[GVN] Always require LoopInfo

GVN behavior depends on LoopInfo in multiple ways, most notably
as a dependency for loop load PRE. As this is not a preserved-only
analysis, using a cached analysis is inappropriate.

In the actual optimization pipeline LoopInfo is always available
at the point GVN runs, but this will ensure it stays this way
even if the pipeline changes.

Author: nikic

llvm/include/llvm/Transforms/Scalar/GVN.h

@@ -261,7 +261,7 @@ class GVNPass : public PassInfoMixin<GVNPass> {
 
   bool runImpl(Function &F, AssumptionCache &RunAC, DominatorTree &RunDT,
                const TargetLibraryInfo &RunTLI, AAResults &RunAA,
-               MemoryDependenceResults *RunMD, LoopInfo *LI,
+               MemoryDependenceResults *RunMD, LoopInfo &LI,
                OptimizationRemarkEmitter *ORE, MemorySSA *MSSA = nullptr);
 
   /// Push a new Value to the LeaderTable onto the list for its value number.

llvm/lib/Transforms/Scalar/GVN.cpp

@@ -760,7 +760,7 @@ PreservedAnalyses GVNPass::run(Function &F, FunctionAnalysisManager &AM) {
   auto &AA = AM.getResult<AAManager>(F);
   auto *MemDep =
       isMemDepEnabled() ? &AM.getResult<MemoryDependenceAnalysis>(F) : nullptr;
-  auto *LI = AM.getCachedResult<LoopAnalysis>(F);
+  auto &LI = AM.getResult<LoopAnalysis>(F);
   auto *MSSA = AM.getCachedResult<MemorySSAAnalysis>(F);
   auto &ORE = AM.getResult<OptimizationRemarkEmitterAnalysis>(F);
   bool Changed = runImpl(F, AC, DT, TLI, AA, MemDep, LI, &ORE,
@@ -772,8 +772,7 @@ PreservedAnalyses GVNPass::run(Function &F, FunctionAnalysisManager &AM) {
   PA.preserve<TargetLibraryAnalysis>();
   if (MSSA)
     PA.preserve<MemorySSAAnalysis>();
-  if (LI)
-    PA.preserve<LoopAnalysis>();
+  PA.preserve<LoopAnalysis>();
   return PA;
 }
 
@@ -1434,8 +1433,7 @@ void GVNPass::eliminatePartiallyRedundantLoad(
     if (auto *RangeMD = Load->getMetadata(LLVMContext::MD_range))
       NewLoad->setMetadata(LLVMContext::MD_range, RangeMD);
     if (auto *AccessMD = Load->getMetadata(LLVMContext::MD_access_group))
-      if (LI &&
-          LI->getLoopFor(Load->getParent()) == LI->getLoopFor(UnavailableBlock))
+      if (LI->getLoopFor(Load->getParent()) == LI->getLoopFor(UnavailableBlock))
         NewLoad->setMetadata(LLVMContext::MD_access_group, AccessMD);
 
     // We do not propagate the old load's debug location, because the new
@@ -1743,9 +1741,6 @@ bool GVNPass::PerformLoadPRE(LoadInst *Load, AvailValInBlkVect &ValuesPerBlock,
 bool GVNPass::performLoopLoadPRE(LoadInst *Load,
                                  AvailValInBlkVect &ValuesPerBlock,
                                  UnavailBlkVect &UnavailableBlocks) {
-  if (!LI)
-    return false;
-
   const Loop *L = LI->getLoopFor(Load->getParent());
   // TODO: Generalize to other loop blocks that dominate the latch.
   if (!L || L->getHeader() != Load->getParent())
@@ -1914,7 +1909,7 @@ bool GVNPass::processNonLocalLoad(LoadInst *Load) {
   // Step 4: Eliminate partial redundancy.
   if (!isPREEnabled() || !isLoadPREEnabled())
     return Changed;
-  if (!isLoadInLoopPREEnabled() && LI && LI->getLoopFor(Load->getParent()))
+  if (!isLoadInLoopPREEnabled() && LI->getLoopFor(Load->getParent()))
     return Changed;
 
   if (performLoopLoadPRE(Load, ValuesPerBlock, UnavailableBlocks) ||
@@ -2686,7 +2681,7 @@ bool GVNPass::processInstruction(Instruction *I) {
 /// runOnFunction - This is the main transformation entry point for a function.
 bool GVNPass::runImpl(Function &F, AssumptionCache &RunAC, DominatorTree &RunDT,
                       const TargetLibraryInfo &RunTLI, AAResults &RunAA,
-                      MemoryDependenceResults *RunMD, LoopInfo *LI,
+                      MemoryDependenceResults *RunMD, LoopInfo &LI,
                       OptimizationRemarkEmitter *RunORE, MemorySSA *MSSA) {
   AC = &RunAC;
   DT = &RunDT;
@@ -2696,7 +2691,7 @@ bool GVNPass::runImpl(Function &F, AssumptionCache &RunAC, DominatorTree &RunDT,
   MD = RunMD;
   ImplicitControlFlowTracking ImplicitCFT;
   ICF = &ImplicitCFT;
-  this->LI = LI;
+  this->LI = &LI;
   VN.setMemDep(MD);
   ORE = RunORE;
   InvalidBlockRPONumbers = true;
@@ -2710,7 +2705,7 @@ bool GVNPass::runImpl(Function &F, AssumptionCache &RunAC, DominatorTree &RunDT,
   // Merge unconditional branches, allowing PRE to catch more
   // optimization opportunities.
   for (BasicBlock &BB : llvm::make_early_inc_range(F)) {
-    bool removedBlock = MergeBlockIntoPredecessor(&BB, &DTU, LI, MSSAU, MD);
+    bool removedBlock = MergeBlockIntoPredecessor(&BB, &DTU, &LI, MSSAU, MD);
     if (removedBlock)
       ++NumGVNBlocks;
 
@@ -3286,8 +3281,6 @@ class llvm::gvn::GVNLegacyPass : public FunctionPass {
     if (skipFunction(F))
       return false;
 
-    auto &LIWP = getAnalysis<LoopInfoWrapperPass>();
-
     auto *MSSAWP = getAnalysisIfAvailable<MemorySSAWrapperPass>();
     return Impl.runImpl(
         F, getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F),
@@ -3297,7 +3290,7 @@ class llvm::gvn::GVNLegacyPass : public FunctionPass {
         Impl.isMemDepEnabled()
             ? &getAnalysis<MemoryDependenceWrapperPass>().getMemDep()
             : nullptr,
-        &LIWP.getLoopInfo(),
+        getAnalysis<LoopInfoWrapperPass>().getLoopInfo(),
         &getAnalysis<OptimizationRemarkEmitterWrapperPass>().getORE(),
         MSSAWP ? &MSSAWP->getMSSA() : nullptr);
   }