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Sanjay Patel authored
The behavior in Analysis (knownbits) implements poison semantics already, and we expect the transforms (for example, in instcombine) derived from those semantics, so this patch changes the LangRef and remaining code to be consistent. This is one more step in removing "undef" from LLVM. Without this, I think https://github.com/llvm/llvm-project/issues/53330 has a legitimate complaint because that report wants to allow subsequent code to mask off bits, and that is allowed with undef values. The clang builtins are not actually documented anywhere AFAICT, but we might want to add that to remove more uncertainty. Differential Revision: https://reviews.llvm.org/D117912
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