1// Copyright 2012 the V8 project authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef V8_CODEGEN_REGISTER_BASE_H_
6#define V8_CODEGEN_REGISTER_BASE_H_
7
8#include "src/base/bits.h"
9#include "src/base/bounds.h"
10#include "src/common/globals.h"
11
12namespace v8 {
13
14namespace internal {
15
16// Base type for CPU Registers.
17//
18// 1) We would prefer to use an enum for registers, but enum values are
19// assignment-compatible with int, which has caused code-generation bugs.
20//
21// 2) By not using an enum, we are possibly preventing the compiler from
22// doing certain constant folds, which may significantly reduce the
23// code generated for some assembly instructions (because they boil down
24// to a few constants). If this is a problem, we could change the code
25// such that we use an enum in optimized mode, and the class in debug
26// mode. This way we get the compile-time error checking in debug mode
27// and best performance in optimized code.
28template <typename SubType, int kAfterLastRegister>
29class RegisterBase {
30 public:
31  static constexpr int8_t kCode_no_reg = -1;
32  static constexpr int8_t kNumRegisters = kAfterLastRegister;
33
34  static constexpr SubType no_reg() { return SubType{kCode_no_reg}; }
35
36  static constexpr SubType from_code(int8_t code) {
37    DCHECK(base::IsInRange(static_cast<int>(code), 0, kNumRegisters - 1));
38    return SubType{code};
39  }
40
41  constexpr bool is_valid() const { return reg_code_ != kCode_no_reg; }
42
43  constexpr int8_t code() const {
44    DCHECK(is_valid());
45    return reg_code_;
46  }
47
48  inline constexpr bool operator==(SubType other) const {
49    return reg_code_ == other.reg_code_;
50  }
51  inline constexpr bool operator!=(SubType other) const {
52    return reg_code_ != other.reg_code_;
53  }
54
55  // Used to print the name of some special registers.
56  static const char* GetSpecialRegisterName(int code) { return "UNKNOWN"; }
57
58 protected:
59  explicit constexpr RegisterBase(int code) : reg_code_(code) {}
60
61 private:
62  int8_t reg_code_;
63  STATIC_ASSERT(kAfterLastRegister <= kMaxInt8);
64};
65
66template <typename RegType,
67          typename = decltype(RegisterName(std::declval<RegType>()))>
68inline std::ostream& operator<<(std::ostream& os, RegType reg) {
69  return os << RegisterName(reg);
70}
71
72// Helper macros to define a {RegisterName} method based on a macro list
73// containing all names.
74#define DEFINE_REGISTER_NAMES_NAME(name) #name,
75#define DEFINE_REGISTER_NAMES(RegType, LIST)                                   \
76  inline const char* RegisterName(RegType reg) {                               \
77    static constexpr const char* Names[] = {LIST(DEFINE_REGISTER_NAMES_NAME)}; \
78    STATIC_ASSERT(arraysize(Names) == RegType::kNumRegisters);                 \
79    return reg.is_valid() ? Names[reg.code()] : "invalid";                     \
80  }
81
82}  // namespace internal
83}  // namespace v8
84
85#endif  // V8_CODEGEN_REGISTER_BASE_H_
86