if (BI->isUnconditional() && BI->getSuccessor(0) == BB) {
if (!AggressiveInsts) return false;
// Okay, it looks like the instruction IS in the "condition". Check to
- // see if its a cheap instruction to unconditionally compute, and if it
+ // see if it's a cheap instruction to unconditionally compute, and if it
// only uses stuff defined outside of the condition. If so, hoist it out.
if (!I->isSafeToSpeculativelyExecute())
return false;
ConstantInt *SimplifyCFGOpt::GetConstantInt(Value *V) {
// Normal constant int.
ConstantInt *CI = dyn_cast<ConstantInt>(V);
- if (CI || !TD || !isa<Constant>(V) || !isa<PointerType>(V->getType()))
+ if (CI || !TD || !isa<Constant>(V) || !V->getType()->isPointerTy())
return CI;
// This is some kind of pointer constant. Turn it into a pointer-sized
AddPredecessorToBlock(NewSuccessors[i], Pred, BB);
// Convert pointer to int before we switch.
- if (isa<PointerType>(CV->getType())) {
+ if (CV->getType()->isPointerTy()) {
assert(TD && "Cannot switch on pointer without TargetData");
CV = new PtrToIntInst(CV, TD->getIntPtrType(CV->getContext()),
"magicptr", PTI);
case Instruction::Add:
case Instruction::Sub:
// Not worth doing for vector ops.
- if (isa<VectorType>(HInst->getType()))
+ if (HInst->getType()->isVectorTy())
return false;
break;
case Instruction::And:
case Instruction::LShr:
case Instruction::AShr:
// Don't mess with vector operations.
- if (isa<VectorType>(HInst->getType()))
+ if (HInst->getType()->isVectorTy())
return false;
break; // These are all cheap and non-trapping instructions.
}
UI != E; ++UI) {
// Ignore any user that is not a PHI node in BB2. These can only occur in
// unreachable blocks, because they would not be dominated by the instr.
- PHINode *PN = dyn_cast<PHINode>(UI);
+ PHINode *PN = dyn_cast<PHINode>(*UI);
if (!PN || PN->getParent() != BB2)
return false;
PHIUses.push_back(PN);
bool llvm::FoldBranchToCommonDest(BranchInst *BI) {
BasicBlock *BB = BI->getParent();
Instruction *Cond = dyn_cast<Instruction>(BI->getCondition());
- if (Cond == 0) return false;
-
+ if (Cond == 0 || (!isa<CmpInst>(Cond) && !isa<BinaryOperator>(Cond)) ||
+ Cond->getParent() != BB || !Cond->hasOneUse())
+ return false;
// Only allow this if the condition is a simple instruction that can be
// executed unconditionally. It must be in the same block as the branch, and
// Ignore dbg intrinsics.
while(isa<DbgInfoIntrinsic>(FrontIt))
++FrontIt;
- if ((!isa<CmpInst>(Cond) && !isa<BinaryOperator>(Cond)) ||
- Cond->getParent() != BB || &*FrontIt != Cond || !Cond->hasOneUse()) {
- return false;
+
+ // Allow a single instruction to be hoisted in addition to the compare
+ // that feeds the branch. We later ensure that any values that _it_ uses
+ // were also live in the predecessor, so that we don't unnecessarily create
+ // register pressure or inhibit out-of-order execution.
+ Instruction *BonusInst = 0;
+ if (&*FrontIt != Cond &&
+ FrontIt->hasOneUse() && *FrontIt->use_begin() == Cond &&
+ FrontIt->isSafeToSpeculativelyExecute()) {
+ BonusInst = &*FrontIt;
+ ++FrontIt;
}
+ // Only a single bonus inst is allowed.
+ if (&*FrontIt != Cond)
+ return false;
+
// Make sure the instruction after the condition is the cond branch.
BasicBlock::iterator CondIt = Cond; ++CondIt;
// Ingore dbg intrinsics.
!SafeToMergeTerminators(BI, PBI))
continue;
+ // Ensure that any values used in the bonus instruction are also used
+ // by the terminator of the predecessor. This means that those values
+ // must already have been resolved, so we won't be inhibiting the
+ // out-of-order core by speculating them earlier.
+ if (BonusInst) {
+ // Collect the values used by the bonus inst
+ SmallPtrSet<Value*, 4> UsedValues;
+ for (Instruction::op_iterator OI = BonusInst->op_begin(),
+ OE = BonusInst->op_end(); OI != OE; ++OI) {
+ Value* V = *OI;
+ if (!isa<Constant>(V))
+ UsedValues.insert(V);
+ }
+
+ SmallVector<std::pair<Value*, unsigned>, 4> Worklist;
+ Worklist.push_back(std::make_pair(PBI->getOperand(0), 0));
+
+ // Walk up to four levels back up the use-def chain of the predecessor's
+ // terminator to see if all those values were used. The choice of four
+ // levels is arbitrary, to provide a compile-time-cost bound.
+ while (!Worklist.empty()) {
+ std::pair<Value*, unsigned> Pair = Worklist.back();
+ Worklist.pop_back();
+
+ if (Pair.second >= 4) continue;
+ UsedValues.erase(Pair.first);
+ if (UsedValues.empty()) break;
+
+ if (Instruction* I = dyn_cast<Instruction>(Pair.first)) {
+ for (Instruction::op_iterator OI = I->op_begin(), OE = I->op_end();
+ OI != OE; ++OI)
+ Worklist.push_back(std::make_pair(OI->get(), Pair.second+1));
+ }
+ }
+
+ if (!UsedValues.empty()) return false;
+ }
+
Instruction::BinaryOps Opc;
bool InvertPredCond = false;
PBI->setSuccessor(1, OldTrue);
}
+ // If we have a bonus inst, clone it into the predecessor block.
+ Instruction *NewBonus = 0;
+ if (BonusInst) {
+ NewBonus = BonusInst->clone();
+ PredBlock->getInstList().insert(PBI, NewBonus);
+ NewBonus->takeName(BonusInst);
+ BonusInst->setName(BonusInst->getName()+".old");
+ }
+
// Clone Cond into the predecessor basic block, and or/and the
// two conditions together.
Instruction *New = Cond->clone();
+ if (BonusInst) New->replaceUsesOfWith(BonusInst, NewBonus);
PredBlock->getInstList().insert(PBI, New);
New->takeName(Cond);
Cond->setName(New->getName()+".old");
// Okay, we're going to insert the PHI node. Since PBI is not the only
// predecessor, compute the PHI'd conditional value for all of the preds.
// Any predecessor where the condition is not computable we keep symbolic.
- for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
- if ((PBI = dyn_cast<BranchInst>((*PI)->getTerminator())) &&
+ for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
+ BasicBlock *P = *PI;
+ if ((PBI = dyn_cast<BranchInst>(P->getTerminator())) &&
PBI != BI && PBI->isConditional() &&
PBI->getCondition() == BI->getCondition() &&
PBI->getSuccessor(0) != PBI->getSuccessor(1)) {
bool CondIsTrue = PBI->getSuccessor(0) == BB;
NewPN->addIncoming(ConstantInt::get(Type::getInt1Ty(BB->getContext()),
- CondIsTrue), *PI);
+ CondIsTrue), P);
} else {
- NewPN->addIncoming(BI->getCondition(), *PI);
+ NewPN->addIncoming(BI->getCondition(), P);
}
+ }
BI->setCondition(NewPN);
return true;
assert(BB && BB->getParent() && "Block not embedded in function!");
assert(BB->getTerminator() && "Degenerate basic block encountered!");
- assert(&BB->getParent()->getEntryBlock() != BB &&
- "Can't Simplify entry block!");
- // Remove basic blocks that have no predecessors... or that just have themself
- // as a predecessor. These are unreachable.
- if (pred_begin(BB) == pred_end(BB) || BB->getSinglePredecessor() == BB) {
+ // Remove basic blocks that have no predecessors (except the entry block)...
+ // or that just have themself as a predecessor. These are unreachable.
+ if ((pred_begin(BB) == pred_end(BB) &&
+ &BB->getParent()->getEntryBlock() != BB) ||
+ BB->getSinglePredecessor() == BB) {
DEBUG(dbgs() << "Removing BB: \n" << *BB);
DeleteDeadBlock(BB);
return true;
SmallVector<BasicBlock*, 8> UncondBranchPreds;
SmallVector<BranchInst*, 8> CondBranchPreds;
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
- TerminatorInst *PTI = (*PI)->getTerminator();
+ BasicBlock *P = *PI;
+ TerminatorInst *PTI = P->getTerminator();
if (BranchInst *BI = dyn_cast<BranchInst>(PTI)) {
if (BI->isUnconditional())
- UncondBranchPreds.push_back(*PI);
+ UncondBranchPreds.push_back(P);
else
CondBranchPreds.push_back(BI);
}
Pred->getInstList().remove(II); // Take out of symbol table
// Insert the call now.
- SmallVector<Value*,8> Args(II->op_begin()+3, II->op_end());
+ SmallVector<Value*,8> Args(II->op_begin(), II->op_end()-3);
CallInst *CI = CallInst::Create(II->getCalledValue(),
Args.begin(), Args.end(),
II->getName(), BI);
while (isa<DbgInfoIntrinsic>(BBI))
++BBI;
if (BBI->isTerminator()) // Terminator is the only non-phi instruction!
- if (TryToSimplifyUncondBranchFromEmptyBlock(BB))
- return true;
+ if (BB != &BB->getParent()->getEntryBlock())
+ if (TryToSimplifyUncondBranchFromEmptyBlock(BB))
+ return true;
} else { // Conditional branch
if (isValueEqualityComparison(BI)) {
// switch.
if (BasicBlock *OnlyPred = BB->getSinglePredecessor())
if (SimplifyEqualityComparisonWithOnlyPredecessor(BI, OnlyPred))
- return SimplifyCFG(BB) || 1;
+ return SimplifyCFG(BB) | true;
// This block must be empty, except for the setcond inst, if it exists.
// Ignore dbg intrinsics.
// branches to us and one of our successors, fold the setcc into the
// predecessor and use logical operations to pick the right destination.
if (FoldBranchToCommonDest(BI))
- return SimplifyCFG(BB) | 1;
+ return SimplifyCFG(BB) | true;
// Scan predecessor blocks for conditional branches.
II->removeFromParent(); // Take out of symbol table
// Insert the call now...
- SmallVector<Value*, 8> Args(II->op_begin()+3, II->op_end());
+ SmallVector<Value*, 8> Args(II->op_begin(), II->op_end()-3);
CallInst *CI = CallInst::Create(II->getCalledValue(),
Args.begin(), Args.end(),
II->getName(), BI);
CI->setCallingConv(II->getCallingConv());
CI->setAttributes(II->getAttributes());
- // If the invoke produced a value, the Call does now instead.
+ // If the invoke produced a value, the call does now instead.
II->replaceAllUsesWith(CI);
delete II;
Changed = true;
}
// If this block is now dead, remove it.
- if (pred_begin(BB) == pred_end(BB)) {
+ if (pred_begin(BB) == pred_end(BB) &&
+ BB != &BB->getParent()->getEntryBlock()) {
// We know there are no successors, so just nuke the block.
M->getBasicBlockList().erase(BB);
return true;
}
}
+ } else if (IndirectBrInst *IBI =
+ dyn_cast<IndirectBrInst>(BB->getTerminator())) {
+ // Eliminate redundant destinations.
+ SmallPtrSet<Value *, 8> Succs;
+ for (unsigned i = 0, e = IBI->getNumDestinations(); i != e; ++i) {
+ BasicBlock *Dest = IBI->getDestination(i);
+ if (!Dest->hasAddressTaken() || !Succs.insert(Dest)) {
+ Dest->removePredecessor(BB);
+ IBI->removeDestination(i);
+ --i; --e;
+ Changed = true;
+ }
+ }
+
+ if (IBI->getNumDestinations() == 0) {
+ // If the indirectbr has no successors, change it to unreachable.
+ new UnreachableInst(IBI->getContext(), IBI);
+ IBI->eraseFromParent();
+ Changed = true;
+ } else if (IBI->getNumDestinations() == 1) {
+ // If the indirectbr has one successor, change it to a direct branch.
+ BranchInst::Create(IBI->getDestination(0), IBI);
+ IBI->eraseFromParent();
+ Changed = true;
+ }
}
// Merge basic blocks into their predecessor if there is only one distinct
// is a conditional branch, see if we can hoist any code from this block up
// into our predecessor.
pred_iterator PI(pred_begin(BB)), PE(pred_end(BB));
- BasicBlock *OnlyPred = *PI++;
- for (; PI != PE; ++PI) // Search all predecessors, see if they are all same
- if (*PI != OnlyPred) {
+ BasicBlock *OnlyPred = 0;
+ for (; PI != PE; ++PI) { // Search all predecessors, see if they are all same
+ if (!OnlyPred)
+ OnlyPred = *PI;
+ else if (*PI != OnlyPred) {
OnlyPred = 0; // There are multiple different predecessors...
break;
}
+ }
if (OnlyPred)
if (BranchInst *BI = dyn_cast<BranchInst>(OnlyPred->getTerminator()))
if (!TrueWhenEqual) std::swap(DefaultBB, EdgeBB);
// Convert pointer to int before we switch.
- if (isa<PointerType>(CompVal->getType())) {
+ if (CompVal->getType()->isPointerTy()) {
assert(TD && "Cannot switch on pointer without TargetData");
CompVal = new PtrToIntInst(CompVal,
TD->getIntPtrType(CompVal->getContext()),
/// eliminates unreachable basic blocks, and does other "peephole" optimization
/// of the CFG. It returns true if a modification was made.
///
-/// WARNING: The entry node of a function may not be simplified.
-///
bool llvm::SimplifyCFG(BasicBlock *BB, const TargetData *TD) {
return SimplifyCFGOpt(TD).run(BB);
}
projects / oota-llvm.git / blobdiff