[PATCH] D132443: [LSR] Fold terminating condition to other IV when possible

[Yueh-Ting (eop) Chen via Phabricator via llvm-commits]

eopXD added inline comments.


================
Comment at: llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp:6844
+
+        OldTermCond->replaceAllUsesWith(
+            PoisonValue::get(OldTermCond->getType()));
----------------
craig.topper wrote:
> What are the other users of `OldTermCond` and why is it ok to replace them with poison?
Nice catch. Added check and negative test for it.


================
Comment at: llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp:6849
+        // Cleanup the old terminating condition that is no longer used
+        // Clear the PHINode and DCE will do the rest...
+        while (ToFold->getNumIncomingValues())
----------------
craig.topper wrote:
> Is there a DCE after this? Earlier optimizations in this function used DeleteDeadPHIs to recursively clean up.
Yes. Removing the terminal condition and leveraging `DeleteDeadPHIs` is a much better approach. Thank you.


Repository:
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CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D132443/new/

https://reviews.llvm.org/D132443