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Don't cache projection if no padding is used.

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In this case we can just return memory_index(index) which is readily available.
This commit is contained in:
Hans Kratz 2021-07-20 07:38:00 +02:00
parent e4106581de
commit e89908231b
1 changed files with 6 additions and 4 deletions
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10
compiler/rustc_codegen_llvm/src/type_of.rs
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@ -99,6 +99,7 @@ fn struct_llfields<'a, 'tcx>(
let mut prev_effective_align = layout.align.abi; let mut prev_effective_align = layout.align.abi;
let mut result: Vec<_> = Vec::with_capacity(1 + field_count * 2); let mut result: Vec<_> = Vec::with_capacity(1 + field_count * 2);
let mut projection = vec![0; field_count]; let mut projection = vec![0; field_count];
let mut padding_used = false;
for i in layout.fields.index_by_increasing_offset() { for i in layout.fields.index_by_increasing_offset() {
let target_offset = layout.fields.offset(i as usize); let target_offset = layout.fields.offset(i as usize);
let field = layout.field(cx, i); let field = layout.field(cx, i);
@ -118,6 +119,7 @@ fn struct_llfields<'a, 'tcx>(
assert!(target_offset >= offset); assert!(target_offset >= offset);
let padding = target_offset - offset; let padding = target_offset - offset;
if padding != Size::ZERO { if padding != Size::ZERO {
padding_used = true;
let padding_align = prev_effective_align.min(effective_field_align); let padding_align = prev_effective_align.min(effective_field_align);
assert_eq!(offset.align_to(padding_align) + padding, target_offset); assert_eq!(offset.align_to(padding_align) + padding, target_offset);
result.push(cx.type_padding_filler(padding, padding_align)); result.push(cx.type_padding_filler(padding, padding_align));
@ -145,7 +147,9 @@ fn struct_llfields<'a, 'tcx>(
} else { } else {
debug!("struct_llfields: offset: {:?} stride: {:?}", offset, layout.size); debug!("struct_llfields: offset: {:?} stride: {:?}", offset, layout.size);
} }
cx.field_projection_cache.borrow_mut().insert(layout, projection); if padding_used {
cx.field_projection_cache.borrow_mut().insert(layout, projection);
}
(result, packed) (result, packed)
} }
@ -361,9 +365,7 @@ impl<'tcx> LayoutLlvmExt<'tcx> for TyAndLayout<'tcx> {
FieldsShape::Arbitrary { .. } => match cx.field_projection_cache.borrow().get(self) { FieldsShape::Arbitrary { .. } => match cx.field_projection_cache.borrow().get(self) {
Some(projection) => projection[index] as u64, Some(projection) => projection[index] as u64,
None => { None => self.fields.memory_index(index) as u64,
bug!("TyAndLayout::llvm_field_index({:?}): field projection not cached", self)
}
}, },
} }
} }