#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/raw_ostream.h"
#include "llvm/Analysis/ConstantFolding.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"
PN->addIncoming(PN->getIncomingValueForBlock(ExistPred), NewPred);
}
-/// CanPropagatePredecessorsForPHIs - Return true if we can fold BB, an
-/// almost-empty BB ending in an unconditional branch to Succ, into succ.
-///
-/// Assumption: Succ is the single successor for BB.
-///
-static bool CanPropagatePredecessorsForPHIs(BasicBlock *BB, BasicBlock *Succ) {
- assert(*succ_begin(BB) == Succ && "Succ is not successor of BB!");
-
- DEBUG(errs() << "Looking to fold " << BB->getName() << " into "
- << Succ->getName() << "\n");
- // Shortcut, if there is only a single predecessor it must be BB and merging
- // is always safe
- if (Succ->getSinglePredecessor()) return true;
-
- // Make a list of the predecessors of BB
- typedef SmallPtrSet<BasicBlock*, 16> BlockSet;
- BlockSet BBPreds(pred_begin(BB), pred_end(BB));
-
- // Use that list to make another list of common predecessors of BB and Succ
- BlockSet CommonPreds;
- for (pred_iterator PI = pred_begin(Succ), PE = pred_end(Succ);
- PI != PE; ++PI)
- if (BBPreds.count(*PI))
- CommonPreds.insert(*PI);
-
- // Shortcut, if there are no common predecessors, merging is always safe
- if (CommonPreds.empty())
- return true;
-
- // Look at all the phi nodes in Succ, to see if they present a conflict when
- // merging these blocks
- for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
- PHINode *PN = cast<PHINode>(I);
-
- // If the incoming value from BB is again a PHINode in
- // BB which has the same incoming value for *PI as PN does, we can
- // merge the phi nodes and then the blocks can still be merged
- PHINode *BBPN = dyn_cast<PHINode>(PN->getIncomingValueForBlock(BB));
- if (BBPN && BBPN->getParent() == BB) {
- for (BlockSet::iterator PI = CommonPreds.begin(), PE = CommonPreds.end();
- PI != PE; PI++) {
- if (BBPN->getIncomingValueForBlock(*PI)
- != PN->getIncomingValueForBlock(*PI)) {
- DEBUG(errs() << "Can't fold, phi node " << PN->getName() << " in "
- << Succ->getName() << " is conflicting with "
- << BBPN->getName() << " with regard to common predecessor "
- << (*PI)->getName() << "\n");
- return false;
- }
- }
- } else {
- Value* Val = PN->getIncomingValueForBlock(BB);
- for (BlockSet::iterator PI = CommonPreds.begin(), PE = CommonPreds.end();
- PI != PE; PI++) {
- // See if the incoming value for the common predecessor is equal to the
- // one for BB, in which case this phi node will not prevent the merging
- // of the block.
- if (Val != PN->getIncomingValueForBlock(*PI)) {
- DEBUG(errs() << "Can't fold, phi node " << PN->getName() << " in "
- << Succ->getName() << " is conflicting with regard to common "
- << "predecessor " << (*PI)->getName() << "\n");
- return false;
- }
- }
- }
- }
-
- return true;
-}
-
-/// TryToSimplifyUncondBranchFromEmptyBlock - BB contains an unconditional
-/// branch to Succ, and contains no instructions other than PHI nodes and the
-/// branch. If possible, eliminate BB.
-static bool TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB,
- BasicBlock *Succ) {
- // Check to see if merging these blocks would cause conflicts for any of the
- // phi nodes in BB or Succ. If not, we can safely merge.
- if (!CanPropagatePredecessorsForPHIs(BB, Succ)) return false;
-
- // Check for cases where Succ has multiple predecessors and a PHI node in BB
- // has uses which will not disappear when the PHI nodes are merged. It is
- // possible to handle such cases, but difficult: it requires checking whether
- // BB dominates Succ, which is non-trivial to calculate in the case where
- // Succ has multiple predecessors. Also, it requires checking whether
- // constructing the necessary self-referential PHI node doesn't intoduce any
- // conflicts; this isn't too difficult, but the previous code for doing this
- // was incorrect.
- //
- // Note that if this check finds a live use, BB dominates Succ, so BB is
- // something like a loop pre-header (or rarely, a part of an irreducible CFG);
- // folding the branch isn't profitable in that case anyway.
- if (!Succ->getSinglePredecessor()) {
- BasicBlock::iterator BBI = BB->begin();
- while (isa<PHINode>(*BBI)) {
- for (Value::use_iterator UI = BBI->use_begin(), E = BBI->use_end();
- UI != E; ++UI) {
- if (PHINode* PN = dyn_cast<PHINode>(*UI)) {
- if (PN->getIncomingBlock(UI) != BB)
- return false;
- } else {
- return false;
- }
- }
- ++BBI;
- }
- }
-
- 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]);
- }
- }
- }
-
- while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
- if (Succ->getSinglePredecessor()) {
- // BB is the only predecessor of Succ, so Succ will end up with exactly
- // the same predecessors BB had.
- Succ->getInstList().splice(Succ->begin(),
- BB->getInstList(), BB->begin());
- } else {
- // We explicitly check for such uses in CanPropagatePredecessorsForPHIs.
- assert(PN->use_empty() && "There shouldn't be any uses here!");
- PN->eraseFromParent();
- }
- }
-
- // Everything that jumped to BB now goes to Succ.
- BB->replaceAllUsesWith(Succ);
- if (!Succ->hasName()) Succ->takeName(BB);
- BB->eraseFromParent(); // Delete the old basic block.
- return true;
-}
/// GetIfCondition - Given a basic block (BB) with two predecessors (and
/// presumably PHI nodes in it), check to see if the merge at this block is due
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;
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::getVoidTy(BB1->getContext())) {
I1->replaceAllUsesWith(NT);
/// 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.
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)) {
TranslateMap[BBI] = C;
delete N; // Constant folded away, don't need actual inst
} else {
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(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) {
// 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");
// 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
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.
}
}
- 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.
return true;
}
-
/// 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
// 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;
}
// 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()))
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;
} 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->getContext(), 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->setAttributes(II->getAttributes());
- // If the invoke produced a value, the Call now does instead
+ // If the invoke produced a value, the Call now does instead.
II->replaceAllUsesWith(CI);
delete II;
Changed = true;
if (BI->isUnconditional()) {
BasicBlock::iterator BBI = BB->getFirstNonPHI();
- BasicBlock *Succ = BI->getSuccessor(0);
// Ignore dbg intrinsics.
while (isa<DbgInfoIntrinsic>(BBI))
++BBI;
- if (BBI->isTerminator() && // Terminator is the only non-phi instruction!
- Succ != BB) // Don't hurt infinite loops!
- if (TryToSimplifyUncondBranchFromEmptyBlock(BB, Succ))
+ if (BBI->isTerminator()) // Terminator is the only non-phi instruction!
+ if (TryToSimplifyUncondBranchFromEmptyBlock(BB))
return true;
} else { // Conditional branch
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