[GVN] When merging blocks update LoopInfo if it's available

If LoopInfo is available during GVN, BasicAA will use it.  However
MergeBlockIntoPredecessor does not update LI as it merges blocks.

This didn't use to cause problems because LI was freed before
GVN/BasicAA.  Now with OptimizationRemarkEmitter, the lifetime of LI is
extended so LI needs to be kept up-to-date during GVN.

Differential Revision: https://reviews.llvm.org/D27288

llvm-svn: 288307

1 files changed, 10 insertions, 6 deletions

diff --git a/llvm/lib/Transforms/Scalar/GVN.cpp b/llvm/lib/Transforms/Scalar/GVN.cpp
index d5234c0f7e3..79afff2fe3b 100644
--- a/llvm/lib/Transforms/Scalar/GVN.cpp
+++ b/llvm/lib/Transforms/Scalar/GVN.cpp
@@ -586,7 +586,8 @@ PreservedAnalyses GVN::run(Function &F, FunctionAnalysisManager &AM) {
   auto &TLI = AM.getResult<TargetLibraryAnalysis>(F);
   auto &AA = AM.getResult<AAManager>(F);
   auto &MemDep = AM.getResult<MemoryDependenceAnalysis>(F);
-  bool Changed = runImpl(F, AC, DT, TLI, AA, &MemDep);
+  auto *LI = AM.getCachedResult<LoopAnalysis>(F);
+  bool Changed = runImpl(F, AC, DT, TLI, AA, &MemDep, LI);
   if (!Changed)
     return PreservedAnalyses::all();
   PreservedAnalyses PA;
@@ -2179,7 +2180,7 @@ bool GVN::processInstruction(Instruction *I) {
 /// runOnFunction - This is the main transformation entry point for a function.
 bool GVN::runImpl(Function &F, AssumptionCache &RunAC, DominatorTree &RunDT,
                   const TargetLibraryInfo &RunTLI, AAResults &RunAA,
-                  MemoryDependenceResults *RunMD) {
+                  MemoryDependenceResults *RunMD, LoopInfo *LI) {
   AC = &RunAC;
   DT = &RunDT;
   VN.setDomTree(DT);
@@ -2196,9 +2197,9 @@ bool GVN::runImpl(Function &F, AssumptionCache &RunAC, DominatorTree &RunDT,
   for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ) {
     BasicBlock *BB = &*FI++;
 
-    bool removedBlock =
-        MergeBlockIntoPredecessor(BB, DT, /* LoopInfo */ nullptr, MD);
-    if (removedBlock) ++NumGVNBlocks;
+    bool removedBlock = MergeBlockIntoPredecessor(BB, DT, LI, MD);
+    if (removedBlock)
+      ++NumGVNBlocks;
 
     Changed |= removedBlock;
   }
@@ -2693,13 +2694,16 @@ public:
     if (skipFunction(F))
       return false;
 
+    auto *LIWP = getAnalysisIfAvailable<LoopInfoWrapperPass>();
+
     return Impl.runImpl(
         F, getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F),
         getAnalysis<DominatorTreeWrapperPass>().getDomTree(),
         getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(),
         getAnalysis<AAResultsWrapperPass>().getAAResults(),
         NoLoads ? nullptr
-                : &getAnalysis<MemoryDependenceWrapperPass>().getMemDep());
+                : &getAnalysis<MemoryDependenceWrapperPass>().getMemDep(),
+        LIWP ? &LIWP->getLoopInfo() : nullptr);
   }
 
   void getAnalysisUsage(AnalysisUsage &AU) const override {