Speed up codegen prepare from 3.58s to 0.488s.

[oota-llvm.git] / lib / Transforms / Utils / DemoteRegToStack.cpp

diff --git a/lib/Transforms/Utils/DemoteRegToStack.cpp b/lib/Transforms/Utils/DemoteRegToStack.cpp
index 3eadfa7694af64f46ccc84bfcf1f450a2fbbc3de..c908b4a55914266e041f9ddd00c6d92b05b38a4e 100644 (file)
--- a/lib/Transforms/Utils/DemoteRegToStack.cpp
+++ b/lib/Transforms/Utils/DemoteRegToStack.cpp
@@ -2,8 +2,8 @@
 //
 //                     The LLVM Compiler Infrastructure
 //
-// This file was developed by the LLVM research group and is distributed under
-// the University of Illinois Open Source License. See LICENSE.TXT for details.
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
@@ -29,14 +29,24 @@ using namespace llvm;
 /// invalidating the SSA information for the value.  It returns the pointer to
 /// the alloca inserted to create a stack slot for I.
 ///
-AllocaInst* llvm::DemoteRegToStack(Instruction &I, bool VolatileLoads) {
-  if (I.use_empty()) return 0;                // nothing to do!
-
+AllocaInst* llvm::DemoteRegToStack(Instruction &I, bool VolatileLoads,
+                                   Instruction *AllocaPoint) {
+  if (I.use_empty()) {
+    I.eraseFromParent();
+    return 0;
+  }
+  
   // Create a stack slot to hold the value.
-  Function *F = I.getParent()->getParent();
-  AllocaInst *Slot = new AllocaInst(I.getType(), 0, I.getName(),
-                                    F->getEntryBlock().begin());
-
+  AllocaInst *Slot;
+  if (AllocaPoint) {
+    Slot = new AllocaInst(I.getType(), 0,
+                          I.getName()+".reg2mem", AllocaPoint);
+  } else {
+    Function *F = I.getParent()->getParent();
+    Slot = new AllocaInst(I.getType(), 0, I.getName()+".reg2mem",
+                          F->getEntryBlock().begin());
+  }
+  
   // Change all of the users of the instruction to read from the stack slot
   // instead.
   while (!I.use_empty()) {
@@ -93,3 +103,44 @@ 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, Instruction *AllocaPoint) {
+  if (P->use_empty()) {
+    P->eraseFromParent();    
+    return 0;                
+  }
+
+  // Create a stack slot to hold the value.
+  AllocaInst *Slot;
+  if (AllocaPoint) {
+    Slot = new AllocaInst(P->getType(), 0,
+                          P->getName()+".reg2mem", AllocaPoint);
+  } else {
+    Function *F = P->getParent()->getParent();
+    Slot = new AllocaInst(P->getType(), 0, P->getName()+".reg2mem",
+                          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"); II=II;
+    }
+    new StoreInst(P->getIncomingValue(i), Slot, 
+                  P->getIncomingBlock(i)->getTerminator());
+  }
+  
+  // Insert load in place of the phi and replace all uses.
+  Value *V = new LoadInst(Slot, P->getName()+".reload", P);
+  P->replaceAllUsesWith(V);
+  
+  // Delete phi.
+  P->eraseFromParent();
+  
+  return Slot;
+}