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Auto merge of #49383 - nox:scalarpair, r=eddyb

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Allow niche-filling dataful variants to be represented as a ScalarPair

r? @eddyb
This commit is contained in:
bors 2018-03-28 08:01:22 +00:00
commit bcffdf1b6d
2 changed files with 21 additions and 4 deletions
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19
src/librustc/ty/layout.rs
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@ -1517,10 +1517,21 @@ impl<'a, 'tcx> LayoutCx<'tcx, TyCtxt<'a, 'tcx, 'tcx>> {
let offset = st[i].fields.offset(field_index) + offset;
let size = st[i].size;
let abi = if offset.bytes() == 0 && niche.value.size(dl) == size {
Abi::Scalar(niche.clone())
} else {
Abi::Aggregate { sized: true }
let abi = match st[i].abi {
Abi::Scalar(_) => Abi::Scalar(niche.clone()),
Abi::ScalarPair(ref first, ref second) => {
// We need to use scalar_unit to reset the
// valid range to the maximal one for that
// primitive, because only the niche is
// guaranteed to be initialised, not the
// other primitive.
if offset.bytes() == 0 {
Abi::ScalarPair(niche.clone(), scalar_unit(second.value))
} else {
Abi::ScalarPair(scalar_unit(first.value), niche.clone())
}
}
_ => Abi::Aggregate { sized: true },
};
return Ok(tcx.intern_layout(LayoutDetails {