C++ ConstantInt::getBitWidth方法代码示例

void StraightLineStrengthReduce::factorArrayIndex(Value *ArrayIdx,
                                                  const SCEV *Base,
                                                  uint64_t ElementSize,
                                                  GetElementPtrInst *GEP) {
  // At least, ArrayIdx = ArrayIdx *nsw 1.
  allocateCandidatesAndFindBasisForGEP(
      Base, ConstantInt::get(cast<IntegerType>(ArrayIdx->getType()), 1),
      ArrayIdx, ElementSize, GEP);
  Value *LHS = nullptr;
  ConstantInt *RHS = nullptr;
  // One alternative is matching the SCEV of ArrayIdx instead of ArrayIdx
  // itself. This would allow us to handle the shl case for free. However,
  // matching SCEVs has two issues:
  //
  // 1. this would complicate rewriting because the rewriting procedure
  // would have to translate SCEVs back to IR instructions. This translation
  // is difficult when LHS is further evaluated to a composite SCEV.
  //
  // 2. ScalarEvolution is designed to be control-flow oblivious. It tends
  // to strip nsw/nuw flags which are critical for SLSR to trace into
  // sext'ed multiplication.
  if (match(ArrayIdx, m_NSWMul(m_Value(LHS), m_ConstantInt(RHS)))) {
    // SLSR is currently unsafe if i * S may overflow.
    // GEP = Base + sext(LHS *nsw RHS) * ElementSize
    allocateCandidatesAndFindBasisForGEP(Base, RHS, LHS, ElementSize, GEP);
  } else if (match(ArrayIdx, m_NSWShl(m_Value(LHS), m_ConstantInt(RHS)))) {
    // GEP = Base + sext(LHS <<nsw RHS) * ElementSize
    //     = Base + sext(LHS *nsw (1 << RHS)) * ElementSize
    APInt One(RHS->getBitWidth(), 1);
    ConstantInt *PowerOf2 =
        ConstantInt::get(RHS->getContext(), One << RHS->getValue());
    allocateCandidatesAndFindBasisForGEP(Base, PowerOf2, LHS, ElementSize, GEP);
  }
}

bool llvm::decomposeBitTestICmp(const ICmpInst *I, CmpInst::Predicate &Pred,
                                Value *&X, Value *&Y, Value *&Z) {
  ConstantInt *C = dyn_cast<ConstantInt>(I->getOperand(1));
  if (!C)
    return false;

  switch (I->getPredicate()) {
  default:
    return false;
  case ICmpInst::ICMP_SLT:
    // X < 0 is equivalent to (X & SignBit) != 0.
    if (!C->isZero())
      return false;
    Y = ConstantInt::get(I->getContext(), APInt::getSignBit(C->getBitWidth()));
    Pred = ICmpInst::ICMP_NE;
    break;
  case ICmpInst::ICMP_SGT:
    // X > -1 is equivalent to (X & SignBit) == 0.
    if (!C->isAllOnesValue())
      return false;
    Y = ConstantInt::get(I->getContext(), APInt::getSignBit(C->getBitWidth()));
    Pred = ICmpInst::ICMP_EQ;
    break;
  case ICmpInst::ICMP_ULT:
    // X <u 2^n is equivalent to (X & ~(2^n-1)) == 0.
    if (!C->getValue().isPowerOf2())
      return false;
    Y = ConstantInt::get(I->getContext(), -C->getValue());
    Pred = ICmpInst::ICMP_EQ;
    break;
  case ICmpInst::ICMP_UGT:
    // X >u 2^n-1 is equivalent to (X & ~(2^n-1)) != 0.
    if (!(C->getValue() + 1).isPowerOf2())
      return false;
    Y = ConstantInt::get(I->getContext(), ~C->getValue());
    Pred = ICmpInst::ICMP_NE;
    break;
  }

  X = I->getOperand(0);
  Z = ConstantInt::getNullValue(C->getType());
  return true;
}

void StraightLineStrengthReduce::allocateCandidatesAndFindBasisForAdd(
    Value *LHS, Value *RHS, Instruction *I) {
  Value *S = nullptr;
  ConstantInt *Idx = nullptr;
  if (match(RHS, m_Mul(m_Value(S), m_ConstantInt(Idx)))) {
    // I = LHS + RHS = LHS + Idx * S
    allocateCandidatesAndFindBasis(Candidate::Add, SE->getSCEV(LHS), Idx, S, I);
  } else if (match(RHS, m_Shl(m_Value(S), m_ConstantInt(Idx)))) {
    // I = LHS + RHS = LHS + (S << Idx) = LHS + S * (1 << Idx)
    APInt One(Idx->getBitWidth(), 1);
    Idx = ConstantInt::get(Idx->getContext(), One << Idx->getValue());
    allocateCandidatesAndFindBasis(Candidate::Add, SE->getSCEV(LHS), Idx, S, I);
  } else {
    // At least, I = LHS + 1 * RHS
    ConstantInt *One = ConstantInt::get(cast<IntegerType>(I->getType()), 1);
    allocateCandidatesAndFindBasis(Candidate::Add, SE->getSCEV(LHS), One, RHS,
                                   I);
  }
}

/// foldSelectICmpAnd - If one of the constants is zero (we know they can't
/// both be) and we have an icmp instruction with zero, and we have an 'and'
/// with the non-constant value and a power of two we can turn the select
/// into a shift on the result of the 'and'.
static Value *foldSelectICmpAnd(const SelectInst &SI, ConstantInt *TrueVal,
                                ConstantInt *FalseVal,
                                InstCombiner::BuilderTy *Builder) {
  const ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition());
  if (!IC || !IC->isEquality() || !SI.getType()->isIntegerTy())
    return nullptr;

  if (!match(IC->getOperand(1), m_Zero()))
    return nullptr;

  ConstantInt *AndRHS;
  Value *LHS = IC->getOperand(0);
  if (!match(LHS, m_And(m_Value(), m_ConstantInt(AndRHS))))
    return nullptr;

  // If both select arms are non-zero see if we have a select of the form
  // 'x ? 2^n + C : C'. Then we can offset both arms by C, use the logic
  // for 'x ? 2^n : 0' and fix the thing up at the end.
  ConstantInt *Offset = nullptr;
  if (!TrueVal->isZero() && !FalseVal->isZero()) {
    if ((TrueVal->getValue() - FalseVal->getValue()).isPowerOf2())
      Offset = FalseVal;
    else if ((FalseVal->getValue() - TrueVal->getValue()).isPowerOf2())
      Offset = TrueVal;
    else
      return nullptr;

    // Adjust TrueVal and FalseVal to the offset.
    TrueVal = ConstantInt::get(Builder->getContext(),
                               TrueVal->getValue() - Offset->getValue());
    FalseVal = ConstantInt::get(Builder->getContext(),
                                FalseVal->getValue() - Offset->getValue());
  }

  // Make sure the mask in the 'and' and one of the select arms is a power of 2.
  if (!AndRHS->getValue().isPowerOf2() ||
      (!TrueVal->getValue().isPowerOf2() &&
       !FalseVal->getValue().isPowerOf2()))
    return nullptr;

  // Determine which shift is needed to transform result of the 'and' into the
  // desired result.
  ConstantInt *ValC = !TrueVal->isZero() ? TrueVal : FalseVal;
  unsigned ValZeros = ValC->getValue().logBase2();
  unsigned AndZeros = AndRHS->getValue().logBase2();

  // If types don't match we can still convert the select by introducing a zext
  // or a trunc of the 'and'. The trunc case requires that all of the truncated
  // bits are zero, we can figure that out by looking at the 'and' mask.
  if (AndZeros >= ValC->getBitWidth())
    return nullptr;

  Value *V = Builder->CreateZExtOrTrunc(LHS, SI.getType());
  if (ValZeros > AndZeros)
    V = Builder->CreateShl(V, ValZeros - AndZeros);
  else if (ValZeros < AndZeros)
    V = Builder->CreateLShr(V, AndZeros - ValZeros);

  // Okay, now we know that everything is set up, we just don't know whether we
  // have a icmp_ne or icmp_eq and whether the true or false val is the zero.
  bool ShouldNotVal = !TrueVal->isZero();
  ShouldNotVal ^= IC->getPredicate() == ICmpInst::ICMP_NE;
  if (ShouldNotVal)
    V = Builder->CreateXor(V, ValC);

  // Apply an offset if needed.
  if (Offset)
    V = Builder->CreateAdd(V, Offset);
  return V;
}

//.........这里部分代码省略.........
            ConstantInt::get(op1->getType(), APInt::getSignedMaxValue(bw));
          Value *int_min_s =
            ConstantInt::get(op1->getType(), APInt::getSignedMinValue(bw));
          Value *int_max =
            builder.CreateSExt(int_max_s, IntegerType::get(M.getContext(), bw2));
          Value *int_min =
            builder.CreateSExt(int_min_s, IntegerType::get(M.getContext(), bw2));

          if (ii->getIntrinsicID() == Intrinsic::sadd_with_overflow){
            result_ext = builder.CreateAdd(op1ext, op2ext);
          } else if (ii->getIntrinsicID() == Intrinsic::ssub_with_overflow){
            result_ext = builder.CreateSub(op1ext, op2ext);
          } else if (ii->getIntrinsicID() == Intrinsic::smul_with_overflow){
            result_ext = builder.CreateMul(op1ext, op2ext);
          }
          overflow = builder.CreateOr(builder.CreateICmpSGT(result_ext, int_max),
                                      builder.CreateICmpSLT(result_ext, int_min));
        }

        // This trunc cound be replaced by a more general trunc replacement
        // that allows to detect also undefined behavior in assignments or
        // overflow in operation with integers whose dimension is smaller than
        // int's dimension, e.g.
        //     uint8_t = uint8_t + uint8_t;
        // if one desires the wrapping should write
        //     uint8_t = (uint8_t + uint8_t) & 0xFF;
        // before this, must check if it has side effects on other operations
        result = builder.CreateTrunc(result_ext, op1->getType());
        Value *resultStruct =
          builder.CreateInsertValue(UndefValue::get(ii->getType()), result, 0);
        resultStruct = builder.CreateInsertValue(resultStruct, overflow, 1);
        
        ii->replaceAllUsesWith(resultStruct);
        ii->removeFromParent();
        delete ii;
        dirty = true;
        break;
      }

      case Intrinsic::dbg_value:
      case Intrinsic::dbg_declare:
        // Remove these regardless of lower intrinsics flag. This can
        // be removed once IntrinsicLowering is fixed to not have bad
        // caches.
        ii->eraseFromParent();
        dirty = true;
        break;

      case Intrinsic::trap: {
        // Intrisic instruction "llvm.trap" found. Directly lower it to
        // a call of the abort() function.
        Function *F = cast<Function>(
          M.getOrInsertFunction(
            "abort", Type::getVoidTy(getGlobalContext()), NULL));
        F->setDoesNotReturn();
        F->setDoesNotThrow();

        CallInst::Create(F, Twine(), ii);
        new UnreachableInst(getGlobalContext(), ii);

        ii->eraseFromParent();

        dirty = true;
        break;
      }
      case Intrinsic::objectsize: {
        // We don't know the size of an object in general so we replace
        // with 0 or -1 depending on the second argument to the intrinsic.
        assert(ii->getNumArgOperands() == 2 && "wrong number of arguments");
        Value *minArg = ii->getArgOperand(1);
        assert(minArg && "Failed to get second argument");
        ConstantInt *minArgAsInt = dyn_cast<ConstantInt>(minArg);
        assert(minArgAsInt && "Second arg is not a ConstantInt");
        assert(minArgAsInt->getBitWidth() == 1 && "Second argument is not an i1");
        Value *replacement = NULL;
        LLVM_TYPE_Q IntegerType *intType = dyn_cast<IntegerType>(ii->getType());
        assert(intType && "intrinsic does not have integer return type");
        if (minArgAsInt->isZero()) {
          // min=false
          replacement = ConstantInt::get(intType, -1, /*isSigned=*/true);
        } else {
          // min=true
          replacement = ConstantInt::get(intType, 0, /*isSigned=*/false);
        }
        ii->replaceAllUsesWith(replacement);
        ii->eraseFromParent();
        dirty = true;
        break;
      }
      default:
        if (LowerIntrinsics)
          IL->LowerIntrinsicCall(ii);
        dirty = true;
        break;
      }
    }
  }

  return dirty;
}