diff options
| -rw-r--r-- | lib/Transforms/Scalar/JumpThreading.cpp | 45 |
1 files changed, 4 insertions, 41 deletions
diff --git a/lib/Transforms/Scalar/JumpThreading.cpp b/lib/Transforms/Scalar/JumpThreading.cpp index 911f735605..ee9586a0b7 100644 --- a/lib/Transforms/Scalar/JumpThreading.cpp +++ b/lib/Transforms/Scalar/JumpThreading.cpp @@ -1005,47 +1005,10 @@ bool JumpThreading::ProcessThreadableEdges(Instruction *CondInst, bool JumpThreading::ProcessJumpOnPHI(PHINode *PN) { BasicBlock *BB = PN->getParent(); - // See if the phi node has any constant integer or undef values. If so, we - // can determine where the corresponding predecessor will branch. - for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { - Value *PredVal = PN->getIncomingValue(i); - - // Check to see if this input is a constant integer. If so, the direction - // of the branch is predictable. - if (ConstantInt *CI = dyn_cast<ConstantInt>(PredVal)) { - // Merge any common predecessors that will act the same. - BasicBlock *PredBB = FactorCommonPHIPreds(PN, CI); - - BasicBlock *SuccBB; - if (BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator())) - SuccBB = BI->getSuccessor(CI->isZero()); - else { - SwitchInst *SI = cast<SwitchInst>(BB->getTerminator()); - SuccBB = SI->getSuccessor(SI->findCaseValue(CI)); - } - - // Ok, try to thread it! - return ThreadEdge(BB, PredBB, SuccBB); - } - - // If the input is an undef, then it doesn't matter which way it will go. - // Pick an arbitrary dest and thread the edge. - if (UndefValue *UV = dyn_cast<UndefValue>(PredVal)) { - // Merge any common predecessors that will act the same. - BasicBlock *PredBB = FactorCommonPHIPreds(PN, UV); - BasicBlock *SuccBB = - BB->getTerminator()->getSuccessor(GetBestDestForJumpOnUndef(BB)); - - // Ok, try to thread it! - return ThreadEdge(BB, PredBB, SuccBB); - } - } - - // If the incoming values are all variables, we don't know the destination of - // any predecessors. However, if any of the predecessor blocks end in an - // unconditional branch, we can *duplicate* the jump into that block in order - // to further encourage jump threading and to eliminate cases where we have - // branch on a phi of an icmp (branch on icmp is much better). + // If any of the predecessor blocks end in an unconditional branch, we can + // *duplicate* the jump into that block in order to further encourage jump + // threading and to eliminate cases where we have branch on a phi of an icmp + // (branch on icmp is much better). // We don't want to do this tranformation for switches, because we don't // really want to duplicate a switch. |