//===-- llvm/CodeGen/JITCodeEmitter.h - Code emission ----------*- C++ -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file 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
 // machine code will be written (memory or disk, f.e.).
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_CODEGEN_JITCODEEMITTER_H
 #define LLVM_CODEGEN_JITCODEEMITTER_H
 
 #include <string>

 #include <algorithm>

 #include "llvm/System/DataTypes.h"

 #include "llvm/Support/MathExtras.h"
 #include "llvm/CodeGen/MachineCodeEmitter.h"

 #include "llvm/ADT/DenseMap.h"

 
 using namespace std;
 
 namespace llvm {
 
 class MachineBasicBlock;
 class MachineConstantPool;
 class MachineJumpTableInfo;
 class MachineFunction;
 class MachineModuleInfo;
 class MachineRelocation;
 class Value;
 class GlobalValue;
 class Function;

 /// JITCodeEmitter - 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 JITCodeEmitter : public MachineCodeEmitter {
 public:
   virtual ~JITCodeEmitter() {}
 
   /// startFunction - This callback is invoked when the specified function is
   /// about to be code generated.  This initializes the BufferBegin/End/Ptr
   /// fields.
   ///
   virtual void startFunction(MachineFunction &F) = 0;
 
   /// 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.
   ///
   virtual bool finishFunction(MachineFunction &F) = 0;
   

   /// allocIndirectGV - Allocates and fills storage for an indirect
   /// GlobalValue, and returns the address.
   virtual void *allocIndirectGV(const GlobalValue *GV,
                                 const uint8_t *Buffer, size_t Size,
                                 unsigned Alignment) = 0;

 
   /// emitByte - This callback is invoked when a byte needs to be written to the
   /// output stream.
   ///
   void emitByte(uint8_t B) {
     if (CurBufferPtr != BufferEnd)
       *CurBufferPtr++ = B;
   }
 
   /// emitWordLE - This callback is invoked when a 32-bit word needs to be
   /// written to the output stream in little-endian format.
   ///
   void emitWordLE(uint32_t W) {
     if (4 <= BufferEnd-CurBufferPtr) {
       *CurBufferPtr++ = (uint8_t)(W >>  0);
       *CurBufferPtr++ = (uint8_t)(W >>  8);
       *CurBufferPtr++ = (uint8_t)(W >> 16);
       *CurBufferPtr++ = (uint8_t)(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.
   ///
   void emitWordBE(uint32_t W) {
     if (4 <= BufferEnd-CurBufferPtr) {
       *CurBufferPtr++ = (uint8_t)(W >> 24);
       *CurBufferPtr++ = (uint8_t)(W >> 16);
       *CurBufferPtr++ = (uint8_t)(W >>  8);
       *CurBufferPtr++ = (uint8_t)(W >>  0);
     } else {
       CurBufferPtr = BufferEnd;
     }
   }
 
   /// emitDWordLE - This callback is invoked when a 64-bit word needs to be
   /// written to the output stream in little-endian format.
   ///
   void emitDWordLE(uint64_t W) {
     if (8 <= BufferEnd-CurBufferPtr) {
       *CurBufferPtr++ = (uint8_t)(W >>  0);
       *CurBufferPtr++ = (uint8_t)(W >>  8);
       *CurBufferPtr++ = (uint8_t)(W >> 16);
       *CurBufferPtr++ = (uint8_t)(W >> 24);
       *CurBufferPtr++ = (uint8_t)(W >> 32);
       *CurBufferPtr++ = (uint8_t)(W >> 40);
       *CurBufferPtr++ = (uint8_t)(W >> 48);
       *CurBufferPtr++ = (uint8_t)(W >> 56);
     } else {
       CurBufferPtr = BufferEnd;
     }
   }
   
   /// emitDWordBE - This callback is invoked when a 64-bit word needs to be
   /// written to the output stream in big-endian format.
   ///
   void emitDWordBE(uint64_t W) {
     if (8 <= BufferEnd-CurBufferPtr) {
       *CurBufferPtr++ = (uint8_t)(W >> 56);
       *CurBufferPtr++ = (uint8_t)(W >> 48);
       *CurBufferPtr++ = (uint8_t)(W >> 40);
       *CurBufferPtr++ = (uint8_t)(W >> 32);
       *CurBufferPtr++ = (uint8_t)(W >> 24);
       *CurBufferPtr++ = (uint8_t)(W >> 16);
       *CurBufferPtr++ = (uint8_t)(W >>  8);
       *CurBufferPtr++ = (uint8_t)(W >>  0);
     } else {
       CurBufferPtr = BufferEnd;
     }
   }
 

   /// emitAlignment - Move the CurBufferPtr pointer up to the specified

   /// alignment (saturated to BufferEnd of course).
   void emitAlignment(unsigned Alignment) {
     if (Alignment == 0) Alignment = 1;
     uint8_t *NewPtr = (uint8_t*)RoundUpToAlignment((uintptr_t)CurBufferPtr,
                                                    Alignment);
     CurBufferPtr = std::min(NewPtr, BufferEnd);
   }
 
   /// emitAlignmentWithFill - Similar to emitAlignment, except that the
   /// extra bytes are filled with the provided byte.
   void emitAlignmentWithFill(unsigned Alignment, uint8_t Fill) {
     if (Alignment == 0) Alignment = 1;
     uint8_t *NewPtr = (uint8_t*)RoundUpToAlignment((uintptr_t)CurBufferPtr,
                                                    Alignment);
     // Fail if we don't have room.
     if (NewPtr > BufferEnd) {
       CurBufferPtr = BufferEnd;
       return;
     }
     while (CurBufferPtr < NewPtr) {
       *CurBufferPtr++ = Fill;
     }
   }
 
   /// emitULEB128Bytes - This callback is invoked when a ULEB128 needs to be
   /// written to the output stream.

   void emitULEB128Bytes(uint64_t Value, unsigned PadTo = 0) {

     do {
       uint8_t Byte = Value & 0x7f;
       Value >>= 7;

       if (Value || PadTo != 0) Byte |= 0x80;

       emitByte(Byte);
     } while (Value);

 
     if (PadTo) {
       do {
         uint8_t Byte = (PadTo > 1) ? 0x80 : 0x0;
         emitByte(Byte);
       } while (--PadTo);
     }

   }
   
   /// emitSLEB128Bytes - This callback is invoked when a SLEB128 needs to be
   /// written to the output stream.
   void emitSLEB128Bytes(int64_t Value) {
     int32_t Sign = Value >> (8 * sizeof(Value) - 1);
     bool IsMore;
   
     do {
       uint8_t Byte = Value & 0x7f;
       Value >>= 7;
       IsMore = Value != Sign || ((Byte ^ Sign) & 0x40) != 0;
       if (IsMore) Byte |= 0x80;
       emitByte(Byte);
     } while (IsMore);
   }
 
   /// emitString - This callback is invoked when a String needs to be
   /// written to the output stream.
   void emitString(const std::string &String) {
     for (unsigned i = 0, N = static_cast<unsigned>(String.size());
          i < N; ++i) {
       uint8_t C = String[i];
       emitByte(C);
     }
     emitByte(0);
   }
   
   /// emitInt32 - Emit a int32 directive.
   void emitInt32(uint32_t Value) {
     if (4 <= BufferEnd-CurBufferPtr) {
       *((uint32_t*)CurBufferPtr) = Value;
       CurBufferPtr += 4;
     } else {
       CurBufferPtr = BufferEnd;
     }
   }
 
   /// emitInt64 - Emit a int64 directive.
   void emitInt64(uint64_t Value) {
     if (8 <= BufferEnd-CurBufferPtr) {
       *((uint64_t*)CurBufferPtr) = Value;
       CurBufferPtr += 8;
     } else {
       CurBufferPtr = BufferEnd;
     }
   }
   
   /// emitInt32At - Emit the Int32 Value in Addr.
   void emitInt32At(uintptr_t *Addr, uintptr_t Value) {
     if (Addr >= (uintptr_t*)BufferBegin && Addr < (uintptr_t*)BufferEnd)
       (*(uint32_t*)Addr) = (uint32_t)Value;
   }
   
   /// emitInt64At - Emit the Int64 Value in Addr.
   void emitInt64At(uintptr_t *Addr, uintptr_t Value) {
     if (Addr >= (uintptr_t*)BufferBegin && Addr < (uintptr_t*)BufferEnd)
       (*(uint64_t*)Addr) = (uint64_t)Value;
   }
   
   
   /// emitLabel - Emits a label

   virtual void emitLabel(MCSymbol *Label) = 0;

 
   /// 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.
   virtual void *allocateSpace(uintptr_t Size, unsigned Alignment) {
     emitAlignment(Alignment);
     void *Result;
     
     // Check for buffer overflow.
     if (Size >= (uintptr_t)(BufferEnd-CurBufferPtr)) {
       CurBufferPtr = BufferEnd;
       Result = 0;
     } else {
       // Allocate the space.
       Result = CurBufferPtr;
       CurBufferPtr += Size;
     }
     
     return Result;
   }
 
   /// allocateGlobal - Allocate memory for a global.  Unlike allocateSpace,
   /// this method does not allocate memory in the current output buffer,
   /// because a global may live longer than the current function.
   virtual void *allocateGlobal(uintptr_t Size, unsigned Alignment) = 0;
 
   /// 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 uintptr_t getCurrentPCValue() const {
     return (uintptr_t)CurBufferPtr;
   }
 
   /// getCurrentPCOffset - Return the offset from the start of the emitted
   /// buffer that we are currently writing to.
   uintptr_t getCurrentPCOffset() const {
     return CurBufferPtr-BufferBegin;
   }
 
   /// earlyResolveAddresses - True if the code emitter can use symbol addresses 
   /// during code emission time. The JIT is capable of doing this because it
   /// creates jump tables or constant pools in memory on the fly while the
   /// object code emitters rely on a linker to have real addresses and should
   /// use relocations instead.
   bool earlyResolveAddresses() const { return true; }
 
   /// 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.
   ///
   virtual uintptr_t getConstantPoolEntryAddress(unsigned Index) const = 0;
 
   /// getJumpTableEntryAddress - Return the address of the jump table with index
   /// 'Index' in the function that last called initJumpTableInfo.
   ///
   virtual uintptr_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 uintptr_t getMachineBasicBlockAddress(MachineBasicBlock *MBB) const= 0;
 

   /// getLabelAddress - Return the address of the specified Label, only usable
   /// after the Label has been emitted.

   ///

   virtual uintptr_t getLabelAddress(MCSymbol *Label) const = 0;

   
   /// Specifies the MachineModuleInfo object. This is used for exception handling
   /// purposes.
   virtual void setModuleInfo(MachineModuleInfo* Info) = 0;

 
   /// getLabelLocations - Return the label locations map of the label IDs to
   /// their address.
   virtual DenseMap<MCSymbol*, uintptr_t> *getLabelLocations() { return 0; }

 };
 
 } // End llvm namespace
 
 #endif