//
// 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.
//
//===----------------------------------------------------------------------===//
//
-// This file implements Loop Index Splitting Pass.
+// This file implements Loop Index Splitting Pass. This pass handles three
+// kinds of loops.
//
+// [1] Loop is eliminated when loop body is executed only once. For example,
+// for (i = 0; i < N; ++i) {
+// if ( i == X) {
+// ...
+// }
+// }
+//
+// [2] Loop's iteration space is shrunk if loop body is executed for certain
+// range only. For example,
+//
+// for (i = 0; i < N; ++i) {
+// if ( i > A && i < B) {
+// ...
+// }
+// }
+// is trnasformed to iterators from A to B, if A > 0 and B < N.
+//
+// [3] Loop is split if the loop body is dominated by an branch. For example,
+//
+// 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;
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "loop-index-split"
#include "llvm/Transforms/Scalar.h"
-#include "llvm/Function.h"
+#include "llvm/IntrinsicInst.h"
#include "llvm/Analysis/LoopPass.h"
-#include "llvm/Analysis/ScalarEvolutionExpander.h"
+#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Cloning.h"
+#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Support/Compiler.h"
+#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/Statistic.h"
using namespace llvm;
-STATISTIC(NumIndexSplit, "Number of loops index split");
+STATISTIC(NumIndexSplit, "Number of loop index split");
+STATISTIC(NumIndexSplitRemoved, "Number of loops eliminated by loop index split");
+STATISTIC(NumRestrictBounds, "Number of loop iteration space restricted");
namespace {
public:
static char ID; // Pass ID, replacement for typeid
- LoopIndexSplit() : LoopPass((intptr_t)&ID) {}
+ LoopIndexSplit() : LoopPass(&ID) {}
// Index split Loop L. Return true if loop is split.
bool runOnLoop(Loop *L, LPPassManager &LPM);
void getAnalysisUsage(AnalysisUsage &AU) const {
- AU.addRequired<ScalarEvolution>();
AU.addPreserved<ScalarEvolution>();
AU.addRequiredID(LCSSAID);
AU.addPreservedID(LCSSAID);
AU.addRequiredID(LoopSimplifyID);
AU.addPreservedID(LoopSimplifyID);
AU.addRequired<DominatorTree>();
+ AU.addRequired<DominanceFrontier>();
AU.addPreserved<DominatorTree>();
AU.addPreserved<DominanceFrontier>();
}
private:
-
- class SplitInfo {
- public:
- SplitInfo() : SplitValue(NULL), SplitCondition(NULL) {}
-
- // Induction variable's range is split at this value.
- Value *SplitValue;
-
- // This compare instruction compares IndVar against SplitValue.
- ICmpInst *SplitCondition;
-
- // Clear split info.
- void clear() {
- SplitValue = NULL;
- SplitCondition = NULL;
- }
-
- };
+ /// processOneIterationLoop -- Eliminate loop if loop body is executed
+ /// only once. For example,
+ /// for (i = 0; i < N; ++i) {
+ /// if ( i == X) {
+ /// ...
+ /// }
+ /// }
+ ///
+ bool processOneIterationLoop();
+
+ // -- Routines used by updateLoopIterationSpace();
+
+ /// updateLoopIterationSpace -- Update loop's iteration space if loop
+ /// body is executed for certain IV range only. For example,
+ ///
+ /// for (i = 0; i < N; ++i) {
+ /// if ( i > A && i < B) {
+ /// ...
+ /// }
+ /// }
+ /// is transformed to iterators from A to B, if A > 0 and B < N.
+ ///
+ bool updateLoopIterationSpace();
+
+ /// restrictLoopBound - Op dominates loop body. Op compares an IV based value
+ /// with a loop invariant value. Update loop's lower and upper bound based on
+ /// the loop invariant value.
+ bool restrictLoopBound(ICmpInst &Op);
+
+ // --- Routines used by splitLoop(). --- /
+
+ bool splitLoop();
+
+ /// 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.
+ void removeBlocks(BasicBlock *DeadBB, Loop *LP, BasicBlock *LiveBB);
- private:
- /// Find condition inside a loop that is suitable candidate for index split.
- void findSplitCondition();
-
- /// Find loop's exit condition.
- void findLoopConditionals();
-
- /// Return induction variable associated with value V.
- void findIndVar(Value *V, Loop *L);
-
- /// processOneIterationLoop - Current loop L contains compare instruction
- /// that compares induction variable, IndVar, agains loop invariant. If
- /// entire (i.e. meaningful) loop body is dominated by this compare
- /// 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);
+ /// moveExitCondition - Move exit condition EC into split condition block.
+ void moveExitCondition(BasicBlock *CondBB, BasicBlock *ActiveBB,
+ BasicBlock *ExitBB, ICmpInst *EC, ICmpInst *SC,
+ PHINode *IV, Instruction *IVAdd, Loop *LP,
+ unsigned);
- /// If loop header includes loop variant instruction operands then
- /// this loop may not be eliminated.
- bool safeHeader(SplitInfo &SD, BasicBlock *BB);
-
- /// If Exit block includes loop variant instructions then this
- /// loop may not be eliminated.
- bool safeExitBlock(SplitInfo &SD, BasicBlock *BB);
-
- /// 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.
- void removeBlocks(BasicBlock *DeadBB, Loop *LP, BasicBlock *LiveBB);
-
- /// Find cost of spliting loop L.
- unsigned findSplitCost(Loop *L, SplitInfo &SD);
- bool splitLoop(SplitInfo &SD);
-
- void initialize() {
- IndVar = NULL;
- IndVarIncrement = NULL;
- ExitCondition = NULL;
- StartValue = NULL;
- ExitValueNum = 0;
- SplitData.clear();
- }
+ /// 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);
+
+ // --- Utility routines --- /
+
+ /// cleanBlock - A block is considered clean if all non terminal
+ /// instructions are either PHINodes or IV based values.
+ bool cleanBlock(BasicBlock *BB);
+
+ /// IVisLT - If Op is comparing IV based value with an loop invariant and
+ /// IV based value is less than the loop invariant then return the loop
+ /// invariant. Otherwise return NULL.
+ Value * IVisLT(ICmpInst &Op);
+
+ /// IVisLE - If Op is comparing IV based value with an loop invariant and
+ /// IV based value is less than or equal to the loop invariant then
+ /// return the loop invariant. Otherwise return NULL.
+ Value * IVisLE(ICmpInst &Op);
+
+ /// IVisGT - If Op is comparing IV based value with an loop invariant and
+ /// IV based value is greater than the loop invariant then return the loop
+ /// invariant. Otherwise return NULL.
+ Value * IVisGT(ICmpInst &Op);
+
+ /// IVisGE - If Op is comparing IV based value with an loop invariant and
+ /// IV based value is greater than or equal to the loop invariant then
+ /// return the loop invariant. Otherwise return NULL.
+ Value * IVisGE(ICmpInst &Op);
private:
- // Current Loop.
+ // Current Loop information.
Loop *L;
LPPassManager *LPM;
LoopInfo *LI;
- ScalarEvolution *SE;
DominatorTree *DT;
DominanceFrontier *DF;
- SmallVector<SplitInfo, 4> SplitData;
- // Induction variable whose range is being split by this transformation.
PHINode *IndVar;
- Instruction *IndVarIncrement;
-
- // Loop exit condition.
ICmpInst *ExitCondition;
-
- // Induction variable's initial value.
- Value *StartValue;
-
- // Induction variable's final loop exit value operand number in exit condition..
- unsigned ExitValueNum;
+ ICmpInst *SplitCondition;
+ Value *IVStartValue;
+ Value *IVExitValue;
+ Instruction *IVIncrement;
+ SmallPtrSet<Value *, 4> IVBasedValues;
};
-
- char LoopIndexSplit::ID = 0;
- RegisterPass<LoopIndexSplit> X ("loop-index-split", "Index Split Loops");
}
-LoopPass *llvm::createLoopIndexSplitPass() {
+char LoopIndexSplit::ID = 0;
+static RegisterPass<LoopIndexSplit>
+X("loop-index-split", "Index Split Loops");
+
+Pass *llvm::createLoopIndexSplitPass() {
return new LoopIndexSplit();
}
// Index split Loop L. Return true if loop is split.
bool LoopIndexSplit::runOnLoop(Loop *IncomingLoop, LPPassManager &LPM_Ref) {
- bool Changed = false;
L = IncomingLoop;
LPM = &LPM_Ref;
if (!L->getSubLoops().empty())
return false;
- SE = &getAnalysis<ScalarEvolution>();
DT = &getAnalysis<DominatorTree>();
LI = &getAnalysis<LoopInfo>();
- DF = getAnalysisToUpdate<DominanceFrontier>();
+ DF = &getAnalysis<DominanceFrontier>();
- initialize();
+ // Initialize loop data.
+ IndVar = L->getCanonicalInductionVariable();
+ if (!IndVar) return false;
- findLoopConditionals();
+ bool P1InLoop = L->contains(IndVar->getIncomingBlock(1));
+ IVStartValue = IndVar->getIncomingValue(!P1InLoop);
+ IVIncrement = dyn_cast<Instruction>(IndVar->getIncomingValue(P1InLoop));
+ if (!IVIncrement) return false;
+
+ IVBasedValues.clear();
+ IVBasedValues.insert(IndVar);
+ IVBasedValues.insert(IVIncrement);
+ for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
+ I != E; ++I)
+ for(BasicBlock::iterator BI = (*I)->begin(), BE = (*I)->end();
+ BI != BE; ++BI) {
+ if (BinaryOperator *BO = dyn_cast<BinaryOperator>(BI))
+ if (BO != IVIncrement
+ && (BO->getOpcode() == Instruction::Add
+ || BO->getOpcode() == Instruction::Sub))
+ if (IVBasedValues.count(BO->getOperand(0))
+ && L->isLoopInvariant(BO->getOperand(1)))
+ IVBasedValues.insert(BO);
+ }
- if (!ExitCondition)
+ // Reject loop if loop exit condition is not suitable.
+ BasicBlock *ExitingBlock = L->getExitingBlock();
+ if (!ExitingBlock)
return false;
-
- findSplitCondition();
-
- if (SplitData.empty())
+ BranchInst *EBR = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
+ if (!EBR) return false;
+ ExitCondition = dyn_cast<ICmpInst>(EBR->getCondition());
+ if (!ExitCondition) return false;
+ if (ExitingBlock != L->getLoopLatch()) return false;
+ IVExitValue = ExitCondition->getOperand(1);
+ if (!L->isLoopInvariant(IVExitValue))
+ IVExitValue = ExitCondition->getOperand(0);
+ if (!L->isLoopInvariant(IVExitValue))
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; ++SI) {
- SplitInfo &SD = *SI;
- if (SD.SplitCondition->getPredicate() == ICmpInst::ICMP_EQ) {
- Changed = processOneIterationLoop(SD);
- if (Changed) {
- ++NumIndexSplit;
- // If is loop is eliminated then nothing else to do here.
- return Changed;
- }
- }
- }
+ // 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 (ConstantInt *SV = dyn_cast<ConstantInt>(IVStartValue))
+ if (ConstantInt *EV = dyn_cast<ConstantInt>(IVExitValue))
+ if (SV->getSExtValue() > EV->getSExtValue())
+ return false;
- 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;
+ if (processOneIterationLoop())
+ return true;
- // ICM_EQs are already handled above.
- if (SD.SplitCondition->getPredicate() == ICmpInst::ICMP_EQ)
- continue;
-
- unsigned Cost = findSplitCost(L, SD);
- if (Cost < MaxCost)
- MostProfitableSDIndex = Index;
- }
+ if (updateLoopIterationSpace())
+ return true;
- // Split most profitiable condition.
- Changed = splitLoop(SplitData[MostProfitableSDIndex]);
+ if (splitLoop())
+ return true;
- if (Changed)
- ++NumIndexSplit;
-
- return Changed;
+ return false;
}
-/// Return true if V is a induction variable or induction variable's
-/// increment for loop L.
-void LoopIndexSplit::findIndVar(Value *V, Loop *L) {
-
- Instruction *I = dyn_cast<Instruction>(V);
- if (!I)
- return;
-
- // Check if I is a phi node from loop header or not.
- if (PHINode *PN = dyn_cast<PHINode>(V)) {
- if (PN->getParent() == L->getHeader()) {
- IndVar = PN;
- return;
- }
- }
-
- // Check if I is a add instruction whose one operand is
- // phi node from loop header and second operand is constant.
- if (I->getOpcode() != Instruction::Add)
- return;
-
- 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;
- }
- }
-
- return;
+// --- Helper routines ---
+// isUsedOutsideLoop - Returns true iff V is used outside the loop L.
+static bool isUsedOutsideLoop(Value *V, Loop *L) {
+ for(Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
+ if (!L->contains(cast<Instruction>(*UI)->getParent()))
+ return true;
+ return false;
}
-// Find loop's exit condition and associated induction variable.
-void LoopIndexSplit::findLoopConditionals() {
-
- BasicBlock *ExitBlock = NULL;
-
- for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
- I != E; ++I) {
- BasicBlock *BB = *I;
- if (!L->isLoopExit(BB))
- continue;
- if (ExitBlock)
- return;
- ExitBlock = BB;
- }
-
- if (!ExitBlock)
- return;
-
- // If exit block's terminator is conditional branch inst then we have found
- // exit condition.
- BranchInst *BR = dyn_cast<BranchInst>(ExitBlock->getTerminator());
- if (!BR || BR->isUnconditional())
- return;
-
- ICmpInst *CI = dyn_cast<ICmpInst>(BR->getCondition());
- if (!CI)
- return;
-
- ExitCondition = CI;
-
- // Exit condition's one operand is loop invariant exit value and second
- // operand is SCEVAddRecExpr based on induction variable.
- 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)) {
- ExitValueNum = 0;
- findIndVar(V1, L);
- }
- else if (SH1->isLoopInvariant(L) && isa<SCEVAddRecExpr>(SH0)) {
- ExitValueNum = 1;
- findIndVar(V0, L);
- }
-
- if (!IndVar)
- ExitCondition = NULL;
- else if (IndVar) {
- BasicBlock *Preheader = L->getLoopPreheader();
- StartValue = IndVar->getIncomingValueForBlock(Preheader);
- }
+// Return V+1
+static Value *getPlusOne(Value *V, bool Sign, Instruction *InsertPt) {
+ ConstantInt *One = ConstantInt::get(V->getType(), 1, Sign);
+ return BinaryOperator::CreateAdd(V, One, "lsp", InsertPt);
}
-/// Find condition inside a loop that is suitable candidate for index split.
-void LoopIndexSplit::findSplitCondition() {
-
- SplitInfo SD;
- // Check all basic block's terminators.
-
- for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
- I != E; ++I) {
- BasicBlock *BB = *I;
-
- // If this basic block does not terminate in a conditional branch
- // then terminator is not a suitable split condition.
- BranchInst *BR = dyn_cast<BranchInst>(BB->getTerminator());
- if (!BR)
- continue;
-
- if (BR->isUnconditional())
- continue;
+// Return V-1
+static Value *getMinusOne(Value *V, bool Sign, Instruction *InsertPt) {
+ ConstantInt *One = ConstantInt::get(V->getType(), 1, Sign);
+ return BinaryOperator::CreateSub(V, One, "lsp", InsertPt);
+}
- ICmpInst *CI = dyn_cast<ICmpInst>(BR->getCondition());
- if (!CI || CI == ExitCondition)
- return;
-
- // 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);
- }
- }
- 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);
- }
- }
- }
+// Return min(V1, V1)
+static Value *getMin(Value *V1, Value *V2, bool Sign, Instruction *InsertPt) {
+
+ Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
+ V1, V2, "lsp", InsertPt);
+ return SelectInst::Create(C, V1, V2, "lsp", InsertPt);
}
-/// processOneIterationLoop - Current loop L contains compare instruction
-/// that compares induction variable, IndVar, against loop invariant. If
-/// entire (i.e. meaningful) loop body is dominated by this compare
-/// instruction then loop body is executed only once. In such case eliminate
-/// loop structure surrounding this loop body. For example,
-/// for (int i = start; i < end; ++i) {
-/// if ( i == somevalue) {
-/// loop_body
-/// }
-/// }
-/// can be transformed into
-/// if (somevalue >= start && somevalue < end) {
-/// i = somevalue;
-/// loop_body
-/// }
-bool LoopIndexSplit::processOneIterationLoop(SplitInfo &SD) {
+// Return max(V1, V2)
+static Value *getMax(Value *V1, Value *V2, bool Sign, Instruction *InsertPt) {
+
+ Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
+ V1, V2, "lsp", InsertPt);
+ return SelectInst::Create(C, V2, V1, "lsp", InsertPt);
+}
+/// processOneIterationLoop -- Eliminate loop if loop body is executed
+/// only once. For example,
+/// for (i = 0; i < N; ++i) {
+/// if ( i == X) {
+/// ...
+/// }
+/// }
+///
+bool LoopIndexSplit::processOneIterationLoop() {
+ SplitCondition = NULL;
+ BasicBlock *Latch = L->getLoopLatch();
BasicBlock *Header = L->getHeader();
-
- // First of all, 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)
+ BranchInst *BR = dyn_cast<BranchInst>(Header->getTerminator());
+ if (!BR) return false;
+ if (!isa<BranchInst>(Latch->getTerminator())) return false;
+ if (BR->isUnconditional()) return false;
+ SplitCondition = dyn_cast<ICmpInst>(BR->getCondition());
+ if (!SplitCondition) return false;
+ if (SplitCondition == ExitCondition) return false;
+ if (SplitCondition->getPredicate() != ICmpInst::ICMP_EQ) return false;
+ if (BR->getOperand(1) != Latch) return false;
+ if (!IVBasedValues.count(SplitCondition->getOperand(0))
+ && !IVBasedValues.count(SplitCondition->getOperand(1)))
return false;
-
- // If loop header includes loop variant instruction operands then
- // this loop may not be eliminated.
- if (!safeHeader(SD, Header))
+
+ // If IV is used outside the loop then this loop traversal is required.
+ // FIXME: Calculate and use last IV value.
+ if (isUsedOutsideLoop(IVIncrement, L))
return false;
- // If Exit block includes loop variant instructions then this
- // loop may not be eliminated.
- if (!safeExitBlock(SD, ExitCondition->getParent()))
+ // If BR operands are not IV or not loop invariants then skip this loop.
+ Value *OPV = SplitCondition->getOperand(0);
+ Value *SplitValue = SplitCondition->getOperand(1);
+ if (!L->isLoopInvariant(SplitValue)) {
+ Value *T = SplitValue;
+ SplitValue = OPV;
+ OPV = T;
+ }
+ if (!L->isLoopInvariant(SplitValue))
+ return false;
+ Instruction *OPI = dyn_cast<Instruction>(OPV);
+ if (!OPI)
return false;
+ if (OPI->getParent() != Header || isUsedOutsideLoop(OPI, L))
+ return false;
+ Value *StartValue = IVStartValue;
+ Value *ExitValue = IVExitValue;;
+
+ if (OPV != IndVar) {
+ // If BR operand is IV based then use this operand to calculate
+ // effective conditions for loop body.
+ BinaryOperator *BOPV = dyn_cast<BinaryOperator>(OPV);
+ if (!BOPV)
+ return false;
+ if (BOPV->getOpcode() != Instruction::Add)
+ return false;
+ StartValue = BinaryOperator::CreateAdd(OPV, StartValue, "" , BR);
+ ExitValue = BinaryOperator::CreateAdd(OPV, ExitValue, "" , BR);
+ }
- // Update CFG.
+ if (!cleanBlock(Header))
+ return false;
- // As a first step to break this loop, remove Latch to Header edge.
- BasicBlock *Latch = L->getLoopLatch();
- BasicBlock *LatchSucc = NULL;
- BranchInst *BR = dyn_cast<BranchInst>(Latch->getTerminator());
- if (!BR)
+ if (!cleanBlock(Latch))
return false;
- Header->removePredecessor(Latch);
- for (succ_iterator SI = succ_begin(Latch), E = succ_end(Latch);
- SI != E; ++SI) {
- if (Header != *SI)
- LatchSucc = *SI;
+
+ // If the merge point for BR is not loop latch then skip this loop.
+ if (BR->getSuccessor(0) != Latch) {
+ DominanceFrontier::iterator DF0 = DF->find(BR->getSuccessor(0));
+ assert (DF0 != DF->end() && "Unable to find dominance frontier");
+ if (!DF0->second.count(Latch))
+ return false;
}
- BR->setUnconditionalDest(LatchSucc);
-
- Instruction *Terminator = Header->getTerminator();
- Value *ExitValue = ExitCondition->getOperand(ExitValueNum);
+
+ if (BR->getSuccessor(1) != Latch) {
+ DominanceFrontier::iterator DF1 = DF->find(BR->getSuccessor(1));
+ assert (DF1 != DF->end() && "Unable to find dominance frontier");
+ if (!DF1->second.count(Latch))
+ return false;
+ }
+
+ // Now, Current loop L contains compare instruction
+ // that compares induction variable, IndVar, against loop invariant. And
+ // entire (i.e. meaningful) loop body is dominated by this compare
+ // instruction. In such case eliminate
+ // loop structure surrounding this loop body. For example,
+ // for (int i = start; i < end; ++i) {
+ // if ( i == somevalue) {
+ // loop_body
+ // }
+ // }
+ // can be transformed into
+ // if (somevalue >= start && somevalue < end) {
+ // i = somevalue;
+ // loop_body
+ // }
+
+ // Replace index variable with split value in loop body. Loop body is executed
+ // only when index variable is equal to split value.
+ IndVar->replaceAllUsesWith(SplitValue);
// Replace split condition in header.
// Transform
// 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 ?
+ Instruction *C1 = new ICmpInst(ExitCondition->isSignedPredicate() ?
ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE,
- SD.SplitValue, StartValue, "lisplit",
- Terminator);
- Instruction *C2 = new ICmpInst(SignedPredicate ?
- ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
- SD.SplitValue, ExitValue, "lisplit",
- Terminator);
- Instruction *NSplitCond = BinaryOperator::createAnd(C1, C2, "lisplit",
- Terminator);
- SD.SplitCondition->replaceAllUsesWith(NSplitCond);
- SD.SplitCondition->eraseFromParent();
-
- // Now, clear latch block. Remove instructions that are responsible
- // to increment induction variable.
- Instruction *LTerminator = Latch->getTerminator();
- for (BasicBlock::iterator LB = Latch->begin(), LE = Latch->end();
- LB != LE; ) {
- Instruction *I = LB;
- ++LB;
- if (isa<PHINode>(I) || I == LTerminator)
- continue;
+ SplitValue, StartValue, "lisplit", BR);
- if (I == IndVarIncrement)
- I->replaceAllUsesWith(ExitValue);
- else
- I->replaceAllUsesWith(UndefValue::get(I->getType()));
- I->eraseFromParent();
+ CmpInst::Predicate C2P = ExitCondition->getPredicate();
+ BranchInst *LatchBR = cast<BranchInst>(Latch->getTerminator());
+ if (LatchBR->getOperand(0) != Header)
+ C2P = CmpInst::getInversePredicate(C2P);
+ Instruction *C2 = new ICmpInst(C2P, SplitValue, ExitValue, "lisplit", BR);
+ Instruction *NSplitCond = BinaryOperator::CreateAnd(C1, C2, "lisplit", BR);
+
+ SplitCondition->replaceAllUsesWith(NSplitCond);
+ SplitCondition->eraseFromParent();
+
+ // Remove Latch to Header edge.
+ BasicBlock *LatchSucc = NULL;
+ Header->removePredecessor(Latch);
+ for (succ_iterator SI = succ_begin(Latch), E = succ_end(Latch);
+ SI != E; ++SI) {
+ if (Header != *SI)
+ LatchSucc = *SI;
}
+ // Clean up latch block.
+ Value *LatchBRCond = LatchBR->getCondition();
+ LatchBR->setUnconditionalDest(LatchSucc);
+ RecursivelyDeleteTriviallyDeadInstructions(LatchBRCond);
+
LPM->deleteLoopFromQueue(L);
// Update Dominator Info.
if (LatchDF != DF->end())
DF->removeFromFrontier(LatchDF, Header);
}
+
+ ++NumIndexSplitRemoved;
return true;
}
-// If loop header includes loop variant instruction operands then
-// this loop can not be eliminated. This is used by processOneIterationLoop().
-bool LoopIndexSplit::safeHeader(SplitInfo &SD, BasicBlock *Header) {
-
- 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;
-
- // Induction variable is OK.
- if (I == IndVar)
- continue;
+/// restrictLoopBound - Op dominates loop body. Op compares an IV based value
+/// with a loop invariant value. Update loop's lower and upper bound based on
+/// the loop invariant value.
+bool LoopIndexSplit::restrictLoopBound(ICmpInst &Op) {
+ bool Sign = Op.isSignedPredicate();
+ Instruction *PHTerm = L->getLoopPreheader()->getTerminator();
+
+ if (IVisGT(*ExitCondition) || IVisGE(*ExitCondition)) {
+ BranchInst *EBR =
+ cast<BranchInst>(ExitCondition->getParent()->getTerminator());
+ ExitCondition->setPredicate(ExitCondition->getInversePredicate());
+ BasicBlock *T = EBR->getSuccessor(0);
+ EBR->setSuccessor(0, EBR->getSuccessor(1));
+ EBR->setSuccessor(1, T);
+ }
- // Induction variable increment is OK.
- if (I == IndVarIncrement)
- continue;
+ // New upper and lower bounds.
+ Value *NLB = NULL;
+ Value *NUB = NULL;
+ if (Value *V = IVisLT(Op)) {
+ // Restrict upper bound.
+ if (IVisLE(*ExitCondition))
+ V = getMinusOne(V, Sign, PHTerm);
+ NUB = getMin(V, IVExitValue, Sign, PHTerm);
+ } else if (Value *V = IVisLE(Op)) {
+ // Restrict upper bound.
+ if (IVisLT(*ExitCondition))
+ V = getPlusOne(V, Sign, PHTerm);
+ NUB = getMin(V, IVExitValue, Sign, PHTerm);
+ } else if (Value *V = IVisGT(Op)) {
+ // Restrict lower bound.
+ V = getPlusOne(V, Sign, PHTerm);
+ NLB = getMax(V, IVStartValue, Sign, PHTerm);
+ } else if (Value *V = IVisGE(Op))
+ // Restrict lower bound.
+ NLB = getMax(V, IVStartValue, Sign, PHTerm);
+
+ if (!NLB && !NUB)
+ return false;
- // Terminator is also harmless.
- if (I == Terminator)
- continue;
+ if (NLB) {
+ unsigned i = IndVar->getBasicBlockIndex(L->getLoopPreheader());
+ IndVar->setIncomingValue(i, NLB);
+ }
- // Otherwise we have a instruction that may not be safe.
- return false;
+ if (NUB) {
+ unsigned i = (ExitCondition->getOperand(0) != IVExitValue);
+ ExitCondition->setOperand(i, NUB);
}
-
return true;
}
-// If Exit block includes loop variant instructions then this
-// loop may not be eliminated. This is used by processOneIterationLoop().
-bool LoopIndexSplit::safeExitBlock(SplitInfo &SD, BasicBlock *ExitBlock) {
-
- for (BasicBlock::iterator BI = ExitBlock->begin(), BE = ExitBlock->end();
- BI != BE; ++BI) {
- Instruction *I = BI;
-
- // PHI Nodes are OK.
- if (isa<PHINode>(I))
- continue;
-
- // Induction variable increment is OK.
- if (IndVarIncrement && IndVarIncrement == I)
- continue;
-
- // Check if I is induction variable increment instruction.
- if (!IndVarIncrement && I->getOpcode() == Instruction::Add) {
-
- Value *Op0 = I->getOperand(0);
- Value *Op1 = I->getOperand(1);
- PHINode *PN = NULL;
- ConstantInt *CI = NULL;
-
- if ((PN = dyn_cast<PHINode>(Op0))) {
- if ((CI = dyn_cast<ConstantInt>(Op1)))
- IndVarIncrement = I;
- } else
- if ((PN = dyn_cast<PHINode>(Op1))) {
- if ((CI = dyn_cast<ConstantInt>(Op0)))
- IndVarIncrement = I;
- }
-
- 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,
- // which is checked below.
- else if (ICmpInst *EC = dyn_cast<ICmpInst>(I)) {
- if (EC == ExitCondition)
- continue;
- }
-
- if (I == ExitBlock->getTerminator())
- continue;
-
- // Otherwise we have instruction that may not be safe.
+/// updateLoopIterationSpace -- Update loop's iteration space if loop
+/// body is executed for certain IV range only. For example,
+///
+/// for (i = 0; i < N; ++i) {
+/// if ( i > A && i < B) {
+/// ...
+/// }
+/// }
+/// is transformed to iterators from A to B, if A > 0 and B < N.
+///
+bool LoopIndexSplit::updateLoopIterationSpace() {
+ SplitCondition = NULL;
+ if (ExitCondition->getPredicate() == ICmpInst::ICMP_NE
+ || ExitCondition->getPredicate() == ICmpInst::ICMP_EQ)
return false;
+ BasicBlock *Latch = L->getLoopLatch();
+ BasicBlock *Header = L->getHeader();
+ BranchInst *BR = dyn_cast<BranchInst>(Header->getTerminator());
+ if (!BR) return false;
+ if (!isa<BranchInst>(Latch->getTerminator())) return false;
+ if (BR->isUnconditional()) return false;
+ BinaryOperator *AND = dyn_cast<BinaryOperator>(BR->getCondition());
+ if (!AND) return false;
+ if (AND->getOpcode() != Instruction::And) return false;
+ ICmpInst *Op0 = dyn_cast<ICmpInst>(AND->getOperand(0));
+ ICmpInst *Op1 = dyn_cast<ICmpInst>(AND->getOperand(1));
+ if (!Op0 || !Op1)
+ return false;
+ IVBasedValues.insert(AND);
+ IVBasedValues.insert(Op0);
+ IVBasedValues.insert(Op1);
+ if (!cleanBlock(Header)) return false;
+ BasicBlock *ExitingBlock = ExitCondition->getParent();
+ if (!cleanBlock(ExitingBlock)) return false;
+
+ // If the merge point for BR is not loop latch then skip this loop.
+ if (BR->getSuccessor(0) != Latch) {
+ DominanceFrontier::iterator DF0 = DF->find(BR->getSuccessor(0));
+ assert (DF0 != DF->end() && "Unable to find dominance frontier");
+ if (!DF0->second.count(Latch))
+ return false;
+ }
+
+ if (BR->getSuccessor(1) != Latch) {
+ DominanceFrontier::iterator DF1 = DF->find(BR->getSuccessor(1));
+ assert (DF1 != DF->end() && "Unable to find dominance frontier");
+ if (!DF1->second.count(Latch))
+ return false;
+ }
+
+ // Verify that loop exiting block has only two predecessor, where one pred
+ // 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 (Header == BB)
+ continue;
+ if (ExitingBBPred)
+ return false;
+ else
+ ExitingBBPred = BB;
}
- // We could not find any reason to consider ExitBlock unsafe.
- return true;
-}
+ if (!restrictLoopBound(*Op0))
+ return false;
-/// 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) {
+ if (!restrictLoopBound(*Op1))
+ return false;
- unsigned Cost = 0;
- BasicBlock *SDBlock = SD.SplitCondition->getParent();
+ // Update CFG.
+ if (BR->getSuccessor(0) == ExitingBlock)
+ BR->setUnconditionalDest(BR->getSuccessor(1));
+ else
+ BR->setUnconditionalDest(BR->getSuccessor(0));
+
+ AND->eraseFromParent();
+ if (Op0->use_empty())
+ Op0->eraseFromParent();
+ if (Op1->use_empty())
+ Op1->eraseFromParent();
+
+ // Update domiantor info. Now, ExitingBlock has only one predecessor,
+ // ExitingBBPred, and it is ExitingBlock's immediate domiantor.
+ DT->changeImmediateDominator(ExitingBlock, ExitingBBPred);
+
+ BasicBlock *ExitBlock = ExitingBlock->getTerminator()->getSuccessor(1);
+ if (L->contains(ExitBlock))
+ ExitBlock = ExitingBlock->getTerminator()->getSuccessor(0);
+
+ // If ExitingBlock is a member of the loop basic blocks' DF list then
+ // replace ExitingBlock with header and exit block in the DF list
+ DominanceFrontier::iterator ExitingBlockDF = DF->find(ExitingBlock);
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);
+ for (DominanceFrontier::DomSetType::iterator
+ EBI = ExitingBlockDF->second.begin(),
+ EBE = ExitingBlockDF->second.end(); EBI != EBE; ++EBI)
+ BBDF->second.insert(*EBI);
+ }
+ }
}
-
- return Cost;
+ NumRestrictBounds++;
+ return true;
}
/// removeBlocks - Remove basic block DeadBB and all blocks dominated by DeadBB.
void LoopIndexSplit::removeBlocks(BasicBlock *DeadBB, Loop *LP,
BasicBlock *LiveBB) {
- SmallVector<std::pair<BasicBlock *, succ_iterator>, 8> WorkList;
- WorkList.push_back(std::make_pair(DeadBB, succ_begin(DeadBB)));
- while (!WorkList.empty()) {
- BasicBlock *BB = WorkList.back(). first;
- succ_iterator SIter = WorkList.back().second;
-
- // If all successor's are processed then remove this block.
- if (SIter == succ_end(BB)) {
- WorkList.pop_back();
- for(BasicBlock::iterator BBI = BB->begin(), BBE = BB->end();
- BBI != BBE; ++BBI) {
- Instruction *I = BBI;
- I->replaceAllUsesWith(UndefValue::get(I->getType()));
- I->eraseFromParent();
+ // First update DeadBB's dominance frontier.
+ SmallVector<BasicBlock *, 8> FrontierBBs;
+ DominanceFrontier::iterator DeadBBDF = DF->find(DeadBB);
+ if (DeadBBDF != DF->end()) {
+ SmallVector<BasicBlock *, 8> PredBlocks;
+
+ DominanceFrontier::DomSetType DeadBBSet = DeadBBDF->second;
+ for (DominanceFrontier::DomSetType::iterator DeadBBSetI = DeadBBSet.begin(),
+ DeadBBSetE = DeadBBSet.end(); DeadBBSetI != DeadBBSetE; ++DeadBBSetI)
+ {
+ BasicBlock *FrontierBB = *DeadBBSetI;
+ FrontierBBs.push_back(FrontierBB);
+
+ // Rremove any PHI incoming edge from blocks dominated by DeadBB.
+ PredBlocks.clear();
+ for(pred_iterator PI = pred_begin(FrontierBB), PE = pred_end(FrontierBB);
+ PI != PE; ++PI) {
+ BasicBlock *P = *PI;
+ if (P == DeadBB || DT->dominates(DeadBB, P))
+ PredBlocks.push_back(P);
}
- LPM->deleteSimpleAnalysisValue(BB, LP);
- DT->eraseNode(BB);
- DF->removeBlock(BB);
- LI->removeBlock(BB);
- BB->eraseFromParent();
- } else {
- BasicBlock *SuccBB = *SIter;
- ++WorkList.back().second;
-
- if (DT->dominates(BB, SuccBB)) {
- WorkList.push_back(std::make_pair(SuccBB, succ_begin(SuccBB)));
- continue;
- } else {
- // If SuccBB is not dominated by BB then it is not removed, however remove
- // any PHI incoming edge from BB.
- for(BasicBlock::iterator SBI = SuccBB->begin(), SBE = SuccBB->end();
- SBI != SBE; ++SBI) {
- if (PHINode *PN = dyn_cast<PHINode>(SBI))
- PN->removeIncomingValue(BB);
- else
- break;
+
+ for(BasicBlock::iterator FBI = FrontierBB->begin(), FBE = FrontierBB->end();
+ FBI != FBE; ++FBI) {
+ if (PHINode *PN = dyn_cast<PHINode>(FBI)) {
+ for(SmallVector<BasicBlock *, 8>::iterator PI = PredBlocks.begin(),
+ PE = PredBlocks.end(); PI != PE; ++PI) {
+ BasicBlock *P = *PI;
+ PN->removeIncomingValue(P);
+ }
}
+ else
+ break;
+ }
+ }
+ }
+
+ // Now remove DeadBB and all nodes dominated by DeadBB in df order.
+ SmallVector<BasicBlock *, 32> WorkList;
+ DomTreeNode *DN = DT->getNode(DeadBB);
+ for (df_iterator<DomTreeNode*> DI = df_begin(DN),
+ E = df_end(DN); DI != E; ++DI) {
+ BasicBlock *BB = DI->getBlock();
+ WorkList.push_back(BB);
+ BB->replaceAllUsesWith(UndefValue::get(Type::LabelTy));
+ }
+
+ while (!WorkList.empty()) {
+ BasicBlock *BB = WorkList.back(); WorkList.pop_back();
+ LPM->deleteSimpleAnalysisValue(BB, LP);
+ for(BasicBlock::iterator BBI = BB->begin(), BBE = BB->end();
+ BBI != BBE; ) {
+ Instruction *I = BBI;
+ ++BBI;
+ I->replaceAllUsesWith(UndefValue::get(I->getType()));
+ LPM->deleteSimpleAnalysisValue(I, LP);
+ I->eraseFromParent();
+ }
+ DT->eraseNode(BB);
+ DF->removeBlock(BB);
+ LI->removeBlock(BB);
+ BB->eraseFromParent();
+ }
- DT->changeImmediateDominator(SuccBB, LiveBB);
-
- // If BB is not dominating SuccBB then SuccBB is in BB's dominance
- // frontiner.
- DominanceFrontier::iterator BBDF = DF->find(BB);
- DF->removeFromFrontier(BBDF, SuccBB);
-
- // LiveBB is now dominating SuccBB. Which means SuccBB's dominance
- // frontier is member of LiveBB's dominance frontier. However, SuccBB
- // itself is not member of LiveBB's dominance frontier.
- DominanceFrontier::iterator LiveDF = DF->find(LiveBB);
- DominanceFrontier::iterator SuccDF = DF->find(SuccBB);
- DominanceFrontier::DomSetType SuccBBSet = SuccDF->second;
- for (DominanceFrontier::DomSetType::iterator SuccBBSetI = SuccBBSet.begin(),
- SuccBBSetE = SuccBBSet.end(); SuccBBSetI != SuccBBSetE; ++SuccBBSetI) {
- BasicBlock *DFMember = *SuccBBSetI;
- // Insert only if LiveBB dominates DFMember.
- if (!DT->dominates(LiveBB, DFMember))
- LiveDF->second.insert(DFMember);
+ // Update Frontier BBs' dominator info.
+ while (!FrontierBBs.empty()) {
+ BasicBlock *FBB = FrontierBBs.back(); FrontierBBs.pop_back();
+ BasicBlock *NewDominator = FBB->getSinglePredecessor();
+ if (!NewDominator) {
+ pred_iterator PI = pred_begin(FBB), PE = pred_end(FBB);
+ NewDominator = *PI;
+ ++PI;
+ if (NewDominator != LiveBB) {
+ for(; PI != PE; ++PI) {
+ BasicBlock *P = *PI;
+ if (P == LiveBB) {
+ NewDominator = LiveBB;
+ break;
+ }
+ NewDominator = DT->findNearestCommonDominator(NewDominator, P);
}
+ }
+ }
+ assert (NewDominator && "Unable to fix dominator info.");
+ DT->changeImmediateDominator(FBB, NewDominator);
+ DF->changeImmediateDominator(FBB, NewDominator, DT);
+ }
- DF->removeFromFrontier(LiveDF, SuccBB);
+}
+
+// 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,
+ unsigned ExitValueNum) {
+
+ 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.
+ BranchInst::Create(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);
}
}
}
}
-bool LoopIndexSplit::splitLoop(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 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; ) {
+ PHINode *PN = dyn_cast<PHINode>(BI);
+ ++BI;
+ if (!PN)
+ break;
- BasicBlock *Preheader = L->getLoopPreheader();
- BasicBlock *SplitBlock = SD.SplitCondition->getParent();
- BasicBlock *Latch = L->getLoopLatch();
+ 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;
+ }
+
+ // 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
+ // 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);
+ }
+}
+
+bool LoopIndexSplit::splitLoop() {
+ SplitCondition = NULL;
+ if (ExitCondition->getPredicate() == ICmpInst::ICMP_NE
+ || ExitCondition->getPredicate() == ICmpInst::ICMP_EQ)
+ return false;
BasicBlock *Header = L->getHeader();
- BranchInst *SplitTerminator = cast<BranchInst>(SplitBlock->getTerminator());
-
- // FIXME - 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().
- if (Header == SplitBlock
- && (Latch == SplitTerminator->getSuccessor(0)
- || Latch == SplitTerminator->getSuccessor(1)))
+ BasicBlock *Latch = L->getLoopLatch();
+ BranchInst *SBR = NULL; // Split Condition Branch
+ BranchInst *EBR = cast<BranchInst>(ExitCondition->getParent()->getTerminator());
+ // If Exiting block includes loop variant instructions then this
+ // loop may not be split safely.
+ BasicBlock *ExitingBlock = ExitCondition->getParent();
+ if (!cleanBlock(ExitingBlock)) return false;
+
+ for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
+ I != E; ++I) {
+ BranchInst *BR = dyn_cast<BranchInst>((*I)->getTerminator());
+ if (!BR || BR->isUnconditional()) continue;
+ ICmpInst *CI = dyn_cast<ICmpInst>(BR->getCondition());
+ if (!CI || CI == ExitCondition
+ || CI->getPredicate() == ICmpInst::ICMP_NE
+ || CI->getPredicate() == ICmpInst::ICMP_EQ)
+ continue;
+
+ // 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().
+ if (Header == (*I)
+ && (Latch == BR->getSuccessor(0) || Latch == BR->getSuccessor(1)))
+ continue;
+
+ // If the block does not dominate the latch then this is not a diamond.
+ // Such loop may not benefit from index split.
+ if (!DT->dominates((*I), Latch))
+ continue;
+
+ // If split condition branches heads do not have single predecessor,
+ // SplitCondBlock, then is not possible to remove inactive branch.
+ if (!BR->getSuccessor(0)->getSinglePredecessor()
+ || !BR->getSuccessor(1)->getSinglePredecessor())
+ return false;
+
+ // If the merge point for BR is not loop latch then skip this condition.
+ if (BR->getSuccessor(0) != Latch) {
+ DominanceFrontier::iterator DF0 = DF->find(BR->getSuccessor(0));
+ assert (DF0 != DF->end() && "Unable to find dominance frontier");
+ if (!DF0->second.count(Latch))
+ continue;
+ }
+
+ if (BR->getSuccessor(1) != Latch) {
+ DominanceFrontier::iterator DF1 = DF->find(BR->getSuccessor(1));
+ assert (DF1 != DF->end() && "Unable to find dominance frontier");
+ if (!DF1->second.count(Latch))
+ continue;
+ }
+ SplitCondition = CI;
+ SBR = BR;
+ break;
+ }
+
+ if (!SplitCondition)
+ return false;
+
+ // If the predicate sign does not match then skip.
+ if (ExitCondition->isSignedPredicate() != SplitCondition->isSignedPredicate())
return false;
- // True loop is original loop. False loop is cloned loop.
-
- bool SignedPredicate = ExitCondition->isSignedPredicate();
- //[*] Calculate True loop's new Exit Value in loop preheader.
- // TLExitValue = min(SplitValue, ExitValue)
- //[*] Calculate False loop's new Start Value in loop preheader.
- // FLStartValue = min(SplitValue, TrueLoop.StartValue)
- Value *TLExitValue = NULL;
- Value *FLStartValue = NULL;
- if (isa<ConstantInt>(SD.SplitValue)) {
- TLExitValue = SD.SplitValue;
- FLStartValue = SD.SplitValue;
+ unsigned EVOpNum = (ExitCondition->getOperand(1) == IVExitValue);
+ unsigned SVOpNum = IVBasedValues.count(SplitCondition->getOperand(0));
+ Value *SplitValue = SplitCondition->getOperand(SVOpNum);
+ if (!L->isLoopInvariant(SplitValue))
+ return false;
+ if (!IVBasedValues.count(SplitCondition->getOperand(!SVOpNum)))
+ return false;
+
+ // Normalize loop conditions so that it is easier to calculate new loop
+ // bounds.
+ if (IVisGT(*ExitCondition) || IVisGE(*ExitCondition)) {
+ ExitCondition->setPredicate(ExitCondition->getInversePredicate());
+ BasicBlock *T = EBR->getSuccessor(0);
+ EBR->setSuccessor(0, EBR->getSuccessor(1));
+ EBR->setSuccessor(1, T);
}
- else {
- Value *C1 = new ICmpInst(SignedPredicate ?
- ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
- SD.SplitValue,
- ExitCondition->getOperand(ExitValueNum),
- "lsplit.ev",
- Preheader->getTerminator());
- TLExitValue = new SelectInst(C1, SD.SplitValue,
- ExitCondition->getOperand(ExitValueNum),
- "lsplit.ev", Preheader->getTerminator());
-
- Value *C2 = new ICmpInst(SignedPredicate ?
- ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
- SD.SplitValue, StartValue, "lsplit.sv",
- Preheader->getTerminator());
- FLStartValue = new SelectInst(C2, SD.SplitValue, StartValue,
- "lsplit.sv", Preheader->getTerminator());
+
+ if (IVisGT(*SplitCondition) || IVisGE(*SplitCondition)) {
+ SplitCondition->setPredicate(SplitCondition->getInversePredicate());
+ BasicBlock *T = SBR->getSuccessor(0);
+ SBR->setSuccessor(0, SBR->getSuccessor(1));
+ SBR->setSuccessor(1, T);
+ }
+
+ //[*] Calculate new loop bounds.
+ Value *AEV = SplitValue;
+ Value *BSV = SplitValue;
+ bool Sign = SplitCondition->isSignedPredicate();
+ Instruction *PHTerm = L->getLoopPreheader()->getTerminator();
+
+ if (IVisLT(*ExitCondition)) {
+ if (IVisLT(*SplitCondition)) {
+ /* Do nothing */
+ }
+ else if (IVisLE(*SplitCondition)) {
+ AEV = getPlusOne(SplitValue, Sign, PHTerm);
+ BSV = getPlusOne(SplitValue, Sign, PHTerm);
+ } else {
+ assert (0 && "Unexpected split condition!");
+ }
}
+ else if (IVisLE(*ExitCondition)) {
+ if (IVisLT(*SplitCondition)) {
+ AEV = getMinusOne(SplitValue, Sign, PHTerm);
+ }
+ else if (IVisLE(*SplitCondition)) {
+ BSV = getPlusOne(SplitValue, Sign, PHTerm);
+ } else {
+ assert (0 && "Unexpected split condition!");
+ }
+ } else {
+ assert (0 && "Unexpected exit condition!");
+ }
+ AEV = getMin(AEV, IVExitValue, Sign, PHTerm);
+ BSV = getMax(BSV, IVStartValue, Sign, PHTerm);
- //[*] Clone loop. Avoid true destination of split condition and
- // the blocks dominated by true destination.
+ // [*] Clone Loop
DenseMap<const Value *, Value *> ValueMap;
- Loop *FalseLoop = CloneLoop(L, LPM, LI, ValueMap, this);
- BasicBlock *FalseHeader = FalseLoop->getHeader();
-
- //[*] True loop's exit edge enters False loop.
- PHINode *IndVarClone = cast<PHINode>(ValueMap[IndVar]);
- BasicBlock *ExitBlock = ExitCondition->getParent();
- BranchInst *ExitInsn = dyn_cast<BranchInst>(ExitBlock->getTerminator());
- assert (ExitInsn && "Unable to find suitable loop exit branch");
- BasicBlock *ExitDest = ExitInsn->getSuccessor(1);
-
- if (L->contains(ExitDest)) {
- ExitDest = ExitInsn->getSuccessor(0);
- ExitInsn->setSuccessor(0, FalseHeader);
+ Loop *BLoop = CloneLoop(L, LPM, LI, ValueMap, this);
+ Loop *ALoop = L;
+
+ // [*] ALoop's exiting edge enters BLoop's header.
+ // ALoop's original exit block becomes BLoop's exit block.
+ PHINode *B_IndVar = cast<PHINode>(ValueMap[IndVar]);
+ BasicBlock *A_ExitingBlock = ExitCondition->getParent();
+ BranchInst *A_ExitInsn =
+ dyn_cast<BranchInst>(A_ExitingBlock->getTerminator());
+ assert (A_ExitInsn && "Unable to find suitable loop exit branch");
+ BasicBlock *B_ExitBlock = A_ExitInsn->getSuccessor(1);
+ BasicBlock *B_Header = BLoop->getHeader();
+ if (ALoop->contains(B_ExitBlock)) {
+ B_ExitBlock = A_ExitInsn->getSuccessor(0);
+ A_ExitInsn->setSuccessor(0, B_Header);
} else
- ExitInsn->setSuccessor(1, FalseHeader);
+ A_ExitInsn->setSuccessor(1, B_Header);
+
+ // [*] Update ALoop's exit value using new exit value.
+ ExitCondition->setOperand(EVOpNum, AEV);
+
+ // [*] Update BLoop's header phi nodes. Remove incoming PHINode's from
+ // original loop's preheader. Add incoming PHINode values from
+ // ALoop's exiting block. Update BLoop header's domiantor info.
// Collect inverse map of Header PHINodes.
DenseMap<Value *, Value *> InverseMap;
- for (BasicBlock::iterator BI = L->getHeader()->begin(),
- BE = L->getHeader()->end(); BI != BE; ++BI) {
+ for (BasicBlock::iterator BI = ALoop->getHeader()->begin(),
+ BE = ALoop->getHeader()->end(); BI != BE; ++BI) {
if (PHINode *PN = dyn_cast<PHINode>(BI)) {
PHINode *PNClone = cast<PHINode>(ValueMap[PN]);
InverseMap[PNClone] = PN;
break;
}
- // Update False loop's header
- for (BasicBlock::iterator BI = FalseHeader->begin(), BE = FalseHeader->end();
+ BasicBlock *A_Preheader = ALoop->getLoopPreheader();
+ for (BasicBlock::iterator BI = B_Header->begin(), BE = B_Header->end();
BI != BE; ++BI) {
if (PHINode *PN = dyn_cast<PHINode>(BI)) {
- PN->removeIncomingValue(Preheader);
- if (PN == IndVarClone)
- PN->addIncoming(FLStartValue, ExitBlock);
+ // Remove incoming value from original preheader.
+ PN->removeIncomingValue(A_Preheader);
+
+ // Add incoming value from A_ExitingBlock.
+ if (PN == B_IndVar)
+ PN->addIncoming(BSV, A_ExitingBlock);
else {
PHINode *OrigPN = cast<PHINode>(InverseMap[PN]);
- Value *V2 = OrigPN->getIncomingValueForBlock(ExitBlock);
- PN->addIncoming(V2, ExitBlock);
+ Value *V2 = NULL;
+ // If loop header is also loop exiting block then
+ // OrigPN is incoming value for B loop header.
+ if (A_ExitingBlock == ALoop->getHeader())
+ V2 = OrigPN;
+ else
+ V2 = OrigPN->getIncomingValueForBlock(A_ExitingBlock);
+ PN->addIncoming(V2, A_ExitingBlock);
}
} else
break;
}
- // Update ExitDest. Now it's predecessor is False loop's exit block.
- BasicBlock *ExitBlockClone = cast<BasicBlock>(ValueMap[ExitBlock]);
- for (BasicBlock::iterator BI = ExitDest->begin(), BE = ExitDest->end();
+ DT->changeImmediateDominator(B_Header, A_ExitingBlock);
+ DF->changeImmediateDominator(B_Header, A_ExitingBlock, DT);
+
+ // [*] Update BLoop's exit block. Its new predecessor is BLoop's exit
+ // block. Remove incoming PHINode values from ALoop's exiting block.
+ // Add new incoming values from BLoop's incoming exiting value.
+ // Update BLoop exit block's dominator info..
+ BasicBlock *B_ExitingBlock = cast<BasicBlock>(ValueMap[A_ExitingBlock]);
+ for (BasicBlock::iterator BI = B_ExitBlock->begin(), BE = B_ExitBlock->end();
BI != BE; ++BI) {
if (PHINode *PN = dyn_cast<PHINode>(BI)) {
- PN->addIncoming(ValueMap[PN->getIncomingValueForBlock(ExitBlock)], ExitBlockClone);
- PN->removeIncomingValue(ExitBlock);
+ PN->addIncoming(ValueMap[PN->getIncomingValueForBlock(A_ExitingBlock)],
+ B_ExitingBlock);
+ PN->removeIncomingValue(A_ExitingBlock);
} else
break;
}
- if (DT) {
- DT->changeImmediateDominator(FalseHeader, ExitBlock);
- DT->changeImmediateDominator(ExitDest, cast<BasicBlock>(ValueMap[ExitBlock]));
+ DT->changeImmediateDominator(B_ExitBlock, B_ExitingBlock);
+ DF->changeImmediateDominator(B_ExitBlock, B_ExitingBlock, DT);
+
+ //[*] Split ALoop's exit edge. This creates a new block which
+ // serves two purposes. First one is to hold PHINode defnitions
+ // to ensure that ALoop's LCSSA form. Second use it to act
+ // as a preheader for BLoop.
+ BasicBlock *A_ExitBlock = SplitEdge(A_ExitingBlock, B_Header, this);
+
+ //[*] Preserve ALoop's LCSSA form. Create new forwarding PHINodes
+ // in A_ExitBlock to redefine outgoing PHI definitions from ALoop.
+ for(BasicBlock::iterator BI = B_Header->begin(), BE = B_Header->end();
+ BI != BE; ++BI) {
+ if (PHINode *PN = dyn_cast<PHINode>(BI)) {
+ Value *V1 = PN->getIncomingValueForBlock(A_ExitBlock);
+ PHINode *newPHI = PHINode::Create(PN->getType(), PN->getName());
+ newPHI->addIncoming(V1, A_ExitingBlock);
+ A_ExitBlock->getInstList().push_front(newPHI);
+ PN->removeIncomingValue(A_ExitBlock);
+ PN->addIncoming(newPHI, A_ExitBlock);
+ } else
+ break;
}
- assert (!L->contains(ExitDest) && " Unable to find exit edge destination");
+ //[*] Eliminate split condition's inactive branch from ALoop.
+ BasicBlock *A_SplitCondBlock = SplitCondition->getParent();
+ BranchInst *A_BR = cast<BranchInst>(A_SplitCondBlock->getTerminator());
+ BasicBlock *A_InactiveBranch = NULL;
+ BasicBlock *A_ActiveBranch = NULL;
+ A_ActiveBranch = A_BR->getSuccessor(0);
+ A_InactiveBranch = A_BR->getSuccessor(1);
+ 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 = NULL;
+ BasicBlock *B_ActiveBranch = NULL;
+ B_ActiveBranch = B_BR->getSuccessor(1);
+ B_InactiveBranch = B_BR->getSuccessor(0);
+ B_BR->setUnconditionalDest(B_ActiveBranch);
+ removeBlocks(B_InactiveBranch, BLoop, B_ActiveBranch);
+
+ BasicBlock *A_Header = ALoop->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[IVIncrement]);
+ ICmpInst *B_SplitCondition = cast<ICmpInst>(ValueMap[SplitCondition]);
+
+ moveExitCondition(A_SplitCondBlock, A_ActiveBranch, A_ExitBlock, ExitCondition,
+ cast<ICmpInst>(SplitCondition), IndVar, IVIncrement,
+ ALoop, EVOpNum);
+
+ moveExitCondition(B_SplitCondBlock, B_ActiveBranch,
+ B_ExitBlock, B_ExitCondition,
+ B_SplitCondition, B_IndVar, B_IndVarIncrement,
+ BLoop, EVOpNum);
+
+ NumIndexSplit++;
+ return true;
+}
- //[*] Split Exit Edge.
- SplitEdge(ExitBlock, FalseHeader, this);
+/// cleanBlock - A block is considered clean if all non terminal instructions
+/// are either, PHINodes, IV based.
+bool LoopIndexSplit::cleanBlock(BasicBlock *BB) {
+ Instruction *Terminator = BB->getTerminator();
+ for(BasicBlock::iterator BI = BB->begin(), BE = BB->end();
+ BI != BE; ++BI) {
+ Instruction *I = BI;
- //[*] Eliminate split condition's false branch from True loop.
- BranchInst *BR = cast<BranchInst>(SplitBlock->getTerminator());
- BasicBlock *FBB = BR->getSuccessor(1);
- BR->setUnconditionalDest(BR->getSuccessor(0));
- removeBlocks(FBB, L, BR->getSuccessor(0));
+ if (isa<PHINode>(I) || I == Terminator || I == ExitCondition
+ || I == SplitCondition || IVBasedValues.count(I)
+ || isa<DbgInfoIntrinsic>(I))
+ continue;
- //[*] Update True loop's exit value using new exit value.
- ExitCondition->setOperand(ExitValueNum, TLExitValue);
+ if (I->mayWriteToMemory())
+ return false;
- //[*] Eliminate split condition's true branch in False loop CFG.
- BasicBlock *FSplitBlock = cast<BasicBlock>(ValueMap[SplitBlock]);
- BranchInst *FBR = cast<BranchInst>(FSplitBlock->getTerminator());
- BasicBlock *TBB = FBR->getSuccessor(0);
- FBR->setUnconditionalDest(FBR->getSuccessor(1));
- removeBlocks(TBB, FalseLoop, cast<BasicBlock>(FBR->getSuccessor(0)));
+ // I is used only inside this block then it is OK.
+ bool usedOutsideBB = false;
+ for (Value::use_iterator UI = I->use_begin(), UE = I->use_end();
+ UI != UE; ++UI) {
+ Instruction *U = cast<Instruction>(UI);
+ if (U->getParent() != BB)
+ usedOutsideBB = true;
+ }
+ if (!usedOutsideBB)
+ continue;
+ // Otherwise we have a instruction that may not allow loop spliting.
+ return false;
+ }
return true;
}
+/// IVisLT - If Op is comparing IV based value with an loop invariant and
+/// IV based value is less than the loop invariant then return the loop
+/// invariant. Otherwise return NULL.
+Value * LoopIndexSplit::IVisLT(ICmpInst &Op) {
+ ICmpInst::Predicate P = Op.getPredicate();
+ if ((P == ICmpInst::ICMP_SLT || P == ICmpInst::ICMP_ULT)
+ && IVBasedValues.count(Op.getOperand(0))
+ && L->isLoopInvariant(Op.getOperand(1)))
+ return Op.getOperand(1);
+
+ if ((P == ICmpInst::ICMP_SGT || P == ICmpInst::ICMP_UGT)
+ && IVBasedValues.count(Op.getOperand(1))
+ && L->isLoopInvariant(Op.getOperand(0)))
+ return Op.getOperand(0);
+
+ return NULL;
+}
+
+/// IVisLE - If Op is comparing IV based value with an loop invariant and
+/// IV based value is less than or equal to the loop invariant then
+/// return the loop invariant. Otherwise return NULL.
+Value * LoopIndexSplit::IVisLE(ICmpInst &Op) {
+ ICmpInst::Predicate P = Op.getPredicate();
+ if ((P == ICmpInst::ICMP_SLE || P == ICmpInst::ICMP_ULE)
+ && IVBasedValues.count(Op.getOperand(0))
+ && L->isLoopInvariant(Op.getOperand(1)))
+ return Op.getOperand(1);
+
+ if ((P == ICmpInst::ICMP_SGE || P == ICmpInst::ICMP_UGE)
+ && IVBasedValues.count(Op.getOperand(1))
+ && L->isLoopInvariant(Op.getOperand(0)))
+ return Op.getOperand(0);
+
+ return NULL;
+}
+
+/// IVisGT - If Op is comparing IV based value with an loop invariant and
+/// IV based value is greater than the loop invariant then return the loop
+/// invariant. Otherwise return NULL.
+Value * LoopIndexSplit::IVisGT(ICmpInst &Op) {
+ ICmpInst::Predicate P = Op.getPredicate();
+ if ((P == ICmpInst::ICMP_SGT || P == ICmpInst::ICMP_UGT)
+ && IVBasedValues.count(Op.getOperand(0))
+ && L->isLoopInvariant(Op.getOperand(1)))
+ return Op.getOperand(1);
+
+ if ((P == ICmpInst::ICMP_SLT || P == ICmpInst::ICMP_ULT)
+ && IVBasedValues.count(Op.getOperand(1))
+ && L->isLoopInvariant(Op.getOperand(0)))
+ return Op.getOperand(0);
+
+ return NULL;
+}
+
+/// IVisGE - If Op is comparing IV based value with an loop invariant and
+/// IV based value is greater than or equal to the loop invariant then
+/// return the loop invariant. Otherwise return NULL.
+Value * LoopIndexSplit::IVisGE(ICmpInst &Op) {
+ ICmpInst::Predicate P = Op.getPredicate();
+ if ((P == ICmpInst::ICMP_SGE || P == ICmpInst::ICMP_UGE)
+ && IVBasedValues.count(Op.getOperand(0))
+ && L->isLoopInvariant(Op.getOperand(1)))
+ return Op.getOperand(1);
+
+ if ((P == ICmpInst::ICMP_SLE || P == ICmpInst::ICMP_ULE)
+ && IVBasedValues.count(Op.getOperand(1))
+ && L->isLoopInvariant(Op.getOperand(0)))
+ return Op.getOperand(0);
+
+ return NULL;
+}
+
projects / oota-llvm.git / blobdiff