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C++ BranchInst::swapSuccessors方法代码示例

本文整理汇总了C++中BranchInst::swapSuccessors方法的典型用法代码示例。如果您正苦于以下问题:C++ BranchInst::swapSuccessors方法的具体用法?C++ BranchInst::swapSuccessors怎么用?C++ BranchInst::swapSuccessors使用的例子?那么, 这里精选的方法代码示例或许可以为您提供帮助。您也可以进一步了解该方法所在BranchInst的用法示例。


在下文中一共展示了BranchInst::swapSuccessors方法的3个代码示例,这些例子默认根据受欢迎程度排序。您可以为喜欢或者感觉有用的代码点赞,您的评价将有助于系统推荐出更棒的C++代码示例。

示例1: FlattenParallelAndOr


//.........这里部分代码省略.........
    if (Preds.count(PS) == 0) {
      // Case 2.
      LastCondBlock = Pred;
    } else {
      // Case 1
      BranchInst *BPS = dyn_cast<BranchInst>(PS->getTerminator());
      if (BPS && BPS->isUnconditional()) {
        // Case 1: PS(BB3) should be an unconditional branch.
        LastCondBlock = Pred;
      }
    }
  }

  if (!FirstCondBlock || !LastCondBlock || (FirstCondBlock == LastCondBlock))
    return false;

  TerminatorInst *TBB = LastCondBlock->getTerminator();
  BasicBlock *PS1 = TBB->getSuccessor(0);
  BasicBlock *PS2 = TBB->getSuccessor(1);
  BranchInst *PBI1 = dyn_cast<BranchInst>(PS1->getTerminator());
  BranchInst *PBI2 = dyn_cast<BranchInst>(PS2->getTerminator());

  // If PS1 does not jump into PS2, but PS2 jumps into PS1,
  // attempt branch inversion.
  if (!PBI1 || !PBI1->isUnconditional() ||
      (PS1->getTerminator()->getSuccessor(0) != PS2)) {
    // Check whether PS2 jumps into PS1.
    if (!PBI2 || !PBI2->isUnconditional() ||
        (PS2->getTerminator()->getSuccessor(0) != PS1))
      return false;

    // Do branch inversion.
    BasicBlock *CurrBlock = LastCondBlock;
    bool EverChanged = false;
    while (1) {
      BranchInst *BI = dyn_cast<BranchInst>(CurrBlock->getTerminator());
      CmpInst *CI = dyn_cast<CmpInst>(BI->getCondition());
      CmpInst::Predicate Predicate = CI->getPredicate();
      // Cannonicalize icmp_ne -> icmp_eq, fcmp_one -> fcmp_oeq
      if ((Predicate == CmpInst::ICMP_NE) || (Predicate == CmpInst::FCMP_ONE)) {
        CI->setPredicate(ICmpInst::getInversePredicate(Predicate));
        BI->swapSuccessors();
        EverChanged = true;
      }
      if (CurrBlock == FirstCondBlock)
        break;
      CurrBlock = CurrBlock->getSinglePredecessor();
    }
    return EverChanged;
  }

  // PS1 must have a conditional branch.
  if (!PBI1 || !PBI1->isUnconditional())
    return false;

  // PS2 should not contain PHI node.
  PHI = dyn_cast<PHINode>(PS2->begin());
  if (PHI)
    return false;

  // Do the transformation.
  BasicBlock *CB;
  BranchInst *PBI = dyn_cast<BranchInst>(FirstCondBlock->getTerminator());
  bool Iteration = true;
  BasicBlock *SaveInsertBB = Builder.GetInsertBlock();
  BasicBlock::iterator SaveInsertPt = Builder.GetInsertPoint();
  Value *PC = PBI->getCondition();

  do {
    CB = PBI->getSuccessor(1 - Idx);
    // Delete the conditional branch.
    FirstCondBlock->getInstList().pop_back();
    FirstCondBlock->getInstList()
        .splice(FirstCondBlock->end(), CB->getInstList());
    PBI = cast<BranchInst>(FirstCondBlock->getTerminator());
    Value *CC = PBI->getCondition();
    // Merge conditions.
    Builder.SetInsertPoint(PBI);
    Value *NC;
    if (Idx == 0)
      // Case 2, use parallel or.
      NC = Builder.CreateOr(PC, CC);
    else
      // Case 1, use parallel and.
      NC = Builder.CreateAnd(PC, CC);

    PBI->replaceUsesOfWith(CC, NC);
    PC = NC;
    if (CB == LastCondBlock)
      Iteration = false;
    // Remove internal conditional branches.
    CB->dropAllReferences();
    // make CB unreachable and let downstream to delete the block.
    new UnreachableInst(CB->getContext(), CB);
  } while (Iteration);

  Builder.SetInsertPoint(SaveInsertBB, SaveInsertPt);
  DEBUG(dbgs() << "Use parallel and/or in:\n" << *FirstCondBlock);
  return true;
}
开发者ID:ChiahungTai,项目名称:llvm,代码行数:101,代码来源:FlattenCFG.cpp

示例2: convertToCTRLoop


//.........这里部分代码省略.........

    // We now have a loop-invariant count of loop iterations (which is not the
    // constant zero) for which we know that this loop will not exit via this
    // exisiting block.

    // We need to make sure that this block will run on every loop iteration.
    // For this to be true, we must dominate all blocks with backedges. Such
    // blocks are in-loop predecessors to the header block.
    bool NotAlways = false;
    for (pred_iterator PI = pred_begin(L->getHeader()),
         PIE = pred_end(L->getHeader()); PI != PIE; ++PI) {
      if (!L->contains(*PI))
        continue;

      if (!DT->dominates(*I, *PI)) {
        NotAlways = true;
        break;
      }
    }

    if (NotAlways)
      continue;

    // Make sure this blocks ends with a conditional branch.
    Instruction *TI = (*I)->getTerminator();
    if (!TI)
      continue;

    if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
      if (!BI->isConditional())
        continue;

      CountedExitBranch = BI;
    } else
      continue;

    // Note that this block may not be the loop latch block, even if the loop
    // has a latch block.
    CountedExitBlock = *I;
    ExitCount = EC;
    break;
  }

  if (!CountedExitBlock)
    return MadeChange;

  BasicBlock *Preheader = L->getLoopPreheader();

  // If we don't have a preheader, then insert one. If we already have a
  // preheader, then we can use it (except if the preheader contains a use of
  // the CTR register because some such uses might be reordered by the
  // selection DAG after the mtctr instruction).
  if (!Preheader || mightUseCTR(TT, Preheader))
    Preheader = InsertPreheaderForLoop(L, this);
  if (!Preheader)
    return MadeChange;

  DEBUG(dbgs() << "Preheader for exit count: " << Preheader->getName() << "\n");

  // Insert the count into the preheader and replace the condition used by the
  // selected branch.
  MadeChange = true;

  SCEVExpander SCEVE(*SE, "loopcnt");
  LLVMContext &C = SE->getContext();
  Type *CountType = TT.isArch64Bit() ? Type::getInt64Ty(C) :
                                       Type::getInt32Ty(C);
  if (!ExitCount->getType()->isPointerTy() &&
      ExitCount->getType() != CountType)
    ExitCount = SE->getZeroExtendExpr(ExitCount, CountType);
  ExitCount = SE->getAddExpr(ExitCount,
                             SE->getConstant(CountType, 1)); 
  Value *ECValue = SCEVE.expandCodeFor(ExitCount, CountType,
                                       Preheader->getTerminator());

  IRBuilder<> CountBuilder(Preheader->getTerminator());
  Module *M = Preheader->getParent()->getParent();
  Value *MTCTRFunc = Intrinsic::getDeclaration(M, Intrinsic::ppc_mtctr,
                                               CountType);
  CountBuilder.CreateCall(MTCTRFunc, ECValue);

  IRBuilder<> CondBuilder(CountedExitBranch);
  Value *DecFunc =
    Intrinsic::getDeclaration(M, Intrinsic::ppc_is_decremented_ctr_nonzero);
  Value *NewCond = CondBuilder.CreateCall(DecFunc);
  Value *OldCond = CountedExitBranch->getCondition();
  CountedExitBranch->setCondition(NewCond);

  // The false branch must exit the loop.
  if (!L->contains(CountedExitBranch->getSuccessor(0)))
    CountedExitBranch->swapSuccessors();

  // The old condition may be dead now, and may have even created a dead PHI
  // (the original induction variable).
  RecursivelyDeleteTriviallyDeadInstructions(OldCond);
  DeleteDeadPHIs(CountedExitBlock);

  ++NumCTRLoops;
  return MadeChange;
}
开发者ID:eaglexmw,项目名称:llvm,代码行数:101,代码来源:PPCCTRLoops.cpp

示例3: convertToCTRLoop


//.........这里部分代码省略.........
    // constant zero) for which we know that this loop will not exit via this
    // existing block.

    // We need to make sure that this block will run on every loop iteration.
    // For this to be true, we must dominate all blocks with backedges. Such
    // blocks are in-loop predecessors to the header block.
    bool NotAlways = false;
    for (pred_iterator PI = pred_begin(L->getHeader()),
         PIE = pred_end(L->getHeader()); PI != PIE; ++PI) {
      if (!L->contains(*PI))
        continue;

      if (!DT->dominates(*I, *PI)) {
        NotAlways = true;
        break;
      }
    }

    if (NotAlways)
      continue;

    // Make sure this blocks ends with a conditional branch.
    Instruction *TI = (*I)->getTerminator();
    if (!TI)
      continue;

    if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
      if (!BI->isConditional())
        continue;

      CountedExitBranch = BI;
    } else
      continue;

    // Note that this block may not be the loop latch block, even if the loop
    // has a latch block.
    CountedExitBlock = *I;
    ExitCount = EC;
    break;
  }

  if (!CountedExitBlock)
    return MadeChange;

  BasicBlock *Preheader = L->getLoopPreheader();

  // If we don't have a preheader, then insert one. If we already have a
  // preheader, then we can use it (except if the preheader contains a use of
  // the CTR register because some such uses might be reordered by the
  // selection DAG after the mtctr instruction).
  if (!Preheader || mightUseCTR(Preheader))
    Preheader = InsertPreheaderForLoop(L, DT, LI, PreserveLCSSA);
  if (!Preheader)
    return MadeChange;

  LLVM_DEBUG(dbgs() << "Preheader for exit count: " << Preheader->getName()
                    << "\n");

  // Insert the count into the preheader and replace the condition used by the
  // selected branch.
  MadeChange = true;

  SCEVExpander SCEVE(*SE, *DL, "loopcnt");
  LLVMContext &C = SE->getContext();
  Type *CountType = TM->isPPC64() ? Type::getInt64Ty(C) : Type::getInt32Ty(C);
  if (!ExitCount->getType()->isPointerTy() &&
      ExitCount->getType() != CountType)
    ExitCount = SE->getZeroExtendExpr(ExitCount, CountType);
  ExitCount = SE->getAddExpr(ExitCount, SE->getOne(CountType));
  Value *ECValue =
      SCEVE.expandCodeFor(ExitCount, CountType, Preheader->getTerminator());

  IRBuilder<> CountBuilder(Preheader->getTerminator());
  Module *M = Preheader->getParent()->getParent();
  Function *MTCTRFunc =
      Intrinsic::getDeclaration(M, Intrinsic::ppc_mtctr, CountType);
  CountBuilder.CreateCall(MTCTRFunc, ECValue);

  IRBuilder<> CondBuilder(CountedExitBranch);
  Function *DecFunc =
      Intrinsic::getDeclaration(M, Intrinsic::ppc_is_decremented_ctr_nonzero);
  Value *NewCond = CondBuilder.CreateCall(DecFunc, {});
  Value *OldCond = CountedExitBranch->getCondition();
  CountedExitBranch->setCondition(NewCond);

  // The false branch must exit the loop.
  if (!L->contains(CountedExitBranch->getSuccessor(0)))
    CountedExitBranch->swapSuccessors();

  // The old condition may be dead now, and may have even created a dead PHI
  // (the original induction variable).
  RecursivelyDeleteTriviallyDeadInstructions(OldCond);
  // Run through the basic blocks of the loop and see if any of them have dead
  // PHIs that can be removed.
  for (auto I : L->blocks())
    DeleteDeadPHIs(I);

  ++NumCTRLoops;
  return MadeChange;
}
开发者ID:jamboree,项目名称:llvm,代码行数:101,代码来源:PPCCTRLoops.cpp


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