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fuchsia / third_party / rust / 5fd9c059efaa76efeb2c85782a94aec343fd8bdc / . / compiler / rustc_middle / src / mir / mod.rs
blob: 48f39b26152cbbc40103eadfbe4daa74216d739f [file] [log] [blame]
//! MIR datatypes and passes. See the [rustc dev guide] for more info.
//!
//! [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/mir/index.html
use crate::mir::coverage::{CodeRegion, CoverageKind};
use crate::mir::interpret::{Allocation, ConstValue, GlobalAlloc, Scalar};
use crate::mir::visit::MirVisitable;
use crate::ty::adjustment::PointerCast;
use crate::ty::codec::{TyDecoder, TyEncoder};
use crate::ty::fold::{FallibleTypeFolder, TypeFoldable, TypeVisitor};
use crate::ty::print::{FmtPrinter, Printer};
use crate::ty::subst::{Subst, SubstsRef};
use crate::ty::{self, List, Ty, TyCtxt};
use crate::ty::{AdtDef, InstanceDef, Region, ScalarInt, UserTypeAnnotationIndex};
use rustc_hir::def::{CtorKind, Namespace};
use rustc_hir::def_id::{DefId, CRATE_DEF_INDEX};
use rustc_hir::{self, GeneratorKind};
use rustc_hir::{self as hir, HirId};
use rustc_session::Session;
use rustc_target::abi::{Size, VariantIdx};
use polonius_engine::Atom;
pub use rustc_ast::Mutability;
use rustc_data_structures::fx::FxHashSet;
use rustc_data_structures::graph::dominators::{dominators, Dominators};
use rustc_data_structures::graph::{self, GraphSuccessors};
use rustc_index::bit_set::BitMatrix;
use rustc_index::vec::{Idx, IndexVec};
use rustc_serialize::{Decodable, Encodable};
use rustc_span::symbol::Symbol;
use rustc_span::{Span, DUMMY_SP};
use rustc_target::asm::InlineAsmRegOrRegClass;
use either::Either;
use std::borrow::Cow;
use std::convert::TryInto;
use std::fmt::{self, Debug, Display, Formatter, Write};
use std::ops::{ControlFlow, Index, IndexMut};
use std::slice;
use std::{iter, mem, option};
use self::graph_cyclic_cache::GraphIsCyclicCache;
use self::predecessors::{PredecessorCache, Predecessors};
pub use self::query::*;
pub mod coverage;
mod generic_graph;
pub mod generic_graphviz;
mod graph_cyclic_cache;
pub mod graphviz;
pub mod interpret;
pub mod mono;
pub mod patch;
mod predecessors;
pub mod pretty;
mod query;
pub mod spanview;
pub mod tcx;
pub mod terminator;
pub use terminator::*;
pub mod traversal;
mod type_foldable;
pub mod visit;
pub use self::generic_graph::graphviz_safe_def_name;
pub use self::graphviz::write_mir_graphviz;
pub use self::pretty::{
create_dump_file, display_allocation, dump_enabled, dump_mir, write_mir_pretty, PassWhere,
};
/// Types for locals
pub type LocalDecls<'tcx> = IndexVec<Local, LocalDecl<'tcx>>;
pub trait HasLocalDecls<'tcx> {
fn local_decls(&self) -> &LocalDecls<'tcx>;
}
impl<'tcx> HasLocalDecls<'tcx> for LocalDecls<'tcx> {
#[inline]
fn local_decls(&self) -> &LocalDecls<'tcx> {
self
}
}
impl<'tcx> HasLocalDecls<'tcx> for Body<'tcx> {
#[inline]
fn local_decls(&self) -> &LocalDecls<'tcx> {
&self.local_decls
}
}
/// A streamlined trait that you can implement to create a pass; the
/// pass will be named after the type, and it will consist of a main
/// loop that goes over each available MIR and applies `run_pass`.
pub trait MirPass<'tcx> {
fn name(&self) -> Cow<'_, str> {
let name = std::any::type_name::<Self>();
if let Some(tail) = name.rfind(':') {
Cow::from(&name[tail + 1..])
} else {
Cow::from(name)
}
}
/// Returns `true` if this pass is enabled with the current combination of compiler flags.
fn is_enabled(&self, _sess: &Session) -> bool {
true
}
fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>);
/// If this pass causes the MIR to enter a new phase, return that phase.
fn phase_change(&self) -> Option<MirPhase> {
None
}
fn is_mir_dump_enabled(&self) -> bool {
true
}
}
/// The various "big phases" that MIR goes through.
///
/// These phases all describe dialects of MIR. Since all MIR uses the same datastructures, the
/// dialects forbid certain variants or values in certain phases.
///
/// Note: Each phase's validation checks all invariants of the *previous* phases' dialects. A phase
/// that changes the dialect documents what invariants must be upheld *after* that phase finishes.
///
/// Warning: ordering of variants is significant.
#[derive(Copy, Clone, TyEncodable, TyDecodable, Debug, PartialEq, Eq, PartialOrd, Ord)]
#[derive(HashStable)]
pub enum MirPhase {
Build = 0,
// FIXME(oli-obk): it's unclear whether we still need this phase (and its corresponding query).
// We used to have this for pre-miri MIR based const eval.
Const = 1,
/// This phase checks the MIR for promotable elements and takes them out of the main MIR body
/// by creating a new MIR body per promoted element. After this phase (and thus the termination
/// of the `mir_promoted` query), these promoted elements are available in the `promoted_mir`
/// query.
ConstPromotion = 2,
/// After this phase
/// * the only `AggregateKind`s allowed are `Array` and `Generator`,
/// * `DropAndReplace` is gone for good
/// * `Drop` now uses explicit drop flags visible in the MIR and reaching a `Drop` terminator
/// means that the auto-generated drop glue will be invoked.
DropLowering = 3,
/// After this phase, generators are explicit state machines (no more `Yield`).
/// `AggregateKind::Generator` is gone for good.
GeneratorLowering = 4,
Optimization = 5,
}
impl MirPhase {
/// Gets the index of the current MirPhase within the set of all `MirPhase`s.
pub fn phase_index(&self) -> usize {
*self as usize
}
}
/// Where a specific `mir::Body` comes from.
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
#[derive(HashStable, TyEncodable, TyDecodable, TypeFoldable)]
pub struct MirSource<'tcx> {
pub instance: InstanceDef<'tcx>,
/// If `Some`, this is a promoted rvalue within the parent function.
pub promoted: Option<Promoted>,
}
impl<'tcx> MirSource<'tcx> {
pub fn item(def_id: DefId) -> Self {
MirSource {
instance: InstanceDef::Item(ty::WithOptConstParam::unknown(def_id)),
promoted: None,
}
}
pub fn from_instance(instance: InstanceDef<'tcx>) -> Self {
MirSource { instance, promoted: None }
}
pub fn with_opt_param(self) -> ty::WithOptConstParam<DefId> {
self.instance.with_opt_param()
}
#[inline]
pub fn def_id(&self) -> DefId {
self.instance.def_id()
}
}
#[derive(Clone, TyEncodable, TyDecodable, Debug, HashStable, TypeFoldable)]
pub struct GeneratorInfo<'tcx> {
/// The yield type of the function, if it is a generator.
pub yield_ty: Option<Ty<'tcx>>,
/// Generator drop glue.
pub generator_drop: Option<Body<'tcx>>,
/// The layout of a generator. Produced by the state transformation.
pub generator_layout: Option<GeneratorLayout<'tcx>>,
/// If this is a generator then record the type of source expression that caused this generator
/// to be created.
pub generator_kind: GeneratorKind,
}
/// The lowered representation of a single function.
#[derive(Clone, TyEncodable, TyDecodable, Debug, HashStable, TypeFoldable)]
pub struct Body<'tcx> {
/// A list of basic blocks. References to basic block use a newtyped index type [`BasicBlock`]
/// that indexes into this vector.
basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,
/// Records how far through the "desugaring and optimization" process this particular
/// MIR has traversed. This is particularly useful when inlining, since in that context
/// we instantiate the promoted constants and add them to our promoted vector -- but those
/// promoted items have already been optimized, whereas ours have not. This field allows
/// us to see the difference and forego optimization on the inlined promoted items.
pub phase: MirPhase,
pub source: MirSource<'tcx>,
/// A list of source scopes; these are referenced by statements
/// and used for debuginfo. Indexed by a `SourceScope`.
pub source_scopes: IndexVec<SourceScope, SourceScopeData<'tcx>>,
pub generator: Option<Box<GeneratorInfo<'tcx>>>,
/// Declarations of locals.
///
/// The first local is the return value pointer, followed by `arg_count`
/// locals for the function arguments, followed by any user-declared
/// variables and temporaries.
pub local_decls: LocalDecls<'tcx>,
/// User type annotations.
pub user_type_annotations: ty::CanonicalUserTypeAnnotations<'tcx>,
/// The number of arguments this function takes.
///
/// Starting at local 1, `arg_count` locals will be provided by the caller
/// and can be assumed to be initialized.
///
/// If this MIR was built for a constant, this will be 0.
pub arg_count: usize,
/// Mark an argument local (which must be a tuple) as getting passed as
/// its individual components at the LLVM level.
///
/// This is used for the "rust-call" ABI.
pub spread_arg: Option<Local>,
/// Debug information pertaining to user variables, including captures.
pub var_debug_info: Vec<VarDebugInfo<'tcx>>,
/// A span representing this MIR, for error reporting.
pub span: Span,
/// Constants that are required to evaluate successfully for this MIR to be well-formed.
/// We hold in this field all the constants we are not able to evaluate yet.
pub required_consts: Vec<Constant<'tcx>>,
/// Does this body use generic parameters. This is used for the `ConstEvaluatable` check.
///
/// Note that this does not actually mean that this body is not computable right now.
/// The repeat count in the following example is polymorphic, but can still be evaluated
/// without knowing anything about the type parameter `T`.
///
/// ```rust
/// fn test<T>() {
/// let _ = [0; std::mem::size_of::<*mut T>()];
/// }
/// ```
///
/// **WARNING**: Do not change this flags after the MIR was originally created, even if an optimization
/// removed the last mention of all generic params. We do not want to rely on optimizations and
/// potentially allow things like `[u8; std::mem::size_of::<T>() * 0]` due to this.
pub is_polymorphic: bool,
predecessor_cache: PredecessorCache,
is_cyclic: GraphIsCyclicCache,
}
impl<'tcx> Body<'tcx> {
pub fn new(
source: MirSource<'tcx>,
basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,
source_scopes: IndexVec<SourceScope, SourceScopeData<'tcx>>,
local_decls: LocalDecls<'tcx>,
user_type_annotations: ty::CanonicalUserTypeAnnotations<'tcx>,
arg_count: usize,
var_debug_info: Vec<VarDebugInfo<'tcx>>,
span: Span,
generator_kind: Option<GeneratorKind>,
) -> Self {
// We need `arg_count` locals, and one for the return place.
assert!(
local_decls.len() > arg_count,
"expected at least {} locals, got {}",
arg_count + 1,
local_decls.len()
);
let mut body = Body {
phase: MirPhase::Build,
source,
basic_blocks,
source_scopes,
generator: generator_kind.map(|generator_kind| {
Box::new(GeneratorInfo {
yield_ty: None,
generator_drop: None,
generator_layout: None,
generator_kind,
})
}),
local_decls,
user_type_annotations,
arg_count,
spread_arg: None,
var_debug_info,
span,
required_consts: Vec::new(),
is_polymorphic: false,
predecessor_cache: PredecessorCache::new(),
is_cyclic: GraphIsCyclicCache::new(),
};
body.is_polymorphic = body.has_param_types_or_consts();
body
}
/// Returns a partially initialized MIR body containing only a list of basic blocks.
///
/// The returned MIR contains no `LocalDecl`s (even for the return place) or source scopes. It
/// is only useful for testing but cannot be `#[cfg(test)]` because it is used in a different
/// crate.
pub fn new_cfg_only(basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>) -> Self {
let mut body = Body {
phase: MirPhase::Build,
source: MirSource::item(DefId::local(CRATE_DEF_INDEX)),
basic_blocks,
source_scopes: IndexVec::new(),
generator: None,
local_decls: IndexVec::new(),
user_type_annotations: IndexVec::new(),
arg_count: 0,
spread_arg: None,
span: DUMMY_SP,
required_consts: Vec::new(),
var_debug_info: Vec::new(),
is_polymorphic: false,
predecessor_cache: PredecessorCache::new(),
is_cyclic: GraphIsCyclicCache::new(),
};
body.is_polymorphic = body.has_param_types_or_consts();
body
}
#[inline]
pub fn basic_blocks(&self) -> &IndexVec<BasicBlock, BasicBlockData<'tcx>> {
&self.basic_blocks
}
#[inline]
pub fn basic_blocks_mut(&mut self) -> &mut IndexVec<BasicBlock, BasicBlockData<'tcx>> {
// Because the user could mutate basic block terminators via this reference, we need to
// invalidate the caches.
//
// FIXME: Use a finer-grained API for this, so only transformations that alter terminators
// invalidate the caches.
self.predecessor_cache.invalidate();
self.is_cyclic.invalidate();
&mut self.basic_blocks
}
#[inline]
pub fn basic_blocks_and_local_decls_mut(
&mut self,
) -> (&mut IndexVec<BasicBlock, BasicBlockData<'tcx>>, &mut LocalDecls<'tcx>) {
self.predecessor_cache.invalidate();
self.is_cyclic.invalidate();
(&mut self.basic_blocks, &mut self.local_decls)
}
#[inline]
pub fn basic_blocks_local_decls_mut_and_var_debug_info(
&mut self,
) -> (
&mut IndexVec<BasicBlock, BasicBlockData<'tcx>>,
&mut LocalDecls<'tcx>,
&mut Vec<VarDebugInfo<'tcx>>,
) {
self.predecessor_cache.invalidate();
self.is_cyclic.invalidate();
(&mut self.basic_blocks, &mut self.local_decls, &mut self.var_debug_info)
}
/// Returns `true` if a cycle exists in the control-flow graph that is reachable from the
/// `START_BLOCK`.
pub fn is_cfg_cyclic(&self) -> bool {
self.is_cyclic.is_cyclic(self)
}
#[inline]
pub fn local_kind(&self, local: Local) -> LocalKind {
let index = local.as_usize();
if index == 0 {
debug_assert!(
self.local_decls[local].mutability == Mutability::Mut,
"return place should be mutable"
);
LocalKind::ReturnPointer
} else if index < self.arg_count + 1 {
LocalKind::Arg
} else if self.local_decls[local].is_user_variable() {
LocalKind::Var
} else {
LocalKind::Temp
}
}
/// Returns an iterator over all user-declared mutable locals.
#[inline]
pub fn mut_vars_iter<'a>(&'a self) -> impl Iterator<Item = Local> + 'a {
(self.arg_count + 1..self.local_decls.len()).filter_map(move |index| {
let local = Local::new(index);
let decl = &self.local_decls[local];
if decl.is_user_variable() && decl.mutability == Mutability::Mut {
Some(local)
} else {
None
}
})
}
/// Returns an iterator over all user-declared mutable arguments and locals.
#[inline]
pub fn mut_vars_and_args_iter<'a>(&'a self) -> impl Iterator<Item = Local> + 'a {
(1..self.local_decls.len()).filter_map(move |index| {
let local = Local::new(index);
let decl = &self.local_decls[local];
if (decl.is_user_variable() || index < self.arg_count + 1)
&& decl.mutability == Mutability::Mut
{
Some(local)
} else {
None
}
})
}
/// Returns an iterator over all function arguments.
#[inline]
pub fn args_iter(&self) -> impl Iterator<Item = Local> + ExactSizeIterator {
(1..self.arg_count + 1).map(Local::new)
}
/// Returns an iterator over all user-defined variables and compiler-generated temporaries (all
/// locals that are neither arguments nor the return place).
#[inline]
pub fn vars_and_temps_iter(
&self,
) -> impl DoubleEndedIterator<Item = Local> + ExactSizeIterator {
(self.arg_count + 1..self.local_decls.len()).map(Local::new)
}
#[inline]
pub fn drain_vars_and_temps<'a>(&'a mut self) -> impl Iterator<Item = LocalDecl<'tcx>> + 'a {
self.local_decls.drain(self.arg_count + 1..)
}
/// Changes a statement to a nop. This is both faster than deleting instructions and avoids
/// invalidating statement indices in `Location`s.
pub fn make_statement_nop(&mut self, location: Location) {
let block = &mut self.basic_blocks[location.block];
debug_assert!(location.statement_index < block.statements.len());
block.statements[location.statement_index].make_nop()
}
/// Returns the source info associated with `location`.
pub fn source_info(&self, location: Location) -> &SourceInfo {
let block = &self[location.block];
let stmts = &block.statements;
let idx = location.statement_index;
if idx < stmts.len() {
&stmts[idx].source_info
} else {
assert_eq!(idx, stmts.len());
&block.terminator().source_info
}
}
/// Returns the return type; it always return first element from `local_decls` array.
#[inline]
pub fn return_ty(&self) -> Ty<'tcx> {
self.local_decls[RETURN_PLACE].ty
}
/// Gets the location of the terminator for the given block.
#[inline]
pub fn terminator_loc(&self, bb: BasicBlock) -> Location {
Location { block: bb, statement_index: self[bb].statements.len() }
}
pub fn stmt_at(&self, location: Location) -> Either<&Statement<'tcx>, &Terminator<'tcx>> {
let Location { block, statement_index } = location;
let block_data = &self.basic_blocks[block];
block_data
.statements
.get(statement_index)
.map(Either::Left)
.unwrap_or_else(|| Either::Right(block_data.terminator()))
}
#[inline]
pub fn predecessors(&self) -> &Predecessors {
self.predecessor_cache.compute(&self.basic_blocks)
}
#[inline]
pub fn dominators(&self) -> Dominators<BasicBlock> {
dominators(self)
}
#[inline]
pub fn yield_ty(&self) -> Option<Ty<'tcx>> {
self.generator.as_ref().and_then(|generator| generator.yield_ty)
}
#[inline]
pub fn generator_layout(&self) -> Option<&GeneratorLayout<'tcx>> {
self.generator.as_ref().and_then(|generator| generator.generator_layout.as_ref())
}
#[inline]
pub fn generator_drop(&self) -> Option<&Body<'tcx>> {
self.generator.as_ref().and_then(|generator| generator.generator_drop.as_ref())
}
#[inline]
pub fn generator_kind(&self) -> Option<GeneratorKind> {
self.generator.as_ref().map(|generator| generator.generator_kind)
}
}
#[derive(Copy, Clone, PartialEq, Eq, Debug, TyEncodable, TyDecodable, HashStable)]
pub enum Safety {
Safe,
/// Unsafe because of compiler-generated unsafe code, like `await` desugaring
BuiltinUnsafe,
/// Unsafe because of an unsafe fn
FnUnsafe,
/// Unsafe because of an `unsafe` block
ExplicitUnsafe(hir::HirId),
}
impl<'tcx> Index<BasicBlock> for Body<'tcx> {
type Output = BasicBlockData<'tcx>;
#[inline]
fn index(&self, index: BasicBlock) -> &BasicBlockData<'tcx> {
&self.basic_blocks()[index]
}
}
impl<'tcx> IndexMut<BasicBlock> for Body<'tcx> {
#[inline]
fn index_mut(&mut self, index: BasicBlock) -> &mut BasicBlockData<'tcx> {
&mut self.basic_blocks_mut()[index]
}
}
#[derive(Copy, Clone, Debug, HashStable, TypeFoldable)]
pub enum ClearCrossCrate<T> {
Clear,
Set(T),
}
impl<T> ClearCrossCrate<T> {
pub fn as_ref(&self) -> ClearCrossCrate<&T> {
match self {
ClearCrossCrate::Clear => ClearCrossCrate::Clear,
ClearCrossCrate::Set(v) => ClearCrossCrate::Set(v),
}
}
pub fn assert_crate_local(self) -> T {
match self {
ClearCrossCrate::Clear => bug!("unwrapping cross-crate data"),
ClearCrossCrate::Set(v) => v,
}
}
}
const TAG_CLEAR_CROSS_CRATE_CLEAR: u8 = 0;
const TAG_CLEAR_CROSS_CRATE_SET: u8 = 1;
impl<'tcx, E: TyEncoder<'tcx>, T: Encodable<E>> Encodable<E> for ClearCrossCrate<T> {
#[inline]
fn encode(&self, e: &mut E) -> Result<(), E::Error> {
if E::CLEAR_CROSS_CRATE {
return Ok(());
}
match *self {
ClearCrossCrate::Clear => TAG_CLEAR_CROSS_CRATE_CLEAR.encode(e),
ClearCrossCrate::Set(ref val) => {
TAG_CLEAR_CROSS_CRATE_SET.encode(e)?;
val.encode(e)
}
}
}
}
impl<'tcx, D: TyDecoder<'tcx>, T: Decodable<D>> Decodable<D> for ClearCrossCrate<T> {
#[inline]
fn decode(d: &mut D) -> Result<ClearCrossCrate<T>, D::Error> {
if D::CLEAR_CROSS_CRATE {
return Ok(ClearCrossCrate::Clear);
}
let discr = u8::decode(d)?;
match discr {
TAG_CLEAR_CROSS_CRATE_CLEAR => Ok(ClearCrossCrate::Clear),
TAG_CLEAR_CROSS_CRATE_SET => {
let val = T::decode(d)?;
Ok(ClearCrossCrate::Set(val))
}
tag => Err(d.error(&format!("Invalid tag for ClearCrossCrate: {:?}", tag))),
}
}
}
/// Grouped information about the source code origin of a MIR entity.
/// Intended to be inspected by diagnostics and debuginfo.
/// Most passes can work with it as a whole, within a single function.
// The unofficial Cranelift backend, at least as of #65828, needs `SourceInfo` to implement `Eq` and
// `Hash`. Please ping @bjorn3 if removing them.
#[derive(Copy, Clone, Debug, Eq, PartialEq, TyEncodable, TyDecodable, Hash, HashStable)]
pub struct SourceInfo {
/// The source span for the AST pertaining to this MIR entity.
pub span: Span,
/// The source scope, keeping track of which bindings can be
/// seen by debuginfo, active lint levels, `unsafe {...}`, etc.
pub scope: SourceScope,
}
impl SourceInfo {
#[inline]
pub fn outermost(span: Span) -> Self {
SourceInfo { span, scope: OUTERMOST_SOURCE_SCOPE }
}
}
///////////////////////////////////////////////////////////////////////////
// Borrow kinds
#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, TyEncodable, TyDecodable)]
#[derive(Hash, HashStable)]
pub enum BorrowKind {
/// Data must be immutable and is aliasable.
Shared,
/// The immediately borrowed place must be immutable, but projections from
/// it don't need to be. For example, a shallow borrow of `a.b` doesn't
/// conflict with a mutable borrow of `a.b.c`.
///
/// This is used when lowering matches: when matching on a place we want to
/// ensure that place have the same value from the start of the match until
/// an arm is selected. This prevents this code from compiling:
///
/// let mut x = &Some(0);
/// match *x {
/// None => (),
/// Some(_) if { x = &None; false } => (),
/// Some(_) => (),
/// }
///
/// This can't be a shared borrow because mutably borrowing (*x as Some).0
/// should not prevent `if let None = x { ... }`, for example, because the
/// mutating `(*x as Some).0` can't affect the discriminant of `x`.
/// We can also report errors with this kind of borrow differently.
Shallow,
/// Data must be immutable but not aliasable. This kind of borrow
/// cannot currently be expressed by the user and is used only in
/// implicit closure bindings. It is needed when the closure is
/// borrowing or mutating a mutable referent, e.g.:
///
/// let x: &mut isize = ...;
/// let y = || *x += 5;
///
/// If we were to try to translate this closure into a more explicit
/// form, we'd encounter an error with the code as written:
///
/// struct Env { x: & &mut isize }
/// let x: &mut isize = ...;
/// let y = (&mut Env { &x }, fn_ptr); // Closure is pair of env and fn
/// fn fn_ptr(env: &mut Env) { **env.x += 5; }
///
/// This is then illegal because you cannot mutate an `&mut` found
/// in an aliasable location. To solve, you'd have to translate with
/// an `&mut` borrow:
///
/// struct Env { x: &mut &mut isize }
/// let x: &mut isize = ...;
/// let y = (&mut Env { &mut x }, fn_ptr); // changed from &x to &mut x
/// fn fn_ptr(env: &mut Env) { **env.x += 5; }
///
/// Now the assignment to `**env.x` is legal, but creating a
/// mutable pointer to `x` is not because `x` is not mutable. We
/// could fix this by declaring `x` as `let mut x`. This is ok in
/// user code, if awkward, but extra weird for closures, since the
/// borrow is hidden.
///
/// So we introduce a "unique imm" borrow -- the referent is
/// immutable, but not aliasable. This solves the problem. For
/// simplicity, we don't give users the way to express this
/// borrow, it's just used when translating closures.
Unique,
/// Data is mutable and not aliasable.
Mut {
/// `true` if this borrow arose from method-call auto-ref
/// (i.e., `adjustment::Adjust::Borrow`).
allow_two_phase_borrow: bool,
},
}
impl BorrowKind {
pub fn allows_two_phase_borrow(&self) -> bool {
match *self {
BorrowKind::Shared | BorrowKind::Shallow | BorrowKind::Unique => false,
BorrowKind::Mut { allow_two_phase_borrow } => allow_two_phase_borrow,
}
}
pub fn describe_mutability(&self) -> String {
match *self {
BorrowKind::Shared | BorrowKind::Shallow | BorrowKind::Unique => {
"immutable".to_string()
}
BorrowKind::Mut { .. } => "mutable".to_string(),
}
}
}
///////////////////////////////////////////////////////////////////////////
// Variables and temps
rustc_index::newtype_index! {
pub struct Local {
derive [HashStable]
DEBUG_FORMAT = "_{}",
const RETURN_PLACE = 0,
}
}
impl Atom for Local {
fn index(self) -> usize {
Idx::index(self)
}
}
/// Classifies locals into categories. See `Body::local_kind`.
#[derive(Clone, Copy, PartialEq, Eq, Debug, HashStable)]
pub enum LocalKind {
/// User-declared variable binding.
Var,
/// Compiler-introduced temporary.
Temp,
/// Function argument.
Arg,
/// Location of function's return value.
ReturnPointer,
}
#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
pub struct VarBindingForm<'tcx> {
/// Is variable bound via `x`, `mut x`, `ref x`, or `ref mut x`?
pub binding_mode: ty::BindingMode,
/// If an explicit type was provided for this variable binding,
/// this holds the source Span of that type.
///
/// NOTE: if you want to change this to a `HirId`, be wary that
/// doing so breaks incremental compilation (as of this writing),
/// while a `Span` does not cause our tests to fail.
pub opt_ty_info: Option<Span>,
/// Place of the RHS of the =, or the subject of the `match` where this
/// variable is initialized. None in the case of `let PATTERN;`.
/// Some((None, ..)) in the case of and `let [mut] x = ...` because
/// (a) the right-hand side isn't evaluated as a place expression.
/// (b) it gives a way to separate this case from the remaining cases
/// for diagnostics.
pub opt_match_place: Option<(Option<Place<'tcx>>, Span)>,
/// The span of the pattern in which this variable was bound.
pub pat_span: Span,
}
#[derive(Clone, Debug, TyEncodable, TyDecodable)]
pub enum BindingForm<'tcx> {
/// This is a binding for a non-`self` binding, or a `self` that has an explicit type.
Var(VarBindingForm<'tcx>),
/// Binding for a `self`/`&self`/`&mut self` binding where the type is implicit.
ImplicitSelf(ImplicitSelfKind),
/// Reference used in a guard expression to ensure immutability.
RefForGuard,
}
/// Represents what type of implicit self a function has, if any.
#[derive(Clone, Copy, PartialEq, Debug, TyEncodable, TyDecodable, HashStable)]
pub enum ImplicitSelfKind {
/// Represents a `fn x(self);`.
Imm,
/// Represents a `fn x(mut self);`.
Mut,
/// Represents a `fn x(&self);`.
ImmRef,
/// Represents a `fn x(&mut self);`.
MutRef,
/// Represents when a function does not have a self argument or
/// when a function has a `self: X` argument.
None,
}
TrivialTypeFoldableAndLiftImpls! { BindingForm<'tcx>, }
mod binding_form_impl {
use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
use rustc_query_system::ich::StableHashingContext;
impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for super::BindingForm<'tcx> {
fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
use super::BindingForm::*;
std::mem::discriminant(self).hash_stable(hcx, hasher);
match self {
Var(binding) => binding.hash_stable(hcx, hasher),
ImplicitSelf(kind) => kind.hash_stable(hcx, hasher),
RefForGuard => (),
}
}
}
}
/// `BlockTailInfo` is attached to the `LocalDecl` for temporaries
/// created during evaluation of expressions in a block tail
/// expression; that is, a block like `{ STMT_1; STMT_2; EXPR }`.
///
/// It is used to improve diagnostics when such temporaries are
/// involved in borrow_check errors, e.g., explanations of where the
/// temporaries come from, when their destructors are run, and/or how
/// one might revise the code to satisfy the borrow checker's rules.
#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
pub struct BlockTailInfo {
/// If `true`, then the value resulting from evaluating this tail
/// expression is ignored by the block's expression context.
///
/// Examples include `{ ...; tail };` and `let _ = { ...; tail };`
/// but not e.g., `let _x = { ...; tail };`
pub tail_result_is_ignored: bool,
/// `Span` of the tail expression.
pub span: Span,
}
/// A MIR local.
///
/// This can be a binding declared by the user, a temporary inserted by the compiler, a function
/// argument, or the return place.
#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
pub struct LocalDecl<'tcx> {
/// Whether this is a mutable binding (i.e., `let x` or `let mut x`).
///
/// Temporaries and the return place are always mutable.
pub mutability: Mutability,
// FIXME(matthewjasper) Don't store in this in `Body`
pub local_info: Option<Box<LocalInfo<'tcx>>>,
/// `true` if this is an internal local.
///
/// These locals are not based on types in the source code and are only used
/// for a few desugarings at the moment.
///
/// The generator transformation will sanity check the locals which are live
/// across a suspension point against the type components of the generator
/// which type checking knows are live across a suspension point. We need to
/// flag drop flags to avoid triggering this check as they are introduced
/// after typeck.
///
/// This should be sound because the drop flags are fully algebraic, and
/// therefore don't affect the auto-trait or outlives properties of the
/// generator.
pub internal: bool,
/// If this local is a temporary and `is_block_tail` is `Some`,
/// then it is a temporary created for evaluation of some
/// subexpression of some block's tail expression (with no
/// intervening statement context).
// FIXME(matthewjasper) Don't store in this in `Body`
pub is_block_tail: Option<BlockTailInfo>,
/// The type of this local.
pub ty: Ty<'tcx>,
/// If the user manually ascribed a type to this variable,
/// e.g., via `let x: T`, then we carry that type here. The MIR
/// borrow checker needs this information since it can affect
/// region inference.
// FIXME(matthewjasper) Don't store in this in `Body`
pub user_ty: Option<Box<UserTypeProjections>>,
/// The *syntactic* (i.e., not visibility) source scope the local is defined
/// in. If the local was defined in a let-statement, this
/// is *within* the let-statement, rather than outside
/// of it.
///
/// This is needed because the visibility source scope of locals within
/// a let-statement is weird.
///
/// The reason is that we want the local to be *within* the let-statement
/// for lint purposes, but we want the local to be *after* the let-statement
/// for names-in-scope purposes.
///
/// That's it, if we have a let-statement like the one in this
/// function:
///
/// ```
/// fn foo(x: &str) {
/// #[allow(unused_mut)]
/// let mut x: u32 = { // <- one unused mut
/// let mut y: u32 = x.parse().unwrap();
/// y + 2
/// };
/// drop(x);
/// }
/// ```
///
/// Then, from a lint point of view, the declaration of `x: u32`
/// (and `y: u32`) are within the `#[allow(unused_mut)]` scope - the
/// lint scopes are the same as the AST/HIR nesting.
///
/// However, from a name lookup point of view, the scopes look more like
/// as if the let-statements were `match` expressions:
///
/// ```
/// fn foo(x: &str) {
/// match {
/// match x.parse().unwrap() {
/// y => y + 2
/// }
/// } {
/// x => drop(x)
/// };
/// }
/// ```
///
/// We care about the name-lookup scopes for debuginfo - if the
/// debuginfo instruction pointer is at the call to `x.parse()`, we
/// want `x` to refer to `x: &str`, but if it is at the call to
/// `drop(x)`, we want it to refer to `x: u32`.
///
/// To allow both uses to work, we need to have more than a single scope
/// for a local. We have the `source_info.scope` represent the "syntactic"
/// lint scope (with a variable being under its let block) while the
/// `var_debug_info.source_info.scope` represents the "local variable"
/// scope (where the "rest" of a block is under all prior let-statements).
///
/// The end result looks like this:
///
/// ```text
/// ROOT SCOPE
/// │{ argument x: &str }
/// │
/// │ │{ #[allow(unused_mut)] } // This is actually split into 2 scopes
/// │ │ // in practice because I'm lazy.
/// │ │
/// │ │← x.source_info.scope
/// │ │← `x.parse().unwrap()`
/// │ │
/// │ │ │← y.source_info.scope
/// │ │
/// │ │ │{ let y: u32 }
/// │ │ │
/// │ │ │← y.var_debug_info.source_info.scope
/// │ │ │← `y + 2`
/// │
/// │ │{ let x: u32 }
/// │ │← x.var_debug_info.source_info.scope
/// │ │← `drop(x)` // This accesses `x: u32`.
/// ```
pub source_info: SourceInfo,
}
// `LocalDecl` is used a lot. Make sure it doesn't unintentionally get bigger.
#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
static_assert_size!(LocalDecl<'_>, 56);
/// Extra information about a some locals that's used for diagnostics and for
/// classifying variables into local variables, statics, etc, which is needed e.g.
/// for unsafety checking.
///
/// Not used for non-StaticRef temporaries, the return place, or anonymous
/// function parameters.
#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
pub enum LocalInfo<'tcx> {
/// A user-defined local variable or function parameter
///
/// The `BindingForm` is solely used for local diagnostics when generating
/// warnings/errors when compiling the current crate, and therefore it need
/// not be visible across crates.
User(ClearCrossCrate<BindingForm<'tcx>>),
/// A temporary created that references the static with the given `DefId`.
StaticRef { def_id: DefId, is_thread_local: bool },
/// A temporary created that references the const with the given `DefId`
ConstRef { def_id: DefId },
/// A temporary created during the creation of an aggregate
/// (e.g. a temporary for `foo` in `MyStruct { my_field: foo }`)
AggregateTemp,
}
impl<'tcx> LocalDecl<'tcx> {
/// Returns `true` only if local is a binding that can itself be
/// made mutable via the addition of the `mut` keyword, namely
/// something like the occurrences of `x` in:
/// - `fn foo(x: Type) { ... }`,
/// - `let x = ...`,
/// - or `match ... { C(x) => ... }`
pub fn can_be_made_mutable(&self) -> bool {
matches!(
self.local_info,
Some(box LocalInfo::User(ClearCrossCrate::Set(
BindingForm::Var(VarBindingForm {
binding_mode: ty::BindingMode::BindByValue(_),
opt_ty_info: _,
opt_match_place: _,
pat_span: _,
}) | BindingForm::ImplicitSelf(ImplicitSelfKind::Imm),
)))
)
}
/// Returns `true` if local is definitely not a `ref ident` or
/// `ref mut ident` binding. (Such bindings cannot be made into
/// mutable bindings, but the inverse does not necessarily hold).
pub fn is_nonref_binding(&self) -> bool {
matches!(
self.local_info,
Some(box LocalInfo::User(ClearCrossCrate::Set(
BindingForm::Var(VarBindingForm {
binding_mode: ty::BindingMode::BindByValue(_),
opt_ty_info: _,
opt_match_place: _,
pat_span: _,
}) | BindingForm::ImplicitSelf(_),
)))
)
}
/// Returns `true` if this variable is a named variable or function
/// parameter declared by the user.
#[inline]
pub fn is_user_variable(&self) -> bool {
matches!(self.local_info, Some(box LocalInfo::User(_)))
}
/// Returns `true` if this is a reference to a variable bound in a `match`
/// expression that is used to access said variable for the guard of the
/// match arm.
pub fn is_ref_for_guard(&self) -> bool {
matches!(
self.local_info,
Some(box LocalInfo::User(ClearCrossCrate::Set(BindingForm::RefForGuard)))
)
}
/// Returns `Some` if this is a reference to a static item that is used to
/// access that static.
pub fn is_ref_to_static(&self) -> bool {
matches!(self.local_info, Some(box LocalInfo::StaticRef { .. }))
}
/// Returns `Some` if this is a reference to a thread-local static item that is used to
/// access that static.
pub fn is_ref_to_thread_local(&self) -> bool {
match self.local_info {
Some(box LocalInfo::StaticRef { is_thread_local, .. }) => is_thread_local,
_ => false,
}
}
/// Returns `true` is the local is from a compiler desugaring, e.g.,
/// `__next` from a `for` loop.
#[inline]
pub fn from_compiler_desugaring(&self) -> bool {
self.source_info.span.desugaring_kind().is_some()
}
/// Creates a new `LocalDecl` for a temporary: mutable, non-internal.
#[inline]
pub fn new(ty: Ty<'tcx>, span: Span) -> Self {
Self::with_source_info(ty, SourceInfo::outermost(span))
}
/// Like `LocalDecl::new`, but takes a `SourceInfo` instead of a `Span`.
#[inline]
pub fn with_source_info(ty: Ty<'tcx>, source_info: SourceInfo) -> Self {
LocalDecl {
mutability: Mutability::Mut,
local_info: None,
internal: false,
is_block_tail: None,
ty,
user_ty: None,
source_info,
}
}
/// Converts `self` into same `LocalDecl` except tagged as internal.
#[inline]
pub fn internal(mut self) -> Self {
self.internal = true;
self
}
/// Converts `self` into same `LocalDecl` except tagged as immutable.
#[inline]
pub fn immutable(mut self) -> Self {
self.mutability = Mutability::Not;
self
}
/// Converts `self` into same `LocalDecl` except tagged as internal temporary.
#[inline]
pub fn block_tail(mut self, info: BlockTailInfo) -> Self {
assert!(self.is_block_tail.is_none());
self.is_block_tail = Some(info);
self
}
}
#[derive(Clone, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
pub enum VarDebugInfoContents<'tcx> {
/// NOTE(eddyb) There's an unenforced invariant that this `Place` is
/// based on a `Local`, not a `Static`, and contains no indexing.
Place(Place<'tcx>),
Const(Constant<'tcx>),
}
impl<'tcx> Debug for VarDebugInfoContents<'tcx> {
fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
match self {
VarDebugInfoContents::Const(c) => write!(fmt, "{}", c),
VarDebugInfoContents::Place(p) => write!(fmt, "{:?}", p),
}
}
}
/// Debug information pertaining to a user variable.
#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
pub struct VarDebugInfo<'tcx> {
pub name: Symbol,
/// Source info of the user variable, including the scope
/// within which the variable is visible (to debuginfo)
/// (see `LocalDecl`'s `source_info` field for more details).
pub source_info: SourceInfo,
/// Where the data for this user variable is to be found.
pub value: VarDebugInfoContents<'tcx>,
}
///////////////////////////////////////////////////////////////////////////
// BasicBlock
rustc_index::newtype_index! {
/// A node in the MIR [control-flow graph][CFG].
///
/// There are no branches (e.g., `if`s, function calls, etc.) within a basic block, which makes
/// it easier to do [data-flow analyses] and optimizations. Instead, branches are represented
/// as an edge in a graph between basic blocks.
///
/// Basic blocks consist of a series of [statements][Statement], ending with a
/// [terminator][Terminator]. Basic blocks can have multiple predecessors and successors,
/// however there is a MIR pass ([`CriticalCallEdges`]) that removes *critical edges*, which
/// are edges that go from a multi-successor node to a multi-predecessor node. This pass is
/// needed because some analyses require that there are no critical edges in the CFG.
///
/// Note that this type is just an index into [`Body.basic_blocks`](Body::basic_blocks);
/// the actual data that a basic block holds is in [`BasicBlockData`].
///
/// Read more about basic blocks in the [rustc-dev-guide][guide-mir].
///
/// [CFG]: https://rustc-dev-guide.rust-lang.org/appendix/background.html#cfg
/// [data-flow analyses]:
/// https://rustc-dev-guide.rust-lang.org/appendix/background.html#what-is-a-dataflow-analysis
/// [`CriticalCallEdges`]: ../../rustc_const_eval/transform/add_call_guards/enum.AddCallGuards.html#variant.CriticalCallEdges
/// [guide-mir]: https://rustc-dev-guide.rust-lang.org/mir/
pub struct BasicBlock {
derive [HashStable]
DEBUG_FORMAT = "bb{}",
const START_BLOCK = 0,
}
}
impl BasicBlock {
pub fn start_location(self) -> Location {
Location { block: self, statement_index: 0 }
}
}
///////////////////////////////////////////////////////////////////////////
// BasicBlockData and Terminator
/// See [`BasicBlock`] for documentation on what basic blocks are at a high level.
#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
pub struct BasicBlockData<'tcx> {
/// List of statements in this block.
pub statements: Vec<Statement<'tcx>>,
/// Terminator for this block.
///
/// N.B., this should generally ONLY be `None` during construction.
/// Therefore, you should generally access it via the
/// `terminator()` or `terminator_mut()` methods. The only
/// exception is that certain passes, such as `simplify_cfg`, swap
/// out the terminator temporarily with `None` while they continue
/// to recurse over the set of basic blocks.
pub terminator: Option<Terminator<'tcx>>,
/// If true, this block lies on an unwind path. This is used
/// during codegen where distinct kinds of basic blocks may be
/// generated (particularly for MSVC cleanup). Unwind blocks must
/// only branch to other unwind blocks.
pub is_cleanup: bool,
}
/// Information about an assertion failure.
#[derive(Clone, TyEncodable, TyDecodable, Hash, HashStable, PartialEq, PartialOrd)]
pub enum AssertKind<O> {
BoundsCheck { len: O, index: O },
Overflow(BinOp, O, O),
OverflowNeg(O),
DivisionByZero(O),
RemainderByZero(O),
ResumedAfterReturn(GeneratorKind),
ResumedAfterPanic(GeneratorKind),
}
#[derive(Clone, Debug, PartialEq, TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable)]
pub enum InlineAsmOperand<'tcx> {
In {
reg: InlineAsmRegOrRegClass,
value: Operand<'tcx>,
},
Out {
reg: InlineAsmRegOrRegClass,
late: bool,
place: Option<Place<'tcx>>,
},
InOut {
reg: InlineAsmRegOrRegClass,
late: bool,
in_value: Operand<'tcx>,
out_place: Option<Place<'tcx>>,
},
Const {
value: Box<Constant<'tcx>>,
},
SymFn {
value: Box<Constant<'tcx>>,
},
SymStatic {
def_id: DefId,
},
}
/// Type for MIR `Assert` terminator error messages.
pub type AssertMessage<'tcx> = AssertKind<Operand<'tcx>>;
pub type Successors<'a> =
iter::Chain<option::IntoIter<&'a BasicBlock>, slice::Iter<'a, BasicBlock>>;
pub type SuccessorsMut<'a> =
iter::Chain<option::IntoIter<&'a mut BasicBlock>, slice::IterMut<'a, BasicBlock>>;
impl<'tcx> BasicBlockData<'tcx> {
pub fn new(terminator: Option<Terminator<'tcx>>) -> BasicBlockData<'tcx> {
BasicBlockData { statements: vec![], terminator, is_cleanup: false }
}
/// Accessor for terminator.
///
/// Terminator may not be None after construction of the basic block is complete. This accessor
/// provides a convenience way to reach the terminator.
#[inline]
pub fn terminator(&self) -> &Terminator<'tcx> {
self.terminator.as_ref().expect("invalid terminator state")
}
#[inline]
pub fn terminator_mut(&mut self) -> &mut Terminator<'tcx> {
self.terminator.as_mut().expect("invalid terminator state")
}
pub fn retain_statements<F>(&mut self, mut f: F)
where
F: FnMut(&mut Statement<'_>) -> bool,
{
for s in &mut self.statements {
if !f(s) {
s.make_nop();
}
}
}
pub fn expand_statements<F, I>(&mut self, mut f: F)
where
F: FnMut(&mut Statement<'tcx>) -> Option<I>,
I: iter::TrustedLen<Item = Statement<'tcx>>,
{
// Gather all the iterators we'll need to splice in, and their positions.
let mut splices: Vec<(usize, I)> = vec![];
let mut extra_stmts = 0;
for (i, s) in self.statements.iter_mut().enumerate() {
if let Some(mut new_stmts) = f(s) {
if let Some(first) = new_stmts.next() {
// We can already store the first new statement.
*s = first;
// Save the other statements for optimized splicing.
let remaining = new_stmts.size_hint().0;
if remaining > 0 {
splices.push((i + 1 + extra_stmts, new_stmts));
extra_stmts += remaining;
}
} else {
s.make_nop();
}
}
}
// Splice in the new statements, from the end of the block.
// FIXME(eddyb) This could be more efficient with a "gap buffer"
// where a range of elements ("gap") is left uninitialized, with
// splicing adding new elements to the end of that gap and moving
// existing elements from before the gap to the end of the gap.
// For now, this is safe code, emulating a gap but initializing it.
let mut gap = self.statements.len()..self.statements.len() + extra_stmts;
self.statements.resize(
gap.end,
Statement { source_info: SourceInfo::outermost(DUMMY_SP), kind: StatementKind::Nop },
);
for (splice_start, new_stmts) in splices.into_iter().rev() {
let splice_end = splice_start + new_stmts.size_hint().0;
while gap.end > splice_end {
gap.start -= 1;
gap.end -= 1;
self.statements.swap(gap.start, gap.end);
}
self.statements.splice(splice_start..splice_end, new_stmts);
gap.end = splice_start;
}
}
pub fn visitable(&self, index: usize) -> &dyn MirVisitable<'tcx> {
if index < self.statements.len() { &self.statements[index] } else { &self.terminator }
}
}
impl<O> AssertKind<O> {
/// Getting a description does not require `O` to be printable, and does not
/// require allocation.
/// The caller is expected to handle `BoundsCheck` separately.
pub fn description(&self) -> &'static str {
use AssertKind::*;
match self {
Overflow(BinOp::Add, _, _) => "attempt to add with overflow",
Overflow(BinOp::Sub, _, _) => "attempt to subtract with overflow",
Overflow(BinOp::Mul, _, _) => "attempt to multiply with overflow",
Overflow(BinOp::Div, _, _) => "attempt to divide with overflow",
Overflow(BinOp::Rem, _, _) => "attempt to calculate the remainder with overflow",
OverflowNeg(_) => "attempt to negate with overflow",
Overflow(BinOp::Shr, _, _) => "attempt to shift right with overflow",
Overflow(BinOp::Shl, _, _) => "attempt to shift left with overflow",
Overflow(op, _, _) => bug!("{:?} cannot overflow", op),
DivisionByZero(_) => "attempt to divide by zero",
RemainderByZero(_) => "attempt to calculate the remainder with a divisor of zero",
ResumedAfterReturn(GeneratorKind::Gen) => "generator resumed after completion",
ResumedAfterReturn(GeneratorKind::Async(_)) => "`async fn` resumed after completion",
ResumedAfterPanic(GeneratorKind::Gen) => "generator resumed after panicking",
ResumedAfterPanic(GeneratorKind::Async(_)) => "`async fn` resumed after panicking",
BoundsCheck { .. } => bug!("Unexpected AssertKind"),
}
}
/// Format the message arguments for the `assert(cond, msg..)` terminator in MIR printing.
pub fn fmt_assert_args<W: Write>(&self, f: &mut W) -> fmt::Result
where
O: Debug,
{
use AssertKind::*;
match self {
BoundsCheck { ref len, ref index } => write!(
f,
"\"index out of bounds: the length is {{}} but the index is {{}}\", {:?}, {:?}",
len, index
),
OverflowNeg(op) => {
write!(f, "\"attempt to negate `{{}}`, which would overflow\", {:?}", op)
}
DivisionByZero(op) => write!(f, "\"attempt to divide `{{}}` by zero\", {:?}", op),
RemainderByZero(op) => write!(
f,
"\"attempt to calculate the remainder of `{{}}` with a divisor of zero\", {:?}",
op
),
Overflow(BinOp::Add, l, r) => write!(
f,
"\"attempt to compute `{{}} + {{}}`, which would overflow\", {:?}, {:?}",
l, r
),
Overflow(BinOp::Sub, l, r) => write!(
f,
"\"attempt to compute `{{}} - {{}}`, which would overflow\", {:?}, {:?}",
l, r
),
Overflow(BinOp::Mul, l, r) => write!(
f,
"\"attempt to compute `{{}} * {{}}`, which would overflow\", {:?}, {:?}",
l, r
),
Overflow(BinOp::Div, l, r) => write!(
f,
"\"attempt to compute `{{}} / {{}}`, which would overflow\", {:?}, {:?}",
l, r
),
Overflow(BinOp::Rem, l, r) => write!(
f,
"\"attempt to compute the remainder of `{{}} % {{}}`, which would overflow\", {:?}, {:?}",
l, r
),
Overflow(BinOp::Shr, _, r) => {
write!(f, "\"attempt to shift right by `{{}}`, which would overflow\", {:?}", r)
}
Overflow(BinOp::Shl, _, r) => {
write!(f, "\"attempt to shift left by `{{}}`, which would overflow\", {:?}", r)
}
_ => write!(f, "\"{}\"", self.description()),
}
}
}
impl<O: fmt::Debug> fmt::Debug for AssertKind<O> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
use AssertKind::*;
match self {
BoundsCheck { ref len, ref index } => write!(
f,
"index out of bounds: the length is {:?} but the index is {:?}",
len, index
),
OverflowNeg(op) => write!(f, "attempt to negate `{:#?}`, which would overflow", op),
DivisionByZero(op) => write!(f, "attempt to divide `{:#?}` by zero", op),
RemainderByZero(op) => write!(
f,
"attempt to calculate the remainder of `{:#?}` with a divisor of zero",
op
),
Overflow(BinOp::Add, l, r) => {
write!(f, "attempt to compute `{:#?} + {:#?}`, which would overflow", l, r)
}
Overflow(BinOp::Sub, l, r) => {
write!(f, "attempt to compute `{:#?} - {:#?}`, which would overflow", l, r)
}
Overflow(BinOp::Mul, l, r) => {
write!(f, "attempt to compute `{:#?} * {:#?}`, which would overflow", l, r)
}
Overflow(BinOp::Div, l, r) => {
write!(f, "attempt to compute `{:#?} / {:#?}`, which would overflow", l, r)
}
Overflow(BinOp::Rem, l, r) => write!(
f,
"attempt to compute the remainder of `{:#?} % {:#?}`, which would overflow",
l, r
),
Overflow(BinOp::Shr, _, r) => {
write!(f, "attempt to shift right by `{:#?}`, which would overflow", r)
}
Overflow(BinOp::Shl, _, r) => {
write!(f, "attempt to shift left by `{:#?}`, which would overflow", r)
}
_ => write!(f, "{}", self.description()),
}
}
}
///////////////////////////////////////////////////////////////////////////
// Statements
#[derive(Clone, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
pub struct Statement<'tcx> {
pub source_info: SourceInfo,
pub kind: StatementKind<'tcx>,
}
// `Statement` is used a lot. Make sure it doesn't unintentionally get bigger.
#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
static_assert_size!(Statement<'_>, 32);
impl Statement<'_> {
/// Changes a statement to a nop. This is both faster than deleting instructions and avoids
/// invalidating statement indices in `Location`s.
pub fn make_nop(&mut self) {
self.kind = StatementKind::Nop
}
/// Changes a statement to a nop and returns the original statement.
#[must_use = "If you don't need the statement, use `make_nop` instead"]
pub fn replace_nop(&mut self) -> Self {
Statement {
source_info: self.source_info,
kind: mem::replace(&mut self.kind, StatementKind::Nop),
}
}
}
#[derive(Clone, Debug, PartialEq, TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable)]
pub enum StatementKind<'tcx> {
/// Write the RHS Rvalue to the LHS Place.
Assign(Box<(Place<'tcx>, Rvalue<'tcx>)>),
/// This represents all the reading that a pattern match may do
/// (e.g., inspecting constants and discriminant values), and the
/// kind of pattern it comes from. This is in order to adapt potential
/// error messages to these specific patterns.
///
/// Note that this also is emitted for regular `let` bindings to ensure that locals that are
/// never accessed still get some sanity checks for, e.g., `let x: ! = ..;`
FakeRead(Box<(FakeReadCause, Place<'tcx>)>),
/// Write the discriminant for a variant to the enum Place.
SetDiscriminant { place: Box<Place<'tcx>>, variant_index: VariantIdx },
/// Start a live range for the storage of the local.
StorageLive(Local),
/// End the current live range for the storage of the local.
StorageDead(Local),
/// Retag references in the given place, ensuring they got fresh tags. This is
/// part of the Stacked Borrows model. These statements are currently only interpreted
/// by miri and only generated when "-Z mir-emit-retag" is passed.
/// See <https://internals.rust-lang.org/t/stacked-borrows-an-aliasing-model-for-rust/8153/>
/// for more details.
Retag(RetagKind, Box<Place<'tcx>>),
/// Encodes a user's type ascription. These need to be preserved
/// intact so that NLL can respect them. For example:
///
/// let a: T = y;
///
/// The effect of this annotation is to relate the type `T_y` of the place `y`
/// to the user-given type `T`. The effect depends on the specified variance:
///
/// - `Covariant` -- requires that `T_y <: T`
/// - `Contravariant` -- requires that `T_y :> T`
/// - `Invariant` -- requires that `T_y == T`
/// - `Bivariant` -- no effect
AscribeUserType(Box<(Place<'tcx>, UserTypeProjection)>, ty::Variance),
/// Marks the start of a "coverage region", injected with '-Zinstrument-coverage'. A
/// `Coverage` statement carries metadata about the coverage region, used to inject a coverage
/// map into the binary. If `Coverage::kind` is a `Counter`, the statement also generates
/// executable code, to increment a counter variable at runtime, each time the code region is
/// executed.
Coverage(Box<Coverage>),
/// Denotes a call to the intrinsic function copy_overlapping, where `src_dst` denotes the
/// memory being read from and written to(one field to save memory), and size
/// indicates how many bytes are being copied over.
CopyNonOverlapping(Box<CopyNonOverlapping<'tcx>>),
/// No-op. Useful for deleting instructions without affecting statement indices.
Nop,
}
impl<'tcx> StatementKind<'tcx> {
pub fn as_assign_mut(&mut self) -> Option<&mut (Place<'tcx>, Rvalue<'tcx>)> {
match self {
StatementKind::Assign(x) => Some(x),
_ => None,
}
}
pub fn as_assign(&self) -> Option<&(Place<'tcx>, Rvalue<'tcx>)> {
match self {
StatementKind::Assign(x) => Some(x),
_ => None,
}
}
}
/// Describes what kind of retag is to be performed.
#[derive(Copy, Clone, TyEncodable, TyDecodable, Debug, PartialEq, Eq, Hash, HashStable)]
pub enum RetagKind {
/// The initial retag when entering a function.
FnEntry,
/// Retag preparing for a two-phase borrow.
TwoPhase,
/// Retagging raw pointers.
Raw,
/// A "normal" retag.
Default,
}
/// The `FakeReadCause` describes the type of pattern why a FakeRead statement exists.
#[derive(Copy, Clone, TyEncodable, TyDecodable, Debug, Hash, HashStable, PartialEq)]
pub enum FakeReadCause {
/// Inject a fake read of the borrowed input at the end of each guards
/// code.
///
/// This should ensure that you cannot change the variant for an enum while
/// you are in the midst of matching on it.
ForMatchGuard,
/// `let x: !; match x {}` doesn't generate any read of x so we need to
/// generate a read of x to check that it is initialized and safe.
///
/// If a closure pattern matches a Place starting with an Upvar, then we introduce a
/// FakeRead for that Place outside the closure, in such a case this option would be
/// Some(closure_def_id).
/// Otherwise, the value of the optional DefId will be None.
ForMatchedPlace(Option<DefId>),
/// A fake read of the RefWithinGuard version of a bind-by-value variable
/// in a match guard to ensure that it's value hasn't change by the time
/// we create the OutsideGuard version.
ForGuardBinding,
/// Officially, the semantics of
///
/// `let pattern = <expr>;`
///
/// is that `<expr>` is evaluated into a temporary and then this temporary is
/// into the pattern.
///
/// However, if we see the simple pattern `let var = <expr>`, we optimize this to
/// evaluate `<expr>` directly into the variable `var`. This is mostly unobservable,
/// but in some cases it can affect the borrow checker, as in #53695.
/// Therefore, we insert a "fake read" here to ensure that we get
/// appropriate errors.
///
/// If a closure pattern matches a Place starting with an Upvar, then we introduce a
/// FakeRead for that Place outside the closure, in such a case this option would be
/// Some(closure_def_id).
/// Otherwise, the value of the optional DefId will be None.
ForLet(Option<DefId>),
/// If we have an index expression like
///
/// (*x)[1][{ x = y; 4}]
///
/// then the first bounds check is invalidated when we evaluate the second
/// index expression. Thus we create a fake borrow of `x` across the second
/// indexer, which will cause a borrow check error.
ForIndex,
}
impl Debug for Statement<'_> {
fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
use self::StatementKind::*;
match self.kind {
Assign(box (ref place, ref rv)) => write!(fmt, "{:?} = {:?}", place, rv),
FakeRead(box (ref cause, ref place)) => {
write!(fmt, "FakeRead({:?}, {:?})", cause, place)
}
Retag(ref kind, ref place) => write!(
fmt,
"Retag({}{:?})",
match kind {
RetagKind::FnEntry => "[fn entry] ",
RetagKind::TwoPhase => "[2phase] ",
RetagKind::Raw => "[raw] ",
RetagKind::Default => "",
},
place,
),
StorageLive(ref place) => write!(fmt, "StorageLive({:?})", place),
StorageDead(ref place) => write!(fmt, "StorageDead({:?})", place),
SetDiscriminant { ref place, variant_index } => {
write!(fmt, "discriminant({:?}) = {:?}", place, variant_index)
}
AscribeUserType(box (ref place, ref c_ty), ref variance) => {
write!(fmt, "AscribeUserType({:?}, {:?}, {:?})", place, variance, c_ty)
}
Coverage(box self::Coverage { ref kind, code_region: Some(ref rgn) }) => {
write!(fmt, "Coverage::{:?} for {:?}", kind, rgn)
}
Coverage(box ref coverage) => write!(fmt, "Coverage::{:?}", coverage.kind),
CopyNonOverlapping(box crate::mir::CopyNonOverlapping {
ref src,
ref dst,
ref count,
}) => {
write!(fmt, "copy_nonoverlapping(src={:?}, dst={:?}, count={:?})", src, dst, count)
}
Nop => write!(fmt, "nop"),
}
}
}
#[derive(Clone, Debug, PartialEq, TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable)]
pub struct Coverage {
pub kind: CoverageKind,
pub code_region: Option<CodeRegion>,
}
#[derive(Clone, Debug, PartialEq, TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable)]
pub struct CopyNonOverlapping<'tcx> {
pub src: Operand<'tcx>,
pub dst: Operand<'tcx>,
/// Number of elements to copy from src to dest, not bytes.
pub count: Operand<'tcx>,
}
///////////////////////////////////////////////////////////////////////////
// Places
/// A path to a value; something that can be evaluated without
/// changing or disturbing program state.
#[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, HashStable)]
pub struct Place<'tcx> {
pub local: Local,
/// projection out of a place (access a field, deref a pointer, etc)
pub projection: &'tcx List<PlaceElem<'tcx>>,
}
#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
static_assert_size!(Place<'_>, 16);
#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
#[derive(TyEncodable, TyDecodable, HashStable)]
pub enum ProjectionElem<V, T> {
Deref,
Field(Field, T),
Index(V),
/// These indices are generated by slice patterns. Easiest to explain
/// by example:
///
/// ```
/// [X, _, .._, _, _] => { offset: 0, min_length: 4, from_end: false },
/// [_, X, .._, _, _] => { offset: 1, min_length: 4, from_end: false },
/// [_, _, .._, X, _] => { offset: 2, min_length: 4, from_end: true },
/// [_, _, .._, _, X] => { offset: 1, min_length: 4, from_end: true },
/// ```
ConstantIndex {
/// index or -index (in Python terms), depending on from_end
offset: u64,
/// The thing being indexed must be at least this long. For arrays this
/// is always the exact length.
min_length: u64,
/// Counting backwards from end? This is always false when indexing an
/// array.
from_end: bool,
},
/// These indices are generated by slice patterns.
///
/// If `from_end` is true `slice[from..slice.len() - to]`.
/// Otherwise `array[from..to]`.
Subslice {
from: u64,
to: u64,
/// Whether `to` counts from the start or end of the array/slice.
/// For `PlaceElem`s this is `true` if and only if the base is a slice.
/// For `ProjectionKind`, this can also be `true` for arrays.
from_end: bool,
},
/// "Downcast" to a variant of an ADT. Currently, we only introduce
/// this for ADTs with more than one variant. It may be better to
/// just introduce it always, or always for enums.
///
/// The included Symbol is the name of the variant, used for printing MIR.
Downcast(Option<Symbol>, VariantIdx),
}
impl<V, T> ProjectionElem<V, T> {
/// Returns `true` if the target of this projection may refer to a different region of memory
/// than the base.
fn is_indirect(&self) -> bool {
match self {
Self::Deref => true,
Self::Field(_, _)
| Self::Index(_)
| Self::ConstantIndex { .. }
| Self::Subslice { .. }
| Self::Downcast(_, _) => false,
}
}
/// Returns `true` if this is a `Downcast` projection with the given `VariantIdx`.
pub fn is_downcast_to(&self, v: VariantIdx) -> bool {
matches!(*self, Self::Downcast(_, x) if x == v)
}
/// Returns `true` if this is a `Field` projection with the given index.
pub fn is_field_to(&self, f: Field) -> bool {
matches!(*self, Self::Field(x, _) if x == f)
}
}
/// Alias for projections as they appear in places, where the base is a place
/// and the index is a local.
pub type PlaceElem<'tcx> = ProjectionElem<Local, Ty<'tcx>>;
// At least on 64 bit systems, `PlaceElem` should not be larger than two pointers.
#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
static_assert_size!(PlaceElem<'_>, 24);
/// Alias for projections as they appear in `UserTypeProjection`, where we
/// need neither the `V` parameter for `Index` nor the `T` for `Field`.
pub type ProjectionKind = ProjectionElem<(), ()>;
rustc_index::newtype_index! {
pub struct Field {
derive [HashStable]
DEBUG_FORMAT = "field[{}]"
}
}
#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct PlaceRef<'tcx> {
pub local: Local,
pub projection: &'tcx [PlaceElem<'tcx>],
}
impl<'tcx> Place<'tcx> {
// FIXME change this to a const fn by also making List::empty a const fn.
pub fn return_place() -> Place<'tcx> {
Place { local: RETURN_PLACE, projection: List::empty() }
}
/// Returns `true` if this `Place` contains a `Deref` projection.
///
/// If `Place::is_indirect` returns false, the caller knows that the `Place` refers to the
/// same region of memory as its base.
pub fn is_indirect(&self) -> bool {
self.projection.iter().any(|elem| elem.is_indirect())
}
/// Finds the innermost `Local` from this `Place`, *if* it is either a local itself or
/// a single deref of a local.
#[inline(always)]
pub fn local_or_deref_local(&self) -> Option<Local> {
self.as_ref().local_or_deref_local()
}
/// If this place represents a local variable like `_X` with no
/// projections, return `Some(_X)`.
#[inline(always)]
pub fn as_local(&self) -> Option<Local> {
self.as_ref().as_local()
}
#[inline]
pub fn as_ref(&self) -> PlaceRef<'tcx> {
PlaceRef { local: self.local, projection: &self.projection }
}
/// Iterate over the projections in evaluation order, i.e., the first element is the base with
/// its projection and then subsequently more projections are added.
/// As a concrete example, given the place a.b.c, this would yield:
/// - (a, .b)
/// - (a.b, .c)
///
/// Given a place without projections, the iterator is empty.
#[inline]
pub fn iter_projections(
self,
) -> impl Iterator<Item = (PlaceRef<'tcx>, PlaceElem<'tcx>)> + DoubleEndedIterator {
self.projection.iter().enumerate().map(move |(i, proj)| {
let base = PlaceRef { local: self.local, projection: &self.projection[..i] };
(base, proj)
})
}
}
impl From<Local> for Place<'_> {
fn from(local: Local) -> Self {
Place { local, projection: List::empty() }
}
}
impl<'tcx> PlaceRef<'tcx> {
/// Finds the innermost `Local` from this `Place`, *if* it is either a local itself or
/// a single deref of a local.
pub fn local_or_deref_local(&self) -> Option<Local> {
match *self {
PlaceRef { local, projection: [] }
| PlaceRef { local, projection: [ProjectionElem::Deref] } => Some(local),
_ => None,
}
}
/// If this place represents a local variable like `_X` with no
/// projections, return `Some(_X)`.
#[inline]
pub fn as_local(&self) -> Option<Local> {
match *self {
PlaceRef { local, projection: [] } => Some(local),
_ => None,
}
}
#[inline]
pub fn last_projection(&self) -> Option<(PlaceRef<'tcx>, PlaceElem<'tcx>)> {
if let &[ref proj_base @ .., elem] = self.projection {
Some((PlaceRef { local: self.local, projection: proj_base }, elem))
} else {
None
}
}
}
impl Debug for Place<'_> {
fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
for elem in self.projection.iter().rev() {
match elem {
ProjectionElem::Downcast(_, _) | ProjectionElem::Field(_, _) => {
write!(fmt, "(").unwrap();
}
ProjectionElem::Deref => {
write!(fmt, "(*").unwrap();
}
ProjectionElem::Index(_)
| ProjectionElem::ConstantIndex { .. }
| ProjectionElem::Subslice { .. } => {}
}
}
write!(fmt, "{:?}", self.local)?;
for elem in self.projection.iter() {
match elem {
ProjectionElem::Downcast(Some(name), _index) => {
write!(fmt, " as {})", name)?;
}
ProjectionElem::Downcast(None, index) => {
write!(fmt, " as variant#{:?})", index)?;
}
ProjectionElem::Deref => {
write!(fmt, ")")?;
}
ProjectionElem::Field(field, ty) => {
write!(fmt, ".{:?}: {:?})", field.index(), ty)?;
}
ProjectionElem::Index(ref index) => {
write!(fmt, "[{:?}]", index)?;
}
ProjectionElem::ConstantIndex { offset, min_length, from_end: false } => {
write!(fmt, "[{:?} of {:?}]", offset, min_length)?;
}
ProjectionElem::ConstantIndex { offset, min_length, from_end: true } => {
write!(fmt, "[-{:?} of {:?}]", offset, min_length)?;
}
ProjectionElem::Subslice { from, to, from_end: true } if to == 0 => {
write!(fmt, "[{:?}:]", from)?;
}
ProjectionElem::Subslice { from, to, from_end: true } if from == 0 => {
write!(fmt, "[:-{:?}]", to)?;
}
ProjectionElem::Subslice { from, to, from_end: true } => {
write!(fmt, "[{:?}:-{:?}]", from, to)?;
}
ProjectionElem::Subslice { from, to, from_end: false } => {
write!(fmt, "[{:?}..{:?}]", from, to)?;
}
}
}
Ok(())
}
}
///////////////////////////////////////////////////////////////////////////
// Scopes
rustc_index::newtype_index! {
pub struct SourceScope {
derive [HashStable]
DEBUG_FORMAT = "scope[{}]",
const OUTERMOST_SOURCE_SCOPE = 0,
}
}
impl SourceScope {
/// Finds the original HirId this MIR item came from.
/// This is necessary after MIR optimizations, as otherwise we get a HirId
/// from the function that was inlined instead of the function call site.
pub fn lint_root<'tcx>(
self,
source_scopes: &IndexVec<SourceScope, SourceScopeData<'tcx>>,
) -> Option<HirId> {
let mut data = &source_scopes[self];
// FIXME(oli-obk): we should be able to just walk the `inlined_parent_scope`, but it
// does not work as I thought it would. Needs more investigation and documentation.
while data.inlined.is_some() {
trace!(?data);
data = &source_scopes[data.parent_scope.unwrap()];
}
trace!(?data);
match &data.local_data {
ClearCrossCrate::Set(data) => Some(data.lint_root),
ClearCrossCrate::Clear => None,
}
}
}
#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
pub struct SourceScopeData<'tcx> {
pub span: Span,
pub parent_scope: Option<SourceScope>,
/// Whether this scope is the root of a scope tree of another body,
/// inlined into this body by the MIR inliner.
/// `ty::Instance` is the callee, and the `Span` is the call site.
pub inlined: Option<(ty::Instance<'tcx>, Span)>,
/// Nearest (transitive) parent scope (if any) which is inlined.
/// This is an optimization over walking up `parent_scope`
/// until a scope with `inlined: Some(...)` is found.
pub inlined_parent_scope: Option<SourceScope>,
/// Crate-local information for this source scope, that can't (and
/// needn't) be tracked across crates.
pub local_data: ClearCrossCrate<SourceScopeLocalData>,
}
#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
pub struct SourceScopeLocalData {
/// An `HirId` with lint levels equivalent to this scope's lint levels.
pub lint_root: hir::HirId,
/// The unsafe block that contains this node.
pub safety: Safety,
}
///////////////////////////////////////////////////////////////////////////
// Operands
/// These are values that can appear inside an rvalue. They are intentionally
/// limited to prevent rvalues from being nested in one another.
#[derive(Clone, PartialEq, TyEncodable, TyDecodable, Hash, HashStable)]
pub enum Operand<'tcx> {
/// Copy: The value must be available for use afterwards.
///
/// This implies that the type of the place must be `Copy`; this is true
/// by construction during build, but also checked by the MIR type checker.
Copy(Place<'tcx>),
/// Move: The value (including old borrows of it) will not be used again.
///
/// Safe for values of all types (modulo future developments towards `?Move`).
/// Correct usage patterns are enforced by the borrow checker for safe code.
/// `Copy` may be converted to `Move` to enable "last-use" optimizations.
Move(Place<'tcx>),
/// Synthesizes a constant value.
Constant(Box<Constant<'tcx>>),
}
#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
static_assert_size!(Operand<'_>, 24);
impl<'tcx> Debug for Operand<'tcx> {
fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
use self::Operand::*;
match *self {
Constant(ref a) => write!(fmt, "{:?}", a),
Copy(ref place) => write!(fmt, "{:?}", place),
Move(ref place) => write!(fmt, "move {:?}", place),
}
}
}
impl<'tcx> Operand<'tcx> {
/// Convenience helper to make a constant that refers to the fn
/// with given `DefId` and substs. Since this is used to synthesize
/// MIR, assumes `user_ty` is None.
pub fn function_handle(
tcx: TyCtxt<'tcx>,
def_id: DefId,
substs: SubstsRef<'tcx>,
span: Span,
) -> Self {
let ty = tcx.type_of(def_id).subst(tcx, substs);
Operand::Constant(Box::new(Constant {
span,
user_ty: None,
literal: ConstantKind::Ty(ty::Const::zero_sized(tcx, ty)),
}))
}
pub fn is_move(&self) -> bool {
matches!(self, Operand::Move(..))
}
/// Convenience helper to make a literal-like constant from a given scalar value.
/// Since this is used to synthesize MIR, assumes `user_ty` is None.
pub fn const_from_scalar(
tcx: TyCtxt<'tcx>,
ty: Ty<'tcx>,
val: Scalar,
span: Span,
) -> Operand<'tcx> {
debug_assert!({
let param_env_and_ty = ty::ParamEnv::empty().and(ty);
let type_size = tcx
.layout_of(param_env_and_ty)
.unwrap_or_else(|e| panic!("could not compute layout for {:?}: {:?}", ty, e))
.size;
let scalar_size = match val {
Scalar::Int(int) => int.size(),
_ => panic!("Invalid scalar type {:?}", val),
};
scalar_size == type_size
});
Operand::Constant(Box::new(Constant {
span,
user_ty: None,
literal: ConstantKind::Val(ConstValue::Scalar(val), ty),
}))
}
pub fn to_copy(&self) -> Self {
match *self {
Operand::Copy(_) | Operand::Constant(_) => self.clone(),
Operand::Move(place) => Operand::Copy(place),
}
}
/// Returns the `Place` that is the target of this `Operand`, or `None` if this `Operand` is a
/// constant.
pub fn place(&self) -> Option<Place<'tcx>> {
match self {
Operand::Copy(place) | Operand::Move(place) => Some(*place),
Operand::Constant(_) => None,
}
}
/// Returns the `Constant` that is the target of this `Operand`, or `None` if this `Operand` is a
/// place.
pub fn constant(&self) -> Option<&Constant<'tcx>> {
match self {
Operand::Constant(x) => Some(&**x),
Operand::Copy(_) | Operand::Move(_) => None,
}
}
}
///////////////////////////////////////////////////////////////////////////
/// Rvalues
#[derive(Clone, TyEncodable, TyDecodable, Hash, HashStable, PartialEq)]
pub enum Rvalue<'tcx> {
/// x (either a move or copy, depending on type of x)
Use(Operand<'tcx>),
/// [x; 32]
Repeat(Operand<'tcx>, &'tcx ty::Const<'tcx>),
/// &x or &mut x
Ref(Region<'tcx>, BorrowKind, Place<'tcx>),
/// Accessing a thread local static. This is inherently a runtime operation, even if llvm
/// treats it as an access to a static. This `Rvalue` yields a reference to the thread local
/// static.
ThreadLocalRef(DefId),
/// Create a raw pointer to the given place
/// Can be generated by raw address of expressions (`&raw const x`),
/// or when casting a reference to a raw pointer.
AddressOf(Mutability, Place<'tcx>),
/// length of a `[X]` or `[X;n]` value
Len(Place<'tcx>),
Cast(CastKind, Operand<'tcx>, Ty<'tcx>),
BinaryOp(BinOp, Box<(Operand<'tcx>, Operand<'tcx>)>),
CheckedBinaryOp(BinOp, Box<(Operand<'tcx>, Operand<'tcx>)>),
NullaryOp(NullOp, Ty<'tcx>),
UnaryOp(UnOp, Operand<'tcx>),
/// Read the discriminant of an ADT.
///
/// Undefined (i.e., no effort is made to make it defined, but there’s no reason why it cannot
/// be defined to return, say, a 0) if ADT is not an enum.
Discriminant(Place<'tcx>),
/// Creates an aggregate value, like a tuple or struct. This is
/// only needed because we want to distinguish `dest = Foo { x:
/// ..., y: ... }` from `dest.x = ...; dest.y = ...;` in the case
/// that `Foo` has a destructor. These rvalues can be optimized
/// away after type-checking and before lowering.
Aggregate(Box<AggregateKind<'tcx>>, Vec<Operand<'tcx>>),
/// Transmutes a `*mut u8` into shallow-initialized `Box<T>`.
///
/// This is different a normal transmute because dataflow analysis will treat the box
/// as initialized but its content as uninitialized.
ShallowInitBox(Operand<'tcx>, Ty<'tcx>),
}
#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
static_assert_size!(Rvalue<'_>, 40);
#[derive(Clone, Copy, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
pub enum CastKind {
Misc,
Pointer(PointerCast),
}
#[derive(Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
pub enum AggregateKind<'tcx> {
/// The type is of the element
Array(Ty<'tcx>),
Tuple,
/// The second field is the variant index. It's equal to 0 for struct
/// and union expressions. The fourth field is
/// active field number and is present only for union expressions
/// -- e.g., for a union expression `SomeUnion { c: .. }`, the
/// active field index would identity the field `c`
Adt(DefId, VariantIdx, SubstsRef<'tcx>, Option<UserTypeAnnotationIndex>, Option<usize>),
Closure(DefId, SubstsRef<'tcx>),
Generator(DefId, SubstsRef<'tcx>, hir::Movability),
}
#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
static_assert_size!(AggregateKind<'_>, 48);
#[derive(Copy, Clone, Debug, PartialEq, PartialOrd, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
pub enum BinOp {
/// The `+` operator (addition)
Add,
/// The `-` operator (subtraction)
Sub,
/// The `*` operator (multiplication)
Mul,
/// The `/` operator (division)
///
/// Division by zero is UB.
Div,
/// The `%` operator (modulus)
///
/// Using zero as the modulus (second operand) is UB.
Rem,
/// The `^` operator (bitwise xor)
BitXor,
/// The `&` operator (bitwise and)
BitAnd,
/// The `|` operator (bitwise or)
BitOr,
/// The `<<` operator (shift left)
///
/// The offset is truncated to the size of the first operand before shifting.
Shl,
/// The `>>` operator (shift right)
///
/// The offset is truncated to the size of the first operand before shifting.
Shr,
/// The `==` operator (equality)
Eq,
/// The `<` operator (less than)
Lt,
/// The `<=` operator (less than or equal to)
Le,
/// The `!=` operator (not equal to)
Ne,
/// The `>=` operator (greater than or equal to)
Ge,
/// The `>` operator (greater than)
Gt,
/// The `ptr.offset` operator
Offset,
}
impl BinOp {
pub fn is_checkable(self) -> bool {
use self::BinOp::*;
matches!(self, Add | Sub | Mul | Shl | Shr)
}
}
#[derive(Copy, Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
pub enum NullOp {
/// Returns the size of a value of that type
SizeOf,
/// Returns the minimum alignment of a type
AlignOf,
}
#[derive(Copy, Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
pub enum UnOp {
/// The `!` operator for logical inversion
Not,
/// The `-` operator for negation
Neg,
}
impl<'tcx> Debug for Rvalue<'tcx> {
fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
use self::Rvalue::*;
match *self {
Use(ref place) => write!(fmt, "{:?}", place),
Repeat(ref a, ref b) => {
write!(fmt, "[{:?}; ", a)?;
pretty_print_const(b, fmt, false)?;
write!(fmt, "]")
}
Len(ref a) => write!(fmt, "Len({:?})", a),
Cast(ref kind, ref place, ref ty) => {
write!(fmt, "{:?} as {:?} ({:?})", place, ty, kind)
}
BinaryOp(ref op, box (ref a, ref b)) => write!(fmt, "{:?}({:?}, {:?})", op, a, b),
CheckedBinaryOp(ref op, box (ref a, ref b)) => {
write!(fmt, "Checked{:?}({:?}, {:?})", op, a, b)
}
UnaryOp(ref op, ref a) => write!(fmt, "{:?}({:?})", op, a),
Discriminant(ref place) => write!(fmt, "discriminant({:?})", place),
NullaryOp(ref op, ref t) => write!(fmt, "{:?}({:?})", op, t),
ThreadLocalRef(did) => ty::tls::with(|tcx| {
let muta = tcx.static_mutability(did).unwrap().prefix_str();
write!(fmt, "&/*tls*/ {}{}", muta, tcx.def_path_str(did))
}),
Ref(region, borrow_kind, ref place) => {
let kind_str = match borrow_kind {
BorrowKind::Shared => "",
BorrowKind::Shallow => "shallow ",
BorrowKind::Mut { .. } | BorrowKind::Unique => "mut ",
};
// When printing regions, add trailing space if necessary.
let print_region = ty::tls::with(|tcx| {
tcx.sess.verbose() || tcx.sess.opts.debugging_opts.identify_regions
});
let region = if print_region {
let mut region = region.to_string();
if !region.is_empty() {
region.push(' ');
}
region
} else {
// Do not even print 'static
String::new()
};
write!(fmt, "&{}{}{:?}", region, kind_str, place)
}
AddressOf(mutability, ref place) => {
let kind_str = match mutability {
Mutability::Mut => "mut",
Mutability::Not => "const",
};
write!(fmt, "&raw {} {:?}", kind_str, place)
}
Aggregate(ref kind, ref places) => {
let fmt_tuple = |fmt: &mut Formatter<'_>, name: &str| {
let mut tuple_fmt = fmt.debug_tuple(name);
for place in places {
tuple_fmt.field(place);
}
tuple_fmt.finish()
};
match **kind {
AggregateKind::Array(_) => write!(fmt, "{:?}", places),
AggregateKind::Tuple => {
if places.is_empty() {
write!(fmt, "()")
} else {
fmt_tuple(fmt, "")
}
}
AggregateKind::Adt(adt_did, variant, substs, _user_ty, _) => {
ty::tls::with(|tcx| {
let mut name = String::new();
let variant_def = &tcx.adt_def(adt_did).variants[variant];
let substs = tcx.lift(substs).expect("could not lift for printing");
FmtPrinter::new(tcx, &mut name, Namespace::ValueNS)
.print_def_path(variant_def.def_id, substs)?;
match variant_def.ctor_kind {
CtorKind::Const => fmt.write_str(&name),
CtorKind::Fn => fmt_tuple(fmt, &name),
CtorKind::Fictive => {
let mut struct_fmt = fmt.debug_struct(&name);
for (field, place) in iter::zip(&variant_def.fields, places) {
struct_fmt.field(field.name.as_str(), place);
}
struct_fmt.finish()
}
}
})
}
AggregateKind::Closure(def_id, substs) => ty::tls::with(|tcx| {
if let Some(def_id) = def_id.as_local() {
let name = if tcx.sess.opts.debugging_opts.span_free_formats {
let substs = tcx.lift(substs).unwrap();
format!(
"[closure@{}]",
tcx.def_path_str_with_substs(def_id.to_def_id(), substs),
)
} else {
let span = tcx.def_span(def_id);
format!(
"[closure@{}]",
tcx.sess.source_map().span_to_diagnostic_string(span)
)
};
let mut struct_fmt = fmt.debug_struct(&name);
// FIXME(project-rfc-2229#48): This should be a list of capture names/places
if let Some(upvars) = tcx.upvars_mentioned(def_id) {
for (&var_id, place) in iter::zip(upvars.keys(), places) {
let var_name = tcx.hir().name(var_id);
struct_fmt.field(var_name.as_str(), place);
}
}
struct_fmt.finish()
} else {
write!(fmt, "[closure]")
}
}),
AggregateKind::Generator(def_id, _, _) => ty::tls::with(|tcx| {
if let Some(def_id) = def_id.as_local() {
let name = format!("[generator@{:?}]", tcx.def_span(def_id));
let mut struct_fmt = fmt.debug_struct(&name);
// FIXME(project-rfc-2229#48): This should be a list of capture names/places
if let Some(upvars) = tcx.upvars_mentioned(def_id) {
for (&var_id, place) in iter::zip(upvars.keys(), places) {
let var_name = tcx.hir().name(var_id);
struct_fmt.field(var_name.as_str(), place);
}
}
struct_fmt.finish()
} else {
write!(fmt, "[generator]")
}
}),
}
}
ShallowInitBox(ref place, ref ty) => {
write!(fmt, "ShallowInitBox({:?}, {:?})", place, ty)
}
}
}
}
///////////////////////////////////////////////////////////////////////////
/// Constants
///
/// Two constants are equal if they are the same constant. Note that
/// this does not necessarily mean that they are `==` in Rust. In
/// particular, one must be wary of `NaN`!
#[derive(Clone, Copy, PartialEq, TyEncodable, TyDecodable, Hash, HashStable)]
pub struct Constant<'tcx> {
pub span: Span,
/// Optional user-given type: for something like
/// `collect::<Vec<_>>`, this would be present and would
/// indicate that `Vec<_>` was explicitly specified.
///
/// Needed for NLL to impose user-given type constraints.
pub user_ty: Option<UserTypeAnnotationIndex>,
pub literal: ConstantKind<'tcx>,
}
#[derive(Clone, Copy, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable, Debug)]
#[derive(Lift)]
pub enum ConstantKind<'tcx> {
/// This constant came from the type system
Ty(&'tcx ty::Const<'tcx>),
/// This constant cannot go back into the type system, as it represents
/// something the type system cannot handle (e.g. pointers).
Val(interpret::ConstValue<'tcx>, Ty<'tcx>),
}
impl<'tcx> Constant<'tcx> {
pub fn check_static_ptr(&self, tcx: TyCtxt<'_>) -> Option<DefId> {
match self.literal.const_for_ty()?.val.try_to_scalar() {
Some(Scalar::Ptr(ptr, _size)) => match tcx.global_alloc(ptr.provenance) {
GlobalAlloc::Static(def_id) => {
assert!(!tcx.is_thread_local_static(def_id));
Some(def_id)
}
_ => None,
},
_ => None,
}
}
#[inline]
pub fn ty(&self) -> Ty<'tcx> {
self.literal.ty()
}
}
impl<'tcx> From<&'tcx ty::Const<'tcx>> for ConstantKind<'tcx> {
#[inline]
fn from(ct: &'tcx ty::Const<'tcx>) -> Self {
Self::Ty(ct)
}
}
impl<'tcx> ConstantKind<'tcx> {
/// Returns `None` if the constant is not trivially safe for use in the type system.
pub fn const_for_ty(&self) -> Option<&'tcx ty::Const<'tcx>> {
match self {
ConstantKind::Ty(c) => Some(c),
ConstantKind::Val(..) => None,
}
}
pub fn ty(&self) -> Ty<'tcx> {
match self {
ConstantKind::Ty(c) => c.ty,
ConstantKind::Val(_, ty) => ty,
}
}
#[inline]
pub fn try_to_value(self) -> Option<interpret::ConstValue<'tcx>> {
match self {
ConstantKind::Ty(c) => c.val.try_to_value(),
ConstantKind::Val(val, _) => Some(val),
}
}
#[inline]
pub fn try_to_scalar(self) -> Option<Scalar> {
self.try_to_value()?.try_to_scalar()
}
#[inline]
pub fn try_to_scalar_int(self) -> Option<ScalarInt> {
Some(self.try_to_value()?.try_to_scalar()?.assert_int())
}
#[inline]
pub fn try_to_bits(self, size: Size) -> Option<u128> {
self.try_to_scalar_int()?.to_bits(size).ok()
}
#[inline]
pub fn try_to_bool(self) -> Option<bool> {
self.try_to_scalar_int()?.try_into().ok()
}
#[inline]
pub fn try_eval_bits(
&self,
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
ty: Ty<'tcx>,
) -> Option<u128> {
match self {
Self::Ty(ct) => ct.try_eval_bits(tcx, param_env, ty),
Self::Val(val, t) => {
assert_eq!(*t, ty);
let size =
tcx.layout_of(param_env.with_reveal_all_normalized(tcx).and(ty)).ok()?.size;
val.try_to_bits(size)
}
}
}
#[inline]
pub fn try_eval_bool(&self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Option<bool> {
match self {
Self::Ty(ct) => ct.try_eval_bool(tcx, param_env),
Self::Val(val, _) => val.try_to_bool(),
}
}
#[inline]
pub fn try_eval_usize(&self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Option<u64> {
match self {
Self::Ty(ct) => ct.try_eval_usize(tcx, param_env),
Self::Val(val, _) => val.try_to_machine_usize(tcx),
}
}
}
/// A collection of projections into user types.
///
/// They are projections because a binding can occur a part of a
/// parent pattern that has been ascribed a type.
///
/// Its a collection because there can be multiple type ascriptions on
/// the path from the root of the pattern down to the binding itself.
///
/// An example:
///
/// ```rust
/// struct S<'a>((i32, &'a str), String);
/// let S((_, w): (i32, &'static str), _): S = ...;
/// // ------ ^^^^^^^^^^^^^^^^^^^ (1)
/// // --------------------------------- ^ (2)
/// ```
///
/// The highlights labelled `(1)` show the subpattern `(_, w)` being
/// ascribed the type `(i32, &'static str)`.
///
/// The highlights labelled `(2)` show the whole pattern being
/// ascribed the type `S`.
///
/// In this example, when we descend to `w`, we will have built up the
/// following two projected types:
///
/// * base: `S`, projection: `(base.0).1`
/// * base: `(i32, &'static str)`, projection: `base.1`
///
/// The first will lead to the constraint `w: &'1 str` (for some
/// inferred region `'1`). The second will lead to the constraint `w:
/// &'static str`.
#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
pub struct UserTypeProjections {
pub contents: Vec<(UserTypeProjection, Span)>,
}
impl<'tcx> UserTypeProjections {
pub fn none() -> Self {
UserTypeProjections { contents: vec![] }
}
pub fn is_empty(&self) -> bool {
self.contents.is_empty()
}
pub fn projections_and_spans(
&self,
) -> impl Iterator<Item = &(UserTypeProjection, Span)> + ExactSizeIterator {
self.contents.iter()
}
pub fn projections(&self) -> impl Iterator<Item = &UserTypeProjection> + ExactSizeIterator {
self.contents.iter().map(|&(ref user_type, _span)| user_type)
}
pub fn push_projection(mut self, user_ty: &UserTypeProjection, span: Span) -> Self {
self.contents.push((user_ty.clone(), span));
self
}
fn map_projections(
mut self,
mut f: impl FnMut(UserTypeProjection) -> UserTypeProjection,
) -> Self {
self.contents = self.contents.into_iter().map(|(proj, span)| (f(proj), span)).collect();
self
}
pub fn index(self) -> Self {
self.map_projections(|pat_ty_proj| pat_ty_proj.index())
}
pub fn subslice(self, from: u64, to: u64) -> Self {
self.map_projections(|pat_ty_proj| pat_ty_proj.subslice(from, to))
}
pub fn deref(self) -> Self {
self.map_projections(|pat_ty_proj| pat_ty_proj.deref())
}
pub fn leaf(self, field: Field) -> Self {
self.map_projections(|pat_ty_proj| pat_ty_proj.leaf(field))
}
pub fn variant(self, adt_def: &'tcx AdtDef, variant_index: VariantIdx, field: Field) -> Self {
self.map_projections(|pat_ty_proj| pat_ty_proj.variant(adt_def, variant_index, field))
}
}
/// Encodes the effect of a user-supplied type annotation on the
/// subcomponents of a pattern. The effect is determined by applying the
/// given list of proejctions to some underlying base type. Often,
/// the projection element list `projs` is empty, in which case this
/// directly encodes a type in `base`. But in the case of complex patterns with
/// subpatterns and bindings, we want to apply only a *part* of the type to a variable,
/// in which case the `projs` vector is used.
///
/// Examples:
///
/// * `let x: T = ...` -- here, the `projs` vector is empty.
///
/// * `let (x, _): T = ...` -- here, the `projs` vector would contain
/// `field[0]` (aka `.0`), indicating that the type of `s` is
/// determined by finding the type of the `.0` field from `T`.
#[derive(Clone, Debug, TyEncodable, TyDecodable, Hash, HashStable, PartialEq)]
pub struct UserTypeProjection {
pub base: UserTypeAnnotationIndex,
pub projs: Vec<ProjectionKind>,
}
impl Copy for ProjectionKind {}
impl UserTypeProjection {
pub(crate) fn index(mut self) -> Self {
self.projs.push(ProjectionElem::Index(()));
self
}
pub(crate) fn subslice(mut self, from: u64, to: u64) -> Self {
self.projs.push(ProjectionElem::Subslice { from, to, from_end: true });
self
}
pub(crate) fn deref(mut self) -> Self {
self.projs.push(ProjectionElem::Deref);
self
}
pub(crate) fn leaf(mut self, field: Field) -> Self {
self.projs.push(ProjectionElem::Field(field, ()));
self
}
pub(crate) fn variant(
mut self,
adt_def: &AdtDef,
variant_index: VariantIdx,
field: Field,
) -> Self {
self.projs.push(ProjectionElem::Downcast(
Some(adt_def.variants[variant_index].name),
variant_index,
));
self.projs.push(ProjectionElem::Field(field, ()));
self
}
}
TrivialTypeFoldableAndLiftImpls! { ProjectionKind, }
impl<'tcx> TypeFoldable<'tcx> for UserTypeProjection {
fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
self,
folder: &mut F,
) -> Result<Self, F::Error> {
Ok(UserTypeProjection {
base: self.base.try_fold_with(folder)?,
projs: self.projs.try_fold_with(folder)?,
})
}
fn super_visit_with<Vs: TypeVisitor<'tcx>>(
&self,
visitor: &mut Vs,
) -> ControlFlow<Vs::BreakTy> {
self.base.visit_with(visitor)
// Note: there's nothing in `self.proj` to visit.
}
}
rustc_index::newtype_index! {
pub struct Promoted {
derive [HashStable]
DEBUG_FORMAT = "promoted[{}]"
}
}
impl<'tcx> Debug for Constant<'tcx> {
fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
write!(fmt, "{}", self)
}
}
impl<'tcx> Display for Constant<'tcx> {
fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
match self.ty().kind() {
ty::FnDef(..) => {}
_ => write!(fmt, "const ")?,
}
Display::fmt(&self.literal, fmt)
}
}
impl<'tcx> Display for ConstantKind<'tcx> {
fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
match *self {
ConstantKind::Ty(c) => pretty_print_const(c, fmt, true),
ConstantKind::Val(val, ty) => pretty_print_const_value(val, ty, fmt, true),
}
}
}
fn pretty_print_const<'tcx>(
c: &ty::Const<'tcx>,
fmt: &mut Formatter<'_>,
print_types: bool,
) -> fmt::Result {
use crate::ty::print::PrettyPrinter;
ty::tls::with(|tcx| {
let literal = tcx.lift(c).unwrap();
let mut cx = FmtPrinter::new(tcx, fmt, Namespace::ValueNS);
cx.print_alloc_ids = true;
cx.pretty_print_const(literal, print_types)?;
Ok(())
})
}
fn pretty_print_const_value<'tcx>(
val: interpret::ConstValue<'tcx>,
ty: Ty<'tcx>,
fmt: &mut Formatter<'_>,
print_types: bool,
) -> fmt::Result {
use crate::ty::print::PrettyPrinter;
ty::tls::with(|tcx| {
let val = tcx.lift(val).unwrap();
let ty = tcx.lift(ty).unwrap();
let mut cx = FmtPrinter::new(tcx, fmt, Namespace::ValueNS);
cx.print_alloc_ids = true;
cx.pretty_print_const_value(val, ty, print_types)?;
Ok(())
})
}
impl<'tcx> graph::DirectedGraph for Body<'tcx> {
type Node = BasicBlock;
}
impl<'tcx> graph::WithNumNodes for Body<'tcx> {
#[inline]
fn num_nodes(&self) -> usize {
self.basic_blocks.len()
}
}
impl<'tcx> graph::WithStartNode for Body<'tcx> {
#[inline]
fn start_node(&self) -> Self::Node {
START_BLOCK
}
}
impl<'tcx> graph::WithSuccessors for Body<'tcx> {
#[inline]
fn successors(&self, node: Self::Node) -> <Self as GraphSuccessors<'_>>::Iter {
self.basic_blocks[node].terminator().successors().cloned()
}
}
impl<'a, 'b> graph::GraphSuccessors<'b> for Body<'a> {
type Item = BasicBlock;
type Iter = iter::Cloned<Successors<'b>>;
}
impl<'tcx, 'graph> graph::GraphPredecessors<'graph> for Body<'tcx> {
type Item = BasicBlock;
type Iter = std::iter::Copied<std::slice::Iter<'graph, BasicBlock>>;
}
impl<'tcx> graph::WithPredecessors for Body<'tcx> {
#[inline]
fn predecessors(&self, node: Self::Node) -> <Self as graph::GraphPredecessors<'_>>::Iter {
self.predecessors()[node].iter().copied()
}
}
/// `Location` represents the position of the start of the statement; or, if
/// `statement_index` equals the number of statements, then the start of the
/// terminator.
#[derive(Copy, Clone, PartialEq, Eq, Hash, Ord, PartialOrd, HashStable)]
pub struct Location {
/// The block that the location is within.
pub block: BasicBlock,
pub statement_index: usize,
}
impl fmt::Debug for Location {
fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(fmt, "{:?}[{}]", self.block, self.statement_index)
}
}
impl Location {
pub const START: Location = Location { block: START_BLOCK, statement_index: 0 };
/// Returns the location immediately after this one within the enclosing block.
///
/// Note that if this location represents a terminator, then the
/// resulting location would be out of bounds and invalid.
pub fn successor_within_block(&self) -> Location {
Location { block: self.block, statement_index: self.statement_index + 1 }
}
/// Returns `true` if `other` is earlier in the control flow graph than `self`.
pub fn is_predecessor_of<'tcx>(&self, other: Location, body: &Body<'tcx>) -> bool {
// If we are in the same block as the other location and are an earlier statement
// then we are a predecessor of `other`.
if self.block == other.block && self.statement_index < other.statement_index {
return true;
}
let predecessors = body.predecessors();
// If we're in another block, then we want to check that block is a predecessor of `other`.
let mut queue: Vec<BasicBlock> = predecessors[other.block].to_vec();
let mut visited = FxHashSet::default();
while let Some(block) = queue.pop() {
// If we haven't visited this block before, then make sure we visit it's predecessors.
if visited.insert(block) {
queue.extend(predecessors[block].iter().cloned());
} else {
continue;
}
// If we found the block that `self` is in, then we are a predecessor of `other` (since
// we found that block by looking at the predecessors of `other`).
if self.block == block {
return true;
}
}
false
}
pub fn dominates(&self, other: Location, dominators: &Dominators<BasicBlock>) -> bool {
if self.block == other.block {
self.statement_index <= other.statement_index
} else {
dominators.is_dominated_by(other.block, self.block)
}
}
}