[Libclc-dev] [PATCH 1/1] math: Use single precision builtin in sp fdim path

[Jan Vesely via Libclc-dev]

On Sat, 2016-05-14 at 03:49 +0000, Aaron Watry wrote:
> On Fri, May 13, 2016, 7:49 PM Tom Stellard via Libclc-dev <
> libclc-dev at lists.llvm.org> wrote:
> 
> > 
> > On Fri, May 13, 2016 at 08:36:18PM -0400, Jan Vesely via Libclc-dev 
> > wrote:
> > > 
> > > Fixes fdim piglit on Turks
> > > 
> > > Signed-off-by: Jan Vesely <jan.vesely at rutgers.edu>
> > > ---
> > > 
> > > Not sure when llvm started inserting double promotion:
> > > <unknown>:0:0: in function test_1_fdim_float void (float
> > > addrspace(1)*,
> > float addrspace(1)*, float addrspace(1)*): unsupported call to
> > function
> > __extendsfdf2
> > > 
> > > 
> > >  generic/lib/math/fdim.inc | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/generic/lib/math/fdim.inc
> > > b/generic/lib/math/fdim.inc
> > > index a67c76e..0e57513 100644
> > > --- a/generic/lib/math/fdim.inc
> > > +++ b/generic/lib/math/fdim.inc
> > > @@ -25,7 +25,7 @@
> > >  _CLC_OVERLOAD _CLC_DEF __CLC_GENTYPE fdim(__CLC_GENTYPE x,
> > __CLC_GENTYPE y) {
> > > 
> > >      if (__builtin_isnan(x) || __builtin_isnan(y))
> > >          return as_float(QNANBITPATT_SP32);
> > > -    return __builtin_fmax(x - y, 0);
> > > +    return __builtin_fmaxf(x - y, 0);
> > Is there a reason we aren't just calling the OpenCL builtin fmax ?
> > 
> Reason? Or good reason?
> 
> If we change this to either __builtin_fmaxf or fmax (I'd go with
> that),
> should we also make that an explicit 0.0f?

Even with 0, the compiler should pick the correct fmax variant (1
conversion vs. 2 conversions), though I agree that the code would be
nicer.

My reason for sticking with __builtin_fmaxf was that there are no
overloads and it forces conversion to float.
It also provides kind of separation between API and it's
implementation, but I'm not sure we wollow it in libclc.

I'll send v2 using 'fmax(x -y, 0.0f)' if that's the consensus.

Jan

> 
> --Aaron
> 
> 
> > 
> > -Tom
> > 
> > > 
> > >  }
> > >  #define __CLC_FDIM_VEC(width) \
> > >  _CLC_OVERLOAD _CLC_DEF float##width fdim(float##width x,
> > > float##width
> > y) { \
> > > 
> > > --
> > > 2.5.5
> > > 
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> > 
-- 
Jan Vesely <jan.vesely at rutgers.edu>
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