mikros/rust
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Get rid of niche selection's dependence on fields's order

Browse Source
This commit is contained in:
Adwin White 2024-09-18 17:30:27 +08:00
parent f6bcd094ab
commit 9ac23dde37
2 changed files with 24 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
compiler/rustc_abi/src/layout.rs
View File

@ -527,15 +527,10 @@ struct TmpLayout<FieldIdx: Idx, VariantIdx: Idx> {
let count =
(niche_variants.end().index() as u128 - niche_variants.start().index() as u128) + 1;
// Find the field with the largest niche
let (field_index, niche, (niche_start, niche_scalar)) = variants[largest_variant_index]
.iter()
.enumerate()
.filter_map(|(j, field)| Some((j, field.largest_niche?)))
.max_by_key(|(_, niche)| niche.available(dl))
.and_then(|(j, niche)| Some((j, niche, niche.reserve(dl, count)?)))?;
let niche_offset =
niche.offset + variant_layouts[largest_variant_index].fields.offset(field_index);
// Use the largest niche in the largest variant.
let niche = variant_layouts[largest_variant_index].largest_niche?;
let (niche_start, niche_scalar) = niche.reserve(dl, count)?;
let niche_offset = niche.offset;
let niche_size = niche.value.size(dl);
let size = variant_layouts[largest_variant_index].size.align_to(align.abi);

20
tests/ui/structs-enums/type-sizes.rs
View File

@ -209,6 +209,23 @@ struct ReorderEndNiche {
b: MiddleNiche4,
}
// We want that the niche selection doesn't depend on order of the fields. See issue #125630.
pub enum NicheFieldOrder1 {
A {
x: NonZero<u64>,
y: [NonZero<u64>; 2],
},
B([u64; 2]),
}
pub enum NicheFieldOrder2 {
A {
y: [NonZero<u64>; 2],
x: NonZero<u64>,
},
B([u64; 2]),
}
// standins for std types which we want to be laid out in a reasonable way
struct RawVecDummy {
@ -260,6 +277,9 @@ pub fn main() {
size_of::<EnumWithMaybeUninhabitedVariant<()>>());
assert_eq!(size_of::<NicheFilledEnumWithAbsentVariant>(), size_of::<&'static ()>());
assert_eq!(size_of::<NicheFieldOrder1>(), 24);
assert_eq!(size_of::<NicheFieldOrder2>(), 24);
assert_eq!(size_of::<Option<Option<(bool, &())>>>(), size_of::<(bool, &())>());
assert_eq!(size_of::<Option<Option<(&(), bool)>>>(), size_of::<(bool, &())>());
assert_eq!(size_of::<Option<Option2<bool, &()>>>(), size_of::<(bool, &())>());