#include "llvm/Constants.h"
#include "llvm/Instructions.h"
#include "llvm/IntrinsicInst.h"
-#include "llvm/LLVMContext.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/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/ADT/SmallVector.h"
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";
+ DEBUG(errs() << "Looking to fold " << BB->getName() << " into "
+ << Succ->getName() << "\n");
// Shortcut, if there is only a single predecessor it must be BB and merging
// is always safe
if (Succ->getSinglePredecessor()) return true;
- 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));
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";
+ DEBUG(errs() << "Can't fold, phi node " << PN->getName() << " in "
+ << Succ->getName() << " is conflicting with "
+ << BBPN->getName() << " with regard to common predecessor "
+ << (*PI)->getName() << "\n");
return false;
}
}
- // 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();
// 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";
+ DEBUG(errs() << "Can't fold, phi node " << PN->getName() << " in "
+ << Succ->getName() << " is conflicting with regard to common "
+ << "predecessor " << (*PI)->getName() << "\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;
}
// 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;
+
+ // Check for cases where Succ has multiple predecessors and a PHI node in BB
+ // has uses which will not disappear when the PHI nodes are merged. It is
+ // possible to handle such cases, but difficult: it requires checking whether
+ // BB dominates Succ, which is non-trivial to calculate in the case where
+ // Succ has multiple predecessors. Also, it requires checking whether
+ // constructing the necessary self-referential PHI node doesn't intoduce any
+ // conflicts; this isn't too difficult, but the previous code for doing this
+ // was incorrect.
+ //
+ // Note that if this check finds a live use, BB dominates Succ, so BB is
+ // something like a loop pre-header (or rarely, a part of an irreducible CFG);
+ // folding the branch isn't profitable in that case anyway.
+ if (!Succ->getSinglePredecessor()) {
+ BasicBlock::iterator BBI = BB->begin();
+ while (isa<PHINode>(*BBI)) {
+ for (Value::use_iterator UI = BBI->use_begin(), E = BBI->use_end();
+ UI != E; ++UI) {
+ if (PHINode* PN = dyn_cast<PHINode>(*UI)) {
+ if (PN->getIncomingBlock(UI) != BB)
+ return false;
+ } else {
+ return false;
+ }
+ }
+ ++BBI;
+ }
+ }
+
+ DEBUG(errs() << "Killing Trivial BB: \n" << *BB);
if (isa<PHINode>(Succ->begin())) {
// If there is more than one pred of succ, and there are PHI nodes in
}
}
- 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();
- continue;
- }
-
- // 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.
+ while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
+ if (Succ->getSinglePredecessor()) {
+ // BB is the only predecessor of Succ, so Succ will end up with exactly
+ // the same predecessors BB had.
Succ->getInstList().splice(Succ->begin(),
BB->getInstList(), BB->begin());
-
- // 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]);
+ } else {
+ // We explicitly check for such uses in CanPropagatePredecessorsForPHIs.
+ assert(PN->use_empty() && "There shouldn't be any uses here!");
+ PN->eraseFromParent();
}
}
// 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;
- // FIXME: A computation of a constant can trap!
- if (!isa<AllocaInst>(I->getOperand(0)) &&
- !isa<Constant>(I->getOperand(0)))
- return false;
- // External weak globals may have address 0, so we can't load them.
- Value *V2 = I->getOperand(0)->getUnderlyingObject();
- if (V2) {
- GlobalVariable* GV = dyn_cast<GlobalVariable>(V2);
- if (GV && GV->hasExternalWeakLinkage())
- 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.
+ // 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++;
assert(ThisCases.size() == 1 && "Branch can only have one case!");
// 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(errs() << "Threading pred instr: " << *Pred->getTerminator()
+ << "Through successor TI: " << *TI << "Leaving: " << *NI << "\n");
EraseTerminatorInstAndDCECond(TI);
return true;
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(errs() << "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(errs() << "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";
+ DEBUG(errs() << "Threading pred instr: " << *Pred->getTerminator()
+ << "Through successor TI: " << *TI << "Leaving: " << *NI << "\n");
EraseTerminatorInstAndDCECond(TI);
return true;
if (InfLoopBlock == 0) {
// 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);
while (isa<DbgInfoIntrinsic>(I2))
I2 = BB2_Itr++;
if (I1->getOpcode() != I2->getOpcode() || isa<PHINode>(I1) ||
- !I1->isIdenticalTo(I2) ||
+ !I1->isIdenticalToWhenDefined(I2) ||
(isa<InvokeInst>(I1) && !isSafeToHoistInvoke(BB1, BB2, I1, I2)))
return false;
BIParent->getInstList().splice(BI, BB1->getInstList(), I1);
if (!I2->use_empty())
I2->replaceAllUsesWith(I1);
+ I1->intersectOptionalDataWith(I2);
BB2->getInstList().erase(I2);
I1 = BB1_Itr++;
I2 = BB2_Itr++;
while (isa<DbgInfoIntrinsic>(I2))
I2 = BB2_Itr++;
- } while (I1->getOpcode() == I2->getOpcode() && I1->isIdenticalTo(I2));
+ } while (I1->getOpcode() == I2->getOpcode() &&
+ I1->isIdenticalToWhenDefined(I2));
return true;
return true;
// Okay, it is safe to hoist the terminator.
- Instruction *NT = I1->clone(*BB1->getContext());
+ Instruction *NT = I1->clone();
BIParent->getInstList().insert(BI, NT);
- if (NT->getType() != Type::VoidTy) {
+ if (NT->getType() != Type::getVoidTy(BB1->getContext())) {
I1->replaceAllUsesWith(NT);
I2->replaceAllUsesWith(NT);
NT->takeName(I1);
/// ultimate destination.
static bool FoldCondBranchOnPHI(BranchInst *BI) {
BasicBlock *BB = BI->getParent();
- LLVMContext *Context = BB->getContext();
PHINode *PN = dyn_cast<PHINode>(BI->getCondition());
// NOTE: we currently cannot transform this case if the PHI node is used
// outside of the block.
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() == Type::getInt1Ty(BB->getContext())) {
// 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;
TranslateMap[PN] = PN->getIncomingValueForBlock(PredBB);
} else {
// Clone the instruction.
- Instruction *N = BBI->clone(*Context);
+ Instruction *N = BBI->clone();
if (BBI->hasName()) N->setName(BBI->getName()+".c");
// Update operands due to translation.
}
// Check for trivial simplification.
- if (Constant *C = ConstantFoldInstruction(N, Context)) {
+ if (Constant *C = ConstantFoldInstruction(N, BB->getContext())) {
TranslateMap[BBI] = C;
delete N; // Constant folded away, don't need actual inst
} else {
/// FoldTwoEntryPHINode - Given a BB that starts with the specified two-entry
/// PHI node, see if we can eliminate it.
static bool FoldTwoEntryPHINode(PHINode *PN) {
- LLVMContext *Context = PN->getParent()->getContext();
-
// 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
if (NumPhis > 2)
return false;
- DOUT << "FOUND IF CONDITION! " << *IfCond << " T: "
- << IfTrue->getName() << " F: " << IfFalse->getName() << "\n";
+ DEBUG(errs() << "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
if (PN->getIncomingValue(0) != PN)
PN->replaceAllUsesWith(PN->getIncomingValue(0));
else
- PN->replaceAllUsesWith(Context->getUndef(PN->getType()));
+ PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
} else if (!DominatesMergePoint(PN->getIncomingValue(0), BB,
&AggressiveInsts) ||
!DominatesMergePoint(PN->getIncomingValue(1), BB,
if (FalseRet->getNumOperands() == 0) {
TrueSucc->removePredecessor(BI->getParent());
FalseSucc->removePredecessor(BI->getParent());
- ReturnInst::Create(0, BI);
+ ReturnInst::Create(BI->getContext(), 0, BI);
EraseTerminatorInstAndDCECond(BI);
return true;
}
}
Value *RI = !TrueValue ?
- ReturnInst::Create(BI) :
- ReturnInst::Create(TrueValue, BI);
+ 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(errs() << "\nCHANGING BRANCH TO TWO RETURNS INTO SELECT:"
+ << "\n " << *BI << "NewRet = " << *RI
+ << "TRUEBLOCK: " << *TrueSucc << "FALSEBLOCK: "<< *FalseSucc);
EraseTerminatorInstAndDCECond(BI);
else
continue;
- DOUT << "FOLDING BRANCH TO COMMON DEST:\n" << *PBI << *BB;
+ DEBUG(errs() << "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(*BI->getParent()->getContext(),
- PBI->getCondition(),
+ BinaryOperator::CreateNot(PBI->getCondition(),
PBI->getCondition()->getName()+".not", PBI);
PBI->setCondition(NewCond);
BasicBlock *OldTrue = PBI->getSuccessor(0);
// Clone Cond into the predecessor basic block, and or/and the
// two conditions together.
- Instruction *New = Cond->clone(*BB->getContext());
+ Instruction *New = Cond->clone();
PredBlock->getInstList().insert(PBI, New);
New->takeName(Cond);
Cond->setName(New->getName()+".old");
static bool SimplifyCondBranchToCondBranch(BranchInst *PBI, BranchInst *BI) {
assert(PBI->isConditional() && BI->isConditional());
BasicBlock *BB = BI->getParent();
- LLVMContext *Context = BB->getContext();
-
+
// 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 (BB->getSinglePredecessor()) {
// Turn this into a branch on constant.
bool CondIsTrue = PBI->getSuccessor(0) == BB;
- BI->setCondition(Context->getConstantInt(Type::Int1Ty, CondIsTrue));
+ BI->setCondition(ConstantInt::get(Type::getInt1Ty(BB->getContext()),
+ CondIsTrue));
return true; // Nuke the branch on constant.
}
// in the constant and simplify the block result. Subsequent passes of
// simplifycfg will thread the block.
if (BlockIsSimpleEnoughToThreadThrough(BB)) {
- PHINode *NewPN = PHINode::Create(Type::Int1Ty,
+ 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
PBI->getCondition() == BI->getCondition() &&
PBI->getSuccessor(0) != PBI->getSuccessor(1)) {
bool CondIsTrue = PBI->getSuccessor(0) == BB;
- NewPN->addIncoming(Context->getConstantInt(Type::Int1Ty,
+ NewPN->addIncoming(ConstantInt::get(Type::getInt1Ty(BB->getContext()),
CondIsTrue), *PI);
} else {
NewPN->addIncoming(BI->getCondition(), *PI);
// Finally, if everything is ok, fold the branches to logical ops.
BasicBlock *OtherDest = BI->getSuccessor(BIOp ^ 1);
- DOUT << "FOLDING BRs:" << *PBI->getParent()
- << "AND: " << *BI->getParent();
+ DEBUG(errs() << "FOLDING BRs:" << *PBI->getParent()
+ << "AND: " << *BI->getParent());
// If OtherDest *is* BB, then BB is a basic block with a single conditional
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("infloop", BB->getParent());
+ BasicBlock *InfLoopBlock = BasicBlock::Create(BB->getContext(),
+ "infloop", BB->getParent());
BranchInst::Create(InfLoopBlock, InfLoopBlock);
OtherDest = InfLoopBlock;
}
- DOUT << *PBI->getParent()->getParent();
+ DEBUG(errs() << *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(*Context, PBICond,
+ PBICond = BinaryOperator::CreateNot(PBICond,
PBICond->getName()+".not",
PBI);
Value *BICond = BI->getCondition();
if (BIOp)
- BICond = BinaryOperator::CreateNot(*Context, BICond,
+ BICond = BinaryOperator::CreateNot(BICond,
BICond->getName()+".not",
PBI);
// Merge the conditions.
}
}
- DOUT << "INTO: " << *PBI->getParent();
-
- DOUT << *PBI->getParent()->getParent();
+ DEBUG(errs() << "INTO: " << *PBI->getParent());
+ DEBUG(errs() << *PBI->getParent()->getParent());
// This basic block is probably dead. We know it has at least
// one fewer predecessor.
// 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) {
- DOUT << "Removing BB: \n" << *BB;
+ DEBUG(errs() << "Removing BB: \n" << *BB);
DeleteDeadBlock(BB);
return true;
}
if (!UncondBranchPreds.empty()) {
while (!UncondBranchPreds.empty()) {
BasicBlock *Pred = UncondBranchPreds.pop_back_val();
- DOUT << "FOLDING: " << *BB
- << "INTO UNCOND BRANCH PRED: " << *Pred;
+ DEBUG(errs() << "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(*BB->getContext());
+ Instruction *NewRet = RI->clone();
Pred->getInstList().push_back(NewRet);
BasicBlock::iterator BBI = RI;
if (BranchInst *BI = dyn_cast<BranchInst>(Pred->getTerminator())) {
if (BI->isUnconditional()) {
Pred->getInstList().pop_back(); // nuke uncond branch
- new UnwindInst(Pred); // Use unwind.
+ new UnwindInst(Pred->getContext(), Pred); // Use unwind.
Changed = true;
}
} else if (InvokeInst *II = dyn_cast<InvokeInst>(Pred->getTerminator()))
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;
}
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