1 //===-- llvm/CodeGen/JITCodeEmitter.h - Code emission ----------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
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.).
15 //===----------------------------------------------------------------------===//
17 #ifndef LLVM_CODEGEN_JITCODEEMITTER_H
18 #define LLVM_CODEGEN_JITCODEEMITTER_H
21 #include "llvm/System/DataTypes.h"
22 #include "llvm/Support/MathExtras.h"
23 #include "llvm/CodeGen/MachineCodeEmitter.h"
29 class MachineBasicBlock;
30 class MachineConstantPool;
31 class MachineJumpTableInfo;
32 class MachineFunction;
33 class MachineModuleInfo;
34 class MachineRelocation;
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.
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.
54 class JITCodeEmitter : public MachineCodeEmitter {
56 virtual ~JITCodeEmitter() {}
58 /// startFunction - This callback is invoked when the specified function is
59 /// about to be code generated. This initializes the BufferBegin/End/Ptr
62 virtual void startFunction(MachineFunction &F) = 0;
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
69 virtual bool finishFunction(MachineFunction &F) = 0;
71 /// startGVStub - This callback is invoked when the JIT needs the address of a
72 /// GV (e.g. function) that has not been code generated yet. The StubSize
73 /// specifies the total size required by the stub. The BufferState must be
74 /// passed to finishGVStub, and start/finish pairs with the same BufferState
75 /// must be properly nested.
77 virtual void startGVStub(BufferState &BS, const GlobalValue* GV,
78 unsigned StubSize, unsigned Alignment = 1) = 0;
80 /// startGVStub - This callback is invoked when the JIT needs the address of a
81 /// GV (e.g. function) that has not been code generated yet. Buffer points to
82 /// memory already allocated for this stub. The BufferState must be passed to
83 /// finishGVStub, and start/finish pairs with the same BufferState must be
86 virtual void startGVStub(BufferState &BS, void *Buffer,
87 unsigned StubSize) = 0;
89 /// finishGVStub - This callback is invoked to terminate a GV stub and returns
90 /// the start address of the stub. The BufferState must first have been
91 /// passed to startGVStub.
93 virtual void *finishGVStub(BufferState &BS) = 0;
95 /// emitByte - This callback is invoked when a byte needs to be written to the
98 void emitByte(uint8_t B) {
99 if (CurBufferPtr != BufferEnd)
103 /// emitWordLE - This callback is invoked when a 32-bit word needs to be
104 /// written to the output stream in little-endian format.
106 void emitWordLE(uint32_t W) {
107 if (4 <= BufferEnd-CurBufferPtr) {
108 *CurBufferPtr++ = (uint8_t)(W >> 0);
109 *CurBufferPtr++ = (uint8_t)(W >> 8);
110 *CurBufferPtr++ = (uint8_t)(W >> 16);
111 *CurBufferPtr++ = (uint8_t)(W >> 24);
113 CurBufferPtr = BufferEnd;
117 /// emitWordBE - This callback is invoked when a 32-bit word needs to be
118 /// written to the output stream in big-endian format.
120 void emitWordBE(uint32_t W) {
121 if (4 <= BufferEnd-CurBufferPtr) {
122 *CurBufferPtr++ = (uint8_t)(W >> 24);
123 *CurBufferPtr++ = (uint8_t)(W >> 16);
124 *CurBufferPtr++ = (uint8_t)(W >> 8);
125 *CurBufferPtr++ = (uint8_t)(W >> 0);
127 CurBufferPtr = BufferEnd;
131 /// emitDWordLE - This callback is invoked when a 64-bit word needs to be
132 /// written to the output stream in little-endian format.
134 void emitDWordLE(uint64_t W) {
135 if (8 <= BufferEnd-CurBufferPtr) {
136 *CurBufferPtr++ = (uint8_t)(W >> 0);
137 *CurBufferPtr++ = (uint8_t)(W >> 8);
138 *CurBufferPtr++ = (uint8_t)(W >> 16);
139 *CurBufferPtr++ = (uint8_t)(W >> 24);
140 *CurBufferPtr++ = (uint8_t)(W >> 32);
141 *CurBufferPtr++ = (uint8_t)(W >> 40);
142 *CurBufferPtr++ = (uint8_t)(W >> 48);
143 *CurBufferPtr++ = (uint8_t)(W >> 56);
145 CurBufferPtr = BufferEnd;
149 /// emitDWordBE - This callback is invoked when a 64-bit word needs to be
150 /// written to the output stream in big-endian format.
152 void emitDWordBE(uint64_t W) {
153 if (8 <= BufferEnd-CurBufferPtr) {
154 *CurBufferPtr++ = (uint8_t)(W >> 56);
155 *CurBufferPtr++ = (uint8_t)(W >> 48);
156 *CurBufferPtr++ = (uint8_t)(W >> 40);
157 *CurBufferPtr++ = (uint8_t)(W >> 32);
158 *CurBufferPtr++ = (uint8_t)(W >> 24);
159 *CurBufferPtr++ = (uint8_t)(W >> 16);
160 *CurBufferPtr++ = (uint8_t)(W >> 8);
161 *CurBufferPtr++ = (uint8_t)(W >> 0);
163 CurBufferPtr = BufferEnd;
167 /// emitAlignment - Move the CurBufferPtr pointer up the the specified
168 /// alignment (saturated to BufferEnd of course).
169 void emitAlignment(unsigned Alignment) {
170 if (Alignment == 0) Alignment = 1;
171 uint8_t *NewPtr = (uint8_t*)RoundUpToAlignment((uintptr_t)CurBufferPtr,
173 CurBufferPtr = std::min(NewPtr, BufferEnd);
176 /// emitAlignmentWithFill - Similar to emitAlignment, except that the
177 /// extra bytes are filled with the provided byte.
178 void emitAlignmentWithFill(unsigned Alignment, uint8_t Fill) {
179 if (Alignment == 0) Alignment = 1;
180 uint8_t *NewPtr = (uint8_t*)RoundUpToAlignment((uintptr_t)CurBufferPtr,
182 // Fail if we don't have room.
183 if (NewPtr > BufferEnd) {
184 CurBufferPtr = BufferEnd;
187 while (CurBufferPtr < NewPtr) {
188 *CurBufferPtr++ = Fill;
192 /// emitULEB128Bytes - This callback is invoked when a ULEB128 needs to be
193 /// written to the output stream.
194 void emitULEB128Bytes(uint64_t Value) {
196 uint8_t Byte = Value & 0x7f;
198 if (Value) Byte |= 0x80;
203 /// emitSLEB128Bytes - This callback is invoked when a SLEB128 needs to be
204 /// written to the output stream.
205 void emitSLEB128Bytes(int64_t Value) {
206 int32_t Sign = Value >> (8 * sizeof(Value) - 1);
210 uint8_t Byte = Value & 0x7f;
212 IsMore = Value != Sign || ((Byte ^ Sign) & 0x40) != 0;
213 if (IsMore) Byte |= 0x80;
218 /// emitString - This callback is invoked when a String needs to be
219 /// written to the output stream.
220 void emitString(const std::string &String) {
221 for (unsigned i = 0, N = static_cast<unsigned>(String.size());
223 uint8_t C = String[i];
229 /// emitInt32 - Emit a int32 directive.
230 void emitInt32(uint32_t Value) {
231 if (4 <= BufferEnd-CurBufferPtr) {
232 *((uint32_t*)CurBufferPtr) = Value;
235 CurBufferPtr = BufferEnd;
239 /// emitInt64 - Emit a int64 directive.
240 void emitInt64(uint64_t Value) {
241 if (8 <= BufferEnd-CurBufferPtr) {
242 *((uint64_t*)CurBufferPtr) = Value;
245 CurBufferPtr = BufferEnd;
249 /// emitInt32At - Emit the Int32 Value in Addr.
250 void emitInt32At(uintptr_t *Addr, uintptr_t Value) {
251 if (Addr >= (uintptr_t*)BufferBegin && Addr < (uintptr_t*)BufferEnd)
252 (*(uint32_t*)Addr) = (uint32_t)Value;
255 /// emitInt64At - Emit the Int64 Value in Addr.
256 void emitInt64At(uintptr_t *Addr, uintptr_t Value) {
257 if (Addr >= (uintptr_t*)BufferBegin && Addr < (uintptr_t*)BufferEnd)
258 (*(uint64_t*)Addr) = (uint64_t)Value;
262 /// emitLabel - Emits a label
263 virtual void emitLabel(uint64_t LabelID) = 0;
265 /// allocateSpace - Allocate a block of space in the current output buffer,
266 /// returning null (and setting conditions to indicate buffer overflow) on
267 /// failure. Alignment is the alignment in bytes of the buffer desired.
268 virtual void *allocateSpace(uintptr_t Size, unsigned Alignment) {
269 emitAlignment(Alignment);
272 // Check for buffer overflow.
273 if (Size >= (uintptr_t)(BufferEnd-CurBufferPtr)) {
274 CurBufferPtr = BufferEnd;
277 // Allocate the space.
278 Result = CurBufferPtr;
279 CurBufferPtr += Size;
285 /// allocateGlobal - Allocate memory for a global. Unlike allocateSpace,
286 /// this method does not allocate memory in the current output buffer,
287 /// because a global may live longer than the current function.
288 virtual void *allocateGlobal(uintptr_t Size, unsigned Alignment) = 0;
290 /// StartMachineBasicBlock - This should be called by the target when a new
291 /// basic block is about to be emitted. This way the MCE knows where the
292 /// start of the block is, and can implement getMachineBasicBlockAddress.
293 virtual void StartMachineBasicBlock(MachineBasicBlock *MBB) = 0;
295 /// getCurrentPCValue - This returns the address that the next emitted byte
296 /// will be output to.
298 virtual uintptr_t getCurrentPCValue() const {
299 return (uintptr_t)CurBufferPtr;
302 /// getCurrentPCOffset - Return the offset from the start of the emitted
303 /// buffer that we are currently writing to.
304 uintptr_t getCurrentPCOffset() const {
305 return CurBufferPtr-BufferBegin;
308 /// earlyResolveAddresses - True if the code emitter can use symbol addresses
309 /// during code emission time. The JIT is capable of doing this because it
310 /// creates jump tables or constant pools in memory on the fly while the
311 /// object code emitters rely on a linker to have real addresses and should
312 /// use relocations instead.
313 bool earlyResolveAddresses() const { return true; }
315 /// addRelocation - Whenever a relocatable address is needed, it should be
316 /// noted with this interface.
317 virtual void addRelocation(const MachineRelocation &MR) = 0;
319 /// FIXME: These should all be handled with relocations!
321 /// getConstantPoolEntryAddress - Return the address of the 'Index' entry in
322 /// the constant pool that was last emitted with the emitConstantPool method.
324 virtual uintptr_t getConstantPoolEntryAddress(unsigned Index) const = 0;
326 /// getJumpTableEntryAddress - Return the address of the jump table with index
327 /// 'Index' in the function that last called initJumpTableInfo.
329 virtual uintptr_t getJumpTableEntryAddress(unsigned Index) const = 0;
331 /// getMachineBasicBlockAddress - Return the address of the specified
332 /// MachineBasicBlock, only usable after the label for the MBB has been
335 virtual uintptr_t getMachineBasicBlockAddress(MachineBasicBlock *MBB) const= 0;
337 /// getLabelAddress - Return the address of the specified LabelID, only usable
338 /// after the LabelID has been emitted.
340 virtual uintptr_t getLabelAddress(uint64_t LabelID) const = 0;
342 /// Specifies the MachineModuleInfo object. This is used for exception handling
344 virtual void setModuleInfo(MachineModuleInfo* Info) = 0;
347 } // End llvm namespace