1//===-- RegisterAliasingTracker.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/// \file
10/// Defines classes to keep track of register aliasing.
11///
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_TOOLS_LLVM_EXEGESIS_ALIASINGTRACKER_H
15#define LLVM_TOOLS_LLVM_EXEGESIS_ALIASINGTRACKER_H
16
17#include <memory>
18#include <unordered_map>
19
20#include "llvm/ADT/BitVector.h"
21#include "llvm/ADT/PackedVector.h"
22#include "llvm/MC/MCRegisterInfo.h"
23
24namespace llvm {
25namespace exegesis {
26
27// Returns the registers that are aliased by the ones set in SourceBits.
28BitVector getAliasedBits(const MCRegisterInfo &RegInfo,
29 const BitVector &SourceBits);
30
31// Keeps track of a mapping from one register (or a register class) to its
32// aliased registers.
33//
34// e.g.
35// RegisterAliasingTracker Tracker(RegInfo, X86::EAX);
36// Tracker.sourceBits() == { X86::EAX }
37// Tracker.aliasedBits() == { X86::AL, X86::AH, X86::AX,
38// X86::EAX,X86::HAX, X86::RAX }
39// Tracker.getOrigin(X86::AL) == X86::EAX;
40// Tracker.getOrigin(X86::BX) == -1;
41struct RegisterAliasingTracker {
42 // Construct a tracker from an MCRegisterClass.
43 RegisterAliasingTracker(const MCRegisterInfo &RegInfo,
44 const BitVector &ReservedReg,
45 const MCRegisterClass &RegClass);
46
47 // Construct a tracker from an MCRegister.
48 RegisterAliasingTracker(const MCRegisterInfo &RegInfo,
49 const MCRegister Register);
50
51 const BitVector &sourceBits() const { return SourceBits; }
52
53 // Retrieves all the touched registers as a BitVector.
54 const BitVector &aliasedBits() const { return AliasedBits; }
55
56 // Returns the origin of this register or -1.
57 int getOrigin(MCPhysReg Aliased) const {
58 if (!AliasedBits[Aliased])
59 return -1;
60 return Origins[Aliased];
61 }
62
63private:
64 RegisterAliasingTracker(const MCRegisterInfo &RegInfo);
65 RegisterAliasingTracker(const RegisterAliasingTracker &) = delete;
66
67 void FillOriginAndAliasedBits(const MCRegisterInfo &RegInfo,
68 const BitVector &OriginalBits);
69
70 BitVector SourceBits;
71 BitVector AliasedBits;
72 PackedVector<size_t, 10> Origins; // Max 1024 physical registers.
73};
74
75// A cache of existing trackers.
76struct RegisterAliasingTrackerCache {
77 // RegInfo must outlive the cache.
78 RegisterAliasingTrackerCache(const MCRegisterInfo &RegInfo,
79 const BitVector &ReservedReg);
80
81 // Convenient function to retrieve a BitVector of the right size.
82 const BitVector &emptyRegisters() const { return EmptyRegisters; }
83
84 // Convenient function to retrieve the registers the function body can't use.
85 const BitVector &reservedRegisters() const { return ReservedReg; }
86
87 // Convenient function to retrieve the underlying MCRegInfo.
88 const MCRegisterInfo &regInfo() const { return RegInfo; }
89
90 // Retrieves the RegisterAliasingTracker for this particular register.
91 const RegisterAliasingTracker &getRegister(MCRegister Reg) const;
92
93 // Retrieves the RegisterAliasingTracker for this particular register class.
94 const RegisterAliasingTracker &getRegisterClass(unsigned RegClassIndex) const;
95
96private:
97 const MCRegisterInfo &RegInfo;
98 const BitVector ReservedReg;
99 const BitVector EmptyRegisters;
100 mutable std::unordered_map<unsigned, std::unique_ptr<RegisterAliasingTracker>>
101 Registers;
102 mutable std::unordered_map<unsigned, std::unique_ptr<RegisterAliasingTracker>>
103 RegisterClasses;
104};
105
106// `a = a & ~b`, optimized for few bit sets in B and no allocation.
107inline void remove(BitVector &A, const BitVector &B) {
108 assert(A.size() == B.size());
109 for (auto I : B.set_bits())
110 A.reset(Idx: I);
111}
112
113// Returns a debug string for the list of registers.
114std::string debugString(const MCRegisterInfo &RegInfo, const BitVector &Regs);
115
116} // namespace exegesis
117} // namespace llvm
118
119#endif // LLVM_TOOLS_LLVM_EXEGESIS_ALIASINGTRACKER_H
120