[kaffe] MIPS Port Update

[Warwick Hunter]

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Kevin,

The original macro only suffered from one
fault: using a MIPS IV movn instruction.
Do you think that we should abandon the
attempts to use the pocketlinux version
of macro and just fix the original fault?

During my testing I noticed that the
pocketlinux macro only works if you are
very careful which value you use as the
newVal. I used the thread-id which keeps
it happy. If one uses a constant value
it fails.

Warwick
-- 
Warwick Hunter                    Agile TV Corporation
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Message-ID: <001601c22d90$3a721210$10eca8c0@grendel>
From: "Kevin D. Kissell" <kevink@mips.com>
To: "Warwick Hunter" <whunter@agile.tv>, "Dalibor Topic" <robilad@yahoo.com>
Cc: "Kaffe Mailing List" <kaffe@kaffe.org>
References: <20020716142121.95344.qmail@web10004.mail.yahoo.com> <3D3504EC.40708@agile.tv> <00a701c22d79$c4db3bf0$10eca8c0@grendel>
Subject: Re: [kaffe] MIPS Port Update
Date: Wed, 17 Jul 2002 14:48:05 +0200
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> 2) The proposed code does not deal with the fact 
>     that the function is specified to return 1 on
>     success, and zero if no exchange occurred.

I should say, it tries to do it with a C epilog: 

     + (*(addr)) == (newVal) ? 1 : 0;})

But there is no guarantee that the compiler will
have tracked and preserved the value written with 
the store conditional (which, being in an asm block,  
might not even be treated as a "store" by the compiler
if we aren't lucky) so as to avoid re-reading *addr.  
If the location is re-loaded, the comparison is not
necessarily going to provide the right response.
The operation may have succeeded, but some other 
thread may have switched in and changed the value 
yet again in the mean time.

One way or another, we have to base the returned 
status on a comparison with the load-locked value.

[rest of my pedantic rant deleted]

            Kevin K.


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