JITEmitter.cpp revision c648dabf65c67d20c208ed0b39b9622387e636c7 
1//===-- Emitter.cpp - Write machine code to executable memory -------------===//
2//
3// This file defines a MachineCodeEmitter object that is used by Jello to write
4// machine code to memory and remember where relocatable values lie.
5//
6//===----------------------------------------------------------------------===//
7
8#include "VM.h"
9#include "Config/sys/mman.h"
10#include "llvm/CodeGen/MachineCodeEmitter.h"
11#include "llvm/CodeGen/MachineFunction.h"
12#include "llvm/CodeGen/MachineConstantPool.h"
13#include "llvm/Target/TargetData.h"
14#include "llvm/Module.h"
15#include "Support/Debug.h"
16#include "Support/Statistic.h"
17#include <stdio.h>
18
19namespace {
20  Statistic<> NumBytes("jello", "Number of bytes of machine code compiled");
21  VM *TheVM = 0;
22
23  class Emitter : public MachineCodeEmitter {
24    // CurBlock - The start of the current block of memory.  CurByte - The
25    // current byte being emitted to.
26    unsigned char *CurBlock, *CurByte;
27
28    // When outputting a function stub in the context of some other function, we
29    // save CurBlock and CurByte here.
30    unsigned char *SavedCurBlock, *SavedCurByte;
31
32    // ConstantPoolAddresses - Contains the location for each entry in the
33    // constant pool.
34    std::vector<void*> ConstantPoolAddresses;
35  public:
36    Emitter(VM &vm) { TheVM = &vm; }
37
38    virtual void startFunction(MachineFunction &F);
39    virtual void finishFunction(MachineFunction &F);
40    virtual void emitConstantPool(MachineConstantPool *MCP);
41    virtual void startFunctionStub(const Function &F, unsigned StubSize);
42    virtual void* finishFunctionStub(const Function &F);
43    virtual void emitByte(unsigned char B);
44    virtual void emitWord(unsigned W);
45
46    virtual uint64_t getGlobalValueAddress(GlobalValue *V);
47    virtual uint64_t getGlobalValueAddress(const std::string &Name);
48    virtual uint64_t getConstantPoolEntryAddress(unsigned Entry);
49    virtual uint64_t getCurrentPCValue();
50
51    // forceCompilationOf - Force the compilation of the specified function, and
52    // return its address, because we REALLY need the address now.
53    //
54    // FIXME: This is JIT specific!
55    //
56    virtual uint64_t forceCompilationOf(Function *F);
57  };
58}
59
60MachineCodeEmitter *VM::createEmitter(VM &V) {
61  return new Emitter(V);
62}
63
64
65#define _POSIX_MAPPED_FILES
66#include <unistd.h>
67#include <sys/mman.h>
68
69// FIXME: This should be rewritten to support a real memory manager for
70// executable memory pages!
71static void *getMemory(unsigned NumPages) {
72  void *pa;
73  if (NumPages == 0) return 0;
74  static const long pageSize = sysconf(_SC_PAGESIZE);
75
76#if defined(i386) || defined(__i386__) || defined(__x86__)
77  /* Linux and *BSD tend to have these flags named differently. */
78#if defined(MAP_ANON) && !defined(MAP_ANONYMOUS)
79# define MAP_ANONYMOUS MAP_ANON
80#endif /* defined(MAP_ANON) && !defined(MAP_ANONYMOUS) */
81#define fd  0
82#elif defined(sparc) || defined(__sparc__) || defined(__sparcv9)
83#define fd -1
84#else
85  std::cerr << "This architecture is not supported by the JIT!\n";
86  abort();
87#endif
88  pa = mmap(0, pageSize*NumPages, PROT_READ|PROT_WRITE|PROT_EXEC,
89            MAP_PRIVATE|MAP_ANONYMOUS, fd, 0);
90  if (pa == MAP_FAILED) {
91    perror("mmap");
92    abort();
93  }
94  return pa;
95}
96
97
98void Emitter::startFunction(MachineFunction &F) {
99  CurBlock = (unsigned char *)getMemory(16);
100  CurByte = CurBlock;  // Start writing at the beginning of the fn.
101  TheVM->addGlobalMapping(F.getFunction(), CurBlock);
102}
103
104void Emitter::finishFunction(MachineFunction &F) {
105  ConstantPoolAddresses.clear();
106  NumBytes += CurByte-CurBlock;
107
108  DEBUG(std::cerr << "Finished CodeGen of [" << (void*)CurBlock
109                  << "] Function: " << F.getFunction()->getName()
110                  << ": " << CurByte-CurBlock << " bytes of text\n");
111}
112
113void Emitter::emitConstantPool(MachineConstantPool *MCP) {
114  const std::vector<Constant*> &Constants = MCP->getConstants();
115  for (unsigned i = 0, e = Constants.size(); i != e; ++i) {
116    // For now we just allocate some memory on the heap, this can be
117    // dramatically improved.
118    const Type *Ty = ((Value*)Constants[i])->getType();
119    void *Addr = malloc(TheVM->getTargetData().getTypeSize(Ty));
120    TheVM->InitializeMemory(Constants[i], Addr);
121    ConstantPoolAddresses.push_back(Addr);
122  }
123}
124
125void Emitter::startFunctionStub(const Function &F, unsigned StubSize) {
126  static const long pageSize = sysconf(_SC_PAGESIZE);
127  SavedCurBlock = CurBlock;  SavedCurByte = CurByte;
128  // FIXME: this is a huge waste of memory.
129  CurBlock = (unsigned char *)getMemory((StubSize+pageSize-1)/pageSize);
130  CurByte = CurBlock;  // Start writing at the beginning of the fn.
131}
132
133void *Emitter::finishFunctionStub(const Function &F) {
134  NumBytes += CurByte-CurBlock;
135  DEBUG(std::cerr << "Finished CodeGen of [0x" << std::hex
136                  << (unsigned)(intptr_t)CurBlock
137                  << std::dec << "] Function stub for: " << F.getName()
138                  << ": " << CurByte-CurBlock << " bytes of text\n");
139  std::swap(CurBlock, SavedCurBlock);
140  CurByte = SavedCurByte;
141  return SavedCurBlock;
142}
143
144void Emitter::emitByte(unsigned char B) {
145  *CurByte++ = B;   // Write the byte to memory
146}
147
148void Emitter::emitWord(unsigned W) {
149  // FIXME: This won't work if the endianness of the host and target don't
150  // agree!  (For a JIT this can't happen though.  :)
151  *(unsigned*)CurByte = W;
152  CurByte += sizeof(unsigned);
153}
154
155
156uint64_t Emitter::getGlobalValueAddress(GlobalValue *V) {
157  // Try looking up the function to see if it is already compiled, if not return
158  // 0.
159  return (intptr_t)TheVM->getPointerToGlobalIfAvailable(V);
160}
161uint64_t Emitter::getGlobalValueAddress(const std::string &Name) {
162  return (intptr_t)TheVM->getPointerToNamedFunction(Name);
163}
164
165// getConstantPoolEntryAddress - Return the address of the 'ConstantNum' entry
166// in the constant pool that was last emitted with the 'emitConstantPool'
167// method.
168//
169uint64_t Emitter::getConstantPoolEntryAddress(unsigned ConstantNum) {
170  assert(ConstantNum < ConstantPoolAddresses.size() &&
171	 "Invalid ConstantPoolIndex!");
172  return (intptr_t)ConstantPoolAddresses[ConstantNum];
173}
174
175// getCurrentPCValue - This returns the address that the next emitted byte
176// will be output to.
177//
178uint64_t Emitter::getCurrentPCValue() {
179  return (intptr_t)CurByte;
180}
181
182uint64_t Emitter::forceCompilationOf(Function *F) {
183  return (intptr_t)TheVM->getPointerToFunction(F);
184}
185
186// getPointerToNamedFunction - This function is used as a global wrapper to
187// VM::getPointerToNamedFunction for the purpose of resolving symbols when
188// bugpoint is debugging the JIT. In that scenario, we are loading an .so and
189// need to resolve function(s) that are being mis-codegenerated, so we need to
190// resolve their addresses at runtime, and this is the way to do it.
191extern "C" {
192  void *getPointerToNamedFunction(const char *Name) {
193    Module &M = TheVM->getModule();
194    if (Function *F = M.getNamedFunction(Name))
195      return TheVM->getPointerToFunction(F);
196    return TheVM->getPointerToNamedFunction(Name);
197  }
198}
199