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Auto merge of #55701 - tromey:ice-fix, r=matthewjasper

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Fix emission of niche-filling discriminant values

Bug #55606 points out a regression introduced by #54004; namely that
an assertion can erroneously fire when a niche-filling discriminant
value is emitted.

This fixes the bug by removing the assertion, and furthermore by
arranging for the discriminant value to be masked according to the
size of the niche.  This makes handling the discriminant a bit simpler
for debuggers.

The test case is from Jonathan Turner.

Closes #55606
This commit is contained in:
bors 2018-11-12 04:12:26 +00:00
commit d1d79ae3ad
2 changed files with 67 additions and 4 deletions
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8
src/librustc_codegen_llvm/debuginfo/metadata.rs
View file

@ -1279,7 +1279,7 @@ impl EnumMemberDescriptionFactory<'ll, 'tcx> {
niche_start,
ref variants,
dataful_variant,
..
ref niche,
} => {
if fallback {
let variant = self.layout.for_variant(cx, dataful_variant);
@ -1361,11 +1361,11 @@ impl EnumMemberDescriptionFactory<'ll, 'tcx> {
let niche_value = if i == dataful_variant {
None
} else {
let niche = (i as u128)
let value = (i as u128)
.wrapping_sub(*niche_variants.start() as u128)
.wrapping_add(niche_start);
assert_eq!(niche as u64 as u128, niche);
Some(niche as u64)
let value = value & ((1u128 << niche.value.size(cx).bits()) - 1);
Some(value as u64)
};
MemberDescription {