#include <string.h>
#include "asm.h"
#include "tree.h"

#define LabelEq(i, l) \
  (CodeBuf[(i)].label != NUL \
   && strcmp(CodeBuf[(i)].label, (l)) == 0)
#define OpEq(i, o) \
  (CodeBuf[(i)].op != NUL \
   && strcmp(CodeBuf[(i)].op, (o)) == 0)
#define Arg1Eq(i, a) \
  (CodeBuf[(i)].arg1 != NUL \
   && strcmp(CodeBuf[(i)].arg1, (a)) == 0)
#define Arg2Eq(i, a) \
  (CodeBuf[(i)].arg2 != NUL \
   && strcmp(CodeBuf[(i)].arg2, (a)) == 0)

/* stringf.c で定義 */
char *Stringf(char *fmt, ...);	/* 文字列を生成して返す (malloc 使用) */

/* asm.c で定義 */
extern Code CodeBuf[];
extern int CBp;

/* プロトタイプ宣言 */
int chkjmp(int i);    /* CodeBuf[i] が省略可能なjmp命令かどうかの判定 */
int chkaddesp(int i); /* 省略可能な add  esp, ??? 命令かどうかの判定  */

/* コードの最適化(覗き穴最適化) */
void optCode(void) {
  int u, l;	/* u: 処理済コードの末尾，l: 未処理コードの先頭 */
  char *s; int i;
  for(u=l=0; l<CBp;){
    if (OpEq(l, "jmp") && OpEq(l+1, "jmp")) {
      /* jmp  L1              */
      /* jmp  L2  →  jmp  L1 */
      CodeBuf[l+1].arg1 = CodeBuf[l].arg1;	/* L1 */
      l++;
    } else if (chkjmp(l)) {
      /*   jmp  Lk          */
      /* L1:            L1: */
      /*  :              :  */
      /* Ln:        →  Ln: */
      l++;
    } else if ((OpEq(l, "add") || OpEq(l, "sub"))
        && Arg2Eq(l, "0")) {
      /* (add|sub)  R/M, 0  →  除去 */
      l++;
    } else if (OpEq(l, "add") && Arg2Eq(l, "1")) {
      /* add  R/M, 1  →  inc R/M */
      CodeBuf[l].op = "inc"; CodeBuf[l].arg2 = NUL;
    } else if (OpEq(l, "sub") && Arg2Eq(l, "1")) {
      /* sub  R/M, 1  →  dec R/M */
      CodeBuf[l].op = "dec"; CodeBuf[l].arg2 = NUL;
    } else if ((OpEq(l, "imul") || OpEq(l, "mdiv"))
               && Arg2Eq(l, "1")) {
      /* (imul|mdiv)  R/M, 1  →  除去 */
      l++;
    } else if (OpEq(l, "imul") && Arg2Eq(l, "0")) {
      /* imul  R/M, 0  →  mov  R/M, 0 */
      CodeBuf[l].op = "mov";
    } else if (OpEq(l, "mov") && Arg1Eq(l, "%eax")
               && OpEq(l+1, "push") && Arg1Eq(l+1, "%eax")) {
      /* mov   %eax, R/M                */
      /* push  %eax       →  push  R/M */
      CodeBuf[l+1].arg1    = CodeBuf[l].arg2;	/* R/M */
      CodeBuf[l+1].comment = CodeBuf[l].comment;
      l++;
    } else if (OpEq(l, "lea") && Arg1Eq(l, "%eax")
               && CodeBuf[l].arg2[0] == '_'
               && OpEq(l+1, "push") && Arg1Eq(l+1, "%eax")) {
      /* lea   %eax, LABEL                         */
      /* push  %eax         →  push  offset LABEL */
      CodeBuf[l+1].arg1    = Stringf("offset %s", CodeBuf[l].arg2);
      CodeBuf[l+1].comment = CodeBuf[l].comment;
      l++;
    } else if (OpEq(l, "push") && OpEq(l+2, "pop")
               && CodeBuf[l+1].arg1 != CodeBuf[l+2].arg1
               && CodeBuf[l+1].arg2 != CodeBuf[l+2].arg1) {
      /* push  R/M1                              */
      /* OP    R1, R/M2           mov   R2, R/M1 */
      /* pop   R2(!=R1,R/M2)  →  OP    R1, R/M2 */
      s = CodeBuf[l+2].arg1;			/* R2   */
      CodeBuf[l+2].op      = CodeBuf[l+1].op;	/* OP   */
      CodeBuf[l+2].arg1    = CodeBuf[l+1].arg1;	/* R1   */
      CodeBuf[l+2].arg2    = CodeBuf[l+1].arg2;	/* R/M2 */
      CodeBuf[l+2].comment = CodeBuf[l+1].comment;
      CodeBuf[l+1].op      = "mov";
      CodeBuf[l+1].arg1    = s;			/* R2   */
      CodeBuf[l+1].arg2    = CodeBuf[l].arg1;	/* R/M1 */
      CodeBuf[l+1].comment = CodeBuf[l].comment;
      l++;
    } else if (OpEq(l, "mov") && Arg1Eq(l, "%ebx")
               && strstr(CodeBuf[l].arg2, "%eax")==NULL
               && OpEq(l+1, "mov") && Arg1Eq(l+1, "%eax")
               && strstr(CodeBuf[l+1].arg2, "%ebx")==NULL
               && !OpEq(l+2, "mdiv")
               && Arg1Eq(l+2, "%eax") && Arg2Eq(l+2, "%ebx")) {
      /* mov         %ebx, R/M1(!⊃%eax)                      */
      /* mov         %eax, R/M2(!⊃%ebx)      mov  %eax, R/M2 */
      /* OP(!=mdiv)  %eax, %ebx           →  OP   %eax, R/M1 */
      CodeBuf[l+2].arg2    = CodeBuf[l].arg2;	/* R/M1 */
      CodeBuf[l+2].comment = CodeBuf[l].comment;
      l++;
    } else if (OpEq(l, "mov") && Arg1Eq(l, "%eax") && Arg2Eq(l, "0")
               && OpEq(l+1, "mov") && Arg1Eq(l+1, "%eax")
               && strstr(CodeBuf[l+1].arg2, "[%ebp+%eax*4")) {
      /* mov  %eax, 0                                         */
      /* mov  %eax, [%ebp+%eax*4-??]  →  mov  %eax, [%ebp-??]*/
      s = CodeBuf[l+1].arg2;
      for (i=12; s[i-1] ;i++) s[i-7]=s[i];
      l++;
    } else if (chkaddesp(l)) {
      /*       add  %esp, ??                        */
      /*       jmp  _???_r    →        jmp  _???_r */

      /*       add  %esp, ??                        */
      /* L1:                      L1:               */
      /*  :                        :                */
      /* _???_r:              →  _???_r:           */
      l++;
    } else {
      CodeBuf[u].label   = CodeBuf[l].label;
      CodeBuf[u].op      = CodeBuf[l].op;
      CodeBuf[u].arg1    = CodeBuf[l].arg1;
      CodeBuf[u].arg2    = CodeBuf[l].arg2;
      CodeBuf[u].comment = CodeBuf[l].comment;
      u++; l++;
    }
  }
  CBp = u;
}

/* CodeBuf[i] が省略可能なjmp命令かどうかを判定する関数 */
int chkjmp(int i) {
  int k;
  if (!OpEq(i, "jmp")) return 0;
  for (k=i+1; CodeBuf[k].label; k++) {
    if (LabelEq(k, CodeBuf[i].arg1)) return -1;
  }
  return 0;
}

/* CodeBuf[i] が省略可能な add  esp, ??? 命令かどうかの判定  */
int chkaddesp(int i) {
  int k;
  if (!OpEq(i, "add") || !Arg1Eq(i, "%esp")) return 0;
  if (OpEq(i+1, "jmp") && strstr(CodeBuf[i].arg1, "_r")) return -1;
  for (k=i+1; CodeBuf[k].label; k++) {
    if (strstr(CodeBuf[k].label, "_r")) return -1;
  }
  return 0;
}