runtime/arch/arm64/instruction_set_features_arm64.h

/*
 * Copyright (C) 2014 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef ART_RUNTIME_ARCH_ARM64_INSTRUCTION_SET_FEATURES_ARM64_H_
#define ART_RUNTIME_ARCH_ARM64_INSTRUCTION_SET_FEATURES_ARM64_H_

#include "arch/instruction_set_features.h"

namespace art {

// SVE is currently not enabled.
static constexpr bool kArm64AllowSVE = false;

class Arm64InstructionSetFeatures;
using Arm64FeaturesUniquePtr = std::unique_ptr<const Arm64InstructionSetFeatures>;

// Instruction set features relevant to the ARM64 architecture.
class Arm64InstructionSetFeatures final : public InstructionSetFeatures {
 public:
  // Process a CPU variant string like "krait" or "cortex-a15" and create InstructionSetFeatures.
  static Arm64FeaturesUniquePtr FromVariant(const std::string& variant, std::string* error_msg);

  // Parse a bitmap and create an InstructionSetFeatures.
  static Arm64FeaturesUniquePtr FromBitmap(uint32_t bitmap);

  // Turn C pre-processor #defines into the equivalent instruction set features.
  static Arm64FeaturesUniquePtr FromCppDefines();

  // Process /proc/cpuinfo and use kRuntimeISA to produce InstructionSetFeatures.
  static Arm64FeaturesUniquePtr FromCpuInfo();

  // Process the auxiliary vector AT_HWCAP entry and use kRuntimeISA to produce
  // InstructionSetFeatures.
  static Arm64FeaturesUniquePtr FromHwcap();

  // Use assembly tests of the current runtime (ie kRuntimeISA) to determine the
  // InstructionSetFeatures. This works around kernel bugs in AT_HWCAP and /proc/cpuinfo.
  static Arm64FeaturesUniquePtr FromAssembly();

  // Use external cpu_features library.
  static Arm64FeaturesUniquePtr FromCpuFeatures();

  // Return a new set of instruction set features, intersecting `this` features
  // with hardware capabilities.
  Arm64FeaturesUniquePtr IntersectWithHwcap() const;

  bool Equals(const InstructionSetFeatures* other) const override;

  // Note that newer CPUs do not have a53 erratum 835769 and 843419,
  // so the two a53 fix features (fix_cortex_a53_835769 and fix_cortex_a53_843419)
  // are not tested for HasAtLeast.
  bool HasAtLeast(const InstructionSetFeatures* other) const override;

  InstructionSet GetInstructionSet() const override {
    return InstructionSet::kArm64;
  }

  uint32_t AsBitmap() const override;

  // Return a string of the form "a53" or "none".
  std::string GetFeatureString() const override;

  // Generate code addressing Cortex-A53 erratum 835769?
  bool NeedFixCortexA53_835769() const {
      return fix_cortex_a53_835769_;
  }

  // Generate code addressing Cortex-A53 erratum 843419?
  bool NeedFixCortexA53_843419() const {
      return fix_cortex_a53_843419_;
  }

  bool HasCRC() const {
    return has_crc_;
  }

  bool HasLSE() const {
    return has_lse_;
  }

  bool HasFP16() const {
    return has_fp16_;
  }

  // Are Dot Product instructions (UDOT/SDOT) available?
  bool HasDotProd() const {
    return has_dotprod_;
  }

  bool HasSVE() const {
    return kArm64AllowSVE && has_sve_;
  }

  size_t GetSVEVectorLength() const {
    // TODO: support SVE vector length detection.
    return kArm64DefaultSVEVectorLength;
  }

  virtual ~Arm64InstructionSetFeatures() {}

 protected:
  // Parse a vector of the form "a53" adding these to a new ArmInstructionSetFeatures.
  std::unique_ptr<const InstructionSetFeatures>
      AddFeaturesFromSplitString(const std::vector<std::string>& features,
                                 std::string* error_msg) const override;

  std::unique_ptr<const InstructionSetFeatures>
      AddRuntimeDetectedFeatures(const InstructionSetFeatures *features) const override;

 private:
  Arm64InstructionSetFeatures(bool needs_a53_835769_fix,
                              bool needs_a53_843419_fix,
                              bool has_crc,
                              bool has_lse,
                              bool has_fp16,
                              bool has_dotprod,
                              bool has_sve)
      : InstructionSetFeatures(),
        fix_cortex_a53_835769_(needs_a53_835769_fix),
        fix_cortex_a53_843419_(needs_a53_843419_fix),
        has_crc_(has_crc),
        has_lse_(has_lse),
        has_fp16_(has_fp16),
        has_dotprod_(has_dotprod),
        has_sve_(has_sve) {
  }

  // Bitmap positions for encoding features as a bitmap.
  enum {
    kA53Bitfield = 1 << 0,
    kCRCBitField = 1 << 1,
    kLSEBitField = 1 << 2,
    kFP16BitField = 1 << 3,
    kDotProdBitField = 1 << 4,
    kSVEBitField = 1 << 5,
  };

  const bool fix_cortex_a53_835769_;
  const bool fix_cortex_a53_843419_;
  const bool has_crc_;      // optional in ARMv8.0, mandatory in ARMv8.1.
  const bool has_lse_;      // ARMv8.1 Large System Extensions.
  const bool has_fp16_;     // ARMv8.2 FP16 extensions.
  const bool has_dotprod_;  // optional in ARMv8.2, mandatory in ARMv8.4.
  const bool has_sve_;      // optional in ARMv8.2.

  DISALLOW_COPY_AND_ASSIGN(Arm64InstructionSetFeatures);
};

}  // namespace art

#endif  // ART_RUNTIME_ARCH_ARM64_INSTRUCTION_SET_FEATURES_ARM64_H_