我编写了一个编译器，我可以将c程序编译到中间代码。我已经使用了javacc工具。
如何为它生成MachineCode？ 我有一个程序用于各种指令集，其寻址模式，指令格式但我无法理解它？ 任何人都可以帮我解释一下代码吗？ 另外我不知道如何从中间代码运行到机器代码？
以下是该计划：
#include<stdio.h>
#include<stdlib.h>
#define MAXCODE 100
typedef unsigned char USC;
USC code[MAXCODE];
USC data[4];
short int dataIdx;
unsigned int cc=0;
unsigned int startCount,endCount;
//do effective Address Calculation
void doEAC(short int mod,short int rm)
{
dataIdx=0;
switch(mod)
{
case 3:
break;
case 0:
if(rm == 6) //110 - direct address
{
code[cc++] = data[dataIdx++];
code[cc++] = data[dataIdx++];
}
break;
case 1:
code[cc++] = data[dataIdx++];
break;
case 2:
code[cc++] = data[dataIdx++];
code[cc++] = data[dataIdx++];
break;
}
}
//register or memory to or from register
void moveRM2R(USC d,USC w,USC mod,USC reg, USC rm)
{
USC c;
// 1 0 0 0 1 0
c = 0x88; // why this value?
c = c | (d << 1); //why this value?
c = c | w; //kya aayegi value?
code[cc++] = c; //why this value?
c = 0x0; //why this value?
c = c | (mod << 6); //why this value?
c = c | (reg << 3); //why this value?
c = c | rm ; //why this value?
code[cc++] = c; //why this value?
doEAC(mod,rm); //how they calculated above
}
//Immediate register or memory
void moveImm2RM(USC w, USC mod, USC rm)
{
USC c;
c = 0xc6;
c = c | w;
code[cc++] = c;
c = 0x0;
c = c | (mod << 6);
c = c | rm;
code[cc++] = c;
doEAC(mod,rm);
code[cc++] = data[dataIdx++];
if(w==1)
code[cc++] = data[dataIdx++];
}
//move immediate to register
void moveImm2R(USC w,USC reg)
{
USC c;
c = 0xb0;
c = c | (w << 3);
c = c | reg;
code[cc++]=c;
dataIdx = 0;
code[cc++] = data[dataIdx++];
if(w==1)
code[cc++] = data[dataIdx++];
}
//Move Memory to accumulator
void moveMem2Acc(USC w)
{
USC c;
c = 0xb0;
c = c | w;
code[cc++] = c;
dataIdx = 0;
code[cc++] = data[dataIdx++];
code[cc++] = data[dataIdx++];
}
//Move accumulator to memory
void moveAcc2Mem(USC w)
{
USC c;
c = 0xb2;
c = c | w;
code[cc++] = c;
dataIdx = 0;
code[cc++] = data[dataIdx++];
code[cc++] = data[dataIdx++];
}
//Move register or memory to segment register
void moveRM2SegR(USC mod, USC sreg, USC rm)
{
USC c;
c = 0x8e;
code[cc++] = c;
c = 0x0;
c = c | (mod << 6);
c = c | (sreg << 3);
c = c | rm;
code[cc++]=c;
doEAC(mod,rm);
}
//Move segment register to register or memory
void moveSegR2RM(USC mod, USC sreg, USC rm)
{
USC c;
c = 0x8c;
code[cc++] = c;
c = 0x0;
c = c | (mod << 6);
c = c | (sreg << 3);
c = c | rm;
code[cc++]=c;
doEAC(mod,rm);
}
//push data on reg or memory on stack
void pushRM(USC mod, USC rm)
{
USC c;
c = 0xff;
code[cc++] = c;
c = 0x00;
c = c | (mod << 6);
c = c | (0x06 << 3); //mod 110 rm
c = c | rm;
code[cc++] = c;
doEAC(mod,rm);
}
//push data on reg on stack
void pushR(USC reg)
{
USC c;
c = 0x40;
c = c | reg;
code[cc++] = c;
}
//push segment reg on stack
void pushSR(USC sreg)
{
USC c;
c = 0x0;
c = c | (sreg << 3);
c = c | 0x6; //000 reg 110
code[cc++] = c;
}
//pop stack into reg or mem
//1000 1111 - mod 000 r/m
void pop2RM(USC mod, USC rm)
{
USC c;
c = 0x8f;
code[cc++] = c;
c = 0x0;
c = c | (mod << 6);
c = c | rm;
code[cc++] = c;
doEAC(mod,rm);
}
//pop into a reg
//0101 1reg
void pop2R(USC reg)
{
USC c;
c = 0x58;
c = c | reg;
code[cc++] = c;
}
//pop into a seg reg
//000 sreg 111
void pop2SR(USC sreg)
{
USC c;
c = 0x0;
c = c | (sreg << 3);
c = c | 0x07;
code[cc++] = c;
}
//exchange register or memory with register
// 1000 011w - mod reg rm
void exchangeRM2R(USC w, USC mod, USC reg, USC rm)
{
USC c;
c = 0x86;
c = c | w;
code[cc++] = c;
c = 0x0;
c = c | (mod << 6);
c = c | (reg << 3);
c = c | reg;
code[cc++] = c;
doEAC(mod,rm);
}
void exchangeR2Acc(USC reg)
{
USC c;
c = 0x90;
c = c | reg;
code[cc++] = c;
}
void printCode()
{
int i;
for(i=startCount;i<endCount;i++)
printf("\t%0x\t",code[i]);
printf("\n");
}
int main()
{
int i;
USC d,w,mod,reg,sreg,rm,data1,data2,addrlow,addrhigh;
//register or memory to or from register
//void moveRM2R(USC d,USC w,USC mod,USC reg, USC rm)
startCount = cc;//what is it doing?
printf("\nMOV CX,AX Move AX register to CX register\n");
d = 0x01; //why this value? memory mode with 8 bit displacement
w = 0x01; //why this value? memory mode with 8 bit displacement
mod = 0x11; //why this value? Register Mode(No Displacement)
rm = 0x01; //why this value? memory mode with 8 bit displacement
reg = 0x00; //why this value? memory mode with no displacement
moveRM2R(d,w,mod,reg,rm);
endCount = cc;
printCode();
//Move Immediate data to register or memory
//void moveImm2RM(USC w, USC mod, USC rm, USC data1, USC data2)
startCount = cc;
printf("\nMOV DX, #4050 - move an immediate data to DX reg\n");
w = 0x01;
mod = 0x11;
rm = 0x03;
data[0] = 0x40;
data[1]= 0x50;
moveImm2RM(w, mod, rm);
endCount=cc;
printCode();
//move immediate to register
//void moveImm2R(USC w,USC reg)
printf("\nMov SI, #4050 - Move a immediate number to SI index reg\n");
startCount = cc;
w = 1;
reg = 0x06;
data[0] = 0x40;
data[1] = 0x50;
moveImm2R(w,reg);
endCount=cc;
printCode();
printf("\nMov AX, 2025 - Move the contents of the memory 2025 into accumulator\n");
startCount = cc;
w = 1;
//Move Memory to accumulator
//void moveMem2Acc(USC w)
w = 0x01;
data[0] = 0x25; //addrlow
data[1] = 0x20; //addrhigh;
moveMem2Acc(w);
endCount=cc;
printCode();
//Move accumulator to memory
//void moveAcc2Mem(USC w)
printf("\nMove the content of acc to a mem addressed by 2025\n");
startCount = cc;
w = 0x01;
data[0] = 0x25; //addrlow
data[1] = 0x20; //addrhigh;
moveAcc2Mem(w);
endCount=cc;
printCode();
//Move register or memory to segment register
//void moveRM2SegR(USC mod, USC sreg, USC rm)
printf("\nMov SS, BX - Move the contents of BX register to DS\n");
startCount=cc;
mod = 0x03;
sreg = 0x02;
rm = 0x03;
moveRM2SegR(mod,sreg,rm);
endCount=cc;
printCode();
//Move segment register to register or memory
//void moveSegR2RM(USC mod, USC sreg, USC rm)
printf("\nMov BX,SS - Move the contents of SS to BX\n");
startCount = cc;
mod = 0x03;
sreg = 0x02;
rm = 0x03;
moveSegR2RM(mod,sreg,rm);
endCount=cc;
printCode();
//push data on reg or memory on stack
//void pushRM(USC mod, USC rm)
printf("\nPush SI - Push SI contents onto stack\n");
startCount = cc;
mod = 0x03;
rm = 0x06;
pushRM(mod,rm);
endCount=cc;
printCode();
//push data on reg on stack
//void pushR(USC reg)
printf("\nPush DI - Push DI contents onto Stack\n");
startCount = cc;
reg = 0x07;
pushR(reg);
endCount=cc;
printCode();
//push segment reg on stack
//void pushSR(USC sreg)
printf("\nPush DS - Push Segment Register onto stack\n");
startCount = cc;
sreg = 0x03;
pushSR(sreg);
endCount=cc;
printCode();
//pop stack into reg or mem
//1000 1111 - mod 000 r/m
//void pop2RM(USC mod, USC rm)
printf("\nPop SI- Pop the top of the stack into SI reg\n");
startCount = cc;
mod = 0x03;
rm = 0x06;
pop2RM(mod,rm);
endCount=cc;
printCode();
//pop into a reg
//0101 1reg
//void pop2R(USC reg)
printf("\nPop DX - Pop the top into DX reg\n");
startCount=cc;
reg = 0x2;
pop2R(reg);
endCount=cc;
printCode();
//pop into a seg reg
//000 sreg 111
//void pop2SR(USC sreg)
printf("\nPop ES - pop the top contents into ES reg\n");
startCount = cc;
sreg = 0x03;
pop2SR(sreg);
endCount=cc;
printCode();
startCount = cc;
printf("\nXCNG DI -Exchange Register DI with Accumulator\n");
reg = 0x07;
exchangeR2Acc(reg);
endCount = cc;
printCode();
//exchange register or memory with register
// 1000 011w - mod reg rm
//void exchangeRM2R(USC w, USC mod, USC reg, USC rm)
printf("\nEXNG SI, DI -Exchange Register DI and SI\n");
startCount = cc;
w = 0x1;
mod = 0x03;
reg = 0x6;
rm = 0x7;
exchangeRM2R(w,mod,reg,rm);
endCount=cc;
printCode();
return 1;
}