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simplify common prim computation

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This commit is contained in:
Erik Desjardins 2024-02-28 17:55:04 -05:00
parent 4dabbcb23b
commit f574c65147
1 changed files with 9 additions and 16 deletions
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25
compiler/rustc_abi/src/layout.rs
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@ -813,7 +813,7 @@ where
break;
}
};
if let Some((old_common_prim, common_offset)) = common_prim {
if let Some((old_prim, common_offset)) = common_prim {
// All variants must be at the same offset
if offset != common_offset {
common_prim = None;
@ -822,12 +822,12 @@ where
// This is pretty conservative. We could go fancier
// by realising that (u8, u8) could just cohabit with
// u16 or even u32.
let new_common_prim = match (old_common_prim, prim) {
let new_prim = match (old_prim, prim) {
// Allow all identical primitives.
(x, y) if x == y => Some(x),
(x, y) if x == y => x,
// Allow integers of the same size with differing signedness.
// We arbitrarily choose the signedness of the first variant.
(p @ Primitive::Int(x, _), Primitive::Int(y, _)) if x == y => Some(p),
(p @ Primitive::Int(x, _), Primitive::Int(y, _)) if x == y => p,
// Allow integers mixed with pointers of the same layout.
// We must represent this using a pointer, to avoid
// roundtripping pointers through ptrtoint/inttoptr.
@ -835,22 +835,15 @@ where
| (i @ Primitive::Int(..), p @ Primitive::Pointer(_))
if p.size(dl) == i.size(dl) && p.align(dl) == i.align(dl) =>
{
Some(p)
p
}
_ => None,
};
match new_common_prim {
Some(new_prim) => {
// Primitives are compatible.
// We may be updating the primitive here, for example from int->ptr.
common_prim = Some((new_prim, common_offset));
}
None => {
// Primitives are incompatible.
_ => {
common_prim = None;
break;
}
}
};
// We may be updating the primitive here, for example from int->ptr.
common_prim = Some((new_prim, common_offset));
} else {
common_prim = Some((prim, offset));
}