[llvm-commits] CVS: llvm/lib/ExecutionEngine/JIT/JITEmitter.cpp
Chris Lattner
lattner at cs.uiuc.edu
Thu May 11 16:08:20 PDT 2006
Changes in directory llvm/lib/ExecutionEngine/JIT:
JITEmitter.cpp updated: 1.97 -> 1.98
---
Log message:
Significantly revamp allocation of machine code to use free lists, real
allocation policies and much more. All this complexity, and we have no
functionality change, woo! :)
---
Diffs of the changes: (+340 -51)
JITEmitter.cpp | 391 +++++++++++++++++++++++++++++++++++++++++++++++++--------
1 files changed, 340 insertions(+), 51 deletions(-)
Index: llvm/lib/ExecutionEngine/JIT/JITEmitter.cpp
diff -u llvm/lib/ExecutionEngine/JIT/JITEmitter.cpp:1.97 llvm/lib/ExecutionEngine/JIT/JITEmitter.cpp:1.98
--- llvm/lib/ExecutionEngine/JIT/JITEmitter.cpp:1.97 Mon May 8 17:00:52 2006
+++ llvm/lib/ExecutionEngine/JIT/JITEmitter.cpp Thu May 11 18:08:08 2006
@@ -44,6 +44,203 @@
// 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);
+ }
+
+ /// MakeFreeBlock - Turn an allocated block into a free block, adjusting
+ /// bits in the object headers, and adding an end of region memory block.
+ FreeRangeHeader &MakeFreeBlock(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();
+}
+
+/// MakeFreeBlock - 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 this block ends up in, which may be != this if it got
+/// coallesced.
+FreeRangeHeader &MemoryRangeHeader::MakeFreeBlock(FreeRangeHeader *FreeList) {
+ MemoryRangeHeader *FollowingBlock = &getBlockAfter();
+ assert(ThisAllocated && "This block is already allocated!");
+ assert(FollowingBlock->PrevAllocated && "Flags out of sync!");
+
+ // If the block after this one is free, merge it into this block.
+ if (!FollowingBlock->ThisAllocated) {
+ FreeRangeHeader &FollowingFreeBlock = *(FreeRangeHeader *)FollowingBlock;
+ 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 *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 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();
+}
+
+/// 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
@@ -53,19 +250,49 @@
/// we are ready to destroy the JIT, the program exits.
class JITMemoryManager {
std::vector<sys::MemoryBlock> Blocks; // Memory blocks allocated by the JIT
- unsigned char *FunctionBase; // Start of the function body area
- unsigned char *CurStubPtr, *CurFunctionPtr;
+ 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
+ // 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);
- inline unsigned char *startFunctionBody();
- inline void endFunctionBody(unsigned char *FunctionEnd);
+
+ /// 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;
@@ -73,18 +300,71 @@
bool isManagingGOT() const {
return GOTBase != NULL;
}
+
+ /// deallocateMemForFunction - Deallocate all memory for the specified
+ /// function body.
+ void deallocateMemForFunction(const Function *F) {
+
+ }
};
}
JITMemoryManager::JITMemoryManager(bool useGOT) {
- // Allocate a 16M block of memory for functions
- sys::MemoryBlock FunBlock = getNewMemoryBlock(16 << 20);
+ // Allocate a 16M block of memory for functions.
+ sys::MemoryBlock MemBlock = getNewMemoryBlock(16 << 20);
- FunctionBase = reinterpret_cast<unsigned char*>(FunBlock.base());
+ unsigned char *MemBase = reinterpret_cast<unsigned char*>(MemBlock.base());
// Allocate stubs backwards from the base, allocate functions forward
// from the base.
- CurStubPtr = CurFunctionPtr = FunctionBase + 512*1024;// Use 512k for stubs
+ 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;
+ Mem2->ThisAllocated = 1;
+ Mem2->PrevAllocated = 0;
+ Mem2->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 = (unsigned char*)Mem1-(unsigned char*)Mem0;
+ Mem0->SetEndOfBlockSizeMarker();
+ Mem0->AddToFreeList(Mem2);
+
+ // Start out with the freelist pointing to Mem0.
+ FreeMemoryList = Mem0;
// Allocate the GOT.
GOTBase = NULL;
@@ -99,7 +379,7 @@
unsigned char *JITMemoryManager::allocateStub(unsigned StubSize) {
CurStubPtr -= StubSize;
- if (CurStubPtr < FunctionBase) {
+ if (CurStubPtr < StubBase) {
// FIXME: allocate a new block
std::cerr << "JIT ran out of memory for function stubs!\n";
abort();
@@ -107,17 +387,9 @@
return CurStubPtr;
}
-unsigned char *JITMemoryManager::startFunctionBody() {
- return CurFunctionPtr;
-}
-
-void JITMemoryManager::endFunctionBody(unsigned char *FunctionEnd) {
- assert(FunctionEnd > CurFunctionPtr);
- CurFunctionPtr = FunctionEnd;
-}
-
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);
@@ -324,28 +596,6 @@
}
-// 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);
-
-}
-
//===----------------------------------------------------------------------===//
// JITEmitter code.
//
@@ -418,16 +668,16 @@
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);
};
}
-MachineCodeEmitter *JIT::createEmitter(JIT &jit) {
- return new JITEmitter(jit);
-}
-
void *JITEmitter::getPointerToGlobal(GlobalValue *V, void *Reference,
bool DoesntNeedStub) {
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) {
@@ -461,10 +711,9 @@
}
void JITEmitter::startFunction(MachineFunction &F) {
- BufferBegin = CurBufferPtr = MemMgr.startFunctionBody();
-
- /// FIXME: implement out of space handling correctly!
- BufferEnd = (unsigned char*)(intptr_t)~0ULL;
+ uintptr_t ActualSize;
+ BufferBegin = CurBufferPtr = MemMgr.startFunctionBody(ActualSize);
+ BufferEnd = BufferBegin+ActualSize;
emitConstantPool(F.getConstantPool());
initJumpTableInfo(F.getJumpTableInfo());
@@ -477,9 +726,15 @@
}
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(CurBufferPtr);
+ MemMgr.endFunctionBody(F.getFunction(), BufferBegin, CurBufferPtr);
NumBytes += getCurrentPCOffset();
if (!Relocations.empty()) {
@@ -642,6 +897,14 @@
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
@@ -655,3 +918,29 @@
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);
+}
+
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