llvm-6502/lib/ExecutionEngine/JIT/JITEmitter.cpp
Chris Lattner f3af4ff005 Make this print the right start pointer
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@28321 91177308-0d34-0410-b5e6-96231b3b80d8
2006-05-16 06:45:50 +00:00

975 lines
36 KiB
C++

//===-- JITEmitter.cpp - Write machine code to executable memory ----------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines a MachineCodeEmitter object that is used by the JIT to
// write machine code to memory and remember where relocatable values are.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "jit"
#include "JIT.h"
#include "llvm/Constant.h"
#include "llvm/Module.h"
#include "llvm/Type.h"
#include "llvm/CodeGen/MachineCodeEmitter.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineJumpTableInfo.h"
#include "llvm/CodeGen/MachineRelocation.h"
#include "llvm/ExecutionEngine/GenericValue.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetJITInfo.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/MutexGuard.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/System/Memory.h"
#include <algorithm>
#include <iostream>
using namespace llvm;
namespace {
Statistic<> NumBytes("jit", "Number of bytes of machine code compiled");
Statistic<> NumRelos("jit", "Number of relocations applied");
JIT *TheJIT = 0;
}
//===----------------------------------------------------------------------===//
// JITMemoryManager code.
//
namespace {
/// MemoryRangeHeader - For a range of memory, this is the header that we put
/// on the block of memory. It is carefully crafted to be one word of memory.
/// Allocated blocks have just this header, free'd blocks have FreeRangeHeader
/// which starts with this.
struct FreeRangeHeader;
struct MemoryRangeHeader {
/// ThisAllocated - This is true if this block is currently allocated. If
/// not, this can be converted to a FreeRangeHeader.
intptr_t ThisAllocated : 1;
/// PrevAllocated - Keep track of whether the block immediately before us is
/// allocated. If not, the word immediately before this header is the size
/// of the previous block.
intptr_t PrevAllocated : 1;
/// BlockSize - This is the size in bytes of this memory block,
/// including this header.
uintptr_t BlockSize : (sizeof(intptr_t)*8 - 2);
/// getBlockAfter - Return the memory block immediately after this one.
///
MemoryRangeHeader &getBlockAfter() const {
return *(MemoryRangeHeader*)((char*)this+BlockSize);
}
/// getFreeBlockBefore - If the block before this one is free, return it,
/// otherwise return null.
FreeRangeHeader *getFreeBlockBefore() const {
if (PrevAllocated) return 0;
intptr_t PrevSize = ((intptr_t *)this)[-1];
return (FreeRangeHeader*)((char*)this-PrevSize);
}
/// FreeBlock - Turn an allocated block into a free block, adjusting
/// bits in the object headers, and adding an end of region memory block.
FreeRangeHeader *FreeBlock(FreeRangeHeader *FreeList);
/// TrimAllocationToSize - If this allocated block is significantly larger
/// than NewSize, split it into two pieces (where the former is NewSize
/// bytes, including the header), and add the new block to the free list.
FreeRangeHeader *TrimAllocationToSize(FreeRangeHeader *FreeList,
uint64_t NewSize);
};
/// FreeRangeHeader - For a memory block that isn't already allocated, this
/// keeps track of the current block and has a pointer to the next free block.
/// Free blocks are kept on a circularly linked list.
struct FreeRangeHeader : public MemoryRangeHeader {
FreeRangeHeader *Prev;
FreeRangeHeader *Next;
/// getMinBlockSize - Get the minimum size for a memory block. Blocks
/// smaller than this size cannot be created.
static unsigned getMinBlockSize() {
return sizeof(FreeRangeHeader)+sizeof(intptr_t);
}
/// SetEndOfBlockSizeMarker - The word at the end of every free block is
/// known to be the size of the free block. Set it for this block.
void SetEndOfBlockSizeMarker() {
void *EndOfBlock = (char*)this + BlockSize;
((intptr_t *)EndOfBlock)[-1] = BlockSize;
}
FreeRangeHeader *RemoveFromFreeList() {
assert(Next->Prev == this && Prev->Next == this && "Freelist broken!");
Next->Prev = Prev;
return Prev->Next = Next;
}
void AddToFreeList(FreeRangeHeader *FreeList) {
Next = FreeList;
Prev = FreeList->Prev;
Prev->Next = this;
Next->Prev = this;
}
/// GrowBlock - The block after this block just got deallocated. Merge it
/// into the current block.
void GrowBlock(uintptr_t NewSize);
/// AllocateBlock - Mark this entire block allocated, updating freelists
/// etc. This returns a pointer to the circular free-list.
FreeRangeHeader *AllocateBlock();
};
}
/// AllocateBlock - Mark this entire block allocated, updating freelists
/// etc. This returns a pointer to the circular free-list.
FreeRangeHeader *FreeRangeHeader::AllocateBlock() {
assert(!ThisAllocated && !getBlockAfter().PrevAllocated &&
"Cannot allocate an allocated block!");
// Mark this block allocated.
ThisAllocated = 1;
getBlockAfter().PrevAllocated = 1;
// Remove it from the free list.
return RemoveFromFreeList();
}
/// FreeBlock - Turn an allocated block into a free block, adjusting
/// bits in the object headers, and adding an end of region memory block.
/// If possible, coallesce this block with neighboring blocks. Return the
/// FreeRangeHeader to allocate from.
FreeRangeHeader *MemoryRangeHeader::FreeBlock(FreeRangeHeader *FreeList) {
MemoryRangeHeader *FollowingBlock = &getBlockAfter();
assert(ThisAllocated && "This block is already allocated!");
assert(FollowingBlock->PrevAllocated && "Flags out of sync!");
FreeRangeHeader *FreeListToReturn = FreeList;
// If the block after this one is free, merge it into this block.
if (!FollowingBlock->ThisAllocated) {
FreeRangeHeader &FollowingFreeBlock = *(FreeRangeHeader *)FollowingBlock;
// "FreeList" always needs to be a valid free block. If we're about to
// coallesce with it, update our notion of what the free list is.
if (&FollowingFreeBlock == FreeList) {
FreeList = FollowingFreeBlock.Next;
FreeListToReturn = 0;
assert(&FollowingFreeBlock != FreeList && "No tombstone block?");
}
FollowingFreeBlock.RemoveFromFreeList();
// Include the following block into this one.
BlockSize += FollowingFreeBlock.BlockSize;
FollowingBlock = &FollowingFreeBlock.getBlockAfter();
// Tell the block after the block we are coallescing that this block is
// allocated.
FollowingBlock->PrevAllocated = 1;
}
assert(FollowingBlock->ThisAllocated && "Missed coallescing?");
if (FreeRangeHeader *PrevFreeBlock = getFreeBlockBefore()) {
PrevFreeBlock->GrowBlock(PrevFreeBlock->BlockSize + BlockSize);
return FreeListToReturn ? FreeListToReturn : PrevFreeBlock;
}
// Otherwise, mark this block free.
FreeRangeHeader &FreeBlock = *(FreeRangeHeader*)this;
FollowingBlock->PrevAllocated = 0;
FreeBlock.ThisAllocated = 0;
// Link this into the linked list of free blocks.
FreeBlock.AddToFreeList(FreeList);
// Add a marker at the end of the block, indicating the size of this free
// block.
FreeBlock.SetEndOfBlockSizeMarker();
return FreeListToReturn ? FreeListToReturn : &FreeBlock;
}
/// GrowBlock - The block after this block just got deallocated. Merge it
/// into the current block.
void FreeRangeHeader::GrowBlock(uintptr_t NewSize) {
assert(NewSize > BlockSize && "Not growing block?");
BlockSize = NewSize;
SetEndOfBlockSizeMarker();
getBlockAfter().PrevAllocated = 0;
}
/// TrimAllocationToSize - If this allocated block is significantly larger
/// than NewSize, split it into two pieces (where the former is NewSize
/// bytes, including the header), and add the new block to the free list.
FreeRangeHeader *MemoryRangeHeader::
TrimAllocationToSize(FreeRangeHeader *FreeList, uint64_t NewSize) {
assert(ThisAllocated && getBlockAfter().PrevAllocated &&
"Cannot deallocate part of an allocated block!");
// Round up size for alignment of header.
unsigned HeaderAlign = __alignof(FreeRangeHeader);
NewSize = (NewSize+ (HeaderAlign-1)) & ~(HeaderAlign-1);
// Size is now the size of the block we will remove from the start of the
// current block.
assert(NewSize <= BlockSize &&
"Allocating more space from this block than exists!");
// If splitting this block will cause the remainder to be too small, do not
// split the block.
if (BlockSize <= NewSize+FreeRangeHeader::getMinBlockSize())
return FreeList;
// Otherwise, we splice the required number of bytes out of this block, form
// a new block immediately after it, then mark this block allocated.
MemoryRangeHeader &FormerNextBlock = getBlockAfter();
// Change the size of this block.
BlockSize = NewSize;
// Get the new block we just sliced out and turn it into a free block.
FreeRangeHeader &NewNextBlock = (FreeRangeHeader &)getBlockAfter();
NewNextBlock.BlockSize = (char*)&FormerNextBlock - (char*)&NewNextBlock;
NewNextBlock.ThisAllocated = 0;
NewNextBlock.PrevAllocated = 1;
NewNextBlock.SetEndOfBlockSizeMarker();
FormerNextBlock.PrevAllocated = 0;
NewNextBlock.AddToFreeList(FreeList);
return &NewNextBlock;
}
namespace {
/// JITMemoryManager - Manage memory for the JIT code generation in a logical,
/// sane way. This splits a large block of MAP_NORESERVE'd memory into two
/// sections, one for function stubs, one for the functions themselves. We
/// have to do this because we may need to emit a function stub while in the
/// middle of emitting a function, and we don't know how large the function we
/// are emitting is. This never bothers to release the memory, because when
/// we are ready to destroy the JIT, the program exits.
class JITMemoryManager {
std::vector<sys::MemoryBlock> Blocks; // Memory blocks allocated by the JIT
FreeRangeHeader *FreeMemoryList; // Circular list of free blocks.
// When emitting code into a memory block, this is the block.
MemoryRangeHeader *CurBlock;
unsigned char *CurStubPtr, *StubBase;
unsigned char *GOTBase; // Target Specific reserved memory
// Centralize memory block allocation.
sys::MemoryBlock getNewMemoryBlock(unsigned size);
std::map<const Function*, MemoryRangeHeader*> FunctionBlocks;
public:
JITMemoryManager(bool useGOT);
~JITMemoryManager();
inline unsigned char *allocateStub(unsigned StubSize);
/// startFunctionBody - When a function starts, allocate a block of free
/// executable memory, returning a pointer to it and its actual size.
unsigned char *startFunctionBody(uintptr_t &ActualSize) {
CurBlock = FreeMemoryList;
// Allocate the entire memory block.
FreeMemoryList = FreeMemoryList->AllocateBlock();
ActualSize = CurBlock->BlockSize-sizeof(MemoryRangeHeader);
return (unsigned char *)(CurBlock+1);
}
/// endFunctionBody - The function F is now allocated, and takes the memory
/// in the range [FunctionStart,FunctionEnd).
void endFunctionBody(const Function *F, unsigned char *FunctionStart,
unsigned char *FunctionEnd) {
assert(FunctionEnd > FunctionStart);
assert(FunctionStart == (unsigned char *)(CurBlock+1) &&
"Mismatched function start/end!");
uintptr_t BlockSize = FunctionEnd - (unsigned char *)CurBlock;
FunctionBlocks[F] = CurBlock;
// Release the memory at the end of this block that isn't needed.
FreeMemoryList =CurBlock->TrimAllocationToSize(FreeMemoryList, BlockSize);
}
unsigned char *getGOTBase() const {
return GOTBase;
}
bool isManagingGOT() const {
return GOTBase != NULL;
}
/// deallocateMemForFunction - Deallocate all memory for the specified
/// function body.
void deallocateMemForFunction(const Function *F) {
std::map<const Function*, MemoryRangeHeader*>::iterator
I = FunctionBlocks.find(F);
if (I == FunctionBlocks.end()) return;
// Find the block that is allocated for this function.
MemoryRangeHeader *MemRange = I->second;
assert(MemRange->ThisAllocated && "Block isn't allocated!");
// Fill the buffer with garbage!
DEBUG(memset(MemRange+1, 0xCD, MemRange->BlockSize-sizeof(*MemRange)));
// Free the memory.
FreeMemoryList = MemRange->FreeBlock(FreeMemoryList);
// Finally, remove this entry from FunctionBlocks.
FunctionBlocks.erase(I);
}
};
}
JITMemoryManager::JITMemoryManager(bool useGOT) {
// Allocate a 16M block of memory for functions.
sys::MemoryBlock MemBlock = getNewMemoryBlock(16 << 20);
unsigned char *MemBase = reinterpret_cast<unsigned char*>(MemBlock.base());
// Allocate stubs backwards from the base, allocate functions forward
// from the base.
StubBase = MemBase;
CurStubPtr = MemBase + 512*1024; // Use 512k for stubs, working backwards.
// We set up the memory chunk with 4 mem regions, like this:
// [ START
// [ Free #0 ] -> Large space to allocate functions from.
// [ Allocated #1 ] -> Tiny space to separate regions.
// [ Free #2 ] -> Tiny space so there is always at least 1 free block.
// [ Allocated #3 ] -> Tiny space to prevent looking past end of block.
// END ]
//
// The last three blocks are never deallocated or touched.
// Add MemoryRangeHeader to the end of the memory region, indicating that
// the space after the block of memory is allocated. This is block #3.
MemoryRangeHeader *Mem3 = (MemoryRangeHeader*)(MemBase+MemBlock.size())-1;
Mem3->ThisAllocated = 1;
Mem3->PrevAllocated = 0;
Mem3->BlockSize = 0;
/// Add a tiny free region so that the free list always has one entry.
FreeRangeHeader *Mem2 =
(FreeRangeHeader *)(((char*)Mem3)-FreeRangeHeader::getMinBlockSize());
Mem2->ThisAllocated = 0;
Mem2->PrevAllocated = 1;
Mem2->BlockSize = FreeRangeHeader::getMinBlockSize();
Mem2->SetEndOfBlockSizeMarker();
Mem2->Prev = Mem2; // Mem2 *is* the free list for now.
Mem2->Next = Mem2;
/// Add a tiny allocated region so that Mem2 is never coallesced away.
MemoryRangeHeader *Mem1 = (MemoryRangeHeader*)Mem2-1;
Mem1->ThisAllocated = 1;
Mem1->PrevAllocated = 0;
Mem1->BlockSize = (char*)Mem2 - (char*)Mem1;
// Add a FreeRangeHeader to the start of the function body region, indicating
// that the space is free. Mark the previous block allocated so we never look
// at it.
FreeRangeHeader *Mem0 = (FreeRangeHeader*)CurStubPtr;
Mem0->ThisAllocated = 0;
Mem0->PrevAllocated = 1;
Mem0->BlockSize = (char*)Mem1-(char*)Mem0;
Mem0->SetEndOfBlockSizeMarker();
Mem0->AddToFreeList(Mem2);
// Start out with the freelist pointing to Mem0.
FreeMemoryList = Mem0;
// Allocate the GOT.
GOTBase = NULL;
if (useGOT) GOTBase = new unsigned char[sizeof(void*) * 8192];
}
JITMemoryManager::~JITMemoryManager() {
for (unsigned i = 0, e = Blocks.size(); i != e; ++i)
sys::Memory::ReleaseRWX(Blocks[i]);
delete[] GOTBase;
Blocks.clear();
}
unsigned char *JITMemoryManager::allocateStub(unsigned StubSize) {
CurStubPtr -= StubSize;
if (CurStubPtr < StubBase) {
// FIXME: allocate a new block
std::cerr << "JIT ran out of memory for function stubs!\n";
abort();
}
return CurStubPtr;
}
sys::MemoryBlock JITMemoryManager::getNewMemoryBlock(unsigned size) {
try {
// Allocate a new block close to the last one.
const sys::MemoryBlock *BOld = Blocks.empty() ? 0 : &Blocks.front();
sys::MemoryBlock B = sys::Memory::AllocateRWX(size, BOld);
Blocks.push_back(B);
return B;
} catch (std::string &err) {
std::cerr << "Allocation failed when allocating new memory in the JIT\n";
std::cerr << err << "\n";
abort();
}
}
//===----------------------------------------------------------------------===//
// JIT lazy compilation code.
//
namespace {
class JITResolverState {
private:
/// FunctionToStubMap - Keep track of the stub created for a particular
/// function so that we can reuse them if necessary.
std::map<Function*, void*> FunctionToStubMap;
/// StubToFunctionMap - Keep track of the function that each stub
/// corresponds to.
std::map<void*, Function*> StubToFunctionMap;
public:
std::map<Function*, void*>& getFunctionToStubMap(const MutexGuard& locked) {
assert(locked.holds(TheJIT->lock));
return FunctionToStubMap;
}
std::map<void*, Function*>& getStubToFunctionMap(const MutexGuard& locked) {
assert(locked.holds(TheJIT->lock));
return StubToFunctionMap;
}
};
/// JITResolver - Keep track of, and resolve, call sites for functions that
/// have not yet been compiled.
class JITResolver {
/// MCE - The MachineCodeEmitter to use to emit stubs with.
MachineCodeEmitter &MCE;
/// LazyResolverFn - The target lazy resolver function that we actually
/// rewrite instructions to use.
TargetJITInfo::LazyResolverFn LazyResolverFn;
JITResolverState state;
/// ExternalFnToStubMap - This is the equivalent of FunctionToStubMap for
/// external functions.
std::map<void*, void*> ExternalFnToStubMap;
//map addresses to indexes in the GOT
std::map<void*, unsigned> revGOTMap;
unsigned nextGOTIndex;
public:
JITResolver(MachineCodeEmitter &mce) : MCE(mce), nextGOTIndex(0) {
LazyResolverFn =
TheJIT->getJITInfo().getLazyResolverFunction(JITCompilerFn);
}
/// getFunctionStub - This returns a pointer to a function stub, creating
/// one on demand as needed.
void *getFunctionStub(Function *F);
/// getExternalFunctionStub - Return a stub for the function at the
/// specified address, created lazily on demand.
void *getExternalFunctionStub(void *FnAddr);
/// AddCallbackAtLocation - If the target is capable of rewriting an
/// instruction without the use of a stub, record the location of the use so
/// we know which function is being used at the location.
void *AddCallbackAtLocation(Function *F, void *Location) {
MutexGuard locked(TheJIT->lock);
/// Get the target-specific JIT resolver function.
state.getStubToFunctionMap(locked)[Location] = F;
return (void*)LazyResolverFn;
}
/// getGOTIndexForAddress - Return a new or existing index in the GOT for
/// and address. This function only manages slots, it does not manage the
/// contents of the slots or the memory associated with the GOT.
unsigned getGOTIndexForAddr(void* addr);
/// JITCompilerFn - This function is called to resolve a stub to a compiled
/// address. If the LLVM Function corresponding to the stub has not yet
/// been compiled, this function compiles it first.
static void *JITCompilerFn(void *Stub);
};
}
/// getJITResolver - This function returns the one instance of the JIT resolver.
///
static JITResolver &getJITResolver(MachineCodeEmitter *MCE = 0) {
static JITResolver TheJITResolver(*MCE);
return TheJITResolver;
}
/// getFunctionStub - This returns a pointer to a function stub, creating
/// one on demand as needed.
void *JITResolver::getFunctionStub(Function *F) {
MutexGuard locked(TheJIT->lock);
// If we already have a stub for this function, recycle it.
void *&Stub = state.getFunctionToStubMap(locked)[F];
if (Stub) return Stub;
// Call the lazy resolver function unless we already KNOW it is an external
// function, in which case we just skip the lazy resolution step.
void *Actual = (void*)LazyResolverFn;
if (F->isExternal() && F->hasExternalLinkage())
Actual = TheJIT->getPointerToFunction(F);
// Otherwise, codegen a new stub. For now, the stub will call the lazy
// resolver function.
Stub = TheJIT->getJITInfo().emitFunctionStub(Actual, MCE);
if (Actual != (void*)LazyResolverFn) {
// If we are getting the stub for an external function, we really want the
// address of the stub in the GlobalAddressMap for the JIT, not the address
// of the external function.
TheJIT->updateGlobalMapping(F, Stub);
}
DEBUG(std::cerr << "JIT: Stub emitted at [" << Stub << "] for function '"
<< F->getName() << "'\n");
// Finally, keep track of the stub-to-Function mapping so that the
// JITCompilerFn knows which function to compile!
state.getStubToFunctionMap(locked)[Stub] = F;
return Stub;
}
/// getExternalFunctionStub - Return a stub for the function at the
/// specified address, created lazily on demand.
void *JITResolver::getExternalFunctionStub(void *FnAddr) {
// If we already have a stub for this function, recycle it.
void *&Stub = ExternalFnToStubMap[FnAddr];
if (Stub) return Stub;
Stub = TheJIT->getJITInfo().emitFunctionStub(FnAddr, MCE);
DEBUG(std::cerr << "JIT: Stub emitted at [" << Stub
<< "] for external function at '" << FnAddr << "'\n");
return Stub;
}
unsigned JITResolver::getGOTIndexForAddr(void* addr) {
unsigned idx = revGOTMap[addr];
if (!idx) {
idx = ++nextGOTIndex;
revGOTMap[addr] = idx;
DEBUG(std::cerr << "Adding GOT entry " << idx
<< " for addr " << addr << "\n");
// ((void**)MemMgr.getGOTBase())[idx] = addr;
}
return idx;
}
/// JITCompilerFn - This function is called when a lazy compilation stub has
/// been entered. It looks up which function this stub corresponds to, compiles
/// it if necessary, then returns the resultant function pointer.
void *JITResolver::JITCompilerFn(void *Stub) {
JITResolver &JR = getJITResolver();
MutexGuard locked(TheJIT->lock);
// The address given to us for the stub may not be exactly right, it might be
// a little bit after the stub. As such, use upper_bound to find it.
std::map<void*, Function*>::iterator I =
JR.state.getStubToFunctionMap(locked).upper_bound(Stub);
assert(I != JR.state.getStubToFunctionMap(locked).begin() &&
"This is not a known stub!");
Function *F = (--I)->second;
// We might like to remove the stub from the StubToFunction map.
// We can't do that! Multiple threads could be stuck, waiting to acquire the
// lock above. As soon as the 1st function finishes compiling the function,
// the next one will be released, and needs to be able to find the function it
// needs to call.
//JR.state.getStubToFunctionMap(locked).erase(I);
DEBUG(std::cerr << "JIT: Lazily resolving function '" << F->getName()
<< "' In stub ptr = " << Stub << " actual ptr = "
<< I->first << "\n");
void *Result = TheJIT->getPointerToFunction(F);
// We don't need to reuse this stub in the future, as F is now compiled.
JR.state.getFunctionToStubMap(locked).erase(F);
// FIXME: We could rewrite all references to this stub if we knew them.
// What we will do is set the compiled function address to map to the
// same GOT entry as the stub so that later clients may update the GOT
// if they see it still using the stub address.
// Note: this is done so the Resolver doesn't have to manage GOT memory
// Do this without allocating map space if the target isn't using a GOT
if(JR.revGOTMap.find(Stub) != JR.revGOTMap.end())
JR.revGOTMap[Result] = JR.revGOTMap[Stub];
return Result;
}
//===----------------------------------------------------------------------===//
// JITEmitter code.
//
namespace {
/// JITEmitter - The JIT implementation of the MachineCodeEmitter, which is
/// used to output functions to memory for execution.
class JITEmitter : public MachineCodeEmitter {
JITMemoryManager MemMgr;
// When outputting a function stub in the context of some other function, we
// save BufferBegin/BufferEnd/CurBufferPtr here.
unsigned char *SavedBufferBegin, *SavedBufferEnd, *SavedCurBufferPtr;
/// Relocations - These are the relocations that the function needs, as
/// emitted.
std::vector<MachineRelocation> Relocations;
/// MBBLocations - This vector is a mapping from MBB ID's to their address.
/// It is filled in by the StartMachineBasicBlock callback and queried by
/// the getMachineBasicBlockAddress callback.
std::vector<intptr_t> MBBLocations;
/// ConstantPool - The constant pool for the current function.
///
MachineConstantPool *ConstantPool;
/// ConstantPoolBase - A pointer to the first entry in the constant pool.
///
void *ConstantPoolBase;
/// ConstantPool - The constant pool for the current function.
///
MachineJumpTableInfo *JumpTable;
/// JumpTableBase - A pointer to the first entry in the jump table.
///
void *JumpTableBase;
public:
JITEmitter(JIT &jit) : MemMgr(jit.getJITInfo().needsGOT()) {
TheJIT = &jit;
DEBUG(if (MemMgr.isManagingGOT()) std::cerr << "JIT is managing a GOT\n");
}
virtual void startFunction(MachineFunction &F);
virtual bool finishFunction(MachineFunction &F);
void emitConstantPool(MachineConstantPool *MCP);
void initJumpTableInfo(MachineJumpTableInfo *MJTI);
void emitJumpTableInfo(MachineJumpTableInfo *MJTI);
virtual void startFunctionStub(unsigned StubSize);
virtual void* finishFunctionStub(const Function *F);
virtual void addRelocation(const MachineRelocation &MR) {
Relocations.push_back(MR);
}
virtual void StartMachineBasicBlock(MachineBasicBlock *MBB) {
if (MBBLocations.size() <= (unsigned)MBB->getNumber())
MBBLocations.resize((MBB->getNumber()+1)*2);
MBBLocations[MBB->getNumber()] = getCurrentPCValue();
}
virtual intptr_t getConstantPoolEntryAddress(unsigned Entry) const;
virtual intptr_t getJumpTableEntryAddress(unsigned Entry) const;
virtual intptr_t getMachineBasicBlockAddress(MachineBasicBlock *MBB) const {
assert(MBBLocations.size() > (unsigned)MBB->getNumber() &&
MBBLocations[MBB->getNumber()] && "MBB not emitted!");
return MBBLocations[MBB->getNumber()];
}
/// deallocateMemForFunction - Deallocate all memory for the specified
/// function body.
void deallocateMemForFunction(Function *F) {
MemMgr.deallocateMemForFunction(F);
}
private:
void *getPointerToGlobal(GlobalValue *GV, void *Reference, bool NoNeedStub);
};
}
void *JITEmitter::getPointerToGlobal(GlobalValue *V, void *Reference,
bool DoesntNeedStub) {
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) {
/// FIXME: If we straightened things out, this could actually emit the
/// global immediately instead of queuing it for codegen later!
return TheJIT->getOrEmitGlobalVariable(GV);
}
// If we have already compiled the function, return a pointer to its body.
Function *F = cast<Function>(V);
void *ResultPtr = TheJIT->getPointerToGlobalIfAvailable(F);
if (ResultPtr) return ResultPtr;
if (F->hasExternalLinkage() && F->isExternal()) {
// If this is an external function pointer, we can force the JIT to
// 'compile' it, which really just adds it to the map.
if (DoesntNeedStub)
return TheJIT->getPointerToFunction(F);
return getJITResolver(this).getFunctionStub(F);
}
// Okay, the function has not been compiled yet, if the target callback
// mechanism is capable of rewriting the instruction directly, prefer to do
// that instead of emitting a stub.
if (DoesntNeedStub)
return getJITResolver(this).AddCallbackAtLocation(F, Reference);
// Otherwise, we have to emit a lazy resolving stub.
return getJITResolver(this).getFunctionStub(F);
}
void JITEmitter::startFunction(MachineFunction &F) {
uintptr_t ActualSize;
BufferBegin = CurBufferPtr = MemMgr.startFunctionBody(ActualSize);
BufferEnd = BufferBegin+ActualSize;
emitConstantPool(F.getConstantPool());
initJumpTableInfo(F.getJumpTableInfo());
// About to start emitting the machine code for the function.
emitAlignment(std::max(F.getFunction()->getAlignment(), 8U));
TheJIT->updateGlobalMapping(F.getFunction(), CurBufferPtr);
MBBLocations.clear();
}
bool JITEmitter::finishFunction(MachineFunction &F) {
if (CurBufferPtr == BufferEnd) {
// FIXME: Allocate more space, then try again.
std::cerr << "JIT: Ran out of space for generated machine code!\n";
abort();
}
emitJumpTableInfo(F.getJumpTableInfo());
MemMgr.endFunctionBody(F.getFunction(), BufferBegin, CurBufferPtr);
NumBytes += getCurrentPCOffset();
if (!Relocations.empty()) {
NumRelos += Relocations.size();
// Resolve the relocations to concrete pointers.
for (unsigned i = 0, e = Relocations.size(); i != e; ++i) {
MachineRelocation &MR = Relocations[i];
void *ResultPtr;
if (MR.isString()) {
ResultPtr = TheJIT->getPointerToNamedFunction(MR.getString());
// If the target REALLY wants a stub for this function, emit it now.
if (!MR.doesntNeedFunctionStub())
ResultPtr = getJITResolver(this).getExternalFunctionStub(ResultPtr);
} else if (MR.isGlobalValue()) {
ResultPtr = getPointerToGlobal(MR.getGlobalValue(),
BufferBegin+MR.getMachineCodeOffset(),
MR.doesntNeedFunctionStub());
} else {
assert(MR.isConstantPoolIndex());
ResultPtr=(void*)getConstantPoolEntryAddress(MR.getConstantPoolIndex());
}
MR.setResultPointer(ResultPtr);
// if we are managing the GOT and the relocation wants an index,
// give it one
if (MemMgr.isManagingGOT() && MR.isGOTRelative()) {
unsigned idx = getJITResolver(this).getGOTIndexForAddr(ResultPtr);
MR.setGOTIndex(idx);
if (((void**)MemMgr.getGOTBase())[idx] != ResultPtr) {
DEBUG(std::cerr << "GOT was out of date for " << ResultPtr
<< " pointing at " << ((void**)MemMgr.getGOTBase())[idx]
<< "\n");
((void**)MemMgr.getGOTBase())[idx] = ResultPtr;
}
}
}
TheJIT->getJITInfo().relocate(BufferBegin, &Relocations[0],
Relocations.size(), MemMgr.getGOTBase());
}
// Update the GOT entry for F to point to the new code.
if(MemMgr.isManagingGOT()) {
unsigned idx = getJITResolver(this).getGOTIndexForAddr((void*)BufferBegin);
if (((void**)MemMgr.getGOTBase())[idx] != (void*)BufferBegin) {
DEBUG(std::cerr << "GOT was out of date for " << (void*)BufferBegin
<< " pointing at " << ((void**)MemMgr.getGOTBase())[idx] << "\n");
((void**)MemMgr.getGOTBase())[idx] = (void*)BufferBegin;
}
}
DEBUG(void *FnStart = TheJIT->getPointerToGlobalIfAvailable(F.getFunction());
char *FnEnd = (char*)getCurrentPCOffset();
std::cerr << "JIT: Finished CodeGen of [" << FnStart
<< "] Function: " << F.getFunction()->getName()
<< ": " << (FnEnd-(char*)FnStart) << " bytes of text, "
<< Relocations.size() << " relocations\n");
Relocations.clear();
return false;
}
void JITEmitter::emitConstantPool(MachineConstantPool *MCP) {
const std::vector<MachineConstantPoolEntry> &Constants = MCP->getConstants();
if (Constants.empty()) return;
unsigned Size = Constants.back().Offset;
Size += TheJIT->getTargetData()->getTypeSize(Constants.back().Val->getType());
ConstantPoolBase = allocateSpace(Size, 1 << MCP->getConstantPoolAlignment());
ConstantPool = MCP;
if (ConstantPoolBase == 0) return; // Buffer overflow.
// Initialize the memory for all of the constant pool entries.
for (unsigned i = 0, e = Constants.size(); i != e; ++i) {
void *CAddr = (char*)ConstantPoolBase+Constants[i].Offset;
TheJIT->InitializeMemory(Constants[i].Val, CAddr);
}
}
void JITEmitter::initJumpTableInfo(MachineJumpTableInfo *MJTI) {
const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables();
if (JT.empty()) return;
unsigned NumEntries = 0;
for (unsigned i = 0, e = JT.size(); i != e; ++i)
NumEntries += JT[i].MBBs.size();
unsigned EntrySize = MJTI->getEntrySize();
// Just allocate space for all the jump tables now. We will fix up the actual
// MBB entries in the tables after we emit the code for each block, since then
// we will know the final locations of the MBBs in memory.
JumpTable = MJTI;
JumpTableBase = allocateSpace(NumEntries * EntrySize, MJTI->getAlignment());
}
void JITEmitter::emitJumpTableInfo(MachineJumpTableInfo *MJTI) {
const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables();
if (JT.empty() || JumpTableBase == 0) return;
unsigned Offset = 0;
assert(MJTI->getEntrySize() == sizeof(void*) && "Cross JIT'ing?");
// For each jump table, map each target in the jump table to the address of
// an emitted MachineBasicBlock.
intptr_t *SlotPtr = (intptr_t*)JumpTableBase;
for (unsigned i = 0, e = JT.size(); i != e; ++i) {
const std::vector<MachineBasicBlock*> &MBBs = JT[i].MBBs;
// Store the address of the basic block for this jump table slot in the
// memory we allocated for the jump table in 'initJumpTableInfo'
for (unsigned mi = 0, me = MBBs.size(); mi != me; ++mi)
*SlotPtr++ = getMachineBasicBlockAddress(MBBs[mi]);
}
}
void JITEmitter::startFunctionStub(unsigned StubSize) {
SavedBufferBegin = BufferBegin;
SavedBufferEnd = BufferEnd;
SavedCurBufferPtr = CurBufferPtr;
BufferBegin = CurBufferPtr = MemMgr.allocateStub(StubSize);
BufferEnd = BufferBegin+StubSize+1;
}
void *JITEmitter::finishFunctionStub(const Function *F) {
NumBytes += getCurrentPCOffset();
std::swap(SavedBufferBegin, BufferBegin);
BufferEnd = SavedBufferEnd;
CurBufferPtr = SavedCurBufferPtr;
return SavedBufferBegin;
}
// getConstantPoolEntryAddress - Return the address of the 'ConstantNum' entry
// in the constant pool that was last emitted with the 'emitConstantPool'
// method.
//
intptr_t JITEmitter::getConstantPoolEntryAddress(unsigned ConstantNum) const {
assert(ConstantNum < ConstantPool->getConstants().size() &&
"Invalid ConstantPoolIndex!");
return (intptr_t)ConstantPoolBase +
ConstantPool->getConstants()[ConstantNum].Offset;
}
// getJumpTableEntryAddress - Return the address of the JumpTable with index
// 'Index' in the jumpp table that was last initialized with 'initJumpTableInfo'
//
intptr_t JITEmitter::getJumpTableEntryAddress(unsigned Index) const {
const std::vector<MachineJumpTableEntry> &JT = JumpTable->getJumpTables();
assert(Index < JT.size() && "Invalid jump table index!");
unsigned Offset = 0;
unsigned EntrySize = JumpTable->getEntrySize();
for (unsigned i = 0; i < Index; ++i)
Offset += JT[i].MBBs.size() * EntrySize;
return (intptr_t)((char *)JumpTableBase + Offset);
}
//===----------------------------------------------------------------------===//
// Public interface to this file
//===----------------------------------------------------------------------===//
MachineCodeEmitter *JIT::createEmitter(JIT &jit) {
return new JITEmitter(jit);
}
// getPointerToNamedFunction - This function is used as a global wrapper to
// JIT::getPointerToNamedFunction for the purpose of resolving symbols when
// bugpoint is debugging the JIT. In that scenario, we are loading an .so and
// need to resolve function(s) that are being mis-codegenerated, so we need to
// resolve their addresses at runtime, and this is the way to do it.
extern "C" {
void *getPointerToNamedFunction(const char *Name) {
Module &M = TheJIT->getModule();
if (Function *F = M.getNamedFunction(Name))
return TheJIT->getPointerToFunction(F);
return TheJIT->getPointerToNamedFunction(Name);
}
}
// getPointerToFunctionOrStub - If the specified function has been
// code-gen'd, return a pointer to the function. If not, compile it, or use
// a stub to implement lazy compilation if available.
//
void *JIT::getPointerToFunctionOrStub(Function *F) {
// If we have already code generated the function, just return the address.
if (void *Addr = getPointerToGlobalIfAvailable(F))
return Addr;
// Get a stub if the target supports it
return getJITResolver(MCE).getFunctionStub(F);
}
/// freeMachineCodeForFunction - release machine code memory for given Function.
///
void JIT::freeMachineCodeForFunction(Function *F) {
// Delete translation for this from the ExecutionEngine, so it will get
// retranslated next time it is used.
updateGlobalMapping(F, 0);
// Free the actual memory for the function body and related stuff.
assert(dynamic_cast<JITEmitter*>(MCE) && "Unexpected MCE?");
dynamic_cast<JITEmitter*>(MCE)->deallocateMemForFunction(F);
}