assembly - MIPS float : swc1 vs. s.s

Question

我正在做一些涉及 MIPS 的工作汇编，我不断遇到这四个浮点加载/存储伪指令:l.s , l.d , s.s , s.d .我在网上找到了一些文档，发现有四个“实际”指令似乎在做同样的事情:lwc1 , ldc1 , swc1 , 和 sdc1 .

我唯一的问题是，有什么区别？据我所知，这两组指令做的事情完全一样。是否存在伪代码只是因为它们更容易阅读？

提前感谢您的任何见解。

Answer 1

My only question is, what's the difference? As far as I can tell, both sets of instructions do exactly the same thing.

你是对的。唯一可能出现的区别是当一个伪指令被翻译成多个“真实”指令时。

Do the pseudos maybe exist just because they're easier to read?

再次，是的。那是 为什么他们存在。它们给人一种更具表现力的指令集的错觉。报价 Computer organization and design / Patterson & Hennessy :

... the assembler can also treat common variations of machine language instructions as if they were instructions in their own right. The hardware need not implement these instructions; however, their appearance in aassembly language simplifies translation and programming. ...

鉴于您的示例，更“清楚”地说:

l.s $f2, 24(t1)       # Load Single contained in 24(t1) to $f2

比

lwc1 $f2, 24(t1)      # Load Word into Coprocessor 1 from 24(t1) to $f2

以及你可以更好地理解:

move $7, $18        # move contents of $18 to $7

比

add $7, $18, $0

对我来说，只有借助助记符才能获得更清晰易读的代码。