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| author | rdivacky <rdivacky@FreeBSD.org> | 2010-02-16 09:30:23 +0000 |
|---|---|---|
| committer | rdivacky <rdivacky@FreeBSD.org> | 2010-02-16 09:30:23 +0000 |
| commit | f25ddd991a5601d0101602c4c263a58c7af4b8a2 (patch) | |
| tree | 4cfca640904d1896e25032757a61f8959c066919 /lib/Transforms/Scalar/JumpThreading.cpp | |
| parent | 3fd58f91dd318518f7daa4ba64c0aaf31799d89b (diff) | |
| download | FreeBSD-src-f25ddd991a5601d0101602c4c263a58c7af4b8a2.zip FreeBSD-src-f25ddd991a5601d0101602c4c263a58c7af4b8a2.tar.gz | |
Update LLVM to r96341.
Diffstat (limited to 'lib/Transforms/Scalar/JumpThreading.cpp')
| -rw-r--r-- | lib/Transforms/Scalar/JumpThreading.cpp | 48 |
1 files changed, 42 insertions, 6 deletions
diff --git a/lib/Transforms/Scalar/JumpThreading.cpp b/lib/Transforms/Scalar/JumpThreading.cpp index 9531311..8f21aac 100644 --- a/lib/Transforms/Scalar/JumpThreading.cpp +++ b/lib/Transforms/Scalar/JumpThreading.cpp @@ -336,13 +336,18 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,PredValueInfo &Result){ else InterestingVal = ConstantInt::getFalse(I->getContext()); - // Scan for the sentinel. + // Scan for the sentinel. If we find an undef, force it to the + // interesting value: x|undef -> true and x&undef -> false. for (unsigned i = 0, e = LHSVals.size(); i != e; ++i) - if (LHSVals[i].first == InterestingVal || LHSVals[i].first == 0) + if (LHSVals[i].first == InterestingVal || LHSVals[i].first == 0) { Result.push_back(LHSVals[i]); + Result.back().first = InterestingVal; + } for (unsigned i = 0, e = RHSVals.size(); i != e; ++i) - if (RHSVals[i].first == InterestingVal || RHSVals[i].first == 0) + if (RHSVals[i].first == InterestingVal || RHSVals[i].first == 0) { Result.push_back(RHSVals[i]); + Result.back().first = InterestingVal; + } return !Result.empty(); } @@ -400,7 +405,7 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,PredValueInfo &Result){ // If comparing a live-in value against a constant, see if we know the // live-in value on any predecessors. if (LVI && isa<Constant>(Cmp->getOperand(1)) && - Cmp->getType()->isInteger() && // Not vector compare. + Cmp->getType()->isIntegerTy() && // Not vector compare. (!isa<Instruction>(Cmp->getOperand(0)) || cast<Instruction>(Cmp->getOperand(0))->getParent() != BB)) { Constant *RHSCst = cast<Constant>(Cmp->getOperand(1)); @@ -451,6 +456,12 @@ static unsigned GetBestDestForJumpOnUndef(BasicBlock *BB) { /// ProcessBlock - If there are any predecessors whose control can be threaded /// through to a successor, transform them now. bool JumpThreading::ProcessBlock(BasicBlock *BB) { + // If the block is trivially dead, just return and let the caller nuke it. + // This simplifies other transformations. + if (pred_begin(BB) == pred_end(BB) && + BB != &BB->getParent()->getEntryBlock()) + return false; + // If this block has a single predecessor, and if that pred has a single // successor, merge the blocks. This encourages recursive jump threading // because now the condition in this block can be threaded through @@ -1117,6 +1128,11 @@ bool JumpThreading::ProcessBranchOnXOR(BinaryOperator *BO) { isa<ConstantInt>(BO->getOperand(1))) return false; + // If the first instruction in BB isn't a phi, we won't be able to infer + // anything special about any particular predecessor. + if (!isa<PHINode>(BB->front())) + return false; + // If we have a xor as the branch input to this block, and we know that the // LHS or RHS of the xor in any predecessor is true/false, then we can clone // the condition into the predecessor and fix that value to true, saving some @@ -1174,6 +1190,26 @@ bool JumpThreading::ProcessBranchOnXOR(BinaryOperator *BO) { BlocksToFoldInto.push_back(XorOpValues[i].second); } + // If we inferred a value for all of the predecessors, then duplication won't + // help us. However, we can just replace the LHS or RHS with the constant. + if (BlocksToFoldInto.size() == + cast<PHINode>(BB->front()).getNumIncomingValues()) { + if (SplitVal == 0) { + // If all preds provide undef, just nuke the xor, because it is undef too. + BO->replaceAllUsesWith(UndefValue::get(BO->getType())); + BO->eraseFromParent(); + } else if (SplitVal->isZero()) { + // If all preds provide 0, replace the xor with the other input. + BO->replaceAllUsesWith(BO->getOperand(isLHS)); + BO->eraseFromParent(); + } else { + // If all preds provide 1, set the computed value to 1. + BO->setOperand(!isLHS, SplitVal); + } + + return true; + } + // Try to duplicate BB into PredBB. return DuplicateCondBranchOnPHIIntoPred(BB, BlocksToFoldInto); } @@ -1393,9 +1429,9 @@ bool JumpThreading::DuplicateCondBranchOnPHIIntoPred(BasicBlock *BB, // Unless PredBB ends with an unconditional branch, split the edge so that we // can just clone the bits from BB into the end of the new PredBB. - BranchInst *OldPredBranch = cast<BranchInst>(PredBB->getTerminator()); + BranchInst *OldPredBranch = dyn_cast<BranchInst>(PredBB->getTerminator()); - if (!OldPredBranch->isUnconditional()) { + if (OldPredBranch == 0 || !OldPredBranch->isUnconditional()) { PredBB = SplitEdge(PredBB, BB, this); OldPredBranch = cast<BranchInst>(PredBB->getTerminator()); } |
