1 //===-- llvm/CodeGen/JITCodeEmitter.h - Code emission ----------*- C++ -*-===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file defines an abstract interface that is used by the machine code 11 // emission framework to output the code. This allows machine code emission to 12 // be separated from concerns such as resolution of call targets, and where the 13 // machine code will be written (memory or disk, f.e.). 14 // 15 //===----------------------------------------------------------------------===// 16 17 #ifndef LLVM_CODEGEN_JITCODEEMITTER_H 18 #define LLVM_CODEGEN_JITCODEEMITTER_H 19 20 #include <string> 21 #include "llvm/Support/DataTypes.h" 22 #include "llvm/Support/MathExtras.h" 23 #include "llvm/CodeGen/MachineCodeEmitter.h" 24 #include "llvm/ADT/DenseMap.h" 25 26 namespace llvm { 27 28 class MachineBasicBlock; 29 class MachineConstantPool; 30 class MachineJumpTableInfo; 31 class MachineFunction; 32 class MachineModuleInfo; 33 class MachineRelocation; 34 class Value; 35 class GlobalValue; 36 class Function; 37 38 /// JITCodeEmitter - This class defines two sorts of methods: those for 39 /// emitting the actual bytes of machine code, and those for emitting auxiliary 40 /// structures, such as jump tables, relocations, etc. 41 /// 42 /// Emission of machine code is complicated by the fact that we don't (in 43 /// general) know the size of the machine code that we're about to emit before 44 /// we emit it. As such, we preallocate a certain amount of memory, and set the 45 /// BufferBegin/BufferEnd pointers to the start and end of the buffer. As we 46 /// emit machine instructions, we advance the CurBufferPtr to indicate the 47 /// location of the next byte to emit. In the case of a buffer overflow (we 48 /// need to emit more machine code than we have allocated space for), the 49 /// CurBufferPtr will saturate to BufferEnd and ignore stores. Once the entire 50 /// function has been emitted, the overflow condition is checked, and if it has 51 /// occurred, more memory is allocated, and we reemit the code into it. 52 /// 53 class JITCodeEmitter : public MachineCodeEmitter { 54 public: 55 virtual ~JITCodeEmitter() {} 56 57 /// startFunction - This callback is invoked when the specified function is 58 /// about to be code generated. This initializes the BufferBegin/End/Ptr 59 /// fields. 60 /// 61 virtual void startFunction(MachineFunction &F) = 0; 62 63 /// finishFunction - This callback is invoked when the specified function has 64 /// finished code generation. If a buffer overflow has occurred, this method 65 /// returns true (the callee is required to try again), otherwise it returns 66 /// false. 67 /// 68 virtual bool finishFunction(MachineFunction &F) = 0; 69 70 /// allocIndirectGV - Allocates and fills storage for an indirect 71 /// GlobalValue, and returns the address. 72 virtual void *allocIndirectGV(const GlobalValue *GV, 73 const uint8_t *Buffer, size_t Size, 74 unsigned Alignment) = 0; 75 76 /// emitByte - This callback is invoked when a byte needs to be written to the 77 /// output stream. 78 /// 79 void emitByte(uint8_t B) { 80 if (CurBufferPtr != BufferEnd) 81 *CurBufferPtr++ = B; 82 } 83 84 /// emitWordLE - This callback is invoked when a 32-bit word needs to be 85 /// written to the output stream in little-endian format. 86 /// 87 void emitWordLE(uint32_t W) { 88 if (4 <= BufferEnd-CurBufferPtr) { 89 *CurBufferPtr++ = (uint8_t)(W >> 0); 90 *CurBufferPtr++ = (uint8_t)(W >> 8); 91 *CurBufferPtr++ = (uint8_t)(W >> 16); 92 *CurBufferPtr++ = (uint8_t)(W >> 24); 93 } else { 94 CurBufferPtr = BufferEnd; 95 } 96 } 97 98 /// emitWordBE - This callback is invoked when a 32-bit word needs to be 99 /// written to the output stream in big-endian format. 100 /// 101 void emitWordBE(uint32_t W) { 102 if (4 <= BufferEnd-CurBufferPtr) { 103 *CurBufferPtr++ = (uint8_t)(W >> 24); 104 *CurBufferPtr++ = (uint8_t)(W >> 16); 105 *CurBufferPtr++ = (uint8_t)(W >> 8); 106 *CurBufferPtr++ = (uint8_t)(W >> 0); 107 } else { 108 CurBufferPtr = BufferEnd; 109 } 110 } 111 112 /// emitDWordLE - This callback is invoked when a 64-bit word needs to be 113 /// written to the output stream in little-endian format. 114 /// 115 void emitDWordLE(uint64_t W) { 116 if (8 <= BufferEnd-CurBufferPtr) { 117 *CurBufferPtr++ = (uint8_t)(W >> 0); 118 *CurBufferPtr++ = (uint8_t)(W >> 8); 119 *CurBufferPtr++ = (uint8_t)(W >> 16); 120 *CurBufferPtr++ = (uint8_t)(W >> 24); 121 *CurBufferPtr++ = (uint8_t)(W >> 32); 122 *CurBufferPtr++ = (uint8_t)(W >> 40); 123 *CurBufferPtr++ = (uint8_t)(W >> 48); 124 *CurBufferPtr++ = (uint8_t)(W >> 56); 125 } else { 126 CurBufferPtr = BufferEnd; 127 } 128 } 129 130 /// emitDWordBE - This callback is invoked when a 64-bit word needs to be 131 /// written to the output stream in big-endian format. 132 /// 133 void emitDWordBE(uint64_t W) { 134 if (8 <= BufferEnd-CurBufferPtr) { 135 *CurBufferPtr++ = (uint8_t)(W >> 56); 136 *CurBufferPtr++ = (uint8_t)(W >> 48); 137 *CurBufferPtr++ = (uint8_t)(W >> 40); 138 *CurBufferPtr++ = (uint8_t)(W >> 32); 139 *CurBufferPtr++ = (uint8_t)(W >> 24); 140 *CurBufferPtr++ = (uint8_t)(W >> 16); 141 *CurBufferPtr++ = (uint8_t)(W >> 8); 142 *CurBufferPtr++ = (uint8_t)(W >> 0); 143 } else { 144 CurBufferPtr = BufferEnd; 145 } 146 } 147 148 /// emitAlignment - Move the CurBufferPtr pointer up to the specified 149 /// alignment (saturated to BufferEnd of course). 150 void emitAlignment(unsigned Alignment) { 151 if (Alignment == 0) Alignment = 1; 152 uint8_t *NewPtr = (uint8_t*)RoundUpToAlignment((uintptr_t)CurBufferPtr, 153 Alignment); 154 CurBufferPtr = std::min(NewPtr, BufferEnd); 155 } 156 157 /// emitAlignmentWithFill - Similar to emitAlignment, except that the 158 /// extra bytes are filled with the provided byte. 159 void emitAlignmentWithFill(unsigned Alignment, uint8_t Fill) { 160 if (Alignment == 0) Alignment = 1; 161 uint8_t *NewPtr = (uint8_t*)RoundUpToAlignment((uintptr_t)CurBufferPtr, 162 Alignment); 163 // Fail if we don't have room. 164 if (NewPtr > BufferEnd) { 165 CurBufferPtr = BufferEnd; 166 return; 167 } 168 while (CurBufferPtr < NewPtr) { 169 *CurBufferPtr++ = Fill; 170 } 171 } 172 173 /// emitULEB128Bytes - This callback is invoked when a ULEB128 needs to be 174 /// written to the output stream. 175 void emitULEB128Bytes(uint64_t Value, unsigned PadTo = 0) { 176 do { 177 uint8_t Byte = Value & 0x7f; 178 Value >>= 7; 179 if (Value || PadTo != 0) Byte |= 0x80; 180 emitByte(Byte); 181 } while (Value); 182 183 if (PadTo) { 184 do { 185 uint8_t Byte = (PadTo > 1) ? 0x80 : 0x0; 186 emitByte(Byte); 187 } while (--PadTo); 188 } 189 } 190 191 /// emitSLEB128Bytes - This callback is invoked when a SLEB128 needs to be 192 /// written to the output stream. 193 void emitSLEB128Bytes(int64_t Value) { 194 int32_t Sign = Value >> (8 * sizeof(Value) - 1); 195 bool IsMore; 196 197 do { 198 uint8_t Byte = Value & 0x7f; 199 Value >>= 7; 200 IsMore = Value != Sign || ((Byte ^ Sign) & 0x40) != 0; 201 if (IsMore) Byte |= 0x80; 202 emitByte(Byte); 203 } while (IsMore); 204 } 205 206 /// emitString - This callback is invoked when a String needs to be 207 /// written to the output stream. 208 void emitString(const std::string &String) { 209 for (unsigned i = 0, N = static_cast<unsigned>(String.size()); 210 i < N; ++i) { 211 uint8_t C = String[i]; 212 emitByte(C); 213 } 214 emitByte(0); 215 } 216 217 /// emitInt32 - Emit a int32 directive. 218 void emitInt32(uint32_t Value) { 219 if (4 <= BufferEnd-CurBufferPtr) { 220 *((uint32_t*)CurBufferPtr) = Value; 221 CurBufferPtr += 4; 222 } else { 223 CurBufferPtr = BufferEnd; 224 } 225 } 226 227 /// emitInt64 - Emit a int64 directive. 228 void emitInt64(uint64_t Value) { 229 if (8 <= BufferEnd-CurBufferPtr) { 230 *((uint64_t*)CurBufferPtr) = Value; 231 CurBufferPtr += 8; 232 } else { 233 CurBufferPtr = BufferEnd; 234 } 235 } 236 237 /// emitInt32At - Emit the Int32 Value in Addr. 238 void emitInt32At(uintptr_t *Addr, uintptr_t Value) { 239 if (Addr >= (uintptr_t*)BufferBegin && Addr < (uintptr_t*)BufferEnd) 240 (*(uint32_t*)Addr) = (uint32_t)Value; 241 } 242 243 /// emitInt64At - Emit the Int64 Value in Addr. 244 void emitInt64At(uintptr_t *Addr, uintptr_t Value) { 245 if (Addr >= (uintptr_t*)BufferBegin && Addr < (uintptr_t*)BufferEnd) 246 (*(uint64_t*)Addr) = (uint64_t)Value; 247 } 248 249 250 /// emitLabel - Emits a label 251 virtual void emitLabel(MCSymbol *Label) = 0; 252 253 /// allocateSpace - Allocate a block of space in the current output buffer, 254 /// returning null (and setting conditions to indicate buffer overflow) on 255 /// failure. Alignment is the alignment in bytes of the buffer desired. 256 virtual void *allocateSpace(uintptr_t Size, unsigned Alignment) { 257 emitAlignment(Alignment); 258 void *Result; 259 260 // Check for buffer overflow. 261 if (Size >= (uintptr_t)(BufferEnd-CurBufferPtr)) { 262 CurBufferPtr = BufferEnd; 263 Result = 0; 264 } else { 265 // Allocate the space. 266 Result = CurBufferPtr; 267 CurBufferPtr += Size; 268 } 269 270 return Result; 271 } 272 273 /// allocateGlobal - Allocate memory for a global. Unlike allocateSpace, 274 /// this method does not allocate memory in the current output buffer, 275 /// because a global may live longer than the current function. 276 virtual void *allocateGlobal(uintptr_t Size, unsigned Alignment) = 0; 277 278 /// StartMachineBasicBlock - This should be called by the target when a new 279 /// basic block is about to be emitted. This way the MCE knows where the 280 /// start of the block is, and can implement getMachineBasicBlockAddress. 281 virtual void StartMachineBasicBlock(MachineBasicBlock *MBB) = 0; 282 283 /// getCurrentPCValue - This returns the address that the next emitted byte 284 /// will be output to. 285 /// 286 virtual uintptr_t getCurrentPCValue() const { 287 return (uintptr_t)CurBufferPtr; 288 } 289 290 /// getCurrentPCOffset - Return the offset from the start of the emitted 291 /// buffer that we are currently writing to. 292 uintptr_t getCurrentPCOffset() const { 293 return CurBufferPtr-BufferBegin; 294 } 295 296 /// earlyResolveAddresses - True if the code emitter can use symbol addresses 297 /// during code emission time. The JIT is capable of doing this because it 298 /// creates jump tables or constant pools in memory on the fly while the 299 /// object code emitters rely on a linker to have real addresses and should 300 /// use relocations instead. 301 bool earlyResolveAddresses() const { return true; } 302 303 /// addRelocation - Whenever a relocatable address is needed, it should be 304 /// noted with this interface. 305 virtual void addRelocation(const MachineRelocation &MR) = 0; 306 307 /// FIXME: These should all be handled with relocations! 308 309 /// getConstantPoolEntryAddress - Return the address of the 'Index' entry in 310 /// the constant pool that was last emitted with the emitConstantPool method. 311 /// 312 virtual uintptr_t getConstantPoolEntryAddress(unsigned Index) const = 0; 313 314 /// getJumpTableEntryAddress - Return the address of the jump table with index 315 /// 'Index' in the function that last called initJumpTableInfo. 316 /// 317 virtual uintptr_t getJumpTableEntryAddress(unsigned Index) const = 0; 318 319 /// getMachineBasicBlockAddress - Return the address of the specified 320 /// MachineBasicBlock, only usable after the label for the MBB has been 321 /// emitted. 322 /// 323 virtual uintptr_t getMachineBasicBlockAddress(MachineBasicBlock *MBB) const= 0; 324 325 /// getLabelAddress - Return the address of the specified Label, only usable 326 /// after the Label has been emitted. 327 /// 328 virtual uintptr_t getLabelAddress(MCSymbol *Label) const = 0; 329 330 /// Specifies the MachineModuleInfo object. This is used for exception handling 331 /// purposes. 332 virtual void setModuleInfo(MachineModuleInfo* Info) = 0; 333 334 /// getLabelLocations - Return the label locations map of the label IDs to 335 /// their address. 336 virtual DenseMap<MCSymbol*, uintptr_t> *getLabelLocations() { return 0; } 337 }; 338 339 } // End llvm namespace 340 341 #endif 342
