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simplify GetIfCondition by using getSinglePredecessor. 

llvm-svn: 121756
This commit is contained in:
Chris Lattner 2010-12-14 07:15:21 +00:00
parent 0f4d67bd88
commit fb73de482c
1 changed files with 24 additions and 28 deletions
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52
llvm/lib/Transforms/Utils/SimplifyCFG.cpp
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@ -110,7 +110,8 @@ static void AddPredecessorToBlock(BasicBlock *Succ, BasicBlock *NewPred,
/// that will be entered from if the condition is true, and the block that will
/// be entered if the condition is false.
///
///
/// This does no checking to see if the true/false blocks have large or unsavory
/// instructions in them.
static Value *GetIfCondition(BasicBlock *BB, BasicBlock *&IfTrue,
BasicBlock *&IfFalse) {
PHINode *SomePHI = cast<PHINode>(BB->begin());
@ -121,11 +122,10 @@ static Value *GetIfCondition(BasicBlock *BB, BasicBlock *&IfTrue,
// We can only handle branches. Other control flow will be lowered to
// branches if possible anyway.
if (!isa<BranchInst>(Pred1->getTerminator()) ||
!isa<BranchInst>(Pred2->getTerminator()))
BranchInst *Pred1Br = dyn_cast<BranchInst>(Pred1->getTerminator());
BranchInst *Pred2Br = dyn_cast<BranchInst>(Pred2->getTerminator());
if (Pred1Br == 0 || Pred2Br == 0)
return 0;
BranchInst *Pred1Br = cast<BranchInst>(Pred1->getTerminator());
BranchInst *Pred2Br = cast<BranchInst>(Pred2->getTerminator());
// Eliminate code duplication by ensuring that Pred1Br is conditional if
// either are.
@ -142,6 +142,12 @@ static Value *GetIfCondition(BasicBlock *BB, BasicBlock *&IfTrue,
}
if (Pred1Br->isConditional()) {
// The only thing we have to watch out for here is to make sure that Pred2
// doesn't have incoming edges from other blocks. If it does, the condition
// doesn't dominate BB.
if (Pred2->getSinglePredecessor() == 0)
return 0;
// If we found a conditional branch predecessor, make sure that it branches
// to BB and Pred2Br. If it doesn't, this isn't an "if statement".
if (Pred1Br->getSuccessor(0) == BB &&
@ -158,39 +164,29 @@ static Value *GetIfCondition(BasicBlock *BB, BasicBlock *&IfTrue,
return 0;
}
// The only thing we have to watch out for here is to make sure that Pred2
// doesn't have incoming edges from other blocks. If it does, the condition
// doesn't dominate BB.
if (++pred_begin(Pred2) != pred_end(Pred2))
return 0;
return Pred1Br->getCondition();
}
// Ok, if we got here, both predecessors end with an unconditional branch to
// BB. Don't panic! If both blocks only have a single (identical)
// predecessor, and THAT is a conditional branch, then we're all ok!
if (pred_begin(Pred1) == pred_end(Pred1) ||
++pred_begin(Pred1) != pred_end(Pred1) ||
pred_begin(Pred2) == pred_end(Pred2) ||
++pred_begin(Pred2) != pred_end(Pred2) ||
*pred_begin(Pred1) != *pred_begin(Pred2))
BasicBlock *CommonPred = Pred1->getSinglePredecessor();
if (CommonPred == 0 || CommonPred != Pred2->getSinglePredecessor())
return 0;
// Otherwise, if this is a conditional branch, then we can use it!
BasicBlock *CommonPred = *pred_begin(Pred1);
if (BranchInst *BI = dyn_cast<BranchInst>(CommonPred->getTerminator())) {
assert(BI->isConditional() && "Two successors but not conditional?");
if (BI->getSuccessor(0) == Pred1) {
IfTrue = Pred1;
IfFalse = Pred2;
} else {
IfTrue = Pred2;
IfFalse = Pred1;
}
return BI->getCondition();
BranchInst *BI = dyn_cast<BranchInst>(CommonPred->getTerminator());
if (BI == 0) return 0;
assert(BI->isConditional() && "Two successors but not conditional?");
if (BI->getSuccessor(0) == Pred1) {
IfTrue = Pred1;
IfFalse = Pred2;
} else {
IfTrue = Pred2;
IfFalse = Pred1;
}
return 0;
return BI->getCondition();
}
/// DominatesMergePoint - If we have a merge point of an "if condition" as