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Split loops and do CFG cleanup.
llvm-svn: 41029
This commit is contained in:
Devang Patel
parent
c71871ba30
commit
63d1affed8
@ -97,6 +97,9 @@ namespace {
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/// loop may not be eliminated.
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bool safeExitBlock(SplitInfo &SD, BasicBlock *BB);
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/// removeBlocks - Remove basic block BB and all blocks dominated by BB.
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void removeBlocks(BasicBlock *InBB);
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/// Find cost of spliting loop L.
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unsigned findSplitCost(Loop *L, SplitInfo &SD);
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bool splitLoop(SplitInfo &SD);
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@ -105,7 +108,9 @@ namespace {
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IndVar = NULL;
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IndVarIncrement = NULL;
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ExitCondition = NULL;
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StartValue = ExitValue = NULL;
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StartValue = NULL;
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ExitValueNum = 0;
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SplitData.clear();
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}
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private:
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@ -128,8 +133,8 @@ namespace {
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// Induction variable's initial value.
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Value *StartValue;
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// Induction variable's final loop exit value.
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Value *ExitValue;
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// Induction variable's final loop exit value operand number in exit condition..
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unsigned ExitValueNum;
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};
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char LoopIndexSplit::ID = 0;
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@ -285,15 +290,15 @@ void LoopIndexSplit::findLoopConditionals() {
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SCEVHandle SH1 = SE->getSCEV(V1);
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if (SH0->isLoopInvariant(L) && isa<SCEVAddRecExpr>(SH1)) {
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ExitValue = V0;
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ExitValueNum = 0;
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findIndVar(V1, L);
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}
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else if (SH1->isLoopInvariant(L) && isa<SCEVAddRecExpr>(SH0)) {
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ExitValue = V1;
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ExitValueNum = 1;
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findIndVar(V0, L);
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}
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if (!ExitValue || !IndVar)
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if (!IndVar)
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ExitCondition = NULL;
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else if (IndVar) {
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BasicBlock *Preheader = L->getLoopPreheader();
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@ -430,7 +435,8 @@ bool LoopIndexSplit::processOneIterationLoop(SplitInfo &SD) {
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Terminator);
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Instruction *C2 = new ICmpInst(SignedPredicate ?
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ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
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SD.SplitValue, ExitValue, "lisplit",
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SD.SplitValue,
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ExitCondition->getOperand(ExitValueNum), "lisplit",
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Terminator);
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Instruction *NSplitCond = BinaryOperator::createAnd(C1, C2, "lisplit",
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Terminator);
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@ -580,6 +586,45 @@ unsigned LoopIndexSplit::findSplitCost(Loop *L, SplitInfo &SD) {
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return Cost;
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}
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/// removeBlocks - Remove basic block BB and all blocks dominated by BB.
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void LoopIndexSplit::removeBlocks(BasicBlock *InBB) {
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SmallVector<BasicBlock *, 8> WorkList;
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WorkList.push_back(InBB);
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while (!WorkList.empty()) {
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BasicBlock *BB = WorkList.back(); WorkList.pop_back();
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// First process all successor
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for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI) {
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BasicBlock *SuccBB = *SI;
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if (DT->dominates(BB, SuccBB)) {
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WorkList.push_back(SuccBB);
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continue;
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}
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// If SuccBB is not dominated by BB then it is not removed, however remove
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// any PHI incoming edge from BB.
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for(BasicBlock::iterator SBI = SuccBB->begin(), SBE = SuccBB->end();
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SBI != SBE; ++SBI) {
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if (PHINode *PN = dyn_cast<PHINode>(SBI))
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PN->removeIncomingValue(BB);
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else
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break;
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}
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}
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// Now delete BB;
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for(BasicBlock::iterator BBI = BB->begin(), BBE = BB->end();
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BBI != BBE; ++BBI) {
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Instruction *I = BBI;
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I->replaceAllUsesWith(UndefValue::get(I->getType()));
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I->eraseFromParent();
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}
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LI->removeBlock(BB);
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BB->eraseFromParent();
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}
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}
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bool LoopIndexSplit::splitLoop(SplitInfo &SD) {
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BasicBlock *Preheader = L->getLoopPreheader();
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@ -600,9 +645,12 @@ bool LoopIndexSplit::splitLoop(SplitInfo &SD) {
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else {
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Value *C1 = new ICmpInst(SignedPredicate ?
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ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
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SD.SplitValue, ExitValue, "lsplit.ev",
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SD.SplitValue,
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ExitCondition->getOperand(ExitValueNum),
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"lsplit.ev",
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Preheader->getTerminator());
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TLExitValue = new SelectInst(C1, SD.SplitValue, ExitValue,
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TLExitValue = new SelectInst(C1, SD.SplitValue,
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ExitCondition->getOperand(ExitValueNum),
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"lsplit.ev", Preheader->getTerminator());
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Value *C2 = new ICmpInst(SignedPredicate ?
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@ -613,28 +661,62 @@ bool LoopIndexSplit::splitLoop(SplitInfo &SD) {
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"lsplit.sv", Preheader->getTerminator());
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}
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//[*] Split Exit Edge.
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//[*] Clone loop. Avoid true destination of split condition and
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// the blocks dominated by true destination.
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DenseMap<const Value *, Value *> ValueMap;
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Loop *FalseLoop = CloneLoop(L, LPM, LI, ValueMap, this);
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BasicBlock *FalseHeader = FalseLoop->getHeader();
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//[*] True loop's exit edge enters False loop.
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PHINode *IndVarClone = cast<PHINode>(ValueMap[IndVar]);
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BasicBlock *ExitBlock = ExitCondition->getParent();
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BranchInst *ExitInsn = dyn_cast<BranchInst>(ExitBlock->getTerminator());
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assert (ExitInsn && "Unable to find suitable loop exit branch");
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BasicBlock *ExitDest = ExitInsn->getSuccessor(1);
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if (L->contains(ExitDest))
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for (BasicBlock::iterator BI = FalseHeader->begin(), BE = FalseHeader->end();
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BI != BE; ++BI) {
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if (PHINode *PN = dyn_cast<PHINode>(BI)) {
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PN->removeIncomingValue(Preheader);
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if (PN == IndVarClone)
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PN->addIncoming(FLStartValue, ExitBlock);
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// else { FIXME : Handl last value assignments.}
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}
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else
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break;
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}
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if (L->contains(ExitDest)) {
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ExitDest = ExitInsn->getSuccessor(0);
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ExitInsn->setSuccessor(0, FalseHeader);
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} else
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ExitInsn->setSuccessor(1, FalseHeader);
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assert (!L->contains(ExitDest) && " Unable to find exit edge destination");
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SplitEdge(ExitBlock, ExitDest, this);
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//[*] Clone loop. Avoid true destination of split condition and
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// the blocks dominated by true destination.
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DenseMap<const Value *, Value *> ValueMap;
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CloneLoop(L, LPM, LI, ValueMap, this);
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//[*] Split Exit Edge.
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SplitEdge(ExitBlock, FalseHeader, this);
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//[*] True loops exit edge enters False loop.
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//[*] Eliminate split condition's false branch from True loop.
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// Update true loop dom info.
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//[*] Update True loop's exit value using NewExitValue.
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//[*] Update False loop's start value using NewStartValue.
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//[*] Fix lack of true branch in False loop CFG.
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// Update false loop dom info.
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//[*] Update dom info in general.
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return false;
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// Update true loop dom info (FIXME).
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BasicBlock *SplitBlock = SD.SplitCondition->getParent();
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BranchInst *BR = cast<BranchInst>(SplitBlock->getTerminator());
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BasicBlock *FBB = BR->getSuccessor(1);
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BR->setUnconditionalDest(BR->getSuccessor(0));
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removeBlocks(FBB);
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//[*] Update True loop's exit value using new exit value.
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ExitCondition->setOperand(ExitValueNum, TLExitValue);
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//[*] Eliminate split condition's true branch in False loop CFG.
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// Update false loop dom info (FXME).
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BasicBlock *FSplitBlock = cast<BasicBlock>(ValueMap[SplitBlock]);
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BranchInst *FBR = cast<BranchInst>(FSplitBlock->getTerminator());
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BasicBlock *TBB = FBR->getSuccessor(0);
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FBR->setUnconditionalDest(FBR->getSuccessor(1));
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removeBlocks(TBB);
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//[*] Update dom info in general (FIXME).
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return true;
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}
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