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 //===----------------------------------------------------------------------===//
9 #include "llvm/CodeGen/MachineCodeEmitter.h"
10 #include "llvm/CodeGen/MachineFunction.h"
11 #include "llvm/CodeGen/MachineConstantPool.h"
12 #include "llvm/Target/TargetData.h"
13 #include "llvm/Function.h"
14 #include "Support/Statistic.h"
19 Statistic<> NumBytes("jello", "Number of bytes of machine code compiled");
21 class Emitter : public MachineCodeEmitter {
22 // CurBlock - The start of the current block of memory. CurByte - The
23 // current byte being emitted to.
24 unsigned char *CurBlock, *CurByte;
26 // When outputting a function stub in the context of some other function, we
27 // save CurBlock and CurByte here.
28 unsigned char *SavedCurBlock, *SavedCurByte;
30 // ConstantPoolAddresses - Contains the location for each entry in the
32 std::vector<void*> ConstantPoolAddresses;
34 Emitter(VM &vm) { TheVM = &vm; }
36 virtual void startFunction(MachineFunction &F);
37 virtual void finishFunction(MachineFunction &F);
38 virtual void emitConstantPool(MachineConstantPool *MCP);
39 virtual void startFunctionStub(const Function &F, unsigned StubSize);
40 virtual void* finishFunctionStub(const Function &F);
41 virtual void emitByte(unsigned char B);
42 virtual void emitWord(unsigned W);
44 virtual uint64_t getGlobalValueAddress(GlobalValue *V);
45 virtual uint64_t getGlobalValueAddress(const std::string &Name);
46 virtual uint64_t getConstantPoolEntryAddress(unsigned Entry);
47 virtual uint64_t getCurrentPCValue();
49 // forceCompilationOf - Force the compilation of the specified function, and
50 // return its address, because we REALLY need the address now.
52 // FIXME: This is JIT specific!
54 virtual uint64_t forceCompilationOf(Function *F);
58 MachineCodeEmitter *VM::createX86Emitter(VM &V) {
59 return new Emitter(V);
63 #define _POSIX_MAPPED_FILES
67 // FIXME: This should be rewritten to support a real memory manager for
68 // executable memory pages!
69 static void *getMemory(unsigned NumPages) {
70 return mmap(0, 4096*NumPages, PROT_READ|PROT_WRITE|PROT_EXEC,
71 MAP_PRIVATE|MAP_ANONYMOUS, 0, 0);
75 void Emitter::startFunction(MachineFunction &F) {
76 CurBlock = (unsigned char *)getMemory(16);
77 CurByte = CurBlock; // Start writing at the beginning of the fn.
78 TheVM->addGlobalMapping(F.getFunction(), CurBlock);
81 void Emitter::finishFunction(MachineFunction &F) {
82 ConstantPoolAddresses.clear();
83 NumBytes += CurByte-CurBlock;
85 DEBUG(std::cerr << "Finished CodeGen of [0x" << std::hex
86 << (unsigned)(intptr_t)CurBlock
87 << std::dec << "] Function: " << F.getFunction()->getName()
88 << ": " << CurByte-CurBlock << " bytes of text\n");
91 void Emitter::emitConstantPool(MachineConstantPool *MCP) {
92 const std::vector<Constant*> &Constants = MCP->getConstants();
93 for (unsigned i = 0, e = Constants.size(); i != e; ++i) {
94 // For now we just allocate some memory on the heap, this can be
95 // dramatically improved.
96 const Type *Ty = ((Value*)Constants[i])->getType();
97 void *Addr = malloc(TheVM->getTargetData().getTypeSize(Ty));
98 TheVM->InitializeMemory(Constants[i], Addr);
99 ConstantPoolAddresses.push_back(Addr);
103 void Emitter::startFunctionStub(const Function &F, unsigned StubSize) {
104 SavedCurBlock = CurBlock; SavedCurByte = CurByte;
105 // FIXME: this is a huge waste of memory.
106 CurBlock = (unsigned char *)getMemory((StubSize+4095)/4096);
107 CurByte = CurBlock; // Start writing at the beginning of the fn.
110 void *Emitter::finishFunctionStub(const Function &F) {
111 NumBytes += CurByte-CurBlock;
112 DEBUG(std::cerr << "Finished CodeGen of [0x" << std::hex
113 << (unsigned)(intptr_t)CurBlock
114 << std::dec << "] Function stub for: " << F.getName()
115 << ": " << CurByte-CurBlock << " bytes of text\n");
116 std::swap(CurBlock, SavedCurBlock);
117 CurByte = SavedCurByte;
118 return SavedCurBlock;
121 void Emitter::emitByte(unsigned char B) {
122 *CurByte++ = B; // Write the byte to memory
125 void Emitter::emitWord(unsigned W) {
126 // FIXME: This won't work if the endianness of the host and target don't
127 // agree! (For a JIT this can't happen though. :)
128 *(unsigned*)CurByte = W;
129 CurByte += sizeof(unsigned);
133 uint64_t Emitter::getGlobalValueAddress(GlobalValue *V) {
134 // Try looking up the function to see if it is already compiled, if not return
136 return (intptr_t)TheVM->getPointerToGlobalIfAvailable(V);
138 uint64_t Emitter::getGlobalValueAddress(const std::string &Name) {
139 return (intptr_t)TheVM->getPointerToNamedFunction(Name);
142 // getConstantPoolEntryAddress - Return the address of the 'ConstantNum' entry
143 // in the constant pool that was last emitted with the 'emitConstantPool'
146 uint64_t Emitter::getConstantPoolEntryAddress(unsigned ConstantNum) {
147 assert(ConstantNum < ConstantPoolAddresses.size() &&
148 "Invalid ConstantPoolIndex!");
149 return (intptr_t)ConstantPoolAddresses[ConstantNum];
152 // getCurrentPCValue - This returns the address that the next emitted byte
153 // will be output to.
155 uint64_t Emitter::getCurrentPCValue() {
156 return (intptr_t)CurByte;
159 uint64_t Emitter::forceCompilationOf(Function *F) {
160 return (intptr_t)TheVM->getPointerToFunction(F);
166 // emitPCRelativeDisp - For functions, just output a displacement that will
167 // cause a reference to the zero page, which will cause a seg-fault, causing
168 // things to get resolved on demand. Keep track of these markers.
170 // For basic block references, keep track of where the references are so they
171 // may be patched up when the basic block is defined.
173 void Emitter::emitPCRelativeDisp(Value *V) {
174 BasicBlock *BB = cast<BasicBlock>(V); // Keep track of reference...
175 BBRefs.push_back(std::make_pair(BB, (unsigned*)CurByte));
179 // emitAddress - Emit an address in either direct or PCRelative form...
181 void Emitter::emitAddress(void *Addr, bool isPCRelative) {
183 *(intptr_t*)CurByte = (intptr_t)Addr - (intptr_t)CurByte-4;
185 *(void**)CurByte = Addr;
190 void Emitter::emitGlobalAddress(GlobalValue *V, bool isPCRelative) {
191 if (isPCRelative) { // must be a call, this is a major hack!
192 // Try looking up the function to see if it is already compiled!
193 if (void *Addr = TheVM->getPointerToGlobalIfAvailable(V)) {
194 emitAddress(Addr, isPCRelative);
195 } else { // Function has not yet been code generated!
196 TheVM->addFunctionRef(CurByte, cast<Function>(V));
198 // Delayed resolution...
199 emitAddress((void*)VM::CompilationCallback, isPCRelative);
202 emitAddress(TheVM->getPointerToGlobal(V), isPCRelative);
206 void Emitter::emitFunctionConstantValueAddress(unsigned ConstantNum,
208 assert(ConstantNum < ConstantPoolAddresses.size() &&
209 "Invalid ConstantPoolIndex!");
210 *(void**)CurByte = (char*)ConstantPoolAddresses[ConstantNum]+Offset;