1 //===-- JITEmitter.cpp - Write machine code to executable memory ----------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines a MachineCodeEmitter object that is used by the JIT to
11 // write machine code to memory and remember where relocatable values are.
13 //===----------------------------------------------------------------------===//
15 #define DEBUG_TYPE "jit"
17 #include "llvm/Constant.h"
18 #include "llvm/Module.h"
19 #include "llvm/Type.h"
20 #include "llvm/CodeGen/MachineCodeEmitter.h"
21 #include "llvm/CodeGen/MachineFunction.h"
22 #include "llvm/CodeGen/MachineConstantPool.h"
23 #include "llvm/CodeGen/MachineJumpTableInfo.h"
24 #include "llvm/CodeGen/MachineRelocation.h"
25 #include "llvm/ExecutionEngine/GenericValue.h"
26 #include "llvm/Target/TargetData.h"
27 #include "llvm/Target/TargetJITInfo.h"
28 #include "llvm/Support/Debug.h"
29 #include "llvm/Support/MutexGuard.h"
30 #include "llvm/ADT/Statistic.h"
31 #include "llvm/System/Memory.h"
37 Statistic<> NumBytes("jit", "Number of bytes of machine code compiled");
38 Statistic<> NumRelos("jit", "Number of relocations applied");
43 //===----------------------------------------------------------------------===//
44 // JITMemoryManager code.
47 /// MemoryRangeHeader - For a range of memory, this is the header that we put
48 /// on the block of memory. It is carefully crafted to be one word of memory.
49 /// Allocated blocks have just this header, free'd blocks have FreeRangeHeader
50 /// which starts with this.
51 struct FreeRangeHeader;
52 struct MemoryRangeHeader {
53 /// ThisAllocated - This is true if this block is currently allocated. If
54 /// not, this can be converted to a FreeRangeHeader.
55 intptr_t ThisAllocated : 1;
57 /// PrevAllocated - Keep track of whether the block immediately before us is
58 /// allocated. If not, the word immediately before this header is the size
59 /// of the previous block.
60 intptr_t PrevAllocated : 1;
62 /// BlockSize - This is the size in bytes of this memory block,
63 /// including this header.
64 uintptr_t BlockSize : (sizeof(intptr_t)*8 - 2);
67 /// getBlockAfter - Return the memory block immediately after this one.
69 MemoryRangeHeader &getBlockAfter() const {
70 return *(MemoryRangeHeader*)((char*)this+BlockSize);
73 /// getFreeBlockBefore - If the block before this one is free, return it,
74 /// otherwise return null.
75 FreeRangeHeader *getFreeBlockBefore() const {
76 if (PrevAllocated) return 0;
77 intptr_t PrevSize = ((intptr_t *)this)[-1];
78 return (FreeRangeHeader*)((char*)this-PrevSize);
81 /// FreeBlock - Turn an allocated block into a free block, adjusting
82 /// bits in the object headers, and adding an end of region memory block.
83 FreeRangeHeader *FreeBlock(FreeRangeHeader *FreeList);
85 /// TrimAllocationToSize - If this allocated block is significantly larger
86 /// than NewSize, split it into two pieces (where the former is NewSize
87 /// bytes, including the header), and add the new block to the free list.
88 FreeRangeHeader *TrimAllocationToSize(FreeRangeHeader *FreeList,
92 /// FreeRangeHeader - For a memory block that isn't already allocated, this
93 /// keeps track of the current block and has a pointer to the next free block.
94 /// Free blocks are kept on a circularly linked list.
95 struct FreeRangeHeader : public MemoryRangeHeader {
96 FreeRangeHeader *Prev;
97 FreeRangeHeader *Next;
99 /// getMinBlockSize - Get the minimum size for a memory block. Blocks
100 /// smaller than this size cannot be created.
101 static unsigned getMinBlockSize() {
102 return sizeof(FreeRangeHeader)+sizeof(intptr_t);
105 /// SetEndOfBlockSizeMarker - The word at the end of every free block is
106 /// known to be the size of the free block. Set it for this block.
107 void SetEndOfBlockSizeMarker() {
108 void *EndOfBlock = (char*)this + BlockSize;
109 ((intptr_t *)EndOfBlock)[-1] = BlockSize;
112 FreeRangeHeader *RemoveFromFreeList() {
113 assert(Next->Prev == this && Prev->Next == this && "Freelist broken!");
115 return Prev->Next = Next;
118 void AddToFreeList(FreeRangeHeader *FreeList) {
120 Prev = FreeList->Prev;
125 /// GrowBlock - The block after this block just got deallocated. Merge it
126 /// into the current block.
127 void GrowBlock(uintptr_t NewSize);
129 /// AllocateBlock - Mark this entire block allocated, updating freelists
130 /// etc. This returns a pointer to the circular free-list.
131 FreeRangeHeader *AllocateBlock();
136 /// AllocateBlock - Mark this entire block allocated, updating freelists
137 /// etc. This returns a pointer to the circular free-list.
138 FreeRangeHeader *FreeRangeHeader::AllocateBlock() {
139 assert(!ThisAllocated && !getBlockAfter().PrevAllocated &&
140 "Cannot allocate an allocated block!");
141 // Mark this block allocated.
143 getBlockAfter().PrevAllocated = 1;
145 // Remove it from the free list.
146 return RemoveFromFreeList();
149 /// FreeBlock - Turn an allocated block into a free block, adjusting
150 /// bits in the object headers, and adding an end of region memory block.
151 /// If possible, coallesce this block with neighboring blocks. Return the
152 /// FreeRangeHeader to allocate from.
153 FreeRangeHeader *MemoryRangeHeader::FreeBlock(FreeRangeHeader *FreeList) {
154 MemoryRangeHeader *FollowingBlock = &getBlockAfter();
155 assert(ThisAllocated && "This block is already allocated!");
156 assert(FollowingBlock->PrevAllocated && "Flags out of sync!");
158 FreeRangeHeader *FreeListToReturn = FreeList;
160 // If the block after this one is free, merge it into this block.
161 if (!FollowingBlock->ThisAllocated) {
162 FreeRangeHeader &FollowingFreeBlock = *(FreeRangeHeader *)FollowingBlock;
163 // "FreeList" always needs to be a valid free block. If we're about to
164 // coallesce with it, update our notion of what the free list is.
165 if (&FollowingFreeBlock == FreeList) {
166 FreeList = FollowingFreeBlock.Next;
167 FreeListToReturn = 0;
168 assert(&FollowingFreeBlock != FreeList && "No tombstone block?");
170 FollowingFreeBlock.RemoveFromFreeList();
172 // Include the following block into this one.
173 BlockSize += FollowingFreeBlock.BlockSize;
174 FollowingBlock = &FollowingFreeBlock.getBlockAfter();
176 // Tell the block after the block we are coallescing that this block is
178 FollowingBlock->PrevAllocated = 1;
181 assert(FollowingBlock->ThisAllocated && "Missed coallescing?");
183 if (FreeRangeHeader *PrevFreeBlock = getFreeBlockBefore()) {
184 PrevFreeBlock->GrowBlock(PrevFreeBlock->BlockSize + BlockSize);
185 return FreeListToReturn ? FreeListToReturn : PrevFreeBlock;
188 // Otherwise, mark this block free.
189 FreeRangeHeader &FreeBlock = *(FreeRangeHeader*)this;
190 FollowingBlock->PrevAllocated = 0;
191 FreeBlock.ThisAllocated = 0;
193 // Link this into the linked list of free blocks.
194 FreeBlock.AddToFreeList(FreeList);
196 // Add a marker at the end of the block, indicating the size of this free
198 FreeBlock.SetEndOfBlockSizeMarker();
199 return FreeListToReturn ? FreeListToReturn : &FreeBlock;
202 /// GrowBlock - The block after this block just got deallocated. Merge it
203 /// into the current block.
204 void FreeRangeHeader::GrowBlock(uintptr_t NewSize) {
205 assert(NewSize > BlockSize && "Not growing block?");
207 SetEndOfBlockSizeMarker();
208 getBlockAfter().PrevAllocated = 0;
211 /// TrimAllocationToSize - If this allocated block is significantly larger
212 /// than NewSize, split it into two pieces (where the former is NewSize
213 /// bytes, including the header), and add the new block to the free list.
214 FreeRangeHeader *MemoryRangeHeader::
215 TrimAllocationToSize(FreeRangeHeader *FreeList, uint64_t NewSize) {
216 assert(ThisAllocated && getBlockAfter().PrevAllocated &&
217 "Cannot deallocate part of an allocated block!");
219 // Round up size for alignment of header.
220 unsigned HeaderAlign = __alignof(FreeRangeHeader);
221 NewSize = (NewSize+ (HeaderAlign-1)) & ~(HeaderAlign-1);
223 // Size is now the size of the block we will remove from the start of the
225 assert(NewSize <= BlockSize &&
226 "Allocating more space from this block than exists!");
228 // If splitting this block will cause the remainder to be too small, do not
230 if (BlockSize <= NewSize+FreeRangeHeader::getMinBlockSize())
233 // Otherwise, we splice the required number of bytes out of this block, form
234 // a new block immediately after it, then mark this block allocated.
235 MemoryRangeHeader &FormerNextBlock = getBlockAfter();
237 // Change the size of this block.
240 // Get the new block we just sliced out and turn it into a free block.
241 FreeRangeHeader &NewNextBlock = (FreeRangeHeader &)getBlockAfter();
242 NewNextBlock.BlockSize = (char*)&FormerNextBlock - (char*)&NewNextBlock;
243 NewNextBlock.ThisAllocated = 0;
244 NewNextBlock.PrevAllocated = 1;
245 NewNextBlock.SetEndOfBlockSizeMarker();
246 FormerNextBlock.PrevAllocated = 0;
247 NewNextBlock.AddToFreeList(FreeList);
248 return &NewNextBlock;
253 /// JITMemoryManager - Manage memory for the JIT code generation in a logical,
254 /// sane way. This splits a large block of MAP_NORESERVE'd memory into two
255 /// sections, one for function stubs, one for the functions themselves. We
256 /// have to do this because we may need to emit a function stub while in the
257 /// middle of emitting a function, and we don't know how large the function we
258 /// are emitting is. This never bothers to release the memory, because when
259 /// we are ready to destroy the JIT, the program exits.
260 class JITMemoryManager {
261 std::vector<sys::MemoryBlock> Blocks; // Memory blocks allocated by the JIT
262 FreeRangeHeader *FreeMemoryList; // Circular list of free blocks.
264 // When emitting code into a memory block, this is the block.
265 MemoryRangeHeader *CurBlock;
267 unsigned char *CurStubPtr, *StubBase;
268 unsigned char *GOTBase; // Target Specific reserved memory
270 // Centralize memory block allocation.
271 sys::MemoryBlock getNewMemoryBlock(unsigned size);
273 std::map<const Function*, MemoryRangeHeader*> FunctionBlocks;
275 JITMemoryManager(bool useGOT);
278 inline unsigned char *allocateStub(unsigned StubSize);
280 /// startFunctionBody - When a function starts, allocate a block of free
281 /// executable memory, returning a pointer to it and its actual size.
282 unsigned char *startFunctionBody(uintptr_t &ActualSize) {
283 CurBlock = FreeMemoryList;
285 // Allocate the entire memory block.
286 FreeMemoryList = FreeMemoryList->AllocateBlock();
287 ActualSize = CurBlock->BlockSize-sizeof(MemoryRangeHeader);
288 return (unsigned char *)(CurBlock+1);
291 /// endFunctionBody - The function F is now allocated, and takes the memory
292 /// in the range [FunctionStart,FunctionEnd).
293 void endFunctionBody(const Function *F, unsigned char *FunctionStart,
294 unsigned char *FunctionEnd) {
295 assert(FunctionEnd > FunctionStart);
296 assert(FunctionStart == (unsigned char *)(CurBlock+1) &&
297 "Mismatched function start/end!");
299 uintptr_t BlockSize = FunctionEnd - (unsigned char *)CurBlock;
300 FunctionBlocks[F] = CurBlock;
302 // Release the memory at the end of this block that isn't needed.
303 FreeMemoryList =CurBlock->TrimAllocationToSize(FreeMemoryList, BlockSize);
306 unsigned char *getGOTBase() const {
309 bool isManagingGOT() const {
310 return GOTBase != NULL;
313 /// deallocateMemForFunction - Deallocate all memory for the specified
315 void deallocateMemForFunction(const Function *F) {
316 std::map<const Function*, MemoryRangeHeader*>::iterator
317 I = FunctionBlocks.find(F);
318 if (I == FunctionBlocks.end()) return;
320 // Find the block that is allocated for this function.
321 MemoryRangeHeader *MemRange = I->second;
322 assert(MemRange->ThisAllocated && "Block isn't allocated!");
324 // Fill the buffer with garbage!
325 DEBUG(memset(MemRange+1, 0xCD, MemRange->BlockSize-sizeof(*MemRange)));
328 FreeMemoryList = MemRange->FreeBlock(FreeMemoryList);
330 // Finally, remove this entry from FunctionBlocks.
331 FunctionBlocks.erase(I);
336 JITMemoryManager::JITMemoryManager(bool useGOT) {
337 // Allocate a 16M block of memory for functions.
338 sys::MemoryBlock MemBlock = getNewMemoryBlock(16 << 20);
340 unsigned char *MemBase = reinterpret_cast<unsigned char*>(MemBlock.base());
342 // Allocate stubs backwards from the base, allocate functions forward
345 CurStubPtr = MemBase + 512*1024; // Use 512k for stubs, working backwards.
347 // We set up the memory chunk with 4 mem regions, like this:
349 // [ Free #0 ] -> Large space to allocate functions from.
350 // [ Allocated #1 ] -> Tiny space to separate regions.
351 // [ Free #2 ] -> Tiny space so there is always at least 1 free block.
352 // [ Allocated #3 ] -> Tiny space to prevent looking past end of block.
355 // The last three blocks are never deallocated or touched.
357 // Add MemoryRangeHeader to the end of the memory region, indicating that
358 // the space after the block of memory is allocated. This is block #3.
359 MemoryRangeHeader *Mem3 = (MemoryRangeHeader*)(MemBase+MemBlock.size())-1;
360 Mem3->ThisAllocated = 1;
361 Mem3->PrevAllocated = 0;
364 /// Add a tiny free region so that the free list always has one entry.
365 FreeRangeHeader *Mem2 =
366 (FreeRangeHeader *)(((char*)Mem3)-FreeRangeHeader::getMinBlockSize());
367 Mem2->ThisAllocated = 0;
368 Mem2->PrevAllocated = 1;
369 Mem2->BlockSize = FreeRangeHeader::getMinBlockSize();
370 Mem2->SetEndOfBlockSizeMarker();
371 Mem2->Prev = Mem2; // Mem2 *is* the free list for now.
374 /// Add a tiny allocated region so that Mem2 is never coallesced away.
375 MemoryRangeHeader *Mem1 = (MemoryRangeHeader*)Mem2-1;
376 Mem1->ThisAllocated = 1;
377 Mem1->PrevAllocated = 0;
378 Mem1->BlockSize = (char*)Mem2 - (char*)Mem1;
380 // Add a FreeRangeHeader to the start of the function body region, indicating
381 // that the space is free. Mark the previous block allocated so we never look
383 FreeRangeHeader *Mem0 = (FreeRangeHeader*)CurStubPtr;
384 Mem0->ThisAllocated = 0;
385 Mem0->PrevAllocated = 1;
386 Mem0->BlockSize = (char*)Mem1-(char*)Mem0;
387 Mem0->SetEndOfBlockSizeMarker();
388 Mem0->AddToFreeList(Mem2);
390 // Start out with the freelist pointing to Mem0.
391 FreeMemoryList = Mem0;
395 if (useGOT) GOTBase = new unsigned char[sizeof(void*) * 8192];
398 JITMemoryManager::~JITMemoryManager() {
399 for (unsigned i = 0, e = Blocks.size(); i != e; ++i)
400 sys::Memory::ReleaseRWX(Blocks[i]);
406 unsigned char *JITMemoryManager::allocateStub(unsigned StubSize) {
407 CurStubPtr -= StubSize;
408 if (CurStubPtr < StubBase) {
409 // FIXME: allocate a new block
410 std::cerr << "JIT ran out of memory for function stubs!\n";
416 sys::MemoryBlock JITMemoryManager::getNewMemoryBlock(unsigned size) {
417 // Allocate a new block close to the last one.
418 const sys::MemoryBlock *BOld = Blocks.empty() ? 0 : &Blocks.front();
420 sys::MemoryBlock B = sys::Memory::AllocateRWX(size, BOld, &ErrMsg);
422 std::cerr << "Allocation failed when allocating new memory in the JIT\n";
423 std::cerr << ErrMsg << "\n";
430 //===----------------------------------------------------------------------===//
431 // JIT lazy compilation code.
434 class JITResolverState {
436 /// FunctionToStubMap - Keep track of the stub created for a particular
437 /// function so that we can reuse them if necessary.
438 std::map<Function*, void*> FunctionToStubMap;
440 /// StubToFunctionMap - Keep track of the function that each stub
442 std::map<void*, Function*> StubToFunctionMap;
445 std::map<Function*, void*>& getFunctionToStubMap(const MutexGuard& locked) {
446 assert(locked.holds(TheJIT->lock));
447 return FunctionToStubMap;
450 std::map<void*, Function*>& getStubToFunctionMap(const MutexGuard& locked) {
451 assert(locked.holds(TheJIT->lock));
452 return StubToFunctionMap;
456 /// JITResolver - Keep track of, and resolve, call sites for functions that
457 /// have not yet been compiled.
459 /// MCE - The MachineCodeEmitter to use to emit stubs with.
460 MachineCodeEmitter &MCE;
462 /// LazyResolverFn - The target lazy resolver function that we actually
463 /// rewrite instructions to use.
464 TargetJITInfo::LazyResolverFn LazyResolverFn;
466 JITResolverState state;
468 /// ExternalFnToStubMap - This is the equivalent of FunctionToStubMap for
469 /// external functions.
470 std::map<void*, void*> ExternalFnToStubMap;
472 //map addresses to indexes in the GOT
473 std::map<void*, unsigned> revGOTMap;
474 unsigned nextGOTIndex;
477 JITResolver(MachineCodeEmitter &mce) : MCE(mce), nextGOTIndex(0) {
479 TheJIT->getJITInfo().getLazyResolverFunction(JITCompilerFn);
482 /// getFunctionStub - This returns a pointer to a function stub, creating
483 /// one on demand as needed.
484 void *getFunctionStub(Function *F);
486 /// getExternalFunctionStub - Return a stub for the function at the
487 /// specified address, created lazily on demand.
488 void *getExternalFunctionStub(void *FnAddr);
490 /// AddCallbackAtLocation - If the target is capable of rewriting an
491 /// instruction without the use of a stub, record the location of the use so
492 /// we know which function is being used at the location.
493 void *AddCallbackAtLocation(Function *F, void *Location) {
494 MutexGuard locked(TheJIT->lock);
495 /// Get the target-specific JIT resolver function.
496 state.getStubToFunctionMap(locked)[Location] = F;
497 return (void*)(intptr_t)LazyResolverFn;
500 /// getGOTIndexForAddress - Return a new or existing index in the GOT for
501 /// and address. This function only manages slots, it does not manage the
502 /// contents of the slots or the memory associated with the GOT.
503 unsigned getGOTIndexForAddr(void* addr);
505 /// JITCompilerFn - This function is called to resolve a stub to a compiled
506 /// address. If the LLVM Function corresponding to the stub has not yet
507 /// been compiled, this function compiles it first.
508 static void *JITCompilerFn(void *Stub);
512 /// getJITResolver - This function returns the one instance of the JIT resolver.
514 static JITResolver &getJITResolver(MachineCodeEmitter *MCE = 0) {
515 static JITResolver TheJITResolver(*MCE);
516 return TheJITResolver;
519 #if (defined(__POWERPC__) || defined (__ppc__) || defined(_POWER)) && \
521 extern "C" void sys_icache_invalidate(const void *Addr, size_t len);
524 /// synchronizeICache - On some targets, the JIT emitted code must be
525 /// explicitly refetched to ensure correct execution.
526 static void synchronizeICache(const void *Addr, size_t len) {
527 #if (defined(__POWERPC__) || defined (__ppc__) || defined(_POWER)) && \
529 sys_icache_invalidate(Addr, len);
533 /// getFunctionStub - This returns a pointer to a function stub, creating
534 /// one on demand as needed.
535 void *JITResolver::getFunctionStub(Function *F) {
536 MutexGuard locked(TheJIT->lock);
538 // If we already have a stub for this function, recycle it.
539 void *&Stub = state.getFunctionToStubMap(locked)[F];
540 if (Stub) return Stub;
542 // Call the lazy resolver function unless we already KNOW it is an external
543 // function, in which case we just skip the lazy resolution step.
544 void *Actual = (void*)(intptr_t)LazyResolverFn;
545 if (F->isExternal() && F->hasExternalLinkage())
546 Actual = TheJIT->getPointerToFunction(F);
548 // Otherwise, codegen a new stub. For now, the stub will call the lazy
549 // resolver function.
550 Stub = TheJIT->getJITInfo().emitFunctionStub(Actual, MCE);
552 if (Actual != (void*)(intptr_t)LazyResolverFn) {
553 // If we are getting the stub for an external function, we really want the
554 // address of the stub in the GlobalAddressMap for the JIT, not the address
555 // of the external function.
556 TheJIT->updateGlobalMapping(F, Stub);
559 // Invalidate the icache if necessary.
560 synchronizeICache(Stub, MCE.getCurrentPCValue()-(intptr_t)Stub);
562 DEBUG(std::cerr << "JIT: Stub emitted at [" << Stub << "] for function '"
563 << F->getName() << "'\n");
565 // Finally, keep track of the stub-to-Function mapping so that the
566 // JITCompilerFn knows which function to compile!
567 state.getStubToFunctionMap(locked)[Stub] = F;
571 /// getExternalFunctionStub - Return a stub for the function at the
572 /// specified address, created lazily on demand.
573 void *JITResolver::getExternalFunctionStub(void *FnAddr) {
574 // If we already have a stub for this function, recycle it.
575 void *&Stub = ExternalFnToStubMap[FnAddr];
576 if (Stub) return Stub;
578 Stub = TheJIT->getJITInfo().emitFunctionStub(FnAddr, MCE);
580 // Invalidate the icache if necessary.
581 synchronizeICache(Stub, MCE.getCurrentPCValue()-(intptr_t)Stub);
583 DEBUG(std::cerr << "JIT: Stub emitted at [" << Stub
584 << "] for external function at '" << FnAddr << "'\n");
588 unsigned JITResolver::getGOTIndexForAddr(void* addr) {
589 unsigned idx = revGOTMap[addr];
591 idx = ++nextGOTIndex;
592 revGOTMap[addr] = idx;
593 DEBUG(std::cerr << "Adding GOT entry " << idx
594 << " for addr " << addr << "\n");
595 // ((void**)MemMgr.getGOTBase())[idx] = addr;
600 /// JITCompilerFn - This function is called when a lazy compilation stub has
601 /// been entered. It looks up which function this stub corresponds to, compiles
602 /// it if necessary, then returns the resultant function pointer.
603 void *JITResolver::JITCompilerFn(void *Stub) {
604 JITResolver &JR = getJITResolver();
606 MutexGuard locked(TheJIT->lock);
608 // The address given to us for the stub may not be exactly right, it might be
609 // a little bit after the stub. As such, use upper_bound to find it.
610 std::map<void*, Function*>::iterator I =
611 JR.state.getStubToFunctionMap(locked).upper_bound(Stub);
612 assert(I != JR.state.getStubToFunctionMap(locked).begin() &&
613 "This is not a known stub!");
614 Function *F = (--I)->second;
616 // We might like to remove the stub from the StubToFunction map.
617 // We can't do that! Multiple threads could be stuck, waiting to acquire the
618 // lock above. As soon as the 1st function finishes compiling the function,
619 // the next one will be released, and needs to be able to find the function it
621 //JR.state.getStubToFunctionMap(locked).erase(I);
623 DEBUG(std::cerr << "JIT: Lazily resolving function '" << F->getName()
624 << "' In stub ptr = " << Stub << " actual ptr = "
625 << I->first << "\n");
627 void *Result = TheJIT->getPointerToFunction(F);
629 // We don't need to reuse this stub in the future, as F is now compiled.
630 JR.state.getFunctionToStubMap(locked).erase(F);
632 // FIXME: We could rewrite all references to this stub if we knew them.
634 // What we will do is set the compiled function address to map to the
635 // same GOT entry as the stub so that later clients may update the GOT
636 // if they see it still using the stub address.
637 // Note: this is done so the Resolver doesn't have to manage GOT memory
638 // Do this without allocating map space if the target isn't using a GOT
639 if(JR.revGOTMap.find(Stub) != JR.revGOTMap.end())
640 JR.revGOTMap[Result] = JR.revGOTMap[Stub];
646 //===----------------------------------------------------------------------===//
650 /// JITEmitter - The JIT implementation of the MachineCodeEmitter, which is
651 /// used to output functions to memory for execution.
652 class JITEmitter : public MachineCodeEmitter {
653 JITMemoryManager MemMgr;
655 // When outputting a function stub in the context of some other function, we
656 // save BufferBegin/BufferEnd/CurBufferPtr here.
657 unsigned char *SavedBufferBegin, *SavedBufferEnd, *SavedCurBufferPtr;
659 /// Relocations - These are the relocations that the function needs, as
661 std::vector<MachineRelocation> Relocations;
663 /// MBBLocations - This vector is a mapping from MBB ID's to their address.
664 /// It is filled in by the StartMachineBasicBlock callback and queried by
665 /// the getMachineBasicBlockAddress callback.
666 std::vector<intptr_t> MBBLocations;
668 /// ConstantPool - The constant pool for the current function.
670 MachineConstantPool *ConstantPool;
672 /// ConstantPoolBase - A pointer to the first entry in the constant pool.
674 void *ConstantPoolBase;
676 /// JumpTable - The jump tables for the current function.
678 MachineJumpTableInfo *JumpTable;
680 /// JumpTableBase - A pointer to the first entry in the jump table.
684 JITEmitter(JIT &jit) : MemMgr(jit.getJITInfo().needsGOT()) {
686 DEBUG(if (MemMgr.isManagingGOT()) std::cerr << "JIT is managing a GOT\n");
689 virtual void startFunction(MachineFunction &F);
690 virtual bool finishFunction(MachineFunction &F);
692 void emitConstantPool(MachineConstantPool *MCP);
693 void initJumpTableInfo(MachineJumpTableInfo *MJTI);
694 void emitJumpTableInfo(MachineJumpTableInfo *MJTI);
696 virtual void startFunctionStub(unsigned StubSize);
697 virtual void* finishFunctionStub(const Function *F);
699 virtual void addRelocation(const MachineRelocation &MR) {
700 Relocations.push_back(MR);
703 virtual void StartMachineBasicBlock(MachineBasicBlock *MBB) {
704 if (MBBLocations.size() <= (unsigned)MBB->getNumber())
705 MBBLocations.resize((MBB->getNumber()+1)*2);
706 MBBLocations[MBB->getNumber()] = getCurrentPCValue();
709 virtual intptr_t getConstantPoolEntryAddress(unsigned Entry) const;
710 virtual intptr_t getJumpTableEntryAddress(unsigned Entry) const;
712 virtual intptr_t getMachineBasicBlockAddress(MachineBasicBlock *MBB) const {
713 assert(MBBLocations.size() > (unsigned)MBB->getNumber() &&
714 MBBLocations[MBB->getNumber()] && "MBB not emitted!");
715 return MBBLocations[MBB->getNumber()];
718 /// deallocateMemForFunction - Deallocate all memory for the specified
720 void deallocateMemForFunction(Function *F) {
721 MemMgr.deallocateMemForFunction(F);
724 void *getPointerToGlobal(GlobalValue *GV, void *Reference, bool NoNeedStub);
728 void *JITEmitter::getPointerToGlobal(GlobalValue *V, void *Reference,
729 bool DoesntNeedStub) {
730 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) {
731 /// FIXME: If we straightened things out, this could actually emit the
732 /// global immediately instead of queuing it for codegen later!
733 return TheJIT->getOrEmitGlobalVariable(GV);
736 // If we have already compiled the function, return a pointer to its body.
737 Function *F = cast<Function>(V);
738 void *ResultPtr = TheJIT->getPointerToGlobalIfAvailable(F);
739 if (ResultPtr) return ResultPtr;
741 if (F->hasExternalLinkage() && F->isExternal()) {
742 // If this is an external function pointer, we can force the JIT to
743 // 'compile' it, which really just adds it to the map.
745 return TheJIT->getPointerToFunction(F);
747 return getJITResolver(this).getFunctionStub(F);
750 // Okay, the function has not been compiled yet, if the target callback
751 // mechanism is capable of rewriting the instruction directly, prefer to do
752 // that instead of emitting a stub.
754 return getJITResolver(this).AddCallbackAtLocation(F, Reference);
756 // Otherwise, we have to emit a lazy resolving stub.
757 return getJITResolver(this).getFunctionStub(F);
760 void JITEmitter::startFunction(MachineFunction &F) {
761 uintptr_t ActualSize;
762 BufferBegin = CurBufferPtr = MemMgr.startFunctionBody(ActualSize);
763 BufferEnd = BufferBegin+ActualSize;
765 emitConstantPool(F.getConstantPool());
766 initJumpTableInfo(F.getJumpTableInfo());
768 // About to start emitting the machine code for the function.
769 emitAlignment(std::max(F.getFunction()->getAlignment(), 8U));
770 TheJIT->updateGlobalMapping(F.getFunction(), CurBufferPtr);
772 MBBLocations.clear();
775 bool JITEmitter::finishFunction(MachineFunction &F) {
776 if (CurBufferPtr == BufferEnd) {
777 // FIXME: Allocate more space, then try again.
778 std::cerr << "JIT: Ran out of space for generated machine code!\n";
782 emitJumpTableInfo(F.getJumpTableInfo());
784 // FnStart is the start of the text, not the start of the constant pool and
785 // other per-function data.
786 unsigned char *FnStart =
787 (unsigned char *)TheJIT->getPointerToGlobalIfAvailable(F.getFunction());
788 unsigned char *FnEnd = CurBufferPtr;
790 MemMgr.endFunctionBody(F.getFunction(), BufferBegin, FnEnd);
791 NumBytes += FnEnd-FnStart;
793 if (!Relocations.empty()) {
794 NumRelos += Relocations.size();
796 // Resolve the relocations to concrete pointers.
797 for (unsigned i = 0, e = Relocations.size(); i != e; ++i) {
798 MachineRelocation &MR = Relocations[i];
801 ResultPtr = TheJIT->getPointerToNamedFunction(MR.getString());
803 // If the target REALLY wants a stub for this function, emit it now.
804 if (!MR.doesntNeedFunctionStub())
805 ResultPtr = getJITResolver(this).getExternalFunctionStub(ResultPtr);
806 } else if (MR.isGlobalValue()) {
807 ResultPtr = getPointerToGlobal(MR.getGlobalValue(),
808 BufferBegin+MR.getMachineCodeOffset(),
809 MR.doesntNeedFunctionStub());
810 } else if (MR.isBasicBlock()) {
811 ResultPtr = (void*)getMachineBasicBlockAddress(MR.getBasicBlock());
812 } else if (MR.isConstantPoolIndex()){
813 ResultPtr=(void*)getConstantPoolEntryAddress(MR.getConstantPoolIndex());
815 assert(MR.isJumpTableIndex());
816 ResultPtr=(void*)getJumpTableEntryAddress(MR.getJumpTableIndex());
819 MR.setResultPointer(ResultPtr);
821 // if we are managing the GOT and the relocation wants an index,
823 if (MemMgr.isManagingGOT() && MR.isGOTRelative()) {
824 unsigned idx = getJITResolver(this).getGOTIndexForAddr(ResultPtr);
826 if (((void**)MemMgr.getGOTBase())[idx] != ResultPtr) {
827 DEBUG(std::cerr << "GOT was out of date for " << ResultPtr
828 << " pointing at " << ((void**)MemMgr.getGOTBase())[idx]
830 ((void**)MemMgr.getGOTBase())[idx] = ResultPtr;
835 TheJIT->getJITInfo().relocate(BufferBegin, &Relocations[0],
836 Relocations.size(), MemMgr.getGOTBase());
839 // Update the GOT entry for F to point to the new code.
840 if(MemMgr.isManagingGOT()) {
841 unsigned idx = getJITResolver(this).getGOTIndexForAddr((void*)BufferBegin);
842 if (((void**)MemMgr.getGOTBase())[idx] != (void*)BufferBegin) {
843 DEBUG(std::cerr << "GOT was out of date for " << (void*)BufferBegin
844 << " pointing at " << ((void**)MemMgr.getGOTBase())[idx] << "\n");
845 ((void**)MemMgr.getGOTBase())[idx] = (void*)BufferBegin;
849 // Invalidate the icache if necessary.
850 synchronizeICache(FnStart, FnEnd-FnStart);
852 DEBUG(std::cerr << "JIT: Finished CodeGen of [" << (void*)FnStart
853 << "] Function: " << F.getFunction()->getName()
854 << ": " << (FnEnd-FnStart) << " bytes of text, "
855 << Relocations.size() << " relocations\n");
860 void JITEmitter::emitConstantPool(MachineConstantPool *MCP) {
861 const std::vector<MachineConstantPoolEntry> &Constants = MCP->getConstants();
862 if (Constants.empty()) return;
864 MachineConstantPoolEntry CPE = Constants.back();
865 unsigned Size = CPE.Offset;
866 const Type *Ty = CPE.isMachineConstantPoolEntry()
867 ? CPE.Val.MachineCPVal->getType() : CPE.Val.ConstVal->getType();
868 Size += TheJIT->getTargetData()->getTypeSize(Ty);
870 ConstantPoolBase = allocateSpace(Size, 1 << MCP->getConstantPoolAlignment());
873 if (ConstantPoolBase == 0) return; // Buffer overflow.
875 // Initialize the memory for all of the constant pool entries.
876 for (unsigned i = 0, e = Constants.size(); i != e; ++i) {
877 void *CAddr = (char*)ConstantPoolBase+Constants[i].Offset;
878 if (Constants[i].isMachineConstantPoolEntry()) {
879 // FIXME: add support to lower machine constant pool values into bytes!
880 std::cerr << "Initialize memory with machine specific constant pool entry"
881 << " has not been implemented!\n";
884 TheJIT->InitializeMemory(Constants[i].Val.ConstVal, CAddr);
888 void JITEmitter::initJumpTableInfo(MachineJumpTableInfo *MJTI) {
889 const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables();
890 if (JT.empty()) return;
892 unsigned NumEntries = 0;
893 for (unsigned i = 0, e = JT.size(); i != e; ++i)
894 NumEntries += JT[i].MBBs.size();
896 unsigned EntrySize = MJTI->getEntrySize();
898 // Just allocate space for all the jump tables now. We will fix up the actual
899 // MBB entries in the tables after we emit the code for each block, since then
900 // we will know the final locations of the MBBs in memory.
902 JumpTableBase = allocateSpace(NumEntries * EntrySize, MJTI->getAlignment());
905 void JITEmitter::emitJumpTableInfo(MachineJumpTableInfo *MJTI) {
906 const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables();
907 if (JT.empty() || JumpTableBase == 0) return;
910 assert(MJTI->getEntrySize() == sizeof(void*) && "Cross JIT'ing?");
912 // For each jump table, map each target in the jump table to the address of
913 // an emitted MachineBasicBlock.
914 intptr_t *SlotPtr = (intptr_t*)JumpTableBase;
916 for (unsigned i = 0, e = JT.size(); i != e; ++i) {
917 const std::vector<MachineBasicBlock*> &MBBs = JT[i].MBBs;
918 // Store the address of the basic block for this jump table slot in the
919 // memory we allocated for the jump table in 'initJumpTableInfo'
920 for (unsigned mi = 0, me = MBBs.size(); mi != me; ++mi)
921 *SlotPtr++ = getMachineBasicBlockAddress(MBBs[mi]);
925 void JITEmitter::startFunctionStub(unsigned StubSize) {
926 SavedBufferBegin = BufferBegin;
927 SavedBufferEnd = BufferEnd;
928 SavedCurBufferPtr = CurBufferPtr;
930 BufferBegin = CurBufferPtr = MemMgr.allocateStub(StubSize);
931 BufferEnd = BufferBegin+StubSize+1;
934 void *JITEmitter::finishFunctionStub(const Function *F) {
935 NumBytes += getCurrentPCOffset();
936 std::swap(SavedBufferBegin, BufferBegin);
937 BufferEnd = SavedBufferEnd;
938 CurBufferPtr = SavedCurBufferPtr;
939 return SavedBufferBegin;
942 // getConstantPoolEntryAddress - Return the address of the 'ConstantNum' entry
943 // in the constant pool that was last emitted with the 'emitConstantPool'
946 intptr_t JITEmitter::getConstantPoolEntryAddress(unsigned ConstantNum) const {
947 assert(ConstantNum < ConstantPool->getConstants().size() &&
948 "Invalid ConstantPoolIndex!");
949 return (intptr_t)ConstantPoolBase +
950 ConstantPool->getConstants()[ConstantNum].Offset;
953 // getJumpTableEntryAddress - Return the address of the JumpTable with index
954 // 'Index' in the jumpp table that was last initialized with 'initJumpTableInfo'
956 intptr_t JITEmitter::getJumpTableEntryAddress(unsigned Index) const {
957 const std::vector<MachineJumpTableEntry> &JT = JumpTable->getJumpTables();
958 assert(Index < JT.size() && "Invalid jump table index!");
961 unsigned EntrySize = JumpTable->getEntrySize();
963 for (unsigned i = 0; i < Index; ++i)
964 Offset += JT[i].MBBs.size() * EntrySize;
966 return (intptr_t)((char *)JumpTableBase + Offset);
969 //===----------------------------------------------------------------------===//
970 // Public interface to this file
971 //===----------------------------------------------------------------------===//
973 MachineCodeEmitter *JIT::createEmitter(JIT &jit) {
974 return new JITEmitter(jit);
977 // getPointerToNamedFunction - This function is used as a global wrapper to
978 // JIT::getPointerToNamedFunction for the purpose of resolving symbols when
979 // bugpoint is debugging the JIT. In that scenario, we are loading an .so and
980 // need to resolve function(s) that are being mis-codegenerated, so we need to
981 // resolve their addresses at runtime, and this is the way to do it.
983 void *getPointerToNamedFunction(const char *Name) {
984 if (Function *F = TheJIT->FindFunctionNamed(Name))
985 return TheJIT->getPointerToFunction(F);
986 return TheJIT->getPointerToNamedFunction(Name);
990 // getPointerToFunctionOrStub - If the specified function has been
991 // code-gen'd, return a pointer to the function. If not, compile it, or use
992 // a stub to implement lazy compilation if available.
994 void *JIT::getPointerToFunctionOrStub(Function *F) {
995 // If we have already code generated the function, just return the address.
996 if (void *Addr = getPointerToGlobalIfAvailable(F))
999 // Get a stub if the target supports it
1000 return getJITResolver(MCE).getFunctionStub(F);
1003 /// freeMachineCodeForFunction - release machine code memory for given Function.
1005 void JIT::freeMachineCodeForFunction(Function *F) {
1006 // Delete translation for this from the ExecutionEngine, so it will get
1007 // retranslated next time it is used.
1008 updateGlobalMapping(F, 0);
1010 // Free the actual memory for the function body and related stuff.
1011 assert(dynamic_cast<JITEmitter*>(MCE) && "Unexpected MCE?");
1012 dynamic_cast<JITEmitter*>(MCE)->deallocateMemForFunction(F);