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 uint8_t *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 uint8_t *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 /// 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 the the specified
151 /// alignment (saturated to BufferEnd of course).
152 void emitAlignment(unsigned Alignment) {
153 if (Alignment == 0) Alignment = 1;
155 if(Alignment <= (uintptr_t)(BufferEnd-CurBufferPtr)) {
156 // Move the current buffer ptr up to the specified alignment.
158 (uint8_t*)(((uintptr_t)CurBufferPtr+Alignment-1) &
159 ~(uintptr_t)(Alignment-1));
161 CurBufferPtr = BufferEnd;
166 /// emitULEB128Bytes - This callback is invoked when a ULEB128 needs to be
167 /// written to the output stream.
168 void emitULEB128Bytes(uint64_t Value) {
170 uint8_t Byte = Value & 0x7f;
172 if (Value) Byte |= 0x80;
177 /// emitSLEB128Bytes - This callback is invoked when a SLEB128 needs to be
178 /// written to the output stream.
179 void emitSLEB128Bytes(uint64_t Value) {
180 uint64_t Sign = Value >> (8 * sizeof(Value) - 1);
184 uint8_t Byte = Value & 0x7f;
186 IsMore = Value != Sign || ((Byte ^ Sign) & 0x40) != 0;
187 if (IsMore) Byte |= 0x80;
192 /// emitString - This callback is invoked when a String needs to be
193 /// written to the output stream.
194 void emitString(const std::string &String) {
195 for (unsigned i = 0, N = static_cast<unsigned>(String.size());
197 uint8_t C = String[i];
203 /// emitInt32 - Emit a int32 directive.
204 void emitInt32(int32_t Value) {
205 if (4 <= BufferEnd-CurBufferPtr) {
206 *((uint32_t*)CurBufferPtr) = Value;
209 CurBufferPtr = BufferEnd;
213 /// emitInt64 - Emit a int64 directive.
214 void emitInt64(uint64_t Value) {
215 if (8 <= BufferEnd-CurBufferPtr) {
216 *((uint64_t*)CurBufferPtr) = Value;
219 CurBufferPtr = BufferEnd;
223 /// emitInt32At - Emit the Int32 Value in Addr.
224 void emitInt32At(uintptr_t *Addr, uintptr_t Value) {
225 if (Addr >= (uintptr_t*)BufferBegin && Addr < (uintptr_t*)BufferEnd)
226 (*(uint32_t*)Addr) = (uint32_t)Value;
229 /// emitInt64At - Emit the Int64 Value in Addr.
230 void emitInt64At(uintptr_t *Addr, uintptr_t Value) {
231 if (Addr >= (uintptr_t*)BufferBegin && Addr < (uintptr_t*)BufferEnd)
232 (*(uint64_t*)Addr) = (uint64_t)Value;
236 /// emitLabel - Emits a label
237 virtual void emitLabel(uint64_t LabelID) = 0;
239 /// allocateSpace - Allocate a block of space in the current output buffer,
240 /// returning null (and setting conditions to indicate buffer overflow) on
241 /// failure. Alignment is the alignment in bytes of the buffer desired.
242 virtual void *allocateSpace(uintptr_t Size, unsigned Alignment) {
243 emitAlignment(Alignment);
246 // Check for buffer overflow.
247 if (Size >= (uintptr_t)(BufferEnd-CurBufferPtr)) {
248 CurBufferPtr = BufferEnd;
251 // Allocate the space.
252 Result = CurBufferPtr;
253 CurBufferPtr += Size;
259 /// StartMachineBasicBlock - This should be called by the target when a new
260 /// basic block is about to be emitted. This way the MCE knows where the
261 /// start of the block is, and can implement getMachineBasicBlockAddress.
262 virtual void StartMachineBasicBlock(MachineBasicBlock *MBB) = 0;
264 /// getCurrentPCValue - This returns the address that the next emitted byte
265 /// will be output to.
267 virtual uintptr_t getCurrentPCValue() const {
268 return (uintptr_t)CurBufferPtr;
271 /// getCurrentPCOffset - Return the offset from the start of the emitted
272 /// buffer that we are currently writing to.
273 virtual uintptr_t getCurrentPCOffset() const {
274 return CurBufferPtr-BufferBegin;
277 /// addRelocation - Whenever a relocatable address is needed, it should be
278 /// noted with this interface.
279 virtual void addRelocation(const MachineRelocation &MR) = 0;
281 /// FIXME: These should all be handled with relocations!
283 /// getConstantPoolEntryAddress - Return the address of the 'Index' entry in
284 /// the constant pool that was last emitted with the emitConstantPool method.
286 virtual uintptr_t getConstantPoolEntryAddress(unsigned Index) const = 0;
288 /// getJumpTableEntryAddress - Return the address of the jump table with index
289 /// 'Index' in the function that last called initJumpTableInfo.
291 virtual uintptr_t getJumpTableEntryAddress(unsigned Index) const = 0;
293 /// getMachineBasicBlockAddress - Return the address of the specified
294 /// MachineBasicBlock, only usable after the label for the MBB has been
297 virtual uintptr_t getMachineBasicBlockAddress(MachineBasicBlock *MBB) const= 0;
299 /// getLabelAddress - Return the address of the specified LabelID, only usable
300 /// after the LabelID has been emitted.
302 virtual uintptr_t getLabelAddress(uint64_t LabelID) const = 0;
304 /// Specifies the MachineModuleInfo object. This is used for exception handling
306 virtual void setModuleInfo(MachineModuleInfo* Info) = 0;
309 } // End llvm namespace