llvm-6502/lib/ExecutionEngine/JIT/JITEmitter.cpp
Reid Spencer 3ed469ccd7 For PR786:
Turn on -Wunused and -Wno-unused-parameter. Clean up most of the resulting
fall out by removing unused variables. Remaining warnings have to do with
unused functions (I didn't want to delete code without review) and unused
variables in generated code. Maintainers should clean up the remaining
issues when they see them. All changes pass DejaGnu tests and Olden.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@31380 91177308-0d34-0410-b5e6-96231b3b80d8
2006-11-02 20:25:50 +00:00

1014 lines
38 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) {
// Allocate a new block close to the last one.
const sys::MemoryBlock *BOld = Blocks.empty() ? 0 : &Blocks.front();
std::string ErrMsg;
sys::MemoryBlock B = sys::Memory::AllocateRWX(size, BOld, &ErrMsg);
if (B.base() == 0) {
std::cerr << "Allocation failed when allocating new memory in the JIT\n";
std::cerr << ErrMsg << "\n";
abort();
}
Blocks.push_back(B);
return B;
}
//===----------------------------------------------------------------------===//
// 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*)(intptr_t)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;
}
#if (defined(__POWERPC__) || defined (__ppc__) || defined(_POWER)) && \
defined(__APPLE__)
extern "C" void sys_icache_invalidate(const void *Addr, size_t len);
#endif
/// synchronizeICache - On some targets, the JIT emitted code must be
/// explicitly refetched to ensure correct execution.
static void synchronizeICache(const void *Addr, size_t len) {
#if (defined(__POWERPC__) || defined (__ppc__) || defined(_POWER)) && \
defined(__APPLE__)
sys_icache_invalidate(Addr, len);
#endif
}
/// 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*)(intptr_t)LazyResolverFn;
if (F->isExternal() && !F->hasNotBeenReadFromBytecode())
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*)(intptr_t)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);
}
// Invalidate the icache if necessary.
synchronizeICache(Stub, MCE.getCurrentPCValue()-(intptr_t)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);
// Invalidate the icache if necessary.
synchronizeICache(Stub, MCE.getCurrentPCValue()-(intptr_t)Stub);
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;
/// JumpTable - The jump tables 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->isExternal() && !F->hasNotBeenReadFromBytecode()) {
// 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());
// FnStart is the start of the text, not the start of the constant pool and
// other per-function data.
unsigned char *FnStart =
(unsigned char *)TheJIT->getPointerToGlobalIfAvailable(F.getFunction());
unsigned char *FnEnd = CurBufferPtr;
MemMgr.endFunctionBody(F.getFunction(), BufferBegin, FnEnd);
NumBytes += FnEnd-FnStart;
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 if (MR.isBasicBlock()) {
ResultPtr = (void*)getMachineBasicBlockAddress(MR.getBasicBlock());
} else if (MR.isConstantPoolIndex()){
ResultPtr=(void*)getConstantPoolEntryAddress(MR.getConstantPoolIndex());
} else {
assert(MR.isJumpTableIndex());
ResultPtr=(void*)getJumpTableEntryAddress(MR.getJumpTableIndex());
}
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;
}
}
// Invalidate the icache if necessary.
synchronizeICache(FnStart, FnEnd-FnStart);
DEBUG(std::cerr << "JIT: Finished CodeGen of [" << (void*)FnStart
<< "] Function: " << F.getFunction()->getName()
<< ": " << (FnEnd-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;
MachineConstantPoolEntry CPE = Constants.back();
unsigned Size = CPE.Offset;
const Type *Ty = CPE.isMachineConstantPoolEntry()
? CPE.Val.MachineCPVal->getType() : CPE.Val.ConstVal->getType();
Size += TheJIT->getTargetData()->getTypeSize(Ty);
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;
if (Constants[i].isMachineConstantPoolEntry()) {
// FIXME: add support to lower machine constant pool values into bytes!
std::cerr << "Initialize memory with machine specific constant pool entry"
<< " has not been implemented!\n";
abort();
}
TheJIT->InitializeMemory(Constants[i].Val.ConstVal, 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;
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) {
if (Function *F = TheJIT->FindFunctionNamed(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);
}