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eliminate some more code subsumed by r86264 

llvm-svn: 86267
This commit is contained in:
Chris Lattner 2009-11-06 18:22:54 +00:00
parent 2f6184f6aa
commit 899ef22acb
1 changed files with 4 additions and 41 deletions
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45
llvm/lib/Transforms/Scalar/JumpThreading.cpp
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@ -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.