//
// The LLVM Compiler Infrastructure
//
-// This file was developed by the LLVM research group and is distributed under
-// the University of Illinois Open Source License. See LICENSE.TXT for details.
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
#include "llvm/Constants.h"
#include "llvm/Instructions.h"
#include "llvm/Type.h"
+#include "llvm/DerivedTypes.h"
#include "llvm/Support/CFG.h"
#include "llvm/Support/Debug.h"
+#include "llvm/Analysis/ConstantFolding.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/Statistic.h"
#include <algorithm>
#include <functional>
#include <set>
#include <map>
using namespace llvm;
+STATISTIC(NumSpeculations, "Number of speculative executed instructions");
+
/// SafeToMergeTerminators - Return true if it is safe to merge these two
/// terminator instructions together.
///
// conflicting incoming values from the two switch blocks.
BasicBlock *SI1BB = SI1->getParent();
BasicBlock *SI2BB = SI2->getParent();
- std::set<BasicBlock*> SI1Succs(succ_begin(SI1BB), succ_end(SI1BB));
+ SmallPtrSet<BasicBlock*, 16> SI1Succs(succ_begin(SI1BB), succ_end(SI1BB));
for (succ_iterator I = succ_begin(SI2BB), E = succ_end(SI2BB); I != E; ++I)
if (SI1Succs.count(*I))
}
}
-// PropagatePredecessorsForPHIs - This gets "Succ" ready to have the
-// predecessors from "BB". This is a little tricky because "Succ" has PHI
-// nodes, which need to have extra slots added to them to hold the merge edges
-// from BB's predecessors, and BB itself might have had PHI nodes in it. This
-// function returns true (failure) if the Succ BB already has a predecessor that
-// is a predecessor of BB and incoming PHI arguments would not be discernible.
+// 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 PropagatePredecessorsForPHIs(BasicBlock *BB, BasicBlock *Succ) {
+static bool CanPropagatePredecessorsForPHIs(BasicBlock *BB, BasicBlock *Succ) {
assert(*succ_begin(BB) == Succ && "Succ is not successor of BB!");
- if (!isa<PHINode>(Succ->front()))
- return false; // We can make the transformation, no problem.
+ 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;
- // If there is more than one predecessor, and there are PHI nodes in
- // the successor, then we need to add incoming edges for the PHI nodes
- //
- const std::vector<BasicBlock*> BBPreds(pred_begin(BB), pred_end(BB));
+ typedef SmallPtrSet<Instruction*, 16> InstrSet;
+ InstrSet BBPHIs;
- // Check to see if one of the predecessors of BB is already a predecessor of
- // Succ. If so, we cannot do the transformation if there are any PHI nodes
- // with incompatible values coming in from the two edges!
- //
- if (!SafeToMergeTerminators(BB->getTerminator(), Succ->getTerminator()))
- return true; // Cannot merge.
+ // 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));
- // Loop over all of the PHI nodes in the successor 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);
- 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)
- PN->addIncoming(OldValPN->getIncomingValue(i),
- OldValPN->getIncomingBlock(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 {
- for (std::vector<BasicBlock*>::const_iterator PredI = BBPreds.begin(),
- End = BBPreds.end(); PredI != End; ++PredI) {
- // Add an incoming value for each of the new incoming values...
- PN->addIncoming(OldVal, *PredI);
+ 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;
+ }
}
}
}
- 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;
}
/// TryToSimplifyUncondBranchFromEmptyBlock - BB contains an unconditional
/// branch. If possible, eliminate BB.
static bool TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB,
BasicBlock *Succ) {
- // If our successor has PHI nodes, then we need to update them to include
- // entries for BB's predecessors, not for BB itself. Be careful though,
- // if this transformation fails (returns true) then we cannot do this
- // transformation!
- //
- if (PropagatePredecessorsForPHIs(BB, Succ)) return false;
+ // 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;
- DEBUG(std::cerr << "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())) {
- std::vector<BasicBlock*>
+ 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() /*|| Succ->getSinglePredecessor() == 0*/) {
- // We can only move the PHI node into Succ if BB dominates Succ.
- // Since BB only has a single successor (Succ), the PHI nodes
- // will dominate Succ, unless Succ has multiple predecessors. In
- // this case, the PHIs are either dead, or have references in dead
- // blocks. In either case, we can just remove them.
- if (!PN->use_empty()) // Uses in dead block?
- PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
- PN->eraseFromParent(); // Nuke instruction.
+ 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 Succ must have
- // *ONLY* had BB as a predecessor, and the PHI node is still valid
- // now. Simply move it into Succ, because we know that BB
- // strictly dominated Succ.
- BB->getInstList().remove(BB->begin());
- Succ->getInstList().push_front(PN);
+ // 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,
- // this means that we should any newly added incoming edges should
- // use the PHI node as the value for these edges, because they are
- // loop back edges.
+ // 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.
- std::string OldName = BB->getName();
BB->replaceAllUsesWith(Succ);
+ if (!Succ->hasName()) Succ->takeName(BB);
BB->eraseFromParent(); // Delete the old basic block.
-
- if (!OldName.empty() && !Succ->hasName()) // Transfer name if we can
- Succ->setName(OldName);
return true;
}
static bool DominatesMergePoint(Value *V, BasicBlock *BB,
std::set<Instruction*> *AggressiveInsts) {
Instruction *I = dyn_cast<Instruction>(V);
- if (!I) return true; // Non-instructions all dominate instructions.
+ if (!I) {
+ // Non-instructions all dominate instructions, but not all constantexprs
+ // can be executed unconditionally.
+ if (ConstantExpr *C = dyn_cast<ConstantExpr>(V))
+ if (C->canTrap())
+ return false;
+ return true;
+ }
BasicBlock *PBB = I->getParent();
// We don't want to allow weird loops that might have the "if condition" in
case Instruction::Or:
case Instruction::Xor:
case Instruction::Shl:
- case Instruction::Shr:
- case Instruction::SetEQ:
- case Instruction::SetNE:
- case Instruction::SetLT:
- case Instruction::SetGT:
- case Instruction::SetLE:
- case Instruction::SetGE:
+ 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.
}
// Okay, we can only really hoist these out if their operands are not
// defined in the conditional region.
- for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
- if (!DominatesMergePoint(I->getOperand(i), BB, 0))
+ for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i)
+ if (!DominatesMergePoint(*i, BB, 0))
return false;
// Okay, it's safe to do this! Remember this instruction.
AggressiveInsts->insert(I);
return true;
}
-// GatherConstantSetEQs - Given a potentially 'or'd together collection of seteq
-// instructions that compare a value against a constant, return the value being
-// compared, and stick the constant into the Values vector.
+// 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){
- if (Instruction *Inst = dyn_cast<Instruction>(V))
- if (Inst->getOpcode() == Instruction::SetEQ) {
+ 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))) {
Values.push_back(C);
return Inst->getOperand(0);
if (LHS == RHS)
return LHS;
}
+ }
return 0;
}
// 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){
- if (Instruction *Inst = dyn_cast<Instruction>(V))
- if (Inst->getOpcode() == Instruction::SetNE) {
+ 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))) {
Values.push_back(C);
return Inst->getOperand(0);
Values.push_back(C);
return Inst->getOperand(1);
}
- } else if (Inst->getOpcode() == Instruction::Cast) {
- // Cast of X to bool is really a comparison against zero.
- assert(Inst->getType() == Type::BoolTy && "Can only handle bool values!");
- Values.push_back(ConstantInt::get(Inst->getOperand(0)->getType(), 0));
- return Inst->getOperand(0);
} else if (Inst->getOpcode() == Instruction::And) {
if (Value *LHS = GatherConstantSetNEs(Inst->getOperand(0), Values))
if (Value *RHS = GatherConstantSetNEs(Inst->getOperand(1), Values))
if (LHS == RHS)
return LHS;
}
+ }
return 0;
}
/// 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)) {
- std::vector<Value*> Operands(I->op_begin(), I->op_end());
- I->getParent()->getInstList().erase(I);
- for (unsigned i = 0, e = Operands.size(); i != e; ++i)
- if (Instruction *OpI = dyn_cast<Instruction>(Operands[i]))
- ErasePossiblyDeadInstructionTree(OpI);
+ 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();
}
}
}
if (BranchInst *BI = dyn_cast<BranchInst>(TI))
if (BI->isConditional() && BI->getCondition()->hasOneUse())
- if (SetCondInst *SCI = dyn_cast<SetCondInst>(BI->getCondition()))
- if ((SCI->getOpcode() == Instruction::SetEQ ||
- SCI->getOpcode() == Instruction::SetNE) &&
- isa<ConstantInt>(SCI->getOperand(1)))
- return SCI->getOperand(0);
+ 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;
}
}
BranchInst *BI = cast<BranchInst>(TI);
- SetCondInst *SCI = cast<SetCondInst>(BI->getCondition());
- Cases.push_back(std::make_pair(cast<ConstantInt>(SCI->getOperand(1)),
- BI->getSuccessor(SCI->getOpcode() ==
- Instruction::SetNE)));
- return BI->getSuccessor(SCI->getOpcode() == Instruction::SetEQ);
+ ICmpInst *ICI = cast<ICmpInst>(BI->getCondition());
+ Cases.push_back(std::make_pair(cast<ConstantInt>(ICI->getOperand(1)),
+ BI->getSuccessor(ICI->getPredicate() ==
+ ICmpInst::ICMP_NE)));
+ return BI->getSuccessor(ICI->getPredicate() == ICmpInst::ICMP_EQ);
}
-// EliminateBlockCases - Given an vector of bb/value pairs, remove any entries
+// 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) {
assert(ThisCases.size() == 1 && "Branch can only have one case!");
Value *Cond = BTI->getCondition();
// Insert the new branch.
- Instruction *NI = new BranchInst(ThisDef, TI);
+ Instruction *NI = BranchInst::Create(ThisDef, TI);
// Remove PHI node entries for the dead edge.
ThisCases[0].second->removePredecessor(TI->getParent());
- DEBUG(std::cerr << "Threading pred instr: " << *Pred->getTerminator()
- << "Through successor TI: " << *TI << "Leaving: " << *NI << "\n");
+ DOUT << "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.
} else {
SwitchInst *SI = cast<SwitchInst>(TI);
// Okay, TI has cases that are statically dead, prune them away.
- std::set<Constant*> DeadCases;
+ SmallPtrSet<Constant*, 16> DeadCases;
for (unsigned i = 0, e = PredCases.size(); i != e; ++i)
DeadCases.insert(PredCases[i].first);
- DEBUG(std::cerr << "Threading pred instr: " << *Pred->getTerminator()
- << "Through successor TI: " << *TI);
+ DOUT << "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);
}
- DEBUG(std::cerr << "Leaving: " << *TI << "\n");
+ DOUT << "Leaving: " << *TI << "\n";
return true;
}
}
ConstantInt *TIV = 0;
BasicBlock *TIBB = TI->getParent();
for (unsigned i = 0, e = PredCases.size(); i != e; ++i)
- if (PredCases[i].second == TIBB)
+ if (PredCases[i].second == TIBB) {
if (TIV == 0)
TIV = PredCases[i].first;
else
return false; // Cannot handle multiple values coming to this block.
+ }
assert(TIV && "No edge from pred to succ?");
// Okay, we found the one constant that our value can be if we get into TI's
CheckEdge = 0;
// Insert the new branch.
- Instruction *NI = new BranchInst(TheRealDest, TI);
+ Instruction *NI = BranchInst::Create(TheRealDest, TI);
- DEBUG(std::cerr << "Threading pred instr: " << *Pred->getTerminator()
- << "Through successor TI: " << *TI << "Leaving: " << *NI << "\n");
+ 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());
assert(CV && "Not a comparison?");
bool Changed = false;
- std::vector<BasicBlock*> Preds(pred_begin(BB), pred_end(BB));
+ SmallVector<BasicBlock*, 16> Preds(pred_begin(BB), pred_end(BB));
while (!Preds.empty()) {
BasicBlock *Pred = Preds.back();
Preds.pop_back();
// Based on whether the default edge from PTI goes to BB or not, fill in
// PredCases and PredDefault with the new switch cases we would like to
// build.
- std::vector<BasicBlock*> NewSuccessors;
+ SmallVector<BasicBlock*, 8> NewSuccessors;
if (PredDefault == BB) {
// If this is the default destination from PTI, only the edges in TI
AddPredecessorToBlock(NewSuccessors[i], Pred, BB);
// Now that the successors are updated, create the new Switch instruction.
- SwitchInst *NewSI = new SwitchInst(CV, PredDefault, PredCases.size(),PTI);
+ 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);
if (InfLoopBlock == 0) {
// Insert it at the end of the loop, because it's either code,
// or it won't matter if it's hot. :)
- InfLoopBlock = new BasicBlock("infloop", BB->getParent());
- new BranchInst(InfLoopBlock, InfLoopBlock);
+ InfLoopBlock = BasicBlock::Create("infloop", BB->getParent());
+ BranchInst::Create(InfLoopBlock, InfLoopBlock);
}
NewSI->setSuccessor(i, InfLoopBlock);
}
return Changed;
}
-/// HoistThenElseCodeToIf - Given a conditional branch that codes to BB1 and
+/// 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.
static bool HoistThenElseCodeToIf(BranchInst *BI) {
BasicBlock *BB2 = BI->getSuccessor(1); // The false destination
Instruction *I1 = BB1->begin(), *I2 = BB2->begin();
- if (I1->getOpcode() != I2->getOpcode() || !I1->isIdenticalTo(I2))
+ if (I1->getOpcode() != I2->getOpcode() || isa<PHINode>(I1) ||
+ isa<InvokeInst>(I1) || !I1->isIdenticalTo(I2))
return false;
// If we get here, we can hoist at least one instruction.
if (NT->getType() != Type::VoidTy) {
I1->replaceAllUsesWith(NT);
I2->replaceAllUsesWith(NT);
- NT->setName(I1->getName());
+ NT->takeName(I1);
}
// Hoisting one of the terminators from our successor is a great thing.
// that determines the right value.
SelectInst *&SI = InsertedSelects[std::make_pair(BB1V, BB2V)];
if (SI == 0)
- SI = new SelectInst(BI->getCondition(), BB1V, BB2V,
- BB1V->getName()+"."+BB2V->getName(), NT);
+ SI = SelectInst::Create(BI->getCondition(), BB1V, BB2V,
+ BB1V->getName()+"."+BB2V->getName(), NT);
// Make the PHI node use the select for all incoming values for BB1/BB2
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
if (PN->getIncomingBlock(i) == BB1 || PN->getIncomingBlock(i) == BB2)
return true;
}
+/// SpeculativelyExecuteBB - Given a conditional branch that goes to BB1
+/// and an BB2 and the only successor of BB1 is BB2, hoist simple code
+/// (for now, restricted to a single instruction that's side effect free) from
+/// the BB1 into the branch block to speculatively execute it.
+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.
+
+ // Be conservative for now. FP select instruction can often be expensive.
+ Value *BrCond = BI->getCondition();
+ if (isa<Instruction>(BrCond) &&
+ cast<Instruction>(BrCond)->getOpcode() == Instruction::FCmp)
+ return false;
+
+ // If BB1 is actually on the false edge of the conditional branch, remember
+ // to swap the select operands later.
+ bool Invert = false;
+ if (BB1 != BI->getSuccessor(0)) {
+ assert(BB1 == BI->getSuccessor(1) && "No edge from 'if' block?");
+ Invert = true;
+ }
+
+ // Turn
+ // BB:
+ // %t1 = icmp
+ // br i1 %t1, label %BB1, label %BB2
+ // BB1:
+ // %t3 = add %t2, c
+ // br label BB2
+ // BB2:
+ // =>
+ // BB:
+ // %t1 = icmp
+ // %t4 = add %t2, c
+ // %t3 = select i1 %t1, %t2, %t3
+ Instruction *I = BB1->begin();
+ switch (I->getOpcode()) {
+ default: return false; // Not safe / profitable to hoist.
+ case Instruction::Add:
+ case Instruction::Sub:
+ 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.
+ return false;
+ break; // These are all cheap and non-trapping instructions.
+ }
+
+ // Can we speculatively execute the instruction? And what is the value
+ // if the condition is false? Consider the phi uses, if the incoming value
+ // from the "if" block are all the same V, then V is the value of the
+ // select if the condition is false.
+ BasicBlock *BIParent = BI->getParent();
+ SmallVector<PHINode*, 4> PHIUses;
+ Value *FalseV = NULL;
+ for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
+ UI != E; ++UI) {
+ PHINode *PN = dyn_cast<PHINode>(UI);
+ if (!PN)
+ continue;
+ 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.
+ }
+ if (!FalseV) // Can this happen?
+ return false;
+
+ // 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) {
+ 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.
+ 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);
+
+ // 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);
+ else
+ SI = SelectInst::Create(BrCond, I, FalseV,
+ I->getName() + "." + FalseV->getName(), BI);
+
+ // Make the PHI node use the select for all incoming values for "then" and
+ // "if" blocks.
+ for (unsigned i = 0, e = PHIUses.size(); i != e; ++i) {
+ PHINode *PN = PHIUses[i];
+ for (unsigned j = 0, ee = PN->getNumIncomingValues(); j != ee; ++j)
+ if (PN->getIncomingBlock(j) == BB1 ||
+ PN->getIncomingBlock(j) == BIParent)
+ PN->setIncomingValue(j, SI);
+ }
+
+ ++NumSpeculations;
+ return true;
+}
+
+/// BlockIsSimpleEnoughToThreadThrough - Return true if we can thread a branch
+/// across this block.
+static bool BlockIsSimpleEnoughToThreadThrough(BasicBlock *BB) {
+ 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) {
+ if (Size > 10) return false; // Don't clone large BB's.
+
+ // We can only support instructions that are 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) {
+ Instruction *U = cast<Instruction>(*UI);
+ if (U->getParent() != BB || isa<PHINode>(U)) return false;
+ }
+
+ // Looks ok, continue checking.
+ }
+
+ return true;
+}
+
+/// FoldCondBranchOnPHI - If we have a conditional branch on a PHI node value
+/// that is defined in the same block as the branch and if any PHI entries are
+/// constants, thread edges corresponding to that entry to be branches to their
+/// ultimate destination.
+static bool FoldCondBranchOnPHI(BranchInst *BI) {
+ BasicBlock *BB = BI->getParent();
+ PHINode *PN = dyn_cast<PHINode>(BI->getCondition());
+ // NOTE: we currently cannot transform this case if the PHI node is used
+ // outside of the block.
+ if (!PN || PN->getParent() != BB || !PN->hasOneUse())
+ return false;
+
+ // 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();
+ return true;
+ }
+
+ // Now we know that this block has multiple preds and two succs.
+ if (!BlockIsSimpleEnoughToThreadThrough(BB)) return false;
+
+ // Okay, this is a simple enough basic block. See if any phi values are
+ // constants.
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
+ ConstantInt *CB;
+ if ((CB = dyn_cast<ConstantInt>(PN->getIncomingValue(i))) &&
+ CB->getType() == Type::Int1Ty) {
+ // Okay, we now know that all edges from PredBB should be revectored to
+ // branch to RealDest.
+ BasicBlock *PredBB = PN->getIncomingBlock(i);
+ BasicBlock *RealDest = BI->getSuccessor(!CB->getZExtValue());
+
+ if (RealDest == BB) continue; // Skip self loops.
+
+ // The dest block might have PHI nodes, other predecessors and other
+ // 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",
+ RealDest->getParent(), RealDest);
+ BranchInst::Create(RealDest, EdgeBB);
+ PHINode *PN;
+ for (BasicBlock::iterator BBI = RealDest->begin();
+ (PN = dyn_cast<PHINode>(BBI)); ++BBI) {
+ Value *V = PN->getIncomingValueForBlock(BB);
+ PN->addIncoming(V, EdgeBB);
+ }
+
+ // BB may have instructions that are being threaded over. Clone these
+ // instructions into EdgeBB. We know that there will be no uses of the
+ // cloned instructions outside of EdgeBB.
+ BasicBlock::iterator InsertPt = EdgeBB->begin();
+ std::map<Value*, Value*> TranslateMap; // Track translated values.
+ for (BasicBlock::iterator BBI = BB->begin(); &*BBI != BI; ++BBI) {
+ if (PHINode *PN = dyn_cast<PHINode>(BBI)) {
+ TranslateMap[PN] = PN->getIncomingValueForBlock(PredBB);
+ } else {
+ // Clone the instruction.
+ Instruction *N = BBI->clone();
+ if (BBI->hasName()) N->setName(BBI->getName()+".c");
+
+ // Update operands due to translation.
+ for (User::op_iterator i = N->op_begin(), e = N->op_end();
+ i != e; ++i) {
+ std::map<Value*, Value*>::iterator PI =
+ TranslateMap.find(*i);
+ if (PI != TranslateMap.end())
+ *i = PI->second;
+ }
+
+ // Check for trivial simplification.
+ if (Constant *C = ConstantFoldInstruction(N)) {
+ TranslateMap[BBI] = C;
+ delete N; // Constant folded away, don't need actual inst
+ } else {
+ // Insert the new instruction into its new home.
+ EdgeBB->getInstList().insert(InsertPt, N);
+ if (!BBI->use_empty())
+ TranslateMap[BBI] = N;
+ }
+ }
+ }
+
+ // Loop over all of the edges from PredBB to BB, changing them to branch
+ // to EdgeBB instead.
+ TerminatorInst *PredBBTI = PredBB->getTerminator();
+ for (unsigned i = 0, e = PredBBTI->getNumSuccessors(); i != e; ++i)
+ if (PredBBTI->getSuccessor(i) == BB) {
+ BB->removePredecessor(PredBB);
+ PredBBTI->setSuccessor(i, EdgeBB);
+ }
+
+ // Recurse, simplifying any other constants.
+ return FoldCondBranchOnPHI(BI) | true;
+ }
+ }
+
+ return false;
+}
+
+/// FoldTwoEntryPHINode - Given a BB that starts with the specified two-entry
+/// PHI node, see if we can eliminate it.
+static bool FoldTwoEntryPHINode(PHINode *PN) {
+ // Ok, this is a two entry PHI node. Check to see if this is a simple "if
+ // statement", which has a very simple dominance structure. Basically, we
+ // are trying to find the condition that is being branched on, which
+ // subsequently causes this merge to happen. We really want control
+ // dependence information for this check, but simplifycfg can't keep it up
+ // to date, and this catches most of the cases we care about anyway.
+ //
+ BasicBlock *BB = PN->getParent();
+ BasicBlock *IfTrue, *IfFalse;
+ Value *IfCond = GetIfCondition(BB, IfTrue, IfFalse);
+ if (!IfCond) return false;
+
+ // Okay, we found that we can merge this two-entry phi node into a select.
+ // Doing so would require us to fold *all* two entry phi nodes in this block.
+ // At some point this becomes non-profitable (particularly if the target
+ // doesn't support cmov's). Only do this transformation if there are two or
+ // fewer PHI nodes in this block.
+ unsigned NumPhis = 0;
+ for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ++NumPhis, ++I)
+ if (NumPhis > 2)
+ return false;
+
+ DOUT << "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
+ // that need to be moved to the dominating block.
+ std::set<Instruction*> AggressiveInsts;
+
+ BasicBlock::iterator AfterPHIIt = BB->begin();
+ while (isa<PHINode>(AfterPHIIt)) {
+ PHINode *PN = cast<PHINode>(AfterPHIIt++);
+ if (PN->getIncomingValue(0) == PN->getIncomingValue(1)) {
+ if (PN->getIncomingValue(0) != PN)
+ PN->replaceAllUsesWith(PN->getIncomingValue(0));
+ else
+ PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
+ } else if (!DominatesMergePoint(PN->getIncomingValue(0), BB,
+ &AggressiveInsts) ||
+ !DominatesMergePoint(PN->getIncomingValue(1), BB,
+ &AggressiveInsts)) {
+ return false;
+ }
+ }
+
+ // If we all PHI nodes are promotable, check to make sure that all
+ // instructions in the predecessor blocks can be promoted as well. If
+ // not, we won't be able to get rid of the control flow, so it's not
+ // worth promoting to select instructions.
+ BasicBlock *DomBlock = 0, *IfBlock1 = 0, *IfBlock2 = 0;
+ PN = cast<PHINode>(BB->begin());
+ BasicBlock *Pred = PN->getIncomingBlock(0);
+ if (cast<BranchInst>(Pred->getTerminator())->isUnconditional()) {
+ IfBlock1 = Pred;
+ DomBlock = *pred_begin(Pred);
+ for (BasicBlock::iterator I = Pred->begin();
+ !isa<TerminatorInst>(I); ++I)
+ if (!AggressiveInsts.count(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 false;
+ }
+ }
+
+ Pred = PN->getIncomingBlock(1);
+ if (cast<BranchInst>(Pred->getTerminator())->isUnconditional()) {
+ IfBlock2 = Pred;
+ DomBlock = *pred_begin(Pred);
+ for (BasicBlock::iterator I = Pred->begin();
+ !isa<TerminatorInst>(I); ++I)
+ if (!AggressiveInsts.count(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 false;
+ }
+ }
+
+ // If we can still promote the PHI nodes after this gauntlet of tests,
+ // do all of the PHI's now.
+
+ // Move all 'aggressive' instructions, which are defined in the
+ // conditional parts of the if's up to the dominating block.
+ if (IfBlock1) {
+ DomBlock->getInstList().splice(DomBlock->getTerminator(),
+ IfBlock1->getInstList(),
+ IfBlock1->begin(),
+ IfBlock1->getTerminator());
+ }
+ if (IfBlock2) {
+ DomBlock->getInstList().splice(DomBlock->getTerminator(),
+ IfBlock2->getInstList(),
+ IfBlock2->begin(),
+ IfBlock2->getTerminator());
+ }
+
+ while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
+ // Change the PHI node into a select instruction.
+ Value *TrueVal =
+ PN->getIncomingValue(PN->getIncomingBlock(0) == IfFalse);
+ Value *FalseVal =
+ PN->getIncomingValue(PN->getIncomingBlock(0) == IfTrue);
+
+ Value *NV = SelectInst::Create(IfCond, TrueVal, FalseVal, "", AfterPHIIt);
+ PN->replaceAllUsesWith(NV);
+ NV->takeName(PN);
+
+ BB->getInstList().erase(PN);
+ }
+ return true;
+}
+
+/// 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.
+static bool SimplifyCondBranchToTwoReturns(BranchInst *BI) {
+ assert(BI->isConditional() && "Must be a conditional branch");
+ BasicBlock *TrueSucc = BI->getSuccessor(0);
+ BasicBlock *FalseSucc = BI->getSuccessor(1);
+ ReturnInst *TrueRet = cast<ReturnInst>(TrueSucc->getTerminator());
+ ReturnInst *FalseRet = cast<ReturnInst>(FalseSucc->getTerminator());
+
+ // 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.
+
+ // Okay, we found a branch that is going to two return nodes. If
+ // there is no return value for this function, just change the
+ // branch into a return.
+ if (FalseRet->getNumOperands() == 0) {
+ TrueSucc->removePredecessor(BI->getParent());
+ FalseSucc->removePredecessor(BI->getParent());
+ ReturnInst::Create(0, BI);
+ BI->eraseFromParent();
+ return true;
+ }
+
+ // Otherwise, build up the result values for the new return.
+ SmallVector<Value*, 4> TrueResult;
+ SmallVector<Value*, 4> FalseResult;
+
+ 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());
+ FalseSucc->removePredecessor(BI->getParent());
+
+ // Insert select instructions where needed.
+ Value *BrCond = BI->getCondition();
+ for (unsigned i = 0, e = TrueRet->getNumOperands(); i != e; ++i) {
+ // 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;
+ }
+
+ TrueResult[i] = SelectInst::Create(BrCond, TrueResult[i],
+ FalseResult[i], "retval", BI);
+ }
+
+ Value *RI = ReturnInst::Create(&TrueResult[0], TrueResult.size(), BI);
+
+ DOUT << "\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);
+ return true;
+}
+
+
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->getRawValue() < RHS->getRawValue();
+ return LHS->getValue().ult(RHS->getValue());
}
};
}
assert(BB && BB->getParent() && "Block not embedded in function!");
assert(BB->getTerminator() && "Degenerate basic block encountered!");
- assert(&BB->getParent()->front() != BB && "Can't Simplify entry block!");
+ 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)) {
- DEBUG(std::cerr << "Removing BB: \n" << *BB);
+ 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.
// away...
Changed |= ConstantFoldTerminator(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()))
+ if (PN->getNumIncomingValues() == 2)
+ Changed |= FoldTwoEntryPHINode(PN);
+
// If this is a returning block with only PHI nodes in it, fold the return
// instruction into any unconditional branch predecessors.
//
BasicBlock::iterator BBI = BB->getTerminator();
if (BBI == BB->begin() || isa<PHINode>(--BBI)) {
// Find predecessors that end with branches.
- std::vector<BasicBlock*> UncondBranchPreds;
- std::vector<BranchInst*> CondBranchPreds;
+ 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();
- if (BranchInst *BI = dyn_cast<BranchInst>(PTI))
+ if (BranchInst *BI = dyn_cast<BranchInst>(PTI)) {
if (BI->isUnconditional())
UncondBranchPreds.push_back(*PI);
else
CondBranchPreds.push_back(BI);
+ }
}
// 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();
Instruction *UncondBranch = Pred->getTerminator();
// Clone the return and add it to the end of the predecessor.
// If the return instruction returns a value, and if the value was a
// PHI node in "BB", propagate the right value into the return.
- if (NewRet->getNumOperands() == 1)
- if (PHINode *PN = dyn_cast<PHINode>(NewRet->getOperand(0)))
+ for (User::op_iterator i = NewRet->op_begin(), e = NewRet->op_end();
+ i != e; ++i)
+ if (PHINode *PN = dyn_cast<PHINode>(*i))
if (PN->getParent() == BB)
- NewRet->setOperand(0, PN->getIncomingValueForBlock(Pred));
+ *i = PN->getIncomingValueForBlock(Pred);
+
// Update any PHI nodes in the returning block to realize that we no
// longer branch to them.
BB->removePredecessor(Pred);
while (!CondBranchPreds.empty()) {
BranchInst *BI = CondBranchPreds.back();
CondBranchPreds.pop_back();
- BasicBlock *TrueSucc = BI->getSuccessor(0);
- BasicBlock *FalseSucc = BI->getSuccessor(1);
- BasicBlock *OtherSucc = TrueSucc == BB ? FalseSucc : TrueSucc;
// Check to see if the non-BB successor is also a return block.
- if (isa<ReturnInst>(OtherSucc->getTerminator())) {
- // Check to see if there are only PHI instructions in this block.
- BasicBlock::iterator OSI = OtherSucc->getTerminator();
- if (OSI == OtherSucc->begin() || isa<PHINode>(--OSI)) {
- // Okay, we found a branch that is going to two return nodes. If
- // there is no return value for this function, just change the
- // branch into a return.
- if (RI->getNumOperands() == 0) {
- TrueSucc->removePredecessor(BI->getParent());
- FalseSucc->removePredecessor(BI->getParent());
- new ReturnInst(0, BI);
- BI->getParent()->getInstList().erase(BI);
- return true;
- }
-
- // Otherwise, figure out what the true and false return values are
- // so we can insert a new select instruction.
- Value *TrueValue = TrueSucc->getTerminator()->getOperand(0);
- Value *FalseValue = FalseSucc->getTerminator()->getOperand(0);
-
- // 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());
-
- TrueSucc->removePredecessor(BI->getParent());
- FalseSucc->removePredecessor(BI->getParent());
-
- // Insert a new select instruction.
- Value *NewRetVal;
- Value *BrCond = BI->getCondition();
- if (TrueValue != FalseValue)
- NewRetVal = new SelectInst(BrCond, TrueValue,
- FalseValue, "retval", BI);
- else
- NewRetVal = TrueValue;
-
- new ReturnInst(NewRetVal, BI);
- BI->getParent()->getInstList().erase(BI);
- if (BrCond->use_empty())
- if (Instruction *BrCondI = dyn_cast<Instruction>(BrCond))
- BrCondI->getParent()->getInstList().erase(BrCondI);
- return true;
- }
- }
+ if (isa<ReturnInst>(BI->getSuccessor(0)->getTerminator()) &&
+ isa<ReturnInst>(BI->getSuccessor(1)->getTerminator()) &&
+ SimplifyCondBranchToTwoReturns(BI))
+ return true;
}
}
- } else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->begin())) {
+ } 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.
//
- std::vector<BasicBlock*> Preds(pred_begin(BB), pred_end(BB));
+ 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 (II->getUnwindDest() == BB) {
// Insert a new branch instruction before the invoke, because this
// is now a fall through...
- BranchInst *BI = new BranchInst(II->getNormalDest(), II);
+ BranchInst *BI = BranchInst::Create(II->getNormalDest(), II);
Pred->getInstList().remove(II); // Take out of symbol table
// Insert the call now...
- std::vector<Value*> Args(II->op_begin()+3, II->op_end());
- CallInst *CI = new CallInst(II->getCalledValue(), Args,
- II->getName(), BI);
+ 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
II->replaceAllUsesWith(CI);
delete II;
}
} else if (BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator())) {
if (BI->isUnconditional()) {
- BasicBlock::iterator BBI = BB->begin(); // Skip over phi nodes...
- while (isa<PHINode>(*BBI)) ++BBI;
+ BasicBlock::iterator BBI = BB->getFirstNonPHI();
BasicBlock *Succ = BI->getSuccessor(0);
if (BBI->isTerminator() && // Terminator is the only non-phi instruction!
return 1;
} else { // Conditional branch
- if (Value *CompVal = isValueEqualityComparison(BI)) {
+ if (isValueEqualityComparison(BI)) {
// If we only have one predecessor, and if it is a branch on this value,
// see if that predecessor totally determines the outcome of this
// switch.
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 (PN->getParent() == BI->getParent())
+ if (FoldCondBranchOnPHI(BI))
+ return SimplifyCFG(BB) | true;
// 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 (BinaryOperator *Cond = dyn_cast<BinaryOperator>(BI->getCondition()))
- if (Cond->getParent() == BB && &BB->front() == Cond &&
- Cond->getNext() == BI && Cond->hasOneUse() &&
+ 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()))
// Invert the predecessors condition test (xor it with true),
// which allows us to write this code once.
Value *NewCond =
- BinaryOperator::createNot(PBI->getCondition(),
+ BinaryOperator::CreateNot(PBI->getCondition(),
PBI->getCondition()->getName()+".not", PBI);
PBI->setCondition(NewCond);
BasicBlock *OldTrue = PBI->getSuccessor(0);
PBI->setSuccessor(1, OldTrue);
}
- if (PBI->getSuccessor(0) == TrueDest ||
- PBI->getSuccessor(1) == FalseDest) {
+ 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();
- New->setName(Cond->getName());
- Cond->setName(Cond->getName()+".old");
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(),
+ BinaryOperator::Create(Opcode, PBI->getCondition(),
New, "bothcond", PBI);
PBI->setCondition(NewCond);
if (PBI->getSuccessor(0) == BB) {
return SimplifyCFG(BB) | 1;
}
}
+ }
- // If this block ends with a branch instruction, and if there is one
- // predecessor, see if the previous block ended with a branch on the same
- // condition, which makes this conditional branch redundant.
- if (BasicBlock *OnlyPred = BB->getSinglePredecessor())
- if (BranchInst *PBI = dyn_cast<BranchInst>(OnlyPred->getTerminator()))
- if (PBI->isConditional() &&
- PBI->getCondition() == BI->getCondition() &&
- (PBI->getSuccessor(0) != BB || PBI->getSuccessor(1) != BB)) {
- // Okay, the outcome of this conditional branch is statically
- // knowable. Delete the outgoing CFG edge that is impossible to
- // execute.
- bool CondIsTrue = PBI->getSuccessor(0) == BB;
- BI->getSuccessor(CondIsTrue)->removePredecessor(BB);
- new BranchInst(BI->getSuccessor(!CondIsTrue), BB);
- BB->getInstList().erase(BI);
- return SimplifyCFG(BB) | true;
+ // Scan predessor 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;
+ }
+ }
}
}
} else if (isa<UnreachableInst>(BB->getTerminator())) {
// If the unreachable instruction is the first in the block, take a gander
// at all of the predecessors of this instruction, and simplify them.
if (&BB->front() == Unreachable) {
- std::vector<BasicBlock*> Preds(pred_begin(BB), pred_end(BB));
+ SmallVector<BasicBlock*, 8> Preds(pred_begin(BB), pred_end(BB));
for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
TerminatorInst *TI = Preds[i]->getTerminator();
}
} else {
if (BI->getSuccessor(0) == BB) {
- new BranchInst(BI->getSuccessor(1), BI);
+ BranchInst::Create(BI->getSuccessor(1), BI);
BI->eraseFromParent();
} else if (BI->getSuccessor(1) == BB) {
- new BranchInst(BI->getSuccessor(0), BI);
+ BranchInst::Create(BI->getSuccessor(0), BI);
BI->eraseFromParent();
Changed = true;
}
if (II->getUnwindDest() == BB) {
// Convert the invoke to a call instruction. This would be a good
// place to note that the call does not throw though.
- BranchInst *BI = new BranchInst(II->getNormalDest(), II);
+ BranchInst *BI = BranchInst::Create(II->getNormalDest(), II);
II->removeFromParent(); // Take out of symbol table
// Insert the call now...
- std::vector<Value*> Args(II->op_begin()+3, II->op_end());
- CallInst *CI = new CallInst(II->getCalledValue(), Args,
- II->getName(), BI);
+ 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 does now instead.
II->replaceAllUsesWith(CI);
delete II;
}
if (OnlySucc) {
- DEBUG(std::cerr << "Merging: " << *BB << "into: " << *OnlyPred);
- TerminatorInst *Term = OnlyPred->getTerminator();
+ 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
//
while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
PN->replaceAllUsesWith(PN->getIncomingValue(0));
- BB->getInstList().pop_front(); // Delete the phi node...
+ BB->getInstList().pop_front(); // Delete the phi node.
}
- // Delete the unconditional branch from the predecessor...
+ // Delete the unconditional branch from the predecessor.
OnlyPred->getInstList().pop_back();
- // Move all definitions in the successor to the predecessor...
+ // 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...
+ // source.
BB->replaceAllUsesWith(OnlyPred);
- std::string OldName = BB->getName();
-
- // Erase basic block from the function...
+ // Inherit predecessors name if it exists.
+ if (!OnlyPred->hasName())
+ OnlyPred->takeName(BB);
+
+ // Erase basic block from the function.
M->getBasicBlockList().erase(BB);
- // Inherit predecessors name if it exists...
- if (!OldName.empty() && !OnlyPred->hasName())
- OnlyPred->setName(OldName);
-
return true;
}
// so see if there is any identical code in the "then" and "else"
// blocks. If so, we can hoist it up to the branching block.
Changed |= HoistThenElseCodeToIf(BI);
+ } else {
+ OnlySucc = NULL;
+ for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB);
+ SI != SE; ++SI) {
+ if (!OnlySucc)
+ OnlySucc = *SI;
+ else if (*SI != OnlySucc) {
+ OnlySucc = 0; // There are multiple distinct successors!
+ break;
+ }
+ }
+
+ if (OnlySucc == OtherBB) {
+ // If BB's only successor is the other successor of the predecessor,
+ // i.e. a triangle, see if we can hoist any code from this block up
+ // to the "if" block.
+ Changed |= SpeculativelyExecuteBB(BI, BB);
+ }
}
}
if (!TrueWhenEqual) std::swap(DefaultBB, EdgeBB);
// Create the new switch instruction now.
- SwitchInst *New = new SwitchInst(CompVal, DefaultBB,Values.size(),BI);
+ SwitchInst *New = SwitchInst::Create(CompVal, DefaultBB,
+ Values.size(), BI);
// Add all of the 'cases' to the switch instruction.
for (unsigned i = 0, e = Values.size(); i != e; ++i)
}
}
- // 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()))
- if (PN->getNumIncomingValues() == 2) {
- // Ok, this is a two entry PHI node. Check to see if this is a simple "if
- // statement", which has a very simple dominance structure. Basically, we
- // are trying to find the condition that is being branched on, which
- // subsequently causes this merge to happen. We really want control
- // dependence information for this check, but simplifycfg can't keep it up
- // to date, and this catches most of the cases we care about anyway.
- //
- BasicBlock *IfTrue, *IfFalse;
- if (Value *IfCond = GetIfCondition(BB, IfTrue, IfFalse)) {
- DEBUG(std::cerr << "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
- // that need to be moved to the dominating block.
- std::set<Instruction*> AggressiveInsts;
- bool CanPromote = true;
-
- BasicBlock::iterator AfterPHIIt = BB->begin();
- while (isa<PHINode>(AfterPHIIt)) {
- PHINode *PN = cast<PHINode>(AfterPHIIt++);
- if (PN->getIncomingValue(0) == PN->getIncomingValue(1)) {
- if (PN->getIncomingValue(0) != PN)
- PN->replaceAllUsesWith(PN->getIncomingValue(0));
- else
- PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
- } else if (!DominatesMergePoint(PN->getIncomingValue(0), BB,
- &AggressiveInsts) ||
- !DominatesMergePoint(PN->getIncomingValue(1), BB,
- &AggressiveInsts)) {
- CanPromote = false;
- break;
- }
- }
-
- // Did we eliminate all PHI's?
- CanPromote |= AfterPHIIt == BB->begin();
-
- // If we all PHI nodes are promotable, check to make sure that all
- // instructions in the predecessor blocks can be promoted as well. If
- // not, we won't be able to get rid of the control flow, so it's not
- // worth promoting to select instructions.
- BasicBlock *DomBlock = 0, *IfBlock1 = 0, *IfBlock2 = 0;
- if (CanPromote) {
- PN = cast<PHINode>(BB->begin());
- BasicBlock *Pred = PN->getIncomingBlock(0);
- if (cast<BranchInst>(Pred->getTerminator())->isUnconditional()) {
- IfBlock1 = Pred;
- DomBlock = *pred_begin(Pred);
- for (BasicBlock::iterator I = Pred->begin();
- !isa<TerminatorInst>(I); ++I)
- if (!AggressiveInsts.count(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.
- CanPromote = false;
- break;
- }
- }
-
- Pred = PN->getIncomingBlock(1);
- if (CanPromote &&
- cast<BranchInst>(Pred->getTerminator())->isUnconditional()) {
- IfBlock2 = Pred;
- DomBlock = *pred_begin(Pred);
- for (BasicBlock::iterator I = Pred->begin();
- !isa<TerminatorInst>(I); ++I)
- if (!AggressiveInsts.count(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.
- CanPromote = false;
- break;
- }
- }
- }
-
- // If we can still promote the PHI nodes after this gauntlet of tests,
- // do all of the PHI's now.
- if (CanPromote) {
- // Move all 'aggressive' instructions, which are defined in the
- // conditional parts of the if's up to the dominating block.
- if (IfBlock1) {
- DomBlock->getInstList().splice(DomBlock->getTerminator(),
- IfBlock1->getInstList(),
- IfBlock1->begin(),
- IfBlock1->getTerminator());
- }
- if (IfBlock2) {
- DomBlock->getInstList().splice(DomBlock->getTerminator(),
- IfBlock2->getInstList(),
- IfBlock2->begin(),
- IfBlock2->getTerminator());
- }
-
- while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
- // Change the PHI node into a select instruction.
- Value *TrueVal =
- PN->getIncomingValue(PN->getIncomingBlock(0) == IfFalse);
- Value *FalseVal =
- PN->getIncomingValue(PN->getIncomingBlock(0) == IfTrue);
-
- std::string Name = PN->getName(); PN->setName("");
- PN->replaceAllUsesWith(new SelectInst(IfCond, TrueVal, FalseVal,
- Name, AfterPHIIt));
- BB->getInstList().erase(PN);
- }
- Changed = true;
- }
- }
- }
-
return Changed;
}
projects / oota-llvm.git / blobdiff