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
20 #include "llvm/ADT/DenseMap.h"
21 #include "llvm/CodeGen/MachineCodeEmitter.h"
22 #include "llvm/Support/DataTypes.h"
23 #include "llvm/Support/MathExtras.h"
28 class MachineBasicBlock;
29 class MachineConstantPool;
30 class MachineJumpTableInfo;
31 class MachineFunction;
32 class MachineModuleInfo;
33 class MachineRelocation;
38 /// JITCodeEmitter - This class defines two sorts of methods: those for
39 /// emitting the actual bytes of machine code, and those for emitting auxiliary
40 /// structures, such as jump tables, relocations, etc.
42 /// Emission of machine code is complicated by the fact that we don't (in
43 /// general) know the size of the machine code that we're about to emit before
44 /// we emit it. As such, we preallocate a certain amount of memory, and set the
45 /// BufferBegin/BufferEnd pointers to the start and end of the buffer. As we
46 /// emit machine instructions, we advance the CurBufferPtr to indicate the
47 /// location of the next byte to emit. In the case of a buffer overflow (we
48 /// need to emit more machine code than we have allocated space for), the
49 /// CurBufferPtr will saturate to BufferEnd and ignore stores. Once the entire
50 /// function has been emitted, the overflow condition is checked, and if it has
51 /// occurred, more memory is allocated, and we reemit the code into it.
53 class JITCodeEmitter : public MachineCodeEmitter {
54 void anchor() override;
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 void startFunction(MachineFunction &F) override = 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 bool finishFunction(MachineFunction &F) override = 0;
71 /// allocIndirectGV - Allocates and fills storage for an indirect
72 /// GlobalValue, and returns the address.
73 virtual void *allocIndirectGV(const GlobalValue *GV,
74 const uint8_t *Buffer, size_t Size,
75 unsigned Alignment) = 0;
77 /// emitByte - This callback is invoked when a byte needs to be written to the
80 void emitByte(uint8_t B) {
81 if (CurBufferPtr != BufferEnd)
85 /// emitWordLE - This callback is invoked when a 32-bit word needs to be
86 /// written to the output stream in little-endian format.
88 void emitWordLE(uint32_t W) {
89 if (4 <= BufferEnd-CurBufferPtr) {
90 *CurBufferPtr++ = (uint8_t)(W >> 0);
91 *CurBufferPtr++ = (uint8_t)(W >> 8);
92 *CurBufferPtr++ = (uint8_t)(W >> 16);
93 *CurBufferPtr++ = (uint8_t)(W >> 24);
95 CurBufferPtr = BufferEnd;
99 /// emitWordBE - This callback is invoked when a 32-bit word needs to be
100 /// written to the output stream in big-endian format.
102 void emitWordBE(uint32_t W) {
103 if (4 <= BufferEnd-CurBufferPtr) {
104 *CurBufferPtr++ = (uint8_t)(W >> 24);
105 *CurBufferPtr++ = (uint8_t)(W >> 16);
106 *CurBufferPtr++ = (uint8_t)(W >> 8);
107 *CurBufferPtr++ = (uint8_t)(W >> 0);
109 CurBufferPtr = BufferEnd;
113 /// emitDWordLE - This callback is invoked when a 64-bit word needs to be
114 /// written to the output stream in little-endian format.
116 void emitDWordLE(uint64_t W) {
117 if (8 <= BufferEnd-CurBufferPtr) {
118 *CurBufferPtr++ = (uint8_t)(W >> 0);
119 *CurBufferPtr++ = (uint8_t)(W >> 8);
120 *CurBufferPtr++ = (uint8_t)(W >> 16);
121 *CurBufferPtr++ = (uint8_t)(W >> 24);
122 *CurBufferPtr++ = (uint8_t)(W >> 32);
123 *CurBufferPtr++ = (uint8_t)(W >> 40);
124 *CurBufferPtr++ = (uint8_t)(W >> 48);
125 *CurBufferPtr++ = (uint8_t)(W >> 56);
127 CurBufferPtr = BufferEnd;
131 /// emitDWordBE - This callback is invoked when a 64-bit word needs to be
132 /// written to the output stream in big-endian format.
134 void emitDWordBE(uint64_t W) {
135 if (8 <= BufferEnd-CurBufferPtr) {
136 *CurBufferPtr++ = (uint8_t)(W >> 56);
137 *CurBufferPtr++ = (uint8_t)(W >> 48);
138 *CurBufferPtr++ = (uint8_t)(W >> 40);
139 *CurBufferPtr++ = (uint8_t)(W >> 32);
140 *CurBufferPtr++ = (uint8_t)(W >> 24);
141 *CurBufferPtr++ = (uint8_t)(W >> 16);
142 *CurBufferPtr++ = (uint8_t)(W >> 8);
143 *CurBufferPtr++ = (uint8_t)(W >> 0);
145 CurBufferPtr = BufferEnd;
149 /// emitAlignment - Move the CurBufferPtr pointer up to the specified
150 /// alignment (saturated to BufferEnd of course).
151 void emitAlignment(unsigned Alignment) {
152 if (Alignment == 0) Alignment = 1;
153 uint8_t *NewPtr = (uint8_t*)RoundUpToAlignment((uintptr_t)CurBufferPtr,
155 CurBufferPtr = std::min(NewPtr, BufferEnd);
158 /// emitAlignmentWithFill - Similar to emitAlignment, except that the
159 /// extra bytes are filled with the provided byte.
160 void emitAlignmentWithFill(unsigned Alignment, uint8_t Fill) {
161 if (Alignment == 0) Alignment = 1;
162 uint8_t *NewPtr = (uint8_t*)RoundUpToAlignment((uintptr_t)CurBufferPtr,
164 // Fail if we don't have room.
165 if (NewPtr > BufferEnd) {
166 CurBufferPtr = BufferEnd;
169 while (CurBufferPtr < NewPtr) {
170 *CurBufferPtr++ = Fill;
174 /// emitULEB128Bytes - This callback is invoked when a ULEB128 needs to be
175 /// written to the output stream.
176 void emitULEB128Bytes(uint64_t Value, unsigned PadTo = 0) {
178 uint8_t Byte = Value & 0x7f;
180 if (Value || PadTo != 0) Byte |= 0x80;
186 uint8_t Byte = (PadTo > 1) ? 0x80 : 0x0;
192 /// emitSLEB128Bytes - This callback is invoked when a SLEB128 needs to be
193 /// written to the output stream.
194 void emitSLEB128Bytes(int64_t Value) {
195 int32_t Sign = Value >> (8 * sizeof(Value) - 1);
199 uint8_t Byte = Value & 0x7f;
201 IsMore = Value != Sign || ((Byte ^ Sign) & 0x40) != 0;
202 if (IsMore) Byte |= 0x80;
207 /// emitString - This callback is invoked when a String needs to be
208 /// written to the output stream.
209 void emitString(const std::string &String) {
210 for (size_t i = 0, N = String.size(); i < N; ++i) {
211 uint8_t C = String[i];
217 /// emitInt32 - Emit a int32 directive.
218 void emitInt32(uint32_t Value) {
219 if (4 <= BufferEnd-CurBufferPtr) {
220 *((uint32_t*)CurBufferPtr) = Value;
223 CurBufferPtr = BufferEnd;
227 /// emitInt64 - Emit a int64 directive.
228 void emitInt64(uint64_t Value) {
229 if (8 <= BufferEnd-CurBufferPtr) {
230 *((uint64_t*)CurBufferPtr) = Value;
233 CurBufferPtr = BufferEnd;
237 /// emitInt32At - Emit the Int32 Value in Addr.
238 void emitInt32At(uintptr_t *Addr, uintptr_t Value) {
239 if (Addr >= (uintptr_t*)BufferBegin && Addr < (uintptr_t*)BufferEnd)
240 (*(uint32_t*)Addr) = (uint32_t)Value;
243 /// emitInt64At - Emit the Int64 Value in Addr.
244 void emitInt64At(uintptr_t *Addr, uintptr_t Value) {
245 if (Addr >= (uintptr_t*)BufferBegin && Addr < (uintptr_t*)BufferEnd)
246 (*(uint64_t*)Addr) = (uint64_t)Value;
250 /// emitLabel - Emits a label
251 void emitLabel(MCSymbol *Label) override = 0;
253 /// allocateSpace - Allocate a block of space in the current output buffer,
254 /// returning null (and setting conditions to indicate buffer overflow) on
255 /// failure. Alignment is the alignment in bytes of the buffer desired.
256 void *allocateSpace(uintptr_t Size, unsigned Alignment) override {
257 emitAlignment(Alignment);
260 // Check for buffer overflow.
261 if (Size >= (uintptr_t)(BufferEnd-CurBufferPtr)) {
262 CurBufferPtr = BufferEnd;
265 // Allocate the space.
266 Result = CurBufferPtr;
267 CurBufferPtr += Size;
273 /// allocateGlobal - Allocate memory for a global. Unlike allocateSpace,
274 /// this method does not allocate memory in the current output buffer,
275 /// because a global may live longer than the current function.
276 virtual void *allocateGlobal(uintptr_t Size, unsigned Alignment) = 0;
278 /// StartMachineBasicBlock - This should be called by the target when a new
279 /// basic block is about to be emitted. This way the MCE knows where the
280 /// start of the block is, and can implement getMachineBasicBlockAddress.
281 void StartMachineBasicBlock(MachineBasicBlock *MBB) override = 0;
283 /// getCurrentPCValue - This returns the address that the next emitted byte
284 /// will be output to.
286 uintptr_t getCurrentPCValue() const override {
287 return (uintptr_t)CurBufferPtr;
290 /// getCurrentPCOffset - Return the offset from the start of the emitted
291 /// buffer that we are currently writing to.
292 uintptr_t getCurrentPCOffset() const override {
293 return CurBufferPtr-BufferBegin;
296 /// earlyResolveAddresses - True if the code emitter can use symbol addresses
297 /// during code emission time. The JIT is capable of doing this because it
298 /// creates jump tables or constant pools in memory on the fly while the
299 /// object code emitters rely on a linker to have real addresses and should
300 /// use relocations instead.
301 bool earlyResolveAddresses() const override { return true; }
303 /// addRelocation - Whenever a relocatable address is needed, it should be
304 /// noted with this interface.
305 void addRelocation(const MachineRelocation &MR) override = 0;
307 /// FIXME: These should all be handled with relocations!
309 /// getConstantPoolEntryAddress - Return the address of the 'Index' entry in
310 /// the constant pool that was last emitted with the emitConstantPool method.
312 uintptr_t getConstantPoolEntryAddress(unsigned Index) const override = 0;
314 /// getJumpTableEntryAddress - Return the address of the jump table with index
315 /// 'Index' in the function that last called initJumpTableInfo.
317 uintptr_t getJumpTableEntryAddress(unsigned Index) const override = 0;
319 /// getMachineBasicBlockAddress - Return the address of the specified
320 /// MachineBasicBlock, only usable after the label for the MBB has been
324 getMachineBasicBlockAddress(MachineBasicBlock *MBB) const override = 0;
326 /// getLabelAddress - Return the address of the specified Label, only usable
327 /// after the Label has been emitted.
329 uintptr_t getLabelAddress(MCSymbol *Label) const override = 0;
331 /// Specifies the MachineModuleInfo object. This is used for exception handling
333 void setModuleInfo(MachineModuleInfo* Info) override = 0;
335 /// getLabelLocations - Return the label locations map of the label IDs to
337 virtual DenseMap<MCSymbol*, uintptr_t> *getLabelLocations() {
342 } // End llvm namespace