[llvm] [InstSimplify] Make sure the simplified value doesn't generate poison in threadBinOpOverSelect (PR #87075)

[via llvm-commits]

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@@ -440,7 +440,8 @@ static Value *threadBinOpOverSelect(Instruction::BinaryOps Opcode, Value *LHS,
     // Check that the simplified value has the form "X op Y" where "op" is the
     // same as the original operation.
     Instruction *Simplified = dyn_cast<Instruction>(FV ? FV : TV);
-    if (Simplified && Simplified->getOpcode() == unsigned(Opcode)) {
+    if (Simplified && Simplified->getOpcode() == unsigned(Opcode) &&
+        !Simplified->hasPoisonGeneratingFlags()) {
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goldsteinn wrote:

why is the fix to prohibit any poison flag and not to just drop the poison generating flag?

https://github.com/llvm/llvm-project/pull/87075