RTEMS Available -- PowerPC/virtex feedback

Robert S. Grimes rsg at alum.mit.edu
Tue Aug 14 09:03:33 CDT 2007

Chris and Greg, you seem to be right - see below.
gregory.menke at gsfc.nasa.gov wrote:
> I ended up using the newlib printf suite as the test- if fp registers
> are shown in the instructions, then it meant I had a build problem w/
> newlib.  The assembly is dramatically different when the fp registers
> are excluded.
Don't know what you are talking about ("newlib printf suite"), so I
checked my own code.
> Chris Caudle writes:
>  > Doesn't that imply that the tools for PPC405 should already be using soft
>  > float?
>  > Everyone is scurrying around figuring out how to rebuild tools with soft
>  > float, but it looks like that should be the default already, and so far no
>  > one has presented any code which confirms that the exception was actually
>  > caused by using a floating point register.
>  > 
>  > Shouldn't looking at the instructions to see if that is a feasible
>  > explanation be the first step?
I did this instruction:

    $ powerpc-rtems-objdump -d --architecture=powerpc:403 myprog.exe >

and examined the results.  Now, I'm not 100% sure what I'm looking for,
but I figured the floating point store instructions (e.g.stfd, stfx,
etc.) were good candidates.  In fact, searching for "stf" turned up
nothing.  I also couldn't find any floating point load, nor any of the
operations that I looked for.  So I think, Chris, your comment from your
first email on this is likely closer to the truth:

    "More accurately it is "program exception," which is also triggered
by illegal opcode."

You had followed this up by asking if the tool chain had changed between
head from a month ago and, and the answer is: No.

So I'm a bit stumped right now.  On the one hand I have an application
that works with the older RTEMs, but fails on startup with -
sounds bad for!  On the other hand, its failure sounds a bit
like that of my earlier post regarding "isync, exceptions, et. al" from
last Thursday - similar, but worse.

Any ideas?

Does it seem correct to rule out (at least temporarily) the tool chain
as the culprit?


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