rustc_middle/mir/mod.rs
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//! 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 std::borrow::Cow;
use std::fmt::{self, Debug, Formatter};
use std::ops::{Index, IndexMut};
use std::{iter, mem};
pub use basic_blocks::BasicBlocks;
use either::Either;
use polonius_engine::Atom;
use rustc_abi::{FieldIdx, VariantIdx};
pub use rustc_ast::Mutability;
use rustc_data_structures::captures::Captures;
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_data_structures::graph::dominators::Dominators;
use rustc_errors::{DiagArgName, DiagArgValue, DiagMessage, ErrorGuaranteed, IntoDiagArg};
use rustc_hir::def::{CtorKind, Namespace};
use rustc_hir::def_id::{CRATE_DEF_ID, DefId};
use rustc_hir::{
self as hir, BindingMode, ByRef, CoroutineDesugaring, CoroutineKind, HirId, ImplicitSelfKind,
};
use rustc_index::bit_set::BitSet;
use rustc_index::{Idx, IndexSlice, IndexVec};
use rustc_macros::{HashStable, TyDecodable, TyEncodable, TypeFoldable, TypeVisitable};
use rustc_serialize::{Decodable, Encodable};
use rustc_span::source_map::Spanned;
use rustc_span::symbol::Symbol;
use rustc_span::{DUMMY_SP, Span};
use tracing::trace;
pub use self::query::*;
use self::visit::TyContext;
use crate::mir::interpret::{AllocRange, Scalar};
use crate::mir::visit::MirVisitable;
use crate::ty::codec::{TyDecoder, TyEncoder};
use crate::ty::fold::{FallibleTypeFolder, TypeFoldable};
use crate::ty::print::{FmtPrinter, Printer, pretty_print_const, with_no_trimmed_paths};
use crate::ty::visit::TypeVisitableExt;
use crate::ty::{
self, AdtDef, GenericArg, GenericArgsRef, Instance, InstanceKind, List, Ty, TyCtxt, TypingMode,
UserTypeAnnotationIndex,
};
mod basic_blocks;
mod consts;
pub mod coverage;
mod generic_graph;
pub mod generic_graphviz;
pub mod graphviz;
pub mod interpret;
pub mod mono;
pub mod patch;
pub mod pretty;
mod query;
mod statement;
mod syntax;
pub mod tcx;
mod terminator;
pub mod traversal;
mod type_foldable;
pub mod visit;
pub use consts::*;
use pretty::pretty_print_const_value;
pub use statement::*;
pub use syntax::*;
pub use terminator::*;
pub use self::generic_graph::graphviz_safe_def_name;
pub use self::graphviz::write_mir_graphviz;
pub use self::pretty::{
PassWhere, create_dump_file, display_allocation, dump_enabled, dump_mir, write_mir_pretty,
};
/// Types for locals
pub type LocalDecls<'tcx> = IndexSlice<Local, LocalDecl<'tcx>>;
pub trait HasLocalDecls<'tcx> {
fn local_decls(&self) -> &LocalDecls<'tcx>;
}
impl<'tcx> HasLocalDecls<'tcx> for IndexVec<Local, LocalDecl<'tcx>> {
#[inline]
fn local_decls(&self) -> &LocalDecls<'tcx> {
self
}
}
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
}
}
impl MirPhase {
/// Gets the index of the current MirPhase within the set of all `MirPhase`s.
///
/// FIXME(JakobDegen): Return a `(usize, usize)` instead.
pub fn phase_index(&self) -> usize {
const BUILT_PHASE_COUNT: usize = 1;
const ANALYSIS_PHASE_COUNT: usize = 2;
match self {
MirPhase::Built => 1,
MirPhase::Analysis(analysis_phase) => {
1 + BUILT_PHASE_COUNT + (*analysis_phase as usize)
}
MirPhase::Runtime(runtime_phase) => {
1 + BUILT_PHASE_COUNT + ANALYSIS_PHASE_COUNT + (*runtime_phase as usize)
}
}
}
/// Parses an `MirPhase` from a pair of strings. Panics if this isn't possible for any reason.
pub fn parse(dialect: String, phase: Option<String>) -> Self {
match &*dialect.to_ascii_lowercase() {
"built" => {
assert!(phase.is_none(), "Cannot specify a phase for `Built` MIR");
MirPhase::Built
}
"analysis" => Self::Analysis(AnalysisPhase::parse(phase)),
"runtime" => Self::Runtime(RuntimePhase::parse(phase)),
_ => bug!("Unknown MIR dialect: '{}'", dialect),
}
}
}
impl AnalysisPhase {
pub fn parse(phase: Option<String>) -> Self {
let Some(phase) = phase else {
return Self::Initial;
};
match &*phase.to_ascii_lowercase() {
"initial" => Self::Initial,
"post_cleanup" | "post-cleanup" | "postcleanup" => Self::PostCleanup,
_ => bug!("Unknown analysis phase: '{}'", phase),
}
}
}
impl RuntimePhase {
pub fn parse(phase: Option<String>) -> Self {
let Some(phase) = phase else {
return Self::Initial;
};
match &*phase.to_ascii_lowercase() {
"initial" => Self::Initial,
"post_cleanup" | "post-cleanup" | "postcleanup" => Self::PostCleanup,
"optimized" => Self::Optimized,
_ => bug!("Unknown runtime phase: '{}'", phase),
}
}
}
/// Where a specific `mir::Body` comes from.
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
#[derive(HashStable, TyEncodable, TyDecodable, TypeFoldable, TypeVisitable)]
pub struct MirSource<'tcx> {
pub instance: InstanceKind<'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: InstanceKind::Item(def_id), promoted: None }
}
pub fn from_instance(instance: InstanceKind<'tcx>) -> Self {
MirSource { instance, promoted: None }
}
#[inline]
pub fn def_id(&self) -> DefId {
self.instance.def_id()
}
}
/// Additional information carried by a MIR body when it is lowered from a coroutine.
/// This information is modified as it is lowered during the `StateTransform` MIR pass,
/// so not all fields will be active at a given time. For example, the `yield_ty` is
/// taken out of the field after yields are turned into returns, and the `coroutine_drop`
/// body is only populated after the state transform pass.
#[derive(Clone, TyEncodable, TyDecodable, Debug, HashStable, TypeFoldable, TypeVisitable)]
pub struct CoroutineInfo<'tcx> {
/// The yield type of the function. This field is removed after the state transform pass.
pub yield_ty: Option<Ty<'tcx>>,
/// The resume type of the function. This field is removed after the state transform pass.
pub resume_ty: Option<Ty<'tcx>>,
/// Coroutine drop glue. This field is populated after the state transform pass.
pub coroutine_drop: Option<Body<'tcx>>,
/// The layout of a coroutine. This field is populated after the state transform pass.
pub coroutine_layout: Option<CoroutineLayout<'tcx>>,
/// If this is a coroutine then record the type of source expression that caused this coroutine
/// to be created.
pub coroutine_kind: CoroutineKind,
}
impl<'tcx> CoroutineInfo<'tcx> {
// Sets up `CoroutineInfo` for a pre-coroutine-transform MIR body.
pub fn initial(
coroutine_kind: CoroutineKind,
yield_ty: Ty<'tcx>,
resume_ty: Ty<'tcx>,
) -> CoroutineInfo<'tcx> {
CoroutineInfo {
coroutine_kind,
yield_ty: Some(yield_ty),
resume_ty: Some(resume_ty),
coroutine_drop: None,
coroutine_layout: None,
}
}
}
/// Some item that needs to monomorphize successfully for a MIR body to be considered well-formed.
#[derive(Copy, Clone, PartialEq, Eq, Debug, Hash, HashStable, TyEncodable, TyDecodable)]
#[derive(TypeFoldable, TypeVisitable)]
pub enum MentionedItem<'tcx> {
/// A function that gets called. We don't necessarily know its precise type yet, since it can be
/// hidden behind a generic.
Fn(Ty<'tcx>),
/// A type that has its drop shim called.
Drop(Ty<'tcx>),
/// Unsizing casts might require vtables, so we have to record them.
UnsizeCast { source_ty: Ty<'tcx>, target_ty: Ty<'tcx> },
/// A closure that is coerced to a function pointer.
Closure(Ty<'tcx>),
}
/// The lowered representation of a single function.
#[derive(Clone, TyEncodable, TyDecodable, Debug, HashStable, TypeFoldable, TypeVisitable)]
pub struct Body<'tcx> {
/// A list of basic blocks. References to basic block use a newtyped index type [`BasicBlock`]
/// that indexes into this vector.
pub basic_blocks: BasicBlocks<'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,
/// How many passses we have executed since starting the current phase. Used for debug output.
pub pass_count: usize,
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>>,
/// Additional information carried by a MIR body when it is lowered from a coroutine.
///
/// Note that the coroutine drop shim, any promoted consts, and other synthetic MIR
/// bodies that come from processing a coroutine body are not typically coroutines
/// themselves, and should probably set this to `None` to avoid carrying redundant
/// information.
pub coroutine: Option<Box<CoroutineInfo<'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: IndexVec<Local, LocalDecl<'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.
/// `None` indicates that the list has not been computed yet.
///
/// This is soundness-critical, we make a guarantee that all consts syntactically mentioned in a
/// function have successfully evaluated if the function ever gets executed at runtime.
pub required_consts: Option<Vec<ConstOperand<'tcx>>>,
/// Further items that were mentioned in this function and hence *may* become monomorphized,
/// depending on optimizations. We use this to avoid optimization-dependent compile errors: the
/// collector recursively traverses all "mentioned" items and evaluates all their
/// `required_consts`.
/// `None` indicates that the list has not been computed yet.
///
/// This is *not* soundness-critical and the contents of this list are *not* a stable guarantee.
/// All that's relevant is that this set is optimization-level-independent, and that it includes
/// everything that the collector would consider "used". (For example, we currently compute this
/// set after drop elaboration, so some drop calls that can never be reached are not considered
/// "mentioned".) See the documentation of `CollectionMode` in
/// `compiler/rustc_monomorphize/src/collector.rs` for more context.
pub mentioned_items: Option<Vec<Spanned<MentionedItem<'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,
/// The phase at which this MIR should be "injected" into the compilation process.
///
/// Everything that comes before this `MirPhase` should be skipped.
///
/// This is only `Some` if the function that this body comes from was annotated with `rustc_custom_mir`.
pub injection_phase: Option<MirPhase>,
pub tainted_by_errors: Option<ErrorGuaranteed>,
/// Coverage information collected from THIR/MIR during MIR building,
/// to be used by the `InstrumentCoverage` pass.
///
/// Only present if coverage is enabled and this function is eligible.
/// Boxed to limit space overhead in non-coverage builds.
pub coverage_info_hi: Option<Box<coverage::CoverageInfoHi>>,
/// Per-function coverage information added by the `InstrumentCoverage`
/// pass, to be used in conjunction with the coverage statements injected
/// into this body's blocks.
///
/// If `-Cinstrument-coverage` is not active, or if an individual function
/// is not eligible for coverage, then this should always be `None`.
pub function_coverage_info: Option<Box<coverage::FunctionCoverageInfo>>,
}
impl<'tcx> Body<'tcx> {
pub fn new(
source: MirSource<'tcx>,
basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,
source_scopes: IndexVec<SourceScope, SourceScopeData<'tcx>>,
local_decls: IndexVec<Local, LocalDecl<'tcx>>,
user_type_annotations: ty::CanonicalUserTypeAnnotations<'tcx>,
arg_count: usize,
var_debug_info: Vec<VarDebugInfo<'tcx>>,
span: Span,
coroutine: Option<Box<CoroutineInfo<'tcx>>>,
tainted_by_errors: Option<ErrorGuaranteed>,
) -> 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::Built,
pass_count: 0,
source,
basic_blocks: BasicBlocks::new(basic_blocks),
source_scopes,
coroutine,
local_decls,
user_type_annotations,
arg_count,
spread_arg: None,
var_debug_info,
span,
required_consts: None,
mentioned_items: None,
is_polymorphic: false,
injection_phase: None,
tainted_by_errors,
coverage_info_hi: None,
function_coverage_info: None,
};
body.is_polymorphic = body.has_non_region_param();
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::Built,
pass_count: 0,
source: MirSource::item(CRATE_DEF_ID.to_def_id()),
basic_blocks: BasicBlocks::new(basic_blocks),
source_scopes: IndexVec::new(),
coroutine: None,
local_decls: IndexVec::new(),
user_type_annotations: IndexVec::new(),
arg_count: 0,
spread_arg: None,
span: DUMMY_SP,
required_consts: None,
mentioned_items: None,
var_debug_info: Vec::new(),
is_polymorphic: false,
injection_phase: None,
tainted_by_errors: None,
coverage_info_hi: None,
function_coverage_info: None,
};
body.is_polymorphic = body.has_non_region_param();
body
}
#[inline]
pub fn basic_blocks_mut(&mut self) -> &mut IndexVec<BasicBlock, BasicBlockData<'tcx>> {
self.basic_blocks.as_mut()
}
pub fn typing_mode(&self, _tcx: TyCtxt<'tcx>) -> TypingMode<'tcx> {
match self.phase {
// FIXME(#132279): the MIR is quite clearly inside of a body, so we
// should instead reveal opaques defined by that body here.
MirPhase::Built | MirPhase::Analysis(_) => TypingMode::non_body_analysis(),
MirPhase::Runtime(_) => TypingMode::PostAnalysis,
}
}
#[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 {
LocalKind::Temp
}
}
/// Returns an iterator over all user-declared mutable locals.
#[inline]
pub fn mut_vars_iter<'a>(&'a self) -> impl Iterator<Item = Local> + Captures<'tcx> + 'a {
(self.arg_count + 1..self.local_decls.len()).filter_map(move |index| {
let local = Local::new(index);
let decl = &self.local_decls[local];
(decl.is_user_variable() && decl.mutability.is_mut()).then_some(local)
})
}
/// 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> + Captures<'tcx> + '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..)
}
/// 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
}
}
pub fn span_for_ty_context(&self, ty_context: TyContext) -> Span {
match ty_context {
TyContext::UserTy(span) => span,
TyContext::ReturnTy(source_info)
| TyContext::LocalDecl { source_info, .. }
| TyContext::YieldTy(source_info)
| TyContext::ResumeTy(source_info) => source_info.span,
TyContext::Location(loc) => self.source_info(loc).span,
}
}
/// 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
}
/// Returns the return type; it always return first element from `local_decls` array.
#[inline]
pub fn bound_return_ty(&self) -> ty::EarlyBinder<'tcx, Ty<'tcx>> {
ty::EarlyBinder::bind(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 yield_ty(&self) -> Option<Ty<'tcx>> {
self.coroutine.as_ref().and_then(|coroutine| coroutine.yield_ty)
}
#[inline]
pub fn resume_ty(&self) -> Option<Ty<'tcx>> {
self.coroutine.as_ref().and_then(|coroutine| coroutine.resume_ty)
}
/// Prefer going through [`TyCtxt::coroutine_layout`] rather than using this directly.
#[inline]
pub fn coroutine_layout_raw(&self) -> Option<&CoroutineLayout<'tcx>> {
self.coroutine.as_ref().and_then(|coroutine| coroutine.coroutine_layout.as_ref())
}
#[inline]
pub fn coroutine_drop(&self) -> Option<&Body<'tcx>> {
self.coroutine.as_ref().and_then(|coroutine| coroutine.coroutine_drop.as_ref())
}
#[inline]
pub fn coroutine_kind(&self) -> Option<CoroutineKind> {
self.coroutine.as_ref().map(|coroutine| coroutine.coroutine_kind)
}
#[inline]
pub fn should_skip(&self) -> bool {
let Some(injection_phase) = self.injection_phase else {
return false;
};
injection_phase > self.phase
}
#[inline]
pub fn is_custom_mir(&self) -> bool {
self.injection_phase.is_some()
}
/// If this basic block ends with a [`TerminatorKind::SwitchInt`] for which we can evaluate the
/// dimscriminant in monomorphization, we return the discriminant bits and the
/// [`SwitchTargets`], just so the caller doesn't also have to match on the terminator.
fn try_const_mono_switchint<'a>(
tcx: TyCtxt<'tcx>,
instance: Instance<'tcx>,
block: &'a BasicBlockData<'tcx>,
) -> Option<(u128, &'a SwitchTargets)> {
// There are two places here we need to evaluate a constant.
let eval_mono_const = |constant: &ConstOperand<'tcx>| {
let env = ty::ParamEnv::reveal_all();
let mono_literal = instance.instantiate_mir_and_normalize_erasing_regions(
tcx,
env,
crate::ty::EarlyBinder::bind(constant.const_),
);
mono_literal.try_eval_bits(tcx, env)
};
let TerminatorKind::SwitchInt { discr, targets } = &block.terminator().kind else {
return None;
};
// If this is a SwitchInt(const _), then we can just evaluate the constant and return.
let discr = match discr {
Operand::Constant(constant) => {
let bits = eval_mono_const(constant)?;
return Some((bits, targets));
}
Operand::Move(place) | Operand::Copy(place) => place,
};
// MIR for `if false` actually looks like this:
// _1 = const _
// SwitchInt(_1)
//
// And MIR for if intrinsics::ub_checks() looks like this:
// _1 = UbChecks()
// SwitchInt(_1)
//
// So we're going to try to recognize this pattern.
//
// If we have a SwitchInt on a non-const place, we find the most recent statement that
// isn't a storage marker. If that statement is an assignment of a const to our
// discriminant place, we evaluate and return the const, as if we've const-propagated it
// into the SwitchInt.
let last_stmt = block.statements.iter().rev().find(|stmt| {
!matches!(stmt.kind, StatementKind::StorageDead(_) | StatementKind::StorageLive(_))
})?;
let (place, rvalue) = last_stmt.kind.as_assign()?;
if discr != place {
return None;
}
match rvalue {
Rvalue::NullaryOp(NullOp::UbChecks, _) => Some((tcx.sess.ub_checks() as u128, targets)),
Rvalue::Use(Operand::Constant(constant)) => {
let bits = eval_mono_const(constant)?;
Some((bits, targets))
}
_ => None,
}
}
/// For a `Location` in this scope, determine what the "caller location" at that point is. This
/// is interesting because of inlining: the `#[track_caller]` attribute of inlined functions
/// must be honored. Falls back to the `tracked_caller` value for `#[track_caller]` functions,
/// or the function's scope.
pub fn caller_location_span<T>(
&self,
mut source_info: SourceInfo,
caller_location: Option<T>,
tcx: TyCtxt<'tcx>,
from_span: impl FnOnce(Span) -> T,
) -> T {
loop {
let scope_data = &self.source_scopes[source_info.scope];
if let Some((callee, callsite_span)) = scope_data.inlined {
// Stop inside the most nested non-`#[track_caller]` function,
// before ever reaching its caller (which is irrelevant).
if !callee.def.requires_caller_location(tcx) {
return from_span(source_info.span);
}
source_info.span = callsite_span;
}
// Skip past all of the parents with `inlined: None`.
match scope_data.inlined_parent_scope {
Some(parent) => source_info.scope = parent,
None => break,
}
}
// No inlined `SourceScope`s, or all of them were `#[track_caller]`.
caller_location.unwrap_or_else(|| from_span(source_info.span))
}
#[track_caller]
pub fn set_required_consts(&mut self, required_consts: Vec<ConstOperand<'tcx>>) {
assert!(
self.required_consts.is_none(),
"required_consts for {:?} have already been set",
self.source.def_id()
);
self.required_consts = Some(required_consts);
}
#[track_caller]
pub fn required_consts(&self) -> &[ConstOperand<'tcx>] {
match &self.required_consts {
Some(l) => l,
None => panic!("required_consts for {:?} have not yet been set", self.source.def_id()),
}
}
#[track_caller]
pub fn set_mentioned_items(&mut self, mentioned_items: Vec<Spanned<MentionedItem<'tcx>>>) {
assert!(
self.mentioned_items.is_none(),
"mentioned_items for {:?} have already been set",
self.source.def_id()
);
self.mentioned_items = Some(mentioned_items);
}
#[track_caller]
pub fn mentioned_items(&self) -> &[Spanned<MentionedItem<'tcx>>] {
match &self.mentioned_items {
Some(l) => l,
None => panic!("mentioned_items for {:?} have not yet been set", self.source.def_id()),
}
}
}
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.as_mut()[index]
}
}
#[derive(Copy, Clone, Debug, HashStable, TypeFoldable, TypeVisitable)]
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 as_mut(&mut self) -> ClearCrossCrate<&mut 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<E: TyEncoder, T: Encodable<E>> Encodable<E> for ClearCrossCrate<T> {
#[inline]
fn encode(&self, e: &mut E) {
if E::CLEAR_CROSS_CRATE {
return;
}
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<D: TyDecoder, T: Decodable<D>> Decodable<D> for ClearCrossCrate<T> {
#[inline]
fn decode(d: &mut D) -> ClearCrossCrate<T> {
if D::CLEAR_CROSS_CRATE {
return ClearCrossCrate::Clear;
}
let discr = u8::decode(d);
match discr {
TAG_CLEAR_CROSS_CRATE_CLEAR => ClearCrossCrate::Clear,
TAG_CLEAR_CROSS_CRATE_SET => {
let val = T::decode(d);
ClearCrossCrate::Set(val)
}
tag => panic!("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, etc.
pub scope: SourceScope,
}
impl SourceInfo {
#[inline]
pub fn outermost(span: Span) -> Self {
SourceInfo { span, scope: OUTERMOST_SOURCE_SCOPE }
}
}
///////////////////////////////////////////////////////////////////////////
// Variables and temps
rustc_index::newtype_index! {
#[derive(HashStable)]
#[encodable]
#[orderable]
#[debug_format = "_{}"]
pub struct Local {
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 or 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`, `ref mut x`, `mut ref x`, or `mut ref mut x`?
pub binding_mode: 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,
}
TrivialTypeTraversalImpls! { 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, TypeVisitable)]
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: ClearCrossCrate<Box<LocalInfo<'tcx>>>,
/// 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::<u32>().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,
}
/// 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 borrow checking.
///
/// Not used for non-StaticRef temporaries, the return place, or anonymous
/// function parameters.
#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]
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(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,
/// 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`
BlockTailTemp(BlockTailInfo),
/// A temporary created during evaluating `if` predicate, possibly for pattern matching for `let`s,
/// and subject to Edition 2024 temporary lifetime rules
IfThenRescopeTemp { if_then: HirId },
/// A temporary created during the pass `Derefer` to avoid it's retagging
DerefTemp,
/// A temporary created for borrow checking.
FakeBorrow,
/// A local without anything interesting about it.
Boring,
}
impl<'tcx> LocalDecl<'tcx> {
pub fn local_info(&self) -> &LocalInfo<'tcx> {
self.local_info.as_ref().assert_crate_local()
}
/// 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(),
LocalInfo::User(
BindingForm::Var(VarBindingForm {
binding_mode: BindingMode(ByRef::No, _),
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(),
LocalInfo::User(
BindingForm::Var(VarBindingForm {
binding_mode: BindingMode(ByRef::No, _),
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(), 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(), LocalInfo::User(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(), 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() {
LocalInfo::StaticRef { is_thread_local, .. } => *is_thread_local,
_ => false,
}
}
/// Returns `true` if this is a DerefTemp
pub fn is_deref_temp(&self) -> bool {
match self.local_info() {
LocalInfo::DerefTemp => true,
_ => 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.
#[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: ClearCrossCrate::Set(Box::new(LocalInfo::Boring)),
ty,
user_ty: None,
source_info,
}
}
/// Converts `self` into same `LocalDecl` except tagged as immutable.
#[inline]
pub fn immutable(mut self) -> Self {
self.mutability = Mutability::Not;
self
}
}
#[derive(Clone, TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]
pub enum VarDebugInfoContents<'tcx> {
/// This `Place` only contains projection which satisfy `can_use_in_debuginfo`.
Place(Place<'tcx>),
Const(ConstOperand<'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:?}"),
}
}
}
#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]
pub struct VarDebugInfoFragment<'tcx> {
/// Type of the original user variable.
/// This cannot contain a union or an enum.
pub ty: Ty<'tcx>,
/// Where in the composite user variable this fragment is,
/// represented as a "projection" into the composite variable.
/// At lower levels, this corresponds to a byte/bit range.
///
/// This can only contain `PlaceElem::Field`.
// FIXME support this for `enum`s by either using DWARF's
// more advanced control-flow features (unsupported by LLVM?)
// to match on the discriminant, or by using custom type debuginfo
// with non-overlapping variants for the composite variable.
pub projection: Vec<PlaceElem<'tcx>>,
}
/// Debug information pertaining to a user variable.
#[derive(Clone, TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]
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,
/// The user variable's data is split across several fragments,
/// each described by a `VarDebugInfoFragment`.
/// See DWARF 5's "2.6.1.2 Composite Location Descriptions"
/// and LLVM's `DW_OP_LLVM_fragment` for more details on
/// the underlying debuginfo feature this relies on.
pub composite: Option<Box<VarDebugInfoFragment<'tcx>>>,
/// Where the data for this user variable is to be found.
pub value: VarDebugInfoContents<'tcx>,
/// When present, indicates what argument number this variable is in the function that it
/// originated from (starting from 1). Note, if MIR inlining is enabled, then this is the
/// argument number in the original function before it was inlined.
pub argument_index: Option<u16>,
}
///////////////////////////////////////////////////////////////////////////
// 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_mir_transform/add_call_guards/enum.AddCallGuards.html#variant.CriticalCallEdges
/// [guide-mir]: https://rustc-dev-guide.rust-lang.org/mir/
#[derive(HashStable)]
#[encodable]
#[orderable]
#[debug_format = "bb{}"]
pub struct BasicBlock {
const START_BLOCK = 0;
}
}
impl BasicBlock {
pub fn start_location(self) -> Location {
Location { block: self, statement_index: 0 }
}
}
///////////////////////////////////////////////////////////////////////////
// BasicBlockData
/// Data for a basic block, including a list of its statements.
///
/// See [`BasicBlock`] for documentation on what basic blocks are at a high level.
#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]
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,
}
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 convenient 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 }
}
/// Does the block have no statements and an unreachable terminator?
#[inline]
pub fn is_empty_unreachable(&self) -> bool {
self.statements.is_empty() && matches!(self.terminator().kind, TerminatorKind::Unreachable)
}
/// Like [`Terminator::successors`] but tries to use information available from the [`Instance`]
/// to skip successors like the `false` side of an `if const {`.
///
/// This is used to implement [`traversal::mono_reachable`] and
/// [`traversal::mono_reachable_reverse_postorder`].
pub fn mono_successors(&self, tcx: TyCtxt<'tcx>, instance: Instance<'tcx>) -> Successors<'_> {
if let Some((bits, targets)) = Body::try_const_mono_switchint(tcx, instance, self) {
targets.successors_for_value(bits)
} else {
self.terminator().successors()
}
}
}
///////////////////////////////////////////////////////////////////////////
// Scopes
rustc_index::newtype_index! {
#[derive(HashStable)]
#[encodable]
#[debug_format = "scope[{}]"]
pub struct SourceScope {
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(
self,
source_scopes: &IndexSlice<SourceScope, SourceScopeData<'_>>,
) -> 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,
}
}
/// The instance this source scope was inlined from, if any.
#[inline]
pub fn inlined_instance<'tcx>(
self,
source_scopes: &IndexSlice<SourceScope, SourceScopeData<'tcx>>,
) -> Option<ty::Instance<'tcx>> {
let scope_data = &source_scopes[self];
if let Some((inlined_instance, _)) = scope_data.inlined {
Some(inlined_instance)
} else if let Some(inlined_scope) = scope_data.inlined_parent_scope {
Some(source_scopes[inlined_scope].inlined.unwrap().0)
} else {
None
}
}
}
#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]
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: HirId,
}
/// 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.
///
/// It's 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:
///
/// ```ignore (illustrative)
/// 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, TypeVisitable)]
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: FieldIdx) -> Self {
self.map_projections(|pat_ty_proj| pat_ty_proj.leaf(field))
}
pub fn variant(
self,
adt_def: AdtDef<'tcx>,
variant_index: VariantIdx,
field_index: FieldIdx,
) -> Self {
self.map_projections(|pat_ty_proj| pat_ty_proj.variant(adt_def, variant_index, field_index))
}
}
/// 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 projections 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)]
#[derive(TypeFoldable, TypeVisitable)]
pub struct UserTypeProjection {
pub base: UserTypeAnnotationIndex,
pub projs: Vec<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: FieldIdx) -> Self {
self.projs.push(ProjectionElem::Field(field, ()));
self
}
pub(crate) fn variant(
mut self,
adt_def: AdtDef<'_>,
variant_index: VariantIdx,
field_index: FieldIdx,
) -> Self {
self.projs.push(ProjectionElem::Downcast(
Some(adt_def.variant(variant_index).name),
variant_index,
));
self.projs.push(ProjectionElem::Field(field_index, ()));
self
}
}
rustc_index::newtype_index! {
#[derive(HashStable)]
#[encodable]
#[orderable]
#[debug_format = "promoted[{}]"]
pub struct Promoted {}
}
/// `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.
#[inline]
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.basic_blocks.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 its 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
}
#[inline]
pub fn dominates(&self, other: Location, dominators: &Dominators<BasicBlock>) -> bool {
if self.block == other.block {
self.statement_index <= other.statement_index
} else {
dominators.dominates(self.block, other.block)
}
}
}
/// `DefLocation` represents the location of a definition - either an argument or an assignment
/// within MIR body.
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub enum DefLocation {
Argument,
Assignment(Location),
CallReturn { call: BasicBlock, target: Option<BasicBlock> },
}
impl DefLocation {
#[inline]
pub fn dominates(self, location: Location, dominators: &Dominators<BasicBlock>) -> bool {
match self {
DefLocation::Argument => true,
DefLocation::Assignment(def) => {
def.successor_within_block().dominates(location, dominators)
}
DefLocation::CallReturn { target: None, .. } => false,
DefLocation::CallReturn { call, target: Some(target) } => {
// The definition occurs on the call -> target edge. The definition dominates a use
// if and only if the edge is on all paths from the entry to the use.
//
// Note that a call terminator has only one edge that can reach the target, so when
// the call strongly dominates the target, all paths from the entry to the target
// go through the call -> target edge.
call != target
&& dominators.dominates(call, target)
&& dominators.dominates(target, location.block)
}
}
}
}
// Some nodes are used a lot. Make sure they don't unintentionally get bigger.
#[cfg(target_pointer_width = "64")]
mod size_asserts {
use rustc_data_structures::static_assert_size;
use super::*;
// tidy-alphabetical-start
static_assert_size!(BasicBlockData<'_>, 128);
static_assert_size!(LocalDecl<'_>, 40);
static_assert_size!(SourceScopeData<'_>, 64);
static_assert_size!(Statement<'_>, 32);
static_assert_size!(Terminator<'_>, 96);
static_assert_size!(VarDebugInfo<'_>, 88);
// tidy-alphabetical-end
}