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Re: [PATCH] Fix thumb calls via PLT on ARM/SymbianOS


On Wed, 2005-03-16 at 17:33, Ian Lance Taylor wrote:
> Richard Earnshaw <rearnsha@gcc.gnu.org> writes:
> 
> > On Wed, 2005-03-16 at 16:39, Ian Lance Taylor wrote:
> > 
> > > OUTPUT_ARCH lets you specify an architecture.  For ARM, this will be
> > > one of the entries found in arch_info_struct in bfd/cpu-arm.c.  Of
> > > course that list can be adjusted.
> > > 
> > 
> > The current attributes proposal for the ABI lists 27 separate
> > attributes, giving rise to a theoretical 10^14 possible variants.  In
> > practice the number of realistic variants is much smaller than this, but
> > it's still much larger than can be listed explicitly in an arch_info
> > struct.
> 
> I guess I misunderstood the issue.  I didn't realize that it was
> necessary to support a set of different attributes.  I guess I don't
> understand why -march was brought up---march in gcc doesn't take a set
> of attributes.
> 

-march was brought up because *in this particular case* it's the
attribute that we are interested in: does the target architecture have
the blx instruction?  So it's true that *in this particular case* we
could solve the problem in the info_arch vector: but we can't solve the
general problem that way -- it requires more a complex solution.

> Of course a set of attributes could be done in BFD by using the
> machine number as a bitfield, but that is probably not the way to go.

You'd need something like 68 bits to fully describe the 27 attributes.

R.


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