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group fields based on largest power of two dividing its size

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The 8472 2022-10-06 23:34:50 +02:00
parent 9f0cb566ea
commit a3450d060d
1 changed files with 3 additions and 7 deletions
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10
compiler/rustc_ty_utils/src/layout.rs
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@ -140,14 +140,10 @@ fn univariant_uninterned<'tcx>(
let optimizing = &mut inverse_memory_index[..end];
let effective_field_align = |f: &TyAndLayout<'_>| {
if let Some(pack) = pack {
f.align.abi.min(pack)
} else if f.size.bytes().is_power_of_two() && f.size.bytes() >= f.align.abi.bytes() {
// Try to put fields which have a 2^n size and smaller alignment together with
// fields that have an alignment matching that size.
// E.g. group [u8; 4] with u32 fields
Align::from_bytes(f.align.abi.bytes()).unwrap_or(f.align.abi)
f.align.abi.min(pack).bytes()
} else {
f.align.abi
// group [u8; 4] with align-4 or [u8; 6] with align-2 fields
f.align.abi.bytes().max(f.size.bytes()).trailing_zeros() as u64
}
};