[arm64] Negative immediates and lack of default Neon support

Marc Glisse marc.glisse at inria.fr
Wed Sep 24 18:04:40 UTC 2014

On Wed, 24 Sep 2014, Torbjörn Granlund wrote:

> Marc Glisse <marc.glisse at inria.fr> writes:
>  I get:
>  clang: warning: argument unused during compilation: '-mfpu=neon'
>  for every call to clang, but it works.
> Well, they really do like pointless warnings over in clang land.
> We cannot fix this without desupporting some clang releases, since
> autoconf does not support having feature test results to be controlled
> by warning output.

Can't we compile something that will fail without neon and add -mfpu=neon 
only in that case? Otherwise, the warning is bearable.

>  By the way, for inline asm, the 'w' modifier you showed me is the
>  official way and gcc is going to document that:
>  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63359
> This is a pity, since it makes it inconsistent with other gcc ports, and
> depending on gcc internals is not very clean.  Furthermore, this creates
> an incompatibility trap between gcc and clang (which we just triggered,
> of course).

Actually, contrary to what I said yesterday, clang does support 'w' (I 
still can't imagine what I may have done yesterday to get that wrong).

Marc Glisse

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