关于ARM的基本指令的问题(LDM和STM)

只看该作者 · 2009-7-1 21:01

//////ARM版里发了没人鸟，转到这里来了
LDM 和STM编码时有一个参数P,官方文档里的解释如下:
P==1
indicates that the word addressed by Rn is included in the range of memory locations accessed, lying at the top (U==0) or bottom (U==1) of that range.
P==0
indicates that the word addressed by Rn is excluded from the range of memory locations accessed, and lies one word beyond the top of the range (U==0) or one word below the bottom of the range (U==1).
我理解是P==1时为类似空栈的方式( Rn指的内存单元将会被使用 )
P==0时为类似满栈的方式( Rn指的内存单元将不会被使用 )

可是我又发现当LDMIA时显示P==0 (INCREASE AFTER,类似空栈)
LDMIB时P==1(INCREASE BEFORE,类似满栈)

越看越晕,不知道到底是怎样了,请大家释疑,谢谢

只看该作者 · 2009-7-1 21:36

确认下是不是资料的问题
请看ARM architecture reference manual.pdf，A5-42页：
P==0 indicates that the word addressed by Rn is included in the range of memory locations accessed, lying at the top (U==0) or bottom (U==1) of that range.
P==1 indicates that the word addressed by Rn is excluded from the range of memory locations accessed, and lies one word beyond the top of the range (U==0) or one
word below the bottom of the range (U==1).
正和你给出的资料相反。
LDMIA是满栈，P==0，
LDMIB是空栈，P==1.这个是没有错的。