[LoopSimplifyCFG] Invalidate SCEV in LoopSimplifyCFG

LoopSimplifyCFG, being a loop pass, needs to preserve scalar
evolution. This invalidates SE for the loops altered during
block merging.

Differential Revision: https://reviews.llvm.org/D48258

llvm-svn: 335036

1 files changed, 7 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/Scalar/LoopSimplifyCFG.cpp b/llvm/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
index c6d037359f0..49de71e5119 100644
--- a/llvm/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
@@ -37,7 +37,8 @@ using namespace llvm;
 
 #define DEBUG_TYPE "loop-simplifycfg"
 
-static bool simplifyLoopCFG(Loop &L, DominatorTree &DT, LoopInfo &LI) {
+static bool simplifyLoopCFG(Loop &L, DominatorTree &DT, LoopInfo &LI,
+                            ScalarEvolution &SE) {
   bool Changed = false;
   // Copy blocks into a temporary array to avoid iterator invalidation issues
   // as we remove them.
@@ -59,6 +60,8 @@ static bool simplifyLoopCFG(Loop &L, DominatorTree &DT, LoopInfo &LI) {
       L.moveToHeader(Succ);
     LI.removeBlock(Pred);
     MergeBasicBlockIntoOnlyPred(Succ, &DT);
+
+    SE.forgetLoop(&L);
     Changed = true;
   }
 
@@ -68,7 +71,7 @@ static bool simplifyLoopCFG(Loop &L, DominatorTree &DT, LoopInfo &LI) {
 PreservedAnalyses LoopSimplifyCFGPass::run(Loop &L, LoopAnalysisManager &AM,
                                            LoopStandardAnalysisResults &AR,
                                            LPMUpdater &) {
-  if (!simplifyLoopCFG(L, AR.DT, AR.LI))
+  if (!simplifyLoopCFG(L, AR.DT, AR.LI, AR.SE))
     return PreservedAnalyses::all();
 
   return getLoopPassPreservedAnalyses();
@@ -88,7 +91,8 @@ public:
 
     DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
     LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
-    return simplifyLoopCFG(*L, DT, LI);
+    ScalarEvolution &SE = getAnalysis<ScalarEvolutionWrapperPass>().getSE();
+    return simplifyLoopCFG(*L, DT, LI, SE);
   }
 
   void getAnalysisUsage(AnalysisUsage &AU) const override {