LLVM API Documentation
00001 //===-- llvm/CodeGen/MachineRelocation.h - Target Relocation ----*- C++ -*-===// 00002 // 00003 // The LLVM Compiler Infrastructure 00004 // 00005 // This file was developed by the LLVM research group and is distributed under 00006 // the University of Illinois Open Source License. See LICENSE.TXT for details. 00007 // 00008 //===----------------------------------------------------------------------===// 00009 // 00010 // This file defines the MachineRelocation class. 00011 // 00012 //===----------------------------------------------------------------------===// 00013 00014 #ifndef LLVM_CODEGEN_MACHINERELOCATION_H 00015 #define LLVM_CODEGEN_MACHINERELOCATION_H 00016 00017 #include "llvm/Support/DataTypes.h" 00018 #include <cassert> 00019 00020 namespace llvm { 00021 class GlobalValue; 00022 00023 /// MachineRelocation - This represents a target-specific relocation value, 00024 /// produced by the code emitter. This relocation is resolved after the has 00025 /// been emitted, either to an object file or to memory, when the target of the 00026 /// relocation can be resolved. 00027 /// 00028 /// A relocation is made up of the following logical portions: 00029 /// 1. An offset in the machine code buffer, the location to modify. 00030 /// 2. A target specific relocation type (a number from 0 to 63). 00031 /// 3. A symbol being referenced, either as a GlobalValue* or as a string. 00032 /// 4. An optional constant value to be added to the reference. 00033 /// 5. A bit, CanRewrite, which indicates to the JIT that a function stub is 00034 /// not needed for the relocation. 00035 /// 6. An index into the GOT, if the target uses a GOT 00036 /// 00037 class MachineRelocation { 00038 enum AddressType { 00039 isResult, // Relocation has be transformed into its result pointer. 00040 isGV, // The Target.GV field is valid. 00041 isExtSym, // The Target.ExtSym field is valid. 00042 isConstPool, // Relocation of constant pool address. 00043 isJumpTable, // Relocation of jump table address. 00044 isGOTIndex // The Target.GOTIndex field is valid. 00045 }; 00046 00047 /// Offset - This is the offset from the start of the code buffer of the 00048 /// relocation to perform. 00049 intptr_t Offset; 00050 00051 /// ConstantVal - A field that may be used by the target relocation type. 00052 intptr_t ConstantVal; 00053 00054 union { 00055 void *Result; // If this has been resolved to a resolved pointer 00056 GlobalValue *GV; // If this is a pointer to an LLVM global 00057 const char *ExtSym; // If this is a pointer to a named symbol 00058 unsigned Index; // Constant pool / jump table index 00059 unsigned GOTIndex; // Index in the GOT of this symbol/global 00060 } Target; 00061 00062 unsigned TargetReloType : 6; // The target relocation ID. 00063 AddressType AddrType : 3; // The field of Target to use. 00064 bool DoesntNeedFnStub : 1; // True if we don't need a fn stub. 00065 bool GOTRelative : 1; // Should this relocation be relative to the GOT? 00066 00067 public: 00068 /// MachineRelocation::getGV - Return a relocation entry for a GlobalValue. 00069 /// 00070 static MachineRelocation getGV(intptr_t offset, unsigned RelocationType, 00071 GlobalValue *GV, intptr_t cst = 0, 00072 bool DoesntNeedFunctionStub = 0, 00073 bool GOTrelative = 0) { 00074 assert((RelocationType & ~63) == 0 && "Relocation type too large!"); 00075 MachineRelocation Result; 00076 Result.Offset = offset; 00077 Result.ConstantVal = cst; 00078 Result.TargetReloType = RelocationType; 00079 Result.AddrType = isGV; 00080 Result.DoesntNeedFnStub = DoesntNeedFunctionStub; 00081 Result.GOTRelative = GOTrelative; 00082 Result.Target.GV = GV; 00083 return Result; 00084 } 00085 00086 /// MachineRelocation::getExtSym - Return a relocation entry for an external 00087 /// symbol, like "free". 00088 /// 00089 static MachineRelocation getExtSym(intptr_t offset, unsigned RelocationType, 00090 const char *ES, intptr_t cst = 0, 00091 bool GOTrelative = 0) { 00092 assert((RelocationType & ~63) == 0 && "Relocation type too large!"); 00093 MachineRelocation Result; 00094 Result.Offset = offset; 00095 Result.ConstantVal = cst; 00096 Result.TargetReloType = RelocationType; 00097 Result.AddrType = isExtSym; 00098 Result.DoesntNeedFnStub = false; 00099 Result.GOTRelative = GOTrelative; 00100 Result.Target.ExtSym = ES; 00101 return Result; 00102 } 00103 00104 /// MachineRelocation::getConstPool - Return a relocation entry for a constant 00105 /// pool entry. 00106 /// 00107 static MachineRelocation getConstPool(intptr_t offset,unsigned RelocationType, 00108 unsigned CPI, intptr_t cst = 0) { 00109 assert((RelocationType & ~63) == 0 && "Relocation type too large!"); 00110 MachineRelocation Result; 00111 Result.Offset = offset; 00112 Result.ConstantVal = cst; 00113 Result.TargetReloType = RelocationType; 00114 Result.AddrType = isConstPool; 00115 Result.DoesntNeedFnStub = false; 00116 Result.GOTRelative = false; 00117 Result.Target.Index = CPI; 00118 return Result; 00119 } 00120 00121 /// MachineRelocation::getJumpTable - Return a relocation entry for a jump 00122 /// table entry. 00123 /// 00124 static MachineRelocation getJumpTable(intptr_t offset,unsigned RelocationType, 00125 unsigned JTI, intptr_t cst = 0) { 00126 assert((RelocationType & ~63) == 0 && "Relocation type too large!"); 00127 MachineRelocation Result; 00128 Result.Offset = offset; 00129 Result.ConstantVal = cst; 00130 Result.TargetReloType = RelocationType; 00131 Result.AddrType = isJumpTable; 00132 Result.DoesntNeedFnStub = false; 00133 Result.GOTRelative = false; 00134 Result.Target.Index = JTI; 00135 return Result; 00136 } 00137 00138 /// getMachineCodeOffset - Return the offset into the code buffer that the 00139 /// relocation should be performed. 00140 intptr_t getMachineCodeOffset() const { 00141 return Offset; 00142 } 00143 00144 /// getRelocationType - Return the target-specific relocation ID for this 00145 /// relocation. 00146 unsigned getRelocationType() const { 00147 return TargetReloType; 00148 } 00149 00150 /// getConstantVal - Get the constant value associated with this relocation. 00151 /// This is often an offset from the symbol. 00152 /// 00153 intptr_t getConstantVal() const { 00154 return ConstantVal; 00155 } 00156 00157 /// isGlobalValue - Return true if this relocation is a GlobalValue, as 00158 /// opposed to a constant string. 00159 bool isGlobalValue() const { 00160 return AddrType == isGV; 00161 } 00162 00163 /// isString - Return true if this is a constant string. 00164 /// 00165 bool isString() const { 00166 return AddrType == isExtSym; 00167 } 00168 00169 /// isConstantPoolIndex - Return true if this is a constant pool reference. 00170 /// 00171 bool isConstantPoolIndex() const { 00172 return AddrType == isConstPool; 00173 } 00174 00175 /// isJumpTableIndex - Return true if this is a jump table reference. 00176 /// 00177 bool isJumpTableIndex() const { 00178 return AddrType == isJumpTable; 00179 } 00180 00181 /// isGOTRelative - Return true the target wants the index into the GOT of 00182 /// the symbol rather than the address of the symbol. 00183 bool isGOTRelative() const { 00184 return GOTRelative; 00185 } 00186 00187 /// doesntNeedFunctionStub - This function returns true if the JIT for this 00188 /// target is capable of directly handling the relocated instruction without 00189 /// using a stub function. It is always conservatively correct for this flag 00190 /// to be false, but targets can improve their compilation callback functions 00191 /// to handle more general cases if they want improved performance. 00192 bool doesntNeedFunctionStub() const { 00193 return DoesntNeedFnStub; 00194 } 00195 00196 /// getGlobalValue - If this is a global value reference, return the 00197 /// referenced global. 00198 GlobalValue *getGlobalValue() const { 00199 assert(isGlobalValue() && "This is not a global value reference!"); 00200 return Target.GV; 00201 } 00202 00203 /// getString - If this is a string value, return the string reference. 00204 /// 00205 const char *getString() const { 00206 assert(isString() && "This is not a string reference!"); 00207 return Target.ExtSym; 00208 } 00209 00210 /// getConstantPoolIndex - If this is a const pool reference, return 00211 /// the index into the constant pool. 00212 unsigned getConstantPoolIndex() const { 00213 assert(isConstantPoolIndex() && "This is not a constant pool reference!"); 00214 return Target.Index; 00215 } 00216 00217 /// getJumpTableIndex - If this is a jump table reference, return 00218 /// the index into the jump table. 00219 unsigned getJumpTableIndex() const { 00220 assert(isJumpTableIndex() && "This is not a jump table reference!"); 00221 return Target.Index; 00222 } 00223 00224 /// getResultPointer - Once this has been resolved to point to an actual 00225 /// address, this returns the pointer. 00226 void *getResultPointer() const { 00227 assert(AddrType == isResult && "Result pointer isn't set yet!"); 00228 return Target.Result; 00229 } 00230 00231 /// setResultPointer - Set the result to the specified pointer value. 00232 /// 00233 void setResultPointer(void *Ptr) { 00234 Target.Result = Ptr; 00235 AddrType = isResult; 00236 } 00237 00238 /// setGOTIndex - Set the GOT index to a specific value. 00239 void setGOTIndex(unsigned idx) { 00240 AddrType = isGOTIndex; 00241 Target.GOTIndex = idx; 00242 } 00243 00244 /// getGOTIndex - Once this has been resolved to an entry in the GOT, 00245 /// this returns that index. The index is from the lowest address entry 00246 /// in the GOT. 00247 unsigned getGOTIndex() const { 00248 assert(AddrType == isGOTIndex); 00249 return Target.GOTIndex; 00250 } 00251 }; 00252 } 00253 00254 #endif