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1 //===- MCLinkerOptimizationHint.h - LOH interface ---------------*- C++ -*-===//
2 //
3 //
4 //                     The LLVM Compiler Infrastructure
5 //
6 // This file is distributed under the University of Illinois Open Source
7 // License. See LICENSE.TXT for details.
8 //
9 //===----------------------------------------------------------------------===//
10 //
11 // This file declares some helpers classes to handle Linker Optimization Hint
12 // (LOH).
13 //
14 // FIXME: LOH interface supports only MachO format at the moment.
15 //===----------------------------------------------------------------------===//
16 
17 #ifndef LLVM_MC_MCLINKEROPTIMIZATIONHINT_H
18 #define LLVM_MC_MCLINKEROPTIMIZATIONHINT_H
19 
20 #include "llvm/ADT/SmallVector.h"
21 #include "llvm/ADT/StringRef.h"
22 #include "llvm/ADT/StringSwitch.h"
23 #include "llvm/Support/raw_ostream.h"
24 
25 namespace llvm {
26 
27 // Forward declarations.
28 class MCAsmLayout;
29 class MCSymbol;
30 class MachObjectWriter;
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 }
65 
MCLOHIdToName(MCLOHType Kind)66 static inline StringRef MCLOHIdToName(MCLOHType Kind) {
67 #define MCLOHCaseIdToName(Name)      case MCLOH_ ## Name: return StringRef(#Name);
68   switch (Kind) {
69     MCLOHCaseIdToName(AdrpAdrp);
70     MCLOHCaseIdToName(AdrpLdr);
71     MCLOHCaseIdToName(AdrpAddLdr);
72     MCLOHCaseIdToName(AdrpLdrGotLdr);
73     MCLOHCaseIdToName(AdrpAddStr);
74     MCLOHCaseIdToName(AdrpLdrGotStr);
75     MCLOHCaseIdToName(AdrpAdd);
76     MCLOHCaseIdToName(AdrpLdrGot);
77   }
78   return StringRef();
79 }
80 
MCLOHIdToNbArgs(MCLOHType Kind)81 static inline int MCLOHIdToNbArgs(MCLOHType Kind) {
82   switch (Kind) {
83     // LOH with two arguments
84   case MCLOH_AdrpAdrp:
85   case MCLOH_AdrpLdr:
86   case MCLOH_AdrpAdd:
87   case MCLOH_AdrpLdrGot:
88     return 2;
89     // LOH with three arguments
90   case MCLOH_AdrpAddLdr:
91   case MCLOH_AdrpLdrGotLdr:
92   case MCLOH_AdrpAddStr:
93   case MCLOH_AdrpLdrGotStr:
94     return 3;
95   }
96   return -1;
97 }
98 
99 /// Store Linker Optimization Hint information (LOH).
100 class MCLOHDirective {
101   MCLOHType Kind;
102 
103   /// Arguments of this directive. Order matters.
104   SmallVector<MCSymbol *, 3> Args;
105 
106   /// Emit this directive in \p OutStream using the information available
107   /// in the given \p ObjWriter and \p Layout to get the address of the
108   /// arguments within the object file.
109   void emit_impl(raw_ostream &OutStream, const MachObjectWriter &ObjWriter,
110                  const MCAsmLayout &Layout) const;
111 
112 public:
113   typedef SmallVectorImpl<MCSymbol *> LOHArgs;
114 
MCLOHDirective(MCLOHType Kind,const LOHArgs & Args)115   MCLOHDirective(MCLOHType Kind, const LOHArgs &Args)
116       : Kind(Kind), Args(Args.begin(), Args.end()) {
117     assert(isValidMCLOHType(Kind) && "Invalid LOH directive type!");
118   }
119 
getKind()120   MCLOHType getKind() const { return Kind; }
121 
getArgs()122   const LOHArgs &getArgs() const { return Args; }
123 
124   /// Emit this directive as:
125   /// <kind, numArgs, addr1, ..., addrN>
126   void emit(MachObjectWriter &ObjWriter, const MCAsmLayout &Layout) const;
127 
128   /// Get the size in bytes of this directive if emitted in \p ObjWriter with
129   /// the given \p Layout.
130   uint64_t getEmitSize(const MachObjectWriter &ObjWriter,
131                        const MCAsmLayout &Layout) const;
132 };
133 
134 class MCLOHContainer {
135   /// Keep track of the emit size of all the LOHs.
136   mutable uint64_t EmitSize;
137 
138   /// Keep track of all LOH directives.
139   SmallVector<MCLOHDirective, 32> Directives;
140 
141 public:
142   typedef SmallVectorImpl<MCLOHDirective> LOHDirectives;
143 
MCLOHContainer()144   MCLOHContainer() : EmitSize(0) {}
145 
146   /// Const accessor to the directives.
getDirectives()147   const LOHDirectives &getDirectives() const {
148     return Directives;
149   }
150 
151   /// Add the directive of the given kind \p Kind with the given arguments
152   /// \p Args to the container.
addDirective(MCLOHType Kind,const MCLOHDirective::LOHArgs & Args)153   void addDirective(MCLOHType Kind, const MCLOHDirective::LOHArgs &Args) {
154     Directives.push_back(MCLOHDirective(Kind, Args));
155   }
156 
157   /// Get the size of the directives if emitted.
getEmitSize(const MachObjectWriter & ObjWriter,const MCAsmLayout & Layout)158   uint64_t getEmitSize(const MachObjectWriter &ObjWriter,
159                        const MCAsmLayout &Layout) const {
160     if (!EmitSize) {
161       for (const MCLOHDirective &D : Directives)
162         EmitSize += D.getEmitSize(ObjWriter, Layout);
163     }
164     return EmitSize;
165   }
166 
167   /// Emit all Linker Optimization Hint in one big table.
168   /// Each line of the table is emitted by LOHDirective::emit.
emit(MachObjectWriter & ObjWriter,const MCAsmLayout & Layout)169   void emit(MachObjectWriter &ObjWriter, const MCAsmLayout &Layout) const {
170     for (const MCLOHDirective &D : Directives)
171       D.emit(ObjWriter, Layout);
172   }
173 
reset()174   void reset() {
175     Directives.clear();
176     EmitSize = 0;
177   }
178 };
179 
180 // Add types for specialized template using MCSymbol.
181 typedef MCLOHDirective::LOHArgs MCLOHArgs;
182 typedef MCLOHContainer::LOHDirectives MCLOHDirectives;
183 
184 } // end namespace llvm
185 
186 #endif
187