question about the usage of VFP register on arm

[Matthew Gretton-Dann]

On Thu, Feb 09, 2012 at 11:13:39AM +0000, junfeng dong wrote:
> Hi,
> my arm cross compiler runs into an error like :
> ld: error: a.out uses VFP register arguments, /tmp/ccGm43Jh.o does not
> 
> It seems ld requires all input files and output file has the same
> attribute of Tag_ABI_VFP_args, which is set by gcc in assembler file
> (.eabi_attribute 28, 1).
> but I didn't find the place where gcc cope with it. I wonder is this
> attribute controlled only by "-mfloat-abi"? -mfloat-abi=hard means "
> Tag_ABI_VFP_args=1" while -mfloat-abi=soft/softfp means "
> Tag_ABI_VFP_args=0"?is there any other compile option affect that
> attribute?
> Any comments are welcome.

You are correct -mfloat-abi changes the calling-convention used with
floating-point arguments (amongst other things), and thereby changes the
setting of Tag_ABI_VFP_args.

So you need to ensure that all objects you are linking together use the same
calling-convention.

Thanks,

Matt

-- 
Matthew Gretton-Dann
Principal Engineer, PD Software, ARM Ltd.