MCLinkerOptimizationHint.h revision 360784 
1//===- MCLinkerOptimizationHint.h - LOH interface ---------------*- C++ -*-===//
2//
3//
4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5// See https://llvm.org/LICENSE.txt for license information.
6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7//
8//===----------------------------------------------------------------------===//
9//
10// This file declares some helpers classes to handle Linker Optimization Hint
11// (LOH).
12//
13// FIXME: LOH interface supports only MachO format at the moment.
14//===----------------------------------------------------------------------===//
15
16#ifndef LLVM_MC_MCLINKEROPTIMIZATIONHINT_H
17#define LLVM_MC_MCLINKEROPTIMIZATIONHINT_H
18
19#include "llvm/ADT/SmallVector.h"
20#include "llvm/ADT/StringRef.h"
21#include "llvm/ADT/StringSwitch.h"
22#include "llvm/Support/raw_ostream.h"
23#include <cassert>
24#include <cstdint>
25
26namespace llvm {
27
28class MachObjectWriter;
29class MCAsmLayout;
30class MCSymbol;
31
32/// Linker Optimization Hint Type.
33enum MCLOHType {
34  MCLOH_AdrpAdrp = 0x1u,      ///< Adrp xY, _v1@PAGE -> Adrp xY, _v2@PAGE.
35  MCLOH_AdrpLdr = 0x2u,       ///< Adrp _v@PAGE -> Ldr _v@PAGEOFF.
36  MCLOH_AdrpAddLdr = 0x3u,    ///< Adrp _v@PAGE -> Add _v@PAGEOFF -> Ldr.
37  MCLOH_AdrpLdrGotLdr = 0x4u, ///< Adrp _v@GOTPAGE -> Ldr _v@GOTPAGEOFF -> Ldr.
38  MCLOH_AdrpAddStr = 0x5u,    ///< Adrp _v@PAGE -> Add _v@PAGEOFF -> Str.
39  MCLOH_AdrpLdrGotStr = 0x6u, ///< Adrp _v@GOTPAGE -> Ldr _v@GOTPAGEOFF -> Str.
40  MCLOH_AdrpAdd = 0x7u,       ///< Adrp _v@PAGE -> Add _v@PAGEOFF.
41  MCLOH_AdrpLdrGot = 0x8u     ///< Adrp _v@GOTPAGE -> Ldr _v@GOTPAGEOFF.
42};
43
44static inline StringRef MCLOHDirectiveName() {
45  return StringRef(".loh");
46}
47
48static inline bool isValidMCLOHType(unsigned Kind) {
49  return Kind >= MCLOH_AdrpAdrp && Kind <= MCLOH_AdrpLdrGot;
50}
51
52static inline int MCLOHNameToId(StringRef Name) {
53#define MCLOHCaseNameToId(Name)     .Case(#Name, MCLOH_ ## Name)
54  return StringSwitch<int>(Name)
55    MCLOHCaseNameToId(AdrpAdrp)
56    MCLOHCaseNameToId(AdrpLdr)
57    MCLOHCaseNameToId(AdrpAddLdr)
58    MCLOHCaseNameToId(AdrpLdrGotLdr)
59    MCLOHCaseNameToId(AdrpAddStr)
60    MCLOHCaseNameToId(AdrpLdrGotStr)
61    MCLOHCaseNameToId(AdrpAdd)
62    MCLOHCaseNameToId(AdrpLdrGot)
63    .Default(-1);
64#undef MCLOHCaseNameToId
65}
66
67static inline StringRef MCLOHIdToName(MCLOHType Kind) {
68#define MCLOHCaseIdToName(Name)      case MCLOH_ ## Name: return StringRef(#Name);
69  switch (Kind) {
70    MCLOHCaseIdToName(AdrpAdrp);
71    MCLOHCaseIdToName(AdrpLdr);
72    MCLOHCaseIdToName(AdrpAddLdr);
73    MCLOHCaseIdToName(AdrpLdrGotLdr);
74    MCLOHCaseIdToName(AdrpAddStr);
75    MCLOHCaseIdToName(AdrpLdrGotStr);
76    MCLOHCaseIdToName(AdrpAdd);
77    MCLOHCaseIdToName(AdrpLdrGot);
78  }
79  return StringRef();
80#undef MCLOHCaseIdToName
81}
82
83static inline int MCLOHIdToNbArgs(MCLOHType Kind) {
84  switch (Kind) {
85    // LOH with two arguments
86  case MCLOH_AdrpAdrp:
87  case MCLOH_AdrpLdr:
88  case MCLOH_AdrpAdd:
89  case MCLOH_AdrpLdrGot:
90    return 2;
91    // LOH with three arguments
92  case MCLOH_AdrpAddLdr:
93  case MCLOH_AdrpLdrGotLdr:
94  case MCLOH_AdrpAddStr:
95  case MCLOH_AdrpLdrGotStr:
96    return 3;
97  }
98  return -1;
99}
100
101/// Store Linker Optimization Hint information (LOH).
102class MCLOHDirective {
103  MCLOHType Kind;
104
105  /// Arguments of this directive. Order matters.
106  SmallVector<MCSymbol *, 3> Args;
107
108  /// Emit this directive in \p OutStream using the information available
109  /// in the given \p ObjWriter and \p Layout to get the address of the
110  /// arguments within the object file.
111  void emit_impl(raw_ostream &OutStream, const MachObjectWriter &ObjWriter,
112                 const MCAsmLayout &Layout) const;
113
114public:
115  using LOHArgs = SmallVectorImpl<MCSymbol *>;
116
117  MCLOHDirective(MCLOHType Kind, const LOHArgs &Args)
118      : Kind(Kind), Args(Args.begin(), Args.end()) {
119    assert(isValidMCLOHType(Kind) && "Invalid LOH directive type!");
120  }
121
122  MCLOHType getKind() const { return Kind; }
123
124  const LOHArgs &getArgs() const { return Args; }
125
126  /// Emit this directive as:
127  /// <kind, numArgs, addr1, ..., addrN>
128  void emit(MachObjectWriter &ObjWriter, const MCAsmLayout &Layout) const;
129
130  /// Get the size in bytes of this directive if emitted in \p ObjWriter with
131  /// the given \p Layout.
132  uint64_t getEmitSize(const MachObjectWriter &ObjWriter,
133                       const MCAsmLayout &Layout) const;
134};
135
136class MCLOHContainer {
137  /// Keep track of the emit size of all the LOHs.
138  mutable uint64_t EmitSize = 0;
139
140  /// Keep track of all LOH directives.
141  SmallVector<MCLOHDirective, 32> Directives;
142
143public:
144  using LOHDirectives = SmallVectorImpl<MCLOHDirective>;
145
146  MCLOHContainer() = default;
147
148  /// Const accessor to the directives.
149  const LOHDirectives &getDirectives() const {
150    return Directives;
151  }
152
153  /// Add the directive of the given kind \p Kind with the given arguments
154  /// \p Args to the container.
155  void addDirective(MCLOHType Kind, const MCLOHDirective::LOHArgs &Args) {
156    Directives.push_back(MCLOHDirective(Kind, Args));
157  }
158
159  /// Get the size of the directives if emitted.
160  uint64_t getEmitSize(const MachObjectWriter &ObjWriter,
161                       const MCAsmLayout &Layout) const {
162    if (!EmitSize) {
163      for (const MCLOHDirective &D : Directives)
164        EmitSize += D.getEmitSize(ObjWriter, Layout);
165    }
166    return EmitSize;
167  }
168
169  /// Emit all Linker Optimization Hint in one big table.
170  /// Each line of the table is emitted by LOHDirective::emit.
171  void emit(MachObjectWriter &ObjWriter, const MCAsmLayout &Layout) const {
172    for (const MCLOHDirective &D : Directives)
173      D.emit(ObjWriter, Layout);
174  }
175
176  void reset() {
177    Directives.clear();
178    EmitSize = 0;
179  }
180};
181
182// Add types for specialized template using MCSymbol.
183using MCLOHArgs = MCLOHDirective::LOHArgs;
184using MCLOHDirectives = MCLOHContainer::LOHDirectives;
185
186} // end namespace llvm
187
188#endif // LLVM_MC_MCLINKEROPTIMIZATIONHINT_H
189