JITCodeEmitter.h revision 8b67f774e9c38b7718b2b300b628388f966df4e0
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/System/DataTypes.h" 22#include "llvm/Support/MathExtras.h" 23#include "llvm/CodeGen/MachineCodeEmitter.h" 24 25using namespace std; 26 27namespace llvm { 28 29class MachineBasicBlock; 30class MachineConstantPool; 31class MachineJumpTableInfo; 32class MachineFunction; 33class MachineModuleInfo; 34class MachineRelocation; 35class Value; 36class GlobalValue; 37class Function; 38 39/// JITCodeEmitter - This class defines two sorts of methods: those for 40/// emitting the actual bytes of machine code, and those for emitting auxillary 41/// structures, such as jump tables, relocations, etc. 42/// 43/// Emission of machine code is complicated by the fact that we don't (in 44/// general) know the size of the machine code that we're about to emit before 45/// we emit it. As such, we preallocate a certain amount of memory, and set the 46/// BufferBegin/BufferEnd pointers to the start and end of the buffer. As we 47/// emit machine instructions, we advance the CurBufferPtr to indicate the 48/// location of the next byte to emit. In the case of a buffer overflow (we 49/// need to emit more machine code than we have allocated space for), the 50/// CurBufferPtr will saturate to BufferEnd and ignore stores. Once the entire 51/// function has been emitted, the overflow condition is checked, and if it has 52/// occurred, more memory is allocated, and we reemit the code into it. 53/// 54class JITCodeEmitter : public MachineCodeEmitter { 55public: 56 virtual ~JITCodeEmitter() {} 57 58 /// startFunction - This callback is invoked when the specified function is 59 /// about to be code generated. This initializes the BufferBegin/End/Ptr 60 /// fields. 61 /// 62 virtual void startFunction(MachineFunction &F) = 0; 63 64 /// finishFunction - This callback is invoked when the specified function has 65 /// finished code generation. If a buffer overflow has occurred, this method 66 /// returns true (the callee is required to try again), otherwise it returns 67 /// false. 68 /// 69 virtual bool finishFunction(MachineFunction &F) = 0; 70 71 /// startGVStub - This callback is invoked when the JIT needs the 72 /// address of a GV (e.g. function) that has not been code generated yet. 73 /// The StubSize specifies the total size required by the stub. 74 /// 75 virtual void startGVStub(const GlobalValue* GV, unsigned StubSize, 76 unsigned Alignment = 1) = 0; 77 78 /// startGVStub - This callback is invoked when the JIT needs the address of a 79 /// GV (e.g. function) that has not been code generated yet. Buffer points to 80 /// memory already allocated for this stub. 81 /// 82 virtual void startGVStub(const GlobalValue* GV, void *Buffer, 83 unsigned StubSize) = 0; 84 85 /// finishGVStub - This callback is invoked to terminate a GV stub. 86 /// 87 virtual void *finishGVStub(const GlobalValue* F) = 0; 88 89 /// emitByte - This callback is invoked when a byte needs to be written to the 90 /// output stream. 91 /// 92 void emitByte(uint8_t B) { 93 if (CurBufferPtr != BufferEnd) 94 *CurBufferPtr++ = B; 95 } 96 97 /// emitWordLE - This callback is invoked when a 32-bit word needs to be 98 /// written to the output stream in little-endian format. 99 /// 100 void emitWordLE(uint32_t W) { 101 if (4 <= BufferEnd-CurBufferPtr) { 102 *CurBufferPtr++ = (uint8_t)(W >> 0); 103 *CurBufferPtr++ = (uint8_t)(W >> 8); 104 *CurBufferPtr++ = (uint8_t)(W >> 16); 105 *CurBufferPtr++ = (uint8_t)(W >> 24); 106 } else { 107 CurBufferPtr = BufferEnd; 108 } 109 } 110 111 /// emitWordBE - This callback is invoked when a 32-bit word needs to be 112 /// written to the output stream in big-endian format. 113 /// 114 void emitWordBE(uint32_t W) { 115 if (4 <= BufferEnd-CurBufferPtr) { 116 *CurBufferPtr++ = (uint8_t)(W >> 24); 117 *CurBufferPtr++ = (uint8_t)(W >> 16); 118 *CurBufferPtr++ = (uint8_t)(W >> 8); 119 *CurBufferPtr++ = (uint8_t)(W >> 0); 120 } else { 121 CurBufferPtr = BufferEnd; 122 } 123 } 124 125 /// emitDWordLE - This callback is invoked when a 64-bit word needs to be 126 /// written to the output stream in little-endian format. 127 /// 128 void emitDWordLE(uint64_t W) { 129 if (8 <= BufferEnd-CurBufferPtr) { 130 *CurBufferPtr++ = (uint8_t)(W >> 0); 131 *CurBufferPtr++ = (uint8_t)(W >> 8); 132 *CurBufferPtr++ = (uint8_t)(W >> 16); 133 *CurBufferPtr++ = (uint8_t)(W >> 24); 134 *CurBufferPtr++ = (uint8_t)(W >> 32); 135 *CurBufferPtr++ = (uint8_t)(W >> 40); 136 *CurBufferPtr++ = (uint8_t)(W >> 48); 137 *CurBufferPtr++ = (uint8_t)(W >> 56); 138 } else { 139 CurBufferPtr = BufferEnd; 140 } 141 } 142 143 /// emitDWordBE - This callback is invoked when a 64-bit word needs to be 144 /// written to the output stream in big-endian format. 145 /// 146 void emitDWordBE(uint64_t W) { 147 if (8 <= BufferEnd-CurBufferPtr) { 148 *CurBufferPtr++ = (uint8_t)(W >> 56); 149 *CurBufferPtr++ = (uint8_t)(W >> 48); 150 *CurBufferPtr++ = (uint8_t)(W >> 40); 151 *CurBufferPtr++ = (uint8_t)(W >> 32); 152 *CurBufferPtr++ = (uint8_t)(W >> 24); 153 *CurBufferPtr++ = (uint8_t)(W >> 16); 154 *CurBufferPtr++ = (uint8_t)(W >> 8); 155 *CurBufferPtr++ = (uint8_t)(W >> 0); 156 } else { 157 CurBufferPtr = BufferEnd; 158 } 159 } 160 161 /// emitAlignment - Move the CurBufferPtr pointer up the the specified 162 /// alignment (saturated to BufferEnd of course). 163 void emitAlignment(unsigned Alignment) { 164 if (Alignment == 0) Alignment = 1; 165 uint8_t *NewPtr = (uint8_t*)RoundUpToAlignment((uintptr_t)CurBufferPtr, 166 Alignment); 167 CurBufferPtr = std::min(NewPtr, BufferEnd); 168 } 169 170 /// emitAlignmentWithFill - Similar to emitAlignment, except that the 171 /// extra bytes are filled with the provided byte. 172 void emitAlignmentWithFill(unsigned Alignment, uint8_t Fill) { 173 if (Alignment == 0) Alignment = 1; 174 uint8_t *NewPtr = (uint8_t*)RoundUpToAlignment((uintptr_t)CurBufferPtr, 175 Alignment); 176 // Fail if we don't have room. 177 if (NewPtr > BufferEnd) { 178 CurBufferPtr = BufferEnd; 179 return; 180 } 181 while (CurBufferPtr < NewPtr) { 182 *CurBufferPtr++ = Fill; 183 } 184 } 185 186 /// emitULEB128Bytes - This callback is invoked when a ULEB128 needs to be 187 /// written to the output stream. 188 void emitULEB128Bytes(uint64_t Value) { 189 do { 190 uint8_t Byte = Value & 0x7f; 191 Value >>= 7; 192 if (Value) Byte |= 0x80; 193 emitByte(Byte); 194 } while (Value); 195 } 196 197 /// emitSLEB128Bytes - This callback is invoked when a SLEB128 needs to be 198 /// written to the output stream. 199 void emitSLEB128Bytes(int64_t Value) { 200 int32_t Sign = Value >> (8 * sizeof(Value) - 1); 201 bool IsMore; 202 203 do { 204 uint8_t Byte = Value & 0x7f; 205 Value >>= 7; 206 IsMore = Value != Sign || ((Byte ^ Sign) & 0x40) != 0; 207 if (IsMore) Byte |= 0x80; 208 emitByte(Byte); 209 } while (IsMore); 210 } 211 212 /// emitString - This callback is invoked when a String needs to be 213 /// written to the output stream. 214 void emitString(const std::string &String) { 215 for (unsigned i = 0, N = static_cast<unsigned>(String.size()); 216 i < N; ++i) { 217 uint8_t C = String[i]; 218 emitByte(C); 219 } 220 emitByte(0); 221 } 222 223 /// emitInt32 - Emit a int32 directive. 224 void emitInt32(uint32_t Value) { 225 if (4 <= BufferEnd-CurBufferPtr) { 226 *((uint32_t*)CurBufferPtr) = Value; 227 CurBufferPtr += 4; 228 } else { 229 CurBufferPtr = BufferEnd; 230 } 231 } 232 233 /// emitInt64 - Emit a int64 directive. 234 void emitInt64(uint64_t Value) { 235 if (8 <= BufferEnd-CurBufferPtr) { 236 *((uint64_t*)CurBufferPtr) = Value; 237 CurBufferPtr += 8; 238 } else { 239 CurBufferPtr = BufferEnd; 240 } 241 } 242 243 /// emitInt32At - Emit the Int32 Value in Addr. 244 void emitInt32At(uintptr_t *Addr, uintptr_t Value) { 245 if (Addr >= (uintptr_t*)BufferBegin && Addr < (uintptr_t*)BufferEnd) 246 (*(uint32_t*)Addr) = (uint32_t)Value; 247 } 248 249 /// emitInt64At - Emit the Int64 Value in Addr. 250 void emitInt64At(uintptr_t *Addr, uintptr_t Value) { 251 if (Addr >= (uintptr_t*)BufferBegin && Addr < (uintptr_t*)BufferEnd) 252 (*(uint64_t*)Addr) = (uint64_t)Value; 253 } 254 255 256 /// emitLabel - Emits a label 257 virtual void emitLabel(uint64_t LabelID) = 0; 258 259 /// allocateSpace - Allocate a block of space in the current output buffer, 260 /// returning null (and setting conditions to indicate buffer overflow) on 261 /// failure. Alignment is the alignment in bytes of the buffer desired. 262 virtual void *allocateSpace(uintptr_t Size, unsigned Alignment) { 263 emitAlignment(Alignment); 264 void *Result; 265 266 // Check for buffer overflow. 267 if (Size >= (uintptr_t)(BufferEnd-CurBufferPtr)) { 268 CurBufferPtr = BufferEnd; 269 Result = 0; 270 } else { 271 // Allocate the space. 272 Result = CurBufferPtr; 273 CurBufferPtr += Size; 274 } 275 276 return Result; 277 } 278 279 /// allocateGlobal - Allocate memory for a global. Unlike allocateSpace, 280 /// this method does not allocate memory in the current output buffer, 281 /// because a global may live longer than the current function. 282 virtual void *allocateGlobal(uintptr_t Size, unsigned Alignment) = 0; 283 284 /// StartMachineBasicBlock - This should be called by the target when a new 285 /// basic block is about to be emitted. This way the MCE knows where the 286 /// start of the block is, and can implement getMachineBasicBlockAddress. 287 virtual void StartMachineBasicBlock(MachineBasicBlock *MBB) = 0; 288 289 /// getCurrentPCValue - This returns the address that the next emitted byte 290 /// will be output to. 291 /// 292 virtual uintptr_t getCurrentPCValue() const { 293 return (uintptr_t)CurBufferPtr; 294 } 295 296 /// getCurrentPCOffset - Return the offset from the start of the emitted 297 /// buffer that we are currently writing to. 298 uintptr_t getCurrentPCOffset() const { 299 return CurBufferPtr-BufferBegin; 300 } 301 302 /// earlyResolveAddresses - True if the code emitter can use symbol addresses 303 /// during code emission time. The JIT is capable of doing this because it 304 /// creates jump tables or constant pools in memory on the fly while the 305 /// object code emitters rely on a linker to have real addresses and should 306 /// use relocations instead. 307 bool earlyResolveAddresses() const { return true; } 308 309 /// addRelocation - Whenever a relocatable address is needed, it should be 310 /// noted with this interface. 311 virtual void addRelocation(const MachineRelocation &MR) = 0; 312 313 /// FIXME: These should all be handled with relocations! 314 315 /// getConstantPoolEntryAddress - Return the address of the 'Index' entry in 316 /// the constant pool that was last emitted with the emitConstantPool method. 317 /// 318 virtual uintptr_t getConstantPoolEntryAddress(unsigned Index) const = 0; 319 320 /// getJumpTableEntryAddress - Return the address of the jump table with index 321 /// 'Index' in the function that last called initJumpTableInfo. 322 /// 323 virtual uintptr_t getJumpTableEntryAddress(unsigned Index) const = 0; 324 325 /// getMachineBasicBlockAddress - Return the address of the specified 326 /// MachineBasicBlock, only usable after the label for the MBB has been 327 /// emitted. 328 /// 329 virtual uintptr_t getMachineBasicBlockAddress(MachineBasicBlock *MBB) const= 0; 330 331 /// getLabelAddress - Return the address of the specified LabelID, only usable 332 /// after the LabelID has been emitted. 333 /// 334 virtual uintptr_t getLabelAddress(uint64_t LabelID) const = 0; 335 336 /// Specifies the MachineModuleInfo object. This is used for exception handling 337 /// purposes. 338 virtual void setModuleInfo(MachineModuleInfo* Info) = 0; 339}; 340 341} // End llvm namespace 342 343#endif 344