1 //===-- llvm/MC/Register.h --------------------------------------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #ifndef LLVM_MC_REGISTER_H
10 #define LLVM_MC_REGISTER_H
11 
12 #include "llvm/ADT/DenseMapInfo.h"
13 #include <cassert>
14 
15 namespace llvm {
16 
17 /// An unsigned integer type large enough to represent all physical registers,
18 /// but not necessarily virtual registers.
19 using MCPhysReg = uint16_t;
20 
21 /// Wrapper class representing physical registers. Should be passed by value.
22 class MCRegister {
23   friend hash_code hash_value(const MCRegister &);
24   unsigned Reg;
25 
26 public:
27   constexpr MCRegister(unsigned Val = 0): Reg(Val) {}
28 
29   // Register numbers can represent physical registers, virtual registers, and
30   // sometimes stack slots. The unsigned values are divided into these ranges:
31   //
32   //   0           Not a register, can be used as a sentinel.
33   //   [1;2^30)    Physical registers assigned by TableGen.
34   //   [2^30;2^31) Stack slots. (Rarely used.)
35   //   [2^31;2^32) Virtual registers assigned by MachineRegisterInfo.
36   //
37   // Further sentinels can be allocated from the small negative integers.
38   // DenseMapInfo<unsigned> uses -1u and -2u.
39   static_assert(std::numeric_limits<decltype(Reg)>::max() >= 0xFFFFFFFF,
40                 "Reg isn't large enough to hold full range.");
41   static constexpr unsigned NoRegister = 0u;
42   static constexpr unsigned FirstPhysicalReg = 1u;
43   static constexpr unsigned FirstStackSlot = 1u << 30;
44   static constexpr unsigned VirtualRegFlag = 1u << 31;
45 
46   /// This is the portion of the positive number space that is not a physical
47   /// register. StackSlot values do not exist in the MC layer, see
48   /// Register::isStackSlot() for the more information on them.
49   ///
50   static bool isStackSlot(unsigned Reg) {
51     return FirstStackSlot <= Reg && Reg < VirtualRegFlag;
52   }
53 
54   /// Return true if the specified register number is in
55   /// the physical register namespace.
56   static bool isPhysicalRegister(unsigned Reg) {
57     return FirstPhysicalReg <= Reg && Reg < FirstStackSlot;
58   }
59 
60   constexpr operator unsigned() const {
61     return Reg;
62   }
63 
64   /// Check the provided unsigned value is a valid MCRegister.
65   static MCRegister from(unsigned Val) {
66     assert(Val == NoRegister || isPhysicalRegister(Val));
67     return MCRegister(Val);
68   }
69 
70   unsigned id() const {
71     return Reg;
72   }
73 
74   bool isValid() const { return Reg != NoRegister; }
75 
76   /// Comparisons between register objects
77   bool operator==(const MCRegister &Other) const { return Reg == Other.Reg; }
78   bool operator!=(const MCRegister &Other) const { return Reg != Other.Reg; }
79 
80   /// Comparisons against register constants. E.g.
81   /// * R == AArch64::WZR
82   /// * R == 0
83   /// * R == VirtRegMap::NO_PHYS_REG
84   bool operator==(unsigned Other) const { return Reg == Other; }
85   bool operator!=(unsigned Other) const { return Reg != Other; }
86   bool operator==(int Other) const { return Reg == unsigned(Other); }
87   bool operator!=(int Other) const { return Reg != unsigned(Other); }
88   // MSVC requires that we explicitly declare these two as well.
89   bool operator==(MCPhysReg Other) const { return Reg == unsigned(Other); }
90   bool operator!=(MCPhysReg Other) const { return Reg != unsigned(Other); }
91 };
92 
93 // Provide DenseMapInfo for MCRegister
94 template<> struct DenseMapInfo<MCRegister> {
95   static inline unsigned getEmptyKey() {
96     return DenseMapInfo<unsigned>::getEmptyKey();
97   }
98   static inline unsigned getTombstoneKey() {
99     return DenseMapInfo<unsigned>::getTombstoneKey();
100   }
101   static unsigned getHashValue(const MCRegister &Val) {
102     return DenseMapInfo<unsigned>::getHashValue(Val.id());
103   }
104   static bool isEqual(const MCRegister &LHS, const MCRegister &RHS) {
105     return DenseMapInfo<unsigned>::isEqual(LHS.id(), RHS.id());
106   }
107 };
108 
109 inline hash_code hash_value(const MCRegister &Reg) {
110   return hash_value(Reg.id());
111 }
112 }
113 
114 #endif // ifndef LLVM_MC_REGISTER_H
115