mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-08-30 21:29:28 +00:00
Fixes PR 2030. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@47141 91177308-0d34-0410-b5e6-96231b3b80d8
1688 lines
56 KiB
C++
1688 lines
56 KiB
C++
//===- LoopIndexSplit.cpp - Loop Index Splitting Pass ---------------------===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file is distributed under the University of Illinois Open Source
|
|
// License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This file implements Loop Index Splitting Pass.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#define DEBUG_TYPE "loop-index-split"
|
|
|
|
#include "llvm/Transforms/Scalar.h"
|
|
#include "llvm/Analysis/LoopPass.h"
|
|
#include "llvm/Analysis/ScalarEvolutionExpander.h"
|
|
#include "llvm/Analysis/Dominators.h"
|
|
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
|
|
#include "llvm/Transforms/Utils/Cloning.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");
|
|
|
|
namespace {
|
|
|
|
class VISIBILITY_HIDDEN LoopIndexSplit : public LoopPass {
|
|
|
|
public:
|
|
static char ID; // Pass ID, replacement for typeid
|
|
LoopIndexSplit() : LoopPass((intptr_t)&ID) {}
|
|
|
|
// Index split Loop L. Return true if loop is split.
|
|
bool runOnLoop(Loop *L, LPPassManager &LPM);
|
|
|
|
void getAnalysisUsage(AnalysisUsage &AU) const {
|
|
AU.addRequired<ScalarEvolution>();
|
|
AU.addPreserved<ScalarEvolution>();
|
|
AU.addRequiredID(LCSSAID);
|
|
AU.addPreservedID(LCSSAID);
|
|
AU.addRequired<LoopInfo>();
|
|
AU.addPreserved<LoopInfo>();
|
|
AU.addRequiredID(LoopSimplifyID);
|
|
AU.addPreservedID(LoopSimplifyID);
|
|
AU.addRequired<DominatorTree>();
|
|
AU.addRequired<DominanceFrontier>();
|
|
AU.addPreserved<DominatorTree>();
|
|
AU.addPreserved<DominanceFrontier>();
|
|
}
|
|
|
|
private:
|
|
|
|
class SplitInfo {
|
|
public:
|
|
SplitInfo() : SplitValue(NULL), SplitCondition(NULL),
|
|
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();
|
|
|
|
/// Find loop's exit condition.
|
|
void findLoopConditionals();
|
|
|
|
/// Return induction variable associated with value V.
|
|
void findIndVar(Value *V, Loop *L);
|
|
|
|
/// processOneIterationLoop - Current loop L contains compare instruction
|
|
/// that compares induction variable, IndVar, agains loop invariant. If
|
|
/// entire (i.e. meaningful) loop body is dominated by this compare
|
|
/// instruction then loop body is executed only for one iteration. In
|
|
/// such case eliminate loop structure surrounding this loop body. For
|
|
bool processOneIterationLoop(SplitInfo &SD);
|
|
|
|
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.
|
|
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);
|
|
|
|
/// updatePHINodes - CFG has been changed.
|
|
/// Before
|
|
/// - ExitBB's single predecessor was Latch
|
|
/// - Latch's second successor was Header
|
|
/// Now
|
|
/// - ExitBB's single predecessor was Header
|
|
/// - Latch's one and only successor was Header
|
|
///
|
|
/// Update ExitBB PHINodes' to reflect this change.
|
|
void updatePHINodes(BasicBlock *ExitBB, BasicBlock *Latch,
|
|
BasicBlock *Header,
|
|
PHINode *IV, Instruction *IVIncrement, Loop *LP);
|
|
|
|
/// moveExitCondition - Move exit condition EC into split condition block CondBB.
|
|
void moveExitCondition(BasicBlock *CondBB, BasicBlock *ActiveBB,
|
|
BasicBlock *ExitBB, ICmpInst *EC, ICmpInst *SC,
|
|
PHINode *IV, Instruction *IVAdd, Loop *LP);
|
|
|
|
/// splitLoop - Split current loop L in two loops using split information
|
|
/// SD. Update dominator information. Maintain LCSSA form.
|
|
bool splitLoop(SplitInfo &SD);
|
|
|
|
void initialize() {
|
|
IndVar = NULL;
|
|
IndVarIncrement = NULL;
|
|
ExitCondition = NULL;
|
|
StartValue = NULL;
|
|
ExitValueNum = 0;
|
|
SplitData.clear();
|
|
}
|
|
|
|
private:
|
|
|
|
// Current Loop.
|
|
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;
|
|
};
|
|
|
|
char LoopIndexSplit::ID = 0;
|
|
RegisterPass<LoopIndexSplit> X ("loop-index-split", "Index Split Loops");
|
|
}
|
|
|
|
LoopPass *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;
|
|
|
|
// FIXME - Nested loops make dominator info updates tricky.
|
|
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(),
|
|
E = SplitData.end(); SI != E;) {
|
|
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 (CI && CI->getPredicate() == ICmpInst::ICMP_EQ) {
|
|
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;
|
|
}
|
|
|
|
/// 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;
|
|
}
|
|
|
|
if (PHINode *PN = dyn_cast<PHINode>(Op1))
|
|
if (PN->getParent() == L->getHeader())
|
|
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op0))
|
|
if (CI->isOne()) {
|
|
IndVar = PN;
|
|
IndVarIncrement = I;
|
|
return;
|
|
}
|
|
|
|
return;
|
|
}
|
|
|
|
// Find loop's exit condition and associated induction variable.
|
|
void LoopIndexSplit::findLoopConditionals() {
|
|
|
|
BasicBlock *ExitingBlock = NULL;
|
|
|
|
for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
|
|
I != E; ++I) {
|
|
BasicBlock *BB = *I;
|
|
if (!L->isLoopExit(BB))
|
|
continue;
|
|
if (ExitingBlock)
|
|
return;
|
|
ExitingBlock = BB;
|
|
}
|
|
|
|
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);
|
|
}
|
|
}
|
|
|
|
/// 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 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 (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 (CI->getPredicate() == ICmpInst::ICMP_NE)
|
|
continue;
|
|
|
|
// If split condition predicate is GT or GE then first execute
|
|
// false branch of split condition.
|
|
if (CI->getPredicate() == ICmpInst::ICMP_UGT
|
|
|| CI->getPredicate() == ICmpInst::ICMP_SGT
|
|
|| CI->getPredicate() == ICmpInst::ICMP_UGE
|
|
|| CI->getPredicate() == ICmpInst::ICMP_SGE)
|
|
SD.UseTrueBranchFirst = false;
|
|
|
|
// If one operand is loop invariant and second operand is SCEVAddRecExpr
|
|
// based on induction variable then CI is a candidate split condition.
|
|
if (safeICmpInst(CI, SD))
|
|
SplitData.push_back(SD);
|
|
}
|
|
}
|
|
|
|
// safeIcmpInst - CI is considered safe instruction if one of the operand
|
|
// is SCEVAddRecExpr based on induction variable and other operand is
|
|
// loop invariant. If CI is safe then populate SplitInfo object SD appropriately
|
|
// and return true;
|
|
bool LoopIndexSplit::safeICmpInst(ICmpInst *CI, SplitInfo &SD) {
|
|
|
|
Value *V0 = CI->getOperand(0);
|
|
Value *V1 = CI->getOperand(1);
|
|
|
|
SCEVHandle SH0 = SE->getSCEV(V0);
|
|
SCEVHandle SH1 = SE->getSCEV(V1);
|
|
|
|
if (SH0->isLoopInvariant(L) && isa<SCEVAddRecExpr>(SH1)) {
|
|
SD.SplitValue = V0;
|
|
SD.SplitCondition = CI;
|
|
if (PHINode *PN = dyn_cast<PHINode>(V1)) {
|
|
if (PN == IndVar)
|
|
return true;
|
|
}
|
|
else if (Instruction *Insn = dyn_cast<Instruction>(V1)) {
|
|
if (IndVarIncrement && IndVarIncrement == Insn)
|
|
return true;
|
|
}
|
|
}
|
|
else if (SH1->isLoopInvariant(L) && isa<SCEVAddRecExpr>(SH0)) {
|
|
SD.SplitValue = V1;
|
|
SD.SplitCondition = CI;
|
|
if (PHINode *PN = dyn_cast<PHINode>(V0)) {
|
|
if (PN == IndVar)
|
|
return true;
|
|
}
|
|
else if (Instruction *Insn = dyn_cast<Instruction>(V0)) {
|
|
if (IndVarIncrement && IndVarIncrement == Insn)
|
|
return true;
|
|
}
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
/// processOneIterationLoop - Current loop L contains compare instruction
|
|
/// 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) {
|
|
|
|
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))
|
|
return false;
|
|
|
|
// If Exiting block includes loop variant instructions then this
|
|
// loop may not be eliminated.
|
|
if (!safeExitingBlock(SD, ExitCondition->getParent()))
|
|
return false;
|
|
|
|
// Filter loops where split condition's false branch is not empty.
|
|
if (ExitCondition->getParent() != Header->getTerminator()->getSuccessor(1))
|
|
return false;
|
|
|
|
// If split condition is not safe then do not process this loop.
|
|
// For example,
|
|
// for(int i = 0; i < N; i++) {
|
|
// if ( i == XYZ) {
|
|
// A;
|
|
// else
|
|
// B;
|
|
// }
|
|
// C;
|
|
// D;
|
|
// }
|
|
if (!safeSplitCondition(SD))
|
|
return false;
|
|
|
|
BasicBlock *Latch = L->getLoopLatch();
|
|
BranchInst *BR = dyn_cast<BranchInst>(Latch->getTerminator());
|
|
if (!BR)
|
|
return false;
|
|
|
|
// Update CFG.
|
|
|
|
// Replace index variable with split value in loop body. Loop body is executed
|
|
// 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);
|
|
|
|
// Replace split condition in header.
|
|
// Transform
|
|
// SplitCondition : icmp eq i32 IndVar, SplitValue
|
|
// into
|
|
// 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 ?
|
|
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;
|
|
|
|
if (I == IndVarIncrement)
|
|
I->replaceAllUsesWith(ExitValue);
|
|
else
|
|
I->replaceAllUsesWith(UndefValue::get(I->getType()));
|
|
I->eraseFromParent();
|
|
}
|
|
|
|
LPM->deleteLoopFromQueue(L);
|
|
|
|
// Update Dominator Info.
|
|
// Only CFG change done is to remove Latch to Header edge. This
|
|
// does not change dominator tree because Latch did not dominate
|
|
// Header.
|
|
if (DF) {
|
|
DominanceFrontier::iterator HeaderDF = DF->find(Header);
|
|
if (HeaderDF != DF->end())
|
|
DF->removeFromFrontier(HeaderDF, Header);
|
|
|
|
DominanceFrontier::iterator LatchDF = DF->find(Latch);
|
|
if (LatchDF != DF->end())
|
|
DF->removeFromFrontier(LatchDF, Header);
|
|
}
|
|
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;
|
|
|
|
// 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;
|
|
}
|
|
|
|
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;
|
|
|
|
// Induction variable increment is OK.
|
|
if (IndVarIncrement && IndVarIncrement == I)
|
|
continue;
|
|
|
|
// 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;
|
|
|
|
// Otherwise we have instruction that may not be safe.
|
|
return false;
|
|
}
|
|
|
|
// We could not find any reason to consider ExitingBlock unsafe.
|
|
return true;
|
|
}
|
|
|
|
void LoopIndexSplit::updateLoopBounds(ICmpInst *CI) {
|
|
|
|
Value *V0 = CI->getOperand(0);
|
|
Value *V1 = CI->getOperand(1);
|
|
Value *NV = NULL;
|
|
|
|
SCEVHandle SH0 = SE->getSCEV(V0);
|
|
|
|
if (SH0->isLoopInvariant(L))
|
|
NV = V0;
|
|
else
|
|
NV = V1;
|
|
|
|
if (ExitCondition->getPredicate() == ICmpInst::ICMP_SGT
|
|
|| ExitCondition->getPredicate() == ICmpInst::ICMP_UGT
|
|
|| ExitCondition->getPredicate() == ICmpInst::ICMP_SGE
|
|
|| ExitCondition->getPredicate() == ICmpInst::ICMP_UGE) {
|
|
ExitCondition->swapOperands();
|
|
if (ExitValueNum)
|
|
ExitValueNum = 0;
|
|
else
|
|
ExitValueNum = 1;
|
|
}
|
|
|
|
Value *NUB = NULL;
|
|
Value *NLB = NULL;
|
|
Value *UB = ExitCondition->getOperand(ExitValueNum);
|
|
const Type *Ty = NV->getType();
|
|
bool Sign = ExitCondition->isSignedPredicate();
|
|
BasicBlock *Preheader = L->getLoopPreheader();
|
|
Instruction *PHTerminator = Preheader->getTerminator();
|
|
|
|
assert (NV && "Unexpected value");
|
|
|
|
switch (CI->getPredicate()) {
|
|
case ICmpInst::ICMP_ULE:
|
|
case ICmpInst::ICMP_SLE:
|
|
// for (i = LB; i < UB; ++i)
|
|
// if (i <= NV && ...)
|
|
// LOOP_BODY
|
|
//
|
|
// is transformed into
|
|
// NUB = min (NV+1, UB)
|
|
// for (i = LB; i < NUB ; ++i)
|
|
// LOOP_BODY
|
|
//
|
|
if (ExitCondition->getPredicate() == ICmpInst::ICMP_SLT
|
|
|| ExitCondition->getPredicate() == ICmpInst::ICMP_ULT) {
|
|
Value *A = BinaryOperator::createAdd(NV, ConstantInt::get(Ty, 1, Sign),
|
|
"lsplit.add", PHTerminator);
|
|
Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
|
|
A, UB,"lsplit,c", PHTerminator);
|
|
NUB = new SelectInst (C, A, UB, "lsplit.nub", PHTerminator);
|
|
}
|
|
|
|
// for (i = LB; i <= UB; ++i)
|
|
// if (i <= NV && ...)
|
|
// LOOP_BODY
|
|
//
|
|
// is transformed into
|
|
// NUB = min (NV, UB)
|
|
// for (i = LB; i <= NUB ; ++i)
|
|
// LOOP_BODY
|
|
//
|
|
else if (ExitCondition->getPredicate() == ICmpInst::ICMP_SLE
|
|
|| ExitCondition->getPredicate() == ICmpInst::ICMP_ULE) {
|
|
Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
|
|
NV, UB, "lsplit.c", PHTerminator);
|
|
NUB = new SelectInst (C, NV, UB, "lsplit.nub", PHTerminator);
|
|
}
|
|
break;
|
|
case ICmpInst::ICMP_ULT:
|
|
case ICmpInst::ICMP_SLT:
|
|
// for (i = LB; i < UB; ++i)
|
|
// if (i < NV && ...)
|
|
// LOOP_BODY
|
|
//
|
|
// is transformed into
|
|
// NUB = min (NV, UB)
|
|
// for (i = LB; i < NUB ; ++i)
|
|
// LOOP_BODY
|
|
//
|
|
if (ExitCondition->getPredicate() == ICmpInst::ICMP_SLT
|
|
|| ExitCondition->getPredicate() == ICmpInst::ICMP_ULT) {
|
|
Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
|
|
NV, UB, "lsplit.c", PHTerminator);
|
|
NUB = new SelectInst (C, NV, UB, "lsplit.nub", PHTerminator);
|
|
}
|
|
|
|
// for (i = LB; i <= UB; ++i)
|
|
// if (i < NV && ...)
|
|
// LOOP_BODY
|
|
//
|
|
// is transformed into
|
|
// NUB = min (NV -1 , UB)
|
|
// for (i = LB; i <= NUB ; ++i)
|
|
// LOOP_BODY
|
|
//
|
|
else if (ExitCondition->getPredicate() == ICmpInst::ICMP_SLE
|
|
|| ExitCondition->getPredicate() == ICmpInst::ICMP_ULE) {
|
|
Value *S = BinaryOperator::createSub(NV, ConstantInt::get(Ty, 1, Sign),
|
|
"lsplit.add", PHTerminator);
|
|
Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
|
|
S, UB, "lsplit.c", PHTerminator);
|
|
NUB = new SelectInst (C, S, UB, "lsplit.nub", PHTerminator);
|
|
}
|
|
break;
|
|
case ICmpInst::ICMP_UGE:
|
|
case ICmpInst::ICMP_SGE:
|
|
// for (i = LB; i (< or <=) UB; ++i)
|
|
// if (i >= NV && ...)
|
|
// LOOP_BODY
|
|
//
|
|
// is transformed into
|
|
// NLB = max (NV, LB)
|
|
// for (i = NLB; i (< or <=) UB ; ++i)
|
|
// LOOP_BODY
|
|
//
|
|
{
|
|
Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
|
|
NV, StartValue, "lsplit.c", PHTerminator);
|
|
NLB = new SelectInst (C, StartValue, NV, "lsplit.nlb", PHTerminator);
|
|
}
|
|
break;
|
|
case ICmpInst::ICMP_UGT:
|
|
case ICmpInst::ICMP_SGT:
|
|
// for (i = LB; i (< or <=) UB; ++i)
|
|
// if (i > NV && ...)
|
|
// LOOP_BODY
|
|
//
|
|
// is transformed into
|
|
// NLB = max (NV+1, LB)
|
|
// for (i = NLB; i (< or <=) UB ; ++i)
|
|
// LOOP_BODY
|
|
//
|
|
{
|
|
Value *A = BinaryOperator::createAdd(NV, ConstantInt::get(Ty, 1, Sign),
|
|
"lsplit.add", PHTerminator);
|
|
Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
|
|
A, StartValue, "lsplit.c", PHTerminator);
|
|
NLB = new SelectInst (C, StartValue, A, "lsplit.nlb", PHTerminator);
|
|
}
|
|
break;
|
|
default:
|
|
assert ( 0 && "Unexpected split condition predicate");
|
|
}
|
|
|
|
if (NLB) {
|
|
unsigned i = IndVar->getBasicBlockIndex(Preheader);
|
|
IndVar->setIncomingValue(i, NLB);
|
|
}
|
|
|
|
if (NUB) {
|
|
ExitCondition->setOperand(ExitValueNum, NUB);
|
|
}
|
|
}
|
|
/// updateLoopIterationSpace - Current loop body is covered by an AND
|
|
/// instruction whose operands compares induction variables with loop
|
|
/// invariants. If possible, hoist this check outside the loop by
|
|
/// updating appropriate start and end values for induction variable.
|
|
bool LoopIndexSplit::updateLoopIterationSpace(SplitInfo &SD) {
|
|
BasicBlock *Header = L->getHeader();
|
|
BasicBlock *ExitingBlock = ExitCondition->getParent();
|
|
BasicBlock *SplitCondBlock = SD.SplitCondition->getParent();
|
|
|
|
ICmpInst *Op0 = cast<ICmpInst>(SD.SplitCondition->getOperand(0));
|
|
ICmpInst *Op1 = cast<ICmpInst>(SD.SplitCondition->getOperand(1));
|
|
|
|
if (Op0->getPredicate() == ICmpInst::ICMP_EQ
|
|
|| Op0->getPredicate() == ICmpInst::ICMP_NE
|
|
|| Op0->getPredicate() == ICmpInst::ICMP_EQ
|
|
|| Op0->getPredicate() == ICmpInst::ICMP_NE)
|
|
return false;
|
|
|
|
// Check if SplitCondition dominates entire loop body
|
|
// or not.
|
|
|
|
// If SplitCondition is not in loop header then this loop is not suitable
|
|
// for this transformation.
|
|
if (SD.SplitCondition->getParent() != Header)
|
|
return false;
|
|
|
|
// If loop header includes loop variant instruction operands then
|
|
// this loop may not be eliminated.
|
|
Instruction *Terminator = Header->getTerminator();
|
|
for(BasicBlock::iterator BI = Header->begin(), BE = Header->end();
|
|
BI != BE; ++BI) {
|
|
Instruction *I = BI;
|
|
|
|
// PHI Nodes are OK.
|
|
if (isa<PHINode>(I))
|
|
continue;
|
|
|
|
// SplitCondition itself is OK.
|
|
if (I == SD.SplitCondition)
|
|
continue;
|
|
if (I == Op0 || I == Op1)
|
|
continue;
|
|
|
|
// Induction variable is OK.
|
|
if (I == IndVar)
|
|
continue;
|
|
|
|
// Induction variable increment is OK.
|
|
if (I == IndVarIncrement)
|
|
continue;
|
|
|
|
// Terminator is also harmless.
|
|
if (I == Terminator)
|
|
continue;
|
|
|
|
// Otherwise we have a instruction that may not be safe.
|
|
return false;
|
|
}
|
|
|
|
// If Exiting block includes loop variant instructions then this
|
|
// loop may not be eliminated.
|
|
if (!safeExitingBlock(SD, ExitCondition->getParent()))
|
|
return false;
|
|
|
|
// Verify that loop exiting block has only two predecessor, where one predecessor
|
|
// is split condition block. The other predecessor will become exiting block's
|
|
// dominator after CFG is updated. TODO : Handle CFG's where exiting block has
|
|
// more then two predecessors. This requires extra work in updating dominator
|
|
// information.
|
|
BasicBlock *ExitingBBPred = NULL;
|
|
for (pred_iterator PI = pred_begin(ExitingBlock), PE = pred_end(ExitingBlock);
|
|
PI != PE; ++PI) {
|
|
BasicBlock *BB = *PI;
|
|
if (SplitCondBlock == BB)
|
|
continue;
|
|
if (ExitingBBPred)
|
|
return false;
|
|
else
|
|
ExitingBBPred = BB;
|
|
}
|
|
|
|
// Update loop bounds to absorb Op0 check.
|
|
updateLoopBounds(Op0);
|
|
// Update loop bounds to absorb Op1 check.
|
|
updateLoopBounds(Op1);
|
|
|
|
// Update CFG
|
|
|
|
// Unconditionally connect split block to its remaining successor.
|
|
BranchInst *SplitTerminator =
|
|
cast<BranchInst>(SplitCondBlock->getTerminator());
|
|
BasicBlock *Succ0 = SplitTerminator->getSuccessor(0);
|
|
BasicBlock *Succ1 = SplitTerminator->getSuccessor(1);
|
|
if (Succ0 == ExitCondition->getParent())
|
|
SplitTerminator->setUnconditionalDest(Succ1);
|
|
else
|
|
SplitTerminator->setUnconditionalDest(Succ0);
|
|
|
|
// Remove split condition.
|
|
SD.SplitCondition->eraseFromParent();
|
|
if (Op0->use_begin() == Op0->use_end())
|
|
Op0->eraseFromParent();
|
|
if (Op1->use_begin() == Op1->use_end())
|
|
Op1->eraseFromParent();
|
|
|
|
BranchInst *ExitInsn =
|
|
dyn_cast<BranchInst>(ExitingBlock->getTerminator());
|
|
assert (ExitInsn && "Unable to find suitable loop exit branch");
|
|
BasicBlock *ExitBlock = ExitInsn->getSuccessor(1);
|
|
if (L->contains(ExitBlock))
|
|
ExitBlock = ExitInsn->getSuccessor(0);
|
|
|
|
// Update domiantor info. Now, ExitingBlock has only one predecessor,
|
|
// ExitingBBPred, and it is ExitingBlock's immediate domiantor.
|
|
DT->changeImmediateDominator(ExitingBlock, ExitingBBPred);
|
|
|
|
// If ExitingBlock is a member of loop BB's DF list then replace it with
|
|
// loop header and exit block.
|
|
for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
|
|
I != E; ++I) {
|
|
BasicBlock *BB = *I;
|
|
if (BB == Header || BB == ExitingBlock)
|
|
continue;
|
|
DominanceFrontier::iterator BBDF = DF->find(BB);
|
|
DominanceFrontier::DomSetType::iterator DomSetI = BBDF->second.begin();
|
|
DominanceFrontier::DomSetType::iterator DomSetE = BBDF->second.end();
|
|
while (DomSetI != DomSetE) {
|
|
DominanceFrontier::DomSetType::iterator CurrentItr = DomSetI;
|
|
++DomSetI;
|
|
BasicBlock *DFBB = *CurrentItr;
|
|
if (DFBB == ExitingBlock) {
|
|
BBDF->second.erase(DFBB);
|
|
BBDF->second.insert(Header);
|
|
if (Header != ExitingBlock)
|
|
BBDF->second.insert(ExitBlock);
|
|
}
|
|
}
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
|
|
/// removeBlocks - Remove basic block DeadBB and all blocks dominated by DeadBB.
|
|
/// This routine is used to remove split condition's dead branch, dominated by
|
|
/// DeadBB. LiveBB dominates split conidition's other branch.
|
|
void LoopIndexSplit::removeBlocks(BasicBlock *DeadBB, Loop *LP,
|
|
BasicBlock *LiveBB) {
|
|
|
|
// First update DeadBB's dominance frontier.
|
|
SmallVector<BasicBlock *, 8> FrontierBBs;
|
|
DominanceFrontier::iterator DeadBBDF = DF->find(DeadBB);
|
|
if (DeadBBDF != DF->end()) {
|
|
SmallVector<BasicBlock *, 8> PredBlocks;
|
|
|
|
DominanceFrontier::DomSetType DeadBBSet = DeadBBDF->second;
|
|
for (DominanceFrontier::DomSetType::iterator DeadBBSetI = DeadBBSet.begin(),
|
|
DeadBBSetE = DeadBBSet.end(); DeadBBSetI != DeadBBSetE; ++DeadBBSetI) {
|
|
BasicBlock *FrontierBB = *DeadBBSetI;
|
|
FrontierBBs.push_back(FrontierBB);
|
|
|
|
// Rremove any PHI incoming edge from blocks dominated by DeadBB.
|
|
PredBlocks.clear();
|
|
for(pred_iterator PI = pred_begin(FrontierBB), PE = pred_end(FrontierBB);
|
|
PI != PE; ++PI) {
|
|
BasicBlock *P = *PI;
|
|
if (P == DeadBB || DT->dominates(DeadBB, P))
|
|
PredBlocks.push_back(P);
|
|
}
|
|
|
|
for(BasicBlock::iterator FBI = FrontierBB->begin(), FBE = FrontierBB->end();
|
|
FBI != FBE; ++FBI) {
|
|
if (PHINode *PN = dyn_cast<PHINode>(FBI)) {
|
|
for(SmallVector<BasicBlock *, 8>::iterator PI = PredBlocks.begin(),
|
|
PE = PredBlocks.end(); PI != PE; ++PI) {
|
|
BasicBlock *P = *PI;
|
|
PN->removeIncomingValue(P);
|
|
}
|
|
}
|
|
else
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
// Now remove DeadBB and all nodes dominated by DeadBB in df order.
|
|
SmallVector<BasicBlock *, 32> WorkList;
|
|
DomTreeNode *DN = DT->getNode(DeadBB);
|
|
for (df_iterator<DomTreeNode*> DI = df_begin(DN),
|
|
E = df_end(DN); DI != E; ++DI) {
|
|
BasicBlock *BB = DI->getBlock();
|
|
WorkList.push_back(BB);
|
|
BB->replaceAllUsesWith(UndefValue::get(Type::LabelTy));
|
|
}
|
|
|
|
while (!WorkList.empty()) {
|
|
BasicBlock *BB = WorkList.back(); WorkList.pop_back();
|
|
for(BasicBlock::iterator BBI = BB->begin(), BBE = BB->end();
|
|
BBI != BBE; ) {
|
|
Instruction *I = BBI;
|
|
++BBI;
|
|
I->replaceAllUsesWith(UndefValue::get(I->getType()));
|
|
I->eraseFromParent();
|
|
}
|
|
LPM->deleteSimpleAnalysisValue(BB, LP);
|
|
DT->eraseNode(BB);
|
|
DF->removeBlock(BB);
|
|
LI->removeBlock(BB);
|
|
BB->eraseFromParent();
|
|
}
|
|
|
|
// Update Frontier BBs' dominator info.
|
|
while (!FrontierBBs.empty()) {
|
|
BasicBlock *FBB = FrontierBBs.back(); FrontierBBs.pop_back();
|
|
BasicBlock *NewDominator = FBB->getSinglePredecessor();
|
|
if (!NewDominator) {
|
|
pred_iterator PI = pred_begin(FBB), PE = pred_end(FBB);
|
|
NewDominator = *PI;
|
|
++PI;
|
|
if (NewDominator != LiveBB) {
|
|
for(; PI != PE; ++PI) {
|
|
BasicBlock *P = *PI;
|
|
if (P == LiveBB) {
|
|
NewDominator = LiveBB;
|
|
break;
|
|
}
|
|
NewDominator = DT->findNearestCommonDominator(NewDominator, P);
|
|
}
|
|
}
|
|
}
|
|
assert (NewDominator && "Unable to fix dominator info.");
|
|
DT->changeImmediateDominator(FBB, NewDominator);
|
|
DF->changeImmediateDominator(FBB, NewDominator, DT);
|
|
}
|
|
|
|
}
|
|
|
|
/// safeSplitCondition - Return true if it is possible to
|
|
/// split loop using given split condition.
|
|
bool LoopIndexSplit::safeSplitCondition(SplitInfo &SD) {
|
|
|
|
BasicBlock *SplitCondBlock = SD.SplitCondition->getParent();
|
|
BasicBlock *Latch = L->getLoopLatch();
|
|
BranchInst *SplitTerminator =
|
|
cast<BranchInst>(SplitCondBlock->getTerminator());
|
|
BasicBlock *Succ0 = SplitTerminator->getSuccessor(0);
|
|
BasicBlock *Succ1 = SplitTerminator->getSuccessor(1);
|
|
|
|
// Finally this split condition is safe only if merge point for
|
|
// split condition branch is loop latch. This check along with previous
|
|
// check, to ensure that exit condition is in either loop latch or header,
|
|
// filters all loops with non-empty loop body between merge point
|
|
// and exit condition.
|
|
DominanceFrontier::iterator Succ0DF = DF->find(Succ0);
|
|
assert (Succ0DF != DF->end() && "Unable to find Succ0 dominance frontier");
|
|
if (Succ0DF->second.count(Latch))
|
|
return true;
|
|
|
|
DominanceFrontier::iterator Succ1DF = DF->find(Succ1);
|
|
assert (Succ1DF != DF->end() && "Unable to find Succ1 dominance frontier");
|
|
if (Succ1DF->second.count(Latch))
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
/// calculateLoopBounds - ALoop exit value and BLoop start values are calculated
|
|
/// based on split value.
|
|
void LoopIndexSplit::calculateLoopBounds(SplitInfo &SD) {
|
|
|
|
ICmpInst *SC = cast<ICmpInst>(SD.SplitCondition);
|
|
ICmpInst::Predicate SP = SC->getPredicate();
|
|
const Type *Ty = SD.SplitValue->getType();
|
|
bool Sign = ExitCondition->isSignedPredicate();
|
|
BasicBlock *Preheader = L->getLoopPreheader();
|
|
Instruction *PHTerminator = Preheader->getTerminator();
|
|
|
|
// Initially use split value as upper loop bound for first loop and lower loop
|
|
// bound for second loop.
|
|
Value *AEV = SD.SplitValue;
|
|
Value *BSV = SD.SplitValue;
|
|
|
|
if (ExitCondition->getPredicate() == ICmpInst::ICMP_SGT
|
|
|| ExitCondition->getPredicate() == ICmpInst::ICMP_UGT
|
|
|| ExitCondition->getPredicate() == ICmpInst::ICMP_SGE
|
|
|| ExitCondition->getPredicate() == ICmpInst::ICMP_UGE) {
|
|
ExitCondition->swapOperands();
|
|
if (ExitValueNum)
|
|
ExitValueNum = 0;
|
|
else
|
|
ExitValueNum = 1;
|
|
}
|
|
|
|
switch (ExitCondition->getPredicate()) {
|
|
case ICmpInst::ICMP_SGT:
|
|
case ICmpInst::ICMP_UGT:
|
|
case ICmpInst::ICMP_SGE:
|
|
case ICmpInst::ICMP_UGE:
|
|
default:
|
|
assert (0 && "Unexpected exit condition predicate");
|
|
|
|
case ICmpInst::ICMP_SLT:
|
|
case ICmpInst::ICMP_ULT:
|
|
{
|
|
switch (SP) {
|
|
case ICmpInst::ICMP_SLT:
|
|
case ICmpInst::ICMP_ULT:
|
|
//
|
|
// for (i = LB; i < UB; ++i) { if (i < SV) A; else B; }
|
|
//
|
|
// is transformed into
|
|
// AEV = BSV = SV
|
|
// for (i = LB; i < min(UB, AEV); ++i)
|
|
// A;
|
|
// for (i = max(LB, BSV); i < UB; ++i);
|
|
// B;
|
|
break;
|
|
case ICmpInst::ICMP_SLE:
|
|
case ICmpInst::ICMP_ULE:
|
|
{
|
|
//
|
|
// for (i = LB; i < UB; ++i) { if (i <= SV) A; else B; }
|
|
//
|
|
// is transformed into
|
|
//
|
|
// AEV = SV + 1
|
|
// BSV = SV + 1
|
|
// for (i = LB; i < min(UB, AEV); ++i)
|
|
// A;
|
|
// for (i = max(LB, BSV); i < UB; ++i)
|
|
// B;
|
|
BSV = BinaryOperator::createAdd(SD.SplitValue,
|
|
ConstantInt::get(Ty, 1, Sign),
|
|
"lsplit.add", PHTerminator);
|
|
AEV = BSV;
|
|
}
|
|
break;
|
|
case ICmpInst::ICMP_SGE:
|
|
case ICmpInst::ICMP_UGE:
|
|
//
|
|
// for (i = LB; i < UB; ++i) { if (i >= SV) A; else B; }
|
|
//
|
|
// is transformed into
|
|
// AEV = BSV = SV
|
|
// for (i = LB; i < min(UB, AEV); ++i)
|
|
// B;
|
|
// for (i = max(BSV, LB); i < UB; ++i)
|
|
// A;
|
|
break;
|
|
case ICmpInst::ICMP_SGT:
|
|
case ICmpInst::ICMP_UGT:
|
|
{
|
|
//
|
|
// for (i = LB; i < UB; ++i) { if (i > SV) A; else B; }
|
|
//
|
|
// is transformed into
|
|
//
|
|
// BSV = AEV = SV + 1
|
|
// for (i = LB; i < min(UB, AEV); ++i)
|
|
// B;
|
|
// for (i = max(LB, BSV); i < UB; ++i)
|
|
// A;
|
|
BSV = BinaryOperator::createAdd(SD.SplitValue,
|
|
ConstantInt::get(Ty, 1, Sign),
|
|
"lsplit.add", PHTerminator);
|
|
AEV = BSV;
|
|
}
|
|
break;
|
|
default:
|
|
assert (0 && "Unexpected split condition predicate");
|
|
break;
|
|
} // end switch (SP)
|
|
}
|
|
break;
|
|
case ICmpInst::ICMP_SLE:
|
|
case ICmpInst::ICMP_ULE:
|
|
{
|
|
switch (SP) {
|
|
case ICmpInst::ICMP_SLT:
|
|
case ICmpInst::ICMP_ULT:
|
|
//
|
|
// for (i = LB; i <= UB; ++i) { if (i < SV) A; else B; }
|
|
//
|
|
// is transformed into
|
|
// AEV = SV - 1;
|
|
// BSV = SV;
|
|
// for (i = LB; i <= min(UB, AEV); ++i)
|
|
// A;
|
|
// for (i = max(LB, BSV); i <= UB; ++i)
|
|
// B;
|
|
AEV = BinaryOperator::createSub(SD.SplitValue,
|
|
ConstantInt::get(Ty, 1, Sign),
|
|
"lsplit.sub", PHTerminator);
|
|
break;
|
|
case ICmpInst::ICMP_SLE:
|
|
case ICmpInst::ICMP_ULE:
|
|
//
|
|
// for (i = LB; i <= UB; ++i) { if (i <= SV) A; else B; }
|
|
//
|
|
// is transformed into
|
|
// AEV = SV;
|
|
// BSV = SV + 1;
|
|
// for (i = LB; i <= min(UB, AEV); ++i)
|
|
// A;
|
|
// for (i = max(LB, BSV); i <= UB; ++i)
|
|
// B;
|
|
BSV = BinaryOperator::createAdd(SD.SplitValue,
|
|
ConstantInt::get(Ty, 1, Sign),
|
|
"lsplit.add", PHTerminator);
|
|
break;
|
|
case ICmpInst::ICMP_SGT:
|
|
case ICmpInst::ICMP_UGT:
|
|
//
|
|
// for (i = LB; i <= UB; ++i) { if (i > SV) A; else B; }
|
|
//
|
|
// is transformed into
|
|
// AEV = SV;
|
|
// BSV = SV + 1;
|
|
// for (i = LB; i <= min(AEV, UB); ++i)
|
|
// B;
|
|
// for (i = max(LB, BSV); i <= UB; ++i)
|
|
// A;
|
|
BSV = BinaryOperator::createAdd(SD.SplitValue,
|
|
ConstantInt::get(Ty, 1, Sign),
|
|
"lsplit.add", PHTerminator);
|
|
break;
|
|
case ICmpInst::ICMP_SGE:
|
|
case ICmpInst::ICMP_UGE:
|
|
// ** TODO **
|
|
//
|
|
// for (i = LB; i <= UB; ++i) { if (i >= SV) A; else B; }
|
|
//
|
|
// is transformed into
|
|
// AEV = SV - 1;
|
|
// BSV = SV;
|
|
// for (i = LB; i <= min(AEV, UB); ++i)
|
|
// B;
|
|
// for (i = max(LB, BSV); i <= UB; ++i)
|
|
// A;
|
|
AEV = BinaryOperator::createSub(SD.SplitValue,
|
|
ConstantInt::get(Ty, 1, Sign),
|
|
"lsplit.sub", PHTerminator);
|
|
break;
|
|
default:
|
|
assert (0 && "Unexpected split condition predicate");
|
|
break;
|
|
} // end switch (SP)
|
|
}
|
|
break;
|
|
}
|
|
|
|
// Calculate ALoop induction variable's new exiting value and
|
|
// BLoop induction variable's new starting value. Calculuate these
|
|
// values in original loop's preheader.
|
|
// A_ExitValue = min(SplitValue, OrignalLoopExitValue)
|
|
// B_StartValue = max(SplitValue, OriginalLoopStartValue)
|
|
Instruction *InsertPt = L->getHeader()->getFirstNonPHI();
|
|
|
|
// If ExitValue operand is also defined in Loop header then
|
|
// insert new ExitValue after this operand definition.
|
|
if (Instruction *EVN =
|
|
dyn_cast<Instruction>(ExitCondition->getOperand(ExitValueNum))) {
|
|
if (!isa<PHINode>(EVN))
|
|
if (InsertPt->getParent() == EVN->getParent()) {
|
|
BasicBlock::iterator LHBI = L->getHeader()->begin();
|
|
BasicBlock::iterator LHBE = L->getHeader()->end();
|
|
for(;LHBI != LHBE; ++LHBI) {
|
|
Instruction *I = LHBI;
|
|
if (I == EVN)
|
|
break;
|
|
}
|
|
InsertPt = ++LHBI;
|
|
}
|
|
}
|
|
Value *C1 = new ICmpInst(Sign ?
|
|
ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
|
|
AEV,
|
|
ExitCondition->getOperand(ExitValueNum),
|
|
"lsplit.ev", InsertPt);
|
|
|
|
SD.A_ExitValue = new SelectInst(C1, AEV,
|
|
ExitCondition->getOperand(ExitValueNum),
|
|
"lsplit.ev", InsertPt);
|
|
|
|
Value *C2 = new ICmpInst(Sign ?
|
|
ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
|
|
BSV, StartValue, "lsplit.sv",
|
|
PHTerminator);
|
|
SD.B_StartValue = new SelectInst(C2, StartValue, BSV,
|
|
"lsplit.sv", PHTerminator);
|
|
}
|
|
|
|
/// splitLoop - Split current loop L in two loops using split information
|
|
/// SD. Update dominator information. Maintain LCSSA form.
|
|
bool LoopIndexSplit::splitLoop(SplitInfo &SD) {
|
|
|
|
if (!safeSplitCondition(SD))
|
|
return false;
|
|
|
|
BasicBlock *SplitCondBlock = SD.SplitCondition->getParent();
|
|
|
|
// Unable to handle triange loops at the moment.
|
|
// In triangle loop, split condition is in header and one of the
|
|
// the split destination is loop latch. If split condition is EQ
|
|
// then such loops are already handle in processOneIterationLoop().
|
|
BasicBlock *Latch = L->getLoopLatch();
|
|
BranchInst *SplitTerminator =
|
|
cast<BranchInst>(SplitCondBlock->getTerminator());
|
|
BasicBlock *Succ0 = SplitTerminator->getSuccessor(0);
|
|
BasicBlock *Succ1 = SplitTerminator->getSuccessor(1);
|
|
if (L->getHeader() == SplitCondBlock
|
|
&& (Latch == Succ0 || Latch == Succ1))
|
|
return false;
|
|
|
|
// If split condition branches heads do not have single predecessor,
|
|
// SplitCondBlock, then is not possible to remove inactive branch.
|
|
if (!Succ0->getSinglePredecessor() || !Succ1->getSinglePredecessor())
|
|
return false;
|
|
|
|
// If Exiting block includes loop variant instructions then this
|
|
// loop may not be split safely.
|
|
if (!safeExitingBlock(SD, ExitCondition->getParent()))
|
|
return false;
|
|
|
|
// After loop is cloned there are two loops.
|
|
//
|
|
// First loop, referred as ALoop, executes first part of loop's iteration
|
|
// 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.
|
|
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 original exit block becomes BLoop's exit block.
|
|
PHINode *B_IndVar = cast<PHINode>(ValueMap[IndVar]);
|
|
BasicBlock *A_ExitingBlock = ExitCondition->getParent();
|
|
BranchInst *A_ExitInsn =
|
|
dyn_cast<BranchInst>(A_ExitingBlock->getTerminator());
|
|
assert (A_ExitInsn && "Unable to find suitable loop exit branch");
|
|
BasicBlock *B_ExitBlock = A_ExitInsn->getSuccessor(1);
|
|
if (L->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 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) {
|
|
if (PHINode *PN = dyn_cast<PHINode>(BI)) {
|
|
PHINode *PNClone = cast<PHINode>(ValueMap[PN]);
|
|
InverseMap[PNClone] = PN;
|
|
} else
|
|
break;
|
|
}
|
|
|
|
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);
|
|
|
|
// Add incoming value from A_ExitingBlock.
|
|
if (PN == B_IndVar)
|
|
PN->addIncoming(SD.B_StartValue, 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())
|
|
V2 = OrigPN;
|
|
else
|
|
V2 = OrigPN->getIncomingValueForBlock(A_ExitingBlock);
|
|
PN->addIncoming(V2, A_ExitingBlock);
|
|
}
|
|
} else
|
|
break;
|
|
}
|
|
DT->changeImmediateDominator(B_Header, A_ExitingBlock);
|
|
DF->changeImmediateDominator(B_Header, A_ExitingBlock, DT);
|
|
|
|
// [*] Update BLoop's exit block. Its new predecessor is BLoop's exit
|
|
// block. Remove incoming PHINode values from ALoop's exiting block.
|
|
// Add new incoming values from BLoop's incoming exiting value.
|
|
// Update BLoop exit block's dominator info..
|
|
BasicBlock *B_ExitingBlock = cast<BasicBlock>(ValueMap[A_ExitingBlock]);
|
|
for (BasicBlock::iterator BI = B_ExitBlock->begin(), BE = B_ExitBlock->end();
|
|
BI != BE; ++BI) {
|
|
if (PHINode *PN = dyn_cast<PHINode>(BI)) {
|
|
PN->addIncoming(ValueMap[PN->getIncomingValueForBlock(A_ExitingBlock)],
|
|
B_ExitingBlock);
|
|
PN->removeIncomingValue(A_ExitingBlock);
|
|
} else
|
|
break;
|
|
}
|
|
|
|
DT->changeImmediateDominator(B_ExitBlock, B_ExitingBlock);
|
|
DF->changeImmediateDominator(B_ExitBlock, B_ExitingBlock, DT);
|
|
|
|
//[*] Split ALoop's exit edge. This creates a new block which
|
|
// serves two purposes. First one is to hold PHINode defnitions
|
|
// to ensure that ALoop's LCSSA form. Second use it to act
|
|
// as a preheader for BLoop.
|
|
BasicBlock *A_ExitBlock = SplitEdge(A_ExitingBlock, B_Header, this);
|
|
|
|
//[*] Preserve ALoop's LCSSA form. Create new forwarding PHINodes
|
|
// in A_ExitBlock to redefine outgoing PHI definitions from ALoop.
|
|
for(BasicBlock::iterator BI = B_Header->begin(), BE = B_Header->end();
|
|
BI != BE; ++BI) {
|
|
if (PHINode *PN = dyn_cast<PHINode>(BI)) {
|
|
Value *V1 = PN->getIncomingValueForBlock(A_ExitBlock);
|
|
PHINode *newPHI = new PHINode(PN->getType(), PN->getName());
|
|
newPHI->addIncoming(V1, A_ExitingBlock);
|
|
A_ExitBlock->getInstList().push_front(newPHI);
|
|
PN->removeIncomingValue(A_ExitBlock);
|
|
PN->addIncoming(newPHI, A_ExitBlock);
|
|
} else
|
|
break;
|
|
}
|
|
|
|
//[*] Eliminate split condition's inactive branch from ALoop.
|
|
BasicBlock *A_SplitCondBlock = SD.SplitCondition->getParent();
|
|
BranchInst *A_BR = cast<BranchInst>(A_SplitCondBlock->getTerminator());
|
|
BasicBlock *A_InactiveBranch = NULL;
|
|
BasicBlock *A_ActiveBranch = NULL;
|
|
if (SD.UseTrueBranchFirst) {
|
|
A_ActiveBranch = A_BR->getSuccessor(0);
|
|
A_InactiveBranch = A_BR->getSuccessor(1);
|
|
} else {
|
|
A_ActiveBranch = A_BR->getSuccessor(1);
|
|
A_InactiveBranch = A_BR->getSuccessor(0);
|
|
}
|
|
A_BR->setUnconditionalDest(A_ActiveBranch);
|
|
removeBlocks(A_InactiveBranch, L, A_ActiveBranch);
|
|
|
|
//[*] Eliminate split condition's inactive branch in from BLoop.
|
|
BasicBlock *B_SplitCondBlock = cast<BasicBlock>(ValueMap[A_SplitCondBlock]);
|
|
BranchInst *B_BR = cast<BranchInst>(B_SplitCondBlock->getTerminator());
|
|
BasicBlock *B_InactiveBranch = NULL;
|
|
BasicBlock *B_ActiveBranch = NULL;
|
|
if (SD.UseTrueBranchFirst) {
|
|
B_ActiveBranch = B_BR->getSuccessor(1);
|
|
B_InactiveBranch = B_BR->getSuccessor(0);
|
|
} else {
|
|
B_ActiveBranch = B_BR->getSuccessor(0);
|
|
B_InactiveBranch = B_BR->getSuccessor(1);
|
|
}
|
|
B_BR->setUnconditionalDest(B_ActiveBranch);
|
|
removeBlocks(B_InactiveBranch, BLoop, B_ActiveBranch);
|
|
|
|
BasicBlock *A_Header = L->getHeader();
|
|
if (A_ExitingBlock == A_Header)
|
|
return true;
|
|
|
|
//[*] Move exit condition into split condition block to avoid
|
|
// executing dead loop iteration.
|
|
ICmpInst *B_ExitCondition = cast<ICmpInst>(ValueMap[ExitCondition]);
|
|
Instruction *B_IndVarIncrement = cast<Instruction>(ValueMap[IndVarIncrement]);
|
|
ICmpInst *B_SplitCondition = cast<ICmpInst>(ValueMap[SD.SplitCondition]);
|
|
|
|
moveExitCondition(A_SplitCondBlock, A_ActiveBranch, A_ExitBlock, ExitCondition,
|
|
cast<ICmpInst>(SD.SplitCondition), IndVar, IndVarIncrement,
|
|
ALoop);
|
|
|
|
moveExitCondition(B_SplitCondBlock, B_ActiveBranch, B_ExitBlock, B_ExitCondition,
|
|
B_SplitCondition, B_IndVar, B_IndVarIncrement, BLoop);
|
|
|
|
return true;
|
|
}
|
|
|
|
// moveExitCondition - Move exit condition EC into split condition block CondBB.
|
|
void LoopIndexSplit::moveExitCondition(BasicBlock *CondBB, BasicBlock *ActiveBB,
|
|
BasicBlock *ExitBB, ICmpInst *EC, ICmpInst *SC,
|
|
PHINode *IV, Instruction *IVAdd, Loop *LP) {
|
|
|
|
BasicBlock *ExitingBB = EC->getParent();
|
|
Instruction *CurrentBR = CondBB->getTerminator();
|
|
|
|
// Move exit condition into split condition block.
|
|
EC->moveBefore(CurrentBR);
|
|
EC->setOperand(ExitValueNum == 0 ? 1 : 0, IV);
|
|
|
|
// Move exiting block's branch into split condition block. Update its branch
|
|
// destination.
|
|
BranchInst *ExitingBR = cast<BranchInst>(ExitingBB->getTerminator());
|
|
ExitingBR->moveBefore(CurrentBR);
|
|
BasicBlock *OrigDestBB = NULL;
|
|
if (ExitingBR->getSuccessor(0) == ExitBB) {
|
|
OrigDestBB = ExitingBR->getSuccessor(1);
|
|
ExitingBR->setSuccessor(1, ActiveBB);
|
|
}
|
|
else {
|
|
OrigDestBB = ExitingBR->getSuccessor(0);
|
|
ExitingBR->setSuccessor(0, ActiveBB);
|
|
}
|
|
|
|
// Remove split condition and current split condition branch.
|
|
SC->eraseFromParent();
|
|
CurrentBR->eraseFromParent();
|
|
|
|
// Connect exiting block to original destination.
|
|
new BranchInst(OrigDestBB, ExitingBB);
|
|
|
|
// Update PHINodes
|
|
updatePHINodes(ExitBB, ExitingBB, CondBB, IV, IVAdd, LP);
|
|
|
|
// Fix dominator info.
|
|
// ExitBB is now dominated by CondBB
|
|
DT->changeImmediateDominator(ExitBB, CondBB);
|
|
DF->changeImmediateDominator(ExitBB, CondBB, DT);
|
|
|
|
// Basicblocks dominated by ActiveBB may have ExitingBB or
|
|
// a basic block outside the loop in their DF list. If so,
|
|
// replace it with CondBB.
|
|
DomTreeNode *Node = DT->getNode(ActiveBB);
|
|
for (df_iterator<DomTreeNode *> DI = df_begin(Node), DE = df_end(Node);
|
|
DI != DE; ++DI) {
|
|
BasicBlock *BB = DI->getBlock();
|
|
DominanceFrontier::iterator BBDF = DF->find(BB);
|
|
DominanceFrontier::DomSetType::iterator DomSetI = BBDF->second.begin();
|
|
DominanceFrontier::DomSetType::iterator DomSetE = BBDF->second.end();
|
|
while (DomSetI != DomSetE) {
|
|
DominanceFrontier::DomSetType::iterator CurrentItr = DomSetI;
|
|
++DomSetI;
|
|
BasicBlock *DFBB = *CurrentItr;
|
|
if (DFBB == ExitingBB || !L->contains(DFBB)) {
|
|
BBDF->second.erase(DFBB);
|
|
BBDF->second.insert(CondBB);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/// updatePHINodes - CFG has been changed.
|
|
/// Before
|
|
/// - ExitBB's single predecessor was Latch
|
|
/// - Latch's second successor was Header
|
|
/// Now
|
|
/// - ExitBB's single predecessor is Header
|
|
/// - Latch's one and only successor is Header
|
|
///
|
|
/// Update ExitBB PHINodes' to reflect this change.
|
|
void LoopIndexSplit::updatePHINodes(BasicBlock *ExitBB, BasicBlock *Latch,
|
|
BasicBlock *Header,
|
|
PHINode *IV, Instruction *IVIncrement,
|
|
Loop *LP) {
|
|
|
|
for (BasicBlock::iterator BI = ExitBB->begin(), BE = ExitBB->end();
|
|
BI != BE; ++BI) {
|
|
PHINode *PN = dyn_cast<PHINode>(BI);
|
|
if (!PN)
|
|
break;
|
|
|
|
Value *V = PN->getIncomingValueForBlock(Latch);
|
|
if (PHINode *PHV = dyn_cast<PHINode>(V)) {
|
|
// PHV is in Latch. PHV has one use is in ExitBB PHINode. And one use
|
|
// in Header which is new incoming value for PN.
|
|
Value *NewV = NULL;
|
|
for (Value::use_iterator UI = PHV->use_begin(), E = PHV->use_end();
|
|
UI != E; ++UI)
|
|
if (PHINode *U = dyn_cast<PHINode>(*UI))
|
|
if (LP->contains(U->getParent())) {
|
|
NewV = U;
|
|
break;
|
|
}
|
|
|
|
assert (NewV && "Unable to find new incoming value for exit block PHI");
|
|
PN->addIncoming(NewV, Header);
|
|
|
|
} else if (Instruction *PHI = dyn_cast<Instruction>(V)) {
|
|
// If this instruction is IVIncrement then IV is new incoming value
|
|
// from header otherwise this instruction must be incoming value from
|
|
// header because loop is in LCSSA form.
|
|
if (PHI == IVIncrement)
|
|
PN->addIncoming(IV, Header);
|
|
else
|
|
PN->addIncoming(V, Header);
|
|
} else
|
|
// Otherwise this is an incoming value from header because loop is in
|
|
// LCSSA form.
|
|
PN->addIncoming(V, Header);
|
|
|
|
// Remove incoming value from Latch.
|
|
PN->removeIncomingValue(Latch);
|
|
}
|
|
}
|