#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Analysis/ConstantFolding.h"
+#include "llvm/Target/TargetData.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallVector.h"
STATISTIC(NumSpeculations, "Number of speculative executed instructions");
+namespace {
+class SimplifyCFGOpt {
+ const TargetData *const TD;
+
+ ConstantInt *GetConstantInt(Value *V);
+ Value *GatherConstantSetEQs(Value *V, std::vector<ConstantInt*> &Values);
+ Value *GatherConstantSetNEs(Value *V, std::vector<ConstantInt*> &Values);
+ bool GatherValueComparisons(Instruction *Cond, Value *&CompVal,
+ std::vector<ConstantInt*> &Values);
+ Value *isValueEqualityComparison(TerminatorInst *TI);
+ BasicBlock *GetValueEqualityComparisonCases(TerminatorInst *TI,
+ std::vector<std::pair<ConstantInt*, BasicBlock*> > &Cases);
+ bool SimplifyEqualityComparisonWithOnlyPredecessor(TerminatorInst *TI,
+ BasicBlock *Pred);
+ bool FoldValueComparisonIntoPredecessors(TerminatorInst *TI);
+
+public:
+ explicit SimplifyCFGOpt(const TargetData *td) : TD(td) {}
+ bool run(BasicBlock *BB);
+};
+}
+
/// SafeToMergeTerminators - Return true if it is safe to merge these two
/// terminator instructions together.
///
PN->addIncoming(PN->getIncomingValueForBlock(ExistPred), NewPred);
}
-/// CanPropagatePredecessorsForPHIs - Return true if we can fold BB, an
-/// almost-empty BB ending in an unconditional branch to Succ, into succ.
-///
-/// Assumption: Succ is the single successor for BB.
-///
-static bool CanPropagatePredecessorsForPHIs(BasicBlock *BB, BasicBlock *Succ) {
- assert(*succ_begin(BB) == Succ && "Succ is not successor of BB!");
-
- DEBUG(errs() << "Looking to fold " << BB->getName() << " into "
- << Succ->getName() << "\n");
- // Shortcut, if there is only a single predecessor it must be BB and merging
- // is always safe
- if (Succ->getSinglePredecessor()) return true;
-
- // Make a list of the predecessors of BB
- typedef SmallPtrSet<BasicBlock*, 16> BlockSet;
- BlockSet BBPreds(pred_begin(BB), pred_end(BB));
-
- // Use that list to make another list of common predecessors of BB and Succ
- BlockSet CommonPreds;
- for (pred_iterator PI = pred_begin(Succ), PE = pred_end(Succ);
- PI != PE; ++PI)
- if (BBPreds.count(*PI))
- CommonPreds.insert(*PI);
-
- // Shortcut, if there are no common predecessors, merging is always safe
- if (CommonPreds.empty())
- return true;
-
- // Look at all the phi nodes in Succ, to see if they present a conflict when
- // merging these blocks
- for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
- PHINode *PN = cast<PHINode>(I);
-
- // If the incoming value from BB is again a PHINode in
- // BB which has the same incoming value for *PI as PN does, we can
- // merge the phi nodes and then the blocks can still be merged
- PHINode *BBPN = dyn_cast<PHINode>(PN->getIncomingValueForBlock(BB));
- if (BBPN && BBPN->getParent() == BB) {
- for (BlockSet::iterator PI = CommonPreds.begin(), PE = CommonPreds.end();
- PI != PE; PI++) {
- if (BBPN->getIncomingValueForBlock(*PI)
- != PN->getIncomingValueForBlock(*PI)) {
- DEBUG(errs() << "Can't fold, phi node " << PN->getName() << " in "
- << Succ->getName() << " is conflicting with "
- << BBPN->getName() << " with regard to common predecessor "
- << (*PI)->getName() << "\n");
- return false;
- }
- }
- } else {
- Value* Val = PN->getIncomingValueForBlock(BB);
- for (BlockSet::iterator PI = CommonPreds.begin(), PE = CommonPreds.end();
- PI != PE; PI++) {
- // See if the incoming value for the common predecessor is equal to the
- // one for BB, in which case this phi node will not prevent the merging
- // of the block.
- if (Val != PN->getIncomingValueForBlock(*PI)) {
- DEBUG(errs() << "Can't fold, phi node " << PN->getName() << " in "
- << Succ->getName() << " is conflicting with regard to common "
- << "predecessor " << (*PI)->getName() << "\n");
- return false;
- }
- }
- }
- }
-
- return true;
-}
-
-/// TryToSimplifyUncondBranchFromEmptyBlock - BB contains an unconditional
-/// branch to Succ, and contains no instructions other than PHI nodes and the
-/// branch. If possible, eliminate BB.
-static bool TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB,
- BasicBlock *Succ) {
- // Check to see if merging these blocks would cause conflicts for any of the
- // phi nodes in BB or Succ. If not, we can safely merge.
- if (!CanPropagatePredecessorsForPHIs(BB, Succ)) return false;
-
- // Check for cases where Succ has multiple predecessors and a PHI node in BB
- // has uses which will not disappear when the PHI nodes are merged. It is
- // possible to handle such cases, but difficult: it requires checking whether
- // BB dominates Succ, which is non-trivial to calculate in the case where
- // Succ has multiple predecessors. Also, it requires checking whether
- // constructing the necessary self-referential PHI node doesn't intoduce any
- // conflicts; this isn't too difficult, but the previous code for doing this
- // was incorrect.
- //
- // Note that if this check finds a live use, BB dominates Succ, so BB is
- // something like a loop pre-header (or rarely, a part of an irreducible CFG);
- // folding the branch isn't profitable in that case anyway.
- if (!Succ->getSinglePredecessor()) {
- BasicBlock::iterator BBI = BB->begin();
- while (isa<PHINode>(*BBI)) {
- for (Value::use_iterator UI = BBI->use_begin(), E = BBI->use_end();
- UI != E; ++UI) {
- if (PHINode* PN = dyn_cast<PHINode>(*UI)) {
- if (PN->getIncomingBlock(UI) != BB)
- return false;
- } else {
- return false;
- }
- }
- ++BBI;
- }
- }
-
- DEBUG(errs() << "Killing Trivial BB: \n" << *BB);
-
- if (isa<PHINode>(Succ->begin())) {
- // If there is more than one pred of succ, and there are PHI nodes in
- // the successor, then we need to add incoming edges for the PHI nodes
- //
- const SmallVector<BasicBlock*, 16> BBPreds(pred_begin(BB), pred_end(BB));
-
- // Loop over all of the PHI nodes in the successor of BB.
- for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
- PHINode *PN = cast<PHINode>(I);
- Value *OldVal = PN->removeIncomingValue(BB, false);
- assert(OldVal && "No entry in PHI for Pred BB!");
-
- // If this incoming value is one of the PHI nodes in BB, the new entries
- // in the PHI node are the entries from the old PHI.
- if (isa<PHINode>(OldVal) && cast<PHINode>(OldVal)->getParent() == BB) {
- PHINode *OldValPN = cast<PHINode>(OldVal);
- for (unsigned i = 0, e = OldValPN->getNumIncomingValues(); i != e; ++i)
- // Note that, since we are merging phi nodes and BB and Succ might
- // have common predecessors, we could end up with a phi node with
- // identical incoming branches. This will be cleaned up later (and
- // will trigger asserts if we try to clean it up now, without also
- // simplifying the corresponding conditional branch).
- PN->addIncoming(OldValPN->getIncomingValue(i),
- OldValPN->getIncomingBlock(i));
- } else {
- // Add an incoming value for each of the new incoming values.
- for (unsigned i = 0, e = BBPreds.size(); i != e; ++i)
- PN->addIncoming(OldVal, BBPreds[i]);
- }
- }
- }
-
- while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
- if (Succ->getSinglePredecessor()) {
- // BB is the only predecessor of Succ, so Succ will end up with exactly
- // the same predecessors BB had.
- Succ->getInstList().splice(Succ->begin(),
- BB->getInstList(), BB->begin());
- } else {
- // We explicitly check for such uses in CanPropagatePredecessorsForPHIs.
- assert(PN->use_empty() && "There shouldn't be any uses here!");
- PN->eraseFromParent();
- }
- }
-
- // Everything that jumped to BB now goes to Succ.
- BB->replaceAllUsesWith(Succ);
- if (!Succ->hasName()) Succ->takeName(BB);
- BB->eraseFromParent(); // Delete the old basic block.
- return true;
-}
/// GetIfCondition - Given a basic block (BB) with two predecessors (and
/// presumably PHI nodes in it), check to see if the merge at this block is due
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;
return true;
}
+/// GetConstantInt - Extract ConstantInt from value, looking through IntToPtr
+/// and PointerNullValue. Return NULL if value is not a constant int.
+ConstantInt *SimplifyCFGOpt::GetConstantInt(Value *V) {
+ // Normal constant int.
+ ConstantInt *CI = dyn_cast<ConstantInt>(V);
+ if (CI || !TD || !isa<Constant>(V) || !V->getType()->isPointerTy())
+ return CI;
+
+ // This is some kind of pointer constant. Turn it into a pointer-sized
+ // ConstantInt if possible.
+ const IntegerType *PtrTy = TD->getIntPtrType(V->getContext());
+
+ // Null pointer means 0, see SelectionDAGBuilder::getValue(const Value*).
+ if (isa<ConstantPointerNull>(V))
+ return ConstantInt::get(PtrTy, 0);
+
+ // IntToPtr const int.
+ if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
+ if (CE->getOpcode() == Instruction::IntToPtr)
+ if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(0))) {
+ // The constant is very likely to have the right type already.
+ if (CI->getType() == PtrTy)
+ return CI;
+ else
+ return cast<ConstantInt>
+ (ConstantExpr::getIntegerCast(CI, PtrTy, /*isSigned=*/false));
+ }
+ return 0;
+}
+
/// GatherConstantSetEQs - Given a potentially 'or'd together collection of
/// icmp_eq instructions that compare a value against a constant, return the
/// value being compared, and stick the constant into the Values vector.
-static Value *GatherConstantSetEQs(Value *V, std::vector<ConstantInt*> &Values){
+Value *SimplifyCFGOpt::
+GatherConstantSetEQs(Value *V, std::vector<ConstantInt*> &Values) {
if (Instruction *Inst = dyn_cast<Instruction>(V)) {
if (Inst->getOpcode() == Instruction::ICmp &&
cast<ICmpInst>(Inst)->getPredicate() == ICmpInst::ICMP_EQ) {
- if (ConstantInt *C = dyn_cast<ConstantInt>(Inst->getOperand(1))) {
+ if (ConstantInt *C = GetConstantInt(Inst->getOperand(1))) {
Values.push_back(C);
return Inst->getOperand(0);
- } else if (ConstantInt *C = dyn_cast<ConstantInt>(Inst->getOperand(0))) {
+ } else if (ConstantInt *C = GetConstantInt(Inst->getOperand(0))) {
Values.push_back(C);
return Inst->getOperand(1);
}
/// GatherConstantSetNEs - Given a potentially 'and'd together collection of
/// setne instructions that compare a value against a constant, return the value
/// being compared, and stick the constant into the Values vector.
-static Value *GatherConstantSetNEs(Value *V, std::vector<ConstantInt*> &Values){
+Value *SimplifyCFGOpt::
+GatherConstantSetNEs(Value *V, std::vector<ConstantInt*> &Values) {
if (Instruction *Inst = dyn_cast<Instruction>(V)) {
if (Inst->getOpcode() == Instruction::ICmp &&
cast<ICmpInst>(Inst)->getPredicate() == ICmpInst::ICMP_NE) {
- if (ConstantInt *C = dyn_cast<ConstantInt>(Inst->getOperand(1))) {
+ if (ConstantInt *C = GetConstantInt(Inst->getOperand(1))) {
Values.push_back(C);
return Inst->getOperand(0);
- } else if (ConstantInt *C = dyn_cast<ConstantInt>(Inst->getOperand(0))) {
+ } else if (ConstantInt *C = GetConstantInt(Inst->getOperand(0))) {
Values.push_back(C);
return Inst->getOperand(1);
}
/// GatherValueComparisons - If the specified Cond is an 'and' or 'or' of a
/// bunch of comparisons of one value against constants, return the value and
/// the constants being compared.
-static bool GatherValueComparisons(Instruction *Cond, Value *&CompVal,
- std::vector<ConstantInt*> &Values) {
+bool SimplifyCFGOpt::GatherValueComparisons(Instruction *Cond, Value *&CompVal,
+ std::vector<ConstantInt*> &Values) {
if (Cond->getOpcode() == Instruction::Or) {
CompVal = GatherConstantSetEQs(Cond, Values);
/// isValueEqualityComparison - Return true if the specified terminator checks
/// to see if a value is equal to constant integer value.
-static Value *isValueEqualityComparison(TerminatorInst *TI) {
+Value *SimplifyCFGOpt::isValueEqualityComparison(TerminatorInst *TI) {
+ Value *CV = 0;
if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
// Do not permit merging of large switch instructions into their
// predecessors unless there is only one predecessor.
- if (SI->getNumSuccessors() * std::distance(pred_begin(SI->getParent()),
- pred_end(SI->getParent())) > 128)
- return 0;
-
- return SI->getCondition();
- }
- if (BranchInst *BI = dyn_cast<BranchInst>(TI))
+ if (SI->getNumSuccessors()*std::distance(pred_begin(SI->getParent()),
+ pred_end(SI->getParent())) <= 128)
+ CV = SI->getCondition();
+ } else if (BranchInst *BI = dyn_cast<BranchInst>(TI))
if (BI->isConditional() && BI->getCondition()->hasOneUse())
if (ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition()))
if ((ICI->getPredicate() == ICmpInst::ICMP_EQ ||
ICI->getPredicate() == ICmpInst::ICMP_NE) &&
- isa<ConstantInt>(ICI->getOperand(1)))
- return ICI->getOperand(0);
- return 0;
+ GetConstantInt(ICI->getOperand(1)))
+ CV = ICI->getOperand(0);
+
+ // Unwrap any lossless ptrtoint cast.
+ if (TD && CV && CV->getType() == TD->getIntPtrType(CV->getContext()))
+ if (PtrToIntInst *PTII = dyn_cast<PtrToIntInst>(CV))
+ CV = PTII->getOperand(0);
+ return CV;
}
/// GetValueEqualityComparisonCases - Given a value comparison instruction,
/// decode all of the 'cases' that it represents and return the 'default' block.
-static BasicBlock *
+BasicBlock *SimplifyCFGOpt::
GetValueEqualityComparisonCases(TerminatorInst *TI,
std::vector<std::pair<ConstantInt*,
BasicBlock*> > &Cases) {
BranchInst *BI = cast<BranchInst>(TI);
ICmpInst *ICI = cast<ICmpInst>(BI->getCondition());
- Cases.push_back(std::make_pair(cast<ConstantInt>(ICI->getOperand(1)),
+ Cases.push_back(std::make_pair(GetConstantInt(ICI->getOperand(1)),
BI->getSuccessor(ICI->getPredicate() ==
ICmpInst::ICMP_NE)));
return BI->getSuccessor(ICI->getPredicate() == ICmpInst::ICMP_EQ);
/// comparison with the same value, and if that comparison determines the
/// outcome of this comparison. If so, simplify TI. This does a very limited
/// form of jump threading.
-static bool SimplifyEqualityComparisonWithOnlyPredecessor(TerminatorInst *TI,
- BasicBlock *Pred) {
+bool SimplifyCFGOpt::
+SimplifyEqualityComparisonWithOnlyPredecessor(TerminatorInst *TI,
+ BasicBlock *Pred) {
Value *PredVal = isValueEqualityComparison(Pred->getTerminator());
if (!PredVal) return false; // Not a value comparison in predecessor.
// Remove PHI node entries for the dead edge.
ThisCases[0].second->removePredecessor(TI->getParent());
- DEBUG(errs() << "Threading pred instr: " << *Pred->getTerminator()
+ DEBUG(dbgs() << "Threading pred instr: " << *Pred->getTerminator()
<< "Through successor TI: " << *TI << "Leaving: " << *NI << "\n");
EraseTerminatorInstAndDCECond(TI);
for (unsigned i = 0, e = PredCases.size(); i != e; ++i)
DeadCases.insert(PredCases[i].first);
- DEBUG(errs() << "Threading pred instr: " << *Pred->getTerminator()
+ DEBUG(dbgs() << "Threading pred instr: " << *Pred->getTerminator()
<< "Through successor TI: " << *TI);
for (unsigned i = SI->getNumCases()-1; i != 0; --i)
SI->removeCase(i);
}
- DEBUG(errs() << "Leaving: " << *TI << "\n");
+ DEBUG(dbgs() << "Leaving: " << *TI << "\n");
return true;
}
}
Instruction *NI = BranchInst::Create(TheRealDest, TI);
(void) NI;
- DEBUG(errs() << "Threading pred instr: " << *Pred->getTerminator()
+ DEBUG(dbgs() << "Threading pred instr: " << *Pred->getTerminator()
<< "Through successor TI: " << *TI << "Leaving: " << *NI << "\n");
EraseTerminatorInstAndDCECond(TI);
/// equality comparison instruction (either a switch or a branch on "X == c").
/// See if any of the predecessors of the terminator block are value comparisons
/// on the same value. If so, and if safe to do so, fold them together.
-static bool FoldValueComparisonIntoPredecessors(TerminatorInst *TI) {
+bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(TerminatorInst *TI) {
BasicBlock *BB = TI->getParent();
Value *CV = isValueEqualityComparison(TI); // CondVal
assert(CV && "Not a comparison?");
for (unsigned i = 0, e = NewSuccessors.size(); i != e; ++i)
AddPredecessorToBlock(NewSuccessors[i], Pred, BB);
+ // Convert pointer to int before we switch.
+ if (CV->getType()->isPointerTy()) {
+ assert(TD && "Cannot switch on pointer without TargetData");
+ CV = new PtrToIntInst(CV, TD->getIntPtrType(CV->getContext()),
+ "magicptr", PTI);
+ }
+
// Now that the successors are updated, create the new Switch instruction.
SwitchInst *NewSI = SwitchInst::Create(CV, PredDefault,
PredCases.size(), PTI);
// Okay, it is safe to hoist the terminator.
Instruction *NT = I1->clone();
BIParent->getInstList().insert(BI, NT);
- if (NT->getType() != Type::getVoidTy(BB1->getContext())) {
+ if (!NT->getType()->isVoidTy()) {
I1->replaceAllUsesWith(NT);
I2->replaceAllUsesWith(NT);
NT->takeName(I1);
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);
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
ConstantInt *CB;
if ((CB = dyn_cast<ConstantInt>(PN->getIncomingValue(i))) &&
- CB->getType() == Type::getInt1Ty(BB->getContext())) {
+ CB->getType()->isIntegerTy(1)) {
// Okay, we now know that all edges from PredBB should be revectored to
// branch to RealDest.
BasicBlock *PredBB = PN->getIncomingBlock(i);
}
// Check for trivial simplification.
- if (Constant *C = ConstantFoldInstruction(N, BB->getContext())) {
+ if (Constant *C = ConstantFoldInstruction(N)) {
TranslateMap[BBI] = C;
delete N; // Constant folded away, don't need actual inst
} else {
if (NumPhis > 2)
return false;
- DEBUG(errs() << "FOUND IF CONDITION! " << *IfCond << " T: "
+ DEBUG(dbgs() << "FOUND IF CONDITION! " << *IfCond << " T: "
<< IfTrue->getName() << " F: " << IfFalse->getName() << "\n");
// Loop over the PHI's seeing if we can promote them all to select
ReturnInst::Create(BI->getContext(), TrueValue, BI);
(void) RI;
- DEBUG(errs() << "\nCHANGING BRANCH TO TWO RETURNS INTO SELECT:"
+ DEBUG(dbgs() << "\nCHANGING BRANCH TO TWO RETURNS INTO SELECT:"
<< "\n " << *BI << "NewRet = " << *RI
<< "TRUEBLOCK: " << *TrueSucc << "FALSEBLOCK: "<< *FalseSucc);
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;
else
continue;
- DEBUG(errs() << "FOLDING BRANCH TO COMMON DEST:\n" << *PBI << *BB);
+ DEBUG(dbgs() << "FOLDING BRANCH TO COMMON DEST:\n" << *PBI << *BB);
// If we need to invert the condition in the pred block to match, do so now.
if (InvertPredCond) {
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;
// Finally, if everything is ok, fold the branches to logical ops.
BasicBlock *OtherDest = BI->getSuccessor(BIOp ^ 1);
- DEBUG(errs() << "FOLDING BRs:" << *PBI->getParent()
+ DEBUG(dbgs() << "FOLDING BRs:" << *PBI->getParent()
<< "AND: " << *BI->getParent());
OtherDest = InfLoopBlock;
}
- DEBUG(errs() << *PBI->getParent()->getParent());
+ DEBUG(dbgs() << *PBI->getParent()->getParent());
// BI may have other predecessors. Because of this, we leave
// it alone, but modify PBI.
}
}
- DEBUG(errs() << "INTO: " << *PBI->getParent());
- DEBUG(errs() << *PBI->getParent()->getParent());
+ DEBUG(dbgs() << "INTO: " << *PBI->getParent());
+ DEBUG(dbgs() << *PBI->getParent()->getParent());
// This basic block is probably dead. We know it has at least
// one fewer predecessor.
return true;
}
-/// EliminateDuplicatePHINodes - Check for and eliminate duplicate PHI
-/// nodes in this block. This doesn't try to be clever about PHI nodes
-/// which differ only in the order of the incoming values, but instcombine
-/// orders them so it usually won't matter.
-static bool EliminateDuplicatePHINodes(BasicBlock *BB) {
- bool Changed = false;
-
- // Map from PHI hash values to PHI nodes. If multiple PHIs have
- // the same hash value, the element is the first PHI in the
- // linked list in CollisionMap.
- DenseMap<uintptr_t, PHINode *> HashMap;
-
- // Maintain linked lists of PHI nodes with common hash values.
- DenseMap<PHINode *, PHINode *> CollisionMap;
-
- // Examine each PHI.
- for (BasicBlock::iterator I = BB->begin();
- PHINode *PN = dyn_cast<PHINode>(I++); ) {
- // Compute a hash value on the operands. Instcombine will likely have sorted
- // them, which helps expose duplicates, but we have to check all the
- // operands to be safe in case instcombine hasn't run.
- uintptr_t Hash = 0;
- for (User::op_iterator I = PN->op_begin(), E = PN->op_end(); I != E; ++I) {
- // This hash algorithm is quite weak as hash functions go, but it seems
- // to do a good enough job for this particular purpose, and is very quick.
- Hash ^= reinterpret_cast<uintptr_t>(static_cast<Value *>(*I));
- Hash = (Hash << 7) | (Hash >> (sizeof(uintptr_t) * CHAR_BIT - 7));
- }
- // If we've never seen this hash value before, it's a unique PHI.
- std::pair<DenseMap<uintptr_t, PHINode *>::iterator, bool> Pair =
- HashMap.insert(std::make_pair(Hash, PN));
- if (Pair.second) continue;
- // Otherwise it's either a duplicate or a hash collision.
- for (PHINode *OtherPN = Pair.first->second; ; ) {
- if (OtherPN->isIdenticalTo(PN)) {
- // A duplicate. Replace this PHI with its duplicate.
- PN->replaceAllUsesWith(OtherPN);
- PN->eraseFromParent();
- Changed = true;
- break;
- }
- // A non-duplicate hash collision.
- DenseMap<PHINode *, PHINode *>::iterator I = CollisionMap.find(OtherPN);
- if (I == CollisionMap.end()) {
- // Set this PHI to be the head of the linked list of colliding PHIs.
- PHINode *Old = Pair.first->second;
- Pair.first->second = PN;
- CollisionMap[PN] = Old;
- break;
- }
- // Procede to the next PHI in the list.
- OtherPN = I->second;
- }
- }
-
- return Changed;
-}
-
-/// SimplifyCFG - This function is used to do simplification of a CFG. For
-/// example, it adjusts branches to branches to eliminate the extra hop, it
-/// 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) {
+bool SimplifyCFGOpt::run(BasicBlock *BB) {
bool Changed = false;
Function *M = BB->getParent();
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) {
- DEBUG(errs() << "Removing BB: \n" << *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);
}
if (!UncondBranchPreds.empty()) {
while (!UncondBranchPreds.empty()) {
BasicBlock *Pred = UncondBranchPreds.pop_back_val();
- DEBUG(errs() << "FOLDING: " << *BB
+ DEBUG(dbgs() << "FOLDING: " << *BB
<< "INTO UNCOND BRANCH PRED: " << *Pred);
Instruction *UncondBranch = Pred->getTerminator();
// Clone the return and add it to the end of the predecessor.
Instruction *NewRet = RI->clone();
Pred->getInstList().push_back(NewRet);
- BasicBlock::iterator BBI = RI;
- if (BBI != BB->begin()) {
- // Move region end info into the predecessor.
- if (DbgRegionEndInst *DREI = dyn_cast<DbgRegionEndInst>(--BBI))
- DREI->moveBefore(NewRet);
- }
-
// If the return instruction returns a value, and if the value was a
// PHI node in "BB", propagate the right value into the return.
for (User::op_iterator i = NewRet->op_begin(), e = NewRet->op_end();
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);
if (BI->isUnconditional()) {
BasicBlock::iterator BBI = BB->getFirstNonPHI();
- BasicBlock *Succ = BI->getSuccessor(0);
// Ignore dbg intrinsics.
while (isa<DbgInfoIntrinsic>(BBI))
++BBI;
- if (BBI->isTerminator() && // Terminator is the only non-phi instruction!
- Succ != BB) // Don't hurt infinite loops!
- if (TryToSimplifyUncondBranchFromEmptyBlock(BB, Succ))
- return true;
+ if (BBI->isTerminator()) // Terminator is the only non-phi instruction!
+ 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()))
Value *CompVal = 0;
std::vector<ConstantInt*> Values;
bool TrueWhenEqual = GatherValueComparisons(Cond, CompVal, Values);
- if (CompVal && CompVal->getType()->isInteger()) {
+ if (CompVal) {
// There might be duplicate constants in the list, which the switch
// instruction can't handle, remove them now.
std::sort(Values.begin(), Values.end(), ConstantIntOrdering());
BasicBlock *EdgeBB = BI->getSuccessor(0);
if (!TrueWhenEqual) std::swap(DefaultBB, EdgeBB);
+ // 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);
return Changed;
}
+
+/// SimplifyCFG - This function is used to do simplification of a CFG. For
+/// example, it adjusts branches to branches to eliminate the extra hop, it
+/// eliminates unreachable basic blocks, and does other "peephole" optimization
+/// of the CFG. It returns true if a modification was made.
+///
+bool llvm::SimplifyCFG(BasicBlock *BB, const TargetData *TD) {
+ return SimplifyCFGOpt(TD).run(BB);
+}
projects / oota-llvm.git / blobdiff