Make LoopUnswitch preserve ScalarEvolution by just forgetting everything about

a loop when unswitching it. It only does this in the complex case, because
everything should be fine already in the simple case.

llvm-svn: 125369

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp b/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp
index 0fc416d6746..b4e3d318a57 100644
--- a/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp
@@ -37,6 +37,7 @@
 #include "llvm/Analysis/LoopInfo.h"
 #include "llvm/Analysis/LoopPass.h"
 #include "llvm/Analysis/Dominators.h"
+#include "llvm/Analysis/ScalarEvolution.h"
 #include "llvm/Transforms/Utils/Cloning.h"
 #include "llvm/Transforms/Utils/Local.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
@@ -110,6 +111,7 @@ namespace {
       AU.addRequiredID(LCSSAID);
       AU.addPreservedID(LCSSAID);
       AU.addPreserved<DominatorTree>();
+      AU.addPreserved<ScalarEvolution>();
     }
 
   private:
@@ -574,6 +576,9 @@ void LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val,
         << " blocks] in Function " << F->getName()
         << " when '" << *Val << "' == " << *LIC << "\n");
 
+  if (ScalarEvolution *SE = getAnalysisIfAvailable<ScalarEvolution>())
+    SE->forgetLoop(L);
+
   LoopBlocks.clear();
   NewBlocks.clear();