//
// The LLVM Compiler Infrastructure
//
-// This file was developed by Devang Patel and is distributed under
-// the University of Illinois Open Source License. See LICENSE.TXT for details.
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
};
private:
+
+ // safeIcmpInst - CI is considered safe instruction if one of the operand
+ // is SCEVAddRecExpr based on induction variable and other operand is
+ // loop invariant. If CI is safe then populate SplitInfo object SD appropriately
+ // and return true;
+ bool safeICmpInst(ICmpInst *CI, SplitInfo &SD);
+
/// Find condition inside a loop that is suitable candidate for index split.
void findSplitCondition();
/// instruction then loop body is executed only for one iteration. In
/// such case eliminate loop structure surrounding this loop body. For
bool processOneIterationLoop(SplitInfo &SD);
-
+
+ void updateLoopBounds(ICmpInst *CI);
+ /// updateLoopIterationSpace - Current loop body is covered by an AND
+ /// instruction whose operands compares induction variables with loop
+ /// invariants. If possible, hoist this check outside the loop by
+ /// updating appropriate start and end values for induction variable.
+ bool updateLoopIterationSpace(SplitInfo &SD);
+
/// If loop header includes loop variant instruction operands then
/// this loop may not be eliminated.
bool safeHeader(SplitInfo &SD, BasicBlock *BB);
/// Update ExitBB PHINodes' to reflect this change.
void updatePHINodes(BasicBlock *ExitBB, BasicBlock *Latch,
BasicBlock *Header,
- PHINode *IV, Instruction *IVIncrement);
+ PHINode *IV, Instruction *IVIncrement, Loop *LP);
/// moveExitCondition - Move exit condition EC into split condition block CondBB.
void moveExitCondition(BasicBlock *CondBB, BasicBlock *ActiveBB,
// Induction variable's final loop exit value operand number in exit condition..
unsigned ExitValueNum;
};
-
- char LoopIndexSplit::ID = 0;
- RegisterPass<LoopIndexSplit> X ("loop-index-split", "Index Split Loops");
}
+char LoopIndexSplit::ID = 0;
+static RegisterPass<LoopIndexSplit>
+X("loop-index-split", "Index Split Loops");
+
LoopPass *llvm::createLoopIndexSplitPass() {
return new LoopIndexSplit();
}
return false;
// First see if it is possible to eliminate loop itself or not.
- for (SmallVector<SplitInfo, 4>::iterator SI = SplitData.begin(),
- E = SplitData.end(); SI != E;) {
+ for (SmallVector<SplitInfo, 4>::iterator SI = SplitData.begin();
+ SI != SplitData.end();) {
SplitInfo &SD = *SI;
ICmpInst *CI = dyn_cast<ICmpInst>(SD.SplitCondition);
- if (CI && CI->getPredicate() == ICmpInst::ICMP_EQ) {
+ if (SD.SplitCondition->getOpcode() == Instruction::And) {
+ Changed = updateLoopIterationSpace(SD);
+ if (Changed) {
+ ++NumIndexSplit;
+ // If is loop is eliminated then nothing else to do here.
+ return Changed;
+ } else {
+ SmallVector<SplitInfo, 4>::iterator Delete_SI = SI;
+ SI = SplitData.erase(Delete_SI);
+ }
+ }
+ else if (CI && CI->getPredicate() == ICmpInst::ICMP_EQ) {
Changed = processOneIterationLoop(SD);
if (Changed) {
++NumIndexSplit;
return Changed;
} else {
SmallVector<SplitInfo, 4>::iterator Delete_SI = SI;
- ++SI;
- SplitData.erase(Delete_SI);
+ SI = SplitData.erase(Delete_SI);
}
} else
++SI;
Value *Op0 = I->getOperand(0);
Value *Op1 = I->getOperand(1);
- if (PHINode *PN = dyn_cast<PHINode>(Op0)) {
- if (PN->getParent() == L->getHeader()
- && isa<ConstantInt>(Op1)) {
- IndVar = PN;
- IndVarIncrement = I;
- return;
- }
- }
-
- if (PHINode *PN = dyn_cast<PHINode>(Op1)) {
- if (PN->getParent() == L->getHeader()
- && isa<ConstantInt>(Op0)) {
- IndVar = PN;
- IndVarIncrement = I;
- return;
- }
- }
+ if (PHINode *PN = dyn_cast<PHINode>(Op0))
+ if (PN->getParent() == L->getHeader())
+ if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1))
+ if (CI->isOne()) {
+ IndVar = PN;
+ IndVarIncrement = I;
+ return;
+ }
+
+ if (PHINode *PN = dyn_cast<PHINode>(Op1))
+ if (PN->getParent() == L->getHeader())
+ if (ConstantInt *CI = dyn_cast<ConstantInt>(Op0))
+ if (CI->isOne()) {
+ IndVar = PN;
+ IndVarIncrement = I;
+ return;
+ }
return;
}
if (!CI)
return;
- // FIXME
+ // FIXME
if (CI->getPredicate() == ICmpInst::ICMP_EQ
|| CI->getPredicate() == ICmpInst::ICMP_NE)
return;
- if (CI->getPredicate() == ICmpInst::ICMP_SGT
- || CI->getPredicate() == ICmpInst::ICMP_UGT
- || CI->getPredicate() == ICmpInst::ICMP_SGE
- || CI->getPredicate() == ICmpInst::ICMP_UGE) {
-
- BasicBlock *FirstSuccessor = BR->getSuccessor(0);
- // splitLoop() is expecting LT/LE as exit condition predicate.
- // Swap operands here if possible to meet this requirement.
- if (!L->contains(FirstSuccessor))
- CI->swapOperands();
- else
- return;
- }
-
ExitCondition = CI;
// Exit condition's one operand is loop invariant exit value and second
BasicBlock *Preheader = L->getLoopPreheader();
StartValue = IndVar->getIncomingValueForBlock(Preheader);
}
+
+ // If start value is more then exit value where induction variable
+ // increments by 1 then we are potentially dealing with an infinite loop.
+ // Do not index split this loop.
+ if (ExitCondition) {
+ ConstantInt *SV = dyn_cast<ConstantInt>(StartValue);
+ ConstantInt *EV =
+ dyn_cast<ConstantInt>(ExitCondition->getOperand(ExitValueNum));
+ if (SV && EV && SV->getSExtValue() > EV->getSExtValue())
+ ExitCondition = NULL;
+ else if (EV && EV->isZero())
+ ExitCondition = NULL;
+ }
}
/// Find condition inside a loop that is suitable candidate for index split.
if (BR->isUnconditional())
continue;
+ if (Instruction *AndI = dyn_cast<Instruction>(BR->getCondition())) {
+ if (AndI->getOpcode() == Instruction::And) {
+ ICmpInst *Op0 = dyn_cast<ICmpInst>(AndI->getOperand(0));
+ ICmpInst *Op1 = dyn_cast<ICmpInst>(AndI->getOperand(1));
+
+ if (!Op0 || !Op1)
+ continue;
+
+ if (!safeICmpInst(Op0, SD))
+ continue;
+ SD.clear();
+ if (!safeICmpInst(Op1, SD))
+ continue;
+ SD.clear();
+ SD.SplitCondition = AndI;
+ SplitData.push_back(SD);
+ continue;
+ }
+ }
ICmpInst *CI = dyn_cast<ICmpInst>(BR->getCondition());
if (!CI || CI == ExitCondition)
continue;
// If split condition predicate is GT or GE then first execute
// false branch of split condition.
- if (CI->getPredicate() != ICmpInst::ICMP_ULT
- && CI->getPredicate() != ICmpInst::ICMP_SLT
- && CI->getPredicate() != ICmpInst::ICMP_ULE
- && CI->getPredicate() != ICmpInst::ICMP_SLE)
+ if (CI->getPredicate() == ICmpInst::ICMP_UGT
+ || CI->getPredicate() == ICmpInst::ICMP_SGT
+ || CI->getPredicate() == ICmpInst::ICMP_UGE
+ || CI->getPredicate() == ICmpInst::ICMP_SGE)
SD.UseTrueBranchFirst = false;
// If one operand is loop invariant and second operand is SCEVAddRecExpr
// based on induction variable then CI is a candidate split condition.
- Value *V0 = CI->getOperand(0);
- Value *V1 = CI->getOperand(1);
-
- SCEVHandle SH0 = SE->getSCEV(V0);
- SCEVHandle SH1 = SE->getSCEV(V1);
-
- if (SH0->isLoopInvariant(L) && isa<SCEVAddRecExpr>(SH1)) {
- SD.SplitValue = V0;
- SD.SplitCondition = CI;
- if (PHINode *PN = dyn_cast<PHINode>(V1)) {
- if (PN == IndVar)
- SplitData.push_back(SD);
- }
- else if (Instruction *Insn = dyn_cast<Instruction>(V1)) {
- if (IndVarIncrement && IndVarIncrement == Insn)
- SplitData.push_back(SD);
- }
+ if (safeICmpInst(CI, SD))
+ SplitData.push_back(SD);
+ }
+}
+
+// safeIcmpInst - CI is considered safe instruction if one of the operand
+// is SCEVAddRecExpr based on induction variable and other operand is
+// loop invariant. If CI is safe then populate SplitInfo object SD appropriately
+// and return true;
+bool LoopIndexSplit::safeICmpInst(ICmpInst *CI, SplitInfo &SD) {
+
+ Value *V0 = CI->getOperand(0);
+ Value *V1 = CI->getOperand(1);
+
+ SCEVHandle SH0 = SE->getSCEV(V0);
+ SCEVHandle SH1 = SE->getSCEV(V1);
+
+ if (SH0->isLoopInvariant(L) && isa<SCEVAddRecExpr>(SH1)) {
+ SD.SplitValue = V0;
+ SD.SplitCondition = CI;
+ if (PHINode *PN = dyn_cast<PHINode>(V1)) {
+ if (PN == IndVar)
+ return true;
}
- else if (SH1->isLoopInvariant(L) && isa<SCEVAddRecExpr>(SH0)) {
- SD.SplitValue = V1;
- SD.SplitCondition = CI;
- if (PHINode *PN = dyn_cast<PHINode>(V0)) {
- if (PN == IndVar)
- SplitData.push_back(SD);
- }
- else if (Instruction *Insn = dyn_cast<Instruction>(V0)) {
- if (IndVarIncrement && IndVarIncrement == Insn)
- SplitData.push_back(SD);
- }
+ else if (Instruction *Insn = dyn_cast<Instruction>(V1)) {
+ if (IndVarIncrement && IndVarIncrement == Insn)
+ return true;
}
}
+ else if (SH1->isLoopInvariant(L) && isa<SCEVAddRecExpr>(SH0)) {
+ SD.SplitValue = V1;
+ SD.SplitCondition = CI;
+ if (PHINode *PN = dyn_cast<PHINode>(V0)) {
+ if (PN == IndVar)
+ return true;
+ }
+ else if (Instruction *Insn = dyn_cast<Instruction>(V0)) {
+ if (IndVarIncrement && IndVarIncrement == Insn)
+ return true;
+ }
+ }
+
+ return false;
}
/// processOneIterationLoop - Current loop L contains compare instruction
if (!safeExitingBlock(SD, ExitCondition->getParent()))
return false;
+ // Filter loops where split condition's false branch is not empty.
+ if (ExitCondition->getParent() != Header->getTerminator()->getSuccessor(1))
+ return false;
+
+ // If split condition is not safe then do not process this loop.
+ // For example,
+ // for(int i = 0; i < N; i++) {
+ // if ( i == XYZ) {
+ // A;
+ // else
+ // B;
+ // }
+ // C;
+ // D;
+ // }
+ if (!safeSplitCondition(SD))
+ return false;
+
+ BasicBlock *Latch = L->getLoopLatch();
+ BranchInst *BR = dyn_cast<BranchInst>(Latch->getTerminator());
+ if (!BR)
+ return false;
+
// Update CFG.
// Replace index variable with split value in loop body. Loop body is executed
IndVar->replaceAllUsesWith(SD.SplitValue);
// Remove Latch to Header edge.
- BasicBlock *Latch = L->getLoopLatch();
BasicBlock *LatchSucc = NULL;
- BranchInst *BR = dyn_cast<BranchInst>(Latch->getTerminator());
- if (!BR)
- return false;
Header->removePredecessor(Latch);
for (succ_iterator SI = succ_begin(Latch), E = succ_end(Latch);
SI != E; ++SI) {
ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
SD.SplitValue, ExitValue, "lisplit",
Terminator);
- Instruction *NSplitCond = BinaryOperator::createAnd(C1, C2, "lisplit",
+ Instruction *NSplitCond = BinaryOperator::CreateAnd(C1, C2, "lisplit",
Terminator);
SD.SplitCondition->replaceAllUsesWith(NSplitCond);
SD.SplitCondition->eraseFromParent();
if (isa<PHINode>(I) || I == LTerminator)
continue;
- if (I == IndVarIncrement)
- I->replaceAllUsesWith(ExitValue);
- else
+ if (I == IndVarIncrement) {
+ // Replace induction variable increment if it is not used outside
+ // the loop.
+ bool UsedOutsideLoop = false;
+ for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
+ UI != E; ++UI) {
+ if (Instruction *Use = dyn_cast<Instruction>(UI))
+ if (!L->contains(Use->getParent())) {
+ UsedOutsideLoop = true;
+ break;
+ }
+ }
+ if (!UsedOutsideLoop) {
+ I->replaceAllUsesWith(ExitValue);
+ I->eraseFromParent();
+ }
+ }
+ else {
I->replaceAllUsesWith(UndefValue::get(I->getType()));
- I->eraseFromParent();
+ I->eraseFromParent();
+ }
}
LPM->deleteLoopFromQueue(L);
continue;
// Check if I is induction variable increment instruction.
- if (!IndVarIncrement && I->getOpcode() == Instruction::Add) {
+ if (I->getOpcode() == Instruction::Add) {
Value *Op0 = I->getOperand(0);
Value *Op1 = I->getOperand(1);
if ((PN = dyn_cast<PHINode>(Op0))) {
if ((CI = dyn_cast<ConstantInt>(Op1)))
- IndVarIncrement = I;
+ if (CI->isOne()) {
+ if (!IndVarIncrement && PN == IndVar)
+ IndVarIncrement = I;
+ // else this is another loop induction variable
+ continue;
+ }
} else
if ((PN = dyn_cast<PHINode>(Op1))) {
if ((CI = dyn_cast<ConstantInt>(Op0)))
- IndVarIncrement = I;
+ if (CI->isOne()) {
+ if (!IndVarIncrement && PN == IndVar)
+ IndVarIncrement = I;
+ // else this is another loop induction variable
+ continue;
+ }
}
-
- if (IndVarIncrement && PN == IndVar && CI->isOne())
- continue;
- }
+ }
// I is an Exit condition if next instruction is block terminator.
// Exit condition is OK if it compares loop invariant exit value,
return true;
}
+void LoopIndexSplit::updateLoopBounds(ICmpInst *CI) {
+
+ Value *V0 = CI->getOperand(0);
+ Value *V1 = CI->getOperand(1);
+ Value *NV = NULL;
+
+ SCEVHandle SH0 = SE->getSCEV(V0);
+
+ if (SH0->isLoopInvariant(L))
+ NV = V0;
+ else
+ NV = V1;
+
+ if (ExitCondition->getPredicate() == ICmpInst::ICMP_SGT
+ || ExitCondition->getPredicate() == ICmpInst::ICMP_UGT
+ || ExitCondition->getPredicate() == ICmpInst::ICMP_SGE
+ || ExitCondition->getPredicate() == ICmpInst::ICMP_UGE) {
+ ExitCondition->swapOperands();
+ if (ExitValueNum)
+ ExitValueNum = 0;
+ else
+ ExitValueNum = 1;
+ }
+
+ Value *NUB = NULL;
+ Value *NLB = NULL;
+ Value *UB = ExitCondition->getOperand(ExitValueNum);
+ const Type *Ty = NV->getType();
+ bool Sign = ExitCondition->isSignedPredicate();
+ BasicBlock *Preheader = L->getLoopPreheader();
+ Instruction *PHTerminator = Preheader->getTerminator();
+
+ assert (NV && "Unexpected value");
+
+ switch (CI->getPredicate()) {
+ case ICmpInst::ICMP_ULE:
+ case ICmpInst::ICMP_SLE:
+ // for (i = LB; i < UB; ++i)
+ // if (i <= NV && ...)
+ // LOOP_BODY
+ //
+ // is transformed into
+ // NUB = min (NV+1, UB)
+ // for (i = LB; i < NUB ; ++i)
+ // LOOP_BODY
+ //
+ if (ExitCondition->getPredicate() == ICmpInst::ICMP_SLT
+ || ExitCondition->getPredicate() == ICmpInst::ICMP_ULT) {
+ Value *A = BinaryOperator::CreateAdd(NV, ConstantInt::get(Ty, 1, Sign),
+ "lsplit.add", PHTerminator);
+ Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
+ A, UB,"lsplit,c", PHTerminator);
+ NUB = SelectInst::Create(C, A, UB, "lsplit.nub", PHTerminator);
+ }
+
+ // for (i = LB; i <= UB; ++i)
+ // if (i <= NV && ...)
+ // LOOP_BODY
+ //
+ // is transformed into
+ // NUB = min (NV, UB)
+ // for (i = LB; i <= NUB ; ++i)
+ // LOOP_BODY
+ //
+ else if (ExitCondition->getPredicate() == ICmpInst::ICMP_SLE
+ || ExitCondition->getPredicate() == ICmpInst::ICMP_ULE) {
+ Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
+ NV, UB, "lsplit.c", PHTerminator);
+ NUB = SelectInst::Create(C, NV, UB, "lsplit.nub", PHTerminator);
+ }
+ break;
+ case ICmpInst::ICMP_ULT:
+ case ICmpInst::ICMP_SLT:
+ // for (i = LB; i < UB; ++i)
+ // if (i < NV && ...)
+ // LOOP_BODY
+ //
+ // is transformed into
+ // NUB = min (NV, UB)
+ // for (i = LB; i < NUB ; ++i)
+ // LOOP_BODY
+ //
+ if (ExitCondition->getPredicate() == ICmpInst::ICMP_SLT
+ || ExitCondition->getPredicate() == ICmpInst::ICMP_ULT) {
+ Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
+ NV, UB, "lsplit.c", PHTerminator);
+ NUB = SelectInst::Create(C, NV, UB, "lsplit.nub", PHTerminator);
+ }
+
+ // for (i = LB; i <= UB; ++i)
+ // if (i < NV && ...)
+ // LOOP_BODY
+ //
+ // is transformed into
+ // NUB = min (NV -1 , UB)
+ // for (i = LB; i <= NUB ; ++i)
+ // LOOP_BODY
+ //
+ else if (ExitCondition->getPredicate() == ICmpInst::ICMP_SLE
+ || ExitCondition->getPredicate() == ICmpInst::ICMP_ULE) {
+ Value *S = BinaryOperator::CreateSub(NV, ConstantInt::get(Ty, 1, Sign),
+ "lsplit.add", PHTerminator);
+ Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
+ S, UB, "lsplit.c", PHTerminator);
+ NUB = SelectInst::Create(C, S, UB, "lsplit.nub", PHTerminator);
+ }
+ break;
+ case ICmpInst::ICMP_UGE:
+ case ICmpInst::ICMP_SGE:
+ // for (i = LB; i (< or <=) UB; ++i)
+ // if (i >= NV && ...)
+ // LOOP_BODY
+ //
+ // is transformed into
+ // NLB = max (NV, LB)
+ // for (i = NLB; i (< or <=) UB ; ++i)
+ // LOOP_BODY
+ //
+ {
+ Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
+ NV, StartValue, "lsplit.c", PHTerminator);
+ NLB = SelectInst::Create(C, StartValue, NV, "lsplit.nlb", PHTerminator);
+ }
+ break;
+ case ICmpInst::ICMP_UGT:
+ case ICmpInst::ICMP_SGT:
+ // for (i = LB; i (< or <=) UB; ++i)
+ // if (i > NV && ...)
+ // LOOP_BODY
+ //
+ // is transformed into
+ // NLB = max (NV+1, LB)
+ // for (i = NLB; i (< or <=) UB ; ++i)
+ // LOOP_BODY
+ //
+ {
+ Value *A = BinaryOperator::CreateAdd(NV, ConstantInt::get(Ty, 1, Sign),
+ "lsplit.add", PHTerminator);
+ Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
+ A, StartValue, "lsplit.c", PHTerminator);
+ NLB = SelectInst::Create(C, StartValue, A, "lsplit.nlb", PHTerminator);
+ }
+ break;
+ default:
+ assert ( 0 && "Unexpected split condition predicate");
+ }
+
+ if (NLB) {
+ unsigned i = IndVar->getBasicBlockIndex(Preheader);
+ IndVar->setIncomingValue(i, NLB);
+ }
+
+ if (NUB) {
+ ExitCondition->setOperand(ExitValueNum, NUB);
+ }
+}
+/// updateLoopIterationSpace - Current loop body is covered by an AND
+/// instruction whose operands compares induction variables with loop
+/// invariants. If possible, hoist this check outside the loop by
+/// updating appropriate start and end values for induction variable.
+bool LoopIndexSplit::updateLoopIterationSpace(SplitInfo &SD) {
+ BasicBlock *Header = L->getHeader();
+ BasicBlock *ExitingBlock = ExitCondition->getParent();
+ BasicBlock *SplitCondBlock = SD.SplitCondition->getParent();
+
+ ICmpInst *Op0 = cast<ICmpInst>(SD.SplitCondition->getOperand(0));
+ ICmpInst *Op1 = cast<ICmpInst>(SD.SplitCondition->getOperand(1));
+
+ if (Op0->getPredicate() == ICmpInst::ICMP_EQ
+ || Op0->getPredicate() == ICmpInst::ICMP_NE
+ || Op0->getPredicate() == ICmpInst::ICMP_EQ
+ || Op0->getPredicate() == ICmpInst::ICMP_NE)
+ return false;
+
+ // Check if SplitCondition dominates entire loop body
+ // or not.
+
+ // If SplitCondition is not in loop header then this loop is not suitable
+ // for this transformation.
+ if (SD.SplitCondition->getParent() != Header)
+ return false;
+
+ // If loop header includes loop variant instruction operands then
+ // this loop may not be eliminated.
+ Instruction *Terminator = Header->getTerminator();
+ for(BasicBlock::iterator BI = Header->begin(), BE = Header->end();
+ BI != BE; ++BI) {
+ Instruction *I = BI;
+
+ // PHI Nodes are OK.
+ if (isa<PHINode>(I))
+ continue;
+
+ // SplitCondition itself is OK.
+ if (I == SD.SplitCondition)
+ continue;
+ if (I == Op0 || I == Op1)
+ continue;
+
+ // Induction variable is OK.
+ if (I == IndVar)
+ continue;
+
+ // Induction variable increment is OK.
+ if (I == IndVarIncrement)
+ continue;
+
+ // Terminator is also harmless.
+ if (I == Terminator)
+ continue;
+
+ // Otherwise we have a instruction that may not be safe.
+ return false;
+ }
+
+ // If Exiting block includes loop variant instructions then this
+ // loop may not be eliminated.
+ if (!safeExitingBlock(SD, ExitCondition->getParent()))
+ return false;
+
+ // Verify that loop exiting block has only two predecessor, where one predecessor
+ // is split condition block. The other predecessor will become exiting block's
+ // dominator after CFG is updated. TODO : Handle CFG's where exiting block has
+ // more then two predecessors. This requires extra work in updating dominator
+ // information.
+ BasicBlock *ExitingBBPred = NULL;
+ for (pred_iterator PI = pred_begin(ExitingBlock), PE = pred_end(ExitingBlock);
+ PI != PE; ++PI) {
+ BasicBlock *BB = *PI;
+ if (SplitCondBlock == BB)
+ continue;
+ if (ExitingBBPred)
+ return false;
+ else
+ ExitingBBPred = BB;
+ }
+
+ // Update loop bounds to absorb Op0 check.
+ updateLoopBounds(Op0);
+ // Update loop bounds to absorb Op1 check.
+ updateLoopBounds(Op1);
+
+ // Update CFG
+
+ // Unconditionally connect split block to its remaining successor.
+ BranchInst *SplitTerminator =
+ cast<BranchInst>(SplitCondBlock->getTerminator());
+ BasicBlock *Succ0 = SplitTerminator->getSuccessor(0);
+ BasicBlock *Succ1 = SplitTerminator->getSuccessor(1);
+ if (Succ0 == ExitCondition->getParent())
+ SplitTerminator->setUnconditionalDest(Succ1);
+ else
+ SplitTerminator->setUnconditionalDest(Succ0);
+
+ // Remove split condition.
+ SD.SplitCondition->eraseFromParent();
+ if (Op0->use_begin() == Op0->use_end())
+ Op0->eraseFromParent();
+ if (Op1->use_begin() == Op1->use_end())
+ Op1->eraseFromParent();
+
+ BranchInst *ExitInsn =
+ dyn_cast<BranchInst>(ExitingBlock->getTerminator());
+ assert (ExitInsn && "Unable to find suitable loop exit branch");
+ BasicBlock *ExitBlock = ExitInsn->getSuccessor(1);
+ if (L->contains(ExitBlock))
+ ExitBlock = ExitInsn->getSuccessor(0);
+
+ // Update domiantor info. Now, ExitingBlock has only one predecessor,
+ // ExitingBBPred, and it is ExitingBlock's immediate domiantor.
+ DT->changeImmediateDominator(ExitingBlock, ExitingBBPred);
+
+ // If ExitingBlock is a member of loop BB's DF list then replace it with
+ // loop header and exit block.
+ for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
+ I != E; ++I) {
+ BasicBlock *BB = *I;
+ if (BB == Header || BB == ExitingBlock)
+ continue;
+ DominanceFrontier::iterator BBDF = DF->find(BB);
+ DominanceFrontier::DomSetType::iterator DomSetI = BBDF->second.begin();
+ DominanceFrontier::DomSetType::iterator DomSetE = BBDF->second.end();
+ while (DomSetI != DomSetE) {
+ DominanceFrontier::DomSetType::iterator CurrentItr = DomSetI;
+ ++DomSetI;
+ BasicBlock *DFBB = *CurrentItr;
+ if (DFBB == ExitingBlock) {
+ BBDF->second.erase(DFBB);
+ BBDF->second.insert(Header);
+ if (Header != ExitingBlock)
+ BBDF->second.insert(ExitBlock);
+ }
+ }
+ }
+
+ return true;
+}
+
+
/// removeBlocks - Remove basic block DeadBB and all blocks dominated by DeadBB.
/// This routine is used to remove split condition's dead branch, dominated by
/// DeadBB. LiveBB dominates split conidition's other branch.
while (!WorkList.empty()) {
BasicBlock *BB = WorkList.back(); WorkList.pop_back();
for(BasicBlock::iterator BBI = BB->begin(), BBE = BB->end();
- BBI != BBE; ++BBI) {
+ BBI != BBE; ) {
Instruction *I = BBI;
+ ++BBI;
I->replaceAllUsesWith(UndefValue::get(I->getType()));
I->eraseFromParent();
}
bool LoopIndexSplit::safeSplitCondition(SplitInfo &SD) {
BasicBlock *SplitCondBlock = SD.SplitCondition->getParent();
-
- // Unable to handle triange loops at the moment.
- // In triangle loop, split condition is in header and one of the
- // the split destination is loop latch. If split condition is EQ
- // then such loops are already handle in processOneIterationLoop().
- BasicBlock *Latch = L->getLoopLatch();
+ BasicBlock *Latch = L->getLoopLatch();
BranchInst *SplitTerminator =
cast<BranchInst>(SplitCondBlock->getTerminator());
BasicBlock *Succ0 = SplitTerminator->getSuccessor(0);
BasicBlock *Succ1 = SplitTerminator->getSuccessor(1);
- if (L->getHeader() == SplitCondBlock
- && (Latch == Succ0 || Latch == Succ1))
- return false;
-
- // If split condition branches heads do not have single predecessor,
- // SplitCondBlock, then is not possible to remove inactive branch.
- if (!Succ0->getSinglePredecessor() || !Succ1->getSinglePredecessor())
+
+ // If split block does not dominate the latch then this is not a diamond.
+ // Such loop may not benefit from index split.
+ if (!DT->dominates(SplitCondBlock, Latch))
return false;
// Finally this split condition is safe only if merge point for
Value *AEV = SD.SplitValue;
Value *BSV = SD.SplitValue;
+ if (ExitCondition->getPredicate() == ICmpInst::ICMP_SGT
+ || ExitCondition->getPredicate() == ICmpInst::ICMP_UGT
+ || ExitCondition->getPredicate() == ICmpInst::ICMP_SGE
+ || ExitCondition->getPredicate() == ICmpInst::ICMP_UGE) {
+ ExitCondition->swapOperands();
+ if (ExitValueNum)
+ ExitValueNum = 0;
+ else
+ ExitValueNum = 1;
+ }
+
switch (ExitCondition->getPredicate()) {
case ICmpInst::ICMP_SGT:
case ICmpInst::ICMP_UGT:
// A;
// for (i = max(LB, BSV); i < UB; ++i)
// B;
- BSV = BinaryOperator::createAdd(SD.SplitValue,
+ BSV = BinaryOperator::CreateAdd(SD.SplitValue,
ConstantInt::get(Ty, 1, Sign),
"lsplit.add", PHTerminator);
AEV = BSV;
// B;
// for (i = max(LB, BSV); i < UB; ++i)
// A;
- BSV = BinaryOperator::createAdd(SD.SplitValue,
+ BSV = BinaryOperator::CreateAdd(SD.SplitValue,
ConstantInt::get(Ty, 1, Sign),
"lsplit.add", PHTerminator);
AEV = BSV;
// A;
// for (i = max(LB, BSV); i <= UB; ++i)
// B;
- AEV = BinaryOperator::createSub(SD.SplitValue,
+ AEV = BinaryOperator::CreateSub(SD.SplitValue,
ConstantInt::get(Ty, 1, Sign),
"lsplit.sub", PHTerminator);
break;
// A;
// for (i = max(LB, BSV); i <= UB; ++i)
// B;
- BSV = BinaryOperator::createAdd(SD.SplitValue,
+ BSV = BinaryOperator::CreateAdd(SD.SplitValue,
ConstantInt::get(Ty, 1, Sign),
"lsplit.add", PHTerminator);
break;
// B;
// for (i = max(LB, BSV); i <= UB; ++i)
// A;
- BSV = BinaryOperator::createAdd(SD.SplitValue,
+ BSV = BinaryOperator::CreateAdd(SD.SplitValue,
ConstantInt::get(Ty, 1, Sign),
"lsplit.add", PHTerminator);
break;
// B;
// for (i = max(LB, BSV); i <= UB; ++i)
// A;
- AEV = BinaryOperator::createSub(SD.SplitValue,
+ AEV = BinaryOperator::CreateSub(SD.SplitValue,
ConstantInt::get(Ty, 1, Sign),
"lsplit.sub", PHTerminator);
break;
// values in original loop's preheader.
// A_ExitValue = min(SplitValue, OrignalLoopExitValue)
// B_StartValue = max(SplitValue, OriginalLoopStartValue)
+ Instruction *InsertPt = L->getHeader()->getFirstNonPHI();
+
+ // If ExitValue operand is also defined in Loop header then
+ // insert new ExitValue after this operand definition.
+ if (Instruction *EVN =
+ dyn_cast<Instruction>(ExitCondition->getOperand(ExitValueNum))) {
+ if (!isa<PHINode>(EVN))
+ if (InsertPt->getParent() == EVN->getParent()) {
+ BasicBlock::iterator LHBI = L->getHeader()->begin();
+ BasicBlock::iterator LHBE = L->getHeader()->end();
+ for(;LHBI != LHBE; ++LHBI) {
+ Instruction *I = LHBI;
+ if (I == EVN)
+ break;
+ }
+ InsertPt = ++LHBI;
+ }
+ }
Value *C1 = new ICmpInst(Sign ?
ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
AEV,
ExitCondition->getOperand(ExitValueNum),
- "lsplit.ev", PHTerminator);
- SD.A_ExitValue = new SelectInst(C1, AEV,
- ExitCondition->getOperand(ExitValueNum),
- "lsplit.ev", PHTerminator);
-
+ "lsplit.ev", InsertPt);
+
+ SD.A_ExitValue = SelectInst::Create(C1, AEV,
+ ExitCondition->getOperand(ExitValueNum),
+ "lsplit.ev", InsertPt);
+
Value *C2 = new ICmpInst(Sign ?
ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
BSV, StartValue, "lsplit.sv",
PHTerminator);
- SD.B_StartValue = new SelectInst(C2, StartValue, BSV,
- "lsplit.sv", PHTerminator);
+ SD.B_StartValue = SelectInst::Create(C2, StartValue, BSV,
+ "lsplit.sv", PHTerminator);
}
/// splitLoop - Split current loop L in two loops using split information
if (!safeSplitCondition(SD))
return false;
+ BasicBlock *SplitCondBlock = SD.SplitCondition->getParent();
+
+ // Unable to handle triangle loops at the moment.
+ // In triangle loop, split condition is in header and one of the
+ // the split destination is loop latch. If split condition is EQ
+ // then such loops are already handle in processOneIterationLoop().
+ BasicBlock *Latch = L->getLoopLatch();
+ BranchInst *SplitTerminator =
+ cast<BranchInst>(SplitCondBlock->getTerminator());
+ BasicBlock *Succ0 = SplitTerminator->getSuccessor(0);
+ BasicBlock *Succ1 = SplitTerminator->getSuccessor(1);
+ if (L->getHeader() == SplitCondBlock
+ && (Latch == Succ0 || Latch == Succ1))
+ return false;
+
+ // If split condition branches heads do not have single predecessor,
+ // SplitCondBlock, then is not possible to remove inactive branch.
+ if (!Succ0->getSinglePredecessor() || !Succ1->getSinglePredecessor())
+ return false;
+
+ // If Exiting block includes loop variant instructions then this
+ // loop may not be split safely.
+ if (!safeExitingBlock(SD, ExitCondition->getParent()))
+ return false;
+
// After loop is cloned there are two loops.
//
// First loop, referred as ALoop, executes first part of loop's iteration
PN->addIncoming(SD.B_StartValue, A_ExitingBlock);
else {
PHINode *OrigPN = cast<PHINode>(InverseMap[PN]);
- Value *V2 = OrigPN->getIncomingValueForBlock(A_ExitingBlock);
+ Value *V2 = NULL;
+ // If loop header is also loop exiting block then
+ // OrigPN is incoming value for B loop header.
+ if (A_ExitingBlock == L->getHeader())
+ V2 = OrigPN;
+ else
+ V2 = OrigPN->getIncomingValueForBlock(A_ExitingBlock);
PN->addIncoming(V2, A_ExitingBlock);
}
} else
BI != BE; ++BI) {
if (PHINode *PN = dyn_cast<PHINode>(BI)) {
Value *V1 = PN->getIncomingValueForBlock(A_ExitBlock);
- PHINode *newPHI = new PHINode(PN->getType(), PN->getName());
+ PHINode *newPHI = PHINode::Create(PN->getType(), PN->getName());
newPHI->addIncoming(V1, A_ExitingBlock);
A_ExitBlock->getInstList().push_front(newPHI);
PN->removeIncomingValue(A_ExitBlock);
// destination.
BranchInst *ExitingBR = cast<BranchInst>(ExitingBB->getTerminator());
ExitingBR->moveBefore(CurrentBR);
- if (ExitingBR->getSuccessor(0) == ExitBB)
+ BasicBlock *OrigDestBB = NULL;
+ if (ExitingBR->getSuccessor(0) == ExitBB) {
+ OrigDestBB = ExitingBR->getSuccessor(1);
ExitingBR->setSuccessor(1, ActiveBB);
- else
+ }
+ else {
+ OrigDestBB = ExitingBR->getSuccessor(0);
ExitingBR->setSuccessor(0, ActiveBB);
+ }
// Remove split condition and current split condition branch.
SC->eraseFromParent();
CurrentBR->eraseFromParent();
- // Connect exiting block to split condition block.
- new BranchInst(CondBB, ExitingBB);
+ // Connect exiting block to original destination.
+ BranchInst::Create(OrigDestBB, ExitingBB);
// Update PHINodes
- updatePHINodes(ExitBB, ExitingBB, CondBB, IV, IVAdd);
+ updatePHINodes(ExitBB, ExitingBB, CondBB, IV, IVAdd, LP);
// Fix dominator info.
// ExitBB is now dominated by CondBB
/// - ExitBB's single predecessor was Latch
/// - Latch's second successor was Header
/// Now
-/// - ExitBB's single predecessor was Header
-/// - Latch's one and only successor was Header
+/// - ExitBB's single predecessor is Header
+/// - Latch's one and only successor is Header
///
/// Update ExitBB PHINodes' to reflect this change.
void LoopIndexSplit::updatePHINodes(BasicBlock *ExitBB, BasicBlock *Latch,
BasicBlock *Header,
- PHINode *IV, Instruction *IVIncrement) {
+ PHINode *IV, Instruction *IVIncrement,
+ Loop *LP) {
for (BasicBlock::iterator BI = ExitBB->begin(), BE = ExitBB->end();
- BI != BE; ++BI) {
+ BI != BE; ) {
PHINode *PN = dyn_cast<PHINode>(BI);
+ ++BI;
if (!PN)
break;
Value *V = PN->getIncomingValueForBlock(Latch);
if (PHINode *PHV = dyn_cast<PHINode>(V)) {
- // PHV is in Latch. PHV has two uses, one use is in ExitBB PHINode
- // (i.e. PN :)).
- // The second use is in Header and it is new incoming value for PN.
- PHINode *U1 = NULL;
- PHINode *U2 = NULL;
+ // PHV is in Latch. PHV has one use is in ExitBB PHINode. And one use
+ // in Header which is new incoming value for PN.
Value *NewV = NULL;
for (Value::use_iterator UI = PHV->use_begin(), E = PHV->use_end();
- UI != E; ++UI) {
- if (!U1)
- U1 = cast<PHINode>(*UI);
- else if (!U2)
- U2 = cast<PHINode>(*UI);
- else
- assert ( 0 && "Unexpected third use of this PHINode");
- }
- assert (U1 && U2 && "Unable to find two uses");
-
- if (U1->getParent() == Header)
- NewV = U1;
- else
- NewV = U2;
- PN->addIncoming(NewV, Header);
+ UI != E; ++UI)
+ if (PHINode *U = dyn_cast<PHINode>(*UI))
+ if (LP->contains(U->getParent())) {
+ NewV = U;
+ break;
+ }
+
+ // Add incoming value from header only if PN has any use inside the loop.
+ if (NewV)
+ PN->addIncoming(NewV, Header);
} else if (Instruction *PHI = dyn_cast<Instruction>(V)) {
// If this instruction is IVIncrement then IV is new incoming value
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