1 //===-- Emitter.cpp - Write machine code to executable memory -------------===//
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.
6 //===----------------------------------------------------------------------===//
8 #define DEBUG_TYPE "jit"
9 #ifndef _POSIX_MAPPED_FILES
10 #define _POSIX_MAPPED_FILES
13 #include "llvm/CodeGen/MachineCodeEmitter.h"
14 #include "llvm/CodeGen/MachineFunction.h"
15 #include "llvm/CodeGen/MachineConstantPool.h"
16 #include "llvm/Target/TargetData.h"
17 #include "llvm/Module.h"
18 #include "Support/Debug.h"
19 #include "Support/Statistic.h"
20 #include "Config/unistd.h"
21 #include "Config/sys/mman.h"
24 Statistic<> NumBytes("jello", "Number of bytes of machine code compiled");
27 /// JITMemoryManager - Manage memory for the JIT code generation in a logical,
28 /// sane way. This splits a large block of MAP_NORESERVE'd memory into two
29 /// sections, one for function stubs, one for the functions themselves. We
30 /// have to do this because we may need to emit a function stub while in the
31 /// middle of emitting a function, and we don't know how large the function we
32 /// are emitting is. This never bothers to release the memory, because when
33 /// we are ready to destroy the JIT, the program exits.
34 class JITMemoryManager {
35 unsigned char *MemBase; // Base of block of memory, start of stub mem
36 unsigned char *FunctionBase; // Start of the function body area
37 unsigned char *CurStubPtr, *CurFunctionPtr;
41 inline unsigned char *allocateStub(unsigned StubSize);
42 inline unsigned char *startFunctionBody();
43 inline void endFunctionBody(unsigned char *FunctionEnd);
47 // getMemory - Return a pointer to the specified number of bytes, which is
48 // mapped as executable readable and writable.
49 static void *getMemory(unsigned NumBytes) {
50 if (NumBytes == 0) return 0;
51 static const long pageSize = sysconf(_SC_PAGESIZE);
52 unsigned NumPages = (NumBytes+pageSize-1)/pageSize;
54 #if defined(i386) || defined(__i386__) || defined(__x86__)
55 /* Linux and *BSD tend to have these flags named differently. */
56 #if defined(MAP_ANON) && !defined(MAP_ANONYMOUS)
57 # define MAP_ANONYMOUS MAP_ANON
58 #endif /* defined(MAP_ANON) && !defined(MAP_ANONYMOUS) */
59 #elif defined(sparc) || defined(__sparc__) || defined(__sparcv9)
62 std::cerr << "This architecture is not supported by the JIT!\n";
66 #if defined(__linux__)
72 unsigned mmapFlags = MAP_PRIVATE|MAP_ANONYMOUS;
74 mmapFlags |= MAP_NORESERVE;
77 void *pa = mmap(0, pageSize*NumPages, PROT_READ|PROT_WRITE|PROT_EXEC,
79 if (pa == MAP_FAILED) {
86 JITMemoryManager::JITMemoryManager() {
87 // Allocate a 16M block of memory...
88 MemBase = (unsigned char*)getMemory(16 << 20);
89 FunctionBase = MemBase + 512*1024; // Use 512k for stubs
91 // Allocate stubs backwards from the function base, allocate functions forward
92 // from the function base.
93 CurStubPtr = CurFunctionPtr = FunctionBase;
96 unsigned char *JITMemoryManager::allocateStub(unsigned StubSize) {
97 CurStubPtr -= StubSize;
98 if (CurStubPtr < MemBase) {
99 std::cerr << "JIT ran out of memory for function stubs!\n";
105 unsigned char *JITMemoryManager::startFunctionBody() {
106 // Round up to an even multiple of 4 bytes, this should eventually be target
108 return (unsigned char*)(((intptr_t)CurFunctionPtr + 3) & ~3);
111 void JITMemoryManager::endFunctionBody(unsigned char *FunctionEnd) {
112 assert(FunctionEnd > CurFunctionPtr);
113 CurFunctionPtr = FunctionEnd;
119 /// Emitter - The JIT implementation of the MachineCodeEmitter, which is used
120 /// to output functions to memory for execution.
121 class Emitter : public MachineCodeEmitter {
122 JITMemoryManager MemMgr;
124 // CurBlock - The start of the current block of memory. CurByte - The
125 // current byte being emitted to.
126 unsigned char *CurBlock, *CurByte;
128 // When outputting a function stub in the context of some other function, we
129 // save CurBlock and CurByte here.
130 unsigned char *SavedCurBlock, *SavedCurByte;
132 // ConstantPoolAddresses - Contains the location for each entry in the
134 std::vector<void*> ConstantPoolAddresses;
136 Emitter(VM &vm) { TheVM = &vm; }
138 virtual void startFunction(MachineFunction &F);
139 virtual void finishFunction(MachineFunction &F);
140 virtual void emitConstantPool(MachineConstantPool *MCP);
141 virtual void startFunctionStub(const Function &F, unsigned StubSize);
142 virtual void* finishFunctionStub(const Function &F);
143 virtual void emitByte(unsigned char B);
144 virtual void emitWord(unsigned W);
146 virtual uint64_t getGlobalValueAddress(GlobalValue *V);
147 virtual uint64_t getGlobalValueAddress(const std::string &Name);
148 virtual uint64_t getConstantPoolEntryAddress(unsigned Entry);
149 virtual uint64_t getCurrentPCValue();
151 // forceCompilationOf - Force the compilation of the specified function, and
152 // return its address, because we REALLY need the address now.
154 // FIXME: This is JIT specific!
156 virtual uint64_t forceCompilationOf(Function *F);
160 MachineCodeEmitter *VM::createEmitter(VM &V) {
161 return new Emitter(V);
164 void Emitter::startFunction(MachineFunction &F) {
165 CurByte = CurBlock = MemMgr.startFunctionBody();
166 TheVM->addGlobalMapping(F.getFunction(), CurBlock);
169 void Emitter::finishFunction(MachineFunction &F) {
170 MemMgr.endFunctionBody(CurByte);
171 ConstantPoolAddresses.clear();
172 NumBytes += CurByte-CurBlock;
174 DEBUG(std::cerr << "Finished CodeGen of [" << (void*)CurBlock
175 << "] Function: " << F.getFunction()->getName()
176 << ": " << CurByte-CurBlock << " bytes of text\n");
179 void Emitter::emitConstantPool(MachineConstantPool *MCP) {
180 const std::vector<Constant*> &Constants = MCP->getConstants();
181 for (unsigned i = 0, e = Constants.size(); i != e; ++i) {
182 // For now we just allocate some memory on the heap, this can be
183 // dramatically improved.
184 const Type *Ty = ((Value*)Constants[i])->getType();
185 void *Addr = malloc(TheVM->getTargetData().getTypeSize(Ty));
186 TheVM->InitializeMemory(Constants[i], Addr);
187 ConstantPoolAddresses.push_back(Addr);
191 void Emitter::startFunctionStub(const Function &F, unsigned StubSize) {
192 SavedCurBlock = CurBlock; SavedCurByte = CurByte;
193 CurByte = CurBlock = MemMgr.allocateStub(StubSize);
196 void *Emitter::finishFunctionStub(const Function &F) {
197 NumBytes += CurByte-CurBlock;
198 DEBUG(std::cerr << "Finished CodeGen of [0x" << std::hex
199 << (unsigned)(intptr_t)CurBlock
200 << std::dec << "] Function stub for: " << F.getName()
201 << ": " << CurByte-CurBlock << " bytes of text\n");
202 std::swap(CurBlock, SavedCurBlock);
203 CurByte = SavedCurByte;
204 return SavedCurBlock;
207 void Emitter::emitByte(unsigned char B) {
208 *CurByte++ = B; // Write the byte to memory
211 void Emitter::emitWord(unsigned W) {
212 // This won't work if the endianness of the host and target don't agree! (For
213 // a JIT this can't happen though. :)
214 *(unsigned*)CurByte = W;
215 CurByte += sizeof(unsigned);
218 uint64_t Emitter::getGlobalValueAddress(GlobalValue *V) {
219 // Try looking up the function to see if it is already compiled, if not return
221 return (intptr_t)TheVM->getPointerToGlobalIfAvailable(V);
223 uint64_t Emitter::getGlobalValueAddress(const std::string &Name) {
224 return (intptr_t)TheVM->getPointerToNamedFunction(Name);
227 // getConstantPoolEntryAddress - Return the address of the 'ConstantNum' entry
228 // in the constant pool that was last emitted with the 'emitConstantPool'
231 uint64_t Emitter::getConstantPoolEntryAddress(unsigned ConstantNum) {
232 assert(ConstantNum < ConstantPoolAddresses.size() &&
233 "Invalid ConstantPoolIndex!");
234 return (intptr_t)ConstantPoolAddresses[ConstantNum];
237 // getCurrentPCValue - This returns the address that the next emitted byte
238 // will be output to.
240 uint64_t Emitter::getCurrentPCValue() {
241 return (intptr_t)CurByte;
244 uint64_t Emitter::forceCompilationOf(Function *F) {
245 return (intptr_t)TheVM->getPointerToFunction(F);
248 // getPointerToNamedFunction - This function is used as a global wrapper to
249 // VM::getPointerToNamedFunction for the purpose of resolving symbols when
250 // bugpoint is debugging the JIT. In that scenario, we are loading an .so and
251 // need to resolve function(s) that are being mis-codegenerated, so we need to
252 // resolve their addresses at runtime, and this is the way to do it.
254 void *getPointerToNamedFunction(const char *Name) {
255 Module &M = TheVM->getModule();
256 if (Function *F = M.getNamedFunction(Name))
257 return TheVM->getPointerToFunction(F);
258 return TheVM->getPointerToNamedFunction(Name);