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Re: [Qemu-devel] sparc smul problem

From: Blue Swirl
Subject: Re: [Qemu-devel] sparc smul problem
Date: Mon, 1 Sep 2008 20:20:31 +0300

On 9/1/08, Vince Weaver <address@hidden> wrote:
> Hello!
>  I've been stuck on this all weekend, as I can't find where the actual
> problem is. I might be completely missing it, but I've tried a lot of things
> and can't make it work.
>  On SPARC, the "smul" instruction multiplies two numbers, puts the result in
> the result register but also puts the top 32-bits of the 64-bit result into
> the "Y" register.
>  As the attached code shows, the value of "Y" is wrong.  Somehow after the
> multiply, the top 32 bits of the product rae all zeros.  I've played around
> with the code generated by translate.c, and it looks like the shift and
> other instructions all work properly, but the 64-bit multiply the result is
> somehow being truncated.  But I've looked at the generated code (on x86_64)
> and it looks like it is doing the right thing.
>  So anyway, I'll have to take a look at this again later, but in case anyone
> else wants to look at it in case I am missing anything obvious.

Y loads and stores were not correct, the attached patch fixes the
problem. I'm still running some tests.

Attachment: fix_smul.diff
Description: plain/text

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