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miri: fix exact_div
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RalfJung committed Feb 13, 2020
1 parent 2e6eace commit 10f342a
Showing 1 changed file with 4 additions and 2 deletions.
6 changes: 4 additions & 2 deletions src/librustc_mir/interpret/intrinsics.rs
Original file line number Diff line number Diff line change
Expand Up @@ -410,8 +410,9 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
) -> InterpResult<'tcx> {
// Performs an exact division, resulting in undefined behavior where
// `x % y != 0` or `y == 0` or `x == T::min_value() && y == -1`.
// First, check x % y != 0.
if self.binary_op(BinOp::Rem, a, b)?.to_bits()? != 0 {
// First, check x % y != 0 (or if that computation overflows).
let (res, overflow, _ty) = self.overflowing_binary_op(BinOp::Rem, a, b)?;
if overflow || res.to_bits(a.layout.size)? != 0 {
// Then, check if `b` is -1, which is the "min_value / -1" case.
let minus1 = Scalar::from_int(-1, dest.layout.size);
let b_scalar = b.to_scalar().unwrap();
Expand All @@ -421,6 +422,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
throw_ub_format!("exact_div: {} cannot be divided by {} without remainder", a, b,)
}
}
// `Rem` says this is all right, so we can let `Div` do its job.
self.binop_ignore_overflow(BinOp::Div, a, b, dest)
}
}

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