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interpret: fix CheckedBinOp behavior when overflow checking is disabled

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This commit is contained in:
Ralf Jung 2022-07-04 08:57:10 -04:00
parent e1d1848cc6
commit 6f01ff61b3
3 changed files with 14 additions and 2 deletions
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4
compiler/rustc_const_eval/src/interpret/intrinsics.rs
View File

@ -217,7 +217,9 @@ pub fn emulate_intrinsic(
sym::mul_with_overflow => BinOp::Mul,
_ => bug!(),
};
self.binop_with_overflow(bin_op, &lhs, &rhs, dest)?;
self.binop_with_overflow(
bin_op, /*force_overflow_checks*/ true, &lhs, &rhs, dest,
)?;
}
sym::saturating_add | sym::saturating_sub => {
let l = self.read_immediate(&args[0])?;

8
compiler/rustc_const_eval/src/interpret/operator.rs
View File

@ -12,9 +12,13 @@
impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
/// Applies the binary operation `op` to the two operands and writes a tuple of the result
/// and a boolean signifying the potential overflow to the destination.
///
/// `force_overflow_checks` indicates whether overflow checks should be done even when
/// `tcx.sess.overflow_checks()` is `false`.
pub fn binop_with_overflow(
&mut self,
op: mir::BinOp,
force_overflow_checks: bool,
left: &ImmTy<'tcx, M::PointerTag>,
right: &ImmTy<'tcx, M::PointerTag>,
dest: &PlaceTy<'tcx, M::PointerTag>,
@ -26,6 +30,10 @@ pub fn binop_with_overflow(
"type mismatch for result of {:?}",
op,
);
// As per https://github.com/rust-lang/rust/pull/98738, we always return `false` in the 2nd
// component when overflow checking is disabled.
let overflowed = overflowed && (force_overflow_checks || self.tcx.sess.overflow_checks());
// Write the result to `dest`.
if let Abi::ScalarPair(..) = dest.layout.abi {
// We can use the optimized path and avoid `place_field` (which might do
// `force_allocation`).

4
compiler/rustc_const_eval/src/interpret/step.rs
View File

@ -185,7 +185,9 @@ pub fn eval_rvalue_into_place(
let left = self.read_immediate(&self.eval_operand(left, None)?)?;
let layout = binop_right_homogeneous(bin_op).then_some(left.layout);
let right = self.read_immediate(&self.eval_operand(right, layout)?)?;
self.binop_with_overflow(bin_op, &left, &right, &dest)?;
self.binop_with_overflow(
bin_op, /*force_overflow_checks*/ false, &left, &right, &dest,
)?;
}
UnaryOp(un_op, ref operand) => {