//
// 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.
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/Analysis/CFG.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Type.h"
#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
/// 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!
+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.
+ // 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;
} 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();
+ if (II.getNormalDest()->getSinglePredecessor())
+ InsertPt = II.getNormalDest()->getFirstInsertionPt();
+ else {
+ // We cannot demote invoke instructions to the stack if their normal edge
+ // is critical. Therefore, split the critical edge and insert the store
+ // in the newly created basic block.
+ unsigned SuccNum = GetSuccessorNumber(I.getParent(), II.getNormalDest());
+ TerminatorInst *TI = &cast<TerminatorInst>(I);
+ assert (isCriticalEdge(TI, SuccNum) &&
+ "Expected a critical edge!");
+ BasicBlock *BB = SplitCriticalEdge(TI, SuccNum);
+ assert (BB && "Unable to split critical edge.");
+ InsertPt = BB->getFirstInsertionPt();
+ }
}
- 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 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. 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 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"); (void)II;
+ }
+ new StoreInst(P->getIncomingValue(i), Slot,
+ P->getIncomingBlock(i)->getTerminator());
+ }
+
+ // Insert a load in place of the PHI and replace all uses.
+ BasicBlock::iterator InsertPt = P;
+
+ for (; isa<PHINode>(InsertPt) || isa<LandingPadInst>(InsertPt); ++InsertPt)
+ /* empty */; // Don't insert before PHI nodes or landingpad instrs.
+
+ Value *V = new LoadInst(Slot, P->getName()+".reload", InsertPt);
+ P->replaceAllUsesWith(V);
+ // Delete PHI.
+ P->eraseFromParent();
return Slot;
}
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