问题描述
关于LDP和LDP的文档STP 给出了一个示例指令，最后带有感叹号:
The documentation for LDP and STP gives an example instruction with an exclamation mark in the end:
LDP X8, X2, [X0, #0x10]!
有关移植的文档A64中的A32 PUSH/POP 指令给出了以下示例:
Also the documentation about porting A32 PUSH/POP instructions into A64 gives the following examples:
PUSH {r0-r1} ---> STP X0, X1, [SP, #-16]!
POP {r0-r1} ---> LDP X0, X1, [SP], #16
这两个页面均未解释说明末尾的感叹号的含义.是什么?
Neither of the pages explains what the exclamation mark in the end of the instructions means. What does it?
推荐答案
!表示寄存器回写":基址寄存器用于计算传输地址，而已更新.
The ! means "Register write-back": the base register is used to calculate the address of the transfer, and is updated.
在您的示例中:
LDP X8, X2, [X0, #0x10]!
X0进行了修改，以便在操作之后:
X0 modified so that after the operation:
X0 = X0 + 0x10
如果不放置!，则操作不会修改X0.
If you do not put the !, X0 is not modified by the operation.
在有关PUSH/POP的第二个示例中，不同之处在于完成增量的时间:
On the second example concerning PUSH/POP, the difference is when the increment is done:
STP X0, X1, [SP, #-16]!存储在地址SP-16中，并且SP以相同的方式递减
STP X0, X1, [SP, #-16]! stores at address SP-16, and SP is decremented in the same way
LDP X0, X1, [SP], #16从地址SP加载，执行传输后，将SP+16存储到SP.
LDP X0, X1, [SP], #16 loads from address SP, and after the transfer is performed, stores SP+16 to SP.
这篇关于在A64指令的结尾，感叹号是什么意思?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！