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
12 namespace v8 {
13
14 namespace 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.
28 template <typename SubType, int kAfterLastRegister>
29 class RegisterBase {
30 public:
31 static constexpr int8_t kCode_no_reg = -1;
32 static constexpr int8_t kNumRegisters = kAfterLastRegister;
33
no_reg()34 static constexpr SubType no_reg() { return SubType{kCode_no_reg}; }
35
from_code(int8_t code)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
is_valid() const41 constexpr bool is_valid() const { return reg_code_ != kCode_no_reg; }
42
code() const43 constexpr int8_t code() const {
44 DCHECK(is_valid());
45 return reg_code_;
46 }
47
operator ==(SubType other) const48 inline constexpr bool operator==(SubType other) const {
49 return reg_code_ == other.reg_code_;
50 }
operator !=(SubType other) const51 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.
GetSpecialRegisterName(int code)56 static const char* GetSpecialRegisterName(int code) { return "UNKNOWN"; }
57
58 protected:
RegisterBase(int code)59 explicit constexpr RegisterBase(int code) : reg_code_(code) {}
60
61 private:
62 int8_t reg_code_;
63 STATIC_ASSERT(kAfterLastRegister <= kMaxInt8);
64 };
65
66 template <typename RegType,
67 typename = decltype(RegisterName(std::declval<RegType>()))>
operator <<(std::ostream& os, RegType reg)68 inline 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