[LICM] Invalidate SCEV upon instruction hoisting

Since SCEV can cache information about location of an instruction, it should be invalidated when the instruction is moved.
There should be similar bug in code sinking part of LICM, it will be fixed in a follow-up change.

Patch Author: Daniil Suchkov
Reviewers: asbirlea, mkazantsev, reames
Reviewed By: asbirlea
Subscribers: hiraditya, javed.absar, llvm-commits
Differential Revision: https://reviews.llvm.org/D69370

llvm/include/llvm/Transforms/Utils/LoopUtils.h

@@ -133,7 +133,7 @@ bool sinkRegion(DomTreeNode *, AliasAnalysis *, LoopInfo *, DominatorTree *,
 /// ORE. It returns changed status.
 bool hoistRegion(DomTreeNode *, AliasAnalysis *, LoopInfo *, DominatorTree *,
                  TargetLibraryInfo *, Loop *, AliasSetTracker *,
-                 MemorySSAUpdater *, ICFLoopSafetyInfo *,
+                 MemorySSAUpdater *, ScalarEvolution *, ICFLoopSafetyInfo *,
                  SinkAndHoistLICMFlags &, OptimizationRemarkEmitter *);
 
 /// This function deletes dead loops. The caller of this function needs to

llvm/lib/Transforms/Scalar/LICM.cpp

@@ -137,7 +137,8 @@ static bool isNotUsedOrFreeInLoop(const Instruction &I, const Loop *CurLoop,
                                   TargetTransformInfo *TTI, bool &FreeInLoop);
 static void hoist(Instruction &I, const DominatorTree *DT, const Loop *CurLoop,
                   BasicBlock *Dest, ICFLoopSafetyInfo *SafetyInfo,
-                  MemorySSAUpdater *MSSAU, OptimizationRemarkEmitter *ORE);
+                  MemorySSAUpdater *MSSAU, ScalarEvolution *SE,
+                  OptimizationRemarkEmitter *ORE);
 static bool sink(Instruction &I, LoopInfo *LI, DominatorTree *DT,
                  const Loop *CurLoop, ICFLoopSafetyInfo *SafetyInfo,
                  MemorySSAUpdater *MSSAU, OptimizationRemarkEmitter *ORE);
@@ -162,7 +163,7 @@ static void eraseInstruction(Instruction &I, ICFLoopSafetyInfo &SafetyInfo,
 
 static void moveInstructionBefore(Instruction &I, Instruction &Dest,
                                   ICFLoopSafetyInfo &SafetyInfo,
-                                  MemorySSAUpdater *MSSAU);
+                                  MemorySSAUpdater *MSSAU, ScalarEvolution *SE);
 
 namespace {
 struct LoopInvariantCodeMotion {
@@ -390,8 +391,9 @@ bool LoopInvariantCodeMotion::runOnLoop(
                           CurAST.get(), MSSAU.get(), &SafetyInfo, Flags, ORE);
   Flags.IsSink = false;
   if (Preheader)
-    Changed |= hoistRegion(DT->getNode(L->getHeader()), AA, LI, DT, TLI, L,
-                           CurAST.get(), MSSAU.get(), &SafetyInfo, Flags, ORE);
+    Changed |=
+        hoistRegion(DT->getNode(L->getHeader()), AA, LI, DT, TLI, L,
+                    CurAST.get(), MSSAU.get(), SE, &SafetyInfo, Flags, ORE);
 
   // Now that all loop invariants have been removed from the loop, promote any
   // memory references to scalars that we can.
@@ -795,7 +797,7 @@ class ControlFlowHoister {
 bool llvm::hoistRegion(DomTreeNode *N, AliasAnalysis *AA, LoopInfo *LI,
                        DominatorTree *DT, TargetLibraryInfo *TLI, Loop *CurLoop,
                        AliasSetTracker *CurAST, MemorySSAUpdater *MSSAU,
-                       ICFLoopSafetyInfo *SafetyInfo,
+                       ScalarEvolution *SE, ICFLoopSafetyInfo *SafetyInfo,
                        SinkAndHoistLICMFlags &Flags,
                        OptimizationRemarkEmitter *ORE) {
   // Verify inputs.
@@ -855,7 +857,7 @@ bool llvm::hoistRegion(DomTreeNode *N, AliasAnalysis *AA, LoopInfo *LI,
               I, DT, CurLoop, SafetyInfo, ORE,
               CurLoop->getLoopPreheader()->getTerminator())) {
         hoist(I, DT, CurLoop, CFH.getOrCreateHoistedBlock(BB), SafetyInfo,
-              MSSAU, ORE);
+              MSSAU, SE, ORE);
         HoistedInstructions.push_back(&I);
         Changed = true;
         continue;
@@ -882,7 +884,7 @@ bool llvm::hoistRegion(DomTreeNode *N, AliasAnalysis *AA, LoopInfo *LI,
         eraseInstruction(I, *SafetyInfo, CurAST, MSSAU);
 
         hoist(*ReciprocalDivisor, DT, CurLoop, CFH.getOrCreateHoistedBlock(BB),
-              SafetyInfo, MSSAU, ORE);
+              SafetyInfo, MSSAU, SE, ORE);
         HoistedInstructions.push_back(ReciprocalDivisor);
         Changed = true;
         continue;
@@ -901,7 +903,7 @@ bool llvm::hoistRegion(DomTreeNode *N, AliasAnalysis *AA, LoopInfo *LI,
           CurLoop->hasLoopInvariantOperands(&I) &&
           MustExecuteWithoutWritesBefore(I)) {
         hoist(I, DT, CurLoop, CFH.getOrCreateHoistedBlock(BB), SafetyInfo,
-              MSSAU, ORE);
+              MSSAU, SE, ORE);
         HoistedInstructions.push_back(&I);
         Changed = true;
         continue;
@@ -915,7 +917,7 @@ bool llvm::hoistRegion(DomTreeNode *N, AliasAnalysis *AA, LoopInfo *LI,
             PN->setIncomingBlock(
                 i, CFH.getOrCreateHoistedBlock(PN->getIncomingBlock(i)));
           hoist(*PN, DT, CurLoop, CFH.getOrCreateHoistedBlock(BB), SafetyInfo,
-                MSSAU, ORE);
+                MSSAU, SE, ORE);
           assert(DT->dominates(PN, BB) && "Conditional PHIs not expected");
           Changed = true;
           continue;
@@ -952,7 +954,7 @@ bool llvm::hoistRegion(DomTreeNode *N, AliasAnalysis *AA, LoopInfo *LI,
         LLVM_DEBUG(dbgs() << "LICM rehoisting to "
                           << HoistPoint->getParent()->getName()
                           << ": " << *I << "\n");
-        moveInstructionBefore(*I, *HoistPoint, *SafetyInfo, MSSAU);
+        moveInstructionBefore(*I, *HoistPoint, *SafetyInfo, MSSAU, SE);
         HoistPoint = I;
         Changed = true;
       }
@@ -1441,14 +1443,17 @@ static void eraseInstruction(Instruction &I, ICFLoopSafetyInfo &SafetyInfo,
 
 static void moveInstructionBefore(Instruction &I, Instruction &Dest,
                                   ICFLoopSafetyInfo &SafetyInfo,
-                                  MemorySSAUpdater *MSSAU) {
+                                  MemorySSAUpdater *MSSAU,
+                                  ScalarEvolution *SE) {
   SafetyInfo.removeInstruction(&I);
   SafetyInfo.insertInstructionTo(&I, Dest.getParent());
   I.moveBefore(&Dest);
   if (MSSAU)
     if (MemoryUseOrDef *OldMemAcc = cast_or_null<MemoryUseOrDef>(
             MSSAU->getMemorySSA()->getMemoryAccess(&I)))
       MSSAU->moveToPlace(OldMemAcc, Dest.getParent(), MemorySSA::End);
+  if (SE)
+    SE->forgetValue(&I);
 }
 
 static Instruction *sinkThroughTriviallyReplaceablePHI(
@@ -1662,7 +1667,8 @@ static bool sink(Instruction &I, LoopInfo *LI, DominatorTree *DT,
 ///
 static void hoist(Instruction &I, const DominatorTree *DT, const Loop *CurLoop,
                   BasicBlock *Dest, ICFLoopSafetyInfo *SafetyInfo,
-                  MemorySSAUpdater *MSSAU, OptimizationRemarkEmitter *ORE) {
+                  MemorySSAUpdater *MSSAU, ScalarEvolution *SE,
+                  OptimizationRemarkEmitter *ORE) {
   LLVM_DEBUG(dbgs() << "LICM hoisting to " << Dest->getName() << ": " << I
                     << "\n");
   ORE->emit([&]() {
@@ -1683,10 +1689,10 @@ static void hoist(Instruction &I, const DominatorTree *DT, const Loop *CurLoop,
 
   if (isa<PHINode>(I))
     // Move the new node to the end of the phi list in the destination block.
-    moveInstructionBefore(I, *Dest->getFirstNonPHI(), *SafetyInfo, MSSAU);
+    moveInstructionBefore(I, *Dest->getFirstNonPHI(), *SafetyInfo, MSSAU, SE);
   else
     // Move the new node to the destination block, before its terminator.
-    moveInstructionBefore(I, *Dest->getTerminator(), *SafetyInfo, MSSAU);
+    moveInstructionBefore(I, *Dest->getTerminator(), *SafetyInfo, MSSAU, SE);
 
   // Apply line 0 debug locations when we are moving instructions to different
   // basic blocks because we want to avoid jumpy line tables.

llvm/unittests/Transforms/Scalar/LICMTest.cpp

@@ -86,10 +86,8 @@ TEST(LICMTest, TestSCEVInvalidationOnHoisting) {
   // If LICM have properly invalidated SCEV,
   //   1. SCEV of <load i64, i64* %ptr> should properly dominate the "loop" BB,
   //   2. extra invalidation shouldn't change result of the query.
-  // FIXME: these values should be equal!
-  EXPECT_NE(DispositionBeforeInvalidation,
+  EXPECT_EQ(DispositionBeforeInvalidation,
             ScalarEvolution::BlockDisposition::ProperlyDominatesBlock);
-  // FIXME: these values should be equal!
-  EXPECT_NE(DispositionBeforeInvalidation, DispositionAfterInvalidation);
+  EXPECT_EQ(DispositionBeforeInvalidation, DispositionAfterInvalidation);
 }
 }