// 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>
+#include "llvm/ADT/DenseMap.h"
using namespace llvm;
/// DemoteRegToStack - This function takes a virtual register computed by an
/// 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,
+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.
AllocaInst *Slot;
if (AllocaPoint) {
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.
+
+ // Change all of the users of the instruction to read from the stack slot.
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
+ // 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;
+ // node that we cannot have multiple loads. The problem is that the
+ // resulting 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 of and reuse loads we insert.
+ DenseMap<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,
+ V = new LoadInst(Slot, I.getName()+".reload", VolatileLoads,
PN->getIncomingBlock(i)->getTerminator());
}
PN->setIncomingValue(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.
+ // Insert stores of the computed value into the stack slot. We have to be
+ // careful if I is an invoke instruction, because we can't insert the store
+ // AFTER the terminator instruction.
BasicBlock::iterator InsertPt;
if (!isa<TerminatorInst>(I)) {
InsertPt = &I;
InsertPt = II.getNormalDest()->begin();
}
- for (; isa<PHINode>(InsertPt); ++InsertPt)
- /* empty */; // Don't insert before any PHI nodes.
- new StoreInst(&I, Slot, InsertPt);
+ for (; isa<PHINode>(InsertPt) || isa<LandingPadInst>(InsertPt); ++InsertPt)
+ /* empty */; // Don't insert before 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) {
+/// 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. It returns the pointer to the alloca inserted.
+AllocaInst *llvm::DemotePHIToStack(PHINode *P, Instruction *AllocaPoint) {
if (P->use_empty()) {
- P->eraseFromParent();
- return 0;
+ P->eraseFromParent();
+ return 0;
}
// Create a stack slot to hold the value.
Slot = new AllocaInst(P->getType(), 0, P->getName()+".reg2mem",
F->getEntryBlock().begin());
}
-
- // Iterate over each operand, insert store in each predecessor.
+
+ // Iterate over each operand inserting a 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;
+ assert(II->getParent() != P->getIncomingBlock(i) &&
+ "Invoke edge not supported yet"); (void)II;
}
- new StoreInst(P->getIncomingValue(i), Slot,
+ new StoreInst(P->getIncomingValue(i), Slot,
P->getIncomingBlock(i)->getTerminator());
}
-
- // Insert load in place of the phi and replace all uses.
+
+ // Insert a load in place of the PHI and replace all uses.
Value *V = new LoadInst(Slot, P->getName()+".reload", P);
P->replaceAllUsesWith(V);
-
- // Delete phi.
+
+ // Delete PHI.
P->eraseFromParent();
-
return Slot;
}