From 08d14d2469c4f0465f610a204353220ee2ccde9c Mon Sep 17 00:00:00 2001 From: Tanya Lattner Date: Wed, 11 Jul 2007 18:41:34 +0000 Subject: Adding ability to demote phi to stack. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@39744 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/Utils/DemoteRegToStack.cpp | 38 +++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) (limited to 'lib/Transforms/Utils/DemoteRegToStack.cpp') diff --git a/lib/Transforms/Utils/DemoteRegToStack.cpp b/lib/Transforms/Utils/DemoteRegToStack.cpp index 3eadfa7694..df332b289d 100644 --- a/lib/Transforms/Utils/DemoteRegToStack.cpp +++ b/lib/Transforms/Utils/DemoteRegToStack.cpp @@ -93,3 +93,41 @@ AllocaInst* llvm::DemoteRegToStack(Instruction &I, bool VolatileLoads) { return Slot; } + + +/// DemotePHIToStack - This function takes a virtual register computed by a phi +/// node and replaces it with a slot in the stack frame, allocated via alloca. +/// The phi node is deleted and it returns the pointer to the alloca inserted. +AllocaInst* llvm::DemotePHIToStack(PHINode *P) { + if (P->use_empty()) { + P->eraseFromParent(); + return 0; + } + + // Create a stack slot to hold the value. + Function *F = P->getParent()->getParent(); + AllocaInst *Slot = new AllocaInst(P->getType(), 0, P->getName(), + F->getEntryBlock().begin()); + + // Iterate over each operand, insert store in each predecessor. + for (unsigned i = 0, e = P->getNumIncomingValues(); i < e; ++i) { + if (InvokeInst *II = dyn_cast(P->getIncomingValue(i))) { + assert(II->getParent() != P->getIncomingBlock(i) && + "Invoke edge not supported yet"); + } + new StoreInst(P->getIncomingValue(i), Slot, + P->getIncomingBlock(i)->getTerminator()); + } + + // Insert load in place of the phi and replace all uses. + BasicBlock::iterator InsertPt; + for (InsertPt = P->getParent()->getInstList().begin(); + isa(InsertPt); ++InsertPt); + Value *V = new LoadInst(Slot, P->getName()+".reload", P); + P->replaceAllUsesWith(V); + + // Delete phi. + P->eraseFromParent(); + + return Slot; +} -- cgit v1.2.3