forked from OSchip/llvm-project
parent
fbc80692e4
commit
ae8aa646f1
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@ -6255,58 +6255,57 @@ static bool DeadPHICycle(PHINode *PN, std::set<PHINode*> &PotentiallyDeadPHIs) {
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// PHINode simplification
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//
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Instruction *InstCombiner::visitPHINode(PHINode &PN) {
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// If LCSSA is around, don't nuke PHIs.
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if (!mustPreserveAnalysisID(LCSSAID)) {
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if (Value *V = PN.hasConstantValue())
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return ReplaceInstUsesWith(PN, V);
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if (mustPreservePassID(LCSSAID)) return 0;
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// If the only user of this instruction is a cast instruction, and all of
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//the incoming values are constants, change this PHI to merge together the
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// casted constants.
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if (PN.hasOneUse())
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if (CastInst *CI = dyn_cast<CastInst>(PN.use_back()))
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if (CI->getType() != PN.getType()) { // noop casts will be folded
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bool AllConstant = true;
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for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
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if (!isa<Constant>(PN.getIncomingValue(i))) {
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AllConstant = false;
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break;
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}
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if (AllConstant) {
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// Make a new PHI with all casted values.
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PHINode *New = new PHINode(CI->getType(), PN.getName(), &PN);
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for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
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Constant *OldArg = cast<Constant>(PN.getIncomingValue(i));
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New->addIncoming(ConstantExpr::getCast(OldArg, New->getType()),
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PN.getIncomingBlock(i));
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}
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if (Value *V = PN.hasConstantValue())
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return ReplaceInstUsesWith(PN, V);
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// Update the cast instruction.
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CI->setOperand(0, New);
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WorkList.push_back(CI); // revisit the cast instruction to fold.
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WorkList.push_back(New); // Make sure to revisit the new Phi
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return &PN; // PN is now dead!
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// If the only user of this instruction is a cast instruction, and all of the
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// incoming values are constants, change this PHI to merge together the casted
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// constants.
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if (PN.hasOneUse())
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if (CastInst *CI = dyn_cast<CastInst>(PN.use_back()))
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if (CI->getType() != PN.getType()) { // noop casts will be folded
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bool AllConstant = true;
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for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
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if (!isa<Constant>(PN.getIncomingValue(i))) {
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AllConstant = false;
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break;
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}
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if (AllConstant) {
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// Make a new PHI with all casted values.
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PHINode *New = new PHINode(CI->getType(), PN.getName(), &PN);
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for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
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Constant *OldArg = cast<Constant>(PN.getIncomingValue(i));
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New->addIncoming(ConstantExpr::getCast(OldArg, New->getType()),
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PN.getIncomingBlock(i));
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}
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// Update the cast instruction.
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CI->setOperand(0, New);
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WorkList.push_back(CI); // revisit the cast instruction to fold.
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WorkList.push_back(New); // Make sure to revisit the new Phi
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return &PN; // PN is now dead!
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}
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// If all PHI operands are the same operation, pull them through the PHI,
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// reducing code size.
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if (isa<Instruction>(PN.getIncomingValue(0)) &&
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PN.getIncomingValue(0)->hasOneUse())
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if (Instruction *Result = FoldPHIArgOpIntoPHI(PN))
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return Result;
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// If this is a trivial cycle in the PHI node graph, remove it. Basically,
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// if this PHI only has a single use (a PHI), and if that PHI only has one
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// use (a PHI)... break the cycle.
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if (PN.hasOneUse())
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if (PHINode *PU = dyn_cast<PHINode>(PN.use_back())) {
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std::set<PHINode*> PotentiallyDeadPHIs;
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PotentiallyDeadPHIs.insert(&PN);
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if (DeadPHICycle(PU, PotentiallyDeadPHIs))
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return ReplaceInstUsesWith(PN, UndefValue::get(PN.getType()));
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}
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}
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// If all PHI operands are the same operation, pull them through the PHI,
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// reducing code size.
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if (isa<Instruction>(PN.getIncomingValue(0)) &&
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PN.getIncomingValue(0)->hasOneUse())
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if (Instruction *Result = FoldPHIArgOpIntoPHI(PN))
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return Result;
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// If this is a trivial cycle in the PHI node graph, remove it. Basically, if
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// this PHI only has a single use (a PHI), and if that PHI only has one use (a
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// PHI)... break the cycle.
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if (PN.hasOneUse())
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if (PHINode *PU = dyn_cast<PHINode>(PN.use_back())) {
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std::set<PHINode*> PotentiallyDeadPHIs;
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PotentiallyDeadPHIs.insert(&PN);
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if (DeadPHICycle(PU, PotentiallyDeadPHIs))
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return ReplaceInstUsesWith(PN, UndefValue::get(PN.getType()));
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}
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return 0;
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}
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