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_MCREGISTER_H
10 #define LLVM_MC_MCREGISTER_H
11 
12 #include "llvm/ADT/DenseMapInfo.h"
13 #include "llvm/ADT/Hashing.h"
14 #include <cassert>
15 #include <limits>
16 
17 namespace llvm {
18 
19 /// An unsigned integer type large enough to represent all physical registers,
20 /// but not necessarily virtual registers.
21 using MCPhysReg = uint16_t;
22 
23 /// Wrapper class representing physical registers. Should be passed by value.
24 class MCRegister {
25   friend hash_code hash_value(const MCRegister &);
26   unsigned Reg;
27 
28 public:
29   constexpr MCRegister(unsigned Val = 0): Reg(Val) {}
30 
31   // Register numbers can represent physical registers, virtual registers, and
32   // sometimes stack slots. The unsigned values are divided into these ranges:
33   //
34   //   0           Not a register, can be used as a sentinel.
35   //   [1;2^30)    Physical registers assigned by TableGen.
36   //   [2^30;2^31) Stack slots. (Rarely used.)
37   //   [2^31;2^32) Virtual registers assigned by MachineRegisterInfo.
38   //
39   // Further sentinels can be allocated from the small negative integers.
40   // DenseMapInfo<unsigned> uses -1u and -2u.
41   static_assert(std::numeric_limits<decltype(Reg)>::max() >= 0xFFFFFFFF,
42                 "Reg isn't large enough to hold full range.");
43   static constexpr unsigned NoRegister = 0u;
44   static constexpr unsigned FirstPhysicalReg = 1u;
45   static constexpr unsigned FirstStackSlot = 1u << 30;
46   static constexpr unsigned VirtualRegFlag = 1u << 31;
47 
48   /// This is the portion of the positive number space that is not a physical
49   /// register. StackSlot values do not exist in the MC layer, see
50   /// Register::isStackSlot() for the more information on them.
51   ///
52   static bool isStackSlot(unsigned Reg) {
53     return FirstStackSlot <= Reg && Reg < VirtualRegFlag;
54   }
55 
56   /// Return true if the specified register number is in
57   /// the physical register namespace.
58   static bool isPhysicalRegister(unsigned Reg) {
59     return FirstPhysicalReg <= Reg && Reg < FirstStackSlot;
60   }
61 
62   constexpr operator unsigned() const {
63     return Reg;
64   }
65 
66   /// Check the provided unsigned value is a valid MCRegister.
67   static MCRegister from(unsigned Val) {
68     assert(Val == NoRegister || isPhysicalRegister(Val));
69     return MCRegister(Val);
70   }
71 
72   unsigned id() const {
73     return Reg;
74   }
75 
76   bool isValid() const { return Reg != NoRegister; }
77 
78   /// Comparisons between register objects
79   bool operator==(const MCRegister &Other) const { return Reg == Other.Reg; }
80   bool operator!=(const MCRegister &Other) const { return Reg != Other.Reg; }
81 
82   /// Comparisons against register constants. E.g.
83   /// * R == AArch64::WZR
84   /// * R == 0
85   /// * R == VirtRegMap::NO_PHYS_REG
86   bool operator==(unsigned Other) const { return Reg == Other; }
87   bool operator!=(unsigned Other) const { return Reg != Other; }
88   bool operator==(int Other) const { return Reg == unsigned(Other); }
89   bool operator!=(int Other) const { return Reg != unsigned(Other); }
90   // MSVC requires that we explicitly declare these two as well.
91   bool operator==(MCPhysReg Other) const { return Reg == unsigned(Other); }
92   bool operator!=(MCPhysReg Other) const { return Reg != unsigned(Other); }
93 };
94 
95 // Provide DenseMapInfo for MCRegister
96 template<> struct DenseMapInfo<MCRegister> {
97   static inline unsigned getEmptyKey() {
98     return DenseMapInfo<unsigned>::getEmptyKey();
99   }
100   static inline unsigned getTombstoneKey() {
101     return DenseMapInfo<unsigned>::getTombstoneKey();
102   }
103   static unsigned getHashValue(const MCRegister &Val) {
104     return DenseMapInfo<unsigned>::getHashValue(Val.id());
105   }
106   static bool isEqual(const MCRegister &LHS, const MCRegister &RHS) {
107     return DenseMapInfo<unsigned>::isEqual(LHS.id(), RHS.id());
108   }
109 };
110 
111 inline hash_code hash_value(const MCRegister &Reg) {
112   return hash_value(Reg.id());
113 }
114 }
115 
116 #endif // LLVM_MC_MCREGISTER_H
117