LLVM API Documentation

llvm::MachineCodeEmitter Class Reference

#include <MachineCodeEmitter.h>

Inheritance diagram for llvm::MachineCodeEmitter:

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Collaboration diagram for llvm::MachineCodeEmitter:

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List of all members.

Public Member Functions

virtual ~MachineCodeEmitter ()
virtual void startFunction (MachineFunction &F)=0
virtual bool finishFunction (MachineFunction &F)=0
emitWord *methods *virtual
void 
startFunctionStub (unsigned StubSize)=0
virtual void * finishFunctionStub (const Function *F)=0
void emitByte (unsigned char B)
void emitWordLE (unsigned W)
void emitWordBE (unsigned W)
void emitAlignment (unsigned Alignment)
void * allocateSpace (intptr_t Size, unsigned Alignment)
virtual void StartMachineBasicBlock (MachineBasicBlock *MBB)=0
virtual intptr_t getCurrentPCValue () const
intptr_t getCurrentPCOffset () const
virtual void addRelocation (const MachineRelocation &MR)=0
virtual intptr_t getConstantPoolEntryAddress (unsigned Index) const=0
 FIXME: These should all be handled with relocations!
virtual intptr_t getJumpTableEntryAddress (unsigned Index) const=0
virtual intptr_t getMachineBasicBlockAddress (MachineBasicBlock *MBB) const=0

Protected Attributes

unsigned char * BufferBegin
unsigned char * BufferEnd
unsigned char * CurBufferPtr

Detailed Description

MachineCodeEmitter - This class defines two sorts of methods: those for emitting the actual bytes of machine code, and those for emitting auxillary structures, such as jump tables, relocations, etc.

Emission of machine code is complicated by the fact that we don't (in general) know the size of the machine code that we're about to emit before we emit it. As such, we preallocate a certain amount of memory, and set the BufferBegin/BufferEnd pointers to the start and end of the buffer. As we emit machine instructions, we advance the CurBufferPtr to indicate the location of the next byte to emit. In the case of a buffer overflow (we need to emit more machine code than we have allocated space for), the CurBufferPtr will saturate to BufferEnd and ignore stores. Once the entire function has been emitted, the overflow condition is checked, and if it has occurred, more memory is allocated, and we reemit the code into it.

Definition at line 49 of file MachineCodeEmitter.h.


Constructor & Destructor Documentation

virtual llvm::MachineCodeEmitter::~MachineCodeEmitter (  )  [inline, virtual]

Definition at line 62 of file MachineCodeEmitter.h.


Member Function Documentation

virtual void llvm::MachineCodeEmitter::startFunction ( MachineFunction F  )  [pure virtual]

startFunction - This callback is invoked when the specified function is about to be code generated. This initializes the BufferBegin/End/Ptr fields.

Implemented in llvm::ELFCodeEmitter.

virtual bool llvm::MachineCodeEmitter::finishFunction ( MachineFunction F  )  [pure virtual]

finishFunction - This callback is invoked when the specified function has finished code generation. If a buffer overflow has occurred, this method returns true (the callee is required to try again), otherwise it returns false.

Implemented in llvm::ELFCodeEmitter.

emitWord* methods* virtual void llvm::MachineCodeEmitter::startFunctionStub ( unsigned  StubSize  )  [pure virtual]

startFunctionStub - This callback is invoked when the JIT needs the address of a function that has not been code generated yet. The StubSize specifies the total size required by the stub. Stubs are not allowed to have constant pools, the can only use the other emitByte

Implemented in llvm::ELFCodeEmitter.

Referenced by llvm::X86JITInfo::emitFunctionStub(), llvm::PPCJITInfo::emitFunctionStub(), and llvm::AlphaJITInfo::emitFunctionStub().

virtual void* llvm::MachineCodeEmitter::finishFunctionStub ( const Function F  )  [pure virtual]

finishFunctionStub - This callback is invoked to terminate a function stub.

Implemented in llvm::ELFCodeEmitter.

Referenced by llvm::X86JITInfo::emitFunctionStub(), llvm::PPCJITInfo::emitFunctionStub(), and llvm::AlphaJITInfo::emitFunctionStub().

void llvm::MachineCodeEmitter::emitByte ( unsigned char  B  )  [inline]

emitByte - This callback is invoked when a byte needs to be written to the output stream.

Definition at line 93 of file MachineCodeEmitter.h.

References BufferEnd, and CurBufferPtr.

Referenced by llvm::X86JITInfo::emitFunctionStub().

void llvm::MachineCodeEmitter::emitWordLE ( unsigned  W  )  [inline]

emitWordLE - This callback is invoked when a 32-bit word needs to be written to the output stream in little-endian format.

Definition at line 101 of file MachineCodeEmitter.h.

References BufferEnd, and CurBufferPtr.

Referenced by llvm::X86JITInfo::emitFunctionStub(), and llvm::AlphaJITInfo::emitFunctionStub().

void llvm::MachineCodeEmitter::emitWordBE ( unsigned  W  )  [inline]

emitWordBE - This callback is invoked when a 32-bit word needs to be written to the output stream in big-endian format.

Definition at line 115 of file MachineCodeEmitter.h.

References BufferEnd, and CurBufferPtr.

Referenced by llvm::PPCJITInfo::emitFunctionStub().

void llvm::MachineCodeEmitter::emitAlignment ( unsigned  Alignment  )  [inline]

emitAlignment - Move the CurBufferPtr pointer up the the specified alignment (saturated to BufferEnd of course).

Definition at line 128 of file MachineCodeEmitter.h.

References BufferEnd, and CurBufferPtr.

Referenced by allocateSpace().

void* llvm::MachineCodeEmitter::allocateSpace ( intptr_t  Size,
unsigned  Alignment 
) [inline]

allocateSpace - Allocate a block of space in the current output buffer, returning null (and setting conditions to indicate buffer overflow) on failure. Alignment is the alignment in bytes of the buffer desired.

Definition at line 141 of file MachineCodeEmitter.h.

References BufferEnd, CurBufferPtr, and emitAlignment().

virtual void llvm::MachineCodeEmitter::StartMachineBasicBlock ( MachineBasicBlock MBB  )  [pure virtual]

StartMachineBasicBlock - This should be called by the target when a new basic block is about to be emitted. This way the MCE knows where the start of the block is, and can implement getMachineBasicBlockAddress.

Implemented in llvm::ELFCodeEmitter.

virtual intptr_t llvm::MachineCodeEmitter::getCurrentPCValue (  )  const [inline, virtual]

getCurrentPCValue - This returns the address that the next emitted byte will be output to.

Definition at line 164 of file MachineCodeEmitter.h.

References CurBufferPtr.

Referenced by llvm::X86JITInfo::emitFunctionStub(), llvm::PPCJITInfo::emitFunctionStub(), and llvm::AlphaJITInfo::emitFunctionStub().

intptr_t llvm::MachineCodeEmitter::getCurrentPCOffset (  )  const [inline]

getCurrentPCOffset - Return the offset from the start of the emitted buffer that we are currently writing to.

Definition at line 170 of file MachineCodeEmitter.h.

References BufferBegin, and CurBufferPtr.

virtual void llvm::MachineCodeEmitter::addRelocation ( const MachineRelocation MR  )  [pure virtual]

addRelocation - Whenever a relocatable address is needed, it should be noted with this interface.

Implemented in llvm::ELFCodeEmitter.

virtual intptr_t llvm::MachineCodeEmitter::getConstantPoolEntryAddress ( unsigned  Index  )  const [pure virtual]

FIXME: These should all be handled with relocations!

getConstantPoolEntryAddress - Return the address of the 'Index' entry in the constant pool that was last emitted with the emitConstantPool method.

Implemented in llvm::ELFCodeEmitter.

virtual intptr_t llvm::MachineCodeEmitter::getJumpTableEntryAddress ( unsigned  Index  )  const [pure virtual]

getJumpTableEntryAddress - Return the address of the jump table with index 'Index' in the function that last called initJumpTableInfo.

Implemented in llvm::ELFCodeEmitter.

virtual intptr_t llvm::MachineCodeEmitter::getMachineBasicBlockAddress ( MachineBasicBlock MBB  )  const [pure virtual]

getMachineBasicBlockAddress - Return the address of the specified MachineBasicBlock, only usable after the label for the MBB has been emitted.

Implemented in llvm::ELFCodeEmitter.

Referenced by llvm::X86JITInfo::resolveBBRefs(), llvm::PPCJITInfo::resolveBBRefs(), and llvm::AlphaJITInfo::resolveBBRefs().


Member Data Documentation

unsigned char* llvm::MachineCodeEmitter::BufferBegin [protected]

BufferBegin/BufferEnd - Pointers to the start and end of the memory allocated for this code buffer.

Definition at line 53 of file MachineCodeEmitter.h.

Referenced by getCurrentPCOffset().

unsigned char * llvm::MachineCodeEmitter::BufferEnd [protected]

Definition at line 53 of file MachineCodeEmitter.h.

Referenced by allocateSpace(), emitAlignment(), emitByte(), emitWordBE(), and emitWordLE().

unsigned char* llvm::MachineCodeEmitter::CurBufferPtr [protected]

CurBufferPtr - Pointer to the next byte of memory to fill when emitting code. This is guranteed to be in the range [BufferBegin,BufferEnd]. If this pointer is at BufferEnd, it will never move due to code emission, and all code emission requests will be ignored (this is the buffer overflow condition).

Definition at line 60 of file MachineCodeEmitter.h.

Referenced by allocateSpace(), emitAlignment(), emitByte(), emitWordBE(), emitWordLE(), getCurrentPCOffset(), and getCurrentPCValue().


The documentation for this class was generated from the following file: