stm8 iar中，为什么进入中断后要额外操作A寄存器

只看该作者 · 2012-1-9 16:37

mian.c中有一个函数
u32 add(u32 x,u32 y)
{
  return x+x+y+y+x;

}

中断函数是
INTERRUPT_HANDLER(EXTI_PORTC_IRQHandler, 5)
{
u32 ii= add(323,424);}

查看这个代码的汇编文件，进入后，竟然对A寄存器额外操作

132       INTERRUPT_HANDLER(EXTI_PORTC_IRQHandler, 5)
133       {
\                   EXTI_PORTC_IRQHandler:
\                   _interrupt_7:
\ 000000 8A                   PUSH    CC
\ 000001 84                   POP    A
\ 000002 A4BF                AND    A, #0xbf
\ 000004 88                   PUSH    A
\ 000005 86                   POP    CC
\ 000006 8D000000             CALLF    L:?push_l0
\ 00000A 8D000000             CALLF    L:?push_l1
134          /* In order to detect unexpected events during development,
135             it is recommended to set a breakpoint on the following instruction.
136
137
138          */
139          u32 ii= add(323,424);
\ 00000E AE01A8             LDW    X, #0x1a8
\ 000011 BF00                LDW    S:?w3, X
\ 000013 5F                   CLRW    X
\ 000014 BF00                LDW    S:?w2, X
\ 000016 AE0143             LDW    X, #0x143
\ 000019 BF00                LDW    S:?w1, X
\ 00001B 5F                   CLRW    X
\ 00001C BF00                LDW    S:?w0, X
\ 00001E 8D000000             CALLF    add
140
141       }
\ 000022 8D000000             CALLF    L:?pop_l1
\ 000026 8D000000             CALLF    L:?pop_l0
\ 00002A 80                   IRET