x86.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "y.tab.h"

#define section_text "\
section .text\n\
\n\
    global  _start\n\
\n"

#define section_data "\
section .data\n\
\n\
buf times 64 db 0xA\n\
\n"

#define proc_dump32 "\
dump32:\n\
    mov edi, buf + 7\n\
    mov ebx, 8\n\
\n\
loop8:\n\
    mov eax, esi\n\
    and eax, 0xF\n\
    add eax, '0'\n\
    cmp al, '9'\n\
    jle dump4\n\
    add eax, 7\n\
dump4:\n\
    mov byte [edi], al\n\
    shr esi, 4\n\
    dec edi\n\
    dec ebx\n\
    jnz loop8\n\
\n\
    mov edx, 9     ; arg3 len\n\
    mov ecx, buf   ; arg2 ptr\n\
    mov ebx, 1     ; arg1 stdio\n\
    mov eax, 4     ; sys_write\n\
    int 0X80       ; call kernel\n\
    ret\n\
\n"

#define proc_main "\
_start:\n\
    call function_main\n\
\n\
    mov esi, eax\n\
    call dump32\n\
\n\
    mov ebx, 0     ; exit code\n\
    mov eax, 1     ; sys_exit\n\
    int 0X80       ; call kernel\n\
\n"


#ifndef DATA_SIZE
#define DATA_SIZE 4096
#endif
static char data_buf[DATA_SIZE];

#ifndef CODE_SIZE
#define CODE_SIZE 65536
#endif
static char code_buf[CODE_SIZE];

static char temp_buf[256];

static char * varstack[64];
static int vartop = -1;
static char * argstack[16];
static int argtop = -1;
static char * current_function;

int stack_index(char * name, char * stack[], int top) {
  int i=0;
  while (i<=top) {
    if (!strcmp(stack[i], name))
      return i;
    i++;
  }
  return -1;
}

void gen_int(int value) {
  sprintf(temp_buf,"    push %d\n", value);
  strcat(code_buf, temp_buf);
};

void gen_intvar(char * name) {
  int i = stack_index(name, varstack, vartop);
  if (i >= 0)
    sprintf(temp_buf,"    push dword [ebp-%02d] ; %s\n", 4*(i+1), name);
  else {
    i = stack_index(name, argstack, argtop);
    if (i < 0) {
      yyerror(name);
      exit -1;
    }
    sprintf(temp_buf,"    push dword [ebp+%02d] ; %s\n", 4*(argtop-i+2), name);
  } 
  //free(name);
  strcat(code_buf, temp_buf);
};

void assign_intvar(char * name) {
  int i = stack_index(name, varstack, vartop);
  if (i >= 0)
    sprintf(temp_buf,"    pop dword [ebp-%02d] ; %s\n", 4*(i+1), name);
  else {
    i = stack_index(name, argstack, argtop);
    if (i < 0) {
      yyerror(name);
      exit -1;
    }
    sprintf(temp_buf,"    pop dword [ebp+%02d] ; %s\n", 4*(argtop-i+2), name);
  } 
  //free(name);
  strcat(code_buf, temp_buf);
};

void gen_op32(int op) {
  strcat(code_buf, "    pop ebx\n");
  strcat(code_buf, "    pop eax\n");
  switch (op) {
    case '+':
      strcat(code_buf, "    add eax, ebx\n");
      break;
    case '-':
      strcat(code_buf, "    sub eax, ebx\n");
      break;
    case '*':
      strcat(code_buf, "    imul eax, ebx\n");
      break;
    case '/':
      strcat(code_buf, "    idiv eax, ebx\n");
      break;
  }
  strcat(code_buf, "    push eax\n");
};

void gen_negative() {
  strcat(code_buf, "    pop ebx\n");
  strcat(code_buf, "    mov eax, 0\n");
  strcat(code_buf, "    sub eax, ebx\n");
  strcat(code_buf, "    push eax\n");
};

void gen_jmp(char * prefix, int jmpto) {
  sprintf(temp_buf, "    jmp  %s%04d\n", prefix, jmpto);
  strcat(code_buf, temp_buf);
};
  
void gen_jmpcond32(int op, char * prefix, int jmpto) {
  if (op == 0) {
    strcat(code_buf, "    mov ebx, 0\n");
    op = EQ;
  }
  else
    strcat(code_buf, "    pop ebx\n");
  strcat(code_buf, "    pop eax\n");
  strcat(code_buf, "    cmp eax, ebx\n");
  switch (op) {
    case EQ:
      sprintf(temp_buf, "    je  %s%04d\n", prefix, jmpto);
      break;
    case NE:
      sprintf(temp_buf, "    jne %s%04d\n", prefix, jmpto);
      break;
    case LE:
      sprintf(temp_buf, "    jle %s%04d\n", prefix, jmpto);
      break;
    case GE:
      sprintf(temp_buf, "    jge %s%04d\n", prefix, jmpto);
      break;
    case '<':
      sprintf(temp_buf, "    jl  %s%04d\n", prefix, jmpto);
      break;
    case '>':
      sprintf(temp_buf, "    jg  %s%04d\n", prefix, jmpto);
      break;
  }
  strcat(code_buf, temp_buf);
};

void gen_return() {
  strcat(code_buf, "    pop  eax\n");
  sprintf(temp_buf, "    jmp function_%s_end\n", current_function);
  strcat(code_buf, temp_buf);
}

void gen_label(char * prefix, int jmpto) {
  sprintf(temp_buf, "%s%04d:\n", prefix, jmpto);
  strcat(code_buf, temp_buf);
}

void declare_intvar(char * name) {
  sprintf(temp_buf,"    push 0xffffffff ; %s\n", name);
  strcat(code_buf, temp_buf);
  varstack[++vartop] = name;
};

void declare_intarg(char * name) {
  argstack[++argtop] = name;
}

void begin_func(char * name) {
  current_function = name;
  sprintf(temp_buf,"function_%s:\n", name);
  strcat(code_buf, temp_buf);
  strcat(code_buf, "    push ebp\n");
  strcat(code_buf, "    mov  ebp, esp\n");
//strcat(code_buf, "    push ebx\n");
//strcat(code_buf, "    push edi\n");
//strcat(code_buf, "    push esi\n");
}

void end_func() {
  int i;
  sprintf(temp_buf,"function_%s_end:\n", current_function);
/*
  free(current_function);
  for (i=0; i<vartop; i++)
    free(varstack[i]);
  for (i=0; i<argtop; i++)
    free(argstack[i]);
*/
  strcat(code_buf, temp_buf);
//strcat(code_buf, "    pop  esi\n");
//strcat(code_buf, "    pop  edi\n");
//strcat(code_buf, "    pop  ebx\n");
  strcat(code_buf, "    mov  esp, ebp\n");
  strcat(code_buf, "    pop  ebp\n");
  strcat(code_buf, "    ret\n");
}

void gen_call(char * name, int nargs) {
  sprintf(temp_buf, "    call function_%s\n", name);
  strcat(code_buf, temp_buf);
  if (nargs) {
    sprintf(temp_buf, "    add esp, %d ; drop %d args\n", nargs * 4, nargs);
    strcat(code_buf, temp_buf);
  }
}

void gen_callresult() {
  strcat(code_buf, "    push eax\n");
}

int main()
{
  strcpy(data_buf, section_text);
  strcat(data_buf, section_data);
  strcpy(code_buf, proc_dump32);
  strcat(code_buf, proc_main);
  if (yyparse())
    return 1;
  printf("%s\n",data_buf);
  printf("%s\n",code_buf);
  return 0;
}