine::Atom;
28 pub use rustc_ast::Mutability;
29 use rustc_data_structures::fx::FxHashSet;
30 use rustc_data_structures::graph::dominators::{dominators, Dominators};
31 use rustc_data_structures::graph::{self, GraphSuccessors};
32 use rustc_index::bit_set::BitMatrix;
33 use rustc_index::vec::{Idx, IndexVec};
34 use rustc_serialize::{Decodable, Encodable};
35 use rustc_span::symbol::Symbol;
36 use rustc_span::{Span, DUMMY_SP};
37 use rustc_target::asm::InlineAsmRegOrRegClass;
42 use std::convert::TryInto;
43 use std::fmt::{self, Debug, Display, Formatter, Write};
44 use std::ops::{ControlFlow, Index, IndexMut};
46 use std::{iter, mem, option};
48 use self::graph_cyclic_cache::GraphIsCyclicCache;
49 use self::predecessors::{PredecessorCache, Predecessors};
50 pub use self::query::*;
51 use self::switch_sources::{SwitchSourceCache, SwitchSources};
55 pub mod generic_graphviz;
56 mod graph_cyclic_cache;
68 use crate::mir::traversal::PostorderCache;
69 pub use terminator::*;
75 pub use self::generic_graph::graphviz_safe_def_name;
76 pub use self::graphviz::write_mir_graphviz;
77 pub use self::pretty::{
78 create_dump_file, display_allocation, dump_enabled, dump_mir, write_mir_pretty, PassWhere,
82 pub type LocalDecls<'tcx> = IndexVec<Local, LocalDecl<'tcx>>;
84 pub trait HasLocalDecls<'tcx> {
85 fn local_decls(&self) -> &LocalDecls<'tcx>;
88 impl<'tcx> HasLocalDecls<'tcx> for LocalDecls<'tcx> {
90 fn local_decls(&self) -> &LocalDecls<'tcx> {
95 impl<'tcx> HasLocalDecls<'tcx> for Body<'tcx> {
97 fn local_decls(&self) -> &LocalDecls<'tcx> {
102 /// A streamlined trait that you can implement to create a pass; the
103 /// pass will be named after the type, and it will consist of a main
104 /// loop that goes over each available MIR and applies `run_pass`.
105 pub trait MirPass<'tcx> {
106 fn name(&self) -> Cow<'_, str> {
107 let name = std::any::type_name::<Self>();
108 if let Some(tail) = name.rfind(':') {
109 Cow::from(&name[tail + 1..])
115 /// Returns `true` if this pass is enabled with the current combination of compiler flags.
116 fn is_enabled(&self, _sess: &Session) -> bool {
120 fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>);
122 /// If this pass causes the MIR to enter a new phase, return that phase.
123 fn phase_change(&self) -> Option<MirPhase> {
127 fn is_mir_dump_enabled(&self) -> bool {
132 /// The various "big phases" that MIR goes through.
134 /// These phases all describe dialects of MIR. Since all MIR uses the same datastructures, the
135 /// dialects forbid certain variants or values in certain phases. The sections below summarize the
136 /// changes, but do not document them thoroughly. The full documentation is found in the appropriate
137 /// documentation for the thing the change is affecting.
139 /// Warning: ordering of variants is significant.
140 #[derive(Copy, Clone, TyEncodable, TyDecodable, Debug, PartialEq, Eq, PartialOrd, Ord)]
141 #[derive(HashStable)]
143 /// The dialect of MIR used during all phases before `DropsLowered` is the same. This is also
144 /// the MIR that analysis such as borrowck uses.
146 /// One important thing to remember about the behavior of this section of MIR is that drop terminators
147 /// (including drop and replace) are *conditional*. The elaborate drops pass will then replace each
148 /// instance of a drop terminator with a nop, an unconditional drop, or a drop conditioned on a drop
149 /// flag. Of course, this means that it is important that the drop elaboration can accurately recognize
150 /// when things are initialized and when things are de-initialized. That means any code running on this
151 /// version of MIR must be sure to produce output that drop elaboration can reason about. See the
152 /// section on the drop terminatorss for more details.
154 // FIXME(oli-obk): it's unclear whether we still need this phase (and its corresponding query).
155 // We used to have this for pre-miri MIR based const eval.
157 /// This phase checks the MIR for promotable elements and takes them out of the main MIR body
158 /// by creating a new MIR body per promoted element. After this phase (and thus the termination
159 /// of the `mir_promoted` query), these promoted elements are available in the `promoted_mir`
162 /// Beginning with this phase, the following variants are disallowed:
163 /// * [`TerminatorKind::DropAndReplace`](terminator::TerminatorKind::DropAndReplace)
164 /// * [`TerminatorKind::FalseUnwind`](terminator::TerminatorKind::FalseUnwind)
165 /// * [`TerminatorKind::FalseEdge`](terminator::TerminatorKind::FalseEdge)
166 /// * [`StatementKind::FakeRead`]
167 /// * [`StatementKind::AscribeUserType`]
168 /// * [`Rvalue::Ref`] with `BorrowKind::Shallow`
170 /// And the following variant is allowed:
171 /// * [`StatementKind::Retag`]
173 /// Furthermore, `Drop` now uses explicit drop flags visible in the MIR and reaching a `Drop`
174 /// terminator means that the auto-generated drop glue will be invoked. Also, `Copy` operands
175 /// are allowed for non-`Copy` types.
177 /// After this projections may only contain deref projections as the first element.
179 /// Beginning with this phase, the following variant is disallowed:
180 /// * [`Rvalue::Aggregate`] for any `AggregateKind` except `Array`
182 /// And the following variant is allowed:
183 /// * [`StatementKind::SetDiscriminant`]
185 /// Before this phase, generators are in the "source code" form, featuring `yield` statements
186 /// and such. With this phase change, they are transformed into a proper state machine. Running
187 /// optimizations before this change can be potentially dangerous because the source code is to
188 /// some extent a "lie." In particular, `yield` terminators effectively make the value of all
189 /// locals visible to the caller. This means that dead store elimination before them, or code
190 /// motion across them, is not correct in general. This is also exasperated by type checking
191 /// having pre-computed a list of the types that it thinks are ok to be live across a yield
192 /// point - this is necessary to decide eg whether autotraits are implemented. Introducing new
193 /// types across a yield point will lead to ICEs becaues of this.
195 /// Beginning with this phase, the following variants are disallowed:
196 /// * [`TerminatorKind::Yield`](terminator::TerminatorKind::Yield)
197 /// * [`TerminatorKind::GeneratorDrop`](terminator::TerminatorKind::GeneratorDrop)
198 /// * [`ProjectionElem::Deref`] of `Box`
199 GeneratorsLowered = 6,
204 /// Gets the index of the current MirPhase within the set of all `MirPhase`s.
205 pub fn phase_index(&self) -> usize {
210 /// Where a specific `mir::Body` comes from.
211 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
212 #[derive(HashStable, TyEncodable, TyDecodable, TypeFoldable)]
213 pub struct MirSource<'tcx> {
214 pub instance: InstanceDef<'tcx>,
216 /// If `Some`, this is a promoted rvalue within the parent function.
217 pub promoted: Option<Promoted>,
220 impl<'tcx> MirSource<'tcx> {
221 pub fn item(def_id: DefId) -> Self {
223 instance: InstanceDef::Item(ty::WithOptConstParam::unknown(def_id)),
228 pub fn from_instance(instance: InstanceDef<'tcx>) -> Self {
229 MirSource { instance, promoted: None }
232 pub fn with_opt_param(self) -> ty::WithOptConstParam<DefId> {
233 self.instance.with_opt_param()
237 pub fn def_id(&self) -> DefId {
238 self.instance.def_id()
242 #[derive(Clone, TyEncodable, TyDecodable, Debug, HashStable, TypeFoldable)]
243 pub struct GeneratorInfo<'tcx> {
244 /// The yield type of the function, if it is a generator.
245 pub yield_ty: Option<Ty<'tcx>>,
247 /// Generator drop glue.
248 pub generator_drop: Option<Body<'tcx>>,
250 /// The layout of a generator. Produced by the state transformation.
251 pub generator_layout: Option<GeneratorLayout<'tcx>>,
253 /// If this is a generator then record the type of source expression that caused this generator
255 pub generator_kind: GeneratorKind,
258 /// The lowered representation of a single function.
259 #[derive(Clone, TyEncodable, TyDecodable, Debug, HashStable, TypeFoldable)]
260 pub struct Body<'tcx> {
261 /// A list of basic blocks. References to basic block use a newtyped index type [`BasicBlock`]
262 /// that indexes into this vector.
263 basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,
265 /// Records how far through the "desugaring and optimization" process this particular
266 /// MIR has traversed. This is particularly useful when inlining, since in that context
267 /// we instantiate the promoted constants and add them to our promoted vector -- but those
268 /// promoted items have already been optimized, whereas ours have not. This field allows
269 /// us to see the difference and forego optimization on the inlined promoted items.
272 pub source: MirSource<'tcx>,
274 /// A list of source scopes; these are referenced by statements
275 /// and used for debuginfo. Indexed by a `SourceScope`.
276 pub source_scopes: IndexVec<SourceScope, SourceScopeData<'tcx>>,
278 pub generator: Option<Box<GeneratorInfo<'tcx>>>,
280 /// Declarations of locals.
282 /// The first local is the return value pointer, followed by `arg_count`
283 /// locals for the function arguments, followed by any user-declared
284 /// variables and temporaries.
285 pub local_decls: LocalDecls<'tcx>,
287 /// User type annotations.
288 pub user_type_annotations: ty::CanonicalUserTypeAnnotations<'tcx>,
290 /// The number of arguments this function takes.
292 /// Starting at local 1, `arg_count` locals will be provided by the caller
293 /// and can be assumed to be initialized.
295 /// If this MIR was built for a constant, this will be 0.
296 pub arg_count: usize,
298 /// Mark an argument local (which must be a tuple) as getting passed as
299 /// its individual components at the LLVM level.
301 /// This is used for the "rust-call" ABI.
302 pub spread_arg: Option<Local>,
304 /// Debug information pertaining to user variables, including captures.
305 pub var_debug_info: Vec<VarDebugInfo<'tcx>>,
307 /// A span representing this MIR, for error reporting.
310 /// Constants that are required to evaluate successfully for this MIR to be well-formed.
311 /// We hold in this field all the constants we are not able to evaluate yet.
312 pub required_consts: Vec<Constant<'tcx>>,
314 /// Does this body use generic parameters. This is used for the `ConstEvaluatable` check.
316 /// Note that this does not actually mean that this body is not computable right now.
317 /// The repeat count in the following example is polymorphic, but can still be evaluated
318 /// without knowing anything about the type parameter `T`.
322 /// let _ = [0; std::mem::size_of::<*mut T>()];
326 /// **WARNING**: Do not change this flags after the MIR was originally created, even if an optimization
327 /// removed the last mention of all generic params. We do not want to rely on optimizations and
328 /// potentially allow things like `[u8; std::mem::size_of::<T>() * 0]` due to this.
329 pub is_polymorphic: bool,
331 predecessor_cache: PredecessorCache,
332 switch_source_cache: SwitchSourceCache,
333 is_cyclic: GraphIsCyclicCache,
334 postorder_cache: PostorderCache,
336 pub tainted_by_errors: Option<ErrorGuaranteed>,
339 impl<'tcx> Body<'tcx> {
341 source: MirSource<'tcx>,
342 basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,
343 source_scopes: IndexVec<SourceScope, SourceScopeData<'tcx>>,
344 local_decls: LocalDecls<'tcx>,
345 user_type_annotations: ty::CanonicalUserTypeAnnotations<'tcx>,
347 var_debug_info: Vec<VarDebugInfo<'tcx>>,
349 generator_kind: Option<GeneratorKind>,
350 tainted_by_errors: Option<ErrorGuaranteed>,
352 // We need `arg_count` locals, and one for the return place.
354 local_decls.len() > arg_count,
355 "expected at least {} locals, got {}",
360 let mut body = Body {
361 phase: MirPhase::Built,
365 generator: generator_kind.map(|generator_kind| {
366 Box::new(GeneratorInfo {
368 generator_drop: None,
369 generator_layout: None,
374 user_type_annotations,
379 required_consts: Vec::new(),
380 is_polymorphic: false,
381 predecessor_cache: PredecessorCache::new(),
382 switch_source_cache: SwitchSourceCache::new(),
383 is_cyclic: GraphIsCyclicCache::new(),
384 postorder_cache: PostorderCache::new(),
387 body.is_polymorphic = body.has_param_types_or_consts();
391 /// Returns a partially initialized MIR body containing only a list of basic blocks.
393 /// The returned MIR contains no `LocalDecl`s (even for the return place) or source scopes. It
394 /// is only useful for testing but cannot be `#[cfg(test)]` because it is used in a different
396 pub fn new_cfg_only(basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>) -> Self {
397 let mut body = Body {
398 phase: MirPhase::Built,
399 source: MirSource::item(CRATE_DEF_ID.to_def_id()),
401 source_scopes: IndexVec::new(),
403 local_decls: IndexVec::new(),
404 user_type_annotations: IndexVec::new(),
408 required_consts: Vec::new(),
409 var_debug_info: Vec::new(),
410 is_polymorphic: false,
411 predecessor_cache: PredecessorCache::new(),
412 switch_source_cache: SwitchSourceCache::new(),
413 is_cyclic: GraphIsCyclicCache::new(),
414 postorder_cache: PostorderCache::new(),
415 tainted_by_errors: None,
417 body.is_polymorphic = body.has_param_types_or_consts();
422 pub fn basic_blocks(&self) -> &IndexVec<BasicBlock, BasicBlockData<'tcx>> {
427 pub fn basic_blocks_mut(&mut self) -> &mut IndexVec<BasicBlock, BasicBlockData<'tcx>> {
428 // Because the user could mutate basic block terminators via this reference, we need to
429 // invalidate the caches.
431 // FIXME: Use a finer-grained API for this, so only transformations that alter terminators
432 // invalidate the caches.
433 self.predecessor_cache.invalidate();
434 self.switch_source_cache.invalidate();
435 self.is_cyclic.invalidate();
436 self.postorder_cache.invalidate();
437 &mut self.basic_blocks
441 pub fn basic_blocks_and_local_decls_mut(
443 ) -> (&mut IndexVec<BasicBlock, BasicBlockData<'tcx>>, &mut LocalDecls<'tcx>) {
444 self.predecessor_cache.invalidate();
445 self.switch_source_cache.invalidate();
446 self.is_cyclic.invalidate();
447 self.postorder_cache.invalidate();
448 (&mut self.basic_blocks, &mut self.local_decls)
452 pub fn basic_blocks_local_decls_mut_and_var_debug_info(
455 &mut IndexVec<BasicBlock, BasicBlockData<'tcx>>,
456 &mut LocalDecls<'tcx>,
457 &mut Vec<VarDebugInfo<'tcx>>,
459 self.predecessor_cache.invalidate();
460 self.switch_source_cache.invalidate();
461 self.is_cyclic.invalidate();
462 self.postorder_cache.invalidate();
463 (&mut self.basic_blocks, &mut self.local_decls, &mut self.var_debug_info)
466 /// Returns `true` if a cycle exists in the control-flow graph that is reachable from the
468 pub fn is_cfg_cyclic(&self) -> bool {
469 self.is_cyclic.is_cyclic(self)
473 pub fn local_kind(&self, local: Local) -> LocalKind {
474 let index = local.as_usize();
477 self.local_decls[local].mutability == Mutability::Mut,
478 "return place should be mutable"
481 LocalKind::ReturnPointer
482 } else if index < self.arg_count + 1 {
484 } else if self.local_decls[local].is_user_variable() {
491 /// Returns an iterator over all user-declared mutable locals.
493 pub fn mut_vars_iter<'a>(&'a self) -> impl Iterator<Item = Local> + Captures<'tcx> + 'a {
494 (self.arg_count + 1..self.local_decls.len()).filter_map(move |index| {
495 let local = Local::new(index);
496 let decl = &self.local_decls[local];
497 if decl.is_user_variable() && decl.mutability == Mutability::Mut {
505 /// Returns an iterator over all user-declared mutable arguments and locals.
507 pub fn mut_vars_and_args_iter<'a>(
509 ) -> impl Iterator<Item = Local> + Captures<'tcx> + 'a {
510 (1..self.local_decls.len()).filter_map(move |index| {
511 let local = Local::new(index);
512 let decl = &self.local_decls[local];
513 if (decl.is_user_variable() || index < self.arg_count + 1)
514 && decl.mutability == Mutability::Mut
523 /// Returns an iterator over all function arguments.
525 pub fn args_iter(&self) -> impl Iterator<Item = Local> + ExactSizeIterator {
526 (1..self.arg_count + 1).map(Local::new)
529 /// Returns an iterator over all user-defined variables and compiler-generated temporaries (all
530 /// locals that are neither arguments nor the return place).
532 pub fn vars_and_temps_iter(
534 ) -> impl DoubleEndedIterator<Item = Local> + ExactSizeIterator {
535 (self.arg_count + 1..self.local_decls.len()).map(Local::new)
539 pub fn drain_vars_and_temps<'a>(&'a mut self) -> impl Iterator<Item = LocalDecl<'tcx>> + 'a {
540 self.local_decls.drain(self.arg_count + 1..)
543 /// Changes a statement to a nop. This is both faster than deleting instructions and avoids
544 /// invalidating statement indices in `Location`s.
545 pub fn make_statement_nop(&mut self, location: Location) {
546 let block = &mut self.basic_blocks[location.block];
547 debug_assert!(location.statement_index < block.statements.len());
548 block.statements[location.statement_index].make_nop()
551 /// Returns the source info associated with `location`.
552 pub fn source_info(&self, location: Location) -> &SourceInfo {
553 let block = &self[location.block];
554 let stmts = &block.statements;
555 let idx = location.statement_index;
556 if idx < stmts.len() {
557 &stmts[idx].source_info
559 assert_eq!(idx, stmts.len());
560 &block.terminator().source_info
564 /// Returns the return type; it always return first element from `local_decls` array.
566 pub fn return_ty(&self) -> Ty<'tcx> {
567 self.local_decls[RETURN_PLACE].ty
570 /// Gets the location of the terminator for the given block.
572 pub fn terminator_loc(&self, bb: BasicBlock) -> Location {
573 Location { block: bb, statement_index: self[bb].statements.len() }
576 pub fn stmt_at(&self, location: Location) -> Either<&Statement<'tcx>, &Terminator<'tcx>> {
577 let Location { block, statement_index } = location;
578 let block_data = &self.basic_blocks[block];
581 .get(statement_index)
583 .unwrap_or_else(|| Either::Right(block_data.terminator()))
587 pub fn predecessors(&self) -> &Predecessors {
588 self.predecessor_cache.compute(&self.basic_blocks)
591 /// `body.switch_sources()[&(target, switch)]` returns a list of switch
592 /// values that lead to a `target` block from a `switch` block.
594 pub fn switch_sources(&self) -> &SwitchSources {
595 self.switch_source_cache.compute(&self.basic_blocks)
599 pub fn dominators(&self) -> Dominators<BasicBlock> {
604 pub fn yield_ty(&self) -> Option<Ty<'tcx>> {
605 self.generator.as_ref().and_then(|generator| generator.yield_ty)
609 pub fn generator_layout(&self) -> Option<&GeneratorLayout<'tcx>> {
610 self.generator.as_ref().and_then(|generator| generator.generator_layout.as_ref())
614 pub fn generator_drop(&self) -> Option<&Body<'tcx>> {
615 self.generator.as_ref().and_then(|generator| generator.generator_drop.as_ref())
619 pub fn generator_kind(&self) -> Option<GeneratorKind> {
620 self.generator.as_ref().map(|generator| generator.generator_kind)
624 #[derive(Copy, Clone, PartialEq, Eq, Debug, TyEncodable, TyDecodable, HashStable)]
627 /// Unsafe because of compiler-generated unsafe code, like `await` desugaring
629 /// Unsafe because of an unsafe fn
631 /// Unsafe because of an `unsafe` block
632 ExplicitUnsafe(hir::HirId),
635 impl<'tcx> Index<BasicBlock> for Body<'tcx> {
636 type Output = BasicBlockData<'tcx>;
639 fn index(&self, index: BasicBlock) -> &BasicBlockData<'tcx> {
640 &self.basic_blocks()[index]
644 impl<'tcx> IndexMut<BasicBlock> for Body<'tcx> {
646 fn index_mut(&mut self, index: BasicBlock) -> &mut BasicBlockData<'tcx> {
647 &mut self.basic_blocks_mut()[index]
651 #[derive(Copy, Clone, Debug, HashStable, TypeFoldable)]
652 pub enum ClearCrossCrate<T> {
657 impl<T> ClearCrossCrate<T> {
658 pub fn as_ref(&self) -> ClearCrossCrate<&T> {
660 ClearCrossCrate::Clear => ClearCrossCrate::Clear,
661 ClearCrossCrate::Set(v) => ClearCrossCrate::Set(v),
665 pub fn assert_crate_local(self) -> T {
667 ClearCrossCrate::Clear => bug!("unwrapping cross-crate data"),
668 ClearCrossCrate::Set(v) => v,
673 const TAG_CLEAR_CROSS_CRATE_CLEAR: u8 = 0;
674 const TAG_CLEAR_CROSS_CRATE_SET: u8 = 1;
676 impl<E: TyEncoder, T: Encodable<E>> Encodable<E> for ClearCrossCrate<T> {
678 fn encode(&self, e: &mut E) {
679 if E::CLEAR_CROSS_CRATE {
684 ClearCrossCrate::Clear => TAG_CLEAR_CROSS_CRATE_CLEAR.encode(e),
685 ClearCrossCrate::Set(ref val) => {
686 TAG_CLEAR_CROSS_CRATE_SET.encode(e);
692 impl<D: TyDecoder, T: Decodable<D>> Decodable<D> for ClearCrossCrate<T> {
694 fn decode(d: &mut D) -> ClearCrossCrate<T> {
695 if D::CLEAR_CROSS_CRATE {
696 return ClearCrossCrate::Clear;
699 let discr = u8::decode(d);
702 TAG_CLEAR_CROSS_CRATE_CLEAR => ClearCrossCrate::Clear,
703 TAG_CLEAR_CROSS_CRATE_SET => {
704 let val = T::decode(d);
705 ClearCrossCrate::Set(val)
707 tag => panic!("Invalid tag for ClearCrossCrate: {:?}", tag),
712 /// Grouped information about the source code origin of a MIR entity.
713 /// Intended to be inspected by diagnostics and debuginfo.
714 /// Most passes can work with it as a whole, within a single function.
715 // The unofficial Cranelift backend, at least as of #65828, needs `SourceInfo` to implement `Eq` and
716 // `Hash`. Please ping @bjorn3 if removing them.
717 #[derive(Copy, Clone, Debug, Eq, PartialEq, TyEncodable, TyDecodable, Hash, HashStable)]
718 pub struct SourceInfo {
719 /// The source span for the AST pertaining to this MIR entity.
722 /// The source scope, keeping track of which bindings can be
723 /// seen by debuginfo, active lint levels, `unsafe {...}`, etc.
724 pub scope: SourceScope,
729 pub fn outermost(span: Span) -> Self {
730 SourceInfo { span, scope: OUTERMOST_SOURCE_SCOPE }
734 ///////////////////////////////////////////////////////////////////////////
737 #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, TyEncodable, TyDecodable)]
738 #[derive(Hash, HashStable)]
739 pub enum BorrowKind {
740 /// Data must be immutable and is aliasable.
743 /// The immediately borrowed place must be immutable, but projections from
744 /// it don't need to be. For example, a shallow borrow of `a.b` doesn't
745 /// conflict with a mutable borrow of `a.b.c`.
747 /// This is used when lowering matches: when matching on a place we want to
748 /// ensure that place have the same value from the start of the match until
749 /// an arm is selected. This prevents this code from compiling:
750 /// ```compile_fail,E0510
751 /// let mut x = &Some(0);
754 /// Some(_) if { x = &None; false } => (),
758 /// This can't be a shared borrow because mutably borrowing (*x as Some).0
759 /// should not prevent `if let None = x { ... }`, for example, because the
760 /// mutating `(*x as Some).0` can't affect the discriminant of `x`.
761 /// We can also report errors with this kind of borrow differently.
764 /// Data must be immutable but not aliasable. This kind of borrow
765 /// cannot currently be expressed by the user and is used only in
766 /// implicit closure bindings. It is needed when the closure is
767 /// borrowing or mutating a mutable referent, e.g.:
770 /// let x: &mut isize = &mut z;
771 /// let y = || *x += 5;
773 /// If we were to try to translate this closure into a more explicit
774 /// form, we'd encounter an error with the code as written:
775 /// ```compile_fail,E0594
776 /// struct Env<'a> { x: &'a &'a mut isize }
778 /// let x: &mut isize = &mut z;
779 /// let y = (&mut Env { x: &x }, fn_ptr); // Closure is pair of env and fn
780 /// fn fn_ptr(env: &mut Env) { **env.x += 5; }
782 /// This is then illegal because you cannot mutate an `&mut` found
783 /// in an aliasable location. To solve, you'd have to translate with
784 /// an `&mut` borrow:
785 /// ```compile_fail,E0596
786 /// struct Env<'a> { x: &'a mut &'a mut isize }
788 /// let x: &mut isize = &mut z;
789 /// let y = (&mut Env { x: &mut x }, fn_ptr); // changed from &x to &mut x
790 /// fn fn_ptr(env: &mut Env) { **env.x += 5; }
792 /// Now the assignment to `**env.x` is legal, but creating a
793 /// mutable pointer to `x` is not because `x` is not mutable. We
794 /// could fix this by declaring `x` as `let mut x`. This is ok in
795 /// user code, if awkward, but extra weird for closures, since the
796 /// borrow is hidden.
798 /// So we introduce a "unique imm" borrow -- the referent is
799 /// immutable, but not aliasable. This solves the problem. For
800 /// simplicity, we don't give users the way to express this
801 /// borrow, it's just used when translating closures.
804 /// Data is mutable and not aliasable.
806 /// `true` if this borrow arose from method-call auto-ref
807 /// (i.e., `adjustment::Adjust::Borrow`).
808 allow_two_phase_borrow: bool,
813 pub fn allows_two_phase_borrow(&self) -> bool {
815 BorrowKind::Shared | BorrowKind::Shallow | BorrowKind::Unique => false,
816 BorrowKind::Mut { allow_two_phase_borrow } => allow_two_phase_borrow,
820 pub fn describe_mutability(&self) -> String {
822 BorrowKind::Shared | BorrowKind::Shallow | BorrowKind::Unique => {
823 "immutable".to_string()
825 BorrowKind::Mut { .. } => "mutable".to_string(),
830 ///////////////////////////////////////////////////////////////////////////
831 // Variables and temps
833 rustc_index::newtype_index! {
836 DEBUG_FORMAT = "_{}",
837 const RETURN_PLACE = 0,
841 impl Atom for Local {
842 fn index(self) -> usize {
847 /// Classifies locals into categories. See `Body::local_kind`.
848 #[derive(Clone, Copy, PartialEq, Eq, Debug, HashStable)]
850 /// User-declared variable binding.
852 /// Compiler-introduced temporary.
854 /// Function argument.
856 /// Location of function's return value.
860 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
861 pub struct VarBindingForm<'tcx> {
862 /// Is variable bound via `x`, `mut x`, `ref x`, or `ref mut x`?
863 pub binding_mode: ty::BindingMode,
864 /// If an explicit type was provided for this variable binding,
865 /// this holds the source Span of that type.
867 /// NOTE: if you want to change this to a `HirId`, be wary that
868 /// doing so breaks incremental compilation (as of this writing),
869 /// while a `Span` does not cause our tests to fail.
870 pub opt_ty_info: Option<Span>,
871 /// Place of the RHS of the =, or the subject of the `match` where this
872 /// variable is initialized. None in the case of `let PATTERN;`.
873 /// Some((None, ..)) in the case of and `let [mut] x = ...` because
874 /// (a) the right-hand side isn't evaluated as a place expression.
875 /// (b) it gives a way to separate this case from the remaining cases
877 pub opt_match_place: Option<(Option<Place<'tcx>>, Span)>,
878 /// The span of the pattern in which this variable was bound.
882 #[derive(Clone, Debug, TyEncodable, TyDecodable)]
883 pub enum BindingForm<'tcx> {
884 /// This is a binding for a non-`self` binding, or a `self` that has an explicit type.
885 Var(VarBindingForm<'tcx>),
886 /// Binding for a `self`/`&self`/`&mut self` binding where the type is implicit.
887 ImplicitSelf(ImplicitSelfKind),
888 /// Reference used in a guard expression to ensure immutability.
892 /// Represents what type of implicit self a function has, if any.
893 #[derive(Clone, Copy, PartialEq, Debug, TyEncodable, TyDecodable, HashStable)]
894 pub enum ImplicitSelfKind {
895 /// Represents a `fn x(self);`.
897 /// Represents a `fn x(mut self);`.
899 /// Represents a `fn x(&self);`.
901 /// Represents a `fn x(&mut self);`.
903 /// Represents when a function does not have a self argument or
904 /// when a function has a `self: X` argument.
908 TrivialTypeFoldableAndLiftImpls! { BindingForm<'tcx>, }
910 mod binding_form_impl {
911 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
912 use rustc_query_system::ich::StableHashingContext;
914 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for super::BindingForm<'tcx> {
915 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
916 use super::BindingForm::*;
917 std::mem::discriminant(self).hash_stable(hcx, hasher);
920 Var(binding) => binding.hash_stable(hcx, hasher),
921 ImplicitSelf(kind) => kind.hash_stable(hcx, hasher),
928 /// `BlockTailInfo` is attached to the `LocalDecl` for temporaries
929 /// created during evaluation of expressions in a block tail
930 /// expression; that is, a block like `{ STMT_1; STMT_2; EXPR }`.
932 /// It is used to improve diagnostics when such temporaries are
933 /// involved in borrow_check errors, e.g., explanations of where the
934 /// temporaries come from, when their destructors are run, and/or how
935 /// one might revise the code to satisfy the borrow checker's rules.
936 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
937 pub struct BlockTailInfo {
938 /// If `true`, then the value resulting from evaluating this tail
939 /// expression is ignored by the block's expression context.
941 /// Examples include `{ ...; tail };` and `let _ = { ...; tail };`
942 /// but not e.g., `let _x = { ...; tail };`
943 pub tail_result_is_ignored: bool,
945 /// `Span` of the tail expression.
951 /// This can be a binding declared by the user, a temporary inserted by the compiler, a function
952 /// argument, or the return place.
953 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
954 pub struct LocalDecl<'tcx> {
955 /// Whether this is a mutable binding (i.e., `let x` or `let mut x`).
957 /// Temporaries and the return place are always mutable.
958 pub mutability: Mutability,
960 // FIXME(matthewjasper) Don't store in this in `Body`
961 pub local_info: Option<Box<LocalInfo<'tcx>>>,
963 /// `true` if this is an internal local.
965 /// These locals are not based on types in the source code and are only used
966 /// for a few desugarings at the moment.
968 /// The generator transformation will sanity check the locals which are live
969 /// across a suspension point against the type components of the generator
970 /// which type checking knows are live across a suspension point. We need to
971 /// flag drop flags to avoid triggering this check as they are introduced
972 /// outside of type inference.
974 /// This should be sound because the drop flags are fully algebraic, and
975 /// therefore don't affect the auto-trait or outlives properties of the
979 /// If this local is a temporary and `is_block_tail` is `Some`,
980 /// then it is a temporary created for evaluation of some
981 /// subexpression of some block's tail expression (with no
982 /// intervening statement context).
983 // FIXME(matthewjasper) Don't store in this in `Body`
984 pub is_block_tail: Option<BlockTailInfo>,
986 /// The type of this local.
989 /// If the user manually ascribed a type to this variable,
990 /// e.g., via `let x: T`, then we carry that type here. The MIR
991 /// borrow checker needs this information since it can affect
992 /// region inference.
993 // FIXME(matthewjasper) Don't store in this in `Body`
994 pub user_ty: Option<Box<UserTypeProjections>>,
996 /// The *syntactic* (i.e., not visibility) source scope the local is defined
997 /// in. If the local was defined in a let-statement, this
998 /// is *within* the let-statement, rather than outside
1001 /// This is needed because the visibility source scope of locals within
1002 /// a let-statement is weird.
1004 /// The reason is that we want the local to be *within* the let-statement
1005 /// for lint purposes, but we want the local to be *after* the let-statement
1006 /// for names-in-scope purposes.
1008 /// That's it, if we have a let-statement like the one in this
1012 /// fn foo(x: &str) {
1013 /// #[allow(unused_mut)]
1014 /// let mut x: u32 = { // <- one unused mut
1015 /// let mut y: u32 = x.parse().unwrap();
1022 /// Then, from a lint point of view, the declaration of `x: u32`
1023 /// (and `y: u32`) are within the `#[allow(unused_mut)]` scope - the
1024 /// lint scopes are the same as the AST/HIR nesting.
1026 /// However, from a name lookup point of view, the scopes look more like
1027 /// as if the let-statements were `match` expressions:
1030 /// fn foo(x: &str) {
1032 /// match x.parse::<u32>().unwrap() {
1041 /// We care about the name-lookup scopes for debuginfo - if the
1042 /// debuginfo instruction pointer is at the call to `x.parse()`, we
1043 /// want `x` to refer to `x: &str`, but if it is at the call to
1044 /// `drop(x)`, we want it to refer to `x: u32`.
1046 /// To allow both uses to work, we need to have more than a single scope
1047 /// for a local. We have the `source_info.scope` represent the "syntactic"
1048 /// lint scope (with a variable being under its let block) while the
1049 /// `var_debug_info.source_info.scope` represents the "local variable"
1050 /// scope (where the "rest" of a block is under all prior let-statements).
1052 /// The end result looks like this:
1056 /// │{ argument x: &str }
1058 /// │ │{ #[allow(unused_mut)] } // This is actually split into 2 scopes
1059 /// │ │ // in practice because I'm lazy.
1061 /// │ │← x.source_info.scope
1062 /// │ │← `x.parse().unwrap()`
1064 /// │ │ │← y.source_info.scope
1066 /// │ │ │{ let y: u32 }
1068 /// │ │ │← y.var_debug_info.source_info.scope
1071 /// │ │{ let x: u32 }
1072 /// │ │← x.var_debug_info.source_info.scope
1073 /// │ │← `drop(x)` // This accesses `x: u32`.
1075 pub source_info: SourceInfo,
1078 // `LocalDecl` is used a lot. Make sure it doesn't unintentionally get bigger.
1079 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
1080 static_assert_size!(LocalDecl<'_>, 56);
1082 /// Extra information about a some locals that's used for diagnostics and for
1083 /// classifying variables into local variables, statics, etc, which is needed e.g.
1084 /// for unsafety checking.
1086 /// Not used for non-StaticRef temporaries, the return place, or anonymous
1087 /// function parameters.
1088 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
1089 pub enum LocalInfo<'tcx> {
1090 /// A user-defined local variable or function parameter
1092 /// The `BindingForm` is solely used for local diagnostics when generating
1093 /// warnings/errors when compiling the current crate, and therefore it need
1094 /// not be visible across crates.
1095 User(ClearCrossCrate<BindingForm<'tcx>>),
1096 /// A temporary created that references the static with the given `DefId`.
1097 StaticRef { def_id: DefId, is_thread_local: bool },
1098 /// A temporary created that references the const with the given `DefId`
1099 ConstRef { def_id: DefId },
1100 /// A temporary created during the creation of an aggregate
1101 /// (e.g. a temporary for `foo` in `MyStruct { my_field: foo }`)
1103 /// A temporary created during the pass `Derefer` to avoid it's retagging
1107 impl<'tcx> LocalDecl<'tcx> {
1108 /// Returns `true` only if local is a binding that can itself be
1109 /// made mutable via the addition of the `mut` keyword, namely
1110 /// something like the occurrences of `x` in:
1111 /// - `fn foo(x: Type) { ... }`,
1112 /// - `let x = ...`,
1113 /// - or `match ... { C(x) => ... }`
1114 pub fn can_be_made_mutable(&self) -> bool {
1117 Some(box LocalInfo::User(ClearCrossCrate::Set(
1118 BindingForm::Var(VarBindingForm {
1119 binding_mode: ty::BindingMode::BindByValue(_),
1123 }) | BindingForm::ImplicitSelf(ImplicitSelfKind::Imm),
1128 /// Returns `true` if local is definitely not a `ref ident` or
1129 /// `ref mut ident` binding. (Such bindings cannot be made into
1130 /// mutable bindings, but the inverse does not necessarily hold).
1131 pub fn is_nonref_binding(&self) -> bool {
1134 Some(box LocalInfo::User(ClearCrossCrate::Set(
1135 BindingForm::Var(VarBindingForm {
1136 binding_mode: ty::BindingMode::BindByValue(_),
1140 }) | BindingForm::ImplicitSelf(_),
1145 /// Returns `true` if this variable is a named variable or function
1146 /// parameter declared by the user.
1148 pub fn is_user_variable(&self) -> bool {
1149 matches!(self.local_info, Some(box LocalInfo::User(_)))
1152 /// Returns `true` if this is a reference to a variable bound in a `match`
1153 /// expression that is used to access said variable for the guard of the
1155 pub fn is_ref_for_guard(&self) -> bool {
1158 Some(box LocalInfo::User(ClearCrossCrate::Set(BindingForm::RefForGuard)))
1162 /// Returns `Some` if this is a reference to a static item that is used to
1163 /// access that static.
1164 pub fn is_ref_to_static(&self) -> bool {
1165 matches!(self.local_info, Some(box LocalInfo::StaticRef { .. }))
1168 /// Returns `Some` if this is a reference to a thread-local static item that is used to
1169 /// access that static.
1170 pub fn is_ref_to_thread_local(&self) -> bool {
1171 match self.local_info {
1172 Some(box LocalInfo::StaticRef { is_thread_local, .. }) => is_thread_local,
1177 /// Returns `true` is the local is from a compiler desugaring, e.g.,
1178 /// `__next` from a `for` loop.
1180 pub fn from_compiler_desugaring(&self) -> bool {
1181 self.source_info.span.desugaring_kind().is_some()
1184 /// Creates a new `LocalDecl` for a temporary: mutable, non-internal.
1186 pub fn new(ty: Ty<'tcx>, span: Span) -> Self {
1187 Self::with_source_info(ty, SourceInfo::outermost(span))
1190 /// Like `LocalDecl::new`, but takes a `SourceInfo` instead of a `Span`.
1192 pub fn with_source_info(ty: Ty<'tcx>, source_info: SourceInfo) -> Self {
1194 mutability: Mutability::Mut,
1197 is_block_tail: None,
1204 /// Converts `self` into same `LocalDecl` except tagged as internal.
1206 pub fn internal(mut self) -> Self {
1207 self.internal = true;
1211 /// Converts `self` into same `LocalDecl` except tagged as immutable.
1213 pub fn immutable(mut self) -> Self {
1214 self.mutability = Mutability::Not;
1218 /// Converts `self` into same `LocalDecl` except tagged as internal temporary.
1220 pub fn block_tail(mut self, info: BlockTailInfo) -> Self {
1221 assert!(self.is_block_tail.is_none());
1222 self.is_block_tail = Some(info);
1227 #[derive(Clone, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
1228 pub enum VarDebugInfoContents<'tcx> {
1229 /// NOTE(eddyb) There's an unenforced invariant that this `Place` is
1230 /// based on a `Local`, not a `Static`, and contains no indexing.
1232 Const(Constant<'tcx>),
1235 impl<'tcx> Debug for VarDebugInfoContents<'tcx> {
1236 fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
1238 VarDebugInfoContents::Const(c) => write!(fmt, "{}", c),
1239 VarDebugInfoContents::Place(p) => write!(fmt, "{:?}", p),
1244 /// Debug information pertaining to a user variable.
1245 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
1246 pub struct VarDebugInfo<'tcx> {
1249 /// Source info of the user variable, including the scope
1250 /// within which the variable is visible (to debuginfo)
1251 /// (see `LocalDecl`'s `source_info` field for more details).
1252 pub source_info: SourceInfo,
1254 /// Where the data for this user variable is to be found.
1255 pub value: VarDebugInfoContents<'tcx>,
1258 ///////////////////////////////////////////////////////////////////////////
1261 rustc_index::newtype_index! {
1262 /// A node in the MIR [control-flow graph][CFG].
1264 /// There are no branches (e.g., `if`s, function calls, etc.) within a basic block, which makes
1265 /// it easier to do [data-flow analyses] and optimizations. Instead, branches are represented
1266 /// as an edge in a graph between basic blocks.
1268 /// Basic blocks consist of a series of [statements][Statement], ending with a
1269 /// [terminator][Terminator]. Basic blocks can have multiple predecessors and successors,
1270 /// however there is a MIR pass ([`CriticalCallEdges`]) that removes *critical edges*, which
1271 /// are edges that go from a multi-successor node to a multi-predecessor node. This pass is
1272 /// needed because some analyses require that there are no critical edges in the CFG.
1274 /// Note that this type is just an index into [`Body.basic_blocks`](Body::basic_blocks);
1275 /// the actual data that a basic block holds is in [`BasicBlockData`].
1277 /// Read more about basic blocks in the [rustc-dev-guide][guide-mir].
1279 /// [CFG]: https://rustc-dev-guide.rust-lang.org/appendix/background.html#cfg
1280 /// [data-flow analyses]:
1281 /// https://rustc-dev-guide.rust-lang.org/appendix/background.html#what-is-a-dataflow-analysis
1282 /// [`CriticalCallEdges`]: ../../rustc_const_eval/transform/add_call_guards/enum.AddCallGuards.html#variant.CriticalCallEdges
1283 /// [guide-mir]: https://rustc-dev-guide.rust-lang.org/mir/
1284 pub struct BasicBlock {
1286 DEBUG_FORMAT = "bb{}",
1287 const START_BLOCK = 0,
1292 pub fn start_location(self) -> Location {
1293 Location { block: self, statement_index: 0 }
1297 ///////////////////////////////////////////////////////////////////////////
1298 // BasicBlockData and Terminator
1300 /// See [`BasicBlock`] for documentation on what basic blocks are at a high level.
1301 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
1302 pub struct BasicBlockData<'tcx> {
1303 /// List of statements in this block.
1304 pub statements: Vec<Statement<'tcx>>,
1306 /// Terminator for this block.
1308 /// N.B., this should generally ONLY be `None` during construction.
1309 /// Therefore, you should generally access it via the
1310 /// `terminator()` or `terminator_mut()` methods. The only
1311 /// exception is that certain passes, such as `simplify_cfg`, swap
1312 /// out the terminator temporarily with `None` while they continue
1313 /// to recurse over the set of basic blocks.
1314 pub terminator: Option<Terminator<'tcx>>,
1316 /// If true, this block lies on an unwind path. This is used
1317 /// during codegen where distinct kinds of basic blocks may be
1318 /// generated (particularly for MSVC cleanup). Unwind blocks must
1319 /// only branch to other unwind blocks.
1320 pub is_cleanup: bool,
1323 /// Information about an assertion failure.
1324 #[derive(Clone, TyEncodable, TyDecodable, Hash, HashStable, PartialEq, PartialOrd)]
1325 pub enum AssertKind<O> {
1326 BoundsCheck { len: O, index: O },
1327 Overflow(BinOp, O, O),
1331 ResumedAfterReturn(GeneratorKind),
1332 ResumedAfterPanic(GeneratorKind),
1335 #[derive(Clone, Debug, PartialEq, TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable)]
1336 pub enum InlineAsmOperand<'tcx> {
1338 reg: InlineAsmRegOrRegClass,
1339 value: Operand<'tcx>,
1342 reg: InlineAsmRegOrRegClass,
1344 place: Option<Place<'tcx>>,
1347 reg: InlineAsmRegOrRegClass,
1349 in_value: Operand<'tcx>,
1350 out_place: Option<Place<'tcx>>,
1353 value: Box<Constant<'tcx>>,
1356 value: Box<Constant<'tcx>>,
1363 /// Type for MIR `Assert` terminator error messages.
1364 pub type AssertMessage<'tcx> = AssertKind<Operand<'tcx>>;
1366 pub type Successors<'a> = impl Iterator<Item = BasicBlock> + 'a;
1367 pub type SuccessorsMut<'a> =
1368 iter::Chain<option::IntoIter<&'a mut BasicBlock>, slice::IterMut<'a, BasicBlock>>;
1370 impl<'tcx> BasicBlockData<'tcx> {
1371 pub fn new(terminator: Option<Terminator<'tcx>>) -> BasicBlockData<'tcx> {
1372 BasicBlockData { statements: vec![], terminator, is_cleanup: false }
1375 /// Accessor for terminator.
1377 /// Terminator may not be None after construction of the basic block is complete. This accessor
1378 /// provides a convenience way to reach the terminator.
1380 pub fn terminator(&self) -> &Terminator<'tcx> {
1381 self.terminator.as_ref().expect("invalid terminator state")
1385 pub fn terminator_mut(&mut self) -> &mut Terminator<'tcx> {
1386 self.terminator.as_mut().expect("invalid terminator state")
1389 pub fn retain_statements<F>(&mut self, mut f: F)
1391 F: FnMut(&mut Statement<'_>) -> bool,
1393 for s in &mut self.statements {
1400 pub fn expand_statements<F, I>(&mut self, mut f: F)
1402 F: FnMut(&mut Statement<'tcx>) -> Option<I>,
1403 I: iter::TrustedLen<Item = Statement<'tcx>>,
1405 // Gather all the iterators we'll need to splice in, and their positions.
1406 let mut splices: Vec<(usize, I)> = vec![];
1407 let mut extra_stmts = 0;
1408 for (i, s) in self.statements.iter_mut().enumerate() {
1409 if let Some(mut new_stmts) = f(s) {
1410 if let Some(first) = new_stmts.next() {
1411 // We can already store the first new statement.
1414 // Save the other statements for optimized splicing.
1415 let remaining = new_stmts.size_hint().0;
1417 splices.push((i + 1 + extra_stmts, new_stmts));
1418 extra_stmts += remaining;
1426 // Splice in the new statements, from the end of the block.
1427 // FIXME(eddyb) This could be more efficient with a "gap buffer"
1428 // where a range of elements ("gap") is left uninitialized, with
1429 // splicing adding new elements to the end of that gap and moving
1430 // existing elements from before the gap to the end of the gap.
1431 // For now, this is safe code, emulating a gap but initializing it.
1432 let mut gap = self.statements.len()..self.statements.len() + extra_stmts;
1433 self.statements.resize(
1435 Statement { source_info: SourceInfo::outermost(DUMMY_SP), kind: StatementKind::Nop },
1437 for (splice_start, new_stmts) in splices.into_iter().rev() {
1438 let splice_end = splice_start + new_stmts.size_hint().0;
1439 while gap.end > splice_end {
1442 self.statements.swap(gap.start, gap.end);
1444 self.statements.splice(splice_start..splice_end, new_stmts);
1445 gap.end = splice_start;
1449 pub fn visitable(&self, index: usize) -> &dyn MirVisitable<'tcx> {
1450 if index < self.statements.len() { &self.statements[index] } else { &self.terminator }
1454 impl<O> AssertKind<O> {
1455 /// Getting a description does not require `O` to be printable, and does not
1456 /// require allocation.
1457 /// The caller is expected to handle `BoundsCheck` separately.
1458 pub fn description(&self) -> &'static str {
1461 Overflow(BinOp::Add, _, _) => "attempt to add with overflow",
1462 Overflow(BinOp::Sub, _, _) => "attempt to subtract with overflow",
1463 Overflow(BinOp::Mul, _, _) => "attempt to multiply with overflow",
1464 Overflow(BinOp::Div, _, _) => "attempt to divide with overflow",
1465 Overflow(BinOp::Rem, _, _) => "attempt to calculate the remainder with overflow",
1466 OverflowNeg(_) => "attempt to negate with overflow",
1467 Overflow(BinOp::Shr, _, _) => "attempt to shift right with overflow",
1468 Overflow(BinOp::Shl, _, _) => "attempt to shift left with overflow",
1469 Overflow(op, _, _) => bug!("{:?} cannot overflow", op),
1470 DivisionByZero(_) => "attempt to divide by zero",
1471 RemainderByZero(_) => "attempt to calculate the remainder with a divisor of zero",
1472 ResumedAfterReturn(GeneratorKind::Gen) => "generator resumed after completion",
1473 ResumedAfterReturn(GeneratorKind::Async(_)) => "`async fn` resumed after completion",
1474 ResumedAfterPanic(GeneratorKind::Gen) => "generator resumed after panicking",
1475 ResumedAfterPanic(GeneratorKind::Async(_)) => "`async fn` resumed after panicking",
1476 BoundsCheck { .. } => bug!("Unexpected AssertKind"),
1480 /// Format the message arguments for the `assert(cond, msg..)` terminator in MIR printing.
1481 pub fn fmt_assert_args<W: Write>(&self, f: &mut W) -> fmt::Result
1487 BoundsCheck { ref len, ref index } => write!(
1489 "\"index out of bounds: the length is {{}} but the index is {{}}\", {:?}, {:?}",
1493 OverflowNeg(op) => {
1494 write!(f, "\"attempt to negate `{{}}`, which would overflow\", {:?}", op)
1496 DivisionByZero(op) => write!(f, "\"attempt to divide `{{}}` by zero\", {:?}", op),
1497 RemainderByZero(op) => write!(
1499 "\"attempt to calculate the remainder of `{{}}` with a divisor of zero\", {:?}",
1502 Overflow(BinOp::Add, l, r) => write!(
1504 "\"attempt to compute `{{}} + {{}}`, which would overflow\", {:?}, {:?}",
1507 Overflow(BinOp::Sub, l, r) => write!(
1509 "\"attempt to compute `{{}} - {{}}`, which would overflow\", {:?}, {:?}",
1512 Overflow(BinOp::Mul, l, r) => write!(
1514 "\"attempt to compute `{{}} * {{}}`, which would overflow\", {:?}, {:?}",
1517 Overflow(BinOp::Div, l, r) => write!(
1519 "\"attempt to compute `{{}} / {{}}`, which would overflow\", {:?}, {:?}",
1522 Overflow(BinOp::Rem, l, r) => write!(
1524 "\"attempt to compute the remainder of `{{}} % {{}}`, which would overflow\", {:?}, {:?}",
1527 Overflow(BinOp::Shr, _, r) => {
1528 write!(f, "\"attempt to shift right by `{{}}`, which would overflow\", {:?}", r)
1530 Overflow(BinOp::Shl, _, r) => {
1531 write!(f, "\"attempt to shift left by `{{}}`, which would overflow\", {:?}", r)
1533 _ => write!(f, "\"{}\"", self.description()),
1538 impl<O: fmt::Debug> fmt::Debug for AssertKind<O> {
1539 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1542 BoundsCheck { ref len, ref index } => write!(
1544 "index out of bounds: the length is {:?} but the index is {:?}",
1547 OverflowNeg(op) => write!(f, "attempt to negate `{:#?}`, which would overflow", op),
1548 DivisionByZero(op) => write!(f, "attempt to divide `{:#?}` by zero", op),
1549 RemainderByZero(op) => write!(
1551 "attempt to calculate the remainder of `{:#?}` with a divisor of zero",
1554 Overflow(BinOp::Add, l, r) => {
1555 write!(f, "attempt to compute `{:#?} + {:#?}`, which would overflow", l, r)
1557 Overflow(BinOp::Sub, l, r) => {
1558 write!(f, "attempt to compute `{:#?} - {:#?}`, which would overflow", l, r)
1560 Overflow(BinOp::Mul, l, r) => {
1561 write!(f, "attempt to compute `{:#?} * {:#?}`, which would overflow", l, r)
1563 Overflow(BinOp::Div, l, r) => {
1564 write!(f, "attempt to compute `{:#?} / {:#?}`, which would overflow", l, r)
1566 Overflow(BinOp::Rem, l, r) => write!(
1568 "attempt to compute the remainder of `{:#?} % {:#?}`, which would overflow",
1571 Overflow(BinOp::Shr, _, r) => {
1572 write!(f, "attempt to shift right by `{:#?}`, which would overflow", r)
1574 Overflow(BinOp::Shl, _, r) => {
1575 write!(f, "attempt to shift left by `{:#?}`, which would overflow", r)
1577 _ => write!(f, "{}", self.description()),
1582 ///////////////////////////////////////////////////////////////////////////
1585 #[derive(Clone, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
1586 pub struct Statement<'tcx> {
1587 pub source_info: SourceInfo,
1588 pub kind: StatementKind<'tcx>,
1591 // `Statement` is used a lot. Make sure it doesn't unintentionally get bigger.
1592 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
1593 static_assert_size!(Statement<'_>, 32);
1595 impl Statement<'_> {
1596 /// Changes a statement to a nop. This is both faster than deleting instructions and avoids
1597 /// invalidating statement indices in `Location`s.
1598 pub fn make_nop(&mut self) {
1599 self.kind = StatementKind::Nop
1602 /// Changes a statement to a nop and returns the original statement.
1603 #[must_use = "If you don't need the statement, use `make_nop` instead"]
1604 pub fn replace_nop(&mut self) -> Self {
1606 source_info: self.source_info,
1607 kind: mem::replace(&mut self.kind, StatementKind::Nop),
1612 /// The various kinds of statements that can appear in MIR.
1614 /// Not all of these are allowed at every [`MirPhase`]. Check the documentation there to see which
1615 /// ones you do not have to worry about. The MIR validator will generally enforce such restrictions,
1616 /// causing an ICE if they are violated.
1617 #[derive(Clone, Debug, PartialEq, TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable)]
1618 pub enum StatementKind<'tcx> {
1619 /// Assign statements roughly correspond to an assignment in Rust proper (`x = ...`) except
1620 /// without the possibility of dropping the previous value (that must be done separately, if at
1621 /// all). The *exact* way this works is undecided. It probably does something like evaluating
1622 /// the LHS to a place and the RHS to a value, and then storing the value to the place. Various
1623 /// parts of this may do type specific things that are more complicated than simply copying
1626 /// **Needs clarification**: The implication of the above idea would be that assignment implies
1627 /// that the resulting value is initialized. I believe we could commit to this separately from
1628 /// committing to whatever part of the memory model we would need to decide on to make the above
1629 /// paragragh precise. Do we want to?
1631 /// Assignments in which the types of the place and rvalue differ are not well-formed.
1633 /// **Needs clarification**: Do we ever want to worry about non-free (in the body) lifetimes for
1634 /// the typing requirement in post drop-elaboration MIR? I think probably not - I'm not sure we
1635 /// could meaningfully require this anyway. How about free lifetimes? Is ignoring this
1636 /// interesting for optimizations? Do we want to allow such optimizations?
1638 /// **Needs clarification**: We currently require that the LHS place not overlap with any place
1639 /// read as part of computation of the RHS for some rvalues (generally those not producing
1640 /// primitives). This requirement is under discussion in [#68364]. As a part of this discussion,
1641 /// it is also unclear in what order the components are evaluated.
1643 /// [#68364]: https://github.com/rust-lang/rust/issues/68364
1645 /// See [`Rvalue`] documentation for details on each of those.
1646 Assign(Box<(Place<'tcx>, Rvalue<'tcx>)>),
1648 /// This represents all the reading that a pattern match may do (e.g., inspecting constants and
1649 /// discriminant values), and the kind of pattern it comes from. This is in order to adapt
1650 /// potential error messages to these specific patterns.
1652 /// Note that this also is emitted for regular `let` bindings to ensure that locals that are
1653 /// never accessed still get some sanity checks for, e.g., `let x: ! = ..;`
1655 /// When executed at runtime this is a nop.
1657 /// Disallowed after drop elaboration.
1658 FakeRead(Box<(FakeReadCause, Place<'tcx>)>),
1660 /// Write the discriminant for a variant to the enum Place.
1662 /// This is permitted for both generators and ADTs. This does not necessarily write to the
1663 /// entire place; instead, it writes to the minimum set of bytes as required by the layout for
1665 SetDiscriminant { place: Box<Place<'tcx>>, variant_index: VariantIdx },
1667 /// Deinitializes the place.
1669 /// This writes `uninit` bytes to the entire place.
1670 Deinit(Box<Place<'tcx>>),
1672 /// `StorageLive` and `StorageDead` statements mark the live range of a local.
1674 /// Using a local before a `StorageLive` or after a `StorageDead` is not well-formed. These
1675 /// statements are not required. If the entire MIR body contains no `StorageLive`/`StorageDead`
1676 /// statements for a particular local, the local is always considered live.
1678 /// More precisely, the MIR validator currently does a `MaybeStorageLiveLocals` analysis to
1679 /// check validity of each use of a local. I believe this is equivalent to requiring for every
1680 /// use of a local, there exist at least one path from the root to that use that contains a
1681 /// `StorageLive` more recently than a `StorageDead`.
1683 /// **Needs clarification**: Is it permitted to have two `StorageLive`s without an intervening
1684 /// `StorageDead`? Two `StorageDead`s without an intervening `StorageLive`? LLVM says poison,
1685 /// yes. If the answer to any of these is "no," is breaking that rule UB or is it an error to
1686 /// have a path in the CFG that might do this?
1689 /// See `StorageLive` above.
1692 /// Retag references in the given place, ensuring they got fresh tags.
1694 /// This is part of the Stacked Borrows model. These statements are currently only interpreted
1695 /// by miri and only generated when `-Z mir-emit-retag` is passed. See
1696 /// <https://internals.rust-lang.org/t/stacked-borrows-an-aliasing-model-for-rust/8153/> for
1699 /// For code that is not specific to stacked borrows, you should consider retags to read
1700 /// and modify the place in an opaque way.
1701 Retag(RetagKind, Box<Place<'tcx>>),
1703 /// Encodes a user's type ascription. These need to be preserved
1704 /// intact so that NLL can respect them. For example:
1705 /// ```ignore (illustrative)
1708 /// The effect of this annotation is to relate the type `T_y` of the place `y`
1709 /// to the user-given type `T`. The effect depends on the specified variance:
1711 /// - `Covariant` -- requires that `T_y <: T`
1712 /// - `Contravariant` -- requires that `T_y :> T`
1713 /// - `Invariant` -- requires that `T_y == T`
1714 /// - `Bivariant` -- no effect
1716 /// When executed at runtime this is a nop.
1718 /// Disallowed after drop elaboration.
1719 AscribeUserType(Box<(Place<'tcx>, UserTypeProjection)>, ty::Variance),
1721 /// Marks the start of a "coverage region", injected with '-Cinstrument-coverage'. A
1722 /// `Coverage` statement carries metadata about the coverage region, used to inject a coverage
1723 /// map into the binary. If `Coverage::kind` is a `Counter`, the statement also generates
1724 /// executable code, to increment a counter variable at runtime, each time the code region is
1726 Coverage(Box<Coverage>),
1728 /// Denotes a call to the intrinsic function `copy_nonoverlapping`.
1730 /// First, all three operands are evaluated. `src` and `dest` must each be a reference, pointer,
1731 /// or `Box` pointing to the same type `T`. `count` must evaluate to a `usize`. Then, `src` and
1732 /// `dest` are dereferenced, and `count * size_of::<T>()` bytes beginning with the first byte of
1733 /// the `src` place are copied to the continguous range of bytes beginning with the first byte
1736 /// **Needs clarification**: In what order are operands computed and dereferenced? It should
1737 /// probably match the order for assignment, but that is also undecided.
1739 /// **Needs clarification**: Is this typed or not, ie is there a typed load and store involved?
1740 /// I vaguely remember Ralf saying somewhere that he thought it should not be.
1741 CopyNonOverlapping(Box<CopyNonOverlapping<'tcx>>),
1743 /// No-op. Useful for deleting instructions without affecting statement indices.
1747 impl<'tcx> StatementKind<'tcx> {
1748 pub fn as_assign_mut(&mut self) -> Option<&mut (Place<'tcx>, Rvalue<'tcx>)> {
1750 StatementKind::Assign(x) => Some(x),
1755 pub fn as_assign(&self) -> Option<&(Place<'tcx>, Rvalue<'tcx>)> {
1757 StatementKind::Assign(x) => Some(x),
1763 /// Describes what kind of retag is to be performed.
1764 #[derive(Copy, Clone, TyEncodable, TyDecodable, Debug, PartialEq, Eq, Hash, HashStable)]
1765 pub enum RetagKind {
1766 /// The initial retag when entering a function.
1768 /// Retag preparing for a two-phase borrow.
1770 /// Retagging raw pointers.
1772 /// A "normal" retag.
1776 /// The `FakeReadCause` describes the type of pattern why a FakeRead statement exists.
1777 #[derive(Copy, Clone, TyEncodable, TyDecodable, Debug, Hash, HashStable, PartialEq)]
1778 pub enum FakeReadCause {
1779 /// Inject a fake read of the borrowed input at the end of each guards
1782 /// This should ensure that you cannot change the variant for an enum while
1783 /// you are in the midst of matching on it.
1786 /// `let x: !; match x {}` doesn't generate any read of x so we need to
1787 /// generate a read of x to check that it is initialized and safe.
1789 /// If a closure pattern matches a Place starting with an Upvar, then we introduce a
1790 /// FakeRead for that Place outside the closure, in such a case this option would be
1791 /// Some(closure_def_id).
1792 /// Otherwise, the value of the optional DefId will be None.
1793 ForMatchedPlace(Option<DefId>),
1795 /// A fake read of the RefWithinGuard version of a bind-by-value variable
1796 /// in a match guard to ensure that its value hasn't change by the time
1797 /// we create the OutsideGuard version.
1800 /// Officially, the semantics of
1802 /// `let pattern = <expr>;`
1804 /// is that `<expr>` is evaluated into a temporary and then this temporary is
1805 /// into the pattern.
1807 /// However, if we see the simple pattern `let var = <expr>`, we optimize this to
1808 /// evaluate `<expr>` directly into the variable `var`. This is mostly unobservable,
1809 /// but in some cases it can affect the borrow checker, as in #53695.
1810 /// Therefore, we insert a "fake read" here to ensure that we get
1811 /// appropriate errors.
1813 /// If a closure pattern matches a Place starting with an Upvar, then we introduce a
1814 /// FakeRead for that Place outside the closure, in such a case this option would be
1815 /// Some(closure_def_id).
1816 /// Otherwise, the value of the optional DefId will be None.
1817 ForLet(Option<DefId>),
1819 /// If we have an index expression like
1821 /// (*x)[1][{ x = y; 4}]
1823 /// then the first bounds check is invalidated when we evaluate the second
1824 /// index expression. Thus we create a fake borrow of `x` across the second
1825 /// indexer, which will cause a borrow check error.
1829 impl Debug for Statement<'_> {
1830 fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
1831 use self::StatementKind::*;
1833 Assign(box (ref place, ref rv)) => write!(fmt, "{:?} = {:?}", place, rv),
1834 FakeRead(box (ref cause, ref place)) => {
1835 write!(fmt, "FakeRead({:?}, {:?})", cause, place)
1837 Retag(ref kind, ref place) => write!(
1841 RetagKind::FnEntry => "[fn entry] ",
1842 RetagKind::TwoPhase => "[2phase] ",
1843 RetagKind::Raw => "[raw] ",
1844 RetagKind::Default => "",
1848 StorageLive(ref place) => write!(fmt, "StorageLive({:?})", place),
1849 StorageDead(ref place) => write!(fmt, "StorageDead({:?})", place),
1850 SetDiscriminant { ref place, variant_index } => {
1851 write!(fmt, "discriminant({:?}) = {:?}", place, variant_index)
1853 Deinit(ref place) => write!(fmt, "Deinit({:?})", place),
1854 AscribeUserType(box (ref place, ref c_ty), ref variance) => {
1855 write!(fmt, "AscribeUserType({:?}, {:?}, {:?})", place, variance, c_ty)
1857 Coverage(box self::Coverage { ref kind, code_region: Some(ref rgn) }) => {
1858 write!(fmt, "Coverage::{:?} for {:?}", kind, rgn)
1860 Coverage(box ref coverage) => write!(fmt, "Coverage::{:?}", coverage.kind),
1861 CopyNonOverlapping(box crate::mir::CopyNonOverlapping {
1866 write!(fmt, "copy_nonoverlapping(src={:?}, dst={:?}, count={:?})", src, dst, count)
1868 Nop => write!(fmt, "nop"),
1873 #[derive(Clone, Debug, PartialEq, TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable)]
1874 pub struct Coverage {
1875 pub kind: CoverageKind,
1876 pub code_region: Option<CodeRegion>,
1879 #[derive(Clone, Debug, PartialEq, TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable)]
1880 pub struct CopyNonOverlapping<'tcx> {
1881 pub src: Operand<'tcx>,
1882 pub dst: Operand<'tcx>,
1883 /// Number of elements to copy from src to dest, not bytes.
1884 pub count: Operand<'tcx>,
1887 ///////////////////////////////////////////////////////////////////////////
1890 /// Places roughly correspond to a "location in memory." Places in MIR are the same mathematical
1891 /// object as places in Rust. This of course means that what exactly they are is undecided and part
1892 /// of the Rust memory model. However, they will likely contain at least the following pieces of
1893 /// information in some form:
1895 /// 1. The address in memory that the place refers to.
1896 /// 2. The provenance with which the place is being accessed.
1897 /// 3. The type of the place and an optional variant index. See [`PlaceTy`][tcx::PlaceTy].
1898 /// 4. Optionally, some metadata. This exists if and only if the type of the place is not `Sized`.
1900 /// We'll give a description below of how all pieces of the place except for the provenance are
1901 /// calculated. We cannot give a description of the provenance, because that is part of the
1902 /// undecided aliasing model - we only include it here at all to acknowledge its existence.
1904 /// Each local naturally corresponds to the place `Place { local, projection: [] }`. This place has
1905 /// the address of the local's allocation and the type of the local.
1907 /// **Needs clarification:** Unsized locals seem to present a bit of an issue. Their allocation
1908 /// can't actually be created on `StorageLive`, because it's unclear how big to make the allocation.
1909 /// Furthermore, MIR produces assignments to unsized locals, although that is not permitted under
1910 /// `#![feature(unsized_locals)]` in Rust. Besides just putting "unsized locals are special and
1911 /// different" in a bunch of places, I (JakobDegen) don't know how to incorporate this behavior into
1912 /// the current MIR semantics in a clean way - possibly this needs some design work first.
1914 /// For places that are not locals, ie they have a non-empty list of projections, we define the
1915 /// values as a function of the parent place, that is the place with its last [`ProjectionElem`]
1916 /// stripped. The way this is computed of course depends on the kind of that last projection
1919 /// - [`Downcast`](ProjectionElem::Downcast): This projection sets the place's variant index to the
1920 /// given one, and makes no other changes. A `Downcast` projection on a place with its variant
1921 /// index already set is not well-formed.
1922 /// - [`Field`](ProjectionElem::Field): `Field` projections take their parent place and create a
1923 /// place referring to one of the fields of the type. The resulting address is the parent
1924 /// address, plus the offset of the field. The type becomes the type of the field. If the parent
1925 /// was unsized and so had metadata associated with it, then the metadata is retained if the
1926 /// field is unsized and thrown out if it is sized.
1928 /// These projections are only legal for tuples, ADTs, closures, and generators. If the ADT or
1929 /// generator has more than one variant, the parent place's variant index must be set, indicating
1930 /// which variant is being used. If it has just one variant, the variant index may or may not be
1931 /// included - the single possible variant is inferred if it is not included.
1932 /// - [`ConstantIndex`](ProjectionElem::ConstantIndex): Computes an offset in units of `T` into the
1933 /// place as described in the documentation for the `ProjectionElem`. The resulting address is
1934 /// the parent's address plus that offset, and the type is `T`. This is only legal if the parent
1935 /// place has type `[T; N]` or `[T]` (*not* `&[T]`). Since such a `T` is always sized, any
1936 /// resulting metadata is thrown out.
1937 /// - [`Subslice`](ProjectionElem::Subslice): This projection calculates an offset and a new
1938 /// address in a similar manner as `ConstantIndex`. It is also only legal on `[T; N]` and `[T]`.
1939 /// However, this yields a `Place` of type `[T]`, and additionally sets the metadata to be the
1940 /// length of the subslice.
1941 /// - [`Index`](ProjectionElem::Index): Like `ConstantIndex`, only legal on `[T; N]` or `[T]`.
1942 /// However, `Index` additionally takes a local from which the value of the index is computed at
1943 /// runtime. Computing the value of the index involves interpreting the `Local` as a
1944 /// `Place { local, projection: [] }`, and then computing its value as if done via
1945 /// [`Operand::Copy`]. The array/slice is then indexed with the resulting value. The local must
1946 /// have type `usize`.
1947 /// - [`Deref`](ProjectionElem::Deref): Derefs are the last type of projection, and the most
1948 /// complicated. They are only legal on parent places that are references, pointers, or `Box`. A
1949 /// `Deref` projection begins by loading a value from the parent place, as if by
1950 /// [`Operand::Copy`]. It then dereferences the resulting pointer, creating a place of the
1951 /// pointee's type. The resulting address is the address that was stored in the pointer. If the
1952 /// pointee type is unsized, the pointer additionally stored the value of the metadata.
1954 /// Computing a place may cause UB. One possibility is that the pointer used for a `Deref` may not
1955 /// be suitably aligned. Another possibility is that the place is not in bounds, meaning it does not
1956 /// point to an actual allocation.
1958 /// However, if this is actually UB and when the UB kicks in is undecided. This is being discussed
1959 /// in [UCG#319]. The options include that every place must obey those rules, that only some places
1960 /// must obey them, or that places impose no rules of their own.
1962 /// [UCG#319]: https://github.com/rust-lang/unsafe-code-guidelines/issues/319
1964 /// Rust currently requires that every place obey those two rules. This is checked by MIRI and taken
1965 /// advantage of by codegen (via `gep inbounds`). That is possibly subject to change.
1966 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, HashStable)]
1967 pub struct Place<'tcx> {
1970 /// projection out of a place (access a field, deref a pointer, etc)
1971 pub projection: &'tcx List<PlaceElem<'tcx>>,
1974 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
1975 static_assert_size!(Place<'_>, 16);
1977 #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
1978 #[derive(TyEncodable, TyDecodable, HashStable)]
1979 pub enum ProjectionElem<V, T> {
1982 /// Index into a slice/array.
1984 /// Note that this does not also dereference, and so it does not exactly correspond to slice
1985 /// indexing in Rust. In other words, in the below Rust code:
1988 /// let x = &[1, 2, 3, 4];
1993 /// The `x[i]` is turned into a `Deref` followed by an `Index`, not just an `Index`. The same
1994 /// thing is true of the `ConstantIndex` and `Subslice` projections below.
1997 /// These indices are generated by slice patterns. Easiest to explain
2000 /// ```ignore (illustrative)
2001 /// [X, _, .._, _, _] => { offset: 0, min_length: 4, from_end: false },
2002 /// [_, X, .._, _, _] => { offset: 1, min_length: 4, from_end: false },
2003 /// [_, _, .._, X, _] => { offset: 2, min_length: 4, from_end: true },
2004 /// [_, _, .._, _, X] => { offset: 1, min_length: 4, from_end: true },
2007 /// index or -index (in Python terms), depending on from_end
2009 /// The thing being indexed must be at least this long. For arrays this
2010 /// is always the exact length.
2012 /// Counting backwards from end? This is always false when indexing an
2017 /// These indices are generated by slice patterns.
2019 /// If `from_end` is true `slice[from..slice.len() - to]`.
2020 /// Otherwise `array[from..to]`.
2024 /// Whether `to` counts from the start or end of the array/slice.
2025 /// For `PlaceElem`s this is `true` if and only if the base is a slice.
2026 /// For `ProjectionKind`, this can also be `true` for arrays.
2030 /// "Downcast" to a variant of an enum or a generator.
2032 /// The included Symbol is the name of the variant, used for printing MIR.
2033 Downcast(Option<Symbol>, VariantIdx),
2036 impl<V, T> ProjectionElem<V, T> {
2037 /// Returns `true` if the target of this projection may refer to a different region of memory
2039 fn is_indirect(&self) -> bool {
2041 Self::Deref => true,
2045 | Self::ConstantIndex { .. }
2046 | Self::Subslice { .. }
2047 | Self::Downcast(_, _) => false,
2051 /// Returns `true` if this is a `Downcast` projection with the given `VariantIdx`.
2052 pub fn is_downcast_to(&self, v: VariantIdx) -> bool {
2053 matches!(*self, Self::Downcast(_, x) if x == v)
2056 /// Returns `true` if this is a `Field` projection with the given index.
2057 pub fn is_field_to(&self, f: Field) -> bool {
2058 matches!(*self, Self::Field(x, _) if x == f)
2062 /// Alias for projections as they appear in places, where the base is a place
2063 /// and the index is a local.
2064 pub type PlaceElem<'tcx> = ProjectionElem<Local, Ty<'tcx>>;
2066 // This type is fairly frequently used, so we shouldn't unintentionally increase
2068 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
2069 static_assert_size!(PlaceElem<'_>, 24);
2071 /// Alias for projections as they appear in `UserTypeProjection`, where we
2072 /// need neither the `V` parameter for `Index` nor the `T` for `Field`.
2073 pub type ProjectionKind = ProjectionElem<(), ()>;
2075 rustc_index::newtype_index! {
2076 /// A [newtype'd][wrapper] index type in the MIR [control-flow graph][CFG]
2078 /// A field (e.g., `f` in `_1.f`) is one variant of [`ProjectionElem`]. Conceptually,
2079 /// rustc can identify that a field projection refers to either two different regions of memory
2080 /// or the same one between the base and the 'projection element'.
2081 /// Read more about projections in the [rustc-dev-guide][mir-datatypes]
2083 /// [wrapper]: https://rustc-dev-guide.rust-lang.org/appendix/glossary.html#newtype
2084 /// [CFG]: https://rustc-dev-guide.rust-lang.org/appendix/background.html#cfg
2085 /// [mir-datatypes]: https://rustc-dev-guide.rust-lang.org/mir/index.html#mir-data-types
2088 DEBUG_FORMAT = "field[{}]"
2092 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
2093 pub struct PlaceRef<'tcx> {
2095 pub projection: &'tcx [PlaceElem<'tcx>],
2098 // Once we stop implementing `Ord` for `DefId`,
2099 // this impl will be unnecessary. Until then, we'll
2100 // leave this impl in place to prevent re-adding a
2101 // dependnecy on the `Ord` impl for `DefId`
2102 impl<'tcx> !PartialOrd for PlaceRef<'tcx> {}
2104 impl<'tcx> Place<'tcx> {
2105 // FIXME change this to a const fn by also making List::empty a const fn.
2106 pub fn return_place() -> Place<'tcx> {
2107 Place { local: RETURN_PLACE, projection: List::empty() }
2110 /// Returns `true` if this `Place` contains a `Deref` projection.
2112 /// If `Place::is_indirect` returns false, the caller knows that the `Place` refers to the
2113 /// same region of memory as its base.
2114 pub fn is_indirect(&self) -> bool {
2115 self.projection.iter().any(|elem| elem.is_indirect())
2118 /// Finds the innermost `Local` from this `Place`, *if* it is either a local itself or
2119 /// a single deref of a local.
2121 pub fn local_or_deref_local(&self) -> Option<Local> {
2122 self.as_ref().local_or_deref_local()
2125 /// If this place represents a local variable like `_X` with no
2126 /// projections, return `Some(_X)`.
2128 pub fn as_local(&self) -> Option<Local> {
2129 self.as_ref().as_local()
2133 pub fn as_ref(&self) -> PlaceRef<'tcx> {
2134 PlaceRef { local: self.local, projection: &self.projection }
2137 /// Iterate over the projections in evaluation order, i.e., the first element is the base with
2138 /// its projection and then subsequently more projections are added.
2139 /// As a concrete example, given the place a.b.c, this would yield:
2143 /// Given a place without projections, the iterator is empty.
2145 pub fn iter_projections(
2147 ) -> impl Iterator<Item = (PlaceRef<'tcx>, PlaceElem<'tcx>)> + DoubleEndedIterator {
2148 self.projection.iter().enumerate().map(move |(i, proj)| {
2149 let base = PlaceRef { local: self.local, projection: &self.projection[..i] };
2154 /// Generates a new place by appending `more_projections` to the existing ones
2155 /// and interning the result.
2156 pub fn project_deeper(self, more_projections: &[PlaceElem<'tcx>], tcx: TyCtxt<'tcx>) -> Self {
2157 if more_projections.is_empty() {
2161 let mut v: Vec<PlaceElem<'tcx>>;
2163 let new_projections = if self.projection.is_empty() {
2166 v = Vec::with_capacity(self.projection.len() + more_projections.len());
2167 v.extend(self.projection);
2168 v.extend(more_projections);
2172 Place { local: self.local, projection: tcx.intern_place_elems(new_projections) }
2176 impl From<Local> for Place<'_> {
2177 fn from(local: Local) -> Self {
2178 Place { local, projection: List::empty() }
2182 impl<'tcx> PlaceRef<'tcx> {
2183 /// Finds the innermost `Local` from this `Place`, *if* it is either a local itself or
2184 /// a single deref of a local.
2185 pub fn local_or_deref_local(&self) -> Option<Local> {
2187 PlaceRef { local, projection: [] }
2188 | PlaceRef { local, projection: [ProjectionElem::Deref] } => Some(local),
2193 /// If this place represents a local variable like `_X` with no
2194 /// projections, return `Some(_X)`.
2196 pub fn as_local(&self) -> Option<Local> {
2198 PlaceRef { local, projection: [] } => Some(local),
2204 pub fn last_projection(&self) -> Option<(PlaceRef<'tcx>, PlaceElem<'tcx>)> {
2205 if let &[ref proj_base @ .., elem] = self.projection {
2206 Some((PlaceRef { local: self.local, projection: proj_base }, elem))
2213 impl Debug for Place<'_> {
2214 fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
2215 for elem in self.projection.iter().rev() {
2217 ProjectionElem::Downcast(_, _) | ProjectionElem::Field(_, _) => {
2218 write!(fmt, "(").unwrap();
2220 ProjectionElem::Deref => {
2221 write!(fmt, "(*").unwrap();
2223 ProjectionElem::Index(_)
2224 | ProjectionElem::ConstantIndex { .. }
2225 | ProjectionElem::Subslice { .. } => {}
2229 write!(fmt, "{:?}", self.local)?;
2231 for elem in self.projection.iter() {
2233 ProjectionElem::Downcast(Some(name), _index) => {
2234 write!(fmt, " as {})", name)?;
2236 ProjectionElem::Downcast(None, index) => {
2237 write!(fmt, " as variant#{:?})", index)?;
2239 ProjectionElem::Deref => {
2242 ProjectionElem::Field(field, ty) => {
2243 write!(fmt, ".{:?}: {:?})", field.index(), ty)?;
2245 ProjectionElem::Index(ref index) => {
2246 write!(fmt, "[{:?}]", index)?;
2248 ProjectionElem::ConstantIndex { offset, min_length, from_end: false } => {
2249 write!(fmt, "[{:?} of {:?}]", offset, min_length)?;
2251 ProjectionElem::ConstantIndex { offset, min_length, from_end: true } => {
2252 write!(fmt, "[-{:?} of {:?}]", offset, min_length)?;
2254 ProjectionElem::Subslice { from, to, from_end: true } if to == 0 => {
2255 write!(fmt, "[{:?}:]", from)?;
2257 ProjectionElem::Subslice { from, to, from_end: true } if from == 0 => {
2258 write!(fmt, "[:-{:?}]", to)?;
2260 ProjectionElem::Subslice { from, to, from_end: true } => {
2261 write!(fmt, "[{:?}:-{:?}]", from, to)?;
2263 ProjectionElem::Subslice { from, to, from_end: false } => {
2264 write!(fmt, "[{:?}..{:?}]", from, to)?;
2273 ///////////////////////////////////////////////////////////////////////////
2276 rustc_index::newtype_index! {
2277 pub struct SourceScope {
2279 DEBUG_FORMAT = "scope[{}]",
2280 const OUTERMOST_SOURCE_SCOPE = 0,
2285 /// Finds the original HirId this MIR item came from.
2286 /// This is necessary after MIR optimizations, as otherwise we get a HirId
2287 /// from the function that was inlined instead of the function call site.
2288 pub fn lint_root<'tcx>(
2290 source_scopes: &IndexVec<SourceScope, SourceScopeData<'tcx>>,
2291 ) -> Option<HirId> {
2292 let mut data = &source_scopes[self];
2293 // FIXME(oli-obk): we should be able to just walk the `inlined_parent_scope`, but it
2294 // does not work as I thought it would. Needs more investigation and documentation.
2295 while data.inlined.is_some() {
2297 data = &source_scopes[data.parent_scope.unwrap()];
2300 match &data.local_data {
2301 ClearCrossCrate::Set(data) => Some(data.lint_root),
2302 ClearCrossCrate::Clear => None,
2307 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
2308 pub struct SourceScopeData<'tcx> {
2310 pub parent_scope: Option<SourceScope>,
2312 /// Whether this scope is the root of a scope tree of another body,
2313 /// inlined into this body by the MIR inliner.
2314 /// `ty::Instance` is the callee, and the `Span` is the call site.
2315 pub inlined: Option<(ty::Instance<'tcx>, Span)>,
2317 /// Nearest (transitive) parent scope (if any) which is inlined.
2318 /// This is an optimization over walking up `parent_scope`
2319 /// until a scope with `inlined: Some(...)` is found.
2320 pub inlined_parent_scope: Option<SourceScope>,
2322 /// Crate-local information for this source scope, that can't (and
2323 /// needn't) be tracked across crates.
2324 pub local_data: ClearCrossCrate<SourceScopeLocalData>,
2327 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
2328 pub struct SourceScopeLocalData {
2329 /// An `HirId` with lint levels equivalent to this scope's lint levels.
2330 pub lint_root: hir::HirId,
2331 /// The unsafe block that contains this node.
2335 ///////////////////////////////////////////////////////////////////////////
2338 /// An operand in MIR represents a "value" in Rust, the definition of which is undecided and part of
2339 /// the memory model. One proposal for a definition of values can be found [on UCG][value-def].
2341 /// [value-def]: https://github.com/rust-lang/unsafe-code-guidelines/blob/master/wip/value-domain.md
2343 /// The most common way to create values is via loading a place. Loading a place is an operation
2344 /// which reads the memory of the place and converts it to a value. This is a fundamentally *typed*
2345 /// operation. The nature of the value produced depends on the type of the conversion. Furthermore,
2346 /// there may be other effects: if the type has a validity constraint loading the place might be UB
2347 /// if the validity constraint is not met.
2349 /// **Needs clarification:** Ralf proposes that loading a place not have side-effects.
2350 /// This is what is implemented in miri today. Are these the semantics we want for MIR? Is this
2351 /// something we can even decide without knowing more about Rust's memory model?
2353 /// **Needs clarifiation:** Is loading a place that has its variant index set well-formed? Miri
2354 /// currently implements it, but it seems like this may be something to check against in the
2356 #[derive(Clone, PartialEq, TyEncodable, TyDecodable, Hash, HashStable)]
2357 pub enum Operand<'tcx> {
2358 /// Creates a value by loading the given place.
2360 /// Before drop elaboration, the type of the place must be `Copy`. After drop elaboration there
2361 /// is no such requirement.
2364 /// Creates a value by performing loading the place, just like the `Copy` operand.
2366 /// This *may* additionally overwrite the place with `uninit` bytes, depending on how we decide
2367 /// in [UCG#188]. You should not emit MIR that may attempt a subsequent second load of this
2368 /// place without first re-initializing it.
2370 /// [UCG#188]: https://github.com/rust-lang/unsafe-code-guidelines/issues/188
2373 /// Constants are already semantically values, and remain unchanged.
2374 Constant(Box<Constant<'tcx>>),
2377 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
2378 static_assert_size!(Operand<'_>, 24);
2380 impl<'tcx> Debug for Operand<'tcx> {
2381 fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
2382 use self::Operand::*;
2384 Constant(ref a) => write!(fmt, "{:?}", a),
2385 Copy(ref place) => write!(fmt, "{:?}", place),
2386 Move(ref place) => write!(fmt, "move {:?}", place),
2391 impl<'tcx> Operand<'tcx> {
2392 /// Convenience helper to make a constant that refers to the fn
2393 /// with given `DefId` and substs. Since this is used to synthesize
2394 /// MIR, assumes `user_ty` is None.
2395 pub fn function_handle(
2398 substs: SubstsRef<'tcx>,
2401 let ty = tcx.bound_type_of(def_id).subst(tcx, substs);
2402 Operand::Constant(Box::new(Constant {
2405 literal: ConstantKind::Val(ConstValue::zst(), ty),
2409 pub fn is_move(&self) -> bool {
2410 matches!(self, Operand::Move(..))
2413 /// Convenience helper to make a literal-like constant from a given scalar value.
2414 /// Since this is used to synthesize MIR, assumes `user_ty` is None.
2415 pub fn const_from_scalar(
2420 ) -> Operand<'tcx> {
2422 let param_env_and_ty = ty::ParamEnv::empty().and(ty);
2424 .layout_of(param_env_and_ty)
2425 .unwrap_or_else(|e| panic!("could not compute layout for {:?}: {:?}", ty, e))
2427 let scalar_size = match val {
2428 Scalar::Int(int) => int.size(),
2429 _ => panic!("Invalid scalar type {:?}", val),
2431 scalar_size == type_size
2433 Operand::Constant(Box::new(Constant {
2436 literal: ConstantKind::Val(ConstValue::Scalar(val), ty),
2440 pub fn to_copy(&self) -> Self {
2442 Operand::Copy(_) | Operand::Constant(_) => self.clone(),
2443 Operand::Move(place) => Operand::Copy(place),
2447 /// Returns the `Place` that is the target of this `Operand`, or `None` if this `Operand` is a
2449 pub fn place(&self) -> Option<Place<'tcx>> {
2451 Operand::Copy(place) | Operand::Move(place) => Some(*place),
2452 Operand::Constant(_) => None,
2456 /// Returns the `Constant` that is the target of this `Operand`, or `None` if this `Operand` is a
2458 pub fn constant(&self) -> Option<&Constant<'tcx>> {
2460 Operand::Constant(x) => Some(&**x),
2461 Operand::Copy(_) | Operand::Move(_) => None,
2465 /// Gets the `ty::FnDef` from an operand if it's a constant function item.
2467 /// While this is unlikely in general, it's the normal case of what you'll
2468 /// find as the `func` in a [`TerminatorKind::Call`].
2469 pub fn const_fn_def(&self) -> Option<(DefId, SubstsRef<'tcx>)> {
2470 let const_ty = self.constant()?.literal.ty();
2471 if let ty::FnDef(def_id, substs) = *const_ty.kind() { Some((def_id, substs)) } else { None }
2475 ///////////////////////////////////////////////////////////////////////////
2478 #[derive(Clone, TyEncodable, TyDecodable, Hash, HashStable, PartialEq)]
2479 /// The various kinds of rvalues that can appear in MIR.
2481 /// Not all of these are allowed at every [`MirPhase`] - when this is the case, it's stated below.
2483 /// Computing any rvalue begins by evaluating the places and operands in some order (**Needs
2484 /// clarification**: Which order?). These are then used to produce a "value" - the same kind of
2485 /// value that an [`Operand`] produces.
2486 pub enum Rvalue<'tcx> {
2487 /// Yields the operand unchanged
2490 /// Creates an array where each element is the value of the operand.
2492 /// This is the cause of a bug in the case where the repetition count is zero because the value
2493 /// is not dropped, see [#74836].
2495 /// Corresponds to source code like `[x; 32]`.
2497 /// [#74836]: https://github.com/rust-lang/rust/issues/74836
2498 Repeat(Operand<'tcx>, ty::Const<'tcx>),
2500 /// Creates a reference of the indicated kind to the place.
2502 /// There is not much to document here, because besides the obvious parts the semantics of this
2503 /// are essentially entirely a part of the aliasing model. There are many UCG issues discussing
2504 /// exactly what the behavior of this operation should be.
2506 /// `Shallow` borrows are disallowed after drop lowering.
2507 Ref(Region<'tcx>, BorrowKind, Place<'tcx>),
2509 /// Creates a pointer/reference to the given thread local.
2511 /// The yielded type is a `*mut T` if the static is mutable, otherwise if the static is extern a
2512 /// `*const T`, and if neither of those apply a `&T`.
2514 /// **Note:** This is a runtime operation that actually executes code and is in this sense more
2515 /// like a function call. Also, eliminating dead stores of this rvalue causes `fn main() {}` to
2516 /// SIGILL for some reason that I (JakobDegen) never got a chance to look into.
2518 /// **Needs clarification**: Are there weird additional semantics here related to the runtime
2519 /// nature of this operation?
2520 ThreadLocalRef(DefId),
2522 /// Creates a pointer with the indicated mutability to the place.
2524 /// This is generated by pointer casts like `&v as *const _` or raw address of expressions like
2525 /// `&raw v` or `addr_of!(v)`.
2527 /// Like with references, the semantics of this operation are heavily dependent on the aliasing
2529 AddressOf(Mutability, Place<'tcx>),
2531 /// Yields the length of the place, as a `usize`.
2533 /// If the type of the place is an array, this is the array length. For slices (`[T]`, not
2534 /// `&[T]`) this accesses the place's metadata to determine the length. This rvalue is
2535 /// ill-formed for places of other types.
2538 /// Performs essentially all of the casts that can be performed via `as`.
2540 /// This allows for casts from/to a variety of types.
2542 /// **FIXME**: Document exactly which `CastKind`s allow which types of casts. Figure out why
2543 /// `ArrayToPointer` and `MutToConstPointer` are special.
2544 Cast(CastKind, Operand<'tcx>, Ty<'tcx>),
2546 /// * `Offset` has the same semantics as [`offset`](pointer::offset), except that the second
2547 /// parameter may be a `usize` as well.
2548 /// * The comparison operations accept `bool`s, `char`s, signed or unsigned integers, floats,
2549 /// raw pointers, or function pointers and return a `bool`. The types of the operands must be
2550 /// matching, up to the usual caveat of the lifetimes in function pointers.
2551 /// * Left and right shift operations accept signed or unsigned integers not necessarily of the
2552 /// same type and return a value of the same type as their LHS. Like in Rust, the RHS is
2553 /// truncated as needed.
2554 /// * The `Bit*` operations accept signed integers, unsigned integers, or bools with matching
2555 /// types and return a value of that type.
2556 /// * The remaining operations accept signed integers, unsigned integers, or floats with
2557 /// matching types and return a value of that type.
2558 BinaryOp(BinOp, Box<(Operand<'tcx>, Operand<'tcx>)>),
2560 /// Same as `BinaryOp`, but yields `(T, bool)` instead of `T`. In addition to performing the
2561 /// same computation as the matching `BinaryOp`, checks if the infinite precison result would be
2562 /// unequal to the actual result and sets the `bool` if this is the case.
2564 /// This only supports addition, subtraction, multiplication, and shift operations on integers.
2565 CheckedBinaryOp(BinOp, Box<(Operand<'tcx>, Operand<'tcx>)>),
2567 /// Computes a value as described by the operation.
2568 NullaryOp(NullOp, Ty<'tcx>),
2570 /// Exactly like `BinaryOp`, but less operands.
2572 /// Also does two's-complement arithmetic. Negation requires a signed integer or a float;
2573 /// bitwise not requires a signed integer, unsigned integer, or bool. Both operation kinds
2574 /// return a value with the same type as their operand.
2575 UnaryOp(UnOp, Operand<'tcx>),
2577 /// Computes the discriminant of the place, returning it as an integer of type
2578 /// [`discriminant_ty`]. Returns zero for types without discriminant.
2580 /// The validity requirements for the underlying value are undecided for this rvalue, see
2581 /// [#91095]. Note too that the value of the discriminant is not the same thing as the
2582 /// variant index; use [`discriminant_for_variant`] to convert.
2584 /// [`discriminant_ty`]: crate::ty::Ty::discriminant_ty
2585 /// [#91095]: https://github.com/rust-lang/rust/issues/91095
2586 /// [`discriminant_for_variant`]: crate::ty::Ty::discriminant_for_variant
2587 Discriminant(Place<'tcx>),
2589 /// Creates an aggregate value, like a tuple or struct.
2591 /// This is needed because dataflow analysis needs to distinguish
2592 /// `dest = Foo { x: ..., y: ... }` from `dest.x = ...; dest.y = ...;` in the case that `Foo`
2593 /// has a destructor.
2595 /// Disallowed after deaggregation for all aggregate kinds except `Array` and `Generator`. After
2596 /// generator lowering, `Generator` aggregate kinds are disallowed too.
2597 Aggregate(Box<AggregateKind<'tcx>>, Vec<Operand<'tcx>>),
2599 /// Transmutes a `*mut u8` into shallow-initialized `Box<T>`.
2601 /// This is different from a normal transmute because dataflow analysis will treat the box as
2602 /// initialized but its content as uninitialized. Like other pointer casts, this in general
2603 /// affects alias analysis.
2604 ShallowInitBox(Operand<'tcx>, Ty<'tcx>),
2607 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
2608 static_assert_size!(Rvalue<'_>, 40);
2610 impl<'tcx> Rvalue<'tcx> {
2611 /// Returns true if rvalue can be safely removed when the result is unused.
2613 pub fn is_safe_to_remove(&self) -> bool {
2615 // Pointer to int casts may be side-effects due to exposing the provenance.
2616 // While the model is undecided, we should be conservative. See
2617 // <https://www.ralfj.de/blog/2022/04/11/provenance-exposed.html>
2618 Rvalue::Cast(CastKind::PointerExposeAddress, _, _) => false,
2621 | Rvalue::Repeat(_, _)
2622 | Rvalue::Ref(_, _, _)
2623 | Rvalue::ThreadLocalRef(_)
2624 | Rvalue::AddressOf(_, _)
2627 CastKind::Misc | CastKind::Pointer(_) | CastKind::PointerFromExposedAddress,
2631 | Rvalue::BinaryOp(_, _)
2632 | Rvalue::CheckedBinaryOp(_, _)
2633 | Rvalue::NullaryOp(_, _)
2634 | Rvalue::UnaryOp(_, _)
2635 | Rvalue::Discriminant(_)
2636 | Rvalue::Aggregate(_, _)
2637 | Rvalue::ShallowInitBox(_, _) => true,
2642 #[derive(Clone, Copy, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
2644 /// An exposing pointer to address cast. A cast between a pointer and an integer type, or
2645 /// between a function pointer and an integer type.
2646 /// See the docs on `expose_addr` for more details.
2647 PointerExposeAddress,
2648 /// An address-to-pointer cast that picks up an exposed provenance.
2649 /// See the docs on `from_exposed_addr` for more details.
2650 PointerFromExposedAddress,
2651 /// All sorts of pointer-to-pointer casts. Note that reference-to-raw-ptr casts are
2652 /// translated into `&raw mut/const *r`, i.e., they are not actually casts.
2653 Pointer(PointerCast),
2654 /// Remaining unclassified casts.
2658 #[derive(Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
2659 pub enum AggregateKind<'tcx> {
2660 /// The type is of the element
2664 /// The second field is the variant index. It's equal to 0 for struct
2665 /// and union expressions. The fourth field is
2666 /// active field number and is present only for union expressions
2667 /// -- e.g., for a union expression `SomeUnion { c: .. }`, the
2668 /// active field index would identity the field `c`
2669 Adt(DefId, VariantIdx, SubstsRef<'tcx>, Option<UserTypeAnnotationIndex>, Option<usize>),
2671 Closure(DefId, SubstsRef<'tcx>),
2672 Generator(DefId, SubstsRef<'tcx>, hir::Movability),
2675 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
2676 static_assert_size!(AggregateKind<'_>, 48);
2678 #[derive(Copy, Clone, Debug, PartialEq, PartialOrd, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
2680 /// The `+` operator (addition)
2682 /// The `-` operator (subtraction)
2684 /// The `*` operator (multiplication)
2686 /// The `/` operator (division)
2688 /// Division by zero is UB, because the compiler should have inserted checks
2691 /// The `%` operator (modulus)
2693 /// Using zero as the modulus (second operand) is UB, because the compiler
2694 /// should have inserted checks prior to this.
2696 /// The `^` operator (bitwise xor)
2698 /// The `&` operator (bitwise and)
2700 /// The `|` operator (bitwise or)
2702 /// The `<<` operator (shift left)
2704 /// The offset is truncated to the size of the first operand before shifting.
2706 /// The `>>` operator (shift right)
2708 /// The offset is truncated to the size of the first operand before shifting.
2710 /// The `==` operator (equality)
2712 /// The `<` operator (less than)
2714 /// The `<=` operator (less than or equal to)
2716 /// The `!=` operator (not equal to)
2718 /// The `>=` operator (greater than or equal to)
2720 /// The `>` operator (greater than)
2722 /// The `ptr.offset` operator
2727 pub fn is_checkable(self) -> bool {
2729 matches!(self, Add | Sub | Mul | Shl | Shr)
2733 #[derive(Copy, Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
2735 /// Returns the size of a value of that type
2737 /// Returns the minimum alignment of a type
2741 #[derive(Copy, Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
2743 /// The `!` operator for logical inversion
2745 /// The `-` operator for negation
2749 impl<'tcx> Debug for Rvalue<'tcx> {
2750 fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
2751 use self::Rvalue::*;
2754 Use(ref place) => write!(fmt, "{:?}", place),
2755 Repeat(ref a, b) => {
2756 write!(fmt, "[{:?}; ", a)?;
2757 pretty_print_const(b, fmt, false)?;
2760 Len(ref a) => write!(fmt, "Len({:?})", a),
2761 Cast(ref kind, ref place, ref ty) => {
2762 write!(fmt, "{:?} as {:?} ({:?})", place, ty, kind)
2764 BinaryOp(ref op, box (ref a, ref b)) => write!(fmt, "{:?}({:?}, {:?})", op, a, b),
2765 CheckedBinaryOp(ref op, box (ref a, ref b)) => {
2766 write!(fmt, "Checked{:?}({:?}, {:?})", op, a, b)
2768 UnaryOp(ref op, ref a) => write!(fmt, "{:?}({:?})", op, a),
2769 Discriminant(ref place) => write!(fmt, "discriminant({:?})", place),
2770 NullaryOp(ref op, ref t) => write!(fmt, "{:?}({:?})", op, t),
2771 ThreadLocalRef(did) => ty::tls::with(|tcx| {
2772 let muta = tcx.static_mutability(did).unwrap().prefix_str();
2773 write!(fmt, "&/*tls*/ {}{}", muta, tcx.def_path_str(did))
2775 Ref(region, borrow_kind, ref place) => {
2776 let kind_str = match borrow_kind {
2777 BorrowKind::Shared => "",
2778 BorrowKind::Shallow => "shallow ",
2779 BorrowKind::Mut { .. } | BorrowKind::Unique => "mut ",
2782 // When printing regions, add trailing space if necessary.
2783 let print_region = ty::tls::with(|tcx| {
2784 tcx.sess.verbose() || tcx.sess.opts.debugging_opts.identify_regions
2786 let region = if print_region {
2787 let mut region = region.to_string();
2788 if !region.is_empty() {
2793 // Do not even print 'static
2796 write!(fmt, "&{}{}{:?}", region, kind_str, place)
2799 AddressOf(mutability, ref place) => {
2800 let kind_str = match mutability {
2801 Mutability::Mut => "mut",
2802 Mutability::Not => "const",
2805 write!(fmt, "&raw {} {:?}", kind_str, place)
2808 Aggregate(ref kind, ref places) => {
2809 let fmt_tuple = |fmt: &mut Formatter<'_>, name: &str| {
2810 let mut tuple_fmt = fmt.debug_tuple(name);
2811 for place in places {
2812 tuple_fmt.field(place);
2818 AggregateKind::Array(_) => write!(fmt, "{:?}", places),
2820 AggregateKind::Tuple => {
2821 if places.is_empty() {
2828 AggregateKind::Adt(adt_did, variant, substs, _user_ty, _) => {
2829 ty::tls::with(|tcx| {
2830 let variant_def = &tcx.adt_def(adt_did).variant(variant);
2831 let substs = tcx.lift(substs).expect("could not lift for printing");
2832 let name = FmtPrinter::new(tcx, Namespace::ValueNS)
2833 .print_def_path(variant_def.def_id, substs)?
2836 match variant_def.ctor_kind {
2837 CtorKind::Const => fmt.write_str(&name),
2838 CtorKind::Fn => fmt_tuple(fmt, &name),
2839 CtorKind::Fictive => {
2840 let mut struct_fmt = fmt.debug_struct(&name);
2841 for (field, place) in iter::zip(&variant_def.fields, places) {
2842 struct_fmt.field(field.name.as_str(), place);
2850 AggregateKind::Closure(def_id, substs) => ty::tls::with(|tcx| {
2851 if let Some(def_id) = def_id.as_local() {
2852 let name = if tcx.sess.opts.debugging_opts.span_free_formats {
2853 let substs = tcx.lift(substs).unwrap();
2856 tcx.def_path_str_with_substs(def_id.to_def_id(), substs),
2859 let span = tcx.def_span(def_id);
2862 tcx.sess.source_map().span_to_diagnostic_string(span)
2865 let mut struct_fmt = fmt.debug_struct(&name);
2867 // FIXME(project-rfc-2229#48): This should be a list of capture names/places
2868 if let Some(upvars) = tcx.upvars_mentioned(def_id) {
2869 for (&var_id, place) in iter::zip(upvars.keys(), places) {
2870 let var_name = tcx.hir().name(var_id);
2871 struct_fmt.field(var_name.as_str(), place);
2877 write!(fmt, "[closure]")
2881 AggregateKind::Generator(def_id, _, _) => ty::tls::with(|tcx| {
2882 if let Some(def_id) = def_id.as_local() {
2883 let name = format!("[generator@{:?}]", tcx.def_span(def_id));
2884 let mut struct_fmt = fmt.debug_struct(&name);
2886 // FIXME(project-rfc-2229#48): This should be a list of capture names/places
2887 if let Some(upvars) = tcx.upvars_mentioned(def_id) {
2888 for (&var_id, place) in iter::zip(upvars.keys(), places) {
2889 let var_name = tcx.hir().name(var_id);
2890 struct_fmt.field(var_name.as_str(), place);
2896 write!(fmt, "[generator]")
2902 ShallowInitBox(ref place, ref ty) => {
2903 write!(fmt, "ShallowInitBox({:?}, {:?})", place, ty)
2909 ///////////////////////////////////////////////////////////////////////////
2912 /// Two constants are equal if they are the same constant. Note that
2913 /// this does not necessarily mean that they are `==` in Rust. In
2914 /// particular, one must be wary of `NaN`!
2916 #[derive(Clone, Copy, PartialEq, TyEncodable, TyDecodable, Hash, HashStable)]
2917 pub struct Constant<'tcx> {
2920 /// Optional user-given type: for something like
2921 /// `collect::<Vec<_>>`, this would be present and would
2922 /// indicate that `Vec<_>` was explicitly specified.
2924 /// Needed for NLL to impose user-given type constraints.
2925 pub user_ty: Option<UserTypeAnnotationIndex>,
2927 pub literal: ConstantKind<'tcx>,
2930 #[derive(Clone, Copy, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable, Debug)]
2932 pub enum ConstantKind<'tcx> {
2933 /// This constant came from the type system
2934 Ty(ty::Const<'tcx>),
2935 /// This constant cannot go back into the type system, as it represents
2936 /// something the type system cannot handle (e.g. pointers).
2937 Val(interpret::ConstValue<'tcx>, Ty<'tcx>),
2940 impl<'tcx> Constant<'tcx> {
2941 pub fn check_static_ptr(&self, tcx: TyCtxt<'_>) -> Option<DefId> {
2942 match self.literal.try_to_scalar() {
2943 Some(Scalar::Ptr(ptr, _size)) => match tcx.global_alloc(ptr.provenance) {
2944 GlobalAlloc::Static(def_id) => {
2945 assert!(!tcx.is_thread_local_static(def_id));
2954 pub fn ty(&self) -> Ty<'tcx> {
2959 impl<'tcx> ConstantKind<'tcx> {
2960 /// Returns `None` if the constant is not trivially safe for use in the type system.
2962 pub fn const_for_ty(&self) -> Option<ty::Const<'tcx>> {
2964 ConstantKind::Ty(c) => Some(*c),
2965 ConstantKind::Val(..) => None,
2970 pub fn ty(&self) -> Ty<'tcx> {
2972 ConstantKind::Ty(c) => c.ty(),
2973 ConstantKind::Val(_, ty) => *ty,
2978 pub fn try_to_value(self, tcx: TyCtxt<'tcx>) -> Option<interpret::ConstValue<'tcx>> {
2980 ConstantKind::Ty(c) => match c.kind() {
2981 ty::ConstKind::Value(valtree) => Some(tcx.valtree_to_const_val((c.ty(), valtree))),
2984 ConstantKind::Val(val, _) => Some(val),
2989 pub fn try_to_scalar(self) -> Option<Scalar> {
2991 ConstantKind::Ty(c) => match c.kind() {
2992 ty::ConstKind::Value(valtree) => match valtree {
2993 ty::ValTree::Leaf(scalar_int) => Some(Scalar::Int(scalar_int)),
2994 ty::ValTree::Branch(_) => None,
2998 ConstantKind::Val(val, _) => val.try_to_scalar(),
3003 pub fn try_to_scalar_int(self) -> Option<ScalarInt> {
3004 Some(self.try_to_scalar()?.assert_int())
3008 pub fn try_to_bits(self, size: Size) -> Option<u128> {
3009 self.try_to_scalar_int()?.to_bits(size).ok()
3013 pub fn try_to_bool(self) -> Option<bool> {
3014 self.try_to_scalar_int()?.try_into().ok()
3018 pub fn eval(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Self {
3021 if let Some(val) = c.kind().try_eval_for_mir(tcx, param_env) {
3023 Ok(val) => Self::Val(val, c.ty()),
3024 Err(_) => Self::Ty(tcx.const_error(self.ty())),
3030 Self::Val(_, _) => self,
3034 /// Panics if the value cannot be evaluated or doesn't contain a valid integer of the given type.
3036 pub fn eval_bits(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>, ty: Ty<'tcx>) -> u128 {
3037 self.try_eval_bits(tcx, param_env, ty)
3038 .unwrap_or_else(|| bug!("expected bits of {:#?}, got {:#?}", ty, self))
3042 pub fn try_eval_bits(
3045 param_env: ty::ParamEnv<'tcx>,
3049 Self::Ty(ct) => ct.try_eval_bits(tcx, param_env, ty),
3050 Self::Val(val, t) => {
3053 tcx.layout_of(param_env.with_reveal_all_normalized(tcx).and(ty)).ok()?.size;
3054 val.try_to_bits(size)
3060 pub fn try_eval_bool(&self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Option<bool> {
3062 Self::Ty(ct) => ct.try_eval_bool(tcx, param_env),
3063 Self::Val(val, _) => val.try_to_bool(),
3068 pub fn try_eval_usize(&self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Option<u64> {
3070 Self::Ty(ct) => ct.try_eval_usize(tcx, param_env),
3071 Self::Val(val, _) => val.try_to_machine_usize(tcx),
3076 pub fn from_value(val: ConstValue<'tcx>, ty: Ty<'tcx>) -> Self {
3083 param_env_ty: ty::ParamEnvAnd<'tcx, Ty<'tcx>>,
3086 .layout_of(param_env_ty)
3087 .unwrap_or_else(|e| {
3088 bug!("could not compute layout for {:?}: {:?}", param_env_ty.value, e)
3091 let cv = ConstValue::Scalar(Scalar::from_uint(bits, size));
3093 Self::Val(cv, param_env_ty.value)
3097 pub fn from_bool(tcx: TyCtxt<'tcx>, v: bool) -> Self {
3098 let cv = ConstValue::from_bool(v);
3099 Self::Val(cv, tcx.types.bool)
3103 pub fn zero_sized(ty: Ty<'tcx>) -> Self {
3104 let cv = ConstValue::Scalar(Scalar::ZST);
3108 pub fn from_usize(tcx: TyCtxt<'tcx>, n: u64) -> Self {
3109 let ty = tcx.types.usize;
3110 Self::from_bits(tcx, n as u128, ty::ParamEnv::empty().and(ty))
3114 pub fn from_scalar(_tcx: TyCtxt<'tcx>, s: Scalar, ty: Ty<'tcx>) -> Self {
3115 let val = ConstValue::Scalar(s);
3119 /// Literals are converted to `ConstantKindVal`, const generic parameters are eagerly
3120 /// converted to a constant, everything else becomes `Unevaluated`.
3121 pub fn from_anon_const(
3124 param_env: ty::ParamEnv<'tcx>,
3126 Self::from_opt_const_arg_anon_const(tcx, ty::WithOptConstParam::unknown(def_id), param_env)
3129 #[instrument(skip(tcx), level = "debug")]
3130 pub fn from_inline_const(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> Self {
3131 let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
3132 let body_id = match tcx.hir().get(hir_id) {
3133 hir::Node::AnonConst(ac) => ac.body,
3135 tcx.def_span(def_id.to_def_id()),
3136 "from_inline_const can only process anonymous constants"
3139 let expr = &tcx.hir().body(body_id).value;
3140 let ty = tcx.typeck(def_id).node_type(hir_id);
3142 let lit_input = match expr.kind {
3143 hir::ExprKind::Lit(ref lit) => Some(LitToConstInput { lit: &lit.node, ty, neg: false }),
3144 hir::ExprKind::Unary(hir::UnOp::Neg, ref expr) => match expr.kind {
3145 hir::ExprKind::Lit(ref lit) => {
3146 Some(LitToConstInput { lit: &lit.node, ty, neg: true })
3152 if let Some(lit_input) = lit_input {
3153 // If an error occurred, ignore that it's a literal and leave reporting the error up to
3155 match tcx.at(expr.span).lit_to_mir_constant(lit_input) {
3161 let typeck_root_def_id = tcx.typeck_root_def_id(def_id.to_def_id());
3163 tcx.erase_regions(InternalSubsts::identity_for_item(tcx, typeck_root_def_id));
3165 ty::InlineConstSubsts::new(tcx, ty::InlineConstSubstsParts { parent_substs, ty })
3167 let uneval_const = tcx.mk_const(ty::ConstS {
3168 kind: ty::ConstKind::Unevaluated(ty::Unevaluated {
3169 def: ty::WithOptConstParam::unknown(def_id).to_global(),
3175 debug!(?uneval_const);
3176 debug_assert!(!uneval_const.has_free_regions());
3178 Self::Ty(uneval_const)
3181 #[instrument(skip(tcx), level = "debug")]
3182 fn from_opt_const_arg_anon_const(
3184 def: ty::WithOptConstParam<LocalDefId>,
3185 param_env: ty::ParamEnv<'tcx>,
3187 let body_id = match tcx.hir().get_by_def_id(def.did) {
3188 hir::Node::AnonConst(ac) => ac.body,
3190 tcx.def_span(def.did.to_def_id()),
3191 "from_anon_const can only process anonymous constants"
3195 let expr = &tcx.hir().body(body_id).value;
3198 // Unwrap a block, so that e.g. `{ P }` is recognised as a parameter. Const arguments
3199 // currently have to be wrapped in curly brackets, so it's necessary to special-case.
3200 let expr = match &expr.kind {
3201 hir::ExprKind::Block(block, _) if block.stmts.is_empty() && block.expr.is_some() => {
3202 block.expr.as_ref().unwrap()
3206 debug!("expr.kind: {:?}", expr.kind);
3208 let ty = tcx.type_of(def.def_id_for_type_of());
3211 // FIXME(const_generics): We currently have to special case parameters because `min_const_generics`
3212 // does not provide the parents generics to anonymous constants. We still allow generic const
3213 // parameters by themselves however, e.g. `N`. These constants would cause an ICE if we were to
3214 // ever try to substitute the generic parameters in their bodies.
3216 // While this doesn't happen as these constants are always used as `ty::ConstKind::Param`, it does
3217 // cause issues if we were to remove that special-case and try to evaluate the constant instead.
3218 use hir::{def::DefKind::ConstParam, def::Res, ExprKind, Path, QPath};
3220 ExprKind::Path(QPath::Resolved(_, &Path { res: Res::Def(ConstParam, def_id), .. })) => {
3221 // Find the name and index of the const parameter by indexing the generics of
3222 // the parent item and construct a `ParamConst`.
3223 let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
3224 let item_id = tcx.hir().get_parent_node(hir_id);
3225 let item_def_id = tcx.hir().local_def_id(item_id);
3226 let generics = tcx.generics_of(item_def_id.to_def_id());
3227 let index = generics.param_def_id_to_index[&def_id];
3228 let name = tcx.hir().name(hir_id);
3229 let ty_const = tcx.mk_const(ty::ConstS {
3230 kind: ty::ConstKind::Param(ty::ParamConst::new(index, name)),
3235 return Self::Ty(ty_const);
3240 let hir_id = tcx.hir().local_def_id_to_hir_id(def.did);
3241 let parent_substs = if let Some(parent_hir_id) = tcx.hir().find_parent_node(hir_id) {
3242 if let Some(parent_did) = tcx.hir().opt_local_def_id(parent_hir_id) {
3243 InternalSubsts::identity_for_item(tcx, parent_did.to_def_id())
3245 tcx.mk_substs(Vec::<GenericArg<'tcx>>::new().into_iter())
3248 tcx.mk_substs(Vec::<GenericArg<'tcx>>::new().into_iter())
3250 debug!(?parent_substs);
3252 let did = def.did.to_def_id();
3253 let child_substs = InternalSubsts::identity_for_item(tcx, did);
3254 let substs = tcx.mk_substs(parent_substs.into_iter().chain(child_substs.into_iter()));
3257 let hir_id = tcx.hir().local_def_id_to_hir_id(def.did);
3258 let span = tcx.hir().span(hir_id);
3259 let uneval = ty::Unevaluated::new(def.to_global(), substs);
3260 debug!(?span, ?param_env);
3262 match tcx.const_eval_resolve(param_env, uneval, Some(span)) {
3264 debug!("evaluated const value: {:?}", val);
3268 debug!("error encountered during evaluation");
3269 // Error was handled in `const_eval_resolve`. Here we just create a
3270 // new unevaluated const and error hard later in codegen
3271 let ty_const = tcx.mk_const(ty::ConstS {
3272 kind: ty::ConstKind::Unevaluated(ty::Unevaluated {
3273 def: def.to_global(),
3274 substs: InternalSubsts::identity_for_item(tcx, def.did.to_def_id()),
3286 pub fn from_const(c: ty::Const<'tcx>, tcx: TyCtxt<'tcx>) -> Self {
3288 ty::ConstKind::Value(valtree) => {
3289 let const_val = tcx.valtree_to_const_val((c.ty(), valtree));
3290 Self::Val(const_val, c.ty())
3297 /// A collection of projections into user types.
3299 /// They are projections because a binding can occur a part of a
3300 /// parent pattern that has been ascribed a type.
3302 /// Its a collection because there can be multiple type ascriptions on
3303 /// the path from the root of the pattern down to the binding itself.
3307 /// ```ignore (illustrative)
3308 /// struct S<'a>((i32, &'a str), String);
3309 /// let S((_, w): (i32, &'static str), _): S = ...;
3310 /// // ------ ^^^^^^^^^^^^^^^^^^^ (1)
3311 /// // --------------------------------- ^ (2)
3314 /// The highlights labelled `(1)` show the subpattern `(_, w)` being
3315 /// ascribed the type `(i32, &'static str)`.
3317 /// The highlights labelled `(2)` show the whole pattern being
3318 /// ascribed the type `S`.
3320 /// In this example, when we descend to `w`, we will have built up the
3321 /// following two projected types:
3323 /// * base: `S`, projection: `(base.0).1`
3324 /// * base: `(i32, &'static str)`, projection: `base.1`
3326 /// The first will lead to the constraint `w: &'1 str` (for some
3327 /// inferred region `'1`). The second will lead to the constraint `w:
3329 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
3330 pub struct UserTypeProjections {
3331 pub contents: Vec<(UserTypeProjection, Span)>,
3334 impl<'tcx> UserTypeProjections {
3335 pub fn none() -> Self {
3336 UserTypeProjections { contents: vec![] }
3339 pub fn is_empty(&self) -> bool {
3340 self.contents.is_empty()
3343 pub fn projections_and_spans(
3345 ) -> impl Iterator<Item = &(UserTypeProjection, Span)> + ExactSizeIterator {
3346 self.contents.iter()
3349 pub fn projections(&self) -> impl Iterator<Item = &UserTypeProjection> + ExactSizeIterator {
3350 self.contents.iter().map(|&(ref user_type, _span)| user_type)
3353 pub fn push_projection(mut self, user_ty: &UserTypeProjection, span: Span) -> Self {
3354 self.contents.push((user_ty.clone(), span));
3360 mut f: impl FnMut(UserTypeProjection) -> UserTypeProjection,
3362 self.contents = self.contents.into_iter().map(|(proj, span)| (f(proj), span)).collect();
3366 pub fn index(self) -> Self {
3367 self.map_projections(|pat_ty_proj| pat_ty_proj.index())
3370 pub fn subslice(self, from: u64, to: u64) -> Self {
3371 self.map_projections(|pat_ty_proj| pat_ty_proj.subslice(from, to))
3374 pub fn deref(self) -> Self {
3375 self.map_projections(|pat_ty_proj| pat_ty_proj.deref())
3378 pub fn leaf(self, field: Field) -> Self {
3379 self.map_projections(|pat_ty_proj| pat_ty_proj.leaf(field))
3382 pub fn variant(self, adt_def: AdtDef<'tcx>, variant_index: VariantIdx, field: Field) -> Self {
3383 self.map_projections(|pat_ty_proj| pat_ty_proj.variant(adt_def, variant_index, field))
3387 /// Encodes the effect of a user-supplied type annotation on the
3388 /// subcomponents of a pattern. The effect is determined by applying the
3389 /// given list of projections to some underlying base type. Often,
3390 /// the projection element list `projs` is empty, in which case this
3391 /// directly encodes a type in `base`. But in the case of complex patterns with
3392 /// subpatterns and bindings, we want to apply only a *part* of the type to a variable,
3393 /// in which case the `projs` vector is used.
3397 /// * `let x: T = ...` -- here, the `projs` vector is empty.
3399 /// * `let (x, _): T = ...` -- here, the `projs` vector would contain
3400 /// `field[0]` (aka `.0`), indicating that the type of `s` is
3401 /// determined by finding the type of the `.0` field from `T`.
3402 #[derive(Clone, Debug, TyEncodable, TyDecodable, Hash, HashStable, PartialEq)]
3403 pub struct UserTypeProjection {
3404 pub base: UserTypeAnnotationIndex,
3405 pub projs: Vec<ProjectionKind>,
3408 impl Copy for ProjectionKind {}
3410 impl UserTypeProjection {
3411 pub(crate) fn index(mut self) -> Self {
3412 self.projs.push(ProjectionElem::Index(()));
3416 pub(crate) fn subslice(mut self, from: u64, to: u64) -> Self {
3417 self.projs.push(ProjectionElem::Subslice { from, to, from_end: true });
3421 pub(crate) fn deref(mut self) -> Self {
3422 self.projs.push(ProjectionElem::Deref);
3426 pub(crate) fn leaf(mut self, field: Field) -> Self {
3427 self.projs.push(ProjectionElem::Field(field, ()));
3431 pub(crate) fn variant(
3433 adt_def: AdtDef<'_>,
3434 variant_index: VariantIdx,
3437 self.projs.push(ProjectionElem::Downcast(
3438 Some(adt_def.variant(variant_index).name),
3441 self.projs.push(ProjectionElem::Field(field, ()));
3446 TrivialTypeFoldableAndLiftImpls! { ProjectionKind, }
3448 impl<'tcx> TypeFoldable<'tcx> for UserTypeProjection {
3449 fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
3450 Ok(UserTypeProjection {
3451 base: self.base.try_fold_with(folder)?,
3452 projs: self.projs.try_fold_with(folder)?,
3456 fn visit_with<Vs: TypeVisitor<'tcx>>(&self, visitor: &mut Vs) -> ControlFlow<Vs::BreakTy> {
3457 self.base.visit_with(visitor)
3458 // Note: there's nothing in `self.proj` to visit.
3462 rustc_index::newtype_index! {
3463 pub struct Promoted {
3465 DEBUG_FORMAT = "promoted[{}]"
3469 impl<'tcx> Debug for Constant<'tcx> {
3470 fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
3471 write!(fmt, "{}", self)
3475 impl<'tcx> Display for Constant<'tcx> {
3476 fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
3477 match self.ty().kind() {
3479 _ => write!(fmt, "const ")?,
3481 Display::fmt(&self.literal, fmt)
3485 impl<'tcx> Display for ConstantKind<'tcx> {
3486 fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
3488 ConstantKind::Ty(c) => pretty_print_const(c, fmt, true),
3489 ConstantKind::Val(val, ty) => pretty_print_const_value(val, ty, fmt, true),
3494 fn pretty_print_const<'tcx>(
3496 fmt: &mut Formatter<'_>,
3499 use crate::ty::print::PrettyPrinter;
3500 ty::tls::with(|tcx| {
3501 let literal = tcx.lift(c).unwrap();
3502 let mut cx = FmtPrinter::new(tcx, Namespace::ValueNS);
3503 cx.print_alloc_ids = true;
3504 let cx = cx.pretty_print_const(literal, print_types)?;
3505 fmt.write_str(&cx.into_buffer())?;
3510 fn pretty_print_byte_str(fmt: &mut Formatter<'_>, byte_str: &[u8]) -> fmt::Result {
3511 fmt.write_str("b\"")?;
3512 for &c in byte_str {
3513 for e in std::ascii::escape_default(c) {
3514 fmt.write_char(e as char)?;
3517 fmt.write_str("\"")?;
3522 fn comma_sep<'tcx>(fmt: &mut Formatter<'_>, elems: Vec<ConstantKind<'tcx>>) -> fmt::Result {
3523 let mut first = true;
3526 fmt.write_str(", ")?;
3528 fmt.write_str(&format!("{}", elem))?;
3534 // FIXME: Move that into `mir/pretty.rs`.
3535 fn pretty_print_const_value<'tcx>(
3536 ct: ConstValue<'tcx>,
3538 fmt: &mut Formatter<'_>,
3541 use crate::ty::print::PrettyPrinter;
3543 ty::tls::with(|tcx| {
3544 let ct = tcx.lift(ct).unwrap();
3545 let ty = tcx.lift(ty).unwrap();
3547 if tcx.sess.verbose() {
3548 fmt.write_str(&format!("ConstValue({:?}: {})", ct, ty))?;
3552 let u8_type = tcx.types.u8;
3553 match (ct, ty.kind()) {
3554 // Byte/string slices, printed as (byte) string literals.
3555 (ConstValue::Slice { data, start, end }, ty::Ref(_, inner, _)) => {
3556 match inner.kind() {
3559 // The `inspect` here is okay since we checked the bounds, and there are
3560 // no relocations (we have an active slice reference here). We don't use
3561 // this result to affect interpreter execution.
3564 .inspect_with_uninit_and_ptr_outside_interpreter(start..end);
3565 pretty_print_byte_str(fmt, byte_str)?;
3570 // The `inspect` here is okay since we checked the bounds, and there are no
3571 // relocations (we have an active `str` reference here). We don't use this
3572 // result to affect interpreter execution.
3575 .inspect_with_uninit_and_ptr_outside_interpreter(start..end);
3576 fmt.write_str(&format!("{:?}", String::from_utf8_lossy(slice)))?;
3582 (ConstValue::ByRef { alloc, offset }, ty::Array(t, n)) if *t == u8_type => {
3583 let n = n.kind().try_to_bits(tcx.data_layout.pointer_size).unwrap();
3584 // cast is ok because we already checked for pointer size (32 or 64 bit) above
3585 let range = AllocRange { start: offset, size: Size::from_bytes(n) };
3586 let byte_str = alloc.inner().get_bytes(&tcx, range).unwrap();
3587 fmt.write_str("*")?;
3588 pretty_print_byte_str(fmt, byte_str)?;
3591 // Aggregates, printed as array/tuple/struct/variant construction syntax.
3593 // NB: the `has_param_types_or_consts` check ensures that we can use
3594 // the `destructure_const` query with an empty `ty::ParamEnv` without
3595 // introducing ICEs (e.g. via `layout_of`) from missing bounds.
3596 // E.g. `transmute([0usize; 2]): (u8, *mut T)` needs to know `T: Sized`
3597 // to be able to destructure the tuple into `(0u8, *mut T)
3599 // FIXME(eddyb) for `--emit=mir`/`-Z dump-mir`, we should provide the
3600 // correct `ty::ParamEnv` to allow printing *all* constant values.
3601 (_, ty::Array(..) | ty::Tuple(..) | ty::Adt(..)) if !ty.has_param_types_or_consts() => {
3602 let ct = tcx.lift(ct).unwrap();
3603 let ty = tcx.lift(ty).unwrap();
3604 if let Some(contents) = tcx.try_destructure_mir_constant(
3605 ty::ParamEnv::reveal_all().and(ConstantKind::Val(ct, ty)),
3607 let fields = contents.fields.iter().copied().collect::<Vec<_>>();
3610 fmt.write_str("[")?;
3611 comma_sep(fmt, fields)?;
3612 fmt.write_str("]")?;
3615 fmt.write_str("(")?;
3616 comma_sep(fmt, fields)?;
3617 if contents.fields.len() == 1 {
3618 fmt.write_str(",")?;
3620 fmt.write_str(")")?;
3622 ty::Adt(def, _) if def.variants().is_empty() => {
3623 fmt.write_str(&format!("{{unreachable(): {}}}", ty))?;
3625 ty::Adt(def, substs) => {
3626 let variant_idx = contents
3628 .expect("destructed mir constant of adt without variant idx");
3629 let variant_def = &def.variant(variant_idx);
3630 let substs = tcx.lift(substs).unwrap();
3631 let mut cx = FmtPrinter::new(tcx, Namespace::ValueNS);
3632 cx.print_alloc_ids = true;
3633 let cx = cx.print_value_path(variant_def.def_id, substs)?;
3634 fmt.write_str(&cx.into_buffer())?;
3636 match variant_def.ctor_kind {
3637 CtorKind::Const => {}
3639 fmt.write_str("(")?;
3640 comma_sep(fmt, fields)?;
3641 fmt.write_str(")")?;
3643 CtorKind::Fictive => {
3644 fmt.write_str(" {{ ")?;
3645 let mut first = true;
3646 for (field_def, field) in iter::zip(&variant_def.fields, fields)
3649 fmt.write_str(", ")?;
3651 fmt.write_str(&format!("{}: {}", field_def.name, field))?;
3654 fmt.write_str(" }}")?;
3658 _ => unreachable!(),
3662 // Fall back to debug pretty printing for invalid constants.
3663 fmt.write_str(&format!("{:?}", ct))?;
3665 fmt.write_str(&format!(": {}", ty))?;
3670 (ConstValue::Scalar(scalar), _) => {
3671 let mut cx = FmtPrinter::new(tcx, Namespace::ValueNS);
3672 cx.print_alloc_ids = true;
3673 let ty = tcx.lift(ty).unwrap();
3674 cx = cx.pretty_print_const_scalar(scalar, ty, print_ty)?;
3675 fmt.write_str(&cx.into_buffer())?;
3678 // FIXME(oli-obk): also pretty print arrays and other aggregate constants by reading
3679 // their fields instead of just dumping the memory.
3683 fmt.write_str(&format!("{:?}", ct))?;
3685 fmt.write_str(&format!(": {}", ty))?;
3691 impl<'tcx> graph::DirectedGraph for Body<'tcx> {
3692 type Node = BasicBlock;
3695 impl<'tcx> graph::WithNumNodes for Body<'tcx> {
3697 fn num_nodes(&self) -> usize {
3698 self.basic_blocks.len()
3702 impl<'tcx> graph::WithStartNode for Body<'tcx> {
3704 fn start_node(&self) -> Self::Node {
3709 impl<'tcx> graph::WithSuccessors for Body<'tcx> {
3711 fn successors(&self, node: Self::Node) -> <Self as GraphSuccessors<'_>>::Iter {
3712 self.basic_blocks[node].terminator().successors()
3716 impl<'a, 'b> graph::GraphSuccessors<'b> for Body<'a> {
3717 type Item = BasicBlock;
3718 type Iter = Successors<'b>;
3721 impl<'tcx, 'graph> graph::GraphPredecessors<'graph> for Body<'tcx> {
3722 type Item = BasicBlock;
3723 type Iter = std::iter::Copied<std::slice::Iter<'graph, BasicBlock>>;
3726 impl<'tcx> graph::WithPredecessors for Body<'tcx> {
3728 fn predecessors(&self, node: Self::Node) -> <Self as graph::GraphPredecessors<'_>>::Iter {
3729 self.predecessors()[node].iter().copied()
3733 /// `Location` represents the position of the start of the statement; or, if
3734 /// `statement_index` equals the number of statements, then the start of the
3736 #[derive(Copy, Clone, PartialEq, Eq, Hash, Ord, PartialOrd, HashStable)]
3737 pub struct Location {
3738 /// The block that the location is within.
3739 pub block: BasicBlock,
3741 pub statement_index: usize,
3744 impl fmt::Debug for Location {
3745 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
3746 write!(fmt, "{:?}[{}]", self.block, self.statement_index)
3751 pub const START: Location = Location { block: START_BLOCK, statement_index: 0 };
3753 /// Returns the location immediately after this one within the enclosing block.
3755 /// Note that if this location represents a terminator, then the
3756 /// resulting location would be out of bounds and invalid.
3757 pub fn successor_within_block(&self) -> Location {
3758 Location { block: self.block, statement_index: self.statement_index + 1 }
3761 /// Returns `true` if `other` is earlier in the control flow graph than `self`.
3762 pub fn is_predecessor_of<'tcx>(&self, other: Location, body: &Body<'tcx>) -> bool {
3763 // If we are in the same block as the other location and are an earlier statement
3764 // then we are a predecessor of `other`.
3765 if self.block == other.block && self.statement_index < other.statement_index {
3769 let predecessors = body.predecessors();
3771 // If we're in another block, then we want to check that block is a predecessor of `other`.
3772 let mut queue: Vec<BasicBlock> = predecessors[other.block].to_vec();
3773 let mut visited = FxHashSet::default();
3775 while let Some(block) = queue.pop() {
3776 // If we haven't visited this block before, then make sure we visit its predecessors.
3777 if visited.insert(block) {
3778 queue.extend(predecessors[block].iter().cloned());
3783 // If we found the block that `self` is in, then we are a predecessor of `other` (since
3784 // we found that block by looking at the predecessors of `other`).
3785 if self.block == block {
3793 pub fn dominates(&self, other: Location, dominators: &Dominators<BasicBlock>) -> bool {
3794 if self.block == other.block {
3795 self.statement_index <= other.statement_index
3797 dominators.is_dominated_by(other.block, self.block)