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Rollup merge of #70437 - RalfJung:miri-saturate, r=hanna-kruppe

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Miri float->int casts: be explicit that this is saturating

r? @hanna-kruppe
Cc https://github.com/rust-lang/miri/issues/1264
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Dylan DPC 2020-03-26 21:44:09 +01:00 committed by GitHub
commit 195147c7ae
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src/librustc_mir/interpret/cast.rs
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@ -229,6 +229,8 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
// float -> uint
Uint(t) => {
let width = t.bit_width().unwrap_or_else(|| self.pointer_size().bits());
// `to_u128` is a saturating cast, which is what we need
// (https://doc.rust-lang.org/nightly/nightly-rustc/rustc_apfloat/trait.Float.html#method.to_i128_r).
let v = f.to_u128(usize::try_from(width).unwrap()).value;
// This should already fit the bit width
Ok(Scalar::from_uint(v, Size::from_bits(width)))
@ -236,6 +238,8 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
// float -> int
Int(t) => {
let width = t.bit_width().unwrap_or_else(|| self.pointer_size().bits());
// `to_i128` is a saturating cast, which is what we need
// (https://doc.rust-lang.org/nightly/nightly-rustc/rustc_apfloat/trait.Float.html#method.to_i128_r).
let v = f.to_i128(usize::try_from(width).unwrap()).value;
Ok(Scalar::from_int(v, Size::from_bits(width)))
}