src/aarch64/cpu-features-auditor-aarch64.h

// Copyright 2018, VIXL authors
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#ifndef VIXL_AARCH64_CPU_FEATURES_AUDITOR_AARCH64_H_
#define VIXL_AARCH64_CPU_FEATURES_AUDITOR_AARCH64_H_

#include <iostream>

#include "cpu-features.h"
#include "decoder-aarch64.h"

namespace vixl {
namespace aarch64 {

// This visitor records the CPU features that each decoded instruction requires.
// It provides:
//  - the set of CPU features required by the most recently decoded instruction,
//  - a cumulative set of encountered CPU features,
//  - an optional list of 'available' CPU features.
//
// Primarily, this allows the Disassembler and Simulator to share the same CPU
// features logic. However, it can be used standalone to scan code blocks for
// CPU features.
class CPUFeaturesAuditor : public DecoderVisitor {
 public:
  // Construction arguments:
  //   - If a decoder is specified, the CPUFeaturesAuditor automatically
  //     registers itself as a visitor. Otherwise, this can be done manually.
  //
  //   - If an `available` features list is provided, it is used as a hint in
  //     cases where instructions may be provided by multiple separate features.
  //     An example of this is FP&SIMD loads and stores: some of these are used
  //     in both FP and integer SIMD code. If exactly one of those features is
  //     in `available` when one of these instructions is encountered, then the
  //     auditor will record that feature. Otherwise, it will record _both_
  //     features.
  explicit CPUFeaturesAuditor(
      Decoder* decoder, const CPUFeatures& available = CPUFeatures::None())
      : available_(available), decoder_(decoder) {
    if (decoder_ != NULL) decoder_->AppendVisitor(this);
  }

  explicit CPUFeaturesAuditor(
      const CPUFeatures& available = CPUFeatures::None())
      : available_(available), decoder_(NULL) {}

  virtual ~CPUFeaturesAuditor() {
    if (decoder_ != NULL) decoder_->RemoveVisitor(this);
  }

  void ResetSeenFeatures() {
    seen_ = CPUFeatures::None();
    last_instruction_ = CPUFeatures::None();
  }

  // Query or set available CPUFeatures.
  const CPUFeatures& GetAvailableFeatures() const { return available_; }
  void SetAvailableFeatures(const CPUFeatures& available) {
    available_ = available;
  }

  // Query CPUFeatures seen since construction (or the last call to `Reset()`).
  const CPUFeatures& GetSeenFeatures() const { return seen_; }

  // Query CPUFeatures from the last instruction visited by this auditor.
  const CPUFeatures& GetInstructionFeatures() const {
    return last_instruction_;
  }

  bool InstructionIsAvailable() const {
    return available_.Has(last_instruction_);
  }

  // The common CPUFeatures interface operates on the available_ list.
  CPUFeatures* GetCPUFeatures() { return &available_; }
  void SetCPUFeatures(const CPUFeatures& available) {
    SetAvailableFeatures(available);
  }

// Declare all Visitor functions.
#define DECLARE(A) \
  virtual void Visit##A(const Instruction* instr) VIXL_OVERRIDE;
  VISITOR_LIST(DECLARE)
#undef DECLARE

 private:
  class RecordInstructionFeaturesScope;

  void LoadStoreHelper(const Instruction* instr);
  void LoadStorePairHelper(const Instruction* instr);

  CPUFeatures seen_;
  CPUFeatures last_instruction_;
  CPUFeatures available_;

  Decoder* decoder_;
};

}  // namespace aarch64
}  // namespace vixl

#endif  // VIXL_AARCH64_CPU_FEATURES_AUDITOR_AARCH64_H_