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

Thomas Preudhomme robotux@celest.fr
Tue Mar 4 07:02:00 GMT 2014


[Please CC me as I'm not subscribed to this list]

Hi there,

I'm currently working on adding a switch to check whether public 
function involve float parameters or return values. Such a check would 
be useful for people trying to write code that is compatible with both 
base standard (softfloat) and standard variant (hardfloat) ARM calling 
convention. I also intend to set the ELF attribute Tag_ABI_VFP_args to 
value 3 (code compatible with both ABI) so this check would allow to 
make sure such value would be set.

I initially thought about reusing -mfloat-abi with the value none for 
that purpose since it would somehow define a new ABI where no float can 
be used. However, it would then not be possible to forbit float in 
public interface with the use of VFP instructions for float arithmetic 
(softfp) because this switch conflates the float ABI with the use of a 
floating point unit for float arithmetic. Also, gcc passes -mfloat-abi 
down to the assembler and that would mean teaching the assembler about 
-mfloat-abi=none as well.

I thus think that a new switch would be better and am asking for your 
opinion about it as I would like this functionality to incorporate gcc 
codebase.

Best regards,

Thomas Preud'homme



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