JITCodeEmitter.h revision f451cb870efcf9e0302d25ed05f4cac6bb494e42
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 /// allocIndirectGV - Allocates and fills storage for an indirect 72 /// GlobalValue, and returns the address. 73 virtual void *allocIndirectGV(const GlobalValue *GV, 74 const uint8_t *Buffer, size_t Size, 75 unsigned Alignment) = 0; 76 77 /// emitByte - This callback is invoked when a byte needs to be written to the 78 /// output stream. 79 /// 80 void emitByte(uint8_t B) { 81 if (CurBufferPtr != BufferEnd) 82 *CurBufferPtr++ = B; 83 } 84 85 /// emitWordLE - This callback is invoked when a 32-bit word needs to be 86 /// written to the output stream in little-endian format. 87 /// 88 void emitWordLE(uint32_t W) { 89 if (4 <= BufferEnd-CurBufferPtr) { 90 *CurBufferPtr++ = (uint8_t)(W >> 0); 91 *CurBufferPtr++ = (uint8_t)(W >> 8); 92 *CurBufferPtr++ = (uint8_t)(W >> 16); 93 *CurBufferPtr++ = (uint8_t)(W >> 24); 94 } else { 95 CurBufferPtr = BufferEnd; 96 } 97 } 98 99 /// emitWordBE - This callback is invoked when a 32-bit word needs to be 100 /// written to the output stream in big-endian format. 101 /// 102 void emitWordBE(uint32_t W) { 103 if (4 <= BufferEnd-CurBufferPtr) { 104 *CurBufferPtr++ = (uint8_t)(W >> 24); 105 *CurBufferPtr++ = (uint8_t)(W >> 16); 106 *CurBufferPtr++ = (uint8_t)(W >> 8); 107 *CurBufferPtr++ = (uint8_t)(W >> 0); 108 } else { 109 CurBufferPtr = BufferEnd; 110 } 111 } 112 113 /// emitDWordLE - This callback is invoked when a 64-bit word needs to be 114 /// written to the output stream in little-endian format. 115 /// 116 void emitDWordLE(uint64_t W) { 117 if (8 <= BufferEnd-CurBufferPtr) { 118 *CurBufferPtr++ = (uint8_t)(W >> 0); 119 *CurBufferPtr++ = (uint8_t)(W >> 8); 120 *CurBufferPtr++ = (uint8_t)(W >> 16); 121 *CurBufferPtr++ = (uint8_t)(W >> 24); 122 *CurBufferPtr++ = (uint8_t)(W >> 32); 123 *CurBufferPtr++ = (uint8_t)(W >> 40); 124 *CurBufferPtr++ = (uint8_t)(W >> 48); 125 *CurBufferPtr++ = (uint8_t)(W >> 56); 126 } else { 127 CurBufferPtr = BufferEnd; 128 } 129 } 130 131 /// emitDWordBE - This callback is invoked when a 64-bit word needs to be 132 /// written to the output stream in big-endian format. 133 /// 134 void emitDWordBE(uint64_t W) { 135 if (8 <= BufferEnd-CurBufferPtr) { 136 *CurBufferPtr++ = (uint8_t)(W >> 56); 137 *CurBufferPtr++ = (uint8_t)(W >> 48); 138 *CurBufferPtr++ = (uint8_t)(W >> 40); 139 *CurBufferPtr++ = (uint8_t)(W >> 32); 140 *CurBufferPtr++ = (uint8_t)(W >> 24); 141 *CurBufferPtr++ = (uint8_t)(W >> 16); 142 *CurBufferPtr++ = (uint8_t)(W >> 8); 143 *CurBufferPtr++ = (uint8_t)(W >> 0); 144 } else { 145 CurBufferPtr = BufferEnd; 146 } 147 } 148 149 /// emitAlignment - Move the CurBufferPtr pointer up the specified 150 /// alignment (saturated to BufferEnd of course). 151 void emitAlignment(unsigned Alignment) { 152 if (Alignment == 0) Alignment = 1; 153 uint8_t *NewPtr = (uint8_t*)RoundUpToAlignment((uintptr_t)CurBufferPtr, 154 Alignment); 155 CurBufferPtr = std::min(NewPtr, BufferEnd); 156 } 157 158 /// emitAlignmentWithFill - Similar to emitAlignment, except that the 159 /// extra bytes are filled with the provided byte. 160 void emitAlignmentWithFill(unsigned Alignment, uint8_t Fill) { 161 if (Alignment == 0) Alignment = 1; 162 uint8_t *NewPtr = (uint8_t*)RoundUpToAlignment((uintptr_t)CurBufferPtr, 163 Alignment); 164 // Fail if we don't have room. 165 if (NewPtr > BufferEnd) { 166 CurBufferPtr = BufferEnd; 167 return; 168 } 169 while (CurBufferPtr < NewPtr) { 170 *CurBufferPtr++ = Fill; 171 } 172 } 173 174 /// emitULEB128Bytes - This callback is invoked when a ULEB128 needs to be 175 /// written to the output stream. 176 void emitULEB128Bytes(uint64_t Value) { 177 do { 178 uint8_t Byte = Value & 0x7f; 179 Value >>= 7; 180 if (Value) Byte |= 0x80; 181 emitByte(Byte); 182 } while (Value); 183 } 184 185 /// emitSLEB128Bytes - This callback is invoked when a SLEB128 needs to be 186 /// written to the output stream. 187 void emitSLEB128Bytes(int64_t Value) { 188 int32_t Sign = Value >> (8 * sizeof(Value) - 1); 189 bool IsMore; 190 191 do { 192 uint8_t Byte = Value & 0x7f; 193 Value >>= 7; 194 IsMore = Value != Sign || ((Byte ^ Sign) & 0x40) != 0; 195 if (IsMore) Byte |= 0x80; 196 emitByte(Byte); 197 } while (IsMore); 198 } 199 200 /// emitString - This callback is invoked when a String needs to be 201 /// written to the output stream. 202 void emitString(const std::string &String) { 203 for (unsigned i = 0, N = static_cast<unsigned>(String.size()); 204 i < N; ++i) { 205 uint8_t C = String[i]; 206 emitByte(C); 207 } 208 emitByte(0); 209 } 210 211 /// emitInt32 - Emit a int32 directive. 212 void emitInt32(uint32_t Value) { 213 if (4 <= BufferEnd-CurBufferPtr) { 214 *((uint32_t*)CurBufferPtr) = Value; 215 CurBufferPtr += 4; 216 } else { 217 CurBufferPtr = BufferEnd; 218 } 219 } 220 221 /// emitInt64 - Emit a int64 directive. 222 void emitInt64(uint64_t Value) { 223 if (8 <= BufferEnd-CurBufferPtr) { 224 *((uint64_t*)CurBufferPtr) = Value; 225 CurBufferPtr += 8; 226 } else { 227 CurBufferPtr = BufferEnd; 228 } 229 } 230 231 /// emitInt32At - Emit the Int32 Value in Addr. 232 void emitInt32At(uintptr_t *Addr, uintptr_t Value) { 233 if (Addr >= (uintptr_t*)BufferBegin && Addr < (uintptr_t*)BufferEnd) 234 (*(uint32_t*)Addr) = (uint32_t)Value; 235 } 236 237 /// emitInt64At - Emit the Int64 Value in Addr. 238 void emitInt64At(uintptr_t *Addr, uintptr_t Value) { 239 if (Addr >= (uintptr_t*)BufferBegin && Addr < (uintptr_t*)BufferEnd) 240 (*(uint64_t*)Addr) = (uint64_t)Value; 241 } 242 243 244 /// emitLabel - Emits a label 245 virtual void emitLabel(uint64_t LabelID) = 0; 246 247 /// allocateSpace - Allocate a block of space in the current output buffer, 248 /// returning null (and setting conditions to indicate buffer overflow) on 249 /// failure. Alignment is the alignment in bytes of the buffer desired. 250 virtual void *allocateSpace(uintptr_t Size, unsigned Alignment) { 251 emitAlignment(Alignment); 252 void *Result; 253 254 // Check for buffer overflow. 255 if (Size >= (uintptr_t)(BufferEnd-CurBufferPtr)) { 256 CurBufferPtr = BufferEnd; 257 Result = 0; 258 } else { 259 // Allocate the space. 260 Result = CurBufferPtr; 261 CurBufferPtr += Size; 262 } 263 264 return Result; 265 } 266 267 /// allocateGlobal - Allocate memory for a global. Unlike allocateSpace, 268 /// this method does not allocate memory in the current output buffer, 269 /// because a global may live longer than the current function. 270 virtual void *allocateGlobal(uintptr_t Size, unsigned Alignment) = 0; 271 272 /// StartMachineBasicBlock - This should be called by the target when a new 273 /// basic block is about to be emitted. This way the MCE knows where the 274 /// start of the block is, and can implement getMachineBasicBlockAddress. 275 virtual void StartMachineBasicBlock(MachineBasicBlock *MBB) = 0; 276 277 /// getCurrentPCValue - This returns the address that the next emitted byte 278 /// will be output to. 279 /// 280 virtual uintptr_t getCurrentPCValue() const { 281 return (uintptr_t)CurBufferPtr; 282 } 283 284 /// getCurrentPCOffset - Return the offset from the start of the emitted 285 /// buffer that we are currently writing to. 286 uintptr_t getCurrentPCOffset() const { 287 return CurBufferPtr-BufferBegin; 288 } 289 290 /// earlyResolveAddresses - True if the code emitter can use symbol addresses 291 /// during code emission time. The JIT is capable of doing this because it 292 /// creates jump tables or constant pools in memory on the fly while the 293 /// object code emitters rely on a linker to have real addresses and should 294 /// use relocations instead. 295 bool earlyResolveAddresses() const { return true; } 296 297 /// addRelocation - Whenever a relocatable address is needed, it should be 298 /// noted with this interface. 299 virtual void addRelocation(const MachineRelocation &MR) = 0; 300 301 /// FIXME: These should all be handled with relocations! 302 303 /// getConstantPoolEntryAddress - Return the address of the 'Index' entry in 304 /// the constant pool that was last emitted with the emitConstantPool method. 305 /// 306 virtual uintptr_t getConstantPoolEntryAddress(unsigned Index) const = 0; 307 308 /// getJumpTableEntryAddress - Return the address of the jump table with index 309 /// 'Index' in the function that last called initJumpTableInfo. 310 /// 311 virtual uintptr_t getJumpTableEntryAddress(unsigned Index) const = 0; 312 313 /// getMachineBasicBlockAddress - Return the address of the specified 314 /// MachineBasicBlock, only usable after the label for the MBB has been 315 /// emitted. 316 /// 317 virtual uintptr_t getMachineBasicBlockAddress(MachineBasicBlock *MBB) const= 0; 318 319 /// getLabelAddress - Return the address of the specified LabelID, only usable 320 /// after the LabelID has been emitted. 321 /// 322 virtual uintptr_t getLabelAddress(uint64_t LabelID) const = 0; 323 324 /// Specifies the MachineModuleInfo object. This is used for exception handling 325 /// purposes. 326 virtual void setModuleInfo(MachineModuleInfo* Info) = 0; 327}; 328 329} // End llvm namespace 330 331#endif 332