//
// 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.
//
//===----------------------------------------------------------------------===//
//
class SplitInfo {
public:
- SplitInfo() : SplitValue(NULL), SplitCondition(NULL) {}
+ SplitInfo() : SplitValue(NULL), SplitCondition(NULL),
+ UseTrueBranchFirst(true), A_ExitValue(NULL),
+ B_StartValue(NULL) {}
// Induction variable's range is split at this value.
Value *SplitValue;
- // This compare instruction compares IndVar against SplitValue.
- ICmpInst *SplitCondition;
+ // This instruction compares IndVar against SplitValue.
+ Instruction *SplitCondition;
+
+ // True if after loop index split, first loop will execute split condition's
+ // true branch.
+ bool UseTrueBranchFirst;
+
+ // Exit value for first loop after loop split.
+ Value *A_ExitValue;
+
+ // Start value for second loop after loop split.
+ Value *B_StartValue;
// Clear split info.
void clear() {
SplitValue = NULL;
SplitCondition = NULL;
+ UseTrueBranchFirst = true;
+ A_ExitValue = NULL;
+ B_StartValue = NULL;
}
};
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);
/// DeadBB. LiveBB dominates split conidition's other branch.
void removeBlocks(BasicBlock *DeadBB, Loop *LP, BasicBlock *LiveBB);
- /// Find cost of spliting loop L.
- unsigned findSplitCost(Loop *L, SplitInfo &SD);
-
/// safeSplitCondition - Return true if it is possible to
/// split loop using given split condition.
bool safeSplitCondition(SplitInfo &SD);
+ /// calculateLoopBounds - ALoop exit value and BLoop start values are calculated
+ /// based on split value.
+ void calculateLoopBounds(SplitInfo &SD);
+
+ /// updatePHINodes - CFG has been changed.
+ /// Before
+ /// - 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
+ ///
+ /// Update ExitBB PHINodes' to reflect this change.
+ void updatePHINodes(BasicBlock *ExitBB, BasicBlock *Latch,
+ BasicBlock *Header,
+ PHINode *IV, Instruction *IVIncrement, Loop *LP);
+
+ /// moveExitCondition - Move exit condition EC into split condition block CondBB.
+ void moveExitCondition(BasicBlock *CondBB, BasicBlock *ActiveBB,
+ BasicBlock *ExitBB, ICmpInst *EC, ICmpInst *SC,
+ PHINode *IV, Instruction *IVAdd, Loop *LP);
+
/// splitLoop - Split current loop L in two loops using split information
/// SD. Update dominator information. Maintain LCSSA form.
bool splitLoop(SplitInfo &SD);
for (SmallVector<SplitInfo, 4>::iterator SI = SplitData.begin(),
E = SplitData.end(); SI != E;) {
SplitInfo &SD = *SI;
- if (SD.SplitCondition->getPredicate() == ICmpInst::ICMP_EQ) {
+ ICmpInst *CI = dyn_cast<ICmpInst>(SD.SplitCondition);
+ 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;
++SI;
}
- unsigned MaxCost = 99;
- unsigned Index = 0;
- unsigned MostProfitableSDIndex = 0;
- for (SmallVector<SplitInfo, 4>::iterator SI = SplitData.begin(),
- E = SplitData.end(); SI != E; ++SI, ++Index) {
- SplitInfo SD = *SI;
-
- // ICM_EQs are already handled above.
- assert (SD.SplitCondition->getPredicate() != ICmpInst::ICMP_EQ &&
- "Unexpected split condition predicate");
-
- unsigned Cost = findSplitCost(L, SD);
- if (Cost < MaxCost)
- MostProfitableSDIndex = Index;
- }
+ if (SplitData.empty())
+ return false;
// Split most profitiable condition.
- if (!SplitData.empty())
- Changed = splitLoop(SplitData[MostProfitableSDIndex]);
+ // FIXME : Implement cost analysis.
+ unsigned MostProfitableSDIndex = 0;
+ Changed = splitLoop(SplitData[MostProfitableSDIndex]);
if (Changed)
++NumIndexSplit;
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 (!ExitingBlock)
return;
-
+
+ // If exiting block is neither loop header nor loop latch then this loop is
+ // not suitable.
+ if (ExitingBlock != L->getHeader() && ExitingBlock != L->getLoopLatch())
+ return;
+
// If exit block's terminator is conditional branch inst then we have found
// exit condition.
BranchInst *BR = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
ICmpInst *CI = dyn_cast<ICmpInst>(BR->getCondition());
if (!CI)
return;
-
+
+ // FIXME
+ if (CI->getPredicate() == ICmpInst::ICMP_EQ
+ || CI->getPredicate() == ICmpInst::ICMP_NE)
+ return;
+
ExitCondition = CI;
// Exit condition's one operand is loop invariant exit value and second
SplitInfo SD;
// Check all basic block's terminators.
-
for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
I != E; ++I) {
+ SD.clear();
BasicBlock *BB = *I;
// If this basic block does not terminate in a conditional branch
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)
- return;
+ continue;
+
+ if (CI->getPredicate() == ICmpInst::ICMP_NE)
+ continue;
+
+ // If split condition predicate is GT or GE then first execute
+ // false branch of split condition.
+ 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) {
// SplitCondition : icmp eq i32 IndVar, SplitValue
// into
// c1 = icmp uge i32 SplitValue, StartValue
- // c2 = icmp ult i32 vSplitValue, ExitValue
+ // c2 = icmp ult i32 SplitValue, ExitValue
// and i32 c1, c2
bool SignedPredicate = ExitCondition->isSignedPredicate();
Instruction *C1 = new ICmpInst(SignedPredicate ?
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;
}
-/// Find cost of spliting loop L. Cost is measured in terms of size growth.
-/// Size is growth is calculated based on amount of code duplicated in second
-/// loop.
-unsigned LoopIndexSplit::findSplitCost(Loop *L, SplitInfo &SD) {
+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;
+ }
- unsigned Cost = 0;
- BasicBlock *SDBlock = SD.SplitCondition->getParent();
+ 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 = new SelectInst (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 = new SelectInst (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 = new SelectInst (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 = new SelectInst (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 = new SelectInst (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 = new SelectInst (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 a block is not dominated by split condition block then
- // it must be duplicated in both loops.
- if (!DT->dominates(SDBlock, BB))
- Cost += BB->size();
+ 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 Cost;
+ 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();
}
/// split loop using given split condition.
bool LoopIndexSplit::safeSplitCondition(SplitInfo &SD) {
+ BasicBlock *SplitCondBlock = SD.SplitCondition->getParent();
+ BasicBlock *Latch = L->getLoopLatch();
+ BranchInst *SplitTerminator =
+ cast<BranchInst>(SplitCondBlock->getTerminator());
+ BasicBlock *Succ0 = SplitTerminator->getSuccessor(0);
+ BasicBlock *Succ1 = SplitTerminator->getSuccessor(1);
+
+ // Finally this split condition is safe only if merge point for
+ // split condition branch is loop latch. This check along with previous
+ // check, to ensure that exit condition is in either loop latch or header,
+ // filters all loops with non-empty loop body between merge point
+ // and exit condition.
+ DominanceFrontier::iterator Succ0DF = DF->find(Succ0);
+ assert (Succ0DF != DF->end() && "Unable to find Succ0 dominance frontier");
+ if (Succ0DF->second.count(Latch))
+ return true;
+
+ DominanceFrontier::iterator Succ1DF = DF->find(Succ1);
+ assert (Succ1DF != DF->end() && "Unable to find Succ1 dominance frontier");
+ if (Succ1DF->second.count(Latch))
+ return true;
+
+ return false;
+}
+
+/// calculateLoopBounds - ALoop exit value and BLoop start values are calculated
+/// based on split value.
+void LoopIndexSplit::calculateLoopBounds(SplitInfo &SD) {
+
+ ICmpInst *SC = cast<ICmpInst>(SD.SplitCondition);
+ ICmpInst::Predicate SP = SC->getPredicate();
+ const Type *Ty = SD.SplitValue->getType();
+ bool Sign = ExitCondition->isSignedPredicate();
+ BasicBlock *Preheader = L->getLoopPreheader();
+ Instruction *PHTerminator = Preheader->getTerminator();
+
+ // Initially use split value as upper loop bound for first loop and lower loop
+ // bound for second loop.
+ 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:
+ case ICmpInst::ICMP_SGE:
+ case ICmpInst::ICMP_UGE:
+ default:
+ assert (0 && "Unexpected exit condition predicate");
+
+ case ICmpInst::ICMP_SLT:
+ case ICmpInst::ICMP_ULT:
+ {
+ switch (SP) {
+ case ICmpInst::ICMP_SLT:
+ case ICmpInst::ICMP_ULT:
+ //
+ // for (i = LB; i < UB; ++i) { if (i < SV) A; else B; }
+ //
+ // is transformed into
+ // AEV = BSV = SV
+ // for (i = LB; i < min(UB, AEV); ++i)
+ // A;
+ // for (i = max(LB, BSV); i < UB; ++i);
+ // B;
+ break;
+ case ICmpInst::ICMP_SLE:
+ case ICmpInst::ICMP_ULE:
+ {
+ //
+ // for (i = LB; i < UB; ++i) { if (i <= SV) A; else B; }
+ //
+ // is transformed into
+ //
+ // AEV = SV + 1
+ // BSV = SV + 1
+ // for (i = LB; i < min(UB, AEV); ++i)
+ // A;
+ // for (i = max(LB, BSV); i < UB; ++i)
+ // B;
+ BSV = BinaryOperator::createAdd(SD.SplitValue,
+ ConstantInt::get(Ty, 1, Sign),
+ "lsplit.add", PHTerminator);
+ AEV = BSV;
+ }
+ break;
+ case ICmpInst::ICMP_SGE:
+ case ICmpInst::ICMP_UGE:
+ //
+ // for (i = LB; i < UB; ++i) { if (i >= SV) A; else B; }
+ //
+ // is transformed into
+ // AEV = BSV = SV
+ // for (i = LB; i < min(UB, AEV); ++i)
+ // B;
+ // for (i = max(BSV, LB); i < UB; ++i)
+ // A;
+ break;
+ case ICmpInst::ICMP_SGT:
+ case ICmpInst::ICMP_UGT:
+ {
+ //
+ // for (i = LB; i < UB; ++i) { if (i > SV) A; else B; }
+ //
+ // is transformed into
+ //
+ // BSV = AEV = SV + 1
+ // for (i = LB; i < min(UB, AEV); ++i)
+ // B;
+ // for (i = max(LB, BSV); i < UB; ++i)
+ // A;
+ BSV = BinaryOperator::createAdd(SD.SplitValue,
+ ConstantInt::get(Ty, 1, Sign),
+ "lsplit.add", PHTerminator);
+ AEV = BSV;
+ }
+ break;
+ default:
+ assert (0 && "Unexpected split condition predicate");
+ break;
+ } // end switch (SP)
+ }
+ break;
+ case ICmpInst::ICMP_SLE:
+ case ICmpInst::ICMP_ULE:
+ {
+ switch (SP) {
+ case ICmpInst::ICMP_SLT:
+ case ICmpInst::ICMP_ULT:
+ //
+ // for (i = LB; i <= UB; ++i) { if (i < SV) A; else B; }
+ //
+ // is transformed into
+ // AEV = SV - 1;
+ // BSV = SV;
+ // for (i = LB; i <= min(UB, AEV); ++i)
+ // A;
+ // for (i = max(LB, BSV); i <= UB; ++i)
+ // B;
+ AEV = BinaryOperator::createSub(SD.SplitValue,
+ ConstantInt::get(Ty, 1, Sign),
+ "lsplit.sub", PHTerminator);
+ break;
+ case ICmpInst::ICMP_SLE:
+ case ICmpInst::ICMP_ULE:
+ //
+ // for (i = LB; i <= UB; ++i) { if (i <= SV) A; else B; }
+ //
+ // is transformed into
+ // AEV = SV;
+ // BSV = SV + 1;
+ // for (i = LB; i <= min(UB, AEV); ++i)
+ // A;
+ // for (i = max(LB, BSV); i <= UB; ++i)
+ // B;
+ BSV = BinaryOperator::createAdd(SD.SplitValue,
+ ConstantInt::get(Ty, 1, Sign),
+ "lsplit.add", PHTerminator);
+ break;
+ case ICmpInst::ICMP_SGT:
+ case ICmpInst::ICMP_UGT:
+ //
+ // for (i = LB; i <= UB; ++i) { if (i > SV) A; else B; }
+ //
+ // is transformed into
+ // AEV = SV;
+ // BSV = SV + 1;
+ // for (i = LB; i <= min(AEV, UB); ++i)
+ // B;
+ // for (i = max(LB, BSV); i <= UB; ++i)
+ // A;
+ BSV = BinaryOperator::createAdd(SD.SplitValue,
+ ConstantInt::get(Ty, 1, Sign),
+ "lsplit.add", PHTerminator);
+ break;
+ case ICmpInst::ICMP_SGE:
+ case ICmpInst::ICMP_UGE:
+ // ** TODO **
+ //
+ // for (i = LB; i <= UB; ++i) { if (i >= SV) A; else B; }
+ //
+ // is transformed into
+ // AEV = SV - 1;
+ // BSV = SV;
+ // for (i = LB; i <= min(AEV, UB); ++i)
+ // B;
+ // for (i = max(LB, BSV); i <= UB; ++i)
+ // A;
+ AEV = BinaryOperator::createSub(SD.SplitValue,
+ ConstantInt::get(Ty, 1, Sign),
+ "lsplit.sub", PHTerminator);
+ break;
+ default:
+ assert (0 && "Unexpected split condition predicate");
+ break;
+ } // end switch (SP)
+ }
+ break;
+ }
+
+ // Calculate ALoop induction variable's new exiting value and
+ // BLoop induction variable's new starting value. Calculuate these
+ // 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", InsertPt);
+
+ SD.A_ExitValue = new SelectInst(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);
+}
+
+/// splitLoop - Split current loop L in two loops using split information
+/// SD. Update dominator information. Maintain LCSSA form.
+bool LoopIndexSplit::splitLoop(SplitInfo &SD) {
+
+ if (!safeSplitCondition(SD))
+ return false;
+
BasicBlock *SplitCondBlock = SD.SplitCondition->getParent();
// Unable to handle triange loops at the moment.
if (L->getHeader() == SplitCondBlock
&& (Latch == Succ0 || Latch == Succ1))
return false;
-
- // If one of the split condition branch is post dominating other then loop
- // index split is not appropriate.
- if (DT->dominates(Succ0, Latch) || DT->dominates(Succ1, Latch))
- return false;
-
- // If one of the split condition branch is a predecessor of the other
- // split condition branch head then do not split loop on this condition.
- for(pred_iterator PI = pred_begin(Succ0), PE = pred_end(Succ0);
- PI != PE; ++PI)
- if (Succ1 == *PI)
- return false;
- for(pred_iterator PI = pred_begin(Succ1), PE = pred_end(Succ1);
- PI != PE; ++PI)
- if (Succ0 == *PI)
- return false;
- return true;
-}
-
-/// splitLoop - Split current loop L in two loops using split information
-/// SD. Update dominator information. Maintain LCSSA form.
-bool LoopIndexSplit::splitLoop(SplitInfo &SD) {
+ // 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 (!safeSplitCondition(SD))
+ // 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.
//
// ALoop's exit edge enters BLoop's header through a forwarding block which
// acts as a BLoop's preheader.
+ BasicBlock *Preheader = L->getLoopPreheader();
- //[*] Calculate ALoop induction variable's new exiting value and
- // BLoop induction variable's new starting value. Calculuate these
- // values in original loop's preheader.
- // A_ExitValue = min(SplitValue, OrignalLoopExitValue)
- // B_StartValue = max(SplitValue, OriginalLoopStartValue)
- Value *A_ExitValue = NULL;
- Value *B_StartValue = NULL;
- if (isa<ConstantInt>(SD.SplitValue)) {
- A_ExitValue = SD.SplitValue;
- B_StartValue = SD.SplitValue;
- }
- else {
- BasicBlock *Preheader = L->getLoopPreheader();
- Instruction *PHTerminator = Preheader->getTerminator();
- bool SignedPredicate = ExitCondition->isSignedPredicate();
- Value *C1 = new ICmpInst(SignedPredicate ?
- ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
- SD.SplitValue,
- ExitCondition->getOperand(ExitValueNum),
- "lsplit.ev", PHTerminator);
- A_ExitValue = new SelectInst(C1, SD.SplitValue,
- ExitCondition->getOperand(ExitValueNum),
- "lsplit.ev", PHTerminator);
-
- Value *C2 = new ICmpInst(SignedPredicate ?
- ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
- SD.SplitValue, StartValue, "lsplit.sv",
- PHTerminator);
- B_StartValue = new SelectInst(C2, StartValue, SD.SplitValue,
- "lsplit.sv", PHTerminator);
- }
+ // Calculate ALoop induction variable's new exiting value and
+ // BLoop induction variable's new starting value.
+ calculateLoopBounds(SD);
//[*] Clone loop.
DenseMap<const Value *, Value *> ValueMap;
Loop *BLoop = CloneLoop(L, LPM, LI, ValueMap, this);
+ Loop *ALoop = L;
BasicBlock *B_Header = BLoop->getHeader();
//[*] ALoop's exiting edge BLoop's header.
A_ExitInsn->setSuccessor(1, B_Header);
//[*] Update ALoop's exit value using new exit value.
- ExitCondition->setOperand(ExitValueNum, A_ExitValue);
+ ExitCondition->setOperand(ExitValueNum, SD.A_ExitValue);
// [*] Update BLoop's header phi nodes. Remove incoming PHINode's from
// original loop's preheader. Add incoming PHINode values from
} else
break;
}
- BasicBlock *Preheader = L->getLoopPreheader();
+
for (BasicBlock::iterator BI = B_Header->begin(), BE = B_Header->end();
BI != BE; ++BI) {
if (PHINode *PN = dyn_cast<PHINode>(BI)) {
// Add incoming value from A_ExitingBlock.
if (PN == B_IndVar)
- PN->addIncoming(B_StartValue, A_ExitingBlock);
+ 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
//[*] Eliminate split condition's inactive branch from ALoop.
BasicBlock *A_SplitCondBlock = SD.SplitCondition->getParent();
BranchInst *A_BR = cast<BranchInst>(A_SplitCondBlock->getTerminator());
- BasicBlock *A_InactiveBranch = A_BR->getSuccessor(1);
- BasicBlock *A_ActiveBranch = A_BR->getSuccessor(0);
- A_BR->setUnconditionalDest(A_BR->getSuccessor(0));
+ BasicBlock *A_InactiveBranch = NULL;
+ BasicBlock *A_ActiveBranch = NULL;
+ if (SD.UseTrueBranchFirst) {
+ A_ActiveBranch = A_BR->getSuccessor(0);
+ A_InactiveBranch = A_BR->getSuccessor(1);
+ } else {
+ A_ActiveBranch = A_BR->getSuccessor(1);
+ A_InactiveBranch = A_BR->getSuccessor(0);
+ }
+ A_BR->setUnconditionalDest(A_ActiveBranch);
removeBlocks(A_InactiveBranch, L, A_ActiveBranch);
//[*] Eliminate split condition's inactive branch in from BLoop.
BasicBlock *B_SplitCondBlock = cast<BasicBlock>(ValueMap[A_SplitCondBlock]);
BranchInst *B_BR = cast<BranchInst>(B_SplitCondBlock->getTerminator());
- BasicBlock *B_InactiveBranch = B_BR->getSuccessor(0);
- BasicBlock *B_ActiveBranch = B_BR->getSuccessor(1);
- B_BR->setUnconditionalDest(B_BR->getSuccessor(1));
+ BasicBlock *B_InactiveBranch = NULL;
+ BasicBlock *B_ActiveBranch = NULL;
+ if (SD.UseTrueBranchFirst) {
+ B_ActiveBranch = B_BR->getSuccessor(1);
+ B_InactiveBranch = B_BR->getSuccessor(0);
+ } else {
+ B_ActiveBranch = B_BR->getSuccessor(0);
+ B_InactiveBranch = B_BR->getSuccessor(1);
+ }
+ B_BR->setUnconditionalDest(B_ActiveBranch);
removeBlocks(B_InactiveBranch, BLoop, B_ActiveBranch);
+ BasicBlock *A_Header = L->getHeader();
+ if (A_ExitingBlock == A_Header)
+ return true;
+
+ //[*] Move exit condition into split condition block to avoid
+ // executing dead loop iteration.
+ ICmpInst *B_ExitCondition = cast<ICmpInst>(ValueMap[ExitCondition]);
+ Instruction *B_IndVarIncrement = cast<Instruction>(ValueMap[IndVarIncrement]);
+ ICmpInst *B_SplitCondition = cast<ICmpInst>(ValueMap[SD.SplitCondition]);
+
+ moveExitCondition(A_SplitCondBlock, A_ActiveBranch, A_ExitBlock, ExitCondition,
+ cast<ICmpInst>(SD.SplitCondition), IndVar, IndVarIncrement,
+ ALoop);
+
+ moveExitCondition(B_SplitCondBlock, B_ActiveBranch, B_ExitBlock, B_ExitCondition,
+ B_SplitCondition, B_IndVar, B_IndVarIncrement, BLoop);
+
return true;
}
+
+// moveExitCondition - Move exit condition EC into split condition block CondBB.
+void LoopIndexSplit::moveExitCondition(BasicBlock *CondBB, BasicBlock *ActiveBB,
+ BasicBlock *ExitBB, ICmpInst *EC, ICmpInst *SC,
+ PHINode *IV, Instruction *IVAdd, Loop *LP) {
+
+ BasicBlock *ExitingBB = EC->getParent();
+ Instruction *CurrentBR = CondBB->getTerminator();
+
+ // Move exit condition into split condition block.
+ EC->moveBefore(CurrentBR);
+ EC->setOperand(ExitValueNum == 0 ? 1 : 0, IV);
+
+ // Move exiting block's branch into split condition block. Update its branch
+ // destination.
+ BranchInst *ExitingBR = cast<BranchInst>(ExitingBB->getTerminator());
+ ExitingBR->moveBefore(CurrentBR);
+ BasicBlock *OrigDestBB = NULL;
+ if (ExitingBR->getSuccessor(0) == ExitBB) {
+ OrigDestBB = ExitingBR->getSuccessor(1);
+ ExitingBR->setSuccessor(1, ActiveBB);
+ }
+ 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 original destination.
+ new BranchInst(OrigDestBB, ExitingBB);
+
+ // Update PHINodes
+ updatePHINodes(ExitBB, ExitingBB, CondBB, IV, IVAdd, LP);
+
+ // Fix dominator info.
+ // ExitBB is now dominated by CondBB
+ DT->changeImmediateDominator(ExitBB, CondBB);
+ DF->changeImmediateDominator(ExitBB, CondBB, DT);
+
+ // Basicblocks dominated by ActiveBB may have ExitingBB or
+ // a basic block outside the loop in their DF list. If so,
+ // replace it with CondBB.
+ DomTreeNode *Node = DT->getNode(ActiveBB);
+ for (df_iterator<DomTreeNode *> DI = df_begin(Node), DE = df_end(Node);
+ DI != DE; ++DI) {
+ BasicBlock *BB = DI->getBlock();
+ 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 == ExitingBB || !L->contains(DFBB)) {
+ BBDF->second.erase(DFBB);
+ BBDF->second.insert(CondBB);
+ }
+ }
+ }
+}
+
+/// updatePHINodes - CFG has been changed.
+/// Before
+/// - ExitBB's single predecessor was Latch
+/// - Latch's second successor was Header
+/// Now
+/// - 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,
+ Loop *LP) {
+
+ for (BasicBlock::iterator BI = ExitBB->begin(), BE = ExitBB->end();
+ BI != BE; ++BI) {
+ PHINode *PN = dyn_cast<PHINode>(BI);
+ if (!PN)
+ break;
+
+ Value *V = PN->getIncomingValueForBlock(Latch);
+ if (PHINode *PHV = dyn_cast<PHINode>(V)) {
+ // 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 (PHINode *U = dyn_cast<PHINode>(*UI))
+ if (LP->contains(U->getParent())) {
+ NewV = U;
+ break;
+ }
+
+ assert (NewV && "Unable to find new incoming value for exit block PHI");
+ PN->addIncoming(NewV, Header);
+
+ } else if (Instruction *PHI = dyn_cast<Instruction>(V)) {
+ // If this instruction is IVIncrement then IV is new incoming value
+ // from header otherwise this instruction must be incoming value from
+ // header because loop is in LCSSA form.
+ if (PHI == IVIncrement)
+ PN->addIncoming(IV, Header);
+ else
+ PN->addIncoming(V, Header);
+ } else
+ // Otherwise this is an incoming value from header because loop is in
+ // LCSSA form.
+ PN->addIncoming(V, Header);
+
+ // Remove incoming value from Latch.
+ PN->removeIncomingValue(Latch);
+ }
+}
projects / oota-llvm.git / blobdiff