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JITCodeEmitter.h
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1 //===-- llvm/CodeGen/JITCodeEmitter.h - Code emission ----------*- C++ -*-===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
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.).
14 //
15 //===----------------------------------------------------------------------===//
16 
17 #ifndef LLVM_CODEGEN_JITCODEEMITTER_H
18 #define LLVM_CODEGEN_JITCODEEMITTER_H
19 
20 #include "llvm/ADT/DenseMap.h"
22 #include "llvm/Support/DataTypes.h"
24 #include <string>
25 
26 namespace llvm {
27 
28 class MachineBasicBlock;
29 class MachineConstantPool;
30 class MachineJumpTableInfo;
31 class MachineFunction;
32 class MachineModuleInfo;
33 class MachineRelocation;
34 class Value;
35 class GlobalValue;
36 class Function;
37 
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.
41 ///
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.
52 ///
54  virtual void anchor();
55 public:
56  virtual ~JITCodeEmitter() {}
57 
58  /// startFunction - This callback is invoked when the specified function is
59  /// about to be code generated. This initializes the BufferBegin/End/Ptr
60  /// fields.
61  ///
62  virtual void startFunction(MachineFunction &F) = 0;
63 
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
67  /// false.
68  ///
69  virtual bool finishFunction(MachineFunction &F) = 0;
70 
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;
76 
77  /// emitByte - This callback is invoked when a byte needs to be written to the
78  /// output stream.
79  ///
80  void emitByte(uint8_t B) {
81  if (CurBufferPtr != BufferEnd)
82  *CurBufferPtr++ = B;
83  }
84 
85  /// emitWordLE - This callback is invoked when a 32-bit word needs to be
86  /// written to the output stream in little-endian format.
87  ///
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);
94  } else {
96  }
97  }
98 
99  /// emitWordBE - This callback is invoked when a 32-bit word needs to be
100  /// written to the output stream in big-endian format.
101  ///
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);
108  } else {
110  }
111  }
112 
113  /// emitDWordLE - This callback is invoked when a 64-bit word needs to be
114  /// written to the output stream in little-endian format.
115  ///
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);
126  } else {
128  }
129  }
130 
131  /// emitDWordBE - This callback is invoked when a 64-bit word needs to be
132  /// written to the output stream in big-endian format.
133  ///
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);
144  } else {
146  }
147  }
148 
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,
154  Alignment);
155  CurBufferPtr = std::min(NewPtr, BufferEnd);
156  }
157 
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,
163  Alignment);
164  // Fail if we don't have room.
165  if (NewPtr > BufferEnd) {
167  return;
168  }
169  while (CurBufferPtr < NewPtr) {
170  *CurBufferPtr++ = Fill;
171  }
172  }
173 
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) {
177  do {
178  uint8_t Byte = Value & 0x7f;
179  Value >>= 7;
180  if (Value || PadTo != 0) Byte |= 0x80;
181  emitByte(Byte);
182  } while (Value);
183 
184  if (PadTo) {
185  do {
186  uint8_t Byte = (PadTo > 1) ? 0x80 : 0x0;
187  emitByte(Byte);
188  } while (--PadTo);
189  }
190  }
191 
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);
196  bool IsMore;
197 
198  do {
199  uint8_t Byte = Value & 0x7f;
200  Value >>= 7;
201  IsMore = Value != Sign || ((Byte ^ Sign) & 0x40) != 0;
202  if (IsMore) Byte |= 0x80;
203  emitByte(Byte);
204  } while (IsMore);
205  }
206 
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];
212  emitByte(C);
213  }
214  emitByte(0);
215  }
216 
217  /// emitInt32 - Emit a int32 directive.
218  void emitInt32(uint32_t Value) {
219  if (4 <= BufferEnd-CurBufferPtr) {
220  *((uint32_t*)CurBufferPtr) = Value;
221  CurBufferPtr += 4;
222  } else {
224  }
225  }
226 
227  /// emitInt64 - Emit a int64 directive.
228  void emitInt64(uint64_t Value) {
229  if (8 <= BufferEnd-CurBufferPtr) {
230  *((uint64_t*)CurBufferPtr) = Value;
231  CurBufferPtr += 8;
232  } else {
234  }
235  }
236 
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;
241  }
242 
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;
247  }
248 
249 
250  /// emitLabel - Emits a label
251  virtual void emitLabel(MCSymbol *Label) = 0;
252 
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  virtual void *allocateSpace(uintptr_t Size, unsigned Alignment) {
257  emitAlignment(Alignment);
258  void *Result;
259 
260  // Check for buffer overflow.
261  if (Size >= (uintptr_t)(BufferEnd-CurBufferPtr)) {
263  Result = 0;
264  } else {
265  // Allocate the space.
266  Result = CurBufferPtr;
267  CurBufferPtr += Size;
268  }
269 
270  return Result;
271  }
272 
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;
277 
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  virtual void StartMachineBasicBlock(MachineBasicBlock *MBB) = 0;
282 
283  /// getCurrentPCValue - This returns the address that the next emitted byte
284  /// will be output to.
285  ///
286  virtual uintptr_t getCurrentPCValue() const {
287  return (uintptr_t)CurBufferPtr;
288  }
289 
290  /// getCurrentPCOffset - Return the offset from the start of the emitted
291  /// buffer that we are currently writing to.
292  uintptr_t getCurrentPCOffset() const {
293  return CurBufferPtr-BufferBegin;
294  }
295 
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 { return true; }
302 
303  /// addRelocation - Whenever a relocatable address is needed, it should be
304  /// noted with this interface.
305  virtual void addRelocation(const MachineRelocation &MR) = 0;
306 
307  /// FIXME: These should all be handled with relocations!
308 
309  /// getConstantPoolEntryAddress - Return the address of the 'Index' entry in
310  /// the constant pool that was last emitted with the emitConstantPool method.
311  ///
312  virtual uintptr_t getConstantPoolEntryAddress(unsigned Index) const = 0;
313 
314  /// getJumpTableEntryAddress - Return the address of the jump table with index
315  /// 'Index' in the function that last called initJumpTableInfo.
316  ///
317  virtual uintptr_t getJumpTableEntryAddress(unsigned Index) const = 0;
318 
319  /// getMachineBasicBlockAddress - Return the address of the specified
320  /// MachineBasicBlock, only usable after the label for the MBB has been
321  /// emitted.
322  ///
323  virtual uintptr_t getMachineBasicBlockAddress(MachineBasicBlock *MBB) const= 0;
324 
325  /// getLabelAddress - Return the address of the specified Label, only usable
326  /// after the Label has been emitted.
327  ///
328  virtual uintptr_t getLabelAddress(MCSymbol *Label) const = 0;
329 
330  /// Specifies the MachineModuleInfo object. This is used for exception handling
331  /// purposes.
332  virtual void setModuleInfo(MachineModuleInfo* Info) = 0;
333 
334  /// getLabelLocations - Return the label locations map of the label IDs to
335  /// their address.
337 };
338 
339 } // End llvm namespace
340 
341 #endif
void emitAlignment(unsigned Alignment)
virtual void startFunction(MachineFunction &F)=0
void emitByte(uint8_t B)
F(f)
virtual void * allocateSpace(uintptr_t Size, unsigned Alignment)
virtual uintptr_t getConstantPoolEntryAddress(unsigned Index) const =0
FIXME: These should all be handled with relocations!
virtual uintptr_t getJumpTableEntryAddress(unsigned Index) const =0
void emitInt64(uint64_t Value)
emitInt64 - Emit a int64 directive.
virtual uintptr_t getLabelAddress(MCSymbol *Label) const =0
virtual void setModuleInfo(MachineModuleInfo *Info)=0
virtual uintptr_t getMachineBasicBlockAddress(MachineBasicBlock *MBB) const =0
bool earlyResolveAddresses() const
virtual DenseMap< MCSymbol *, uintptr_t > * getLabelLocations()
void emitDWordLE(uint64_t W)
void emitWordBE(uint32_t W)
virtual bool finishFunction(MachineFunction &F)=0
void emitDWordBE(uint64_t W)
void emitInt64At(uintptr_t *Addr, uintptr_t Value)
emitInt64At - Emit the Int64 Value in Addr.
void emitInt32(uint32_t Value)
emitInt32 - Emit a int32 directive.
virtual uintptr_t getCurrentPCValue() const
virtual void * allocIndirectGV(const GlobalValue *GV, const uint8_t *Buffer, size_t Size, unsigned Alignment)=0
uintptr_t getCurrentPCOffset() const
uint64_t RoundUpToAlignment(uint64_t Value, uint64_t Align)
Definition: MathExtras.h:565
virtual void addRelocation(const MachineRelocation &MR)=0
virtual void * allocateGlobal(uintptr_t Size, unsigned Alignment)=0
void emitAlignmentWithFill(unsigned Alignment, uint8_t Fill)
void emitWordLE(uint32_t W)
void emitULEB128Bytes(uint64_t Value, unsigned PadTo=0)
#define N
virtual void StartMachineBasicBlock(MachineBasicBlock *MBB)=0
LLVM Value Representation.
Definition: Value.h:66
void emitInt32At(uintptr_t *Addr, uintptr_t Value)
emitInt32At - Emit the Int32 Value in Addr.
void emitString(const std::string &String)
void emitSLEB128Bytes(int64_t Value)
virtual void emitLabel(MCSymbol *Label)=0
emitLabel - Emits a label