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IRGen: Don't let the offset of an empty field be undef.

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If the field address comes from a struct_element_addr which is a result of an optimized `MemoryLayout<S>.offset(of: \.field)` we cannot return undef.
We have to be consistent with `offset(of:)`, which returns 0.
Therefore we need to return the base address of the struct.

rdar://117265274
This commit is contained in:
Erik Eckstein
2024-03-11 15:21:03 +01:00
parent 761812af5f
commit c11408ea2f
3 changed files with 74 additions and 3 deletions
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10
lib/IRGen/GenStruct.cpp
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@@ -186,8 +186,14 @@ namespace {
Address projectFieldAddress(IRGenFunction &IGF, Address addr, SILType T,
VarDecl *field) const {
auto &fieldInfo = getFieldInfo(field);
if (fieldInfo.isEmpty())
return fieldInfo.getTypeInfo().getUndefAddress();
if (fieldInfo.isEmpty()) {
// For fields with empty types, we could return undef.
// But if this is a struct_element_addr which is a result of an optimized
// `MemoryLayout<S>.offset(of: \.field)` we cannot return undef. We have
// to be consistent with `offset(of:)`, which returns 0. Therefore we
// return the base address of the struct.
return addr;
}
auto offsets = asImpl().getNonFixedOffsets(IGF, T);
return fieldInfo.projectAddress(IGF, addr, offsets);