C++ BinaryOperator::getParent方法代码示例

void IndVarSimplify::EliminateIVRemainders() {
  // Look for SRem and URem users.
  for (IVUsers::iterator I = IU->begin(), E = IU->end(); I != E; ++I) {
    IVStrideUse &UI = *I;
    BinaryOperator *Rem = dyn_cast<BinaryOperator>(UI.getUser());
    if (!Rem) continue;

    bool isSigned = Rem->getOpcode() == Instruction::SRem;
    if (!isSigned && Rem->getOpcode() != Instruction::URem)
      continue;

    // We're only interested in the case where we know something about
    // the numerator.
    if (UI.getOperandValToReplace() != Rem->getOperand(0))
      continue;

    // Get the SCEVs for the ICmp operands.
    const SCEV *S = SE->getSCEV(Rem->getOperand(0));
    const SCEV *X = SE->getSCEV(Rem->getOperand(1));

    // Simplify unnecessary loops away.
    const Loop *ICmpLoop = LI->getLoopFor(Rem->getParent());
    S = SE->getSCEVAtScope(S, ICmpLoop);
    X = SE->getSCEVAtScope(X, ICmpLoop);

    // i % n  -->  i  if i is in [0,n).
    if ((!isSigned || SE->isKnownNonNegative(S)) &&
        SE->isKnownPredicate(isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
                             S, X))
      Rem->replaceAllUsesWith(Rem->getOperand(0));
    else {
      // (i+1) % n  -->  (i+1)==n?0:(i+1)  if i is in [0,n).
      const SCEV *LessOne =
        SE->getMinusSCEV(S, SE->getConstant(S->getType(), 1));
      if ((!isSigned || SE->isKnownNonNegative(LessOne)) &&
          SE->isKnownPredicate(isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
                               LessOne, X)) {
        ICmpInst *ICmp = new ICmpInst(Rem, ICmpInst::ICMP_EQ,
                                      Rem->getOperand(0), Rem->getOperand(1),
                                      "tmp");
        SelectInst *Sel =
          SelectInst::Create(ICmp,
                             ConstantInt::get(Rem->getType(), 0),
                             Rem->getOperand(0), "tmp", Rem);
        Rem->replaceAllUsesWith(Sel);
      } else
        continue;
    }

    // Inform IVUsers about the new users.
    if (Instruction *I = dyn_cast<Instruction>(Rem->getOperand(0)))
      IU->AddUsersIfInteresting(I);

    DEBUG(dbgs() << "INDVARS: Simplified rem: " << *Rem << '\n');
    DeadInsts.push_back(Rem);
  }
}

// Insert an intrinsic for fast fdiv for safe math situations where we can
// reduce precision. Leave fdiv for situations where the generic node is
// expected to be optimized.
bool AMDGPUCodeGenPrepare::visitFDiv(BinaryOperator &FDiv) {
  Type *Ty = FDiv.getType();

  // TODO: Handle half
  if (!Ty->getScalarType()->isFloatTy())
    return false;

  MDNode *FPMath = FDiv.getMetadata(LLVMContext::MD_fpmath);
  if (!FPMath)
    return false;

  const FPMathOperator *FPOp = cast<const FPMathOperator>(&FDiv);
  float ULP = FPOp->getFPAccuracy();
  if (ULP < 2.5f)
    return false;

  FastMathFlags FMF = FPOp->getFastMathFlags();
  bool UnsafeDiv = HasUnsafeFPMath || FMF.unsafeAlgebra() ||
                                      FMF.allowReciprocal();
  if (ST->hasFP32Denormals() && !UnsafeDiv)
    return false;

  IRBuilder<> Builder(FDiv.getParent(), std::next(FDiv.getIterator()), FPMath);
  Builder.setFastMathFlags(FMF);
  Builder.SetCurrentDebugLocation(FDiv.getDebugLoc());

  const AMDGPUIntrinsicInfo *II = TM->getIntrinsicInfo();
  Function *Decl
    = II->getDeclaration(Mod, AMDGPUIntrinsic::amdgcn_fdiv_fast, {});

  Value *Num = FDiv.getOperand(0);
  Value *Den = FDiv.getOperand(1);

  Value *NewFDiv = nullptr;

  if (VectorType *VT = dyn_cast<VectorType>(Ty)) {
    NewFDiv = UndefValue::get(VT);

    // FIXME: Doesn't do the right thing for cases where the vector is partially
    // constant. This works when the scalarizer pass is run first.
    for (unsigned I = 0, E = VT->getNumElements(); I != E; ++I) {
      Value *NumEltI = Builder.CreateExtractElement(Num, I);
      Value *DenEltI = Builder.CreateExtractElement(Den, I);
      Value *NewElt;

      if (shouldKeepFDivF32(NumEltI, UnsafeDiv)) {
        NewElt = Builder.CreateFDiv(NumEltI, DenEltI);
      } else {
        NewElt = Builder.CreateCall(Decl, { NumEltI, DenEltI });
      }

      NewFDiv = Builder.CreateInsertElement(NewFDiv, NewElt, I);
    }
  } else {
    if (!shouldKeepFDivF32(Num, UnsafeDiv))
      NewFDiv = Builder.CreateCall(Decl, { Num, Den });
  }

  if (NewFDiv) {
    FDiv.replaceAllUsesWith(NewFDiv);
    NewFDiv->takeName(&FDiv);
    FDiv.eraseFromParent();
  }

  return true;
}

// Peephole optimize the following instructions:
// %t1 = cast ? to x *
// %t2 = add x * %SP, %t1              ;; Constant must be 2nd operand
//
// Into: %t3 = getelementptr {<...>} * %SP, <element indices>
//       %t2 = cast <eltype> * %t3 to {<...>}*
//
static bool HandleCastToPointer(BasicBlock::iterator BI,
                                const PointerType *DestPTy,
                                const TargetData &TD) {
  CastInst &CI = cast<CastInst>(*BI);
  if (CI.use_empty()) return false;

  // Scan all of the uses, looking for any uses that are not add or sub
  // instructions.  If we have non-adds, do not make this transformation.
  //
  bool HasSubUse = false;  // Keep track of any subtracts...
  for (Value::use_iterator I = CI.use_begin(), E = CI.use_end();
       I != E; ++I)
    if (BinaryOperator *BO = dyn_cast<BinaryOperator>(*I)) {
      if ((BO->getOpcode() != Instruction::Add &&
           BO->getOpcode() != Instruction::Sub) ||
          // Avoid add sbyte* %X, %X cases...
          BO->getOperand(0) == BO->getOperand(1))
        return false;
      else
        HasSubUse |= BO->getOpcode() == Instruction::Sub;
    } else {
      return false;
    }

  std::vector<Value*> Indices;
  Value *Src = CI.getOperand(0);
  const Type *Result = ConvertibleToGEP(DestPTy, Src, Indices, TD, &BI);
  if (Result == 0) return false;  // Not convertible...

  // Cannot handle subtracts if there is more than one index required...
  if (HasSubUse && Indices.size() != 1) return false;

  PRINT_PEEPHOLE2("cast-add-to-gep:in", *Src, CI);

  // If we have a getelementptr capability... transform all of the 
  // add instruction uses into getelementptr's.
  while (!CI.use_empty()) {
    BinaryOperator *I = cast<BinaryOperator>(*CI.use_begin());
    assert((I->getOpcode() == Instruction::Add ||
            I->getOpcode() == Instruction::Sub) && 
           "Use is not a valid add instruction!");
    
    // Get the value added to the cast result pointer...
    Value *OtherPtr = I->getOperand((I->getOperand(0) == &CI) ? 1 : 0);

    Instruction *GEP = new GetElementPtrInst(OtherPtr, Indices, I->getName());
    PRINT_PEEPHOLE1("cast-add-to-gep:i", *I);

    // If the instruction is actually a subtract, we are guaranteed to only have
    // one index (from code above), so we just need to negate the pointer index
    // long value.
    if (I->getOpcode() == Instruction::Sub) {
      Instruction *Neg = BinaryOperator::createNeg(GEP->getOperand(1), 
                                       GEP->getOperand(1)->getName()+".neg", I);
      GEP->setOperand(1, Neg);
    }

    if (GEP->getType() == I->getType()) {
      // Replace the old add instruction with the shiny new GEP inst
      ReplaceInstWithInst(I, GEP);
    } else {
      // If the type produced by the gep instruction differs from the original
      // add instruction type, insert a cast now.
      //

      // Insert the GEP instruction before the old add instruction...
      I->getParent()->getInstList().insert(I, GEP);

      PRINT_PEEPHOLE1("cast-add-to-gep:o", *GEP);
      GEP = new CastInst(GEP, I->getType());

      // Replace the old add instruction with the shiny new GEP inst
      ReplaceInstWithInst(I, GEP);
    }

    PRINT_PEEPHOLE1("cast-add-to-gep:o", *GEP);
  }
  return true;
}

/// SimplifyDivRemOfSelect - Try to fold a divide or remainder of a select
/// instruction.
bool InstCombiner::SimplifyDivRemOfSelect(BinaryOperator &I) {
  SelectInst *SI = cast<SelectInst>(I.getOperand(1));
  
  // div/rem X, (Cond ? 0 : Y) -> div/rem X, Y
  int NonNullOperand = -1;
  if (Constant *ST = dyn_cast<Constant>(SI->getOperand(1)))
    if (ST->isNullValue())
      NonNullOperand = 2;
  // div/rem X, (Cond ? Y : 0) -> div/rem X, Y
  if (Constant *ST = dyn_cast<Constant>(SI->getOperand(2)))
    if (ST->isNullValue())
      NonNullOperand = 1;
  
  if (NonNullOperand == -1)
    return false;
  
  Value *SelectCond = SI->getOperand(0);
  
  // Change the div/rem to use 'Y' instead of the select.
  I.setOperand(1, SI->getOperand(NonNullOperand));
  
  // Okay, we know we replace the operand of the div/rem with 'Y' with no
  // problem.  However, the select, or the condition of the select may have
  // multiple uses.  Based on our knowledge that the operand must be non-zero,
  // propagate the known value for the select into other uses of it, and
  // propagate a known value of the condition into its other users.
  
  // If the select and condition only have a single use, don't bother with this,
  // early exit.
  if (SI->use_empty() && SelectCond->hasOneUse())
    return true;
  
  // Scan the current block backward, looking for other uses of SI.
  BasicBlock::iterator BBI = &I, BBFront = I.getParent()->begin();
  
  while (BBI != BBFront) {
    --BBI;
    // If we found a call to a function, we can't assume it will return, so
    // information from below it cannot be propagated above it.
    if (isa<CallInst>(BBI) && !isa<IntrinsicInst>(BBI))
      break;
    
    // Replace uses of the select or its condition with the known values.
    for (Instruction::op_iterator I = BBI->op_begin(), E = BBI->op_end();
         I != E; ++I) {
      if (*I == SI) {
        *I = SI->getOperand(NonNullOperand);
        Worklist.Add(BBI);
      } else if (*I == SelectCond) {
        *I = NonNullOperand == 1 ? ConstantInt::getTrue(BBI->getContext()) :
                                   ConstantInt::getFalse(BBI->getContext());
        Worklist.Add(BBI);
      }
    }
    
    // If we past the instruction, quit looking for it.
    if (&*BBI == SI)
      SI = 0;
    if (&*BBI == SelectCond)
      SelectCond = 0;
    
    // If we ran out of things to eliminate, break out of the loop.
    if (SelectCond == 0 && SI == 0)
      break;
    
  }
  return true;
}

// NegateValue - Insert instructions before the instruction pointed to by BI,
// that computes the negative version of the value specified.  The negative
// version of the value is returned, and BI is left pointing at the instruction
// that should be processed next by the reassociation pass.
//
static Value *NegateValue(Value *V, Instruction *BI) {
  if (Constant *C = dyn_cast<Constant>(V))
    return ConstantExpr::getNeg(C);
  
  // We are trying to expose opportunity for reassociation.  One of the things
  // that we want to do to achieve this is to push a negation as deep into an
  // expression chain as possible, to expose the add instructions.  In practice,
  // this means that we turn this:
  //   X = -(A+12+C+D)   into    X = -A + -12 + -C + -D = -12 + -A + -C + -D
  // so that later, a: Y = 12+X could get reassociated with the -12 to eliminate
  // the constants.  We assume that instcombine will clean up the mess later if
  // we introduce tons of unnecessary negation instructions.
  //
  if (Instruction *I = dyn_cast<Instruction>(V))
    if (I->getOpcode() == Instruction::Add && I->hasOneUse()) {
      // Push the negates through the add.
      I->setOperand(0, NegateValue(I->getOperand(0), BI));
      I->setOperand(1, NegateValue(I->getOperand(1), BI));

      // We must move the add instruction here, because the neg instructions do
      // not dominate the old add instruction in general.  By moving it, we are
      // assured that the neg instructions we just inserted dominate the 
      // instruction we are about to insert after them.
      //
      I->moveBefore(BI);
      I->setName(I->getName()+".neg");
      return I;
    }
  
  // Okay, we need to materialize a negated version of V with an instruction.
  // Scan the use lists of V to see if we have one already.
  for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI){
    User *U = *UI;
    if (!BinaryOperator::isNeg(U)) continue;

    // We found one!  Now we have to make sure that the definition dominates
    // this use.  We do this by moving it to the entry block (if it is a
    // non-instruction value) or right after the definition.  These negates will
    // be zapped by reassociate later, so we don't need much finesse here.
    BinaryOperator *TheNeg = cast<BinaryOperator>(U);

    // Verify that the negate is in this function, V might be a constant expr.
    if (TheNeg->getParent()->getParent() != BI->getParent()->getParent())
      continue;
    
    BasicBlock::iterator InsertPt;
    if (Instruction *InstInput = dyn_cast<Instruction>(V)) {
      if (InvokeInst *II = dyn_cast<InvokeInst>(InstInput)) {
        InsertPt = II->getNormalDest()->begin();
      } else {
        InsertPt = InstInput;
        ++InsertPt;
      }
      while (isa<PHINode>(InsertPt)) ++InsertPt;
    } else {
      InsertPt = TheNeg->getParent()->getParent()->getEntryBlock().begin();
    }
    TheNeg->moveBefore(InsertPt);
    return TheNeg;
  }

  // Insert a 'neg' instruction that subtracts the value from zero to get the
  // negation.
  return BinaryOperator::CreateNeg(V, V->getName() + ".neg", BI);
}