[PATCH] D149147: [LoopVectorize] Preserve SCEV

[Nikita Popov via Phabricator via llvm-commits]

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As far as I can tell, LoopVectorize preserves SCEV, mainly by dint of forgetting the loop being vectorized. We should mark it as preserved in the pass manager.

This is a very small compile-time improvement: http://llvm-compile-time-tracker.com/compare.php?from=a1677bda7975a0f690292587a04b9e053aacd1dc&to=bb3b36e5587a636f51e59a76d2e26db07ceea9ff&stat=instructions:u


https://reviews.llvm.org/D149147

Files:
  llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
  llvm/test/Transforms/LoopVectorize/novect-lcssa-cfg-invalidation.ll


Index: llvm/test/Transforms/LoopVectorize/novect-lcssa-cfg-invalidation.ll
===================================================================
--- llvm/test/Transforms/LoopVectorize/novect-lcssa-cfg-invalidation.ll
+++ llvm/test/Transforms/LoopVectorize/novect-lcssa-cfg-invalidation.ll
@@ -8,7 +8,7 @@
 define i32 @novect(ptr %p) {
 
 ; CHECK:           Running pass: LoopVectorizePass on novect
-; CHECK:           Invalidating analysis: ScalarEvolutionAnalysis on novect
+; CHECK-NOT:       Invalidating analysis: ScalarEvolutionAnalysis on novect
 ; CHECK-NOT:       Invalidating analysis: BranchProbabilityAnalysis on novect
 ; CHECK-NOT:       Invalidating analysis: BlockFrequencyAnalysis on novect
 ; CHECK:           Invalidating analysis: DemandedBitsAnalysis on novect
Index: llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
===================================================================
--- llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -10638,6 +10638,11 @@
     if (!EnableVPlanNativePath) {
       PA.preserve<LoopAnalysis>();
       PA.preserve<DominatorTreeAnalysis>();
+      PA.preserve<ScalarEvolutionAnalysis>();
+
+#ifdef EXPENSIVE_CHECKS
+      SE.verify();
+#endif
     }
 
     if (Result.MadeCFGChange) {


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