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"
24 #include "llvm/ADT/DenseMap.h"
30 class MachineBasicBlock;
31 class MachineConstantPool;
32 class MachineJumpTableInfo;
33 class MachineFunction;
34 class MachineModuleInfo;
35 class MachineRelocation;
40 /// JITCodeEmitter - This class defines two sorts of methods: those for
41 /// emitting the actual bytes of machine code, and those for emitting auxillary
42 /// structures, such as jump tables, relocations, etc.
44 /// Emission of machine code is complicated by the fact that we don't (in
45 /// general) know the size of the machine code that we're about to emit before
46 /// we emit it. As such, we preallocate a certain amount of memory, and set the
47 /// BufferBegin/BufferEnd pointers to the start and end of the buffer. As we
48 /// emit machine instructions, we advance the CurBufferPtr to indicate the
49 /// location of the next byte to emit. In the case of a buffer overflow (we
50 /// need to emit more machine code than we have allocated space for), the
51 /// CurBufferPtr will saturate to BufferEnd and ignore stores. Once the entire
52 /// function has been emitted, the overflow condition is checked, and if it has
53 /// occurred, more memory is allocated, and we reemit the code into it.
55 class JITCodeEmitter : public MachineCodeEmitter {
57 virtual ~JITCodeEmitter() {}
59 /// startFunction - This callback is invoked when the specified function is
60 /// about to be code generated. This initializes the BufferBegin/End/Ptr
63 virtual void startFunction(MachineFunction &F) = 0;
65 /// finishFunction - This callback is invoked when the specified function has
66 /// finished code generation. If a buffer overflow has occurred, this method
67 /// returns true (the callee is required to try again), otherwise it returns
70 virtual bool finishFunction(MachineFunction &F) = 0;
72 /// allocIndirectGV - Allocates and fills storage for an indirect
73 /// GlobalValue, and returns the address.
74 virtual void *allocIndirectGV(const GlobalValue *GV,
75 const uint8_t *Buffer, size_t Size,
76 unsigned Alignment) = 0;
78 /// emitByte - This callback is invoked when a byte needs to be written to the
81 void emitByte(uint8_t B) {
82 if (CurBufferPtr != BufferEnd)
86 /// emitWordLE - This callback is invoked when a 32-bit word needs to be
87 /// written to the output stream in little-endian format.
89 void emitWordLE(uint32_t W) {
90 if (4 <= BufferEnd-CurBufferPtr) {
91 *CurBufferPtr++ = (uint8_t)(W >> 0);
92 *CurBufferPtr++ = (uint8_t)(W >> 8);
93 *CurBufferPtr++ = (uint8_t)(W >> 16);
94 *CurBufferPtr++ = (uint8_t)(W >> 24);
96 CurBufferPtr = BufferEnd;
100 /// emitWordBE - This callback is invoked when a 32-bit word needs to be
101 /// written to the output stream in big-endian format.
103 void emitWordBE(uint32_t W) {
104 if (4 <= BufferEnd-CurBufferPtr) {
105 *CurBufferPtr++ = (uint8_t)(W >> 24);
106 *CurBufferPtr++ = (uint8_t)(W >> 16);
107 *CurBufferPtr++ = (uint8_t)(W >> 8);
108 *CurBufferPtr++ = (uint8_t)(W >> 0);
110 CurBufferPtr = BufferEnd;
114 /// emitDWordLE - This callback is invoked when a 64-bit word needs to be
115 /// written to the output stream in little-endian format.
117 void emitDWordLE(uint64_t W) {
118 if (8 <= BufferEnd-CurBufferPtr) {
119 *CurBufferPtr++ = (uint8_t)(W >> 0);
120 *CurBufferPtr++ = (uint8_t)(W >> 8);
121 *CurBufferPtr++ = (uint8_t)(W >> 16);
122 *CurBufferPtr++ = (uint8_t)(W >> 24);
123 *CurBufferPtr++ = (uint8_t)(W >> 32);
124 *CurBufferPtr++ = (uint8_t)(W >> 40);
125 *CurBufferPtr++ = (uint8_t)(W >> 48);
126 *CurBufferPtr++ = (uint8_t)(W >> 56);
128 CurBufferPtr = BufferEnd;
132 /// emitDWordBE - This callback is invoked when a 64-bit word needs to be
133 /// written to the output stream in big-endian format.
135 void emitDWordBE(uint64_t W) {
136 if (8 <= BufferEnd-CurBufferPtr) {
137 *CurBufferPtr++ = (uint8_t)(W >> 56);
138 *CurBufferPtr++ = (uint8_t)(W >> 48);
139 *CurBufferPtr++ = (uint8_t)(W >> 40);
140 *CurBufferPtr++ = (uint8_t)(W >> 32);
141 *CurBufferPtr++ = (uint8_t)(W >> 24);
142 *CurBufferPtr++ = (uint8_t)(W >> 16);
143 *CurBufferPtr++ = (uint8_t)(W >> 8);
144 *CurBufferPtr++ = (uint8_t)(W >> 0);
146 CurBufferPtr = BufferEnd;
150 /// emitAlignment - Move the CurBufferPtr pointer up to the specified
151 /// alignment (saturated to BufferEnd of course).
152 void emitAlignment(unsigned Alignment) {
153 if (Alignment == 0) Alignment = 1;
154 uint8_t *NewPtr = (uint8_t*)RoundUpToAlignment((uintptr_t)CurBufferPtr,
156 CurBufferPtr = std::min(NewPtr, BufferEnd);
159 /// emitAlignmentWithFill - Similar to emitAlignment, except that the
160 /// extra bytes are filled with the provided byte.
161 void emitAlignmentWithFill(unsigned Alignment, uint8_t Fill) {
162 if (Alignment == 0) Alignment = 1;
163 uint8_t *NewPtr = (uint8_t*)RoundUpToAlignment((uintptr_t)CurBufferPtr,
165 // Fail if we don't have room.
166 if (NewPtr > BufferEnd) {
167 CurBufferPtr = BufferEnd;
170 while (CurBufferPtr < NewPtr) {
171 *CurBufferPtr++ = Fill;
175 /// emitULEB128Bytes - This callback is invoked when a ULEB128 needs to be
176 /// written to the output stream.
177 void emitULEB128Bytes(uint64_t Value, unsigned PadTo = 0) {
179 uint8_t Byte = Value & 0x7f;
181 if (Value || PadTo != 0) Byte |= 0x80;
187 uint8_t Byte = (PadTo > 1) ? 0x80 : 0x0;
193 /// emitSLEB128Bytes - This callback is invoked when a SLEB128 needs to be
194 /// written to the output stream.
195 void emitSLEB128Bytes(int64_t Value) {
196 int32_t Sign = Value >> (8 * sizeof(Value) - 1);
200 uint8_t Byte = Value & 0x7f;
202 IsMore = Value != Sign || ((Byte ^ Sign) & 0x40) != 0;
203 if (IsMore) Byte |= 0x80;
208 /// emitString - This callback is invoked when a String needs to be
209 /// written to the output stream.
210 void emitString(const std::string &String) {
211 for (unsigned i = 0, N = static_cast<unsigned>(String.size());
213 uint8_t C = String[i];
219 /// emitInt32 - Emit a int32 directive.
220 void emitInt32(uint32_t Value) {
221 if (4 <= BufferEnd-CurBufferPtr) {
222 *((uint32_t*)CurBufferPtr) = Value;
225 CurBufferPtr = BufferEnd;
229 /// emitInt64 - Emit a int64 directive.
230 void emitInt64(uint64_t Value) {
231 if (8 <= BufferEnd-CurBufferPtr) {
232 *((uint64_t*)CurBufferPtr) = Value;
235 CurBufferPtr = BufferEnd;
239 /// emitInt32At - Emit the Int32 Value in Addr.
240 void emitInt32At(uintptr_t *Addr, uintptr_t Value) {
241 if (Addr >= (uintptr_t*)BufferBegin && Addr < (uintptr_t*)BufferEnd)
242 (*(uint32_t*)Addr) = (uint32_t)Value;
245 /// emitInt64At - Emit the Int64 Value in Addr.
246 void emitInt64At(uintptr_t *Addr, uintptr_t Value) {
247 if (Addr >= (uintptr_t*)BufferBegin && Addr < (uintptr_t*)BufferEnd)
248 (*(uint64_t*)Addr) = (uint64_t)Value;
252 /// emitLabel - Emits a label
253 virtual void emitLabel(MCSymbol *Label) = 0;
255 /// allocateSpace - Allocate a block of space in the current output buffer,
256 /// returning null (and setting conditions to indicate buffer overflow) on
257 /// failure. Alignment is the alignment in bytes of the buffer desired.
258 virtual void *allocateSpace(uintptr_t Size, unsigned Alignment) {
259 emitAlignment(Alignment);
262 // Check for buffer overflow.
263 if (Size >= (uintptr_t)(BufferEnd-CurBufferPtr)) {
264 CurBufferPtr = BufferEnd;
267 // Allocate the space.
268 Result = CurBufferPtr;
269 CurBufferPtr += Size;
275 /// allocateGlobal - Allocate memory for a global. Unlike allocateSpace,
276 /// this method does not allocate memory in the current output buffer,
277 /// because a global may live longer than the current function.
278 virtual void *allocateGlobal(uintptr_t Size, unsigned Alignment) = 0;
280 /// StartMachineBasicBlock - This should be called by the target when a new
281 /// basic block is about to be emitted. This way the MCE knows where the
282 /// start of the block is, and can implement getMachineBasicBlockAddress.
283 virtual void StartMachineBasicBlock(MachineBasicBlock *MBB) = 0;
285 /// getCurrentPCValue - This returns the address that the next emitted byte
286 /// will be output to.
288 virtual uintptr_t getCurrentPCValue() const {
289 return (uintptr_t)CurBufferPtr;
292 /// getCurrentPCOffset - Return the offset from the start of the emitted
293 /// buffer that we are currently writing to.
294 uintptr_t getCurrentPCOffset() const {
295 return CurBufferPtr-BufferBegin;
298 /// earlyResolveAddresses - True if the code emitter can use symbol addresses
299 /// during code emission time. The JIT is capable of doing this because it
300 /// creates jump tables or constant pools in memory on the fly while the
301 /// object code emitters rely on a linker to have real addresses and should
302 /// use relocations instead.
303 bool earlyResolveAddresses() const { return true; }
305 /// addRelocation - Whenever a relocatable address is needed, it should be
306 /// noted with this interface.
307 virtual void addRelocation(const MachineRelocation &MR) = 0;
309 /// FIXME: These should all be handled with relocations!
311 /// getConstantPoolEntryAddress - Return the address of the 'Index' entry in
312 /// the constant pool that was last emitted with the emitConstantPool method.
314 virtual uintptr_t getConstantPoolEntryAddress(unsigned Index) const = 0;
316 /// getJumpTableEntryAddress - Return the address of the jump table with index
317 /// 'Index' in the function that last called initJumpTableInfo.
319 virtual uintptr_t getJumpTableEntryAddress(unsigned Index) const = 0;
321 /// getMachineBasicBlockAddress - Return the address of the specified
322 /// MachineBasicBlock, only usable after the label for the MBB has been
325 virtual uintptr_t getMachineBasicBlockAddress(MachineBasicBlock *MBB) const= 0;
327 /// getLabelAddress - Return the address of the specified Label, only usable
328 /// after the Label has been emitted.
330 virtual uintptr_t getLabelAddress(MCSymbol *Label) const = 0;
332 /// Specifies the MachineModuleInfo object. This is used for exception handling
334 virtual void setModuleInfo(MachineModuleInfo* Info) = 0;
336 /// getLabelLocations - Return the label locations map of the label IDs to
338 virtual DenseMap<MCSymbol*, uintptr_t> *getLabelLocations() { return 0; }
341 } // End llvm namespace