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[Clang][CodeGen] Fix bad codegen when building Clang with latest MSVC #102681

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merged 2 commits into from
Aug 10, 2024
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[Clang][CodeGen] Fix bad codegen when building Clang with latest MSVC #102681

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[Clang][CodeGen] Fix a bad codegen when building Clang with latest MSVC
aganea Aug 9, 2024
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aganea Aug 10, 2024
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13 changes: 9 additions & 4 deletions clang/lib/CodeGen/CGObjCGNU.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2092,10 +2092,15 @@ class CGObjCGNUstep2 : public CGObjCGNUstep {
auto *classStart =
llvm::StructType::get(PtrTy, PtrTy, PtrTy, LongTy, LongTy);
auto &astContext = CGM.getContext();
auto flags = Builder.CreateLoad(
Address{Builder.CreateStructGEP(classStart, selfValue, 4), LongTy,
CharUnits::fromQuantity(
astContext.getTypeAlign(astContext.UnsignedLongTy))});
// FIXME: The following few lines up to and including the call to
// `CreateLoad` were known to miscompile when MSVC 19.40.33813 is used
// to build Clang. When the bug is fixed in future MSVC releases, we
// should revert these lines to their previous state. See discussion in
// https://github.com/llvm/llvm-project/pull/102681
llvm::Value *Val = Builder.CreateStructGEP(classStart, selfValue, 4);
auto Align = CharUnits::fromQuantity(
astContext.getTypeAlign(astContext.UnsignedLongTy));
auto flags = Builder.CreateLoad(Address{Val, LongTy, Align});
auto isInitialized =
Builder.CreateAnd(flags, ClassFlags::ClassFlagInitialized);
llvm::BasicBlock *notInitializedBlock =
Expand Down