[PATCH] D76459: [SCCP] Use SimplifyBinOp for non-integer constant/expressions & overdef.

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a comment.

The problem I see here is that InstSimplify could take a possibly-undef value, and turn it into a simple constant; then we would lose track of the fact that the value might be undef.  (For example, we transform "undef & -2 -> 0", and then incorrectly merge the result with a ConstantRange.)

For NewGVN, you're talking about https://bugs.llvm.org/show_bug.cgi?id=36335 ? I don't think that sort of issue applies here. The operand we're passing to InstSimplify is the operand of the actual operation, so any context InstSimplify could derive is the correct context. We don't try to apply the result to any other instruction.


Repository:
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  https://reviews.llvm.org/D76459/new/

https://reviews.llvm.org/D76459