[PATCH] Implements -mfpu=softvfp+variants on ARM driver

[Renato Golin]

On 18 February 2014 12:20, Bernie Ogden <bogden at arm.com> wrote:
> Just thought: what does -mfpu=<fp arch> (i.e. without the 'softvfp+' part)
> mean now? It could mean 'calling convention unspecified' or it could mean
> 'hardfloat'. I think it should mean the latter, to be consistent with the
> armcc/gcc usage, but I _think_ that means changing the default calling
> convention? I don't like changing defaults - does the community (or you)
> have any position on this?

Hi Bernie,

My patch changes nothing on that respect. The default float ABI is
still mandated by the target triple and other flags which have their
own ways of defining the float ABI (and I won't get into the details,
because they're rather confusing).

The only conflict that arises is what Joerg spotted, which is that
some hard-float triples may still want soft-float ABIs. For instance,
setting the triple to arm-linux-gnueabihf will set -float-abi=hard,
and setting -mfpu=softvfp will set +soft-float-abi, which are
contradictory.

I don't have enough knowledge of all the edge cases to infer what's
the intended behaviour in this case, so I just left a warning and
dealt with it as if the user meant -mfpu=none, which is not ideal but
it's the least disruptive.

If the mfpu should take precedence, than we should dig through the
previous float-abi options and remove if it conflicts with sofvfp. If
not, the current behaviour is correct. If last-set-is-correct, than
just adding the soft-float-abi regardless is the correct behaviour.
I'm ok with any of them, as long as this is what people expect. Joerg
mentioned that the kernel folks might want that, I'll check in the
LLVMLinux and Linaro lists for what do they think the behaviour should
be...

cheers,
--renato