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"
21 #include "llvm/Support/DebugLoc.h"
25 class MachineBasicBlock;
26 class MachineConstantPool;
27 class MachineJumpTableInfo;
28 class MachineFunction;
29 class MachineModuleInfo;
30 class MachineRelocation;
35 /// MachineCodeEmitter - This class defines two sorts of methods: those for
36 /// emitting the actual bytes of machine code, and those for emitting auxillary
37 /// structures, such as jump tables, relocations, etc.
39 /// Emission of machine code is complicated by the fact that we don't (in
40 /// general) know the size of the machine code that we're about to emit before
41 /// we emit it. As such, we preallocate a certain amount of memory, and set the
42 /// BufferBegin/BufferEnd pointers to the start and end of the buffer. As we
43 /// emit machine instructions, we advance the CurBufferPtr to indicate the
44 /// location of the next byte to emit. In the case of a buffer overflow (we
45 /// need to emit more machine code than we have allocated space for), the
46 /// CurBufferPtr will saturate to BufferEnd and ignore stores. Once the entire
47 /// function has been emitted, the overflow condition is checked, and if it has
48 /// occurred, more memory is allocated, and we reemit the code into it.
50 class MachineCodeEmitter {
52 /// BufferBegin/BufferEnd - Pointers to the start and end of the memory
53 /// allocated for this code buffer.
54 uint8_t *BufferBegin, *BufferEnd;
56 /// CurBufferPtr - Pointer to the next byte of memory to fill when emitting
57 /// code. This is guranteed to be in the range [BufferBegin,BufferEnd]. If
58 /// this pointer is at BufferEnd, it will never move due to code emission, and
59 /// all code emission requests will be ignored (this is the buffer overflow
61 uint8_t *CurBufferPtr;
64 virtual ~MachineCodeEmitter() {}
66 /// startFunction - This callback is invoked when the specified function is
67 /// about to be code generated. This initializes the BufferBegin/End/Ptr
70 virtual void startFunction(MachineFunction &F) = 0;
72 /// finishFunction - This callback is invoked when the specified function has
73 /// finished code generation. If a buffer overflow has occurred, this method
74 /// returns true (the callee is required to try again), otherwise it returns
77 virtual bool finishFunction(MachineFunction &F) = 0;
79 /// emitByte - This callback is invoked when a byte needs to be written to the
82 void emitByte(uint8_t B) {
83 if (CurBufferPtr != BufferEnd)
87 /// emitWordLE - This callback is invoked when a 32-bit word needs to be
88 /// written to the output stream in little-endian format.
90 void emitWordLE(uint32_t W) {
91 if (4 <= BufferEnd-CurBufferPtr) {
92 *CurBufferPtr++ = (uint8_t)(W >> 0);
93 *CurBufferPtr++ = (uint8_t)(W >> 8);
94 *CurBufferPtr++ = (uint8_t)(W >> 16);
95 *CurBufferPtr++ = (uint8_t)(W >> 24);
97 CurBufferPtr = BufferEnd;
101 /// emitWordBE - This callback is invoked when a 32-bit word needs to be
102 /// written to the output stream in big-endian format.
104 void emitWordBE(uint32_t W) {
105 if (4 <= BufferEnd-CurBufferPtr) {
106 *CurBufferPtr++ = (uint8_t)(W >> 24);
107 *CurBufferPtr++ = (uint8_t)(W >> 16);
108 *CurBufferPtr++ = (uint8_t)(W >> 8);
109 *CurBufferPtr++ = (uint8_t)(W >> 0);
111 CurBufferPtr = BufferEnd;
115 /// emitDWordLE - This callback is invoked when a 64-bit word needs to be
116 /// written to the output stream in little-endian format.
118 void emitDWordLE(uint64_t W) {
119 if (8 <= BufferEnd-CurBufferPtr) {
120 *CurBufferPtr++ = (uint8_t)(W >> 0);
121 *CurBufferPtr++ = (uint8_t)(W >> 8);
122 *CurBufferPtr++ = (uint8_t)(W >> 16);
123 *CurBufferPtr++ = (uint8_t)(W >> 24);
124 *CurBufferPtr++ = (uint8_t)(W >> 32);
125 *CurBufferPtr++ = (uint8_t)(W >> 40);
126 *CurBufferPtr++ = (uint8_t)(W >> 48);
127 *CurBufferPtr++ = (uint8_t)(W >> 56);
129 CurBufferPtr = BufferEnd;
133 /// emitDWordBE - This callback is invoked when a 64-bit word needs to be
134 /// written to the output stream in big-endian format.
136 void emitDWordBE(uint64_t W) {
137 if (8 <= BufferEnd-CurBufferPtr) {
138 *CurBufferPtr++ = (uint8_t)(W >> 56);
139 *CurBufferPtr++ = (uint8_t)(W >> 48);
140 *CurBufferPtr++ = (uint8_t)(W >> 40);
141 *CurBufferPtr++ = (uint8_t)(W >> 32);
142 *CurBufferPtr++ = (uint8_t)(W >> 24);
143 *CurBufferPtr++ = (uint8_t)(W >> 16);
144 *CurBufferPtr++ = (uint8_t)(W >> 8);
145 *CurBufferPtr++ = (uint8_t)(W >> 0);
147 CurBufferPtr = BufferEnd;
151 /// emitAlignment - Move the CurBufferPtr pointer up the the specified
152 /// alignment (saturated to BufferEnd of course).
153 void emitAlignment(unsigned Alignment) {
154 if (Alignment == 0) Alignment = 1;
156 if(Alignment <= (uintptr_t)(BufferEnd-CurBufferPtr)) {
157 // Move the current buffer ptr up to the specified alignment.
159 (uint8_t*)(((uintptr_t)CurBufferPtr+Alignment-1) &
160 ~(uintptr_t)(Alignment-1));
162 CurBufferPtr = BufferEnd;
167 /// emitULEB128Bytes - This callback is invoked when a ULEB128 needs to be
168 /// written to the output stream.
169 void emitULEB128Bytes(uint64_t Value) {
171 uint8_t Byte = Value & 0x7f;
173 if (Value) Byte |= 0x80;
178 /// emitSLEB128Bytes - This callback is invoked when a SLEB128 needs to be
179 /// written to the output stream.
180 void emitSLEB128Bytes(uint64_t Value) {
181 uint64_t Sign = Value >> (8 * sizeof(Value) - 1);
185 uint8_t Byte = Value & 0x7f;
187 IsMore = Value != Sign || ((Byte ^ Sign) & 0x40) != 0;
188 if (IsMore) Byte |= 0x80;
193 /// emitString - This callback is invoked when a String needs to be
194 /// written to the output stream.
195 void emitString(const std::string &String) {
196 for (unsigned i = 0, N = static_cast<unsigned>(String.size());
198 uint8_t C = String[i];
204 /// emitInt32 - Emit a int32 directive.
205 void emitInt32(int32_t Value) {
206 if (4 <= BufferEnd-CurBufferPtr) {
207 *((uint32_t*)CurBufferPtr) = Value;
210 CurBufferPtr = BufferEnd;
214 /// emitInt64 - Emit a int64 directive.
215 void emitInt64(uint64_t Value) {
216 if (8 <= BufferEnd-CurBufferPtr) {
217 *((uint64_t*)CurBufferPtr) = Value;
220 CurBufferPtr = BufferEnd;
224 /// emitInt32At - Emit the Int32 Value in Addr.
225 void emitInt32At(uintptr_t *Addr, uintptr_t Value) {
226 if (Addr >= (uintptr_t*)BufferBegin && Addr < (uintptr_t*)BufferEnd)
227 (*(uint32_t*)Addr) = (uint32_t)Value;
230 /// emitInt64At - Emit the Int64 Value in Addr.
231 void emitInt64At(uintptr_t *Addr, uintptr_t Value) {
232 if (Addr >= (uintptr_t*)BufferBegin && Addr < (uintptr_t*)BufferEnd)
233 (*(uint64_t*)Addr) = (uint64_t)Value;
236 /// processDebugLoc - Records debug location information about a
237 /// MachineInstruction. This is called before emitting any bytes associated
238 /// with the instruction. Even if successive instructions have the same debug
239 /// location, this method will be called for each one.
240 virtual void processDebugLoc(DebugLoc DL) {}
242 /// emitLabel - Emits a label
243 virtual void emitLabel(uint64_t LabelID) = 0;
245 /// allocateSpace - Allocate a block of space in the current output buffer,
246 /// returning null (and setting conditions to indicate buffer overflow) on
247 /// failure. Alignment is the alignment in bytes of the buffer desired.
248 virtual void *allocateSpace(uintptr_t Size, unsigned Alignment) {
249 emitAlignment(Alignment);
252 // Check for buffer overflow.
253 if (Size >= (uintptr_t)(BufferEnd-CurBufferPtr)) {
254 CurBufferPtr = BufferEnd;
257 // Allocate the space.
258 Result = CurBufferPtr;
259 CurBufferPtr += Size;
265 /// StartMachineBasicBlock - This should be called by the target when a new
266 /// basic block is about to be emitted. This way the MCE knows where the
267 /// start of the block is, and can implement getMachineBasicBlockAddress.
268 virtual void StartMachineBasicBlock(MachineBasicBlock *MBB) = 0;
270 /// getCurrentPCValue - This returns the address that the next emitted byte
271 /// will be output to.
273 virtual uintptr_t getCurrentPCValue() const {
274 return (uintptr_t)CurBufferPtr;
277 /// getCurrentPCOffset - Return the offset from the start of the emitted
278 /// buffer that we are currently writing to.
279 virtual uintptr_t getCurrentPCOffset() const {
280 return CurBufferPtr-BufferBegin;
283 /// addRelocation - Whenever a relocatable address is needed, it should be
284 /// noted with this interface.
285 virtual void addRelocation(const MachineRelocation &MR) = 0;
287 /// FIXME: These should all be handled with relocations!
289 /// getConstantPoolEntryAddress - Return the address of the 'Index' entry in
290 /// the constant pool that was last emitted with the emitConstantPool method.
292 virtual uintptr_t getConstantPoolEntryAddress(unsigned Index) const = 0;
294 /// getJumpTableEntryAddress - Return the address of the jump table with index
295 /// 'Index' in the function that last called initJumpTableInfo.
297 virtual uintptr_t getJumpTableEntryAddress(unsigned Index) const = 0;
299 /// getMachineBasicBlockAddress - Return the address of the specified
300 /// MachineBasicBlock, only usable after the label for the MBB has been
303 virtual uintptr_t getMachineBasicBlockAddress(MachineBasicBlock *MBB) const= 0;
305 /// getLabelAddress - Return the address of the specified LabelID, only usable
306 /// after the LabelID has been emitted.
308 virtual uintptr_t getLabelAddress(uint64_t LabelID) const = 0;
310 /// Specifies the MachineModuleInfo object. This is used for exception handling
312 virtual void setModuleInfo(MachineModuleInfo* Info) = 0;
315 } // End llvm namespace