mirror of
https://github.com/RPCSX/llvm.git
synced 2024-12-05 10:27:02 +00:00
ab2b328c78
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@6397 91177308-0d34-0410-b5e6-96231b3b80d8
192 lines
7.0 KiB
C++
192 lines
7.0 KiB
C++
//===- DemoteRegToStack.cpp - Move a virtual reg. to stack ------*- C++ -*-===//
|
|
//
|
|
// This file provide the function DemoteRegToStack(). This function takes a
|
|
// virtual register computed by an Instruction& X and replaces it with a slot in
|
|
// the stack frame, allocated via alloca. It returns the pointer to the
|
|
// AllocaInst inserted.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "llvm/Transforms/Utils/DemoteRegToStack.h"
|
|
#include "llvm/Function.h"
|
|
#include "llvm/iMemory.h"
|
|
#include "llvm/iPHINode.h"
|
|
#include "llvm/iTerminators.h"
|
|
#include "llvm/Type.h"
|
|
#include "Support/hash_set"
|
|
#include <stack>
|
|
|
|
//----------------------------------------------------------------------------
|
|
// function DemoteRegToStack()
|
|
//
|
|
//----------------------------------------------------------------------------
|
|
|
|
typedef hash_set<PHINode*> PhiSet;
|
|
typedef hash_set<PHINode*>::iterator PhiSetIterator;
|
|
|
|
// Helper function to push a phi *and* all its operands to the worklist!
|
|
// Do not push an instruction if it is already in the result set of Phis to go.
|
|
inline void PushOperandsOnWorkList(std::stack<Instruction*>& workList,
|
|
PhiSet& phisToGo, PHINode* phiN) {
|
|
for (User::op_iterator OI = phiN->op_begin(), OE = phiN->op_end();
|
|
OI != OE; ++OI)
|
|
if (Instruction* opI = dyn_cast<Instruction>(OI))
|
|
if (!isa<PHINode>(opI) ||
|
|
phisToGo.find(cast<PHINode>(opI)) == phisToGo.end())
|
|
workList.push(opI);
|
|
}
|
|
|
|
void FindPhis(Instruction& X, PhiSet& phisToGo)
|
|
{
|
|
std::stack<Instruction*> workList;
|
|
workList.push(&X);
|
|
|
|
// Handle the case that X itself is a Phi!
|
|
if (PHINode* phiX = dyn_cast<PHINode>(&X))
|
|
{
|
|
phisToGo.insert(phiX);
|
|
PushOperandsOnWorkList(workList, phisToGo, phiX);
|
|
}
|
|
|
|
// Now use a worklist to find all phis reachable from X, and
|
|
// (recursively) all phis reachable from operands of such phis.
|
|
for (Instruction* workI; !workList.empty(); workList.pop())
|
|
{
|
|
workI = workList.top();
|
|
for (Value::use_iterator UI=workI->use_begin(), UE=workI->use_end();
|
|
UI != UE; ++UI)
|
|
if (PHINode* phiN = dyn_cast<PHINode>(*UI))
|
|
if (phisToGo.find(phiN) == phisToGo.end())
|
|
{ // Seeing this phi for the first time: it must go!
|
|
phisToGo.insert(phiN);
|
|
workList.push(phiN);
|
|
PushOperandsOnWorkList(workList, phisToGo, phiN);
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
// Create the Alloca for X
|
|
AllocaInst* CreateAllocaForX(Instruction& X)
|
|
{
|
|
Function* parentFunc = X.getParent()->getParent();
|
|
Instruction* entryInst = parentFunc->getEntryNode().begin();
|
|
return new AllocaInst(X.getType(), /*arraySize*/ NULL,
|
|
X.hasName()? X.getName()+std::string("OnStack")
|
|
: "DemotedTmp",
|
|
entryInst);
|
|
}
|
|
|
|
// Insert loads before all uses of I, except uses in Phis
|
|
// since all such Phis *must* be deleted.
|
|
void LoadBeforeUses(Instruction* def, AllocaInst* XSlot)
|
|
{
|
|
for (unsigned nPhis = 0; def->use_size() - nPhis > 0; )
|
|
{
|
|
Instruction* useI = cast<Instruction>(def->use_back());
|
|
if (!isa<PHINode>(useI))
|
|
{
|
|
LoadInst* loadI =
|
|
new LoadInst(XSlot, std::string("Load")+XSlot->getName(), useI);
|
|
useI->replaceUsesOfWith(def, loadI);
|
|
}
|
|
else
|
|
++nPhis;
|
|
}
|
|
}
|
|
|
|
void AddLoadsAndStores(AllocaInst* XSlot, Instruction& X, PhiSet& phisToGo)
|
|
{
|
|
for (PhiSetIterator PI=phisToGo.begin(), PE=phisToGo.end(); PI != PE; ++PI)
|
|
{
|
|
PHINode* pn = *PI;
|
|
|
|
// First, insert loads before all uses except uses in Phis.
|
|
// Do this first because new stores will appear as uses also!
|
|
LoadBeforeUses(pn, XSlot);
|
|
|
|
// For every incoming operand of the Phi, insert a store either
|
|
// just after the instruction defining the value or just before the
|
|
// predecessor of the Phi if the value is a formal, not an instruction.
|
|
//
|
|
for (unsigned i=0, N=pn->getNumIncomingValues(); i < N; ++i)
|
|
{
|
|
Value* phiOp = pn->getIncomingValue(i);
|
|
if (phiOp != &X &&
|
|
(!isa<PHINode>(phiOp) ||
|
|
phisToGo.find(cast<PHINode>(phiOp)) == phisToGo.end()))
|
|
{ // This operand is not a phi that will be deleted: need to store.
|
|
assert(!isa<TerminatorInst>(phiOp));
|
|
|
|
Instruction* storeBefore;
|
|
if (Instruction* I = dyn_cast<Instruction>(phiOp))
|
|
{ // phiOp is an instruction, store its result right after it.
|
|
assert(I->getNext() && "Non-terminator without successor?");
|
|
storeBefore = I->getNext();
|
|
}
|
|
else
|
|
{ // If not, it must be a formal: store it at the end of the
|
|
// predecessor block of the Phi (*not* at function entry!).
|
|
storeBefore = pn->getIncomingBlock(i)->getTerminator();
|
|
}
|
|
|
|
// Create instr. to store the value of phiOp before `insertBefore'
|
|
StoreInst* storeI = new StoreInst(phiOp, XSlot, storeBefore);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
void DeletePhis(PhiSet& phisToGo)
|
|
{
|
|
for (PhiSetIterator PI=phisToGo.begin(), PE=phisToGo.end(); PI != PE; ++PI)
|
|
{
|
|
assert((*PI)->use_size() == 0 && "This PHI should be DEAD!");
|
|
(*PI)->getParent()->getInstList().remove(*PI);
|
|
delete *PI;
|
|
}
|
|
phisToGo.clear();
|
|
}
|
|
|
|
//----------------------------------------------------------------------------
|
|
// function DemoteRegToStack()
|
|
//
|
|
// This function takes a virtual register computed by an
|
|
// Instruction& X and replaces it with a slot in the stack frame,
|
|
// allocated via alloca. It has to:
|
|
// (1) Identify all Phi operations that have X as an operand and
|
|
// transitively other Phis that use such Phis;
|
|
// (2) Store all values merged with X via Phi operations to the stack slot;
|
|
// (3) Load the value from the stack slot just before any use of X or any
|
|
// of the Phis that were eliminated; and
|
|
// (4) Delete all the Phis, which should all now be dead.
|
|
//
|
|
// Returns the pointer to the alloca inserted to create a stack slot for X.
|
|
//----------------------------------------------------------------------------
|
|
|
|
AllocaInst* DemoteRegToStack(Instruction& X)
|
|
{
|
|
if (X.getType() == Type::VoidTy)
|
|
return NULL; // nothing to do!
|
|
|
|
// Find all Phis involving X or recursively using such Phis or Phis
|
|
// involving operands of such Phis (essentially all Phis in the "web" of X)
|
|
PhiSet phisToGo;
|
|
FindPhis(X, phisToGo);
|
|
|
|
// Create a stack slot to hold X
|
|
AllocaInst* XSlot = CreateAllocaForX(X);
|
|
|
|
// Insert loads before all uses of X and (*only then*) insert store after X
|
|
assert(X.getNext() && "Non-terminator (since non-void) with no successor?");
|
|
LoadBeforeUses(&X, XSlot);
|
|
StoreInst* storeI = new StoreInst(&X, XSlot, X.getNext());
|
|
|
|
// Do the same for all the phis that will be deleted
|
|
AddLoadsAndStores(XSlot, X, phisToGo);
|
|
|
|
// Delete the phis and return the alloca instruction
|
|
DeletePhis(phisToGo);
|
|
return XSlot;
|
|
}
|