[PATCH] D118808: Loop Strength Reduce - Optimize unused IVs to final values in the exit block with SCEV

[Whitney Tsang via Phabricator via llvm-commits]

Whitney added a comment.

Is it possible to abstract the portion of the code in IndVarSimplify to simplify this code pattern, and call that function instead of creating your own `ReplaceExitPHIsWithFinalVal`?



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Comment at: llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp:5624
+    if (LCSSAPhi.getNumIncomingValues() != 1)
+      continue;
+
----------------
continue can change to break as all Phis in the same block should have the same number of incoming values. 


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Comment at: llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp:5644
+      continue;
+    for (auto U : IV->users()) {
+        if (U != IVNext) {
----------------
In what situation, that IV only has a single use (`IV->getNumUses() != 1`) and one of the incoming values of `IV` is `IVNext`, but `U != IVNext`?


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Comment at: llvm/test/Transforms/LoopStrengthReduce/remove_scev_indvars.ll:22
+for.exit:
+  %iv.prol.lcssa = phi i64 [ %indvars.iv.next.prol, %for.body ]
+  ret void
----------------
Do we want to also handle the case `%iv.prol.lcssa = phi i64 [ %indvars.iv.prol, %for.body ]`?


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https://reviews.llvm.org/D118808