#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Constants.h"
#include "llvm/Instructions.h"
+#include "llvm/IntrinsicInst.h"
#include "llvm/Type.h"
#include "llvm/DerivedTypes.h"
+#include "llvm/GlobalVariable.h"
#include "llvm/Support/CFG.h"
#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"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.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.
///
succ_end(ExistPred) && "ExistPred is not a predecessor of Succ!");
if (!isa<PHINode>(Succ->begin())) return; // Quick exit if nothing to do
- for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
- PHINode *PN = cast<PHINode>(I);
- Value *V = PN->getIncomingValueForBlock(ExistPred);
- PN->addIncoming(V, 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!");
-
- DOUT << "Looking to fold " << BB->getNameStart() << " into "
- << Succ->getNameStart() << "\n";
- // Shortcut, if there is only a single predecessor is must be BB and merging
- // is always safe
- if (Succ->getSinglePredecessor()) return true;
-
- typedef SmallPtrSet<Instruction*, 16> InstrSet;
- InstrSet BBPHIs;
-
- // Make a list of all phi nodes in BB
- BasicBlock::iterator BBI = BB->begin();
- while (isa<PHINode>(*BBI)) BBPHIs.insert(BBI++);
-
- // 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.begin() == CommonPreds.end())
- 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)) {
- DOUT << "Can't fold, phi node " << *PN->getNameStart() << " in "
- << Succ->getNameStart() << " is conflicting with "
- << BBPN->getNameStart() << " with regard to common predecessor "
- << (*PI)->getNameStart() << "\n";
- return false;
- }
- }
- // Remove this phinode from the list of phis in BB, since it has been
- // handled.
- BBPHIs.erase(BBPN);
- } 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)) {
- DOUT << "Can't fold, phi node " << *PN->getNameStart() << " in "
- << Succ->getNameStart() << " is conflicting with regard to common "
- << "predecessor " << (*PI)->getNameStart() << "\n";
- return false;
- }
- }
- }
- }
-
- // If there are any other phi nodes in BB that don't have a phi node in Succ
- // to merge with, they must be moved to Succ completely. However, for any
- // predecessors of Succ, branches will be added to the phi node that just
- // point to itself. So, for any common predecessors, this must not cause
- // conflicts.
- for (InstrSet::iterator I = BBPHIs.begin(), E = BBPHIs.end();
- I != E; I++) {
- PHINode *PN = cast<PHINode>(*I);
- for (BlockSet::iterator PI = CommonPreds.begin(), PE = CommonPreds.end();
- PI != PE; PI++)
- if (PN->getIncomingValueForBlock(*PI) != PN) {
- DOUT << "Can't fold, phi node " << *PN->getNameStart() << " in "
- << BB->getNameStart() << " is conflicting with regard to common "
- << "predecessor " << (*PI)->getNameStart() << "\n";
- return false;
- }
- }
-
- return true;
+ PHINode *PN;
+ for (BasicBlock::iterator I = Succ->begin();
+ (PN = dyn_cast<PHINode>(I)); ++I)
+ PN->addIncoming(PN->getIncomingValueForBlock(ExistPred), NewPred);
}
-/// 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;
-
- DOUT << "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]);
- }
- }
- }
-
- if (isa<PHINode>(&BB->front())) {
- SmallVector<BasicBlock*, 16>
- OldSuccPreds(pred_begin(Succ), pred_end(Succ));
-
- // Move all PHI nodes in BB to Succ if they are alive, otherwise
- // delete them.
- while (PHINode *PN = dyn_cast<PHINode>(&BB->front()))
- if (PN->use_empty()) {
- // Just remove the dead phi. This happens if Succ's PHIs were the only
- // users of the PHI nodes.
- PN->eraseFromParent();
- } else {
- // The instruction is alive, so this means that BB must dominate all
- // predecessors of Succ (Since all uses of the PN are after its
- // definition, so in Succ or a block dominated by Succ. If a predecessor
- // of Succ would not be dominated by BB, PN would violate the def before
- // use SSA demand). Therefore, we can simply move the phi node to the
- // next block.
- Succ->getInstList().splice(Succ->begin(),
- BB->getInstList(), BB->begin());
-
- // We need to add new entries for the PHI node to account for
- // predecessors of Succ that the PHI node does not take into
- // account. At this point, since we know that BB dominated succ and all
- // of its predecessors, this means that we should any newly added
- // incoming edges should use the PHI node itself as the value for these
- // edges, because they are loop back edges.
- for (unsigned i = 0, e = OldSuccPreds.size(); i != e; ++i)
- if (OldSuccPreds[i] != BB)
- PN->addIncoming(PN, OldSuccPreds[i]);
- }
- }
-
- // 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
return 0;
}
-
-// If we have a merge point of an "if condition" as accepted above, return true
-// if the specified value dominates the block. We don't handle the true
-// generality of domination here, just a special case which works well enough
-// for us.
-//
-// If AggressiveInsts is non-null, and if V does not dominate BB, we check to
-// see if V (which must be an instruction) is cheap to compute and is
-// non-trapping. If both are true, the instruction is inserted into the set and
-// true is returned.
+/// DominatesMergePoint - If we have a merge point of an "if condition" as
+/// accepted above, return true if the specified value dominates the block. We
+/// don't handle the true generality of domination here, just a special case
+/// which works well enough for us.
+///
+/// If AggressiveInsts is non-null, and if V does not dominate BB, we check to
+/// see if V (which must be an instruction) is cheap to compute and is
+/// non-trapping. If both are true, the instruction is inserted into the set
+/// and true is returned.
static bool DominatesMergePoint(Value *V, BasicBlock *BB,
std::set<Instruction*> *AggressiveInsts) {
Instruction *I = dyn_cast<Instruction>(V);
// Okay, it looks like the instruction IS in the "condition". Check to
// see if its 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;
+
switch (I->getOpcode()) {
default: return false; // Cannot hoist this out safely.
- case Instruction::Load:
- // We can hoist loads that are non-volatile and obviously cannot trap.
- if (cast<LoadInst>(I)->isVolatile())
- return false;
- if (!isa<AllocaInst>(I->getOperand(0)) &&
- !isa<Constant>(I->getOperand(0)))
- return false;
-
- // Finally, we have to check to make sure there are no instructions
- // before the load in its basic block, as we are going to hoist the loop
- // out to its predecessor.
- if (PBB->begin() != BasicBlock::iterator(I))
+ case Instruction::Load: {
+ // We have to check to make sure there are no instructions before the
+ // load in its basic block, as we are going to hoist the loop out to
+ // its predecessor.
+ BasicBlock::iterator IP = PBB->begin();
+ while (isa<DbgInfoIntrinsic>(IP))
+ IP++;
+ if (IP != BasicBlock::iterator(I))
return false;
break;
+ }
case Instruction::Add:
case Instruction::Sub:
case Instruction::And:
case Instruction::LShr:
case Instruction::AShr:
case Instruction::ICmp:
- case Instruction::FCmp:
- if (I->getOperand(0)->getType()->isFPOrFPVector())
- return false; // FP arithmetic might trap.
break; // These are all cheap and non-trapping instructions.
}
return true;
}
-// 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){
+/// 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) || !isa<PointerType>(V->getType()))
+ 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.
+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);
}
return 0;
}
-// 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){
+/// 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.
+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);
}
return 0;
}
-
-
/// 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);
return false;
}
-/// ErasePossiblyDeadInstructionTree - If the specified instruction is dead and
-/// has no side effects, nuke it. If it uses any instructions that become dead
-/// because the instruction is now gone, nuke them too.
-static void ErasePossiblyDeadInstructionTree(Instruction *I) {
- if (!isInstructionTriviallyDead(I)) return;
-
- SmallVector<Instruction*, 16> InstrsToInspect;
- InstrsToInspect.push_back(I);
-
- while (!InstrsToInspect.empty()) {
- I = InstrsToInspect.back();
- InstrsToInspect.pop_back();
-
- if (!isInstructionTriviallyDead(I)) continue;
-
- // If I is in the work list multiple times, remove previous instances.
- for (unsigned i = 0, e = InstrsToInspect.size(); i != e; ++i)
- if (InstrsToInspect[i] == I) {
- InstrsToInspect.erase(InstrsToInspect.begin()+i);
- --i, --e;
- }
-
- // Add operands of dead instruction to worklist.
- for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i)
- if (Instruction *OpI = dyn_cast<Instruction>(*i))
- InstrsToInspect.push_back(OpI);
-
- // Remove dead instruction.
- I->eraseFromParent();
+static void EraseTerminatorInstAndDCECond(TerminatorInst *TI) {
+ Instruction* Cond = 0;
+ if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
+ Cond = dyn_cast<Instruction>(SI->getCondition());
+ } else if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
+ if (BI->isConditional())
+ Cond = dyn_cast<Instruction>(BI->getCondition());
}
+
+ TI->eraseFromParent();
+ if (Cond) RecursivelyDeleteTriviallyDeadInstructions(Cond);
}
-// isValueEqualityComparison - Return true if the specified terminator checks to
-// see if a value is equal to constant integer value.
-static Value *isValueEqualityComparison(TerminatorInst *TI) {
+/// isValueEqualityComparison - Return true if the specified terminator checks
+/// to see if a value is equal to constant integer value.
+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;
}
-// Given a value comparison instruction, decode all of the 'cases' that it
-// represents and return the 'default' block.
-static BasicBlock *
+/// GetValueEqualityComparisonCases - Given a value comparison instruction,
+/// decode all of the 'cases' that it represents and return the 'default' block.
+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);
}
-// EliminateBlockCases - Given a vector of bb/value pairs, remove any entries
-// in the list that match the specified block.
+/// EliminateBlockCases - Given a vector of bb/value pairs, remove any entries
+/// in the list that match the specified block.
static void EliminateBlockCases(BasicBlock *BB,
std::vector<std::pair<ConstantInt*, BasicBlock*> > &Cases) {
for (unsigned i = 0, e = Cases.size(); i != e; ++i)
}
}
-// ValuesOverlap - Return true if there are any keys in C1 that exist in C2 as
-// well.
+/// ValuesOverlap - Return true if there are any keys in C1 that exist in C2 as
+/// well.
static bool
ValuesOverlap(std::vector<std::pair<ConstantInt*, BasicBlock*> > &C1,
std::vector<std::pair<ConstantInt*, BasicBlock*> > &C2) {
return false;
}
-// SimplifyEqualityComparisonWithOnlyPredecessor - If TI is known to be a
-// terminator instruction and its block is known to only have a single
-// predecessor block, check to see if that predecessor is also a value
-// 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) {
+/// SimplifyEqualityComparisonWithOnlyPredecessor - If TI is known to be a
+/// terminator instruction and its block is known to only have a single
+/// predecessor block, check to see if that predecessor is also a value
+/// 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.
+bool SimplifyCFGOpt::
+SimplifyEqualityComparisonWithOnlyPredecessor(TerminatorInst *TI,
+ BasicBlock *Pred) {
Value *PredVal = isValueEqualityComparison(Pred->getTerminator());
if (!PredVal) return false; // Not a value comparison in predecessor.
// PredCases. If there are any cases in ThisCases that are in PredCases, we
// can simplify TI.
if (ValuesOverlap(PredCases, ThisCases)) {
- if (BranchInst *BTI = dyn_cast<BranchInst>(TI)) {
+ if (isa<BranchInst>(TI)) {
// Okay, one of the successors of this condbr is dead. Convert it to a
// uncond br.
assert(ThisCases.size() == 1 && "Branch can only have one case!");
- Value *Cond = BTI->getCondition();
// Insert the new branch.
Instruction *NI = BranchInst::Create(ThisDef, TI);
+ (void) NI;
// Remove PHI node entries for the dead edge.
ThisCases[0].second->removePredecessor(TI->getParent());
- DOUT << "Threading pred instr: " << *Pred->getTerminator()
- << "Through successor TI: " << *TI << "Leaving: " << *NI << "\n";
+ DEBUG(dbgs() << "Threading pred instr: " << *Pred->getTerminator()
+ << "Through successor TI: " << *TI << "Leaving: " << *NI << "\n");
- TI->eraseFromParent(); // Nuke the old one.
- // If condition is now dead, nuke it.
- if (Instruction *CondI = dyn_cast<Instruction>(Cond))
- ErasePossiblyDeadInstructionTree(CondI);
+ EraseTerminatorInstAndDCECond(TI);
return true;
} else {
for (unsigned i = 0, e = PredCases.size(); i != e; ++i)
DeadCases.insert(PredCases[i].first);
- DOUT << "Threading pred instr: " << *Pred->getTerminator()
- << "Through successor TI: " << *TI;
+ DEBUG(dbgs() << "Threading pred instr: " << *Pred->getTerminator()
+ << "Through successor TI: " << *TI);
for (unsigned i = SI->getNumCases()-1; i != 0; --i)
if (DeadCases.count(SI->getCaseValue(i))) {
SI->removeCase(i);
}
- DOUT << "Leaving: " << *TI << "\n";
+ DEBUG(dbgs() << "Leaving: " << *TI << "\n");
return true;
}
}
// Insert the new branch.
Instruction *NI = BranchInst::Create(TheRealDest, TI);
+ (void) NI;
- DOUT << "Threading pred instr: " << *Pred->getTerminator()
- << "Through successor TI: " << *TI << "Leaving: " << *NI << "\n";
- Instruction *Cond = 0;
- if (BranchInst *BI = dyn_cast<BranchInst>(TI))
- Cond = dyn_cast<Instruction>(BI->getCondition());
- TI->eraseFromParent(); // Nuke the old one.
+ DEBUG(dbgs() << "Threading pred instr: " << *Pred->getTerminator()
+ << "Through successor TI: " << *TI << "Leaving: " << *NI << "\n");
- if (Cond) ErasePossiblyDeadInstructionTree(Cond);
+ EraseTerminatorInstAndDCECond(TI);
return true;
}
return false;
}
-// FoldValueComparisonIntoPredecessors - The specified terminator is a value
-// 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) {
+namespace {
+ /// ConstantIntOrdering - This class implements a stable ordering of constant
+ /// integers that does not depend on their address. This is important for
+ /// applications that sort ConstantInt's to ensure uniqueness.
+ struct ConstantIntOrdering {
+ bool operator()(const ConstantInt *LHS, const ConstantInt *RHS) const {
+ return LHS->getValue().ult(RHS->getValue());
+ }
+ };
+}
+
+/// FoldValueComparisonIntoPredecessors - The specified terminator is a value
+/// 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.
+bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(TerminatorInst *TI) {
BasicBlock *BB = TI->getParent();
Value *CV = isValueEqualityComparison(TI); // CondVal
assert(CV && "Not a comparison?");
SmallVector<BasicBlock*, 16> Preds(pred_begin(BB), pred_end(BB));
while (!Preds.empty()) {
- BasicBlock *Pred = Preds.back();
- Preds.pop_back();
+ BasicBlock *Pred = Preds.pop_back_val();
// See if the predecessor is a comparison with the same value.
TerminatorInst *PTI = Pred->getTerminator();
if (PredDefault == BB) {
// If this is the default destination from PTI, only the edges in TI
// that don't occur in PTI, or that branch to BB will be activated.
- std::set<ConstantInt*> PTIHandled;
+ std::set<ConstantInt*, ConstantIntOrdering> PTIHandled;
for (unsigned i = 0, e = PredCases.size(); i != e; ++i)
if (PredCases[i].second != BB)
PTIHandled.insert(PredCases[i].first);
// If this is not the default destination from PSI, only the edges
// in SI that occur in PSI with a destination of BB will be
// activated.
- std::set<ConstantInt*> PTIHandled;
+ std::set<ConstantInt*, ConstantIntOrdering> PTIHandled;
for (unsigned i = 0, e = PredCases.size(); i != e; ++i)
if (PredCases[i].second == BB) {
PTIHandled.insert(PredCases[i].first);
// If there are any constants vectored to BB that TI doesn't handle,
// they must go to the default destination of TI.
- for (std::set<ConstantInt*>::iterator I = PTIHandled.begin(),
+ for (std::set<ConstantInt*, ConstantIntOrdering>::iterator I =
+ PTIHandled.begin(),
E = PTIHandled.end(); I != E; ++I) {
PredCases.push_back(std::make_pair(*I, BBDefault));
NewSuccessors.push_back(BBDefault);
for (unsigned i = 0, e = NewSuccessors.size(); i != e; ++i)
AddPredecessorToBlock(NewSuccessors[i], Pred, BB);
+ // Convert pointer to int before we switch.
+ if (isa<PointerType>(CV->getType())) {
+ 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);
for (unsigned i = 0, e = PredCases.size(); i != e; ++i)
NewSI->addCase(PredCases[i].first, PredCases[i].second);
- Instruction *DeadCond = 0;
- if (BranchInst *BI = dyn_cast<BranchInst>(PTI))
- // If PTI is a branch, remember the condition.
- DeadCond = dyn_cast<Instruction>(BI->getCondition());
- Pred->getInstList().erase(PTI);
-
- // If the condition is dead now, remove the instruction tree.
- if (DeadCond) ErasePossiblyDeadInstructionTree(DeadCond);
+ EraseTerminatorInstAndDCECond(PTI);
// Okay, last check. If BB is still a successor of PSI, then we must
// have an infinite loop case. If so, add an infinitely looping block
for (unsigned i = 0, e = NewSI->getNumSuccessors(); i != e; ++i)
if (NewSI->getSuccessor(i) == BB) {
if (InfLoopBlock == 0) {
- // Insert it at the end of the loop, because it's either code,
+ // Insert it at the end of the function, because it's either code,
// or it won't matter if it's hot. :)
- InfLoopBlock = BasicBlock::Create("infloop", BB->getParent());
+ InfLoopBlock = BasicBlock::Create(BB->getContext(),
+ "infloop", BB->getParent());
BranchInst::Create(InfLoopBlock, InfLoopBlock);
}
NewSI->setSuccessor(i, InfLoopBlock);
return Changed;
}
+// isSafeToHoistInvoke - If we would need to insert a select that uses the
+// value of this invoke (comments in HoistThenElseCodeToIf explain why we
+// would need to do this), we can't hoist the invoke, as there is nowhere
+// to put the select in this case.
+static bool isSafeToHoistInvoke(BasicBlock *BB1, BasicBlock *BB2,
+ Instruction *I1, Instruction *I2) {
+ for (succ_iterator SI = succ_begin(BB1), E = succ_end(BB1); SI != E; ++SI) {
+ PHINode *PN;
+ for (BasicBlock::iterator BBI = SI->begin();
+ (PN = dyn_cast<PHINode>(BBI)); ++BBI) {
+ Value *BB1V = PN->getIncomingValueForBlock(BB1);
+ Value *BB2V = PN->getIncomingValueForBlock(BB2);
+ if (BB1V != BB2V && (BB1V==I1 || BB2V==I2)) {
+ return false;
+ }
+ }
+ }
+ return true;
+}
+
/// HoistThenElseCodeToIf - Given a conditional branch that goes to BB1 and
/// BB2, hoist any common code in the two blocks up into the branch block. The
/// caller of this function guarantees that BI's block dominates BB1 and BB2.
BasicBlock *BB1 = BI->getSuccessor(0); // The true destination.
BasicBlock *BB2 = BI->getSuccessor(1); // The false destination
- Instruction *I1 = BB1->begin(), *I2 = BB2->begin();
- if (I1->getOpcode() != I2->getOpcode() || isa<PHINode>(I1) ||
- isa<InvokeInst>(I1) || !I1->isIdenticalTo(I2))
+ BasicBlock::iterator BB1_Itr = BB1->begin();
+ BasicBlock::iterator BB2_Itr = BB2->begin();
+
+ Instruction *I1 = BB1_Itr++, *I2 = BB2_Itr++;
+ while (isa<DbgInfoIntrinsic>(I1))
+ I1 = BB1_Itr++;
+ while (isa<DbgInfoIntrinsic>(I2))
+ I2 = BB2_Itr++;
+ if (I1->getOpcode() != I2->getOpcode() || isa<PHINode>(I1) ||
+ !I1->isIdenticalToWhenDefined(I2) ||
+ (isa<InvokeInst>(I1) && !isSafeToHoistInvoke(BB1, BB2, I1, I2)))
return false;
// If we get here, we can hoist at least one instruction.
BIParent->getInstList().splice(BI, BB1->getInstList(), I1);
if (!I2->use_empty())
I2->replaceAllUsesWith(I1);
+ I1->intersectOptionalDataWith(I2);
BB2->getInstList().erase(I2);
- I1 = BB1->begin();
- I2 = BB2->begin();
- } while (I1->getOpcode() == I2->getOpcode() && I1->isIdenticalTo(I2));
+ I1 = BB1_Itr++;
+ while (isa<DbgInfoIntrinsic>(I1))
+ I1 = BB1_Itr++;
+ I2 = BB2_Itr++;
+ while (isa<DbgInfoIntrinsic>(I2))
+ I2 = BB2_Itr++;
+ } while (I1->getOpcode() == I2->getOpcode() &&
+ I1->isIdenticalToWhenDefined(I2));
return true;
HoistTerminator:
+ // It may not be possible to hoist an invoke.
+ if (isa<InvokeInst>(I1) && !isSafeToHoistInvoke(BB1, BB2, I1, I2))
+ return true;
+
// Okay, it is safe to hoist the terminator.
Instruction *NT = I1->clone();
BIParent->getInstList().insert(BI, NT);
- if (NT->getType() != Type::VoidTy) {
+ if (!NT->getType()->isVoidTy()) {
I1->replaceAllUsesWith(NT);
I2->replaceAllUsesWith(NT);
NT->takeName(I1);
for (succ_iterator SI = succ_begin(BB1), E = succ_end(BB1); SI != E; ++SI)
AddPredecessorToBlock(*SI, BIParent, BB1);
- BI->eraseFromParent();
+ EraseTerminatorInstAndDCECond(BI);
return true;
}
static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *BB1) {
// Only speculatively execution a single instruction (not counting the
// terminator) for now.
- BasicBlock::iterator BBI = BB1->begin();
- ++BBI; // must have at least a terminator
- if (BBI == BB1->end()) return false; // only one inst
- ++BBI;
- if (BBI != BB1->end()) return false; // more than 2 insts.
+ Instruction *HInst = NULL;
+ Instruction *Term = BB1->getTerminator();
+ for (BasicBlock::iterator BBI = BB1->begin(), BBE = BB1->end();
+ BBI != BBE; ++BBI) {
+ Instruction *I = BBI;
+ // Skip debug info.
+ if (isa<DbgInfoIntrinsic>(I)) continue;
+ if (I == Term) break;
+
+ if (!HInst)
+ HInst = I;
+ else
+ return false;
+ }
+ if (!HInst)
+ return false;
// Be conservative for now. FP select instruction can often be expensive.
Value *BrCond = BI->getCondition();
// %t1 = icmp
// %t4 = add %t2, c
// %t3 = select i1 %t1, %t2, %t3
- Instruction *I = BB1->begin();
- switch (I->getOpcode()) {
+ switch (HInst->getOpcode()) {
default: return false; // Not safe / profitable to hoist.
case Instruction::Add:
case Instruction::Sub:
+ // Not worth doing for vector ops.
+ if (isa<VectorType>(HInst->getType()))
+ return false;
+ break;
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
case Instruction::Shl:
case Instruction::LShr:
case Instruction::AShr:
- if (!I->getOperand(0)->getType()->isInteger())
- // FP arithmetic might trap. Not worth doing for vector ops.
+ // Don't mess with vector operations.
+ if (isa<VectorType>(HInst->getType()))
return false;
break; // These are all cheap and non-trapping instructions.
}
+
+ // If the instruction is obviously dead, don't try to predicate it.
+ if (HInst->use_empty()) {
+ HInst->eraseFromParent();
+ return true;
+ }
// Can we speculatively execute the instruction? And what is the value
// if the condition is false? Consider the phi uses, if the incoming value
BasicBlock *BIParent = BI->getParent();
SmallVector<PHINode*, 4> PHIUses;
Value *FalseV = NULL;
- for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
+
+ BasicBlock *BB2 = BB1->getTerminator()->getSuccessor(0);
+ for (Value::use_iterator UI = HInst->use_begin(), E = HInst->use_end();
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);
- if (!PN)
- continue;
+ if (!PN || PN->getParent() != BB2)
+ return false;
PHIUses.push_back(PN);
+
Value *PHIV = PN->getIncomingValueForBlock(BIParent);
if (!FalseV)
FalseV = PHIV;
else if (FalseV != PHIV)
- return false; // Don't know the value when condition is false.
+ return false; // Inconsistent value when condition is false.
}
- if (!FalseV) // Can this happen?
- return false;
+
+ assert(FalseV && "Must have at least one user, and it must be a PHI");
// Do not hoist the instruction if any of its operands are defined but not
// used in this BB. The transformation will prevent the operand from
// being sunk into the use block.
- for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i) {
+ for (User::op_iterator i = HInst->op_begin(), e = HInst->op_end();
+ i != e; ++i) {
Instruction *OpI = dyn_cast<Instruction>(*i);
if (OpI && OpI->getParent() == BIParent &&
!OpI->isUsedInBasicBlock(BIParent))
return false;
}
- // If we get here, we can hoist the instruction. Try to place it before the
- // icmp instruction preceeding the conditional branch.
+ // If we get here, we can hoist the instruction. Try to place it
+ // before the icmp instruction preceding the conditional branch.
BasicBlock::iterator InsertPos = BI;
if (InsertPos != BIParent->begin())
--InsertPos;
- if (InsertPos == BrCond && !isa<PHINode>(BrCond))
- BIParent->getInstList().splice(InsertPos, BB1->getInstList(), I);
- else
- BIParent->getInstList().splice(BI, BB1->getInstList(), I);
+ // Skip debug info between condition and branch.
+ while (InsertPos != BIParent->begin() && isa<DbgInfoIntrinsic>(InsertPos))
+ --InsertPos;
+ if (InsertPos == BrCond && !isa<PHINode>(BrCond)) {
+ SmallPtrSet<Instruction *, 4> BB1Insns;
+ for(BasicBlock::iterator BB1I = BB1->begin(), BB1E = BB1->end();
+ BB1I != BB1E; ++BB1I)
+ BB1Insns.insert(BB1I);
+ for(Value::use_iterator UI = BrCond->use_begin(), UE = BrCond->use_end();
+ UI != UE; ++UI) {
+ Instruction *Use = cast<Instruction>(*UI);
+ if (BB1Insns.count(Use)) {
+ // If BrCond uses the instruction that place it just before
+ // branch instruction.
+ InsertPos = BI;
+ break;
+ }
+ }
+ } else
+ InsertPos = BI;
+ BIParent->getInstList().splice(InsertPos, BB1->getInstList(), HInst);
// Create a select whose true value is the speculatively executed value and
// false value is the previously determined FalseV.
SelectInst *SI;
if (Invert)
- SI = SelectInst::Create(BrCond, FalseV, I,
- FalseV->getName() + "." + I->getName(), BI);
+ SI = SelectInst::Create(BrCond, FalseV, HInst,
+ FalseV->getName() + "." + HInst->getName(), BI);
else
- SI = SelectInst::Create(BrCond, I, FalseV,
- I->getName() + "." + FalseV->getName(), BI);
+ SI = SelectInst::Create(BrCond, HInst, FalseV,
+ HInst->getName() + "." + FalseV->getName(), BI);
// Make the PHI node use the select for all incoming values for "then" and
// "if" blocks.
BranchInst *BI = cast<BranchInst>(BB->getTerminator());
unsigned Size = 0;
- // If this basic block contains anything other than a PHI (which controls the
- // branch) and branch itself, bail out. FIXME: improve this in the future.
- for (BasicBlock::iterator BBI = BB->begin(); &*BBI != BI; ++BBI, ++Size) {
+ for (BasicBlock::iterator BBI = BB->begin(); &*BBI != BI; ++BBI) {
+ if (isa<DbgInfoIntrinsic>(BBI))
+ continue;
if (Size > 10) return false; // Don't clone large BB's.
+ ++Size;
- // We can only support instructions that are do not define values that are
+ // We can only support instructions that do not define values that are
// live outside of the current basic block.
for (Value::use_iterator UI = BBI->use_begin(), E = BBI->use_end();
UI != E; ++UI) {
// Degenerate case of a single entry PHI.
if (PN->getNumIncomingValues() == 1) {
- if (PN->getIncomingValue(0) != PN)
- PN->replaceAllUsesWith(PN->getIncomingValue(0));
- else
- PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
- PN->eraseFromParent();
+ FoldSingleEntryPHINodes(PN->getParent());
return true;
}
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
ConstantInt *CB;
if ((CB = dyn_cast<ConstantInt>(PN->getIncomingValue(i))) &&
- CB->getType() == Type::Int1Ty) {
+ 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);
// difficult cases. Instead of being smart about this, just insert a new
// block that jumps to the destination block, effectively splitting
// the edge we are about to create.
- BasicBlock *EdgeBB = BasicBlock::Create(RealDest->getName()+".critedge",
+ BasicBlock *EdgeBB = BasicBlock::Create(BB->getContext(),
+ RealDest->getName()+".critedge",
RealDest->getParent(), RealDest);
BranchInst::Create(RealDest, EdgeBB);
PHINode *PN;
if (NumPhis > 2)
return false;
- DOUT << "FOUND IF CONDITION! " << *IfCond << " T: "
- << IfTrue->getName() << " F: " << IfFalse->getName() << "\n";
+ 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
// instructions. While we are at it, keep track of the instructions
DomBlock = *pred_begin(Pred);
for (BasicBlock::iterator I = Pred->begin();
!isa<TerminatorInst>(I); ++I)
- if (!AggressiveInsts.count(I)) {
+ if (!AggressiveInsts.count(I) && !isa<DbgInfoIntrinsic>(I)) {
// This is not an aggressive instruction that we can promote.
// Because of this, we won't be able to get rid of the control
// flow, so the xform is not worth it.
DomBlock = *pred_begin(Pred);
for (BasicBlock::iterator I = Pred->begin();
!isa<TerminatorInst>(I); ++I)
- if (!AggressiveInsts.count(I)) {
+ if (!AggressiveInsts.count(I) && !isa<DbgInfoIntrinsic>(I)) {
// This is not an aggressive instruction that we can promote.
// Because of this, we won't be able to get rid of the control
// flow, so the xform is not worth it.
return true;
}
+/// isTerminatorFirstRelevantInsn - Return true if Term is very first
+/// instruction ignoring Phi nodes and dbg intrinsics.
+static bool isTerminatorFirstRelevantInsn(BasicBlock *BB, Instruction *Term) {
+ BasicBlock::iterator BBI = Term;
+ while (BBI != BB->begin()) {
+ --BBI;
+ if (!isa<DbgInfoIntrinsic>(BBI))
+ break;
+ }
+
+ if (isa<PHINode>(BBI) || &*BBI == Term || isa<DbgInfoIntrinsic>(BBI))
+ return true;
+ return false;
+}
+
/// SimplifyCondBranchToTwoReturns - If we found a conditional branch that goes
/// to two returning blocks, try to merge them together into one return,
/// introducing a select if the return values disagree.
// Check to ensure both blocks are empty (just a return) or optionally empty
// with PHI nodes. If there are other instructions, merging would cause extra
// computation on one path or the other.
- BasicBlock::iterator BBI = TrueRet;
- if (BBI != TrueSucc->begin() && !isa<PHINode>(--BBI))
- return false; // Not empty with optional phi nodes.
- BBI = FalseRet;
- if (BBI != FalseSucc->begin() && !isa<PHINode>(--BBI))
- return false; // Not empty with optional phi nodes.
+ if (!isTerminatorFirstRelevantInsn(TrueSucc, TrueRet))
+ return false;
+ if (!isTerminatorFirstRelevantInsn(FalseSucc, FalseRet))
+ return false;
// Okay, we found a branch that is going to two return nodes. If
// there is no return value for this function, just change the
if (FalseRet->getNumOperands() == 0) {
TrueSucc->removePredecessor(BI->getParent());
FalseSucc->removePredecessor(BI->getParent());
- ReturnInst::Create(0, BI);
- BI->eraseFromParent();
+ ReturnInst::Create(BI->getContext(), 0, BI);
+ EraseTerminatorInstAndDCECond(BI);
return true;
}
- // Otherwise, build up the result values for the new return.
- SmallVector<Value*, 4> TrueResult;
- SmallVector<Value*, 4> FalseResult;
+ // Otherwise, figure out what the true and false return values are
+ // so we can insert a new select instruction.
+ Value *TrueValue = TrueRet->getReturnValue();
+ Value *FalseValue = FalseRet->getReturnValue();
+
+ // Unwrap any PHI nodes in the return blocks.
+ if (PHINode *TVPN = dyn_cast_or_null<PHINode>(TrueValue))
+ if (TVPN->getParent() == TrueSucc)
+ TrueValue = TVPN->getIncomingValueForBlock(BI->getParent());
+ if (PHINode *FVPN = dyn_cast_or_null<PHINode>(FalseValue))
+ if (FVPN->getParent() == FalseSucc)
+ FalseValue = FVPN->getIncomingValueForBlock(BI->getParent());
+
+ // In order for this transformation to be safe, we must be able to
+ // unconditionally execute both operands to the return. This is
+ // normally the case, but we could have a potentially-trapping
+ // constant expression that prevents this transformation from being
+ // safe.
+ if (ConstantExpr *TCV = dyn_cast_or_null<ConstantExpr>(TrueValue))
+ if (TCV->canTrap())
+ return false;
+ if (ConstantExpr *FCV = dyn_cast_or_null<ConstantExpr>(FalseValue))
+ if (FCV->canTrap())
+ return false;
- for (unsigned i = 0, e = TrueRet->getNumOperands(); i != e; ++i) {
- // Otherwise, figure out what the true and false return values are
- // so we can insert a new select instruction.
- Value *TrueValue = TrueRet->getOperand(i);
- Value *FalseValue = FalseRet->getOperand(i);
-
- // Unwrap any PHI nodes in the return blocks.
- if (PHINode *TVPN = dyn_cast<PHINode>(TrueValue))
- if (TVPN->getParent() == TrueSucc)
- TrueValue = TVPN->getIncomingValueForBlock(BI->getParent());
- if (PHINode *FVPN = dyn_cast<PHINode>(FalseValue))
- if (FVPN->getParent() == FalseSucc)
- FalseValue = FVPN->getIncomingValueForBlock(BI->getParent());
-
- // In order for this transformation to be safe, we must be able to
- // unconditionally execute both operands to the return. This is
- // normally the case, but we could have a potentially-trapping
- // constant expression that prevents this transformation from being
- // safe.
- if (ConstantExpr *TCV = dyn_cast<ConstantExpr>(TrueValue))
- if (TCV->canTrap())
- return false;
- if (ConstantExpr *FCV = dyn_cast<ConstantExpr>(FalseValue))
- if (FCV->canTrap())
- return false;
-
- TrueResult.push_back(TrueValue);
- FalseResult.push_back(FalseValue);
- }
-
// Okay, we collected all the mapped values and checked them for sanity, and
// defined to really do this transformation. First, update the CFG.
TrueSucc->removePredecessor(BI->getParent());
// Insert select instructions where needed.
Value *BrCond = BI->getCondition();
- for (unsigned i = 0, e = TrueRet->getNumOperands(); i != e; ++i) {
+ if (TrueValue) {
// Insert a select if the results differ.
- if (TrueResult[i] == FalseResult[i] || isa<UndefValue>(FalseResult[i]))
- continue;
- if (isa<UndefValue>(TrueResult[i])) {
- TrueResult[i] = FalseResult[i];
- continue;
+ if (TrueValue == FalseValue || isa<UndefValue>(FalseValue)) {
+ } else if (isa<UndefValue>(TrueValue)) {
+ TrueValue = FalseValue;
+ } else {
+ TrueValue = SelectInst::Create(BrCond, TrueValue,
+ FalseValue, "retval", BI);
}
-
- TrueResult[i] = SelectInst::Create(BrCond, TrueResult[i],
- FalseResult[i], "retval", BI);
}
- Value *RI = ReturnInst::Create(&TrueResult[0], TrueResult.size(), BI);
+ Value *RI = !TrueValue ?
+ ReturnInst::Create(BI->getContext(), BI) :
+ ReturnInst::Create(BI->getContext(), TrueValue, BI);
+ (void) RI;
- DOUT << "\nCHANGING BRANCH TO TWO RETURNS INTO SELECT:"
- << "\n " << *BI << "NewRet = " << *RI
- << "TRUEBLOCK: " << *TrueSucc << "FALSEBLOCK: "<< *FalseSucc;
+ DEBUG(dbgs() << "\nCHANGING BRANCH TO TWO RETURNS INTO SELECT:"
+ << "\n " << *BI << "NewRet = " << *RI
+ << "TRUEBLOCK: " << *TrueSucc << "FALSEBLOCK: "<< *FalseSucc);
- BI->eraseFromParent();
-
- if (Instruction *BrCondI = dyn_cast<Instruction>(BrCond))
- ErasePossiblyDeadInstructionTree(BrCondI);
+ EraseTerminatorInstAndDCECond(BI);
+
return true;
}
+/// FoldBranchToCommonDest - If this basic block is ONLY a setcc and a branch,
+/// and if a predecessor branches to us and one of our successors, fold the
+/// setcc into the predecessor and use logical operations to pick the right
+/// destination.
+bool llvm::FoldBranchToCommonDest(BranchInst *BI) {
+ BasicBlock *BB = BI->getParent();
+ Instruction *Cond = dyn_cast<Instruction>(BI->getCondition());
+ if (Cond == 0) return false;
-namespace {
- /// ConstantIntOrdering - This class implements a stable ordering of constant
- /// integers that does not depend on their address. This is important for
- /// applications that sort ConstantInt's to ensure uniqueness.
- struct ConstantIntOrdering {
- bool operator()(const ConstantInt *LHS, const ConstantInt *RHS) const {
- return LHS->getValue().ult(RHS->getValue());
+
+ // 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
+ // must be at the front of the block.
+ BasicBlock::iterator FrontIt = BB->front();
+ // Ignore dbg intrinsics.
+ while(isa<DbgInfoIntrinsic>(FrontIt))
+ ++FrontIt;
+ if ((!isa<CmpInst>(Cond) && !isa<BinaryOperator>(Cond)) ||
+ Cond->getParent() != BB || &*FrontIt != Cond || !Cond->hasOneUse()) {
+ return false;
+ }
+
+ // Make sure the instruction after the condition is the cond branch.
+ BasicBlock::iterator CondIt = Cond; ++CondIt;
+ // Ingore dbg intrinsics.
+ while(isa<DbgInfoIntrinsic>(CondIt))
+ ++CondIt;
+ if (&*CondIt != BI) {
+ assert (!isa<DbgInfoIntrinsic>(CondIt) && "Hey do not forget debug info!");
+ return false;
+ }
+
+ // Cond is known to be a compare or binary operator. Check to make sure that
+ // neither operand is a potentially-trapping constant expression.
+ if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Cond->getOperand(0)))
+ if (CE->canTrap())
+ return false;
+ if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Cond->getOperand(1)))
+ if (CE->canTrap())
+ return false;
+
+
+ // Finally, don't infinitely unroll conditional loops.
+ BasicBlock *TrueDest = BI->getSuccessor(0);
+ BasicBlock *FalseDest = BI->getSuccessor(1);
+ if (TrueDest == BB || FalseDest == BB)
+ return false;
+
+ for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
+ BasicBlock *PredBlock = *PI;
+ BranchInst *PBI = dyn_cast<BranchInst>(PredBlock->getTerminator());
+
+ // Check that we have two conditional branches. If there is a PHI node in
+ // the common successor, verify that the same value flows in from both
+ // blocks.
+ if (PBI == 0 || PBI->isUnconditional() ||
+ !SafeToMergeTerminators(BI, PBI))
+ continue;
+
+ Instruction::BinaryOps Opc;
+ bool InvertPredCond = false;
+
+ if (PBI->getSuccessor(0) == TrueDest)
+ Opc = Instruction::Or;
+ else if (PBI->getSuccessor(1) == FalseDest)
+ Opc = Instruction::And;
+ else if (PBI->getSuccessor(0) == FalseDest)
+ Opc = Instruction::And, InvertPredCond = true;
+ else if (PBI->getSuccessor(1) == TrueDest)
+ Opc = Instruction::Or, InvertPredCond = true;
+ else
+ continue;
+
+ 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) {
+ Value *NewCond =
+ BinaryOperator::CreateNot(PBI->getCondition(),
+ PBI->getCondition()->getName()+".not", PBI);
+ PBI->setCondition(NewCond);
+ BasicBlock *OldTrue = PBI->getSuccessor(0);
+ BasicBlock *OldFalse = PBI->getSuccessor(1);
+ PBI->setSuccessor(0, OldFalse);
+ PBI->setSuccessor(1, OldTrue);
}
- };
+
+ // Clone Cond into the predecessor basic block, and or/and the
+ // two conditions together.
+ Instruction *New = Cond->clone();
+ PredBlock->getInstList().insert(PBI, New);
+ New->takeName(Cond);
+ Cond->setName(New->getName()+".old");
+
+ Value *NewCond = BinaryOperator::Create(Opc, PBI->getCondition(),
+ New, "or.cond", PBI);
+ PBI->setCondition(NewCond);
+ if (PBI->getSuccessor(0) == BB) {
+ AddPredecessorToBlock(TrueDest, PredBlock, BB);
+ PBI->setSuccessor(0, TrueDest);
+ }
+ if (PBI->getSuccessor(1) == BB) {
+ AddPredecessorToBlock(FalseDest, PredBlock, BB);
+ PBI->setSuccessor(1, FalseDest);
+ }
+ return true;
+ }
+ return false;
}
-// 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) {
+/// SimplifyCondBranchToCondBranch - If we have a conditional branch as a
+/// predecessor of another block, this function tries to simplify it. We know
+/// that PBI and BI are both conditional branches, and BI is in one of the
+/// successor blocks of PBI - PBI branches to BI.
+static bool SimplifyCondBranchToCondBranch(BranchInst *PBI, BranchInst *BI) {
+ assert(PBI->isConditional() && BI->isConditional());
+ BasicBlock *BB = BI->getParent();
+
+ // If this block ends with a branch instruction, and if there is a
+ // predecessor that ends on a branch of the same condition, make
+ // this conditional branch redundant.
+ if (PBI->getCondition() == BI->getCondition() &&
+ PBI->getSuccessor(0) != PBI->getSuccessor(1)) {
+ // Okay, the outcome of this conditional branch is statically
+ // knowable. If this block had a single pred, handle specially.
+ if (BB->getSinglePredecessor()) {
+ // Turn this into a branch on constant.
+ bool CondIsTrue = PBI->getSuccessor(0) == BB;
+ BI->setCondition(ConstantInt::get(Type::getInt1Ty(BB->getContext()),
+ CondIsTrue));
+ return true; // Nuke the branch on constant.
+ }
+
+ // Otherwise, if there are multiple predecessors, insert a PHI that merges
+ // in the constant and simplify the block result. Subsequent passes of
+ // simplifycfg will thread the block.
+ if (BlockIsSimpleEnoughToThreadThrough(BB)) {
+ PHINode *NewPN = PHINode::Create(Type::getInt1Ty(BB->getContext()),
+ BI->getCondition()->getName() + ".pr",
+ BB->begin());
+ // 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())) &&
+ 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);
+ } else {
+ NewPN->addIncoming(BI->getCondition(), *PI);
+ }
+
+ BI->setCondition(NewPN);
+ return true;
+ }
+ }
+
+ // If this is a conditional branch in an empty block, and if any
+ // predecessors is a conditional branch to one of our destinations,
+ // fold the conditions into logical ops and one cond br.
+ BasicBlock::iterator BBI = BB->begin();
+ // Ignore dbg intrinsics.
+ while (isa<DbgInfoIntrinsic>(BBI))
+ ++BBI;
+ if (&*BBI != BI)
+ return false;
+
+
+ if (ConstantExpr *CE = dyn_cast<ConstantExpr>(BI->getCondition()))
+ if (CE->canTrap())
+ return false;
+
+ int PBIOp, BIOp;
+ if (PBI->getSuccessor(0) == BI->getSuccessor(0))
+ PBIOp = BIOp = 0;
+ else if (PBI->getSuccessor(0) == BI->getSuccessor(1))
+ PBIOp = 0, BIOp = 1;
+ else if (PBI->getSuccessor(1) == BI->getSuccessor(0))
+ PBIOp = 1, BIOp = 0;
+ else if (PBI->getSuccessor(1) == BI->getSuccessor(1))
+ PBIOp = BIOp = 1;
+ else
+ return false;
+
+ // Check to make sure that the other destination of this branch
+ // isn't BB itself. If so, this is an infinite loop that will
+ // keep getting unwound.
+ if (PBI->getSuccessor(PBIOp) == BB)
+ return false;
+
+ // Do not perform this transformation if it would require
+ // insertion of a large number of select instructions. For targets
+ // without predication/cmovs, this is a big pessimization.
+ BasicBlock *CommonDest = PBI->getSuccessor(PBIOp);
+
+ unsigned NumPhis = 0;
+ for (BasicBlock::iterator II = CommonDest->begin();
+ isa<PHINode>(II); ++II, ++NumPhis)
+ if (NumPhis > 2) // Disable this xform.
+ return false;
+
+ // Finally, if everything is ok, fold the branches to logical ops.
+ BasicBlock *OtherDest = BI->getSuccessor(BIOp ^ 1);
+
+ DEBUG(dbgs() << "FOLDING BRs:" << *PBI->getParent()
+ << "AND: " << *BI->getParent());
+
+
+ // If OtherDest *is* BB, then BB is a basic block with a single conditional
+ // branch in it, where one edge (OtherDest) goes back to itself but the other
+ // exits. We don't *know* that the program avoids the infinite loop
+ // (even though that seems likely). If we do this xform naively, we'll end up
+ // recursively unpeeling the loop. Since we know that (after the xform is
+ // done) that the block *is* infinite if reached, we just make it an obviously
+ // infinite loop with no cond branch.
+ if (OtherDest == BB) {
+ // Insert it at the end of the function, because it's either code,
+ // or it won't matter if it's hot. :)
+ BasicBlock *InfLoopBlock = BasicBlock::Create(BB->getContext(),
+ "infloop", BB->getParent());
+ BranchInst::Create(InfLoopBlock, InfLoopBlock);
+ OtherDest = InfLoopBlock;
+ }
+
+ DEBUG(dbgs() << *PBI->getParent()->getParent());
+
+ // BI may have other predecessors. Because of this, we leave
+ // it alone, but modify PBI.
+
+ // Make sure we get to CommonDest on True&True directions.
+ Value *PBICond = PBI->getCondition();
+ if (PBIOp)
+ PBICond = BinaryOperator::CreateNot(PBICond,
+ PBICond->getName()+".not",
+ PBI);
+ Value *BICond = BI->getCondition();
+ if (BIOp)
+ BICond = BinaryOperator::CreateNot(BICond,
+ BICond->getName()+".not",
+ PBI);
+ // Merge the conditions.
+ Value *Cond = BinaryOperator::CreateOr(PBICond, BICond, "brmerge", PBI);
+
+ // Modify PBI to branch on the new condition to the new dests.
+ PBI->setCondition(Cond);
+ PBI->setSuccessor(0, CommonDest);
+ PBI->setSuccessor(1, OtherDest);
+
+ // OtherDest may have phi nodes. If so, add an entry from PBI's
+ // block that are identical to the entries for BI's block.
+ PHINode *PN;
+ for (BasicBlock::iterator II = OtherDest->begin();
+ (PN = dyn_cast<PHINode>(II)); ++II) {
+ Value *V = PN->getIncomingValueForBlock(BB);
+ PN->addIncoming(V, PBI->getParent());
+ }
+
+ // We know that the CommonDest already had an edge from PBI to
+ // it. If it has PHIs though, the PHIs may have different
+ // entries for BB and PBI's BB. If so, insert a select to make
+ // them agree.
+ for (BasicBlock::iterator II = CommonDest->begin();
+ (PN = dyn_cast<PHINode>(II)); ++II) {
+ Value *BIV = PN->getIncomingValueForBlock(BB);
+ unsigned PBBIdx = PN->getBasicBlockIndex(PBI->getParent());
+ Value *PBIV = PN->getIncomingValue(PBBIdx);
+ if (BIV != PBIV) {
+ // Insert a select in PBI to pick the right value.
+ Value *NV = SelectInst::Create(PBICond, PBIV, BIV,
+ PBIV->getName()+".mux", PBI);
+ PN->setIncomingValue(PBBIdx, NV);
+ }
+ }
+
+ 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;
+}
+
+bool SimplifyCFGOpt::run(BasicBlock *BB) {
bool Changed = false;
Function *M = BB->getParent();
assert(&BB->getParent()->getEntryBlock() != BB &&
"Can't Simplify entry block!");
- // Remove basic blocks that have no predecessors... which are unreachable.
- if ((pred_begin(BB) == pred_end(BB)) ||
- (*pred_begin(BB) == BB && ++pred_begin(BB) == pred_end(BB))) {
- DOUT << "Removing BB: \n" << *BB;
-
- // Loop through all of our successors and make sure they know that one
- // of their predecessors is going away.
- for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI)
- SI->removePredecessor(BB);
-
- while (!BB->empty()) {
- Instruction &I = BB->back();
- // If this instruction is used, replace uses with an arbitrary
- // value. Because control flow can't get here, we don't care
- // what we replace the value with. Note that since this block is
- // unreachable, and all values contained within it must dominate their
- // uses, that all uses will eventually be removed.
- if (!I.use_empty())
- // Make all users of this instruction use undef instead
- I.replaceAllUsesWith(UndefValue::get(I.getType()));
-
- // Remove the instruction from the basic block
- BB->getInstList().pop_back();
- }
- M->getBasicBlockList().erase(BB);
+ // 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(dbgs() << "Removing BB: \n" << *BB);
+ DeleteDeadBlock(BB);
return true;
}
// away...
Changed |= ConstantFoldTerminator(BB);
+ // Check for and eliminate duplicate PHI nodes in this block.
+ Changed |= EliminateDuplicatePHINodes(BB);
+
// If there is a trivial two-entry PHI node in this basic block, and we can
// eliminate it, do so now.
if (PHINode *PN = dyn_cast<PHINode>(BB->begin()))
// different return values, fold the replace the branch/return with a select
// and return.
if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
- BasicBlock::iterator BBI = BB->getTerminator();
- if (BBI == BB->begin() || isa<PHINode>(--BBI)) {
+ if (isTerminatorFirstRelevantInsn(BB, BB->getTerminator())) {
// Find predecessors that end with branches.
SmallVector<BasicBlock*, 8> UncondBranchPreds;
SmallVector<BranchInst*, 8> CondBranchPreds;
// If we found some, do the transformation!
if (!UncondBranchPreds.empty()) {
while (!UncondBranchPreds.empty()) {
- BasicBlock *Pred = UncondBranchPreds.back();
- DOUT << "FOLDING: " << *BB
- << "INTO UNCOND BRANCH PRED: " << *Pred;
- UncondBranchPreds.pop_back();
+ BasicBlock *Pred = UncondBranchPreds.pop_back_val();
+ 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();
// instruction. If any of them just select between returns, change the
// branch itself into a select/return pair.
while (!CondBranchPreds.empty()) {
- BranchInst *BI = CondBranchPreds.back();
- CondBranchPreds.pop_back();
+ BranchInst *BI = CondBranchPreds.pop_back_val();
// Check to see if the non-BB successor is also a return block.
if (isa<ReturnInst>(BI->getSuccessor(0)->getTerminator()) &&
} else if (isa<UnwindInst>(BB->begin())) {
// Check to see if the first instruction in this block is just an unwind.
// If so, replace any invoke instructions which use this as an exception
- // destination with call instructions, and any unconditional branch
- // predecessor with an unwind.
+ // destination with call instructions.
//
SmallVector<BasicBlock*, 8> Preds(pred_begin(BB), pred_end(BB));
while (!Preds.empty()) {
BasicBlock *Pred = Preds.back();
- if (BranchInst *BI = dyn_cast<BranchInst>(Pred->getTerminator())) {
- if (BI->isUnconditional()) {
- Pred->getInstList().pop_back(); // nuke uncond branch
- new UnwindInst(Pred); // Use unwind.
- Changed = true;
- }
- } else if (InvokeInst *II = dyn_cast<InvokeInst>(Pred->getTerminator()))
+ if (InvokeInst *II = dyn_cast<InvokeInst>(Pred->getTerminator()))
if (II->getUnwindDest() == BB) {
// Insert a new branch instruction before the invoke, because this
- // is now a fall through...
+ // is now a fall through.
BranchInst *BI = BranchInst::Create(II->getNormalDest(), II);
Pred->getInstList().remove(II); // Take out of symbol table
- // Insert the call now...
+ // Insert the call now.
SmallVector<Value*,8> Args(II->op_begin()+3, II->op_end());
CallInst *CI = CallInst::Create(II->getCalledValue(),
Args.begin(), Args.end(),
II->getName(), BI);
CI->setCallingConv(II->getCallingConv());
- CI->setParamAttrs(II->getParamAttrs());
- // If the invoke produced a value, the Call now does instead
+ CI->setAttributes(II->getAttributes());
+ // If the invoke produced a value, the Call now does instead.
II->replaceAllUsesWith(CI);
delete II;
Changed = true;
// If the block only contains the switch, see if we can fold the block
// away into any preds.
- if (SI == &BB->front())
+ BasicBlock::iterator BBI = BB->begin();
+ // Ignore dbg intrinsics.
+ while (isa<DbgInfoIntrinsic>(BBI))
+ ++BBI;
+ if (SI == &*BBI)
if (FoldValueComparisonIntoPredecessors(SI))
return SimplifyCFG(BB) || 1;
}
if (BI->isUnconditional()) {
BasicBlock::iterator BBI = BB->getFirstNonPHI();
- BasicBlock *Succ = BI->getSuccessor(0);
- if (BBI->isTerminator() && // Terminator is the only non-phi instruction!
- Succ != BB) // Don't hurt infinite loops!
- if (TryToSimplifyUncondBranchFromEmptyBlock(BB, Succ))
- return 1;
+ // Ignore dbg intrinsics.
+ while (isa<DbgInfoIntrinsic>(BBI))
+ ++BBI;
+ if (BBI->isTerminator()) // Terminator is the only non-phi instruction!
+ if (TryToSimplifyUncondBranchFromEmptyBlock(BB))
+ return true;
} else { // Conditional branch
if (isValueEqualityComparison(BI)) {
return SimplifyCFG(BB) || 1;
// This block must be empty, except for the setcond inst, if it exists.
+ // Ignore dbg intrinsics.
BasicBlock::iterator I = BB->begin();
- if (&*I == BI ||
- (&*I == cast<Instruction>(BI->getCondition()) &&
- &*++I == BI))
+ // Ignore dbg intrinsics.
+ while (isa<DbgInfoIntrinsic>(I))
+ ++I;
+ if (&*I == BI) {
if (FoldValueComparisonIntoPredecessors(BI))
return SimplifyCFG(BB) | true;
+ } else if (&*I == cast<Instruction>(BI->getCondition())){
+ ++I;
+ // Ignore dbg intrinsics.
+ while (isa<DbgInfoIntrinsic>(I))
+ ++I;
+ if(&*I == BI) {
+ if (FoldValueComparisonIntoPredecessors(BI))
+ return SimplifyCFG(BB) | 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()))
// If this basic block is ONLY a setcc and a branch, and if a predecessor
// branches to us and one of our successors, fold the setcc into the
// predecessor and use logical operations to pick the right destination.
- BasicBlock *TrueDest = BI->getSuccessor(0);
- BasicBlock *FalseDest = BI->getSuccessor(1);
- if (Instruction *Cond = dyn_cast<Instruction>(BI->getCondition())) {
- BasicBlock::iterator CondIt = Cond;
- if ((isa<CmpInst>(Cond) || isa<BinaryOperator>(Cond)) &&
- Cond->getParent() == BB && &BB->front() == Cond &&
- &*++CondIt == BI && Cond->hasOneUse() &&
- TrueDest != BB && FalseDest != BB)
- for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI!=E; ++PI)
- if (BranchInst *PBI = dyn_cast<BranchInst>((*PI)->getTerminator()))
- if (PBI->isConditional() && SafeToMergeTerminators(BI, PBI)) {
- BasicBlock *PredBlock = *PI;
- if (PBI->getSuccessor(0) == FalseDest ||
- PBI->getSuccessor(1) == TrueDest) {
- // Invert the predecessors condition test (xor it with true),
- // which allows us to write this code once.
- Value *NewCond =
- BinaryOperator::CreateNot(PBI->getCondition(),
- PBI->getCondition()->getName()+".not", PBI);
- PBI->setCondition(NewCond);
- BasicBlock *OldTrue = PBI->getSuccessor(0);
- BasicBlock *OldFalse = PBI->getSuccessor(1);
- PBI->setSuccessor(0, OldFalse);
- PBI->setSuccessor(1, OldTrue);
- }
+ if (FoldBranchToCommonDest(BI))
+ return SimplifyCFG(BB) | 1;
- if ((PBI->getSuccessor(0) == TrueDest && FalseDest != BB) ||
- (PBI->getSuccessor(1) == FalseDest && TrueDest != BB)) {
- // Clone Cond into the predecessor basic block, and or/and the
- // two conditions together.
- Instruction *New = Cond->clone();
- PredBlock->getInstList().insert(PBI, New);
- New->takeName(Cond);
- Cond->setName(New->getName()+".old");
- Instruction::BinaryOps Opcode =
- PBI->getSuccessor(0) == TrueDest ?
- Instruction::Or : Instruction::And;
- Value *NewCond =
- BinaryOperator::Create(Opcode, PBI->getCondition(),
- New, "bothcond", PBI);
- PBI->setCondition(NewCond);
- if (PBI->getSuccessor(0) == BB) {
- AddPredecessorToBlock(TrueDest, PredBlock, BB);
- PBI->setSuccessor(0, TrueDest);
- }
- if (PBI->getSuccessor(1) == BB) {
- AddPredecessorToBlock(FalseDest, PredBlock, BB);
- PBI->setSuccessor(1, FalseDest);
- }
- return SimplifyCFG(BB) | 1;
- }
- }
- }
- // Scan predessor blocks for conditional branches.
+ // 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 this block ends with a branch instruction, and if there is a
- // predecessor that ends on a branch of the same condition, make
- // this conditional branch redundant.
- if (PBI->getCondition() == BI->getCondition() &&
- PBI->getSuccessor(0) != PBI->getSuccessor(1)) {
- // Okay, the outcome of this conditional branch is statically
- // knowable. If this block had a single pred, handle specially.
- if (BB->getSinglePredecessor()) {
- // Turn this into a branch on constant.
- bool CondIsTrue = PBI->getSuccessor(0) == BB;
- BI->setCondition(ConstantInt::get(Type::Int1Ty, CondIsTrue));
- return SimplifyCFG(BB); // Nuke the branch on constant.
- }
-
- // Otherwise, if there are multiple predecessors, insert a PHI
- // that merges in the constant and simplify the block result.
- if (BlockIsSimpleEnoughToThreadThrough(BB)) {
- PHINode *NewPN = PHINode::Create(Type::Int1Ty,
- BI->getCondition()->getName()
- + ".pr", BB->begin());
- for (PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
- if ((PBI = dyn_cast<BranchInst>((*PI)->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::Int1Ty,
- CondIsTrue), *PI);
- } else {
- NewPN->addIncoming(BI->getCondition(), *PI);
- }
-
- BI->setCondition(NewPN);
- // This will thread the branch.
- return SimplifyCFG(BB) | true;
- }
- }
-
- // If this is a conditional branch in an empty block, and if any
- // predecessors is a conditional branch to one of our destinations,
- // fold the conditions into logical ops and one cond br.
- if (&BB->front() == BI) {
- int PBIOp, BIOp;
- if (PBI->getSuccessor(0) == BI->getSuccessor(0)) {
- PBIOp = BIOp = 0;
- } else if (PBI->getSuccessor(0) == BI->getSuccessor(1)) {
- PBIOp = 0; BIOp = 1;
- } else if (PBI->getSuccessor(1) == BI->getSuccessor(0)) {
- PBIOp = 1; BIOp = 0;
- } else if (PBI->getSuccessor(1) == BI->getSuccessor(1)) {
- PBIOp = BIOp = 1;
- } else {
- PBIOp = BIOp = -1;
- }
-
- // Check to make sure that the other destination of this branch
- // isn't BB itself. If so, this is an infinite loop that will
- // keep getting unwound.
- if (PBIOp != -1 && PBI->getSuccessor(PBIOp) == BB)
- PBIOp = BIOp = -1;
-
- // Do not perform this transformation if it would require
- // insertion of a large number of select instructions. For targets
- // without predication/cmovs, this is a big pessimization.
- if (PBIOp != -1) {
- BasicBlock *CommonDest = PBI->getSuccessor(PBIOp);
-
- unsigned NumPhis = 0;
- for (BasicBlock::iterator II = CommonDest->begin();
- isa<PHINode>(II); ++II, ++NumPhis) {
- if (NumPhis > 2) {
- // Disable this xform.
- PBIOp = -1;
- break;
- }
- }
- }
-
- // Finally, if everything is ok, fold the branches to logical ops.
- if (PBIOp != -1) {
- BasicBlock *CommonDest = PBI->getSuccessor(PBIOp);
- BasicBlock *OtherDest = BI->getSuccessor(BIOp ^ 1);
-
- // If OtherDest *is* BB, then this is a basic block with just
- // a conditional branch in it, where one edge (OtherDesg) goes
- // back to the block. We know that the program doesn't get
- // stuck in the infinite loop, so the condition must be such
- // that OtherDest isn't branched through. Forward to CommonDest,
- // and avoid an infinite loop at optimizer time.
- if (OtherDest == BB)
- OtherDest = CommonDest;
-
- DOUT << "FOLDING BRs:" << *PBI->getParent()
- << "AND: " << *BI->getParent();
-
- // BI may have other predecessors. Because of this, we leave
- // it alone, but modify PBI.
-
- // Make sure we get to CommonDest on True&True directions.
- Value *PBICond = PBI->getCondition();
- if (PBIOp)
- PBICond = BinaryOperator::CreateNot(PBICond,
- PBICond->getName()+".not",
- PBI);
- Value *BICond = BI->getCondition();
- if (BIOp)
- BICond = BinaryOperator::CreateNot(BICond,
- BICond->getName()+".not",
- PBI);
- // Merge the conditions.
- Value *Cond =
- BinaryOperator::CreateOr(PBICond, BICond, "brmerge", PBI);
-
- // Modify PBI to branch on the new condition to the new dests.
- PBI->setCondition(Cond);
- PBI->setSuccessor(0, CommonDest);
- PBI->setSuccessor(1, OtherDest);
-
- // OtherDest may have phi nodes. If so, add an entry from PBI's
- // block that are identical to the entries for BI's block.
- PHINode *PN;
- for (BasicBlock::iterator II = OtherDest->begin();
- (PN = dyn_cast<PHINode>(II)); ++II) {
- Value *V = PN->getIncomingValueForBlock(BB);
- PN->addIncoming(V, PBI->getParent());
- }
-
- // We know that the CommonDest already had an edge from PBI to
- // it. If it has PHIs though, the PHIs may have different
- // entries for BB and PBI's BB. If so, insert a select to make
- // them agree.
- for (BasicBlock::iterator II = CommonDest->begin();
- (PN = dyn_cast<PHINode>(II)); ++II) {
- Value * BIV = PN->getIncomingValueForBlock(BB);
- unsigned PBBIdx = PN->getBasicBlockIndex(PBI->getParent());
- Value *PBIV = PN->getIncomingValue(PBBIdx);
- if (BIV != PBIV) {
- // Insert a select in PBI to pick the right value.
- Value *NV = SelectInst::Create(PBICond, PBIV, BIV,
- PBIV->getName()+".mux", PBI);
- PN->setIncomingValue(PBBIdx, NV);
- }
- }
-
- DOUT << "INTO: " << *PBI->getParent();
-
- // This basic block is probably dead. We know it has at least
- // one fewer predecessor.
- return SimplifyCFG(BB) | true;
- }
- }
- }
+ if (PBI != BI && PBI->isConditional())
+ if (SimplifyCondBranchToCondBranch(PBI, BI))
+ return SimplifyCFG(BB) | true;
}
} else if (isa<UnreachableInst>(BB->getTerminator())) {
// If there are any instructions immediately before the unreachable that can
while (Unreachable != BB->begin()) {
BasicBlock::iterator BBI = Unreachable;
--BBI;
- if (isa<CallInst>(BBI)) break;
+ // Do not delete instructions that can have side effects, like calls
+ // (which may never return) and volatile loads and stores.
+ if (isa<CallInst>(BBI) && !isa<DbgInfoIntrinsic>(BBI)) break;
+
+ if (StoreInst *SI = dyn_cast<StoreInst>(BBI))
+ if (SI->isVolatile())
+ break;
+
+ if (LoadInst *LI = dyn_cast<LoadInst>(BBI))
+ if (LI->isVolatile())
+ break;
+
// Delete this instruction
BB->getInstList().erase(BBI);
Changed = true;
if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
if (BI->isUnconditional()) {
if (BI->getSuccessor(0) == BB) {
- new UnreachableInst(TI);
+ new UnreachableInst(TI->getContext(), TI);
TI->eraseFromParent();
Changed = true;
}
} else {
if (BI->getSuccessor(0) == BB) {
BranchInst::Create(BI->getSuccessor(1), BI);
- BI->eraseFromParent();
+ EraseTerminatorInstAndDCECond(BI);
} else if (BI->getSuccessor(1) == BB) {
BranchInst::Create(BI->getSuccessor(0), BI);
- BI->eraseFromParent();
+ EraseTerminatorInstAndDCECond(BI);
Changed = true;
}
}
Args.begin(), Args.end(),
II->getName(), BI);
CI->setCallingConv(II->getCallingConv());
- CI->setParamAttrs(II->getParamAttrs());
+ CI->setAttributes(II->getAttributes());
// If the invoke produced a value, the Call does now instead.
II->replaceAllUsesWith(CI);
delete II;
// pred, and if there is only one distinct successor of the predecessor, and
// if there are no PHI nodes.
//
+ if (MergeBlockIntoPredecessor(BB))
+ return true;
+
+ // Otherwise, if this block only has a single predecessor, and if that block
+ // 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
OnlyPred = 0; // There are multiple different predecessors...
break;
}
-
- BasicBlock *OnlySucc = 0;
- if (OnlyPred && OnlyPred != BB && // Don't break self loops
- OnlyPred->getTerminator()->getOpcode() != Instruction::Invoke) {
- // Check to see if there is only one distinct successor...
- succ_iterator SI(succ_begin(OnlyPred)), SE(succ_end(OnlyPred));
- OnlySucc = BB;
- for (; SI != SE; ++SI)
- if (*SI != OnlySucc) {
- OnlySucc = 0; // There are multiple distinct successors!
- break;
- }
- }
-
- if (OnlySucc) {
- DOUT << "Merging: " << *BB << "into: " << *OnlyPred;
-
- // Resolve any PHI nodes at the start of the block. They are all
- // guaranteed to have exactly one entry if they exist, unless there are
- // multiple duplicate (but guaranteed to be equal) entries for the
- // incoming edges. This occurs when there are multiple edges from
- // OnlyPred to OnlySucc.
- //
- while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
- PN->replaceAllUsesWith(PN->getIncomingValue(0));
- BB->getInstList().pop_front(); // Delete the phi node.
- }
-
- // Delete the unconditional branch from the predecessor.
- OnlyPred->getInstList().pop_back();
-
- // Move all definitions in the successor to the predecessor.
- OnlyPred->getInstList().splice(OnlyPred->end(), BB->getInstList());
-
- // Make all PHI nodes that referred to BB now refer to Pred as their
- // source.
- BB->replaceAllUsesWith(OnlyPred);
-
- // Inherit predecessors name if it exists.
- if (!OnlyPred->hasName())
- OnlyPred->takeName(BB);
-
- // Erase basic block from the function.
- M->getBasicBlockList().erase(BB);
-
- return true;
- }
-
- // Otherwise, if this block only has a single predecessor, and if that block
- // is a conditional branch, see if we can hoist any code from this block up
- // into our predecessor.
+
if (OnlyPred)
if (BranchInst *BI = dyn_cast<BranchInst>(OnlyPred->getTerminator()))
if (BI->isConditional()) {
BasicBlock *OtherBB = BI->getSuccessor(BI->getSuccessor(0) == BB);
PI = pred_begin(OtherBB);
++PI;
+
if (PI == pred_end(OtherBB)) {
// We have a conditional branch to two blocks that are only reachable
// from the condbr. We know that the condbr dominates the two blocks,
// blocks. If so, we can hoist it up to the branching block.
Changed |= HoistThenElseCodeToIf(BI);
} else {
- OnlySucc = NULL;
+ BasicBlock* OnlySucc = NULL;
for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB);
SI != SE; ++SI) {
if (!OnlySucc)
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 (isa<PointerType>(CompVal->getType())) {
+ 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);
}
// Erase the old branch instruction.
- (*PI)->getInstList().erase(BI);
-
- // Erase the potentially condition tree that was used to computed the
- // branch condition.
- ErasePossiblyDeadInstructionTree(Cond);
+ EraseTerminatorInstAndDCECond(BI);
return true;
}
}
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, const TargetData *TD) {
+ return SimplifyCFGOpt(TD).run(BB);
+}
projects / oota-llvm.git / blobdiff