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X86InstrBuilder.h

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00001 //===-- X86InstrBuilder.h - Functions to aid building x86 insts -*- C++ -*-===//
00002 // 
00003 //                     The LLVM Compiler Infrastructure
00004 //
00005 // This file was developed by the LLVM research group and is distributed under
00006 // the University of Illinois Open Source License. See LICENSE.TXT for details.
00007 // 
00008 //===----------------------------------------------------------------------===//
00009 //
00010 // This file exposes functions that may be used with BuildMI from the
00011 // MachineInstrBuilder.h file to handle X86'isms in a clean way.
00012 //
00013 // The BuildMem function may be used with the BuildMI function to add entire
00014 // memory references in a single, typed, function call.  X86 memory references
00015 // can be very complex expressions (described in the README), so wrapping them
00016 // up behind an easier to use interface makes sense.  Descriptions of the
00017 // functions are included below.
00018 //
00019 // For reference, the order of operands for memory references is:
00020 // (Operand), Base, Scale, Index, Displacement.
00021 //
00022 //===----------------------------------------------------------------------===//
00023 
00024 #ifndef X86INSTRBUILDER_H
00025 #define X86INSTRBUILDER_H
00026 
00027 #include "llvm/CodeGen/MachineInstrBuilder.h"
00028 
00029 namespace llvm {
00030 
00031 /// X86AddressMode - This struct holds a generalized full x86 address mode.
00032 /// The base register can be a frame index, which will eventually be replaced
00033 /// with BP or SP and Disp being offsetted accordingly.  The displacement may
00034 /// also include the offset of a global value.
00035 struct X86AddressMode {
00036     enum {
00037       UnknownBase,
00038       RegBase,
00039       FrameIndexBase,
00040     } BaseType;
00041 
00042     union {
00043       unsigned Reg;
00044       int FrameIndex;
00045     } Base;
00046 
00047     unsigned Scale;
00048     unsigned IndexReg;
00049     unsigned Disp;
00050     GlobalValue *GV;
00051 
00052     X86AddressMode() : BaseType(UnknownBase), GV(NULL) {}
00053 };
00054 
00055 /// addDirectMem - This function is used to add a direct memory reference to the
00056 /// current instruction -- that is, a dereference of an address in a register,
00057 /// with no scale, index or displacement. An example is: DWORD PTR [EAX].
00058 ///
00059 inline const MachineInstrBuilder &addDirectMem(const MachineInstrBuilder &MIB,
00060                                                unsigned Reg) {
00061   // Because memory references are always represented with four
00062   // values, this adds: Reg, [1, NoReg, 0] to the instruction.
00063   return MIB.addReg(Reg).addZImm(1).addReg(0).addSImm(0);
00064 }
00065 
00066 
00067 /// addRegOffset - This function is used to add a memory reference of the form
00068 /// [Reg + Offset], i.e., one with no scale or index, but with a
00069 /// displacement. An example is: DWORD PTR [EAX + 4].
00070 ///
00071 inline const MachineInstrBuilder &addRegOffset(const MachineInstrBuilder &MIB,
00072                                                unsigned Reg, int Offset) {
00073   return MIB.addReg(Reg).addZImm(1).addReg(0).addSImm(Offset);
00074 }
00075 
00076 inline const MachineInstrBuilder &addFullAddress(const MachineInstrBuilder &MIB,
00077                                                  const X86AddressMode &AM) {
00078   assert (AM.Scale == 1 || AM.Scale == 2 || AM.Scale == 4 || AM.Scale == 8);
00079 
00080   if (AM.BaseType == X86AddressMode::RegBase)
00081     MIB.addReg(AM.Base.Reg);
00082   else if (AM.BaseType == X86AddressMode::FrameIndexBase)
00083     MIB.addFrameIndex(AM.Base.FrameIndex);
00084   else
00085     assert (0);
00086   MIB.addZImm(AM.Scale).addReg(AM.IndexReg);
00087   if (AM.GV)
00088     return MIB.addGlobalAddress(AM.GV, false, AM.Disp);
00089   else
00090     return MIB.addSImm(AM.Disp);
00091 }
00092 
00093 /// addFrameReference - This function is used to add a reference to the base of
00094 /// an abstract object on the stack frame of the current function.  This
00095 /// reference has base register as the FrameIndex offset until it is resolved.
00096 /// This allows a constant offset to be specified as well...
00097 ///
00098 inline const MachineInstrBuilder &
00099 addFrameReference(const MachineInstrBuilder &MIB, int FI, int Offset = 0) {
00100   return MIB.addFrameIndex(FI).addZImm(1).addReg(0).addSImm(Offset);
00101 }
00102 
00103 /// addConstantPoolReference - This function is used to add a reference to the
00104 /// base of a constant value spilled to the per-function constant pool.  The
00105 /// reference has base register ConstantPoolIndex offset which is retained until
00106 /// either machine code emission or assembly output.  This allows an optional
00107 /// offset to be added as well.
00108 ///
00109 inline const MachineInstrBuilder &
00110 addConstantPoolReference(const MachineInstrBuilder &MIB, unsigned CPI,
00111                          int Offset = 0) {
00112   return MIB.addConstantPoolIndex(CPI).addZImm(1).addReg(0).addSImm(Offset);
00113 }
00114 
00115 } // End llvm namespace
00116 
00117 #endif