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[lupino3]

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[shuckleFan]

Hi I'm a student that I have just started to use edumips64. I read the documentation, the part about system call, I don't get why regsiter R1 and register R14 are used for return value and parameter, respectively, instead of more conventional register.
In particular register R1, isn't it reserved for assembler?
I hope this question is not too naive.

[lupino3]

Hi @shuckleFan and thanks for your question, which is definitely not naive :)

So, I did implement the SYSCALL instruction 17 years ago, but I do not remember at all why I chose those particular registers. As I look to online docs now, I think you are right and I should have used r1 ($at) for the return value.

I suspect it wouldn't be a good idea to change behavior now, so I'll leave things as they are. I'll dig a bit further in my docs to see if I can find a reason for this choice :)

Thanks,
Andrea

[shuckleFan]

I should have used r1 ($at) for the return value
Is that a typo?
You meant "should NOT" right? 🤔

by the way thank you for aswering me. i appreciate it a lot

[lupino3]

Yes, I meant should not have used r1 :) apologies.
$v0 ($r2) seems more appropriate.