bjoernager/rust
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ignore zst offsets instead

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This commit is contained in:
Erik Desjardins 2020-08-16 19:25:39 -04:00
parent e9bc3ddb07
commit 68217c9e0f
2 changed files with 78 additions and 89 deletions
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32
compiler/rustc_codegen_ssa/src/mir/place.rs
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@ -93,15 +93,29 @@ impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
let effective_field_align = self.align.restrict_for_offset(offset);
let mut simple = || {
// Unions and newtypes only use an offset of 0.
let llval = if offset.bytes() == 0 {
self.llval
} else if let Abi::ScalarPair(ref a, ref b) = self.layout.abi {
// Offsets have to match either first or second field.
assert_eq!(offset, a.value.size(bx.cx()).align_to(b.value.align(bx.cx()).abi));
bx.struct_gep(self.llval, 1)
} else {
bx.struct_gep(self.llval, bx.cx().backend_field_index(self.layout, ix))
let llval = match self.layout.abi {
_ if offset.bytes() == 0 => {
// Unions and newtypes only use an offset of 0.
// Also handles the first field of Scalar and ScalarPair layouts.
self.llval
}
Abi::ScalarPair(ref a, ref b)
if offset == a.value.size(bx.cx()).align_to(b.value.align(bx.cx()).abi) =>
{
// Offset matches second field.
bx.struct_gep(self.llval, 1)
}
Abi::ScalarPair(..) | Abi::Scalar(_) => {
// ZST fields are not included in Scalar and ScalarPair layouts, so manually offset the pointer.
assert!(
field.is_zst(),
"non-ZST field offset does not match layout: {:?}",
field
);
let byte_ptr = bx.pointercast(self.llval, bx.cx().type_i8p());
bx.gep(byte_ptr, &[bx.const_usize(offset.bytes())])
}
_ => bx.struct_gep(self.llval, bx.cx().backend_field_index(self.layout, ix)),
};
PlaceRef {
// HACK(eddyb): have to bitcast pointers until LLVM removes pointee types.