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//===-- llvm/CodeGen/JITCodeEmitter.h - Code emission ----------*- C++ -*-===//
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// The LLVM Compiler Infrastructure
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//===----------------------------------------------------------------------===//
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// This file defines an abstract interface that is used by the machine code
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// emission framework to output the code. This allows machine code emission to
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// be separated from concerns such as resolution of call targets, and where the
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// machine code will be written (memory or disk, f.e.).
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CODEGEN_JITCODEEMITTER_H
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#define LLVM_CODEGEN_JITCODEEMITTER_H
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#include "llvm/System/DataTypes.h"
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#include "llvm/Support/MathExtras.h"
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#include "llvm/CodeGen/MachineCodeEmitter.h"
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class MachineBasicBlock;
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class MachineConstantPool;
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class MachineJumpTableInfo;
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class MachineFunction;
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class MachineModuleInfo;
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class MachineRelocation;
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/// JITCodeEmitter - This class defines two sorts of methods: those for
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/// emitting the actual bytes of machine code, and those for emitting auxillary
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/// structures, such as jump tables, relocations, etc.
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/// Emission of machine code is complicated by the fact that we don't (in
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/// general) know the size of the machine code that we're about to emit before
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/// we emit it. As such, we preallocate a certain amount of memory, and set the
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/// BufferBegin/BufferEnd pointers to the start and end of the buffer. As we
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/// emit machine instructions, we advance the CurBufferPtr to indicate the
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/// location of the next byte to emit. In the case of a buffer overflow (we
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/// need to emit more machine code than we have allocated space for), the
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/// CurBufferPtr will saturate to BufferEnd and ignore stores. Once the entire
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/// function has been emitted, the overflow condition is checked, and if it has
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/// occurred, more memory is allocated, and we reemit the code into it.
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class JITCodeEmitter : public MachineCodeEmitter {
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virtual ~JITCodeEmitter() {}
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/// startFunction - This callback is invoked when the specified function is
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/// about to be code generated. This initializes the BufferBegin/End/Ptr
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virtual void startFunction(MachineFunction &F) = 0;
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/// finishFunction - This callback is invoked when the specified function has
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/// finished code generation. If a buffer overflow has occurred, this method
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/// returns true (the callee is required to try again), otherwise it returns
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virtual bool finishFunction(MachineFunction &F) = 0;
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/// allocIndirectGV - Allocates and fills storage for an indirect
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/// GlobalValue, and returns the address.
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virtual void *allocIndirectGV(const GlobalValue *GV,
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const uint8_t *Buffer, size_t Size,
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unsigned Alignment) = 0;
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/// emitByte - This callback is invoked when a byte needs to be written to the
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void emitByte(uint8_t B) {
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if (CurBufferPtr != BufferEnd)
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/// emitWordLE - This callback is invoked when a 32-bit word needs to be
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/// written to the output stream in little-endian format.
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void emitWordLE(uint32_t W) {
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if (4 <= BufferEnd-CurBufferPtr) {
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*CurBufferPtr++ = (uint8_t)(W >> 0);
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*CurBufferPtr++ = (uint8_t)(W >> 8);
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*CurBufferPtr++ = (uint8_t)(W >> 16);
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*CurBufferPtr++ = (uint8_t)(W >> 24);
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CurBufferPtr = BufferEnd;
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/// emitWordBE - This callback is invoked when a 32-bit word needs to be
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/// written to the output stream in big-endian format.
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void emitWordBE(uint32_t W) {
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if (4 <= BufferEnd-CurBufferPtr) {
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*CurBufferPtr++ = (uint8_t)(W >> 24);
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*CurBufferPtr++ = (uint8_t)(W >> 16);
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*CurBufferPtr++ = (uint8_t)(W >> 8);
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*CurBufferPtr++ = (uint8_t)(W >> 0);
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CurBufferPtr = BufferEnd;
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/// emitDWordLE - This callback is invoked when a 64-bit word needs to be
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/// written to the output stream in little-endian format.
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void emitDWordLE(uint64_t W) {
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if (8 <= BufferEnd-CurBufferPtr) {
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*CurBufferPtr++ = (uint8_t)(W >> 0);
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*CurBufferPtr++ = (uint8_t)(W >> 8);
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*CurBufferPtr++ = (uint8_t)(W >> 16);
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*CurBufferPtr++ = (uint8_t)(W >> 24);
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*CurBufferPtr++ = (uint8_t)(W >> 32);
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*CurBufferPtr++ = (uint8_t)(W >> 40);
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*CurBufferPtr++ = (uint8_t)(W >> 48);
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*CurBufferPtr++ = (uint8_t)(W >> 56);
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CurBufferPtr = BufferEnd;
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/// emitDWordBE - This callback is invoked when a 64-bit word needs to be
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/// written to the output stream in big-endian format.
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void emitDWordBE(uint64_t W) {
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if (8 <= BufferEnd-CurBufferPtr) {
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*CurBufferPtr++ = (uint8_t)(W >> 56);
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*CurBufferPtr++ = (uint8_t)(W >> 48);
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*CurBufferPtr++ = (uint8_t)(W >> 40);
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*CurBufferPtr++ = (uint8_t)(W >> 32);
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*CurBufferPtr++ = (uint8_t)(W >> 24);
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*CurBufferPtr++ = (uint8_t)(W >> 16);
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*CurBufferPtr++ = (uint8_t)(W >> 8);
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*CurBufferPtr++ = (uint8_t)(W >> 0);
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CurBufferPtr = BufferEnd;
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/// emitAlignment - Move the CurBufferPtr pointer up to the specified
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/// alignment (saturated to BufferEnd of course).
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void emitAlignment(unsigned Alignment) {
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if (Alignment == 0) Alignment = 1;
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uint8_t *NewPtr = (uint8_t*)RoundUpToAlignment((uintptr_t)CurBufferPtr,
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CurBufferPtr = std::min(NewPtr, BufferEnd);
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/// emitAlignmentWithFill - Similar to emitAlignment, except that the
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/// extra bytes are filled with the provided byte.
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void emitAlignmentWithFill(unsigned Alignment, uint8_t Fill) {
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if (Alignment == 0) Alignment = 1;
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uint8_t *NewPtr = (uint8_t*)RoundUpToAlignment((uintptr_t)CurBufferPtr,
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// Fail if we don't have room.
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if (NewPtr > BufferEnd) {
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CurBufferPtr = BufferEnd;
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while (CurBufferPtr < NewPtr) {
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*CurBufferPtr++ = Fill;
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/// emitULEB128Bytes - This callback is invoked when a ULEB128 needs to be
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/// written to the output stream.
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void emitULEB128Bytes(uint64_t Value) {
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uint8_t Byte = Value & 0x7f;
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if (Value) Byte |= 0x80;
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/// emitSLEB128Bytes - This callback is invoked when a SLEB128 needs to be
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/// written to the output stream.
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void emitSLEB128Bytes(int64_t Value) {
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int32_t Sign = Value >> (8 * sizeof(Value) - 1);
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uint8_t Byte = Value & 0x7f;
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IsMore = Value != Sign || ((Byte ^ Sign) & 0x40) != 0;
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if (IsMore) Byte |= 0x80;
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/// emitString - This callback is invoked when a String needs to be
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/// written to the output stream.
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void emitString(const std::string &String) {
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for (unsigned i = 0, N = static_cast<unsigned>(String.size());
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uint8_t C = String[i];
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/// emitInt32 - Emit a int32 directive.
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void emitInt32(uint32_t Value) {
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if (4 <= BufferEnd-CurBufferPtr) {
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*((uint32_t*)CurBufferPtr) = Value;
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CurBufferPtr = BufferEnd;
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/// emitInt64 - Emit a int64 directive.
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void emitInt64(uint64_t Value) {
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if (8 <= BufferEnd-CurBufferPtr) {
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*((uint64_t*)CurBufferPtr) = Value;
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CurBufferPtr = BufferEnd;
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/// emitInt32At - Emit the Int32 Value in Addr.
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void emitInt32At(uintptr_t *Addr, uintptr_t Value) {
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if (Addr >= (uintptr_t*)BufferBegin && Addr < (uintptr_t*)BufferEnd)
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(*(uint32_t*)Addr) = (uint32_t)Value;
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/// emitInt64At - Emit the Int64 Value in Addr.
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void emitInt64At(uintptr_t *Addr, uintptr_t Value) {
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if (Addr >= (uintptr_t*)BufferBegin && Addr < (uintptr_t*)BufferEnd)
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(*(uint64_t*)Addr) = (uint64_t)Value;
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/// emitLabel - Emits a label
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virtual void emitLabel(uint64_t LabelID) = 0;
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/// allocateSpace - Allocate a block of space in the current output buffer,
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/// returning null (and setting conditions to indicate buffer overflow) on
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/// failure. Alignment is the alignment in bytes of the buffer desired.
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virtual void *allocateSpace(uintptr_t Size, unsigned Alignment) {
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emitAlignment(Alignment);
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// Check for buffer overflow.
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if (Size >= (uintptr_t)(BufferEnd-CurBufferPtr)) {
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CurBufferPtr = BufferEnd;
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// Allocate the space.
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Result = CurBufferPtr;
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CurBufferPtr += Size;
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/// allocateGlobal - Allocate memory for a global. Unlike allocateSpace,
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/// this method does not allocate memory in the current output buffer,
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/// because a global may live longer than the current function.
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virtual void *allocateGlobal(uintptr_t Size, unsigned Alignment) = 0;
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/// StartMachineBasicBlock - This should be called by the target when a new
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/// basic block is about to be emitted. This way the MCE knows where the
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/// start of the block is, and can implement getMachineBasicBlockAddress.
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virtual void StartMachineBasicBlock(MachineBasicBlock *MBB) = 0;
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/// getCurrentPCValue - This returns the address that the next emitted byte
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/// will be output to.
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virtual uintptr_t getCurrentPCValue() const {
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return (uintptr_t)CurBufferPtr;
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/// getCurrentPCOffset - Return the offset from the start of the emitted
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/// buffer that we are currently writing to.
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uintptr_t getCurrentPCOffset() const {
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return CurBufferPtr-BufferBegin;
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/// earlyResolveAddresses - True if the code emitter can use symbol addresses
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/// during code emission time. The JIT is capable of doing this because it
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/// creates jump tables or constant pools in memory on the fly while the
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/// object code emitters rely on a linker to have real addresses and should
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/// use relocations instead.
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bool earlyResolveAddresses() const { return true; }
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/// addRelocation - Whenever a relocatable address is needed, it should be
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/// noted with this interface.
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virtual void addRelocation(const MachineRelocation &MR) = 0;
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/// FIXME: These should all be handled with relocations!
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/// getConstantPoolEntryAddress - Return the address of the 'Index' entry in
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/// the constant pool that was last emitted with the emitConstantPool method.
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virtual uintptr_t getConstantPoolEntryAddress(unsigned Index) const = 0;
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/// getJumpTableEntryAddress - Return the address of the jump table with index
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/// 'Index' in the function that last called initJumpTableInfo.
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virtual uintptr_t getJumpTableEntryAddress(unsigned Index) const = 0;
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/// getMachineBasicBlockAddress - Return the address of the specified
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/// MachineBasicBlock, only usable after the label for the MBB has been
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virtual uintptr_t getMachineBasicBlockAddress(MachineBasicBlock *MBB) const= 0;
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/// getLabelAddress - Return the address of the specified LabelID, only usable
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/// after the LabelID has been emitted.
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virtual uintptr_t getLabelAddress(uint64_t LabelID) const = 0;
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/// Specifies the MachineModuleInfo object. This is used for exception handling
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virtual void setModuleInfo(MachineModuleInfo* Info) = 0;
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} // End llvm namespace