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From: Florian K. <br...@ac...> - 2012-02-23 14:53:45
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On 02/23/2012 03:28 AM, Julian Seward wrote:
> So .. apart from the curiosity value, I am not sure what this will buy
> you in the general case. Maybe you are doing some bizarre experiment
> with your handwritten assembly version of _start?
>
Yeah...to satisfy your curiosity here's the story.
Long time ago when I did the 128-bit floating point implementation for
s390 I wrote some testing machinery that made sure memcheck propagated
the undefinedness through the new IROps properly. Basically
- load an undefined value into a register
- AND it with a one-hot bit-pattern (leaving a single bit undefined)
- perform the operation we're interested in
- do a conditional branch on the result
- depending on the operation the conditional branch would test
a specific bit or all of them
- check for reported error
I'm trying to revive that machinery because I think it's useful to have,
in particular for testing upcoming dfp support.
So what I'm doing is to generate the smallest possible asm snippets that
implement what I described above.
I ran into trouble with step #1 :)
Cheers,
Florian
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