wot to do with the Maverick Crunch patches?

Joseph S. Myers joseph@codesourcery.com
Tue Apr 1 14:16:00 GMT 2008

On Tue, 1 Apr 2008, Hasjim Williams wrote:

> > That illustrates the sort of thing that needs changing to implement
> > unwind 
> > support for a new coprocessor.  Obviously you need to get the unwind 
> > specification in the official ARM EABI documents first before
> > implementing 
> > it in GCC
> Any idea of who to contact and/or how to get this done?

Contact Richard Earnshaw in the first instance.

> > and binutils will also need to support generating correct 
> > information given .save directives for the coprocessor registers.
> http://files.futaris.org/gcc/binutils-crunch.patch almost covers this,
> but I don't quite follow your binutils patch:
> http://sourceware.org/ml/binutils/2006-08/msg00207.html

Since my patch fixes a bug specific to the iWMMXt unwind support, you 
don't need to follow it; either your binutils patch for your coprocessor 
will be bug-free, or it will have its own bugs you need to debug yourself, 
unrelated to the iWMMXt one I fixed.  Following the current bug-fixed code 
would be more useful as an example than following old buggy code and a 
bug-fix to it.

> Also, can I assume that running the testsuites (binutils, gcc and glibc)
> is the best way to determine what is missing from the current
> MaverickCrunch support?

You would be well-advised to add an unwind test similar to the one I added 
in my GCC patch, to make sure that the Crunch registers are restored 

That only covers call-preserved registers.  Testing call-clobbered 
registers is harder (but normally unwind information won't be generated 
for them, so they matter less); for iWMMXt I tried testing using 
-fcall-saved-wr0 -fcall-saved-wr1 ... but found that 
CONDITIONAL_REGISTER_USAGE overrides -fcall-saved-* for the wr registers 
and there is no prologue/epilogue support for saving/restoring wcgr 
registers.  You may need to temporarily modify GCC to save and restore 
such registers in order to test the unwinding for them.

Joseph S. Myers

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