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"
21#include "llvm/CodeGen/MachineCodeEmitter.h"
22#include "llvm/Support/DataTypes.h"
23#include "llvm/Support/MathExtras.h"
24#include <string>
25
26namespace llvm {
27
28class MachineBasicBlock;
29class MachineConstantPool;
30class MachineJumpTableInfo;
31class MachineFunction;
32class MachineModuleInfo;
33class MachineRelocation;
34class Value;
35class GlobalValue;
36class 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///
53class JITCodeEmitter : public MachineCodeEmitter {
54  void anchor() override;
55public:
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  void startFunction(MachineFunction &F) override = 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  bool finishFunction(MachineFunction &F) override = 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 {
95      CurBufferPtr = BufferEnd;
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 {
109      CurBufferPtr = BufferEnd;
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 {
127      CurBufferPtr = BufferEnd;
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 {
145      CurBufferPtr = BufferEnd;
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) {
166      CurBufferPtr = 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 {
223      CurBufferPtr = BufferEnd;
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 {
233      CurBufferPtr = BufferEnd;
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  void emitLabel(MCSymbol *Label) override = 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  void *allocateSpace(uintptr_t Size, unsigned Alignment) override {
257    emitAlignment(Alignment);
258    void *Result;
259
260    // Check for buffer overflow.
261    if (Size >= (uintptr_t)(BufferEnd-CurBufferPtr)) {
262      CurBufferPtr = BufferEnd;
263      Result = nullptr;
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  void StartMachineBasicBlock(MachineBasicBlock *MBB) override = 0;
282
283  /// getCurrentPCValue - This returns the address that the next emitted byte
284  /// will be output to.
285  ///
286  uintptr_t getCurrentPCValue() const override {
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 override {
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 override { return true; }
302
303  /// addRelocation - Whenever a relocatable address is needed, it should be
304  /// noted with this interface.
305  void addRelocation(const MachineRelocation &MR) override = 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  uintptr_t getConstantPoolEntryAddress(unsigned Index) const override = 0;
313
314  /// getJumpTableEntryAddress - Return the address of the jump table with index
315  /// 'Index' in the function that last called initJumpTableInfo.
316  ///
317  uintptr_t getJumpTableEntryAddress(unsigned Index) const override = 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  uintptr_t
324    getMachineBasicBlockAddress(MachineBasicBlock *MBB) const override = 0;
325
326  /// getLabelAddress - Return the address of the specified Label, only usable
327  /// after the Label has been emitted.
328  ///
329  uintptr_t getLabelAddress(MCSymbol *Label) const override = 0;
330
331  /// Specifies the MachineModuleInfo object. This is used for exception handling
332  /// purposes.
333  void setModuleInfo(MachineModuleInfo* Info) override = 0;
334
335  /// getLabelLocations - Return the label locations map of the label IDs to
336  /// their address.
337  virtual DenseMap<MCSymbol*, uintptr_t> *getLabelLocations() {
338    return nullptr;
339  }
340};
341
342} // End llvm namespace
343
344#endif
345