[RFC][ARM] Naming for new switch to check for mixed hardfloat/softfloat compat

[Joseph S. Myers]

On Wed, 5 Mar 2014, Thomas Preud'homme wrote:

> > Some libgcc functions on ARM have ABIs that depend on which AAPCS 
> > variant is in use - that is, libcalls, not just explicitly defined or 
> > called functions, can affect the ABI compatibility.  But the RTABI 
> > functions don't - if you allow for that, then you increase the number 
> > of cases that end up compatible with both ABI variants.
> 
> Do you have some example of such libgcc functions? Is there any of them 
> with no link to the use of float in public interface? Without knowing 
> any such case from the top of my head I would say that the use of any of 
> these functions make the compilation unit not compatible with both 
> calling conventions since it requires libgcc for a specific calling 
> convention but maybe the runtime library can be treated differently than 
> other libraries.

The functions affected use floating-point in their public interfaces - for 
example, __muldc3.  Note that libcalls have a different hook 
(TARGET_LIBCALL_VALUE, ending up using arm_libcall_uses_aapcs_base) from 
the ones you mentioned.  But if you use only functions that pass 
arm_libcall_uses_aapcs_base (i.e. the floating-point operations defined in 
RTABI) or don't involve floating point, then you can be compatible with 
both calling conventions.

-- 
Joseph S. Myers
joseph@codesourcery.com