// 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,
+// [1] A loop may be eliminated if the body is executed exactly once.
+// For example,
+//
// for (i = 0; i < N; ++i) {
-// if ( i == X) {
-// ...
+// if (i == X) {
+// body;
// }
// }
//
-// [2] Loop's iteration space is shrunk if loop body is executed for certain
-// range only. For example,
-//
+// is transformed to
+//
+// i = X;
+// body;
+//
+// [2] A loop's iteration space may be shrunk if the loop body is executed
+// for a proper sub-range of the loop's iteration space. For example,
+//
// for (i = 0; i < N; ++i) {
-// if ( i > A && i < B) {
+// 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,
+// is transformed to iterators from A to B, if A > 0 and B < N.
+//
+// [3] A loop may be split if the loop body is dominated by a 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/LLVMContext.h"
#include "llvm/Analysis/LoopPass.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"
namespace {
- class VISIBILITY_HIDDEN LoopIndexSplit : public LoopPass {
-
+ class LoopIndexSplit : public LoopPass {
public:
static char ID; // Pass ID, replacement for typeid
LoopIndexSplit() : LoopPass(&ID) {}
}
char LoopIndexSplit::ID = 0;
-static RegisterPass<LoopIndexSplit>
-X("loop-index-split", "Index Split Loops");
+INITIALIZE_PASS(LoopIndexSplit, "loop-index-split",
+ "Index Split Loops", false, false);
Pass *llvm::createLoopIndexSplitPass() {
return new LoopIndexSplit();
L = IncomingLoop;
LPM = &LPM_Ref;
+ // If LoopSimplify form is not available, stay out of trouble.
+ if (!L->isLoopSimplifyForm())
+ return false;
+
// FIXME - Nested loops make dominator info updates tricky.
if (!L->getSubLoops().empty())
return false;
IVExitValue = ExitCondition->getOperand(0);
if (!L->isLoopInvariant(IVExitValue))
return false;
+ if (!IVBasedValues.count(
+ ExitCondition->getOperand(IVExitValue == ExitCondition->getOperand(0))))
+ 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.
// 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()))
+ if (!L->contains(cast<Instruction>(*UI)))
return true;
return false;
}
// Return V+1
-static Value *getPlusOne(Value *V, bool Sign, Instruction *InsertPt) {
- ConstantInt *One = ConstantInt::get(V->getType(), 1, Sign);
+static Value *getPlusOne(Value *V, bool Sign, Instruction *InsertPt,
+ LLVMContext &Context) {
+ Constant *One = ConstantInt::get(V->getType(), 1, Sign);
return BinaryOperator::CreateAdd(V, One, "lsp", InsertPt);
}
// Return V-1
-static Value *getMinusOne(Value *V, bool Sign, Instruction *InsertPt) {
- ConstantInt *One = ConstantInt::get(V->getType(), 1, Sign);
+static Value *getMinusOne(Value *V, bool Sign, Instruction *InsertPt,
+ LLVMContext &Context) {
+ Constant *One = ConstantInt::get(V->getType(), 1, Sign);
return BinaryOperator::CreateSub(V, One, "lsp", InsertPt);
}
// 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);
+ Value *C = new ICmpInst(InsertPt,
+ Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
+ V1, V2, "lsp");
return SelectInst::Create(C, V1, V2, "lsp", InsertPt);
}
// 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);
+ Value *C = new ICmpInst(InsertPt,
+ Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
+ V1, V2, "lsp");
return SelectInst::Create(C, V2, V1, "lsp", InsertPt);
}
// 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))
+ std::swap(OPV, SplitValue);
if (!L->isLoopInvariant(SplitValue))
return false;
Instruction *OPI = dyn_cast<Instruction>(OPV);
// c1 = icmp uge i32 SplitValue, StartValue
// c2 = icmp ult i32 SplitValue, ExitValue
// and i32 c1, c2
- Instruction *C1 = new ICmpInst(ExitCondition->isSignedPredicate() ?
+ Instruction *C1 = new ICmpInst(BR, ExitCondition->isSigned() ?
ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE,
- SplitValue, StartValue, "lisplit", BR);
+ SplitValue, StartValue, "lisplit");
CmpInst::Predicate C2P = ExitCondition->getPredicate();
BranchInst *LatchBR = cast<BranchInst>(Latch->getTerminator());
- if (LatchBR->getOperand(0) != Header)
+ if (LatchBR->getOperand(1) != Header)
C2P = CmpInst::getInversePredicate(C2P);
- Instruction *C2 = new ICmpInst(C2P, SplitValue, ExitValue, "lisplit", BR);
+ Instruction *C2 = new ICmpInst(BR, C2P, SplitValue, ExitValue, "lisplit");
Instruction *NSplitCond = BinaryOperator::CreateAnd(C1, C2, "lisplit", BR);
SplitCondition->replaceAllUsesWith(NSplitCond);
/// 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();
+ bool Sign = Op.isSigned();
Instruction *PHTerm = L->getLoopPreheader()->getTerminator();
if (IVisGT(*ExitCondition) || IVisGE(*ExitCondition)) {
EBR->setSuccessor(1, T);
}
+ LLVMContext &Context = Op.getContext();
+
// 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);
+ V = getMinusOne(V, Sign, PHTerm, Context);
NUB = getMin(V, IVExitValue, Sign, PHTerm);
} else if (Value *V = IVisLE(Op)) {
// Restrict upper bound.
if (IVisLT(*ExitCondition))
- V = getPlusOne(V, Sign, PHTerm);
+ V = getPlusOne(V, Sign, PHTerm, Context);
NUB = getMin(V, IVExitValue, Sign, PHTerm);
} else if (Value *V = IVisGT(Op)) {
// Restrict lower bound.
- V = getPlusOne(V, Sign, PHTerm);
+ V = getPlusOne(V, Sign, PHTerm, Context);
NLB = getMax(V, IVStartValue, Sign, PHTerm);
} else if (Value *V = IVisGE(Op))
// Restrict lower bound.
}
}
}
- NumRestrictBounds++;
+ ++NumRestrictBounds;
return true;
}
E = df_end(DN); DI != E; ++DI) {
BasicBlock *BB = DI->getBlock();
WorkList.push_back(BB);
- BB->replaceAllUsesWith(UndefValue::get(Type::LabelTy));
+ BB->replaceAllUsesWith(UndefValue::get(
+ Type::getLabelTy(DeadBB->getContext())));
}
while (!WorkList.empty()) {
- BasicBlock *BB = WorkList.back(); WorkList.pop_back();
+ BasicBlock *BB = WorkList.pop_back_val();
LPM->deleteSimpleAnalysisValue(BB, LP);
for(BasicBlock::iterator BBI = BB->begin(), BBE = BB->end();
BBI != BBE; ) {
// Update Frontier BBs' dominator info.
while (!FrontierBBs.empty()) {
- BasicBlock *FBB = FrontierBBs.back(); FrontierBBs.pop_back();
+ BasicBlock *FBB = FrontierBBs.pop_back_val();
BasicBlock *NewDominator = FBB->getSinglePredecessor();
if (!NewDominator) {
pred_iterator PI = pred_begin(FBB), PE = pred_end(FBB);
// 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);
+
+ // Blocks outside the loop may have been in the dominance frontier of blocks
+ // inside the condition; this is now impossible because the blocks inside the
+ // condition no loger dominate the exit. Remove the relevant blocks from
+ // the dominance frontiers.
+ for (Loop::block_iterator I = LP->block_begin(), E = LP->block_end();
+ I != E; ++I) {
+ if (*I == CondBB || !DT->dominates(CondBB, *I)) continue;
+ DominanceFrontier::iterator BBDF = DF->find(*I);
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)) {
+ if (!LP->contains(DFBB))
BBDF->second.erase(DFBB);
- BBDF->second.insert(CondBB);
- }
}
}
}
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())) {
+ if (LP->contains(U)) {
NewV = U;
break;
}
BasicBlock *ExitingBlock = ExitCondition->getParent();
if (!cleanBlock(ExitingBlock)) return false;
+ LLVMContext &Context = Header->getContext();
+
for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
I != E; ++I) {
BranchInst *BR = dyn_cast<BranchInst>((*I)->getTerminator());
return false;
// If the predicate sign does not match then skip.
- if (ExitCondition->isSignedPredicate() != SplitCondition->isSignedPredicate())
+ if (ExitCondition->isSigned() != SplitCondition->isSigned())
return false;
unsigned EVOpNum = (ExitCondition->getOperand(1) == IVExitValue);
if (!IVBasedValues.count(SplitCondition->getOperand(!SVOpNum)))
return false;
+ // Check for side effects.
+ for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
+ I != E; ++I) {
+ BasicBlock *BB = *I;
+
+ assert(DT->dominates(Header, BB));
+ if (DT->properlyDominates(SplitCondition->getParent(), BB))
+ continue;
+
+ for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();
+ BI != BE; ++BI) {
+ Instruction *Inst = BI;
+
+ if (!Inst->isSafeToSpeculativelyExecute() && !isa<PHINode>(Inst)
+ && !isa<BranchInst>(Inst) && !isa<DbgInfoIntrinsic>(Inst))
+ return false;
+ }
+ }
+
// Normalize loop conditions so that it is easier to calculate new loop
// bounds.
if (IVisGT(*ExitCondition) || IVisGE(*ExitCondition)) {
//[*] Calculate new loop bounds.
Value *AEV = SplitValue;
Value *BSV = SplitValue;
- bool Sign = SplitCondition->isSignedPredicate();
+ bool Sign = SplitCondition->isSigned();
Instruction *PHTerm = L->getLoopPreheader()->getTerminator();
if (IVisLT(*ExitCondition)) {
/* Do nothing */
}
else if (IVisLE(*SplitCondition)) {
- AEV = getPlusOne(SplitValue, Sign, PHTerm);
- BSV = getPlusOne(SplitValue, Sign, PHTerm);
+ AEV = getPlusOne(SplitValue, Sign, PHTerm, Context);
+ BSV = getPlusOne(SplitValue, Sign, PHTerm, Context);
} else {
assert (0 && "Unexpected split condition!");
}
}
else if (IVisLE(*ExitCondition)) {
if (IVisLT(*SplitCondition)) {
- AEV = getMinusOne(SplitValue, Sign, PHTerm);
+ AEV = getMinusOne(SplitValue, Sign, PHTerm, Context);
}
else if (IVisLE(*SplitCondition)) {
- BSV = getPlusOne(SplitValue, Sign, PHTerm);
+ BSV = getPlusOne(SplitValue, Sign, PHTerm, Context);
} else {
assert (0 && "Unexpected split condition!");
}
BSV = getMax(BSV, IVStartValue, Sign, PHTerm);
// [*] Clone Loop
- DenseMap<const Value *, Value *> ValueMap;
- Loop *BLoop = CloneLoop(L, LPM, LI, ValueMap, this);
+ ValueMap<const Value *, Value *> VMap;
+ Loop *BLoop = CloneLoop(L, LPM, LI, VMap, 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]);
+ PHINode *B_IndVar = cast<PHINode>(VMap[IndVar]);
BasicBlock *A_ExitingBlock = ExitCondition->getParent();
BranchInst *A_ExitInsn =
dyn_cast<BranchInst>(A_ExitingBlock->getTerminator());
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]);
+ PHINode *PNClone = cast<PHINode>(VMap[PN]);
InverseMap[PNClone] = PN;
} else
break;
// 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]);
+ BasicBlock *B_ExitingBlock = cast<BasicBlock>(VMap[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(A_ExitingBlock)],
+ PN->addIncoming(VMap[PN->getIncomingValueForBlock(A_ExitingBlock)],
B_ExitingBlock);
PN->removeIncomingValue(A_ExitingBlock);
} else
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.
removeBlocks(A_InactiveBranch, L, A_ActiveBranch);
//[*] Eliminate split condition's inactive branch in from BLoop.
- BasicBlock *B_SplitCondBlock = cast<BasicBlock>(ValueMap[A_SplitCondBlock]);
+ BasicBlock *B_SplitCondBlock = cast<BasicBlock>(VMap[A_SplitCondBlock]);
BranchInst *B_BR = cast<BranchInst>(B_SplitCondBlock->getTerminator());
BasicBlock *B_InactiveBranch = NULL;
BasicBlock *B_ActiveBranch = NULL;
//[*] 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]);
+ ICmpInst *B_ExitCondition = cast<ICmpInst>(VMap[ExitCondition]);
+ Instruction *B_IndVarIncrement = cast<Instruction>(VMap[IVIncrement]);
+ ICmpInst *B_SplitCondition = cast<ICmpInst>(VMap[SplitCondition]);
moveExitCondition(A_SplitCondBlock, A_ActiveBranch, A_ExitBlock, ExitCondition,
cast<ICmpInst>(SplitCondition), IndVar, IVIncrement,
B_SplitCondition, B_IndVar, B_IndVarIncrement,
BLoop, EVOpNum);
- NumIndexSplit++;
+ ++NumIndexSplit;
return true;
}
|| isa<DbgInfoIntrinsic>(I))
continue;
- if (I->mayWriteToMemory())
+ if (I->mayHaveSideEffects())
return false;
// I is used only inside this block then it is OK.
projects / oota-llvm.git / blobdiff