[IndVarSimplify] Teach IndVarSimplify to preserve MemorySSA.

Author: alinas

llvm/lib/Transforms/Scalar/IndVarSimplify.cpp

@@ -38,6 +38,8 @@
 #include "llvm/ADT/iterator_range.h"
 #include "llvm/Analysis/LoopInfo.h"
 #include "llvm/Analysis/LoopPass.h"
+#include "llvm/Analysis/MemorySSA.h"
+#include "llvm/Analysis/MemorySSAUpdater.h"
 #include "llvm/Analysis/ScalarEvolution.h"
 #include "llvm/Analysis/ScalarEvolutionExpander.h"
 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
@@ -138,6 +140,8 @@ class IndVarSimplify {
   const DataLayout &DL;
   TargetLibraryInfo *TLI;
   const TargetTransformInfo *TTI;
+  MemorySSA *MSSA;
+  std::unique_ptr<MemorySSAUpdater> MSSAU;
 
   SmallVector<WeakTrackingVH, 16> DeadInsts;
 
@@ -162,8 +166,11 @@ class IndVarSimplify {
 public:
   IndVarSimplify(LoopInfo *LI, ScalarEvolution *SE, DominatorTree *DT,
                  const DataLayout &DL, TargetLibraryInfo *TLI,
-                 TargetTransformInfo *TTI)
-      : LI(LI), SE(SE), DT(DT), DL(DL), TLI(TLI), TTI(TTI) {}
+                 TargetTransformInfo *TTI, MemorySSA *MSSA)
+      : LI(LI), SE(SE), DT(DT), DL(DL), TLI(TLI), TTI(TTI), MSSA(MSSA) {
+    if (MSSA)
+      MSSAU = std::make_unique<MemorySSAUpdater>(MSSA);
+  }
 
   bool run(Loop *L);
 };
@@ -418,11 +425,11 @@ bool IndVarSimplify::handleFloatingPointIV(Loop *L, PHINode *PN) {
   // new comparison.
   NewCompare->takeName(Compare);
   Compare->replaceAllUsesWith(NewCompare);
-  RecursivelyDeleteTriviallyDeadInstructions(Compare, TLI);
+  RecursivelyDeleteTriviallyDeadInstructions(Compare, TLI, MSSAU.get());
 
   // Delete the old floating point increment.
   Incr->replaceAllUsesWith(UndefValue::get(Incr->getType()));
-  RecursivelyDeleteTriviallyDeadInstructions(Incr, TLI);
+  RecursivelyDeleteTriviallyDeadInstructions(Incr, TLI, MSSAU.get());
 
   // If the FP induction variable still has uses, this is because something else
   // in the loop uses its value.  In order to canonicalize the induction
@@ -435,7 +442,7 @@ bool IndVarSimplify::handleFloatingPointIV(Loop *L, PHINode *PN) {
     Value *Conv = new SIToFPInst(NewPHI, PN->getType(), "indvar.conv",
                                  &*PN->getParent()->getFirstInsertionPt());
     PN->replaceAllUsesWith(Conv);
-    RecursivelyDeleteTriviallyDeadInstructions(PN, TLI);
+    RecursivelyDeleteTriviallyDeadInstructions(PN, TLI, MSSAU.get());
   }
   return true;
 }
@@ -2823,12 +2830,14 @@ PreservedAnalyses IndVarSimplifyPass::run(Loop &L, LoopAnalysisManager &AM,
   Function *F = L.getHeader()->getParent();
   const DataLayout &DL = F->getParent()->getDataLayout();
 
-  IndVarSimplify IVS(&AR.LI, &AR.SE, &AR.DT, DL, &AR.TLI, &AR.TTI);
+  IndVarSimplify IVS(&AR.LI, &AR.SE, &AR.DT, DL, &AR.TLI, &AR.TTI, AR.MSSA);
   if (!IVS.run(&L))
     return PreservedAnalyses::all();
 
   auto PA = getLoopPassPreservedAnalyses();
   PA.preserveSet<CFGAnalyses>();
+  if (AR.MSSA)
+    PA.preserve<MemorySSAAnalysis>();
   return PA;
 }
 
@@ -2853,13 +2862,18 @@ struct IndVarSimplifyLegacyPass : public LoopPass {
     auto *TTIP = getAnalysisIfAvailable<TargetTransformInfoWrapperPass>();
     auto *TTI = TTIP ? &TTIP->getTTI(*L->getHeader()->getParent()) : nullptr;
     const DataLayout &DL = L->getHeader()->getModule()->getDataLayout();
+    auto *MSSAAnalysis = getAnalysisIfAvailable<MemorySSAWrapperPass>();
+    MemorySSA *MSSA = nullptr;
+    if (MSSAAnalysis)
+      MSSA = &MSSAAnalysis->getMSSA();
 
-    IndVarSimplify IVS(LI, SE, DT, DL, TLI, TTI);
+    IndVarSimplify IVS(LI, SE, DT, DL, TLI, TTI, MSSA);
     return IVS.run(L);
   }
 
   void getAnalysisUsage(AnalysisUsage &AU) const override {
     AU.setPreservesCFG();
+    AU.addPreserved<MemorySSAWrapperPass>();
     getLoopAnalysisUsage(AU);
   }
 };