//
//===----------------------------------------------------------------------===//
//
-// 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/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 {
bool runOnLoop(Loop *L, LPPassManager &LPM);
void getAnalysisUsage(AnalysisUsage &AU) const {
- AU.addRequired<ScalarEvolution>();
AU.addPreserved<ScalarEvolution>();
AU.addRequiredID(LCSSAID);
AU.addPreservedID(LCSSAID);
}
private:
+ /// 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();
- class SplitInfo {
- public:
- 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 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();
+ /// 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);
- /// Find loop's exit condition.
- void findLoopConditionals();
+ // --- Routines used by splitLoop(). --- /
- /// Return induction variable associated with value V.
- void findIndVar(Value *V, Loop *L);
+ bool splitLoop();
- /// 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);
-
- /// isOneIterationLoop - Return true if split condition is EQ and
- /// the IV is not used outside the loop.
- bool isOneIterationLoop(ICmpInst *CI);
-
- 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);
-
- /// If Exiting block includes loop variant instructions then this
- /// loop may not be eliminated.
- bool safeExitingBlock(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.
+ /// 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);
-
- /// 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);
-
+
+ /// 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);
+
/// updatePHINodes - CFG has been changed.
/// Before
/// - ExitBB's single predecessor was 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);
-
- void initialize() {
- IndVar = NULL;
- IndVarIncrement = NULL;
- ExitCondition = NULL;
- StartValue = NULL;
- ExitValueNum = 0;
- SplitData.clear();
- }
+ // --- 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;
};
}
static RegisterPass<LoopIndexSplit>
X("loop-index-split", "Index Split Loops");
-LoopPass *llvm::createLoopIndexSplitPass() {
+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 = &getAnalysis<DominanceFrontier>();
- initialize();
-
- findLoopConditionals();
-
- if (!ExitCondition)
- return false;
-
- findSplitCondition();
-
- if (SplitData.empty())
- return false;
-
- // First see if it is possible to eliminate loop itself or not.
- for (SmallVector<SplitInfo, 4>::iterator SI = SplitData.begin();
- SI != SplitData.end();) {
- SplitInfo &SD = *SI;
- 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 (isOneIterationLoop(CI)) {
- Changed = processOneIterationLoop(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
- ++SI;
- }
-
- if (SplitData.empty())
- return false;
-
- // Split most profitiable condition.
- // FIXME : Implement cost analysis.
- unsigned MostProfitableSDIndex = 0;
- Changed = splitLoop(SplitData[MostProfitableSDIndex]);
-
- if (Changed)
- ++NumIndexSplit;
-
- return Changed;
-}
-
-/// isOneIterationLoop - Return true if split condition is EQ and
-/// the IV is not used outside the loop.
-bool LoopIndexSplit::isOneIterationLoop(ICmpInst *CI) {
- if (!CI)
- return false;
- if (CI->getPredicate() != ICmpInst::ICMP_EQ)
- return false;
-
- Value *Incr = IndVar->getIncomingValueForBlock(L->getLoopLatch());
- for (Value::use_iterator UI = Incr->use_begin(), E = Incr->use_end();
- UI != E; ++UI)
- if (!L->contains(cast<Instruction>(*UI)->getParent()))
- return false;
-
- return true;
-}
-/// 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())
- if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1))
- if (CI->isOne()) {
- IndVar = PN;
- IndVarIncrement = I;
- return;
- }
+ // Initialize loop data.
+ IndVar = L->getCanonicalInductionVariable();
+ if (!IndVar) return false;
- 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;
- }
+ bool P1InLoop = L->contains(IndVar->getIncomingBlock(1));
+ IVStartValue = IndVar->getIncomingValue(!P1InLoop);
+ IVIncrement = dyn_cast<Instruction>(IndVar->getIncomingValue(P1InLoop));
+ if (!IVIncrement) return false;
- return;
-}
-
-// Find loop's exit condition and associated induction variable.
-void LoopIndexSplit::findLoopConditionals() {
-
- BasicBlock *ExitingBlock = NULL;
-
+ IVBasedValues.clear();
+ IVBasedValues.insert(IndVar);
+ IVBasedValues.insert(IVIncrement);
for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
- I != E; ++I) {
- BasicBlock *BB = *I;
- if (!L->isLoopExit(BB))
- continue;
- if (ExitingBlock)
- return;
- ExitingBlock = BB;
- }
+ 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);
+ }
+ // Reject loop if loop exit condition is not suitable.
+ BasicBlock *ExitingBlock = L->getExitingBlock();
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());
- if (!BR || BR->isUnconditional())
- return;
-
- 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
- // 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 false;
+ 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;
// If start value is more then exit value where induction variable
// increments by 1 then we are potentially dealing with an infinite loop.
// Do not index split this loop.
- if (ExitCondition) {
- ConstantInt *SV = dyn_cast<ConstantInt>(StartValue);
- ConstantInt *EV =
- dyn_cast<ConstantInt>(ExitCondition->getOperand(ExitValueNum));
- if (SV && EV && SV->getSExtValue() > EV->getSExtValue())
- ExitCondition = NULL;
- else if (EV && EV->isZero())
- ExitCondition = NULL;
- }
-}
+ if (ConstantInt *SV = dyn_cast<ConstantInt>(IVStartValue))
+ if (ConstantInt *EV = dyn_cast<ConstantInt>(IVExitValue))
+ if (SV->getSExtValue() > EV->getSExtValue())
+ return false;
-/// 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) {
- SD.clear();
- BasicBlock *BB = *I;
+ if (processOneIterationLoop())
+ return true;
- // 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;
+ if (updateLoopIterationSpace())
+ return true;
- if (Instruction *AndI = dyn_cast<Instruction>(BR->getCondition())) {
- if (AndI->getOpcode() == Instruction::And) {
- ICmpInst *Op0 = dyn_cast<ICmpInst>(AndI->getOperand(0));
- ICmpInst *Op1 = dyn_cast<ICmpInst>(AndI->getOperand(1));
-
- if (!Op0 || !Op1)
- continue;
-
- if (!safeICmpInst(Op0, SD))
- continue;
- SD.clear();
- if (!safeICmpInst(Op1, SD))
- continue;
- SD.clear();
- SD.SplitCondition = AndI;
- SplitData.push_back(SD);
- continue;
- }
- }
- ICmpInst *CI = dyn_cast<ICmpInst>(BR->getCondition());
- if (!CI || CI == ExitCondition)
- continue;
+ if (splitLoop())
+ return true;
- if (CI->getPredicate() == ICmpInst::ICMP_NE)
- continue;
+ return false;
+}
- // 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.
- if (safeICmpInst(CI, SD))
- SplitData.push_back(SD);
- }
+// --- 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;
}
-// 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) {
+// 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);
+}
- 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 (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 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);
+}
- return false;
+// 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)
- return false;
-
- // If loop header includes loop variant instruction operands then
- // this loop may not be eliminated.
- if (!safeHeader(SD, 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 Exiting block includes loop variant instructions then this
- // loop may not be eliminated.
- if (!safeExitingBlock(SD, ExitCondition->getParent()))
+ // 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;
- // Filter loops where split condition's false branch is not empty.
- if (ExitCondition->getParent() != Header->getTerminator()->getSuccessor(1))
+ // 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;
-
- // 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))
+ 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);
+ }
- BasicBlock *Latch = L->getLoopLatch();
- BranchInst *BR = dyn_cast<BranchInst>(Latch->getTerminator());
- if (!BR)
+ if (!cleanBlock(Header))
return false;
- // Update CFG.
+ if (!cleanBlock(Latch))
+ 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;
+ }
+
+ // 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(SD.SplitValue);
-
- // 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;
- }
- BR->setUnconditionalDest(LatchSucc);
-
- Instruction *Terminator = Header->getTerminator();
- Value *ExitValue = ExitCondition->getOperand(ExitValueNum);
+ IndVar->replaceAllUsesWith(SplitValue);
// Replace split condition in header.
// Transform
// c1 = icmp uge i32 SplitValue, StartValue
// 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) {
- // Replace induction variable increment if it is not used outside
- // the loop.
- bool UsedOutsideLoop = false;
- for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
- UI != E; ++UI) {
- if (Instruction *Use = dyn_cast<Instruction>(UI))
- if (!L->contains(Use->getParent())) {
- UsedOutsideLoop = true;
- break;
- }
- }
- if (!UsedOutsideLoop) {
- I->replaceAllUsesWith(ExitValue);
- I->eraseFromParent();
- }
- }
- else {
- I->replaceAllUsesWith(UndefValue::get(I->getType()));
- I->eraseFromParent();
- }
+ 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 Exiting block includes loop variant instructions then this
-// loop may not be eliminated. This is used by processOneIterationLoop().
-bool LoopIndexSplit::safeExitingBlock(SplitInfo &SD,
- BasicBlock *ExitingBlock) {
-
- for (BasicBlock::iterator BI = ExitingBlock->begin(),
- BE = ExitingBlock->end(); BI != BE; ++BI) {
- Instruction *I = BI;
-
- // PHI Nodes are OK.
- if (isa<PHINode>(I))
- continue;
+/// 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;
- // Induction variable increment is OK.
- if (IndVarIncrement && IndVarIncrement == I)
+ // 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;
+ }
- // Check if I is induction variable increment instruction.
- if (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)))
- 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)))
- if (CI->isOne()) {
- if (!IndVarIncrement && PN == IndVar)
- IndVarIncrement = I;
- // else this is another loop induction variable
- 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 == ExitingBlock->getTerminator())
- continue;
+ if (!restrictLoopBound(*Op0))
+ return false;
- // Otherwise we have instruction that may not be safe.
+ if (!restrictLoopBound(*Op1))
return false;
- }
- // We could not find any reason to consider ExitingBlock unsafe.
- return true;
-}
+ // Update CFG.
+ if (BR->getSuccessor(0) == ExitingBlock)
+ BR->setUnconditionalDest(BR->getSuccessor(1));
+ else
+ BR->setUnconditionalDest(BR->getSuccessor(0));
-void LoopIndexSplit::updateLoopBounds(ICmpInst *CI) {
+ AND->eraseFromParent();
+ if (Op0->use_empty())
+ Op0->eraseFromParent();
+ if (Op1->use_empty())
+ Op1->eraseFromParent();
- Value *V0 = CI->getOperand(0);
- Value *V1 = CI->getOperand(1);
- Value *NV = NULL;
+ // Update domiantor info. Now, ExitingBlock has only one predecessor,
+ // ExitingBBPred, and it is ExitingBlock's immediate domiantor.
+ DT->changeImmediateDominator(ExitingBlock, ExitingBBPred);
- 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;
- }
+ BasicBlock *ExitBlock = ExitingBlock->getTerminator()->getSuccessor(1);
+ if (L->contains(ExitBlock))
+ ExitBlock = ExitingBlock->getTerminator()->getSuccessor(0);
- Value *NUB = NULL;
- Value *NLB = NULL;
- Value *UB = ExitCondition->getOperand(ExitValueNum);
- const Type *Ty = NV->getType();
- bool Sign = ExitCondition->isSignedPredicate();
- BasicBlock *Preheader = L->getLoopPreheader();
- Instruction *PHTerminator = Preheader->getTerminator();
-
- assert (NV && "Unexpected value");
-
- switch (CI->getPredicate()) {
- case ICmpInst::ICMP_ULE:
- case ICmpInst::ICMP_SLE:
- // for (i = LB; i < UB; ++i)
- // if (i <= NV && ...)
- // LOOP_BODY
- //
- // is transformed into
- // NUB = min (NV+1, UB)
- // for (i = LB; i < NUB ; ++i)
- // LOOP_BODY
- //
- if (ExitCondition->getPredicate() == ICmpInst::ICMP_SLT
- || ExitCondition->getPredicate() == ICmpInst::ICMP_ULT) {
- Value *A = BinaryOperator::CreateAdd(NV, ConstantInt::get(Ty, 1, Sign),
- "lsplit.add", PHTerminator);
- Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
- A, UB,"lsplit,c", PHTerminator);
- NUB = SelectInst::Create(C, A, UB, "lsplit.nub", PHTerminator);
- }
-
- // for (i = LB; i <= UB; ++i)
- // if (i <= NV && ...)
- // LOOP_BODY
- //
- // is transformed into
- // NUB = min (NV, UB)
- // for (i = LB; i <= NUB ; ++i)
- // LOOP_BODY
- //
- else if (ExitCondition->getPredicate() == ICmpInst::ICMP_SLE
- || ExitCondition->getPredicate() == ICmpInst::ICMP_ULE) {
- Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
- NV, UB, "lsplit.c", PHTerminator);
- NUB = SelectInst::Create(C, NV, UB, "lsplit.nub", PHTerminator);
- }
- break;
- case ICmpInst::ICMP_ULT:
- case ICmpInst::ICMP_SLT:
- // for (i = LB; i < UB; ++i)
- // if (i < NV && ...)
- // LOOP_BODY
- //
- // is transformed into
- // NUB = min (NV, UB)
- // for (i = LB; i < NUB ; ++i)
- // LOOP_BODY
- //
- if (ExitCondition->getPredicate() == ICmpInst::ICMP_SLT
- || ExitCondition->getPredicate() == ICmpInst::ICMP_ULT) {
- Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
- NV, UB, "lsplit.c", PHTerminator);
- NUB = SelectInst::Create(C, NV, UB, "lsplit.nub", PHTerminator);
- }
-
- // for (i = LB; i <= UB; ++i)
- // if (i < NV && ...)
- // LOOP_BODY
- //
- // is transformed into
- // NUB = min (NV -1 , UB)
- // for (i = LB; i <= NUB ; ++i)
- // LOOP_BODY
- //
- else if (ExitCondition->getPredicate() == ICmpInst::ICMP_SLE
- || ExitCondition->getPredicate() == ICmpInst::ICMP_ULE) {
- Value *S = BinaryOperator::CreateSub(NV, ConstantInt::get(Ty, 1, Sign),
- "lsplit.add", PHTerminator);
- Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
- S, UB, "lsplit.c", PHTerminator);
- NUB = SelectInst::Create(C, S, UB, "lsplit.nub", PHTerminator);
- }
- break;
- case ICmpInst::ICMP_UGE:
- case ICmpInst::ICMP_SGE:
- // for (i = LB; i (< or <=) UB; ++i)
- // if (i >= NV && ...)
- // LOOP_BODY
- //
- // is transformed into
- // NLB = max (NV, LB)
- // for (i = NLB; i (< or <=) UB ; ++i)
- // LOOP_BODY
- //
- {
- Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
- NV, StartValue, "lsplit.c", PHTerminator);
- NLB = SelectInst::Create(C, StartValue, NV, "lsplit.nlb", PHTerminator);
- }
- break;
- case ICmpInst::ICMP_UGT:
- case ICmpInst::ICMP_SGT:
- // for (i = LB; i (< or <=) UB; ++i)
- // if (i > NV && ...)
- // LOOP_BODY
- //
- // is transformed into
- // NLB = max (NV+1, LB)
- // for (i = NLB; i (< or <=) UB ; ++i)
- // LOOP_BODY
- //
- {
- Value *A = BinaryOperator::CreateAdd(NV, ConstantInt::get(Ty, 1, Sign),
- "lsplit.add", PHTerminator);
- Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
- A, StartValue, "lsplit.c", PHTerminator);
- NLB = SelectInst::Create(C, StartValue, A, "lsplit.nlb", PHTerminator);
- }
- break;
- default:
- assert ( 0 && "Unexpected split condition predicate");
- }
-
- if (NLB) {
- unsigned i = IndVar->getBasicBlockIndex(Preheader);
- IndVar->setIncomingValue(i, NLB);
- }
-
- if (NUB) {
- ExitCondition->setOperand(ExitValueNum, NUB);
- }
-}
-/// updateLoopIterationSpace - Current loop body is covered by an AND
-/// instruction whose operands compares induction variables with loop
-/// invariants. If possible, hoist this check outside the loop by
-/// updating appropriate start and end values for induction variable.
-bool LoopIndexSplit::updateLoopIterationSpace(SplitInfo &SD) {
- BasicBlock *Header = L->getHeader();
- BasicBlock *ExitingBlock = ExitCondition->getParent();
- BasicBlock *SplitCondBlock = SD.SplitCondition->getParent();
-
- ICmpInst *Op0 = cast<ICmpInst>(SD.SplitCondition->getOperand(0));
- ICmpInst *Op1 = cast<ICmpInst>(SD.SplitCondition->getOperand(1));
-
- if (Op0->getPredicate() == ICmpInst::ICMP_EQ
- || Op0->getPredicate() == ICmpInst::ICMP_NE
- || Op1->getPredicate() == ICmpInst::ICMP_EQ
- || Op1->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_empty())
- Op0->eraseFromParent();
- if (Op1->use_empty())
- 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.
+ // 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;
BasicBlock *DFBB = *CurrentItr;
if (DFBB == ExitingBlock) {
BBDF->second.erase(DFBB);
- BBDF->second.insert(Header);
- if (Header != ExitingBlock)
- BBDF->second.insert(ExitBlock);
+ for (DominanceFrontier::DomSetType::iterator
+ EBI = ExitingBlockDF->second.begin(),
+ EBE = ExitingBlockDF->second.end(); EBI != EBE; ++EBI)
+ BBDF->second.insert(*EBI);
}
}
}
-
+ NumRestrictBounds++;
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.
DominanceFrontier::DomSetType DeadBBSet = DeadBBDF->second;
for (DominanceFrontier::DomSetType::iterator DeadBBSetI = DeadBBSet.begin(),
- DeadBBSetE = DeadBBSet.end(); DeadBBSetI != DeadBBSetE; ++DeadBBSetI) {
+ DeadBBSetE = DeadBBSet.end(); DeadBBSetI != DeadBBSetE; ++DeadBBSetI)
+ {
BasicBlock *FrontierBB = *DeadBBSetI;
FrontierBBs.push_back(FrontierBB);
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();
}
- LPM->deleteSimpleAnalysisValue(BB, LP);
DT->eraseNode(BB);
DF->removeBlock(BB);
LI->removeBlock(BB);
}
-/// safeSplitCondition - Return true if it is possible to
-/// split loop using given split condition.
-bool LoopIndexSplit::safeSplitCondition(SplitInfo &SD) {
+// 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 *SplitCondBlock = SD.SplitCondition->getParent();
- BasicBlock *Latch = L->getLoopLatch();
- BranchInst *SplitTerminator =
- cast<BranchInst>(SplitCondBlock->getTerminator());
- BasicBlock *Succ0 = SplitTerminator->getSuccessor(0);
- BasicBlock *Succ1 = SplitTerminator->getSuccessor(1);
+ BasicBlock *ExitingBB = EC->getParent();
+ Instruction *CurrentBR = CondBB->getTerminator();
- // If split block does not dominate the latch then this is not a diamond.
- // Such loop may not benefit from index split.
- if (!DT->dominates(SplitCondBlock, Latch))
- return false;
+ // Move exit condition into split condition block.
+ EC->moveBefore(CurrentBR);
+ EC->setOperand(ExitValueNum == 0 ? 1 : 0, IV);
- // 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;
+ // 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();
- 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;
-}
+ // Connect exiting block to original destination.
+ BranchInst::Create(OrigDestBB, ExitingBB);
-/// 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;
- }
+ // Update PHINodes
+ updatePHINodes(ExitBB, ExitingBB, CondBB, IV, IVAdd, LP);
- 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)
+ // 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);
+ }
}
- 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)
+/// 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;
+
+ 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;
- }
- InsertPt = ++LHBI;
- }
+ }
+
+ // 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);
}
- Value *C1 = new ICmpInst(Sign ?
- ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
- AEV,
- ExitCondition->getOperand(ExitValueNum),
- "lsplit.ev", InsertPt);
-
- SD.A_ExitValue = SelectInst::Create(C1, AEV,
- ExitCondition->getOperand(ExitValueNum),
- "lsplit.ev", InsertPt);
-
- Value *C2 = new ICmpInst(Sign ?
- ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
- BSV, StartValue, "lsplit.sv",
- PHTerminator);
- SD.B_StartValue = SelectInst::Create(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))
+bool LoopIndexSplit::splitLoop() {
+ SplitCondition = NULL;
+ if (ExitCondition->getPredicate() == ICmpInst::ICMP_NE
+ || ExitCondition->getPredicate() == ICmpInst::ICMP_EQ)
return false;
+ BasicBlock *Header = L->getHeader();
+ 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 EQ is not handled.
- if (ICmpInst *ICMP = dyn_cast<ICmpInst>(SD.SplitCondition)) {
- if (ICMP->getPredicate() == ICmpInst::ICMP_EQ)
+ // 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;
}
-
- BasicBlock *SplitCondBlock = SD.SplitCondition->getParent();
-
- // Unable to handle triangle loops at the moment.
- // In triangle loop, split condition is in header and one of the
- // the split destination is loop latch. If split condition is EQ
- // then such loops are already handle in processOneIterationLoop().
- BasicBlock *Latch = L->getLoopLatch();
- BranchInst *SplitTerminator =
- cast<BranchInst>(SplitCondBlock->getTerminator());
- BasicBlock *Succ0 = SplitTerminator->getSuccessor(0);
- BasicBlock *Succ1 = SplitTerminator->getSuccessor(1);
- if (L->getHeader() == SplitCondBlock
- && (Latch == Succ0 || Latch == Succ1))
+
+ if (!SplitCondition)
return false;
- // If split condition branches heads do not have single predecessor,
- // SplitCondBlock, then is not possible to remove inactive branch.
- if (!Succ0->getSinglePredecessor() || !Succ1->getSinglePredecessor())
+ // If the predicate sign does not match then skip.
+ if (ExitCondition->isSignedPredicate() != SplitCondition->isSignedPredicate())
return false;
- // If Exiting block includes loop variant instructions then this
- // loop may not be split safely.
- if (!safeExitingBlock(SD, ExitCondition->getParent()))
+ 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;
- // After loop is cloned there are two loops.
- //
- // First loop, referred as ALoop, executes first part of loop's iteration
- // space split. Second loop, referred as BLoop, executes remaining
- // part of loop's iteration space.
- //
- // 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.
- calculateLoopBounds(SD);
-
- //[*] Clone loop.
+ // 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);
+ }
+
+ 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
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.
+ // [*] 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();
dyn_cast<BranchInst>(A_ExitingBlock->getTerminator());
assert (A_ExitInsn && "Unable to find suitable loop exit branch");
BasicBlock *B_ExitBlock = A_ExitInsn->getSuccessor(1);
- if (L->contains(B_ExitBlock)) {
+ BasicBlock *B_Header = BLoop->getHeader();
+ if (ALoop->contains(B_ExitBlock)) {
B_ExitBlock = A_ExitInsn->getSuccessor(0);
A_ExitInsn->setSuccessor(0, B_Header);
} else
A_ExitInsn->setSuccessor(1, B_Header);
- //[*] Update ALoop's exit value using new exit value.
- ExitCondition->setOperand(ExitValueNum, SD.A_ExitValue);
-
+ // [*] 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;
}
+ 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)) {
// Remove incoming value from original preheader.
- PN->removeIncomingValue(Preheader);
+ PN->removeIncomingValue(A_Preheader);
// Add incoming value from A_ExitingBlock.
if (PN == B_IndVar)
- PN->addIncoming(SD.B_StartValue, A_ExitingBlock);
+ PN->addIncoming(BSV, A_ExitingBlock);
else {
PHINode *OrigPN = cast<PHINode>(InverseMap[PN]);
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())
+ if (A_ExitingBlock == ALoop->getHeader())
V2 = OrigPN;
else
V2 = OrigPN->getIncomingValueForBlock(A_ExitingBlock);
} else
break;
}
+
DT->changeImmediateDominator(B_Header, A_ExitingBlock);
DF->changeImmediateDominator(B_Header, A_ExitingBlock, DT);
DT->changeImmediateDominator(B_ExitBlock, B_ExitingBlock);
DF->changeImmediateDominator(B_ExitBlock, B_ExitingBlock, DT);
- //[*] Split ALoop's exit edge. This creates a new block which
+ //[*] 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.
}
//[*] Eliminate split condition's inactive branch from ALoop.
- BasicBlock *A_SplitCondBlock = SD.SplitCondition->getParent();
+ BasicBlock *A_SplitCondBlock = SplitCondition->getParent();
BranchInst *A_BR = cast<BranchInst>(A_SplitCondBlock->getTerminator());
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_ActiveBranch = A_BR->getSuccessor(0);
+ A_InactiveBranch = A_BR->getSuccessor(1);
A_BR->setUnconditionalDest(A_ActiveBranch);
removeBlocks(A_InactiveBranch, L, A_ActiveBranch);
BranchInst *B_BR = cast<BranchInst>(B_SplitCondBlock->getTerminator());
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_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 = L->getHeader();
+ 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[IndVarIncrement]);
- ICmpInst *B_SplitCondition = cast<ICmpInst>(ValueMap[SD.SplitCondition]);
+ Instruction *B_IndVarIncrement = cast<Instruction>(ValueMap[IVIncrement]);
+ ICmpInst *B_SplitCondition = cast<ICmpInst>(ValueMap[SplitCondition]);
moveExitCondition(A_SplitCondBlock, A_ActiveBranch, A_ExitBlock, ExitCondition,
- cast<ICmpInst>(SD.SplitCondition), IndVar, IndVarIncrement,
- ALoop);
+ cast<ICmpInst>(SplitCondition), IndVar, IVIncrement,
+ ALoop, EVOpNum);
- moveExitCondition(B_SplitCondBlock, B_ActiveBranch, B_ExitBlock, B_ExitCondition,
- B_SplitCondition, B_IndVar, B_IndVarIncrement, BLoop);
+ moveExitCondition(B_SplitCondBlock, B_ActiveBranch,
+ B_ExitBlock, B_ExitCondition,
+ B_SplitCondition, B_IndVar, B_IndVarIncrement,
+ BLoop, EVOpNum);
+ NumIndexSplit++;
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();
+/// 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;
- // Connect exiting block to original destination.
- BranchInst::Create(OrigDestBB, ExitingBB);
+ if (isa<PHINode>(I) || I == Terminator || I == ExitCondition
+ || I == SplitCondition || IVBasedValues.count(I)
+ || isa<DbgInfoIntrinsic>(I))
+ continue;
- // Update PHINodes
- updatePHINodes(ExitBB, ExitingBB, CondBB, IV, IVAdd, LP);
+ if (I->mayWriteToMemory())
+ return false;
- // 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);
- }
+ // 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;
}
-/// 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;
+/// 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;
+}
- 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;
- }
+/// 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;
+}
- // Add incoming value from header only if PN has any use inside the loop.
- if (NewV)
- PN->addIncoming(NewV, Header);
+/// 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;
+}
- } 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);
- }
+/// 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