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Factor the actual simplification out of SimplifyIndirectBrOnSelect and into a new helper function so it can be reused in e.g. an upcoming SimplifySwitchOnSelect.

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No functional change.

llvm-svn: 123234
This commit is contained in:
Frits van Bommel 2011-01-11 12:52:11 +00:00
parent 82cc1fb69c
commit f5bd48972a
1 changed files with 58 additions and 47 deletions
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105
lib/Transforms/Utils/SimplifyCFG.cpp
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@ -1728,6 +1728,62 @@ static bool SimplifyCondBranchToCondBranch(BranchInst *PBI, BranchInst *BI) {
return true;
}
// SimplifyTerminatorOnSelect - Simplifies a terminator by replacing it with a
// branch to TrueBB if Cond is true or to FalseBB if Cond is false.
// Takes care of updating the successors and removing the old terminator.
// Also makes sure not to introduce new successors by assuming that edges to
// non-successor TrueBBs and FalseBBs aren't reachable.
static bool SimplifyTerminatorOnSelect(TerminatorInst *OldTerm, Value *Cond,
BasicBlock *TrueBB, BasicBlock *FalseBB){
// Remove any superfluous successor edges from the CFG.
// First, figure out which successors to preserve.
// If TrueBB and FalseBB are equal, only try to preserve one copy of that
// successor.
BasicBlock *KeepEdge1 = TrueBB;
BasicBlock *KeepEdge2 = TrueBB != FalseBB ? FalseBB : 0;
// Then remove the rest.
for (unsigned I = 0, E = OldTerm->getNumSuccessors(); I != E; ++I) {
BasicBlock *Succ = OldTerm->getSuccessor(I);
// Make sure only to keep exactly one copy of each edge.
if (Succ == KeepEdge1)
KeepEdge1 = 0;
else if (Succ == KeepEdge2)
KeepEdge2 = 0;
else
Succ->removePredecessor(OldTerm->getParent());
}
// Insert an appropriate new terminator.
if ((KeepEdge1 == 0) && (KeepEdge2 == 0)) {
if (TrueBB == FalseBB)
// We were only looking for one successor, and it was present.
// Create an unconditional branch to it.
BranchInst::Create(TrueBB, OldTerm);
else
// We found both of the successors we were looking for.
// Create a conditional branch sharing the condition of the select.
BranchInst::Create(TrueBB, FalseBB, Cond, OldTerm);
} else if (KeepEdge1 && (KeepEdge2 || TrueBB == FalseBB)) {
// Neither of the selected blocks were successors, so this
// terminator must be unreachable.
new UnreachableInst(OldTerm->getContext(), OldTerm);
} else {
// One of the selected values was a successor, but the other wasn't.
// Insert an unconditional branch to the one that was found;
// the edge to the one that wasn't must be unreachable.
if (KeepEdge1 == 0)
// Only TrueBB was found.
BranchInst::Create(TrueBB, OldTerm);
else
// Only FalseBB was found.
BranchInst::Create(FalseBB, OldTerm);
}
EraseTerminatorInstAndDCECond(OldTerm);
return true;
}
// SimplifyIndirectBrOnSelect - Replaces
// (indirectbr (select cond, blockaddress(@fn, BlockA),
// blockaddress(@fn, BlockB)))
@ -1744,53 +1800,8 @@ static bool SimplifyIndirectBrOnSelect(IndirectBrInst *IBI, SelectInst *SI) {
BasicBlock *TrueBB = TBA->getBasicBlock();
BasicBlock *FalseBB = FBA->getBasicBlock();
// Remove any superfluous successor edges from the CFG.
// First, figure out which successors to preserve.
// If TrueBB and FalseBB are equal, only try to preserve one copy of that
// successor.
BasicBlock *KeepEdge1 = TrueBB;
BasicBlock *KeepEdge2 = TrueBB != FalseBB ? FalseBB : 0;
// Then remove the rest.
for (unsigned I = 0, E = IBI->getNumSuccessors(); I != E; ++I) {
BasicBlock *Succ = IBI->getSuccessor(I);
// Make sure only to keep exactly one copy of each edge.
if (Succ == KeepEdge1)
KeepEdge1 = 0;
else if (Succ == KeepEdge2)
KeepEdge2 = 0;
else
Succ->removePredecessor(IBI->getParent());
}
// Insert an appropriate new terminator.
if ((KeepEdge1 == 0) && (KeepEdge2 == 0)) {
if (TrueBB == FalseBB)
// We were only looking for one successor, and it was present.
// Create an unconditional branch to it.
BranchInst::Create(TrueBB, IBI);
else
// We found both of the successors we were looking for.
// Create a conditional branch sharing the condition of the select.
BranchInst::Create(TrueBB, FalseBB, SI->getCondition(), IBI);
} else if (KeepEdge1 && (KeepEdge2 || TrueBB == FalseBB)) {
// Neither of the selected blocks were successors, so this
// indirectbr must be unreachable.
new UnreachableInst(IBI->getContext(), IBI);
} else {
// One of the selected values was a successor, but the other wasn't.
// Insert an unconditional branch to the one that was found;
// the edge to the one that wasn't must be unreachable.
if (KeepEdge1 == 0)
// Only TrueBB was found.
BranchInst::Create(TrueBB, IBI);
else
// Only FalseBB was found.
BranchInst::Create(FalseBB, IBI);
}
EraseTerminatorInstAndDCECond(IBI);
return true;
// Perform the actual simplification.
return SimplifyTerminatorOnSelect(IBI, SI->getCondition(), TrueBB, FalseBB);
}
/// TryToSimplifyUncondBranchWithICmpInIt - This is called when we find an icmp