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bring back extra check for int_min%-1

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Ralf Jung 2020-02-09 15:41:40 +01:00
parent 202d401c25
commit 28f85c6ffa
1 changed files with 11 additions and 0 deletions
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11
src/librustc_mir/interpret/operator.rs
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@ -195,6 +195,17 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
if let Some(op) = op {
let l128 = self.sign_extend(l, left_layout) as i128;
let r = self.sign_extend(r, right_layout) as i128;
// We need a special check for overflowing remainder:
// "int_min % -1" overflows and returns 0, but after casting things to a larger int
// type it does *not* overflow nor give an unrepresentable result!
match bin_op {
Rem => {
if r == -1 && l == (1 << (size.bits() - 1)) {
return Ok((Scalar::from_int(0, size), true, left_layout.ty));
}
}
_ => {}
}
let (result, oflo) = op(l128, r);
// This may be out-of-bounds for the result type, so we have to truncate ourselves.