局部变量分配到寄存器的问题

只看该作者 · 2010-11-16 13:02

论坛里面看到了个函数，拷贝下来编译了下：
原函数：
#define uint8 unsigned char
#define uint unsigned int

void  Adjust(uint val)
{
  uint8  temp1,temp2,temp3,temp4,temp5;
      while(val>=10000)
      {
            val =val- 10000;
            temp1++;
      }

      while(val>=1000)
      {
            val =val-1000;
            temp2++;
      }

      while(val>=100)
      {
            val -= 100;
            temp3++;
      }

      while(val>=10)
      {
            val =val- 10;
            temp4++;
      }

      temp5 = val;
}

void main()
{
while(1)
  {
   Adjust(65500)；

}
}

编译后发现RAM占了14个字节，寄存器只用了R6,R7，然后5个局部变量用了5个固定地址RAM字节，请教下各位怎么让那些局部变量在寄存器还有的用的情况下分配到寄存器中去呢？

汇编代码如下：

         ; FUNCTION _Adjust (BEGIN)
                                       ; SOURCE LINE # 45
;---- Variable 'val' assigned to Register 'R6/R7' ----
                                       ; SOURCE LINE # 46
0000       ?C0001:
                                       ; SOURCE LINE # 48
0000 C3             CLR    C
0001 EF             MOV    A,R7
0002 9410             SUBB A,#010H
0004 EE             MOV    A,R6
0005 9427             SUBB A,#027H
0007 400C             JC    ?C0003
                                       ; SOURCE LINE # 49
                                       ; SOURCE LINE # 50
0009 74F0             MOV    A,#0F0H
000B 2F             ADD    A,R7
000C FF             MOV    R7,A
000D 74D8             MOV    A,#0D8H
000F 3E             ADDC A,R6
0010 FE             MOV    R6,A
                                       ; SOURCE LINE # 51
0011 0500       R    INC    temp1
                                       ; SOURCE LINE # 52
0013 80EB             SJMP ?C0001
0015       ?C0003:
                                       ; SOURCE LINE # 54
0015 C3             CLR    C
0016 EF             MOV    A,R7
0017 94E8             SUBB A,#0E8H
0019 EE             MOV    A,R6
001A 9403             SUBB A,#03H
001C 400C             JC    ?C0005
                                       ; SOURCE LINE # 55
                                       ; SOURCE LINE # 56
001E 7418             MOV    A,#018H
0020 2F             ADD    A,R7
0021 FF             MOV    R7,A
0022 74FC             MOV    A,#0FCH
0024 3E             ADDC A,R6
0025 FE             MOV    R6,A
                                       ; SOURCE LINE # 57
0026 0500       R    INC    temp2
                                       ; SOURCE LINE # 58
0028 80EB             SJMP ?C0003
002A       ?C0005:
                                       ; SOURCE LINE # 60
002A C3             CLR    C
002B EF             MOV    A,R7
002C 9464             SUBB A,#064H
002E EE             MOV    A,R6
002F 9400             SUBB A,#00H
0031 400C             JC    ?C0007
                                       ; SOURCE LINE # 61
                                       ; SOURCE LINE # 62
0033 749C             MOV    A,#09CH
0035 2F             ADD    A,R7
0036 FF             MOV    R7,A
0037 74FF             MOV    A,#0FFH
0039 3E             ADDC A,R6
C51 COMPILER V9.00 GLOB                                                                11/16/2010 13:00:55 PAGE 4
003A FE             MOV    R6,A
                                       ; SOURCE LINE # 63
003B 0500       R    INC    temp3
                                       ; SOURCE LINE # 64
003D 80EB             SJMP ?C0005
003F       ?C0007:
                                       ; SOURCE LINE # 66
003F C3             CLR    C
0040 EF             MOV    A,R7
0041 940A             SUBB A,#0AH
0043 EE             MOV    A,R6
0044 9400             SUBB A,#00H
0046 400C             JC    ?C0008
                                       ; SOURCE LINE # 67
                                       ; SOURCE LINE # 68
0048 74F6             MOV    A,#0F6H
004A 2F             ADD    A,R7
004B FF             MOV    R7,A
004C 74FF             MOV    A,#0FFH
004E 3E             ADDC A,R6
004F FE             MOV    R6,A
                                       ; SOURCE LINE # 69
0050 0500       R    INC    temp4
                                       ; SOURCE LINE # 70
0052 80EB             SJMP ?C0007
0054       ?C0008:
                                       ; SOURCE LINE # 72
0054 8F00       R    MOV    temp5,R7
                                       ; SOURCE LINE # 73
0056 22             RET
         ; FUNCTION _Adjust (END)

         ; FUNCTION main (BEGIN)
                                       ; SOURCE LINE # 85
                                       ; SOURCE LINE # 86
0000       ?C0010:
                                       ; SOURCE LINE # 88
                                       ; SOURCE LINE # 89
                                       ; SOURCE LINE # 90
0000 7FDC             MOV    R7,#0DCH
0002 7EFF             MOV    R6,#0FFH
0004 120000    R    LCALL _Adjust
                                       ; SOURCE LINE # 92
0007 80F7             SJMP ?C0010
         ; FUNCTION main (END)