It's not necessary to do rounding for alloca operations when the requested
alignment is equal to the stack alignment.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40004 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Utils/DemoteRegToStack.cpp b/lib/Transforms/Utils/DemoteRegToStack.cpp
new file mode 100644
index 0000000..df332b2
--- /dev/null
+++ b/lib/Transforms/Utils/DemoteRegToStack.cpp
@@ -0,0 +1,133 @@
+//===- DemoteRegToStack.cpp - Move a virtual register to the stack --------===//
+//
+// 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 provide the function DemoteRegToStack(). This function takes a
+// virtual register computed by an Instruction and replaces it with a slot in
+// the stack frame, allocated via alloca. It returns the pointer to the
+// AllocaInst inserted. After this function is called on an instruction, we are
+// guaranteed that the only user of the instruction is a store that is
+// immediately after it.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Function.h"
+#include "llvm/Instructions.h"
+#include "llvm/Type.h"
+#include <map>
+using namespace llvm;
+
+/// DemoteRegToStack - This function takes a virtual register computed by an
+/// Instruction and replaces it with a slot in the stack frame, allocated via
+/// alloca. This allows the CFG to be changed around without fear of
+/// 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!
+
+ // 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());
+
+ // Change all of the users of the instruction to read from the stack slot
+ // instead.
+ while (!I.use_empty()) {
+ Instruction *U = cast<Instruction>(I.use_back());
+ if (PHINode *PN = dyn_cast<PHINode>(U)) {
+ // If this is a PHI node, we can't insert a load of the value before the
+ // use. Instead, insert the load in the predecessor block corresponding
+ // to the incoming value.
+ //
+ // Note that if there are multiple edges from a basic block to this PHI
+ // node that we cannot multiple loads. The problem is that the resultant
+ // PHI node will have multiple values (from each load) coming in from the
+ // same block, which is illegal SSA form. For this reason, we keep track
+ // and reuse loads we insert.
+ std::map<BasicBlock*, Value*> Loads;
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
+ if (PN->getIncomingValue(i) == &I) {
+ Value *&V = Loads[PN->getIncomingBlock(i)];
+ if (V == 0) {
+ // Insert the load into the predecessor block
+ V = new LoadInst(Slot, I.getName()+".reload", VolatileLoads,
+ PN->getIncomingBlock(i)->getTerminator());
+ }
+ PN->setIncomingValue(i, V);
+ }
+
+ } else {
+ // If this is a normal instruction, just insert a load.
+ Value *V = new LoadInst(Slot, I.getName()+".reload", VolatileLoads, U);
+ U->replaceUsesOfWith(&I, V);
+ }
+ }
+
+
+ // Insert stores of the computed value into the stack slot. We have to be
+ // careful is I is an invoke instruction though, because we can't insert the
+ // store AFTER the terminator instruction.
+ 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.
+ InvokeInst &II = cast<InvokeInst>(I);
+ assert(II.getNormalDest()->getSinglePredecessor() &&
+ "Cannot demote invoke with a critical successor!");
+ InsertPt = II.getNormalDest()->begin();
+ }
+
+ for (; isa<PHINode>(InsertPt); ++InsertPt)
+ /* empty */; // Don't insert before any PHI nodes.
+ 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) {
+ 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;
+}