bjoernager/rust
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compiler: split vector_align into cabi and llvmlike

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Introduce a pair of functions that actually describe what they do,
because it wasn't clear the alignment is sometimes a forgery.
This commit is contained in:
Jubilee Young 2025-02-19 14:53:31 -08:00
parent 5c474fd99b
commit 79f41c773a
3 changed files with 20 additions and 12 deletions
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2
compiler/rustc_abi/src/callconv/reg.rs
View file

@ -57,7 +57,7 @@ impl Reg {
128 => dl.f128_align.abi,
_ => panic!("unsupported float: {self:?}"),
},
RegKind::Vector => dl.vector_align(self.size).abi,
RegKind::Vector => dl.llvmlike_vector_align(self.size).abi,
}
}
}

23
compiler/rustc_abi/src/lib.rs
View file

@ -408,16 +408,21 @@ impl TargetDataLayout {
}
}
/// psABI-mandated alignment for a vector type, if any
#[inline]
pub fn vector_align(&self, vec_size: Size) -> AbiAndPrefAlign {
for &(size, align) in &self.vector_align {
if size == vec_size {
return align;
}
}
// Default to natural alignment, which is what LLVM does.
// That is, use the size, rounded up to a power of 2.
AbiAndPrefAlign::new(Align::from_bytes(vec_size.bytes().next_power_of_two()).unwrap())
fn cabi_vector_align(&self, vec_size: Size) -> Option<AbiAndPrefAlign> {
self.vector_align
.iter()
.find(|(size, _align)| *size == vec_size)
.map(|(_size, align)| *align)
}
/// an alignment resembling the one LLVM would pick for a vector
#[inline]
pub fn llvmlike_vector_align(&self, vec_size: Size) -> AbiAndPrefAlign {
self.cabi_vector_align(vec_size).unwrap_or(AbiAndPrefAlign::new(
Align::from_bytes(vec_size.bytes().next_power_of_two()).unwrap(),
))
}
}