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Rollup merge of #102045 - RalfJung:const-prop-regression-fix, r=oli-obk

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fix ConstProp handling of written_only_inside_own_block_locals

Fixes a regression introduced by https://github.com/rust-lang/rust/pull/100239, which adds an early return and thus skips some code in `visit_terminator` that must be run for soundness.

Fixes https://github.com/rust-lang/rust/issues/101973
This commit is contained in:
Dylan DPC 2022-09-21 19:01:08 +05:30 • committed by GitHub
commit 7d7f55599a
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3 changed files with 140 additions and 20 deletions
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40
compiler/rustc_mir_transform/src/const_prop.rs
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@ -1066,32 +1066,32 @@ impl<'tcx> MutVisitor<'tcx> for ConstPropagator<'_, 'tcx> {
let source_info = terminator.source_info;
self.source_info = Some(source_info);
self.super_terminator(terminator, location);
// Do NOT early return in this function, it does some crucial fixup of the state at the end!
match &mut terminator.kind {
TerminatorKind::Assert { expected, ref mut cond, .. } => {
if let Some(ref value) = self.eval_operand(&cond) {
trace!("assertion on {:?} should be {:?}", value, expected);
let expected = Scalar::from_bool(*expected);
let Ok(value_const) = self.ecx.read_scalar(&value) else {
// FIXME should be used use_ecx rather than a local match... but we have
// quite a few of these read_scalar/read_immediate that need fixing.
return
};
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);
// FIXME should be used use_ecx rather than a local match... but we have
// quite a few of these read_scalar/read_immediate that need fixing.
if let Ok(value_const) = self.ecx.read_scalar(&value) {
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(_) => {}
}
} else {
if self.should_const_prop(value) {
*cond = self.operand_from_scalar(
value_const,
self.tcx.types.bool,
source_info.span,
);
}
Operand::Constant(_) => {}
}
} else {
if self.should_const_prop(value) {
*cond = self.operand_from_scalar(
value_const,
self.tcx.types.bool,
source_info.span,
);
}
}
}