1 //===-- llvm/CodeGen/MachineCodeEmitter.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_MACHINECODEEMITTER_H
18 #define LLVM_CODEGEN_MACHINECODEEMITTER_H
20 #include "llvm/Support/DataTypes.h"
24 class MachineBasicBlock;
25 class MachineConstantPool;
26 class MachineJumpTableInfo;
27 class MachineFunction;
28 class MachineModuleInfo;
29 class MachineRelocation;
34 /// MachineCodeEmitter - This class defines two sorts of methods: those for
35 /// emitting the actual bytes of machine code, and those for emitting auxillary
36 /// structures, such as jump tables, relocations, etc.
38 /// Emission of machine code is complicated by the fact that we don't (in
39 /// general) know the size of the machine code that we're about to emit before
40 /// we emit it. As such, we preallocate a certain amount of memory, and set the
41 /// BufferBegin/BufferEnd pointers to the start and end of the buffer. As we
42 /// emit machine instructions, we advance the CurBufferPtr to indicate the
43 /// location of the next byte to emit. In the case of a buffer overflow (we
44 /// need to emit more machine code than we have allocated space for), the
45 /// CurBufferPtr will saturate to BufferEnd and ignore stores. Once the entire
46 /// function has been emitted, the overflow condition is checked, and if it has
47 /// occurred, more memory is allocated, and we reemit the code into it.
49 class MachineCodeEmitter {
51 /// BufferBegin/BufferEnd - Pointers to the start and end of the memory
52 /// allocated for this code buffer.
53 unsigned char *BufferBegin, *BufferEnd;
55 /// CurBufferPtr - Pointer to the next byte of memory to fill when emitting
56 /// code. This is guranteed to be in the range [BufferBegin,BufferEnd]. If
57 /// this pointer is at BufferEnd, it will never move due to code emission, and
58 /// all code emission requests will be ignored (this is the buffer overflow
60 unsigned char *CurBufferPtr;
63 virtual ~MachineCodeEmitter() {}
65 /// startFunction - This callback is invoked when the specified function is
66 /// about to be code generated. This initializes the BufferBegin/End/Ptr
69 virtual void startFunction(MachineFunction &F) = 0;
71 /// finishFunction - This callback is invoked when the specified function has
72 /// finished code generation. If a buffer overflow has occurred, this method
73 /// returns true (the callee is required to try again), otherwise it returns
76 virtual bool finishFunction(MachineFunction &F) = 0;
78 /// startGVStub - This callback is invoked when the JIT needs the
79 /// address of a GV (e.g. function) that has not been code generated yet.
80 /// The StubSize specifies the total size required by the stub.
82 virtual void startGVStub(const GlobalValue* GV, unsigned StubSize,
83 unsigned Alignment = 1) = 0;
85 /// startGVStub - This callback is invoked when the JIT needs the address of a
86 /// GV (e.g. function) that has not been code generated yet. Buffer points to
87 /// memory already allocated for this stub.
89 virtual void startGVStub(const GlobalValue* GV, void *Buffer,
90 unsigned StubSize) = 0;
92 /// finishGVStub - This callback is invoked to terminate a GV stub.
94 virtual void *finishGVStub(const GlobalValue* F) = 0;
96 /// emitByte - This callback is invoked when a byte needs to be written to the
99 void emitByte(unsigned char B) {
100 if (CurBufferPtr != BufferEnd)
104 /// emitWordLE - This callback is invoked when a 32-bit word needs to be
105 /// written to the output stream in little-endian format.
107 void emitWordLE(unsigned W) {
108 if (4 <= BufferEnd-CurBufferPtr) {
109 *CurBufferPtr++ = (unsigned char)(W >> 0);
110 *CurBufferPtr++ = (unsigned char)(W >> 8);
111 *CurBufferPtr++ = (unsigned char)(W >> 16);
112 *CurBufferPtr++ = (unsigned char)(W >> 24);
114 CurBufferPtr = BufferEnd;
118 /// emitWordBE - This callback is invoked when a 32-bit word needs to be
119 /// written to the output stream in big-endian format.
121 void emitWordBE(unsigned W) {
122 if (4 <= BufferEnd-CurBufferPtr) {
123 *CurBufferPtr++ = (unsigned char)(W >> 24);
124 *CurBufferPtr++ = (unsigned char)(W >> 16);
125 *CurBufferPtr++ = (unsigned char)(W >> 8);
126 *CurBufferPtr++ = (unsigned char)(W >> 0);
128 CurBufferPtr = BufferEnd;
132 /// emitDWordLE - This callback is invoked when a 64-bit word needs to be
133 /// written to the output stream in little-endian format.
135 void emitDWordLE(uint64_t W) {
136 if (8 <= BufferEnd-CurBufferPtr) {
137 *CurBufferPtr++ = (unsigned char)(W >> 0);
138 *CurBufferPtr++ = (unsigned char)(W >> 8);
139 *CurBufferPtr++ = (unsigned char)(W >> 16);
140 *CurBufferPtr++ = (unsigned char)(W >> 24);
141 *CurBufferPtr++ = (unsigned char)(W >> 32);
142 *CurBufferPtr++ = (unsigned char)(W >> 40);
143 *CurBufferPtr++ = (unsigned char)(W >> 48);
144 *CurBufferPtr++ = (unsigned char)(W >> 56);
146 CurBufferPtr = BufferEnd;
150 /// emitDWordBE - This callback is invoked when a 64-bit word needs to be
151 /// written to the output stream in big-endian format.
153 void emitDWordBE(uint64_t W) {
154 if (8 <= BufferEnd-CurBufferPtr) {
155 *CurBufferPtr++ = (unsigned char)(W >> 56);
156 *CurBufferPtr++ = (unsigned char)(W >> 48);
157 *CurBufferPtr++ = (unsigned char)(W >> 40);
158 *CurBufferPtr++ = (unsigned char)(W >> 32);
159 *CurBufferPtr++ = (unsigned char)(W >> 24);
160 *CurBufferPtr++ = (unsigned char)(W >> 16);
161 *CurBufferPtr++ = (unsigned char)(W >> 8);
162 *CurBufferPtr++ = (unsigned char)(W >> 0);
164 CurBufferPtr = BufferEnd;
168 /// emitAlignment - Move the CurBufferPtr pointer up the the specified
169 /// alignment (saturated to BufferEnd of course).
170 void emitAlignment(unsigned Alignment) {
171 if (Alignment == 0) Alignment = 1;
173 if(Alignment <= (uintptr_t)(BufferEnd-CurBufferPtr)) {
174 // Move the current buffer ptr up to the specified alignment.
176 (unsigned char*)(((uintptr_t)CurBufferPtr+Alignment-1) &
177 ~(uintptr_t)(Alignment-1));
179 CurBufferPtr = BufferEnd;
184 /// emitULEB128Bytes - This callback is invoked when a ULEB128 needs to be
185 /// written to the output stream.
186 void emitULEB128Bytes(unsigned Value) {
188 unsigned char Byte = Value & 0x7f;
190 if (Value) Byte |= 0x80;
195 /// emitSLEB128Bytes - This callback is invoked when a SLEB128 needs to be
196 /// written to the output stream.
197 void emitSLEB128Bytes(int Value) {
198 int Sign = Value >> (8 * sizeof(Value) - 1);
202 unsigned char Byte = Value & 0x7f;
204 IsMore = Value != Sign || ((Byte ^ Sign) & 0x40) != 0;
205 if (IsMore) Byte |= 0x80;
210 /// emitString - This callback is invoked when a String needs to be
211 /// written to the output stream.
212 void emitString(const std::string &String) {
213 for (unsigned i = 0, N = static_cast<unsigned>(String.size());
215 unsigned char C = String[i];
221 /// emitInt32 - Emit a int32 directive.
222 void emitInt32(int Value) {
223 if (4 <= BufferEnd-CurBufferPtr) {
224 *((uint32_t*)CurBufferPtr) = Value;
227 CurBufferPtr = BufferEnd;
231 /// emitInt64 - Emit a int64 directive.
232 void emitInt64(uint64_t Value) {
233 if (8 <= BufferEnd-CurBufferPtr) {
234 *((uint64_t*)CurBufferPtr) = Value;
237 CurBufferPtr = BufferEnd;
241 /// emitInt32At - Emit the Int32 Value in Addr.
242 void emitInt32At(uintptr_t *Addr, uintptr_t Value) {
243 if (Addr >= (uintptr_t*)BufferBegin && Addr < (uintptr_t*)BufferEnd)
244 (*(uint32_t*)Addr) = (uint32_t)Value;
247 /// emitInt64At - Emit the Int64 Value in Addr.
248 void emitInt64At(uintptr_t *Addr, uintptr_t Value) {
249 if (Addr >= (uintptr_t*)BufferBegin && Addr < (uintptr_t*)BufferEnd)
250 (*(uint64_t*)Addr) = (uint64_t)Value;
254 /// emitLabel - Emits a label
255 virtual void emitLabel(uint64_t LabelID) = 0;
257 /// allocateSpace - Allocate a block of space in the current output buffer,
258 /// returning null (and setting conditions to indicate buffer overflow) on
259 /// failure. Alignment is the alignment in bytes of the buffer desired.
260 virtual void *allocateSpace(uintptr_t Size, unsigned Alignment) {
261 emitAlignment(Alignment);
264 // Check for buffer overflow.
265 if (Size >= (uintptr_t)(BufferEnd-CurBufferPtr)) {
266 CurBufferPtr = BufferEnd;
269 // Allocate the space.
270 Result = CurBufferPtr;
271 CurBufferPtr += Size;
277 /// StartMachineBasicBlock - This should be called by the target when a new
278 /// basic block is about to be emitted. This way the MCE knows where the
279 /// start of the block is, and can implement getMachineBasicBlockAddress.
280 virtual void StartMachineBasicBlock(MachineBasicBlock *MBB) = 0;
282 /// getCurrentPCValue - This returns the address that the next emitted byte
283 /// will be output to.
285 virtual uintptr_t getCurrentPCValue() const {
286 return (uintptr_t)CurBufferPtr;
289 /// getCurrentPCOffset - Return the offset from the start of the emitted
290 /// buffer that we are currently writing to.
291 uintptr_t getCurrentPCOffset() const {
292 return CurBufferPtr-BufferBegin;
295 /// addRelocation - Whenever a relocatable address is needed, it should be
296 /// noted with this interface.
297 virtual void addRelocation(const MachineRelocation &MR) = 0;
300 /// FIXME: These should all be handled with relocations!
302 /// getConstantPoolEntryAddress - Return the address of the 'Index' entry in
303 /// the constant pool that was last emitted with the emitConstantPool method.
305 virtual uintptr_t getConstantPoolEntryAddress(unsigned Index) const = 0;
307 /// getJumpTableEntryAddress - Return the address of the jump table with index
308 /// 'Index' in the function that last called initJumpTableInfo.
310 virtual uintptr_t getJumpTableEntryAddress(unsigned Index) const = 0;
312 /// getMachineBasicBlockAddress - Return the address of the specified
313 /// MachineBasicBlock, only usable after the label for the MBB has been
316 virtual uintptr_t getMachineBasicBlockAddress(MachineBasicBlock *MBB) const= 0;
318 /// getLabelAddress - Return the address of the specified LabelID, only usable
319 /// after the LabelID has been emitted.
321 virtual uintptr_t getLabelAddress(uint64_t LabelID) const = 0;
323 /// Specifies the MachineModuleInfo object. This is used for exception handling
325 virtual void setModuleInfo(MachineModuleInfo* Info) = 0;
328 } // End llvm namespace