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Reuse induction variables created for strength-reduced GEPs by other similar GEPs.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@20466 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jeff Cohen 2005-03-05 22:40:34 +00:00
parent d81b691ea0
commit b21bf9a8d5
1 changed files with 62 additions and 33 deletions
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95
lib/Transforms/Scalar/LoopStrengthReduce.cpp
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@ -35,6 +35,22 @@ using namespace llvm;
namespace {
Statistic<> NumReduced ("loop-reduce", "Number of GEPs strength reduced");
class GEPCache
{
public:
GEPCache() : CachedPHINode(0), Map() {}
GEPCache* operator[](Value *v) {
std::map<Value *, GEPCache>::iterator I = Map.find(v);
if (I == Map.end())
I = Map.insert(std::pair<Value *, GEPCache>(v, GEPCache())).first;
return &(I->second);
}
PHINode *CachedPHINode;
std::map<Value *, GEPCache> Map;
};
class LoopStrengthReduce : public FunctionPass {
LoopInfo *LI;
DominatorSet *DS;
@ -65,6 +81,7 @@ namespace {
private:
void runOnLoop(Loop *L);
void strengthReduceGEP(GetElementPtrInst *GEPI, Loop *L,
GEPCache* GEPCache,
Instruction *InsertBefore,
std::set<Instruction*> &DeadInsts);
void DeleteTriviallyDeadInstructions(std::set<Instruction*> &Insts);
@ -96,6 +113,7 @@ DeleteTriviallyDeadInstructions(std::set<Instruction*> &Insts) {
}
void LoopStrengthReduce::strengthReduceGEP(GetElementPtrInst *GEPI, Loop *L,
GEPCache *Cache,
Instruction *InsertBefore,
std::set<Instruction*> &DeadInsts) {
// We will strength reduce the GEP by splitting it into two parts. The first
@ -117,6 +135,7 @@ void LoopStrengthReduce::strengthReduceGEP(GetElementPtrInst *GEPI, Loop *L,
BasicBlock *Header = L->getHeader();
BasicBlock *Preheader = L->getLoopPreheader();
bool AllConstantOperands = true;
Cache = (*Cache)[GEPI->getOperand(0)];
for (unsigned op = 1, e = GEPI->getNumOperands(); op != e; ++op) {
Value *operand = GEPI->getOperand(op);
@ -145,6 +164,7 @@ void LoopStrengthReduce::strengthReduceGEP(GetElementPtrInst *GEPI, Loop *L,
AllConstantOperands = false;
} else
return;
Cache = (*Cache)[operand];
}
assert(indvar > 0 && "Indvar used by GEP not found in operand list");
@ -157,7 +177,7 @@ void LoopStrengthReduce::strengthReduceGEP(GetElementPtrInst *GEPI, Loop *L,
if (!DS->dominates(GepPtrOp, Preheader->getTerminator()))
return;
// Don't reduced multiplies that the target can handle via addressing modes.
// Don't reduce multiplies that the target can handle via addressing modes.
uint64_t sz = getAnalysis<TargetData>().getTypeSize(ty);
for (unsigned i = 1; i <= MaxTargetAMSize; i *= 2)
if (i == sz)
@ -169,38 +189,46 @@ void LoopStrengthReduce::strengthReduceGEP(GetElementPtrInst *GEPI, Loop *L,
// If there is only one operand after the initial non-constant one, we know
// that it was the induction variable, and has been replaced by a constant
// null value. In this case, replace the GEP with a use of pointer directly.
Value *PreGEP;
if (AllConstantOperands && isa<Constant>(GEPI->getOperand(0))) {
Constant *C = dyn_cast<Constant>(GEPI->getOperand(0));
PreGEP = ConstantExpr::getGetElementPtr(C, pre_op_vector);
} else if (pre_op_vector.size() == 1) {
PreGEP = GEPI->getOperand(0);
} else {
PreGEP = new GetElementPtrInst(GEPI->getOperand(0),
pre_op_vector, GEPI->getName()+".pre",
Preheader->getTerminator());
}
PHINode *NewPHI;
if (1) {
Value *PreGEP;
if (AllConstantOperands && isa<Constant>(GEPI->getOperand(0))) {
Constant *C = dyn_cast<Constant>(GEPI->getOperand(0));
PreGEP = ConstantExpr::getGetElementPtr(C, pre_op_vector);
} else if (pre_op_vector.size() == 1) {
PreGEP = GEPI->getOperand(0);
} else {
PreGEP = new GetElementPtrInst(GEPI->getOperand(0),
pre_op_vector, GEPI->getName()+".pre",
Preheader->getTerminator());
}
// The next step of the strength reduction is to create a PHI that will choose
// between the initial GEP we created and inserted into the preheader, and
// the incremented GEP that we will create below and insert into the loop body
PHINode *NewPHI = new PHINode(PreGEP->getType(),
GEPI->getName()+".str", InsertBefore);
NewPHI->addIncoming(PreGEP, Preheader);
// Now, create the GEP instruction to increment by one the value selected by
// the PHI instruction we just created above, and add it as the second
// incoming Value/BasicBlock pair to the PHINode. It is inserted before the
// increment of the canonical induction variable.
Instruction *IncrInst =
const_cast<Instruction*>(L->getCanonicalInductionVariableIncrement());
GetElementPtrInst *StrGEP = new GetElementPtrInst(NewPHI, inc_op_vector,
GEPI->getName()+".inc",
IncrInst);
pred_iterator PI = pred_begin(Header);
if (*PI == Preheader)
++PI;
NewPHI->addIncoming(StrGEP, *PI);
// The next step of the strength reduction is to create a PHI that will choose
// between the initial GEP we created and inserted into the preheader, and
// the incremented GEP that we will create below and insert into the loop body
NewPHI = new PHINode(PreGEP->getType(),
GEPI->getName()+".str", InsertBefore);
NewPHI->addIncoming(PreGEP, Preheader);
// Now, create the GEP instruction to increment by one the value selected by
// the PHI instruction we just created above, and add it as the second
// incoming Value/BasicBlock pair to the PHINode. It is inserted before the
// increment of the canonical induction variable.
Instruction *IncrInst =
const_cast<Instruction*>(L->getCanonicalInductionVariableIncrement());
GetElementPtrInst *StrGEP = new GetElementPtrInst(NewPHI, inc_op_vector,
GEPI->getName()+".inc",
IncrInst);
pred_iterator PI = pred_begin(Header);
if (*PI == Preheader)
++PI;
NewPHI->addIncoming(StrGEP, *PI);
Cache->CachedPHINode = NewPHI;
} else {
// Reuse previously created pointer, as it is identical to the one we were
// about to create.
NewPHI = Cache->CachedPHINode;
}
if (GEPI->getNumOperands() - 1 == indvar) {
// If there were no operands following the induction variable, replace all
@ -246,10 +274,11 @@ void LoopStrengthReduce::runOnLoop(Loop *L) {
// strength reduced pointers we'll be creating after the canonical induction
// variable's PHI.
std::set<Instruction*> DeadInsts;
GEPCache Cache;
for (Value::use_iterator UI = PN->use_begin(), UE = PN->use_end();
UI != UE; ++UI)
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI))
strengthReduceGEP(GEPI, L, PN->getNext(), DeadInsts);
strengthReduceGEP(GEPI, L, &Cache, PN->getNext(), DeadInsts);
// Clean up after ourselves
if (!DeadInsts.empty()) {