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Only visit reachable blocks in ConstProp lint.

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This commit is contained in:
Camille GILLOT 2023-03-30 18:40:47 +00:00
parent f8cfafcceb
commit 7d47a910eb
3 changed files with 48 additions and 8 deletions
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40
compiler/rustc_mir_transform/src/const_prop_lint.rs
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@ -9,6 +9,7 @@ use rustc_const_eval::interpret::{
};
use rustc_hir::def::DefKind;
use rustc_hir::HirId;
use rustc_index::bit_set::BitSet;
use rustc_middle::mir::visit::Visitor;
use rustc_middle::mir::*;
use rustc_middle::ty::layout::{LayoutError, LayoutOf, LayoutOfHelpers, TyAndLayout};
@ -129,6 +130,8 @@ struct ConstPropagator<'mir, 'tcx> {
ecx: InterpCx<'mir, 'tcx, ConstPropMachine<'mir, 'tcx>>,
tcx: TyCtxt<'tcx>,
param_env: ParamEnv<'tcx>,
worklist: Vec<BasicBlock>,
visited_blocks: BitSet<BasicBlock>,
}
impl<'tcx> LayoutOfHelpers<'tcx> for ConstPropagator<'_, 'tcx> {
@ -203,7 +206,13 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
)
.expect("failed to push initial stack frame");
ConstPropagator { ecx, tcx, param_env }
ConstPropagator {
ecx,
tcx,
param_env,
worklist: vec![START_BLOCK],
visited_blocks: BitSet::new_empty(body.basic_blocks.len()),
}
}
fn body(&self) -> &'mir Body<'tcx> {
@ -496,12 +505,10 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
if expected != value_const {
// Poison all places this operand references so that further code
// doesn't use the invalid value
match cond {
Operand::Move(ref place) | Operand::Copy(ref place) => {
Self::remove_const(&mut self.ecx, place.local);
}
Operand::Constant(_) => {}
if let Some(place) = cond.place() {
Self::remove_const(&mut self.ecx, place.local);
}
enum DbgVal<T> {
Val(T),
Underscore,
@ -566,7 +573,12 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
impl<'tcx> Visitor<'tcx> for ConstPropagator<'_, 'tcx> {
fn visit_body(&mut self, body: &Body<'tcx>) {
for (bb, data) in body.basic_blocks.iter_enumerated() {
while let Some(bb) = self.worklist.pop() {
if !self.visited_blocks.insert(bb) {
continue;
}
let data = &body.basic_blocks[bb];
self.visit_basic_block_data(bb, data);
}
}
@ -657,6 +669,17 @@ impl<'tcx> Visitor<'tcx> for ConstPropagator<'_, 'tcx> {
TerminatorKind::Assert { expected, ref msg, ref cond, .. } => {
self.check_assertion(*expected, msg, cond, location);
}
TerminatorKind::SwitchInt { ref discr, ref targets } => {
if let Some(ref value) = self.eval_operand(&discr, location)
&& let Some(value_const) = self.use_ecx(location, |this| this.ecx.read_scalar(&value))
&& let Ok(constant) = value_const.try_to_int()
&& let Ok(constant) = constant.to_bits(constant.size())
{
let target = targets.target_for_value(constant);
self.worklist.push(target);
return;
}
}
// None of these have Operands to const-propagate.
TerminatorKind::Goto { .. }
| TerminatorKind::Resume
@ -668,10 +691,11 @@ impl<'tcx> Visitor<'tcx> for ConstPropagator<'_, 'tcx> {
| TerminatorKind::GeneratorDrop
| TerminatorKind::FalseEdge { .. }
| TerminatorKind::FalseUnwind { .. }
| TerminatorKind::SwitchInt { .. }
| TerminatorKind::Call { .. }
| TerminatorKind::InlineAsm { .. } => {}
}
self.worklist.extend(terminator.successors());
}
fn visit_basic_block_data(&mut self, block: BasicBlock, data: &BasicBlockData<'tcx>) {