[Bug] GVNPass incorrectly considered as uninitialized

[Zhenhang1213]

In this demo, hook_param has been memset, but in GVNPass , clang consideres hook_param.flags is uninitialized.

llvm-project/llvm/lib/IR/ConstantFold.cpp

Lines 676 to 678 in 6f241e3

	case Instruction::Or: // X | undef -> -1
	if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef | undef -> undef
	return C1;

https://godbolt.org/z/83nMW8M8o

[nikic]

From a cursory look, probably because your code violates strict aliasing rules and is UB. It works with -fno-strict-aliasing.