///
AllocaInst *DemoteRegToStack(Instruction &X, bool VolatileLoads = false);
+/// 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 *DemotePHIToStack(PHINode *P);
+
} // End llvm namespace
#endif
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<InvokeInst>(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<PHINode>(InsertPt); ++InsertPt);
+ Value *V = new LoadInst(Slot, P->getName()+".reload", P);
+ P->replaceAllUsesWith(V);
+
+ // Delete phi.
+ P->eraseFromParent();
+
+ return Slot;
+}