Commit eb9b0330 authored by Tanya Lattner's avatar Tanya Lattner
Browse files

Merge from mainline because Owen said so. 

llvm-svn: 42080
parent 9641951f

llvm/lib/Transforms/Scalar/GVN.cpp

+16 −1
Original line number Diff line number Diff line
@@ -673,6 +673,7 @@ namespace { 
    void dump(DenseMap<BasicBlock*, Value*>& d);

    bool iterateOnFunction(Function &F);

    Value* CollapsePhi(PHINode* p);

    bool isSafeReplacement(PHINode* p, Instruction* inst);

  };

  

  char GVN::ID = 0;
@@ -731,6 +732,7 @@ Value* GVN::CollapsePhi(PHINode* p) { 
  if (constVal) {

    if (Instruction* inst = dyn_cast<Instruction>(constVal)) {

      if (DT.dominates(inst, p))

        if (isSafeReplacement(p, inst))

          return inst;

    } else {

      return constVal;
@@ -740,6 +742,19 @@ Value* GVN::CollapsePhi(PHINode* p) { 
  return 0;

}



bool GVN::isSafeReplacement(PHINode* p, Instruction* inst) {

  if (!isa<PHINode>(inst))

    return true;

  

  for (Instruction::use_iterator UI = p->use_begin(), E = p->use_end();

       UI != E; ++UI)

    if (PHINode* use_phi = dyn_cast<PHINode>(UI))

      if (use_phi->getParent() == inst->getParent())

        return false;

  

  return true;

}



/// GetValueForBlock - Get the value to use within the specified basic block.

/// available values are in Phis.

Value *GVN::GetValueForBlock(BasicBlock *BB, LoadInst* orig,