[llvm] [DAGCombiner] Ensure poison-generating flags are stripped in `freeze` op (PR #114582)

[Antonio Frighetto via llvm-commits]

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@@ -16151,6 +16151,7 @@ SDValue DAGCombiner::visitFREEZE(SDNode *N) {
                              SVN->getMask());
   } else {
     // NOTE: this strips poison generating flags.
+    N0->dropFlags(SDNodeFlags::PoisonGeneratingFlags);
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antoniofrighetto wrote:

getNode creates a copy, but `N0` is still the original node. It is indeed CSE'd, but the flag has been dropped by the time it gets CSE'd.

https://github.com/llvm/llvm-project/pull/114582