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Date: Thu, 2 Feb 2017 10:02:16 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Joe Perches <joe@perches.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Laura Abbott <labbott@redhat.com>, Will Deacon <will.deacon@arm.com>,
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Subject: Re: Build failure with v4.9-rc1 and GCC trunk -- compiler weirdness
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On Wed, Feb 01, 2017 at 11:04:54AM -0800, Joe Perches wrote:
> > +#define order_base_2(n)                                \
> > +(                                              \
> > +       __builtin_constant_p(n) ? (             \
> > +               ((n) < 2) ? (n) :               \
> > +               ilog2((n) - 1) + 1) :           \
> > +       __order_base_2(n)                       \
> > + )
> 
> Does this work properly when n is a signed negative value?

Do you see it returning a complex number?