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factor new code out to a SimplifyBranchOnICmpChain helper function. 

llvm-svn: 121681
This commit is contained in:
Chris Lattner 2010-12-13 05:03:41 +00:00
parent a442f24a36
commit a69c443459
1 changed files with 91 additions and 77 deletions
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168
llvm/lib/Transforms/Utils/SimplifyCFG.cpp
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@ -1847,6 +1847,93 @@ static bool TryToSimplifyUncondBranchWithICmpInIt(ICmpInst *ICI) {
return true;
}
/// SimplifyBranchOnICmpChain - The specified branch is a conditional branch.
/// Check to see if it is branching on an or/and chain of icmp instructions, and
/// fold it into a switch instruction if so.
static bool SimplifyBranchOnICmpChain(BranchInst *BI, const TargetData *TD) {
Instruction *Cond = dyn_cast<Instruction>(BI->getCondition());
if (Cond == 0) return false;
// Change br (X == 0 | X == 1), T, F into a switch instruction.
// If this is a bunch of seteq's or'd together, or if it's a bunch of
// 'setne's and'ed together, collect them.
Value *CompVal = 0;
std::vector<ConstantInt*> Values;
bool TrueWhenEqual = true;
Value *ExtraCase = 0;
if (Cond->getOpcode() == Instruction::Or) {
CompVal = GatherConstantCompares(Cond, Values, ExtraCase, TD, true);
} else if (Cond->getOpcode() == Instruction::And) {
CompVal = GatherConstantCompares(Cond, Values, ExtraCase, TD, false);
TrueWhenEqual = false;
}
// If we didn't have a multiply compared value, fail.
if (CompVal == 0) return false;
// There might be duplicate constants in the list, which the switch
// instruction can't handle, remove them now.
array_pod_sort(Values.begin(), Values.end(), ConstantIntSortPredicate);
Values.erase(std::unique(Values.begin(), Values.end()), Values.end());
// If Extra was used, we require at least two switch values to do the
// transformation. A switch with one value is just an cond branch.
if (ExtraCase && Values.size() < 2) return false;
// Figure out which block is which destination.
BasicBlock *DefaultBB = BI->getSuccessor(1);
BasicBlock *EdgeBB = BI->getSuccessor(0);
if (!TrueWhenEqual) std::swap(DefaultBB, EdgeBB);
BasicBlock *BB = BI->getParent();
// If there are any extra values that couldn't be folded into the switch
// then we evaluate them with an explicit branch first. Split the block
// right before the condbr to handle it.
if (ExtraCase) {
BasicBlock *NewBB = BB->splitBasicBlock(BI, "switch.early.test");
// Remove the uncond branch added to the old block.
TerminatorInst *OldTI = BB->getTerminator();
BranchInst::Create(EdgeBB, NewBB, ExtraCase, OldTI);
OldTI->eraseFromParent();
BB = NewBB;
}
// Convert pointer to int before we switch.
if (CompVal->getType()->isPointerTy()) {
assert(TD && "Cannot switch on pointer without TargetData");
CompVal = new PtrToIntInst(CompVal,
TD->getIntPtrType(CompVal->getContext()),
"magicptr", BI);
}
// Create the new switch instruction now.
SwitchInst *New =
SwitchInst::Create(CompVal, DefaultBB, Values.size(), BI);
// Add all of the 'cases' to the switch instruction.
for (unsigned i = 0, e = Values.size(); i != e; ++i)
New->addCase(Values[i], EdgeBB);
// We added edges from PI to the EdgeBB. As such, if there were any
// PHI nodes in EdgeBB, they need entries to be added corresponding to
// the number of edges added.
for (BasicBlock::iterator BBI = EdgeBB->begin();
isa<PHINode>(BBI); ++BBI) {
PHINode *PN = cast<PHINode>(BBI);
Value *InVal = PN->getIncomingValueForBlock(BB);
for (unsigned i = 0, e = Values.size()-1; i != e; ++i)
PN->addIncoming(InVal, BB);
}
// Erase the old branch instruction.
EraseTerminatorInstAndDCECond(BI);
return true;
}
bool SimplifyCFGOpt::run(BasicBlock *BB) {
bool Changed = false;
Function *Fn = BB->getParent();
@ -2047,6 +2134,10 @@ bool SimplifyCFGOpt::run(BasicBlock *BB) {
}
}
// Try to turn "br (X == 0 | X == 1), T, F" into a switch instruction.
if (SimplifyBranchOnICmpChain(BI, TD))
return true;
// If this is a branch on a phi node in the current block, thread control
// through this block if any PHI node entries are constants.
if (PHINode *PN = dyn_cast<PHINode>(BI->getCondition()))
@ -2060,89 +2151,12 @@ bool SimplifyCFGOpt::run(BasicBlock *BB) {
if (FoldBranchToCommonDest(BI))
return SimplifyCFG(BB) | true;
// Scan predecessor blocks for conditional branches.
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
if (BranchInst *PBI = dyn_cast<BranchInst>((*PI)->getTerminator()))
if (PBI != BI && PBI->isConditional())
if (SimplifyCondBranchToCondBranch(PBI, BI))
return SimplifyCFG(BB) | true;
// Change br (X == 0 | X == 1), T, F into a switch instruction.
// If this is a bunch of seteq's or'd together, or if it's a bunch of
// 'setne's and'ed together, collect them.
Value *CompVal = 0;
std::vector<ConstantInt*> Values;
bool TrueWhenEqual = true;
Value *ExtraCase = 0;
if (Instruction *Cond = dyn_cast<Instruction>(BI->getCondition())) {
if (Cond->getOpcode() == Instruction::Or) {
CompVal = GatherConstantCompares(Cond, Values, ExtraCase, TD, true);
} else if (Cond->getOpcode() == Instruction::And) {
CompVal = GatherConstantCompares(Cond, Values, ExtraCase, TD, false);
TrueWhenEqual = false;
}
}
// We do this transformation if we'll end up creating a switch with at
// least two values if Extra is used.
if (CompVal && (!ExtraCase || Values.size() > 1)) {
// There might be duplicate constants in the list, which the switch
// instruction can't handle, remove them now.
array_pod_sort(Values.begin(), Values.end(), ConstantIntSortPredicate);
Values.erase(std::unique(Values.begin(), Values.end()), Values.end());
// Figure out which block is which destination.
BasicBlock *DefaultBB = BI->getSuccessor(1);
BasicBlock *EdgeBB = BI->getSuccessor(0);
if (!TrueWhenEqual) std::swap(DefaultBB, EdgeBB);
// If there are any extra values that couldn't be folded into the switch
// then we evaluate them with an explicit branch first. Split the block
// right before the condbr to handle it.
if (ExtraCase) {
BasicBlock *NewBB = BB->splitBasicBlock(BI, "switch.early.test");
// Remove the uncond branch added to the old block.
TerminatorInst *OldTI = BB->getTerminator();
BranchInst::Create(EdgeBB, NewBB, ExtraCase, OldTI);
OldTI->eraseFromParent();
BB = NewBB;
}
// Convert pointer to int before we switch.
if (CompVal->getType()->isPointerTy()) {
assert(TD && "Cannot switch on pointer without TargetData");
CompVal = new PtrToIntInst(CompVal,
TD->getIntPtrType(CompVal->getContext()),
"magicptr", BI);
}
// Create the new switch instruction now.
SwitchInst *New =
SwitchInst::Create(CompVal, DefaultBB, Values.size(), BI);
// Add all of the 'cases' to the switch instruction.
for (unsigned i = 0, e = Values.size(); i != e; ++i)
New->addCase(Values[i], EdgeBB);
// We added edges from PI to the EdgeBB. As such, if there were any
// PHI nodes in EdgeBB, they need entries to be added corresponding to
// the number of edges added.
for (BasicBlock::iterator BBI = EdgeBB->begin();
isa<PHINode>(BBI); ++BBI) {
PHINode *PN = cast<PHINode>(BBI);
Value *InVal = PN->getIncomingValueForBlock(BB);
for (unsigned i = 0, e = Values.size()-1; i != e; ++i)
PN->addIncoming(InVal, BB);
}
// Erase the old branch instruction.
EraseTerminatorInstAndDCECond(BI);
return true;
}
}
} else if (isa<UnreachableInst>(BB->getTerminator())) {
// If there are any instructions immediately before the unreachable that can