//===-- llvm/CodeGen/MachineCodeEmitter.h - Code emission -------*- C++ -*-===//
//
+// 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 an abstract interface that is used by the machine code
// emission framework to output the code. This allows machine code emission to
// be separated from concerns such as resolution of call targets, and where the
//
//===----------------------------------------------------------------------===//
-#ifndef LLVM_CODEGEN_MACHINE_CODE_EMITTER_H
-#define LLVM_CODEGEN_MACHINE_CODE_EMITTER_H
+#ifndef LLVM_CODEGEN_MACHINECODEEMITTER_H
+#define LLVM_CODEGEN_MACHINECODEEMITTER_H
+
+#include "llvm/Support/DataTypes.h"
+#include <vector>
+
+namespace llvm {
-#include <string>
-#include "Support/DataTypes.h"
-class MachineFunction;
class MachineBasicBlock;
class MachineConstantPool;
+class MachineJumpTableInfo;
+class MachineFunction;
+class MachineRelocation;
class Value;
class GlobalValue;
class Function;
-struct MachineCodeEmitter {
+/// 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.
+///
+class MachineCodeEmitter {
+protected:
+ /// BufferBegin/BufferEnd - Pointers to the start and end of the memory
+ /// allocated for this code buffer.
+ unsigned char *BufferBegin, *BufferEnd;
+
+ /// 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).
+ unsigned char *CurBufferPtr;
+public:
virtual ~MachineCodeEmitter() {}
/// startFunction - This callback is invoked when the specified function is
- /// about to be code generated.
+ /// about to be code generated. This initializes the BufferBegin/End/Ptr
+ /// fields.
///
- virtual void startFunction(MachineFunction &F) {}
-
+ virtual void startFunction(MachineFunction &F) = 0;
+
/// finishFunction - This callback is invoked when the specified function has
- /// finished code generation.
+ /// finished code generation. If a buffer overflow has occurred, this method
+ /// returns true (the callee is required to try again), otherwise it returns
+ /// false.
///
- virtual void finishFunction(MachineFunction &F) {}
-
- /// emitConstantPool - This callback is invoked to output the constant pool
- /// for the function.
- virtual void emitConstantPool(MachineConstantPool *MCP) {}
-
+ virtual bool finishFunction(MachineFunction &F) = 0;
+
/// 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 emit* methods.
+ /// have constant pools, the can only use the other emitByte*/emitWord*
+ /// methods.
///
- virtual void startFunctionStub(const Function &F, unsigned StubSize) {}
+ virtual void startFunctionStub(unsigned StubSize, unsigned Alignment = 1) = 0;
/// finishFunctionStub - This callback is invoked to terminate a function
/// stub.
///
- virtual void *finishFunctionStub(const Function &F) { return 0; }
+ virtual void *finishFunctionStub(const Function *F) = 0;
/// emitByte - This callback is invoked when a byte needs to be written to the
/// output stream.
///
- virtual void emitByte(unsigned char B) {}
+ void emitByte(unsigned char B) {
+ if (CurBufferPtr != BufferEnd)
+ *CurBufferPtr++ = B;
+ }
- /// emitWord - This callback is invoked when a word needs to be written to the
- /// output stream.
+ /// emitWordLE - This callback is invoked when a 32-bit word needs to be
+ /// written to the output stream in little-endian format.
///
- virtual void emitWord(unsigned W) = 0;
-
- /// getGlobalValueAddress - This method is used to get the address of the
- /// specified global value. In some cases, however, the address may not yet
- /// be known at the point that the method is called (for example, getting the
- /// address of a function which has not yet been code generated). If this is
- /// the case, the function returns zero, and the callee has to be able to
- /// handle the situation.
+ void emitWordLE(unsigned W) {
+ if (CurBufferPtr+4 <= BufferEnd) {
+ *CurBufferPtr++ = (unsigned char)(W >> 0);
+ *CurBufferPtr++ = (unsigned char)(W >> 8);
+ *CurBufferPtr++ = (unsigned char)(W >> 16);
+ *CurBufferPtr++ = (unsigned char)(W >> 24);
+ } else {
+ CurBufferPtr = BufferEnd;
+ }
+ }
+
+ /// emitWordBE - This callback is invoked when a 32-bit word needs to be
+ /// written to the output stream in big-endian format.
///
- virtual uint64_t getGlobalValueAddress(GlobalValue *V) = 0;
- virtual uint64_t getGlobalValueAddress(const std::string &Name) = 0;
-
- // getConstantPoolEntryAddress - Return the address of the 'Index' entry in
- // the constant pool that was last emitted with the 'emitConstantPool' method.
- //
- virtual uint64_t getConstantPoolEntryAddress(unsigned Index) = 0;
-
-
- // getCurrentPCValue - This returns the address that the next emitted byte
- // will be output to.
- //
- virtual uint64_t getCurrentPCValue() = 0;
-
- // forceCompilationOf - Force the compilation of the specified function, and
- // return its address, because we REALLY need the address now.
- //
- // FIXME: This is JIT specific!
- //
- virtual uint64_t forceCompilationOf(Function *F) = 0;
+ void emitWordBE(unsigned W) {
+ if (CurBufferPtr+4 <= BufferEnd) {
+ *CurBufferPtr++ = (unsigned char)(W >> 24);
+ *CurBufferPtr++ = (unsigned char)(W >> 16);
+ *CurBufferPtr++ = (unsigned char)(W >> 8);
+ *CurBufferPtr++ = (unsigned char)(W >> 0);
+ } else {
+ CurBufferPtr = BufferEnd;
+ }
+ }
+
+ /// emitAlignment - Move the CurBufferPtr pointer up the the specified
+ /// alignment (saturated to BufferEnd of course).
+ void emitAlignment(unsigned Alignment) {
+ if (Alignment == 0) Alignment = 1;
+ // Move the current buffer ptr up to the specified alignment.
+ CurBufferPtr =
+ (unsigned char*)(((intptr_t)CurBufferPtr+Alignment-1) &
+ ~(intptr_t)(Alignment-1));
+ if (CurBufferPtr > BufferEnd)
+ CurBufferPtr = BufferEnd;
+ }
+ /// 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.
+ void *allocateSpace(intptr_t Size, unsigned Alignment) {
+ emitAlignment(Alignment);
+ void *Result = CurBufferPtr;
+
+ // Allocate the space.
+ CurBufferPtr += Size;
+
+ // Check for buffer overflow.
+ if (CurBufferPtr >= BufferEnd) {
+ CurBufferPtr = BufferEnd;
+ Result = 0;
+ }
+ return Result;
+ }
+
+ /// 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.
+ virtual void StartMachineBasicBlock(MachineBasicBlock *MBB) = 0;
+
+ /// getCurrentPCValue - This returns the address that the next emitted byte
+ /// will be output to.
+ ///
+ virtual intptr_t getCurrentPCValue() const {
+ return (intptr_t)CurBufferPtr;
+ }
+
+ /// getCurrentPCOffset - Return the offset from the start of the emitted
+ /// buffer that we are currently writing to.
+ intptr_t getCurrentPCOffset() const {
+ return CurBufferPtr-BufferBegin;
+ }
- /// createDebugEmitter - Return a dynamically allocated machine
- /// code emitter, which just prints the opcodes and fields out the cout. This
- /// can be used for debugging users of the MachineCodeEmitter interface.
+ /// addRelocation - Whenever a relocatable address is needed, it should be
+ /// noted with this interface.
+ virtual void addRelocation(const MachineRelocation &MR) = 0;
+
+
+ /// 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.
///
- static MachineCodeEmitter *createDebugEmitter();
+ virtual intptr_t getConstantPoolEntryAddress(unsigned Index) const = 0;
- /// createFilePrinterEmitter - Return a dynamically allocated
- /// machine code emitter, which prints binary code to a file. This
- /// can be used for debugging users of the MachineCodeEmitter interface.
+ /// getJumpTableEntryAddress - Return the address of the jump table with index
+ /// 'Index' in the function that last called initJumpTableInfo.
///
- static MachineCodeEmitter *createFilePrinterEmitter(MachineCodeEmitter&);
+ virtual intptr_t getJumpTableEntryAddress(unsigned Index) const = 0;
+
+ /// getMachineBasicBlockAddress - Return the address of the specified
+ /// MachineBasicBlock, only usable after the label for the MBB has been
+ /// emitted.
+ ///
+ virtual intptr_t getMachineBasicBlockAddress(MachineBasicBlock *MBB) const= 0;
};
+} // End llvm namespace
+
#endif
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