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Simplification of trip counting machinery.
- make sure to check the indvar type before anything else (efficiency)
- Make sure to insert the 'add' into the program, even though it'll be
dead
- Wrap code at 80 columns
- Other minor cleanups to reduce indentation level
llvm-svn: 8434
This commit is contained in:
Chris Lattner
parent
29a0f79c05
commit
37123e1b58
@ -155,7 +155,9 @@ InductionVariable::InductionVariable(PHINode *P, LoopInfo *LoopInfo): End(0) {
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}
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Value* InductionVariable::getExecutionCount(LoopInfo *LoopInfo) {
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Value *InductionVariable::getExecutionCount(LoopInfo *LoopInfo) {
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if (InductionType != Canonical) return 0;
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DEBUG(std::cerr << "entering getExecutionCount\n");
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// Don't recompute if already available
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@ -167,111 +169,104 @@ Value* InductionVariable::getExecutionCount(LoopInfo *LoopInfo) {
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const Loop *L = LoopInfo ? LoopInfo->getLoopFor(Phi->getParent()) : 0;
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if (!L) {
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DEBUG(std::cerr << "null loop. oops\n");
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return NULL;
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return 0;
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}
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// >1 backedge => cannot predict number of iterations
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if (Phi->getNumIncomingValues() != 2) {
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DEBUG(std::cerr << ">2 incoming values. oops\n");
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return NULL;
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return 0;
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}
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// Find final node: predecesor of the loop header that's also an exit
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BasicBlock *terminator = 0;
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BasicBlock *header = L->getHeader();
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for (pred_iterator PI = pred_begin(header), PE = pred_end(header);
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PI != PE; ++PI) {
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for (pred_iterator PI = pred_begin(L->getHeader()),
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PE = pred_end(L->getHeader()); PI != PE; ++PI)
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if (L->isLoopExit(*PI)) {
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terminator = *PI;
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break;
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}
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}
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// Break in the loop => cannot predict number of iterations
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// break: any block which is an exit node whose successor is not in loop,
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// and this block is not marked as the terminator
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//
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const std::vector<BasicBlock*> &blocks = L->getBlocks();
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for (std::vector<BasicBlock*>::const_iterator i = blocks.begin(), e = blocks.end();
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i != e; ++i) {
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if (L->isLoopExit(*i) && (*i != terminator)) {
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for (succ_iterator SI = succ_begin(*i), SE = succ_end(*i); SI != SE; ++SI) {
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if (! L->contains(*SI)) {
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for (std::vector<BasicBlock*>::const_iterator I = blocks.begin(),
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e = blocks.end(); I != e; ++I)
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if (L->isLoopExit(*I) && *I != terminator)
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for (succ_iterator SI = succ_begin(*I), SE = succ_end(*I); SI != SE; ++SI)
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if (!L->contains(*SI)) {
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DEBUG(std::cerr << "break found in loop");
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return NULL;
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return 0;
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}
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}
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}
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}
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BranchInst *B = dyn_cast<BranchInst>(terminator->getTerminator());
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if (!B) {
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// this really should not happen
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DEBUG(std::cerr << "no terminator instruction!");
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return NULL;
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DEBUG(std::cerr << "Terminator is not a cond branch!");
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return 0;
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}
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SetCondInst *SCI = dyn_cast<SetCondInst>(B->getCondition());
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if (SCI && InductionType == Canonical) {
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DEBUG(std::cerr << "sci:" << *SCI);
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Value *condVal0 = SCI->getOperand(0);
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Value *condVal1 = SCI->getOperand(1);
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Value *indVar = 0;
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// the induction variable is the one coming from the backedge
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if (L->contains(Phi->getIncomingBlock(0))) {
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indVar = Phi->getIncomingValue(0);
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} else {
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indVar = Phi->getIncomingValue(1);
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}
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// check to see if indVar is one of the parameters in SCI
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// and if the other is loop-invariant, it is the UB
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if (indVar == condVal0) {
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if (isLoopInvariant(condVal1, L)) {
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End = condVal1;
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} else {
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DEBUG(std::cerr << "not loop invariant 1\n");
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}
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} else if (indVar == condVal1) {
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if (isLoopInvariant(condVal0, L)) {
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End = condVal0;
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} else {
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DEBUG(std::cerr << "not loop invariant 0\n");
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}
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}
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if (End) {
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switch (SCI->getOpcode()) {
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case Instruction::SetLT:
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case Instruction::SetNE: break; // already done
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case Instruction::SetLE: {
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// if compared to a constant int N, then predict N+1 iterations
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if (ConstantSInt *ubSigned = dyn_cast<ConstantSInt>(End)) {
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End = ConstantSInt::get(ubSigned->getType(), ubSigned->getValue()+1);
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DEBUG(std::cerr << "signed int constant\n");
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} else if (ConstantUInt *ubUnsigned = dyn_cast<ConstantUInt>(End)) {
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End = ConstantUInt::get(ubUnsigned->getType(),
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ubUnsigned->getValue()+1);
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DEBUG(std::cerr << "unsigned int constant\n");
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} else {
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DEBUG(std::cerr << "symbolic bound\n");
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//End = NULL;
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// new expression N+1
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End = BinaryOperator::create(Instruction::Add, End,
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ConstantUInt::get(ubUnsigned->getType(),
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1));
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}
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break;
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}
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default: End = NULL; // cannot predict
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}
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}
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return End;
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} else {
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DEBUG(std::cerr << "SCI null or non-canonical ind var\n");
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if (!SCI) {
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DEBUG(std::cerr << "Not a cond branch on setcc!\n");
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return 0;
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}
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DEBUG(std::cerr << "sci:" << *SCI);
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Value *condVal0 = SCI->getOperand(0);
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Value *condVal1 = SCI->getOperand(1);
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Value *indVar = 0;
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// the induction variable is the one coming from the backedge
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indVar = Phi->getIncomingValue(L->contains(Phi->getIncomingBlock(1)));
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// Check to see if indVar is one of the parameters in SCI and if the other is
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// loop-invariant, it is the UB
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if (indVar == condVal0) {
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if (isLoopInvariant(condVal1, L))
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End = condVal1;
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else {
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DEBUG(std::cerr << "not loop invariant 1\n");
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return 0;
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}
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} else if (indVar == condVal1) {
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if (isLoopInvariant(condVal0, L))
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End = condVal0;
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else {
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DEBUG(std::cerr << "not loop invariant 0\n");
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return 0;
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}
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} else {
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DEBUG(std::cerr << "Loop condition doesn't directly uses indvar\n");
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return 0;
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}
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switch (SCI->getOpcode()) {
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case Instruction::SetLT:
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case Instruction::SetNE: return End; // already done
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case Instruction::SetLE:
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// if compared to a constant int N, then predict N+1 iterations
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if (ConstantSInt *ubSigned = dyn_cast<ConstantSInt>(End)) {
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DEBUG(std::cerr << "signed int constant\n");
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return ConstantSInt::get(ubSigned->getType(), ubSigned->getValue()+1);
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} else if (ConstantUInt *ubUnsigned = dyn_cast<ConstantUInt>(End)) {
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DEBUG(std::cerr << "unsigned int constant\n");
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return ConstantUInt::get(ubUnsigned->getType(),
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ubUnsigned->getValue()+1);
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} else {
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DEBUG(std::cerr << "symbolic bound\n");
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// new expression N+1, insert right before the SCI. FIXME: If End is loop
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// invariant, then so is this expression. We should insert it in the loop
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// preheader if it exists.
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return BinaryOperator::create(Instruction::Add, End,
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ConstantInt::get(End->getType(), 1),
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"tripcount", SCI);
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}
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default:
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return 0; // cannot predict
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}
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return NULL;
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}
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