X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FTransforms%2FScalar%2FNaryReassociate.cpp;h=930552d2f9043855e2625f8a482d31953d553644;hb=8293dfd63f4a38dbf81da882c4ec699ebb098f95;hp=c6cb12f77fa0a3476aee35a03f53c7ed4335e167;hpb=2509f522f6b6c1f687504807d0a1bd508f4df457;p=oota-llvm.git

diff --git a/lib/Transforms/Scalar/NaryReassociate.cpp b/lib/Transforms/Scalar/NaryReassociate.cpp
index c6cb12f77fa..930552d2f90 100644
--- a/lib/Transforms/Scalar/NaryReassociate.cpp
+++ b/lib/Transforms/Scalar/NaryReassociate.cpp
@@ -188,7 +188,7 @@ private:
   //     foo(a + b);
   //   if (p2)
   //     bar(a + b);
-  DenseMap<const SCEV *, SmallVector<Instruction *, 2>> SeenExprs;
+  DenseMap<const SCEV *, SmallVector<WeakVH, 2>> SeenExprs;
 };
 } // anonymous namespace
 
@@ -246,19 +246,21 @@ bool NaryReassociate::doOneIteration(Function &F) {
        Node != GraphTraits<DominatorTree *>::nodes_end(DT); ++Node) {
     BasicBlock *BB = Node->getBlock();
     for (auto I = BB->begin(); I != BB->end(); ++I) {
-      if (SE->isSCEVable(I->getType()) && isPotentiallyNaryReassociable(I)) {
-        const SCEV *OldSCEV = SE->getSCEV(I);
-        if (Instruction *NewI = tryReassociate(I)) {
+      if (SE->isSCEVable(I->getType()) && isPotentiallyNaryReassociable(&*I)) {
+        const SCEV *OldSCEV = SE->getSCEV(&*I);
+        if (Instruction *NewI = tryReassociate(&*I)) {
           Changed = true;
-          SE->forgetValue(I);
+          SE->forgetValue(&*I);
           I->replaceAllUsesWith(NewI);
-          RecursivelyDeleteTriviallyDeadInstructions(I, TLI);
-          I = NewI;
+          // If SeenExprs constains I's WeakVH, that entry will be replaced with
+          // nullptr.
+          RecursivelyDeleteTriviallyDeadInstructions(&*I, TLI);
+          I = NewI->getIterator();
         }
         // Add the rewritten instruction to SeenExprs; the original instruction
         // is deleted.
-        const SCEV *NewSCEV = SE->getSCEV(I);
-        SeenExprs[NewSCEV].push_back(I);
+        const SCEV *NewSCEV = SE->getSCEV(&*I);
+        SeenExprs[NewSCEV].push_back(WeakVH(&*I));
         // Ideally, NewSCEV should equal OldSCEV because tryReassociate(I)
         // is equivalent to I. However, ScalarEvolution::getSCEV may
         // weaken nsw causing NewSCEV not to equal OldSCEV. For example, suppose
@@ -278,7 +280,7 @@ bool NaryReassociate::doOneIteration(Function &F) {
         //
         // This improvement is exercised in @reassociate_gep_nsw in nary-gep.ll.
         if (NewSCEV != OldSCEV)
-          SeenExprs[OldSCEV].push_back(I);
+          SeenExprs[OldSCEV].push_back(WeakVH(&*I));
       }
     }
   }
@@ -562,9 +564,13 @@ NaryReassociate::findClosestMatchingDominator(const SCEV *CandidateExpr,
   // future instruction either. Therefore, we pop it out of the stack. This
   // optimization makes the algorithm O(n).
   while (!Candidates.empty()) {
-    Instruction *Candidate = Candidates.back();
-    if (DT->dominates(Candidate, Dominatee))
-      return Candidate;
+    // Candidates stores WeakVHs, so a candidate can be nullptr if it's removed
+    // during rewriting.
+    if (Value *Candidate = Candidates.back()) {
+      Instruction *CandidateInstruction = cast<Instruction>(Candidate);
+      if (DT->dominates(CandidateInstruction, Dominatee))
+        return CandidateInstruction;
+    }
     Candidates.pop_back();
   }
   return nullptr;