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 
26 namespace llvm {
27 
28 class MachObjectWriter;
29 class MCAsmLayout;
30 class MCSymbol;
31 
32 /// Linker Optimization Hint Type.
33 enum 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 
MCLOHDirectiveName()44 static inline StringRef MCLOHDirectiveName() {
45   return StringRef(".loh");
46 }
47 
isValidMCLOHType(unsigned Kind)48 static inline bool isValidMCLOHType(unsigned Kind) {
49   return Kind >= MCLOH_AdrpAdrp && Kind <= MCLOH_AdrpLdrGot;
50 }
51 
MCLOHNameToId(StringRef Name)52 static 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 
MCLOHIdToName(MCLOHType Kind)67 static 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 
MCLOHIdToNbArgs(MCLOHType Kind)83 static 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).
102 class 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 
114 public:
115   using LOHArgs = SmallVectorImpl<MCSymbol *>;
116 
MCLOHDirective(MCLOHType Kind,const LOHArgs & Args)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 
getKind()122   MCLOHType getKind() const { return Kind; }
123 
getArgs()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 
136 class 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 
143 public:
144   using LOHDirectives = SmallVectorImpl<MCLOHDirective>;
145 
146   MCLOHContainer() = default;
147 
148   /// Const accessor to the directives.
getDirectives()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.
addDirective(MCLOHType Kind,const MCLOHDirective::LOHArgs & Args)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.
getEmitSize(const MachObjectWriter & ObjWriter,const MCAsmLayout & Layout)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.
emit(MachObjectWriter & ObjWriter,const MCAsmLayout & Layout)171   void emit(MachObjectWriter &ObjWriter, const MCAsmLayout &Layout) const {
172     for (const MCLOHDirective &D : Directives)
173       D.emit(ObjWriter, Layout);
174   }
175 
reset()176   void reset() {
177     Directives.clear();
178     EmitSize = 0;
179   }
180 };
181 
182 // Add types for specialized template using MCSymbol.
183 using MCLOHArgs = MCLOHDirective::LOHArgs;
184 using MCLOHDirectives = MCLOHContainer::LOHDirectives;
185 
186 } // end namespace llvm
187 
188 #endif // LLVM_MC_MCLINKEROPTIMIZATIONHINT_H
189