LowLevelType.h

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//== llvm/CodeGenTypes/LowLevelType.h -------------------------- -*- C++ -*-==//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
/// \file
/// Implement a low-level type suitable for MachineInstr level instruction
/// selection.
///
/// For a type attached to a MachineInstr, we only care about 2 details: total
/// size and the number of vector lanes (if any). Accordingly, there are 4
/// possible valid type-kinds:
///
///    * `sN` for scalars and aggregates
///    * `<N x sM>` for vectors, which must have at least 2 elements.
///    * `pN` for pointers
///
/// Other information required for correct selection is expected to be carried
/// by the opcode, or non-type flags. For example the distinction between G_ADD
/// and G_FADD for int/float or fast-math flags.
///
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_CODEGEN_LOWLEVELTYPE_H
#define LLVM_CODEGEN_LOWLEVELTYPE_H
 
#include "llvm/ADT/DenseMapInfo.h"
#include "llvm/CodeGenTypes/MachineValueType.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include <cassert>
 
namespace llvm {
 
class Type;
class raw_ostream;
 
class LLT {
public:
  /// Get a low-level scalar or aggregate "bag of bits".
  static constexpr LLT scalar(unsigned SizeInBits) {
    return LLT{/*isPointer=*/false, /*isVector=*/false, /*isScalar=*/true,
               ElementCount::getFixed(0), SizeInBits,
               /*AddressSpace=*/0};
  }
 
  /// Get a low-level token; just a scalar with zero bits (or no size).
  static constexpr LLT token() {
    return LLT{/*isPointer=*/false, /*isVector=*/false,
               /*isScalar=*/true,   ElementCount::getFixed(0),
               /*SizeInBits=*/0,
               /*AddressSpace=*/0};
  }
 
  /// Get a low-level pointer in the given address space.
  static constexpr LLT pointer(unsigned AddressSpace, unsigned SizeInBits) {
    assert(SizeInBits > 0 && "invalid pointer size");
    return LLT{/*isPointer=*/true, /*isVector=*/false, /*isScalar=*/false,
               ElementCount::getFixed(0), SizeInBits, AddressSpace};
  }
 
  /// Get a low-level vector of some number of elements and element width.
  static constexpr LLT vector(ElementCount EC, unsigned ScalarSizeInBits) {
    assert(!EC.isScalar() && "invalid number of vector elements");
    return LLT{/*isPointer=*/false, /*isVector=*/true, /*isScalar=*/false,
               EC, ScalarSizeInBits, /*AddressSpace=*/0};
  }
 
  /// Get a low-level vector of some number of elements and element type.
  static constexpr LLT vector(ElementCount EC, LLT ScalarTy) {
    assert(!EC.isScalar() && "invalid number of vector elements");
    assert(!ScalarTy.isVector() && "invalid vector element type");
    return LLT{ScalarTy.isPointer(),
               /*isVector=*/true,
               /*isScalar=*/false,
               EC,
               ScalarTy.getSizeInBits().getFixedValue(),
               ScalarTy.isPointer() ? ScalarTy.getAddressSpace() : 0};
  }
 
  /// Get a 16-bit IEEE half value.
  /// TODO: Add IEEE semantics to type - This currently returns a simple `scalar(16)`.
  static constexpr LLT float16() {
    return scalar(16);
  }
 
  /// Get a 32-bit IEEE float value.
  static constexpr LLT float32() {
    return scalar(32);
  }
 
  /// Get a 64-bit IEEE double value.
  static constexpr LLT float64() {
    return scalar(64);
  }
 
  /// Get a low-level fixed-width vector of some number of elements and element
  /// width.
  static constexpr LLT fixed_vector(unsigned NumElements,
                                    unsigned ScalarSizeInBits) {
    return vector(ElementCount::getFixed(NumElements), ScalarSizeInBits);
  }
 
  /// Get a low-level fixed-width vector of some number of elements and element
  /// type.
  static constexpr LLT fixed_vector(unsigned NumElements, LLT ScalarTy) {
    return vector(ElementCount::getFixed(NumElements), ScalarTy);
  }
 
  /// Get a low-level scalable vector of some number of elements and element
  /// width.
  static constexpr LLT scalable_vector(unsigned MinNumElements,
                                       unsigned ScalarSizeInBits) {
    return vector(ElementCount::getScalable(MinNumElements), ScalarSizeInBits);
  }
 
  /// Get a low-level scalable vector of some number of elements and element
  /// type.
  static constexpr LLT scalable_vector(unsigned MinNumElements, LLT ScalarTy) {
    return vector(ElementCount::getScalable(MinNumElements), ScalarTy);
  }
 
  static constexpr LLT scalarOrVector(ElementCount EC, LLT ScalarTy) {
    return EC.isScalar() ? ScalarTy : LLT::vector(EC, ScalarTy);
  }
 
  static constexpr LLT scalarOrVector(ElementCount EC, uint64_t ScalarSize) {
    assert(ScalarSize <= std::numeric_limits<unsigned>::max() &&
           "Not enough bits in LLT to represent size");
    return scalarOrVector(EC, LLT::scalar(static_cast<unsigned>(ScalarSize)));
  }
 
  explicit constexpr LLT(bool isPointer, bool isVector, bool isScalar,
                         ElementCount EC, uint64_t SizeInBits,
                         unsigned AddressSpace)
      : LLT() {
    init(isPointer, isVector, isScalar, EC, SizeInBits, AddressSpace);
  }
  explicit constexpr LLT()
      : IsScalar(false), IsPointer(false), IsVector(false), RawData(0) {}
 
  LLVM_ABI explicit LLT(MVT VT);
 
  constexpr bool isValid() const { return IsScalar || RawData != 0; }
  constexpr bool isScalar() const { return IsScalar; }
  constexpr bool isToken() const { return IsScalar && RawData == 0; };
  constexpr bool isVector() const { return isValid() && IsVector; }
  constexpr bool isPointer() const {
    return isValid() && IsPointer && !IsVector;
  }
  constexpr bool isPointerVector() const { return IsPointer && isVector(); }
  constexpr bool isPointerOrPointerVector() const {
    return IsPointer && isValid();
  }
 
  /// Returns the number of elements in a vector LLT. Must only be called on
  /// vector types.
  constexpr uint16_t getNumElements() const {
    if (isScalable())
      llvm::reportFatalInternalError(
          "Possible incorrect use of LLT::getNumElements() for "
          "scalable vector. Scalable flag may be dropped, use "
          "LLT::getElementCount() instead");
    return getElementCount().getKnownMinValue();
  }
 
  /// Returns true if the LLT is a scalable vector. Must only be called on
  /// vector types.
  constexpr bool isScalable() const {
    assert(isVector() && "Expected a vector type");
    return getFieldValue(VectorScalableFieldInfo);
  }
 
  /// Returns true if the LLT is a fixed vector. Returns false otherwise, even
  /// if the LLT is not a vector type.
  constexpr bool isFixedVector() const { return isVector() && !isScalable(); }
 
  /// Returns true if the LLT is a scalable vector. Returns false otherwise,
  /// even if the LLT is not a vector type.
  constexpr bool isScalableVector() const { return isVector() && isScalable(); }
 
  constexpr ElementCount getElementCount() const {
    assert(IsVector && "cannot get number of elements on scalar/aggregate");
    return ElementCount::get(getFieldValue(VectorElementsFieldInfo),
                             isScalable());
  }
 
  /// Returns the total size of the type. Must only be called on sized types.
  constexpr TypeSize getSizeInBits() const {
    if (isPointer() || isScalar())
      return TypeSize::getFixed(getScalarSizeInBits());
    auto EC = getElementCount();
    return TypeSize(getScalarSizeInBits() * EC.getKnownMinValue(),
                    EC.isScalable());
  }
 
  /// Returns the total size of the type in bytes, i.e. number of whole bytes
  /// needed to represent the size in bits. Must only be called on sized types.
  constexpr TypeSize getSizeInBytes() const {
    TypeSize BaseSize = getSizeInBits();
    return {(BaseSize.getKnownMinValue() + 7) / 8, BaseSize.isScalable()};
  }
 
  constexpr LLT getScalarType() const {
    return isVector() ? getElementType() : *this;
  }
 
  /// If this type is a vector, return a vector with the same number of elements
  /// but the new element type. Otherwise, return the new element type.
  constexpr LLT changeElementType(LLT NewEltTy) const {
    return isVector() ? LLT::vector(getElementCount(), NewEltTy) : NewEltTy;
  }
 
  /// If this type is a vector, return a vector with the same number of elements
  /// but the new element size. Otherwise, return the new element type. Invalid
  /// for pointer types. For pointer types, use changeElementType.
  constexpr LLT changeElementSize(unsigned NewEltSize) const {
    assert(!isPointerOrPointerVector() &&
           "invalid to directly change element size for pointers");
    return isVector() ? LLT::vector(getElementCount(), NewEltSize)
                      : LLT::scalar(NewEltSize);
  }
 
  /// Return a vector or scalar with the same element type and the new element
  /// count.
  constexpr LLT changeElementCount(ElementCount EC) const {
    return LLT::scalarOrVector(EC, getScalarType());
  }
 
  /// Return a type that is \p Factor times smaller. Reduces the number of
  /// elements if this is a vector, or the bitwidth for scalar/pointers. Does
  /// not attempt to handle cases that aren't evenly divisible.
  constexpr LLT divide(int Factor) const {
    assert(Factor != 1);
    assert((!isScalar() || getScalarSizeInBits() != 0) &&
           "cannot divide scalar of size zero");
    if (isVector()) {
      assert(getElementCount().isKnownMultipleOf(Factor));
      return scalarOrVector(getElementCount().divideCoefficientBy(Factor),
                            getElementType());
    }
 
    assert(getScalarSizeInBits() % Factor == 0);
    return scalar(getScalarSizeInBits() / Factor);
  }
 
  /// Produce a vector type that is \p Factor times bigger, preserving the
  /// element type. For a scalar or pointer, this will produce a new vector with
  /// \p Factor elements.
  constexpr LLT multiplyElements(int Factor) const {
    if (isVector()) {
      return scalarOrVector(getElementCount().multiplyCoefficientBy(Factor),
                            getElementType());
    }
 
    return fixed_vector(Factor, *this);
  }
 
  constexpr bool isByteSized() const {
    return getSizeInBits().isKnownMultipleOf(8);
  }
 
  constexpr unsigned getScalarSizeInBits() const {
    if (isPointerOrPointerVector())
      return getFieldValue(PointerSizeFieldInfo);
    return getFieldValue(ScalarSizeFieldInfo);
  }
 
  constexpr unsigned getAddressSpace() const {
    assert(isPointerOrPointerVector() &&
           "cannot get address space of non-pointer type");
    return getFieldValue(PointerAddressSpaceFieldInfo);
  }
 
  /// Returns the vector's element type. Only valid for vector types.
  constexpr LLT getElementType() const {
    assert(isVector() && "cannot get element type of scalar/aggregate");
    if (IsPointer)
      return pointer(getAddressSpace(), getScalarSizeInBits());
    else
      return scalar(getScalarSizeInBits());
  }
 
  LLVM_ABI void print(raw_ostream &OS) const;
 
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
  LLVM_DUMP_METHOD void dump() const;
#endif
 
  constexpr bool operator==(const LLT &RHS) const {
    return IsPointer == RHS.IsPointer && IsVector == RHS.IsVector &&
           IsScalar == RHS.IsScalar && RHS.RawData == RawData;
  }
 
  constexpr bool operator!=(const LLT &RHS) const { return !(*this == RHS); }
 
  friend struct DenseMapInfo<LLT>;
  friend class GISelInstProfileBuilder;
 
private:
  /// LLT is packed into 64 bits as follows:
  /// isScalar : 1
  /// isPointer : 1
  /// isVector  : 1
  /// with 61 bits remaining for Kind-specific data, packed in bitfields
  /// as described below. As there isn't a simple portable way to pack bits
  /// into bitfields, here the different fields in the packed structure is
  /// described in static const *Field variables. Each of these variables
  /// is a 2-element array, with the first element describing the bitfield size
  /// and the second element describing the bitfield offset.
  ///
  /// +--------+---------+--------+----------+----------------------+
  /// |isScalar|isPointer|isVector| RawData  |Notes                 |
  /// +--------+---------+--------+----------+----------------------+
  /// |   0    |    0    |   0    |    0     |Invalid               |
  /// +--------+---------+--------+----------+----------------------+
  /// |   0    |    0    |   1    |    0     |Tombstone Key         |
  /// +--------+---------+--------+----------+----------------------+
  /// |   0    |    1    |   0    |    0     |Empty Key             |
  /// +--------+---------+--------+----------+----------------------+
  /// |   1    |    0    |   0    |    0     |Token                 |
  /// +--------+---------+--------+----------+----------------------+
  /// |   1    |    0    |   0    | non-zero |Scalar                |
  /// +--------+---------+--------+----------+----------------------+
  /// |   0    |    1    |   0    | non-zero |Pointer               |
  /// +--------+---------+--------+----------+----------------------+
  /// |   0    |    0    |   1    | non-zero |Vector of non-pointer |
  /// +--------+---------+--------+----------+----------------------+
  /// |   0    |    1    |   1    | non-zero |Vector of pointer     |
  /// +--------+---------+--------+----------+----------------------+
  ///
  /// Everything else is reserved.
  typedef int BitFieldInfo[2];
  ///
  /// This is how the bitfields are packed per Kind:
  /// * Invalid:
  ///   gets encoded as RawData == 0, as that is an invalid encoding, since for
  ///   valid encodings, SizeInBits/SizeOfElement must be larger than 0.
  /// * Non-pointer scalar (isPointer == 0 && isVector == 0):
  ///   SizeInBits: 32;
  static const constexpr BitFieldInfo ScalarSizeFieldInfo{32, 29};
  /// * Pointer (isPointer == 1 && isVector == 0):
  ///   SizeInBits: 16;
  ///   AddressSpace: 24;
  static const constexpr BitFieldInfo PointerSizeFieldInfo{16, 45};
  static const constexpr BitFieldInfo PointerAddressSpaceFieldInfo{24, 21};
  /// * Vector-of-non-pointer (isPointer == 0 && isVector == 1):
  ///   NumElements: 16;
  ///   SizeOfElement: 32;
  ///   Scalable: 1;
  static const constexpr BitFieldInfo VectorElementsFieldInfo{16, 5};
  static const constexpr BitFieldInfo VectorScalableFieldInfo{1, 0};
  /// * Vector-of-pointer (isPointer == 1 && isVector == 1):
  ///   NumElements: 16;
  ///   SizeOfElement: 16;
  ///   AddressSpace: 24;
  ///   Scalable: 1;
 
  uint64_t IsScalar : 1;
  uint64_t IsPointer : 1;
  uint64_t IsVector : 1;
  uint64_t RawData : 61;
 
  static constexpr uint64_t getMask(const BitFieldInfo FieldInfo) {
    const int FieldSizeInBits = FieldInfo[0];
    return (((uint64_t)1) << FieldSizeInBits) - 1;
  }
  static constexpr uint64_t maskAndShift(uint64_t Val, uint64_t Mask,
                                         uint8_t Shift) {
    assert(Val <= Mask && "Value too large for field");
    return (Val & Mask) << Shift;
  }
  static constexpr uint64_t maskAndShift(uint64_t Val,
                                         const BitFieldInfo FieldInfo) {
    return maskAndShift(Val, getMask(FieldInfo), FieldInfo[1]);
  }
 
  constexpr uint64_t getFieldValue(const BitFieldInfo FieldInfo) const {
    return getMask(FieldInfo) & (RawData >> FieldInfo[1]);
  }
 
  constexpr void init(bool IsPointer, bool IsVector, bool IsScalar,
                      ElementCount EC, uint64_t SizeInBits,
                      unsigned AddressSpace) {
    assert(SizeInBits <= std::numeric_limits<unsigned>::max() &&
           "Not enough bits in LLT to represent size");
    this->IsPointer = IsPointer;
    this->IsVector = IsVector;
    this->IsScalar = IsScalar;
    if (IsPointer) {
      RawData = maskAndShift(SizeInBits, PointerSizeFieldInfo) |
                maskAndShift(AddressSpace, PointerAddressSpaceFieldInfo);
    } else {
      RawData = maskAndShift(SizeInBits, ScalarSizeFieldInfo);
    }
    if (IsVector) {
      RawData |= maskAndShift(EC.getKnownMinValue(), VectorElementsFieldInfo) |
                 maskAndShift(EC.isScalable() ? 1 : 0, VectorScalableFieldInfo);
    }
  }
 
public:
  constexpr uint64_t getUniqueRAWLLTData() const {
    return ((uint64_t)RawData) << 3 | ((uint64_t)IsScalar) << 2 |
           ((uint64_t)IsPointer) << 1 | ((uint64_t)IsVector);
  }
};
 
inline raw_ostream& operator<<(raw_ostream &OS, const LLT &Ty) {
  Ty.print(OS);
  return OS;
}
 
template<> struct DenseMapInfo<LLT> {
  static inline LLT getEmptyKey() {
    LLT Invalid;
    Invalid.IsPointer = true;
    return Invalid;
  }
  static inline LLT getTombstoneKey() {
    LLT Invalid;
    Invalid.IsVector = true;
    return Invalid;
  }
  static inline unsigned getHashValue(const LLT &Ty) {
    uint64_t Val = Ty.getUniqueRAWLLTData();
    return DenseMapInfo<uint64_t>::getHashValue(Val);
  }
  static bool isEqual(const LLT &LHS, const LLT &RHS) {
    return LHS == RHS;
  }
};
 
}
 
#endif // LLVM_CODEGEN_LOWLEVELTYPE_H