Re: Specifying VPF instructions for ARM?

[Jeff Gold <jgold at us dot ncipher dot com>]

Richard Earnshaw wrote:
> GCC cannot currently generate VFP instructions, but work is in progress to 
> address this (though not for the next release of the compiler).  It can 
> support VFP-format soft-float code (using the same data layout as the VFP, 
> but without using VFP instructions) but this can only be selected as a 
> build-time option.

This is probably just ignorance on my part.  VFP instructions are what 
the error messages talk about and I had no idea there was a difference 
between that and the floating point issues.

Does "build-time option" mean building binutils and gcc, or the 
application itself?  How does one specify which soft-float format should 
be used?  Is this implied by things like -mcpu=strongarm or can it be 
set independently?

> Sorry, I don't read gcc-help -- too many mails in each day as it is, 
> without adding more.

Fair enough.  I only mentioned that I had posted to gcc-help to 
demonstrate that I didn't just post to this list without reading the 
description of the mailing lists on the web site.

> You don't say which versions of the various tools you are trying to use, 

I am using GCC release 3.3.1 when attempting to build the application, 
which is what generates the error messages I posted.  Other recent 
recent versions of GCC seem to provoke the same problem.  GCC 
2.9-xscale-010827 which I got this from the Intel site for the RedHat 
GNUpro toolkit is what I used to generate the libraries.

Could something related to this have changed in the intervening 
versions?  I'm not able to find anything relevant in the ChangeLog.

> The only solution I can suggest here is to avoid using an xscale-elf 
> toolchain for building applications non-xscale systems (use the arm-elf 
> configuration or maybe the strongarm-elf configuration).

For some rather senseless reasons (that I won't bother describing) the 
tool chain needs to be named xscale-elf-*, but I'll try working around 
this using --target=strongarm-elf along with either links or renaming 
executables.

I'm still a little confused, though.  I know that I pass -mcpu=strongarm 
when building the library object files as well as those for the 
application, yet the error message at link time specifically mention 
these as things that use VFP soft-float code.  Does this mean that the 
way the support code is marked becomes contageous where other static 
libraries are concerned?  Or is there some ar option I should be passing 
to avoid this?

Thanks for the explanation and suggestions.

                                    Jeff