Revert r146822 at Pete Cooper's request as it broke clang self hosting.

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

diff --git a/lib/Transforms/Utils/DemoteRegToStack.cpp b/lib/Transforms/Utils/DemoteRegToStack.cpp
index bbf998d790c4136266d6d58a61fa63ef3bce8b4a..3ef6b018bf89837bb56be300ab9d63eb6c5b03b3 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.
 //
 //===----------------------------------------------------------------------===//
 //
@@ -29,13 +29,23 @@ 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.
@@ -57,7 +67,7 @@ AllocaInst* llvm::DemoteRegToStack(Instruction &I, bool VolatileLoads) {
           Value *&V = Loads[PN->getIncomingBlock(i)];
           if (V == 0) {
             // Insert the load into the predecessor block
-            V = new LoadInst(Slot, I.getName()+".reload", VolatileLoads, 
+            V = new LoadInst(Slot, I.getName()+".reload", VolatileLoads,
                              PN->getIncomingBlock(i)->getTerminator());
           }
           PN->setIncomingValue(i, V);
@@ -77,6 +87,7 @@ AllocaInst* llvm::DemoteRegToStack(Instruction &I, bool VolatileLoads) {
   BasicBlock::iterator InsertPt;
   if (!isa<TerminatorInst>(I)) {
     InsertPt = &I;
+    ++InsertPt;
   } else {
     // We cannot demote invoke instructions to the stack if their normal edge
     // is critical.
@@ -86,9 +97,50 @@ AllocaInst* llvm::DemoteRegToStack(Instruction &I, bool VolatileLoads) {
     InsertPt = II.getNormalDest()->begin();
   }
 
-  for (++InsertPt; isa<PHINode>(InsertPt); ++InsertPt)
-  /* empty */;   // Don't insert before any PHI nodes.
+  for (; isa<PHINode>(InsertPt) || isa<LandingPadInst>(InsertPt); ++InsertPt)
+  /* empty */;   // Don't insert before any PHI nodes or landingpad instrs.
   new StoreInst(&I, Slot, InsertPt);
 
   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"); (void)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;
+}