[PATCH] [LoopReroll] Run LICM before Loop Rerolling.

[James Molloy]

Hi hfinkel,

Loop rerolling bails out if any value is not used by any iteration. Make sure all invariant values are hoisted first.

REPOSITORY
  rL LLVM

http://reviews.llvm.org/D7674

Files:
  lib/Transforms/IPO/PassManagerBuilder.cpp

Index: lib/Transforms/IPO/PassManagerBuilder.cpp
===================================================================
--- lib/Transforms/IPO/PassManagerBuilder.cpp
+++ lib/Transforms/IPO/PassManagerBuilder.cpp
@@ -262,8 +262,12 @@
 
   addExtensionsToPM(EP_ScalarOptimizerLate, MPM);
 
-  if (RerollLoops)
+  if (RerollLoops) {
+    // Run LICM before loop rerolling, as rerolling cannot handle any
+    // loop-invariant values at all.
+    MPM.add(createLICMPass());
     MPM.add(createLoopRerollPass());
+  }
   if (!RunSLPAfterLoopVectorization) {
     if (SLPVectorize)
       MPM.add(createSLPVectorizerPass());   // Vectorize parallel scalar chains.

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