C++ BranchInst::getParent方法代码示例

void AMDGPUAnnotateUniformValues::visitBranchInst(BranchInst &I) {
  if (I.isUnconditional())
    return;

  Value *Cond = I.getCondition();
  if (!DA->isUniform(Cond))
    return;

  setUniformMetadata(I.getParent()->getTerminator());
}

static bool foldReturnAndProcessPred(BasicBlock *BB, ReturnInst *Ret,
                                     BasicBlock *&OldEntry,
                                     bool &TailCallsAreMarkedTail,
                                     SmallVectorImpl<PHINode *> &ArgumentPHIs,
                                     bool CannotTailCallElimCallsMarkedTail,
                                     const TargetTransformInfo *TTI) {
  bool Change = false;

  // If the return block contains nothing but the return and PHI's,
  // there might be an opportunity to duplicate the return in its
  // predecessors and perform TRC there. Look for predecessors that end
  // in unconditional branch and recursive call(s).
  SmallVector<BranchInst*, 8> UncondBranchPreds;
  for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
    BasicBlock *Pred = *PI;
    TerminatorInst *PTI = Pred->getTerminator();
    if (BranchInst *BI = dyn_cast<BranchInst>(PTI))
      if (BI->isUnconditional())
        UncondBranchPreds.push_back(BI);
  }

  while (!UncondBranchPreds.empty()) {
    BranchInst *BI = UncondBranchPreds.pop_back_val();
    BasicBlock *Pred = BI->getParent();
    if (CallInst *CI = findTRECandidate(BI, CannotTailCallElimCallsMarkedTail, TTI)){
      DEBUG(dbgs() << "FOLDING: " << *BB
            << "INTO UNCOND BRANCH PRED: " << *Pred);
      ReturnInst *RI = FoldReturnIntoUncondBranch(Ret, BB, Pred);

      // Cleanup: if all predecessors of BB have been eliminated by
      // FoldReturnIntoUncondBranch, delete it.  It is important to empty it,
      // because the ret instruction in there is still using a value which
      // eliminateRecursiveTailCall will attempt to remove.
      if (!BB->hasAddressTaken() && pred_begin(BB) == pred_end(BB))
        BB->eraseFromParent();

      eliminateRecursiveTailCall(CI, RI, OldEntry, TailCallsAreMarkedTail,
                                 ArgumentPHIs,
                                 CannotTailCallElimCallsMarkedTail);
      ++NumRetDuped;
      Change = true;
    }
  }

  return Change;
}

/// \brief Insert the missing branch conditions
void StructurizeCFG::insertConditions(bool Loops) {
  BranchVector &Conds = Loops ? LoopConds : Conditions;
  Value *Default = Loops ? BoolTrue : BoolFalse;
  SSAUpdater PhiInserter;

  for (BranchVector::iterator I = Conds.begin(),
       E = Conds.end(); I != E; ++I) {

    BranchInst *Term = *I;
    assert(Term->isConditional());

    BasicBlock *Parent = Term->getParent();
    BasicBlock *SuccTrue = Term->getSuccessor(0);
    BasicBlock *SuccFalse = Term->getSuccessor(1);

    PhiInserter.Initialize(Boolean, "");
    PhiInserter.AddAvailableValue(&Func->getEntryBlock(), Default);
    PhiInserter.AddAvailableValue(Loops ? SuccFalse : Parent, Default);

    BBPredicates &Preds = Loops ? LoopPreds[SuccFalse] : Predicates[SuccTrue];

    NearestCommonDominator Dominator(DT);
    Dominator.addBlock(Parent, false);

    Value *ParentValue = 0;
    for (BBPredicates::iterator PI = Preds.begin(), PE = Preds.end();
         PI != PE; ++PI) {

      if (PI->first == Parent) {
        ParentValue = PI->second;
        break;
      }
      PhiInserter.AddAvailableValue(PI->first, PI->second);
      Dominator.addBlock(PI->first);
    }

    if (ParentValue) {
      Term->setCondition(ParentValue);
    } else {
      if (!Dominator.wasResultExplicitMentioned())
        PhiInserter.AddAvailableValue(Dominator.getResult(), Default);

      Term->setCondition(PhiInserter.GetValueInMiddleOfBlock(Parent));
    }
  }
}

bool TailCallElim::FoldReturnAndProcessPred(BasicBlock *BB,
                                       ReturnInst *Ret, BasicBlock *&OldEntry,
                                       bool &TailCallsAreMarkedTail,
                                       SmallVectorImpl<PHINode *> &ArgumentPHIs,
                                       bool CannotTailCallElimCallsMarkedTail) {
  bool Change = false;

  // If the return block contains nothing but the return and PHI's,
  // there might be an opportunity to duplicate the return in its
  // predecessors and perform TRC there. Look for predecessors that end
  // in unconditional branch and recursive call(s).
  SmallVector<BranchInst*, 8> UncondBranchPreds;
  for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
    BasicBlock *Pred = *PI;
    TerminatorInst *PTI = Pred->getTerminator();
    if (BranchInst *BI = dyn_cast<BranchInst>(PTI))
      if (BI->isUnconditional())
        UncondBranchPreds.push_back(BI);
  }

  while (!UncondBranchPreds.empty()) {
    BranchInst *BI = UncondBranchPreds.pop_back_val();
    BasicBlock *Pred = BI->getParent();
    if (CallInst *CI = FindTRECandidate(BI, CannotTailCallElimCallsMarkedTail)){
      DEBUG(dbgs() << "FOLDING: " << *BB
            << "INTO UNCOND BRANCH PRED: " << *Pred);
      EliminateRecursiveTailCall(CI, FoldReturnIntoUncondBranch(Ret, BB, Pred),
                                 OldEntry, TailCallsAreMarkedTail, ArgumentPHIs,
                                 CannotTailCallElimCallsMarkedTail);
      ++NumRetDuped;
      Change = true;
    }
  }

  return Change;
}

/// shouldEliminateUnconditionalBranch - Return true if this branch looks
/// attractive to eliminate.  We eliminate the branch if the destination basic
/// block has <= 5 instructions in it, not counting PHI nodes.  In practice,
/// since one of these is a terminator instruction, this means that we will add
/// up to 4 instructions to the new block.
///
/// We don't count PHI nodes in the count since they will be removed when the
/// contents of the block are copied over.
///
bool TailDup::shouldEliminateUnconditionalBranch(TerminatorInst *TI,
                                                 unsigned Threshold) {
  BranchInst *BI = dyn_cast<BranchInst>(TI);
  if (!BI || !BI->isUnconditional()) return false;  // Not an uncond branch!

  BasicBlock *Dest = BI->getSuccessor(0);
  if (Dest == BI->getParent()) return false;        // Do not loop infinitely!

  // Do not inline a block if we will just get another branch to the same block!
  TerminatorInst *DTI = Dest->getTerminator();
  if (BranchInst *DBI = dyn_cast<BranchInst>(DTI))
    if (DBI->isUnconditional() && DBI->getSuccessor(0) == Dest)
      return false;                                 // Do not loop infinitely!

  // FIXME: DemoteRegToStack cannot yet demote invoke instructions to the stack,
  // because doing so would require breaking critical edges.  This should be
  // fixed eventually.
  if (!DTI->use_empty())
    return false;

  // Do not bother with blocks with only a single predecessor: simplify
  // CFG will fold these two blocks together!
  pred_iterator PI = pred_begin(Dest), PE = pred_end(Dest);
  ++PI;
  if (PI == PE) return false;  // Exactly one predecessor!

  BasicBlock::iterator I = Dest->getFirstNonPHI();

  for (unsigned Size = 0; I != Dest->end(); ++I) {
    if (Size == Threshold) return false;  // The block is too large.
    
    // Don't tail duplicate call instructions.  They are very large compared to
    // other instructions.
    if (isa<CallInst>(I) || isa<InvokeInst>(I)) return false;

    // Also alloca and malloc.
    if (isa<AllocaInst>(I)) return false;

    // Some vector instructions can expand into a number of instructions.
    if (isa<ShuffleVectorInst>(I) || isa<ExtractElementInst>(I) ||
        isa<InsertElementInst>(I)) return false;
    
    // Only count instructions that are not debugger intrinsics.
    if (!isa<DbgInfoIntrinsic>(I)) ++Size;
  }

  // Do not tail duplicate a block that has thousands of successors into a block
  // with a single successor if the block has many other predecessors.  This can
  // cause an N^2 explosion in CFG edges (and PHI node entries), as seen in
  // cases that have a large number of indirect gotos.
  unsigned NumSuccs = DTI->getNumSuccessors();
  if (NumSuccs > 8) {
    unsigned TooMany = 128;
    if (NumSuccs >= TooMany) return false;
    TooMany = TooMany/NumSuccs;
    for (; PI != PE; ++PI)
      if (TooMany-- == 0) return false;
  }
  
  // If this unconditional branch is a fall-through, be careful about
  // tail duplicating it.  In particular, we don't want to taildup it if the
  // original block will still be there after taildup is completed: doing so
  // would eliminate the fall-through, requiring unconditional branches.
  Function::iterator DestI = Dest;
  if (&*--DestI == BI->getParent()) {
    // The uncond branch is a fall-through.  Tail duplication of the block is
    // will eliminate the fall-through-ness and end up cloning the terminator
    // at the end of the Dest block.  Since the original Dest block will
    // continue to exist, this means that one or the other will not be able to
    // fall through.  One typical example that this helps with is code like:
    // if (a)
    //   foo();
    // if (b)
    //   foo();
    // Cloning the 'if b' block into the end of the first foo block is messy.
    
    // The messy case is when the fall-through block falls through to other
    // blocks.  This is what we would be preventing if we cloned the block.
    DestI = Dest;
    if (++DestI != Dest->getParent()->end()) {
      BasicBlock *DestSucc = DestI;
      // If any of Dest's successors are fall-throughs, don't do this xform.
      for (succ_iterator SI = succ_begin(Dest), SE = succ_end(Dest);
           SI != SE; ++SI)
        if (*SI == DestSucc)
          return false;
    }
  }

  // Finally, check that we haven't redirected to this target block earlier;
  // there are cases where we loop forever if we don't check this (PR 2323).
//.........这里部分代码省略.........

/// HandleFloatingPointIV - If the loop has floating induction variable
/// then insert corresponding integer induction variable if possible.
/// For example,
/// for(double i = 0; i < 10000; ++i)
///   bar(i)
/// is converted into
/// for(int i = 0; i < 10000; ++i)
///   bar((double)i);
///
void IndVarSimplify::HandleFloatingPointIV(Loop *L, PHINode *PN) {
  unsigned IncomingEdge = L->contains(PN->getIncomingBlock(0));
  unsigned BackEdge     = IncomingEdge^1;

  // Check incoming value.
  ConstantFP *InitValueVal =
    dyn_cast<ConstantFP>(PN->getIncomingValue(IncomingEdge));

  int64_t InitValue;
  if (!InitValueVal || !ConvertToSInt(InitValueVal->getValueAPF(), InitValue))
    return;

  // Check IV increment. Reject this PN if increment operation is not
  // an add or increment value can not be represented by an integer.
  BinaryOperator *Incr =
    dyn_cast<BinaryOperator>(PN->getIncomingValue(BackEdge));
  if (Incr == 0 || Incr->getOpcode() != Instruction::FAdd) return;
  
  // If this is not an add of the PHI with a constantfp, or if the constant fp
  // is not an integer, bail out.
  ConstantFP *IncValueVal = dyn_cast<ConstantFP>(Incr->getOperand(1));
  int64_t IncValue;
  if (IncValueVal == 0 || Incr->getOperand(0) != PN ||
      !ConvertToSInt(IncValueVal->getValueAPF(), IncValue))
    return;

  // Check Incr uses. One user is PN and the other user is an exit condition
  // used by the conditional terminator.
  Value::use_iterator IncrUse = Incr->use_begin();
  Instruction *U1 = cast<Instruction>(IncrUse++);
  if (IncrUse == Incr->use_end()) return;
  Instruction *U2 = cast<Instruction>(IncrUse++);
  if (IncrUse != Incr->use_end()) return;

  // Find exit condition, which is an fcmp.  If it doesn't exist, or if it isn't
  // only used by a branch, we can't transform it.
  FCmpInst *Compare = dyn_cast<FCmpInst>(U1);
  if (!Compare)
    Compare = dyn_cast<FCmpInst>(U2);
  if (Compare == 0 || !Compare->hasOneUse() ||
      !isa<BranchInst>(Compare->use_back()))
    return;
  
  BranchInst *TheBr = cast<BranchInst>(Compare->use_back());

  // We need to verify that the branch actually controls the iteration count
  // of the loop.  If not, the new IV can overflow and no one will notice.
  // The branch block must be in the loop and one of the successors must be out
  // of the loop.
  assert(TheBr->isConditional() && "Can't use fcmp if not conditional");
  if (!L->contains(TheBr->getParent()) ||
      (L->contains(TheBr->getSuccessor(0)) &&
       L->contains(TheBr->getSuccessor(1))))
    return;
  
  
  // If it isn't a comparison with an integer-as-fp (the exit value), we can't
  // transform it.
  ConstantFP *ExitValueVal = dyn_cast<ConstantFP>(Compare->getOperand(1));
  int64_t ExitValue;
  if (ExitValueVal == 0 ||
      !ConvertToSInt(ExitValueVal->getValueAPF(), ExitValue))
    return;
  
  // Find new predicate for integer comparison.
  CmpInst::Predicate NewPred = CmpInst::BAD_ICMP_PREDICATE;
  switch (Compare->getPredicate()) {
  default: return;  // Unknown comparison.
  case CmpInst::FCMP_OEQ:
  case CmpInst::FCMP_UEQ: NewPred = CmpInst::ICMP_EQ; break;
  case CmpInst::FCMP_ONE:
  case CmpInst::FCMP_UNE: NewPred = CmpInst::ICMP_NE; break;
  case CmpInst::FCMP_OGT:
  case CmpInst::FCMP_UGT: NewPred = CmpInst::ICMP_SGT; break;
  case CmpInst::FCMP_OGE:
  case CmpInst::FCMP_UGE: NewPred = CmpInst::ICMP_SGE; break;
  case CmpInst::FCMP_OLT:
  case CmpInst::FCMP_ULT: NewPred = CmpInst::ICMP_SLT; break;
  case CmpInst::FCMP_OLE:
  case CmpInst::FCMP_ULE: NewPred = CmpInst::ICMP_SLE; break;
  }
  
  // We convert the floating point induction variable to a signed i32 value if
  // we can.  This is only safe if the comparison will not overflow in a way
  // that won't be trapped by the integer equivalent operations.  Check for this
  // now.
  // TODO: We could use i64 if it is native and the range requires it.
  
  // The start/stride/exit values must all fit in signed i32.
  if (!isInt<32>(InitValue) || !isInt<32>(IncValue) || !isInt<32>(ExitValue))
    return;
//.........这里部分代码省略.........

//.........这里部分代码省略.........
				}
			}
		}
	}

	//build information for predecessor of blocks in post dominator tree
	for (Function::iterator bi = func->begin(); bi != func->end(); bi++) {
		BasicBlock *BB = bi;
		DomTreeNode *dn = pdt.getNode(BB);

		for (DomTreeNode::iterator di = dn->begin(); di != dn->end(); di++) {
			BasicBlock *CB = (*di)->getBlock();
			pre[CB] = BB;
		}
	}
//
//	//add dependency within a basicblock
//	for (Loop::block_iterator bi = L->getBlocks().begin(); bi != L->getBlocks().end(); bi++) {
//		BasicBlock *BB = *bi;
//		Instruction *pre = NULL;
//		for (BasicBlock::iterator ui = BB->begin(); ui != BB->end(); ui++) {
//			Instruction *inst = &(*ui);
//			if (pre != NULL) {
//				addEdge(pre, inst, CONTROL);
//			}
//			pre = inst;
//		}
//	}

//	//the special kind of dependence need loop peeling ? I don't know whether this is needed
//	for (Loop::block_iterator bi = L->getBlocks().begin(); bi != L->getBlocks().end(); bi++) {
//		BasicBlock *BB = *bi;
//		for (succ_iterator PI = succ_begin(BB); PI != succ_end(BB); ++PI) {
//			BasicBlock *succ = *PI;
//
//			checkControlDependence(BB, succ, pdt);
//		}
//	}


	/*
	 * alien code part 2
	 */
	// add normal control dependencies
	// loop through each instruction
	for (Loop::block_iterator bbIter = L->block_begin(); bbIter
			!= L->block_end(); ++bbIter) {
		BasicBlock *bb = *bbIter;
		// check the successors of this basic block
		if (BranchInst *branchInst = dyn_cast<BranchInst>(bb->getTerminator())) {
			if (branchInst->getNumSuccessors() > 1) {
				BasicBlock * succ = branchInst->getSuccessor(0);
				// if the successor is nested shallower than the current basic block, continue
				if (LI->getLoopDepth(bb) < LI->getLoopDepth(succ)) {
					continue;
				}
				// otherwise, add all instructions to graph as control dependence
				while (succ != NULL && succ != bb && LI->getLoopDepth(succ)
						>= LI->getLoopDepth(bb)) {
					Instruction *terminator = bb->getTerminator();
					for (BasicBlock::iterator succInstIter = succ->begin(); &(*succInstIter)
							!= succ->getTerminator(); ++succInstIter) {
						addEdge(terminator, &(*succInstIter), CONTROL);
					}
					if (BranchInst *succBrInst = dyn_cast<BranchInst>(succ->getTerminator())) {
						if (succBrInst->getNumSuccessors() > 1) {
							addEdge(terminator, succ->getTerminator(),
									CONTROL);
						}
					}
					if (BranchInst *br = dyn_cast<BranchInst>(succ->getTerminator())) {
						if (br->getNumSuccessors() == 1) {
							succ = br->getSuccessor(0);
						} else {
							succ = NULL;
						}
					} else {
						succ = NULL;
					}
				}
			}
		}
	}


	/*
	 * alien code part 3
	 */
    for (std::set<BranchInst*>::iterator exitIter = backedgeParents.begin(); exitIter != backedgeParents.end(); ++exitIter) {
        BranchInst *exitBranch = *exitIter;
        if (exitBranch->isConditional()) {
            BasicBlock *header = LI->getLoopFor(exitBranch->getParent())->getHeader();
            for (BasicBlock::iterator ctrlIter = header->begin(); ctrlIter != header->end(); ++ctrlIter) {
                addEdge(exitBranch, &(*ctrlIter), CONTROL);
            }
        }
    }

	//end control dependence
}

// addEdgesFor
// Creates a node for I and inserts edges from the created node to the
// appropriate node of other values.
void IneqGraph::addEdgesFor(Instruction *I) {
  if (I->getType()->isPointerTy())
    return;

  Range RI = RA->getRange(I);
  if (!RI.getLower().isMinSignedValue())
    addMayEdge(AlfaConst, I, -RI.getLower().getSExtValue());
  if (!RI.getUpper().isMaxSignedValue())
    addMayEdge(I, AlfaConst, RI.getUpper().getSExtValue());

  // TODO: Handle multiplication, remainder and division instructions.
  switch (I->getOpcode()) {
    case Instruction::SExt:
    case Instruction::ZExt:
    case Instruction::Trunc:
    case Instruction::BitCast:
      addMayEdge(I, I->getOperand(0), 0);
      addMayEdge(I->getOperand(0), I, 0);
      break;
    case Instruction::Add:
      // a = b + c
      // ==> a <= b + sup(c)
      // ==> a <= c + sup(b)
      // ==> b <= a - inf(c)
      // ==> c <= a - inf(b)
      {
        Value *A = I->getOperand(0);
        Value *B = I->getOperand(1);
        Range AR = RA->getRange(A);
        Range BR = RA->getRange(B);
        if (!isa<ConstantInt>(B) && !AR.getUpper().isMaxSignedValue())
          addMayEdge(I, B, AR.getUpper());
        if (!isa<ConstantInt>(A) && !BR.getUpper().isMaxSignedValue())
          addMayEdge(I, A, BR.getUpper());
        if (!isa<ConstantInt>(A) && !BR.getLower().isMinSignedValue())
          addMayEdge(A, I, -BR.getUpper());
        if (!isa<ConstantInt>(B) && !AR.getLower().isMinSignedValue())
          addMayEdge(B, I, -AR.getUpper());
        break;
      }
    case Instruction::Sub:
      // a = b - c
      // ==> a <= b - inf(c)
      {
        Value *A = I->getOperand(0);
        Value *B = I->getOperand(1);
        Range AR = RA->getRange(A);
        Range BR = RA->getRange(B);
        if (!isa<ConstantInt>(A) && !BR.getLower().isMinSignedValue())
          addMayEdge(I, A, -BR.getLower());
        break;
      }
    case Instruction::Br:
      // if (a > b) {
      //   a1 = sigma(a)
      //   b1 = sigma(b)
      {      
        BranchInst *BI = cast<BranchInst>(I);
        ICmpInst *Cmp = dyn_cast<ICmpInst>(I->getOperand(0));
        if (!Cmp)
          break;
        Value *L = Cmp->getOperand(0);
        DEBUG(dbgs() << "IneqGraph: L: " << *L << "\n");
        Value *R = Cmp->getOperand(1);
        DEBUG(dbgs() << "IneqGraph: R: " << *R << "\n");
        Value *LSigma = VS->findSigma(L, BI->getSuccessor(0), BI->getParent());
        DEBUG(dbgs() << "IneqGraph: LSigma: " << *LSigma << "\n");
        Value *RSigma = VS->findSigma(R, BI->getSuccessor(0), BI->getParent());
        DEBUG(dbgs() << "IneqGraph: RSigma: " << *RSigma << "\n");
        Value *LSExtSigma = VS->findSExtSigma(L, BI->getSuccessor(0), BI->getParent());
        DEBUG(dbgs() << "IneqGraph: LSExtSigma: " << *LSExtSigma << "\n");
        Value *RSExtSigma = VS->findSExtSigma(R, BI->getSuccessor(0), BI->getParent());
        DEBUG(dbgs() << "IneqGraph: RSExtSigma: " << *RSExtSigma << "\n");
        switch (Cmp->getPredicate()) {
          case ICmpInst::ICMP_SLT:
            DEBUG(dbgs() << "IneqGraph: SLT:\n");
            if (!isa<ConstantInt>(R) && LSigma) {
              if (RSigma)
                addMayEdge(LSigma, RSigma, -1);
              if (RSExtSigma)
                addMayEdge(LSigma, RSExtSigma, -1);
            }
            if (!isa<ConstantInt>(R) && LSExtSigma && LSExtSigma != LSigma) {
              if (RSigma)
                addMayEdge(LSExtSigma, RSigma, -1);
              if (RSExtSigma)
                addMayEdge(LSExtSigma, RSExtSigma, -1);
            }
            break;
          case ICmpInst::ICMP_SLE:
            DEBUG(dbgs() << "IneqGraph: SLE:\n");
            if (!isa<ConstantInt>(R) && LSigma && RSigma)
              addMayEdge(LSigma, RSigma, 0);
            if (!isa<ConstantInt>(R) && (LSExtSigma != LSigma || RSExtSigma != RSigma))
              addMayEdge(LSExtSigma, RSExtSigma, 0);
            break;
          default:
//.........这里部分代码省略.........