[Libclc-dev] [PATCH 2/2] AMDGPU: Implement accurate double precision sqrt

[Jan Vesely]

On Mon, Jun 1, 2015 at 12:16 PM, Tom Stellard <tom at stellard.net> wrote:

> On Thu, May 21, 2015 at 09:20:18AM -0400, Jan Vesely wrote:
> > On Wed, 2015-05-13 at 03:34 +0000, Tom Stellard wrote:
> > > ---
> > >  amdgcn/lib/SOURCES      |  1 +
> > >  amdgcn/lib/math/sqrt.cl | 59
> +++++++++++++++++++++++++++++++++++++++++++++++++
> >
> > I see you created new folder for amdgcn, is the implementation expected
> > to be different for fp64 enabled EG and NI asics?
> >
>
> No, I can move it into the r600 directory.
>

with that change LGTM


>
> -Tom
>
> > >  2 files changed, 60 insertions(+)
> > >  create mode 100644 amdgcn/lib/SOURCES
> > >  create mode 100644 amdgcn/lib/math/sqrt.cl
> > >
> > > diff --git a/amdgcn/lib/SOURCES b/amdgcn/lib/SOURCES
> > > new file mode 100644
> > > index 0000000..64f874c
> > > --- /dev/null
> > > +++ b/amdgcn/lib/SOURCES
> > > @@ -0,0 +1 @@
> > > +math/sqrt.cl
> > > diff --git a/amdgcn/lib/math/sqrt.cl b/amdgcn/lib/math/sqrt.cl
> > > new file mode 100644
> > > index 0000000..3e5b17c
> > > --- /dev/null
> > > +++ b/amdgcn/lib/math/sqrt.cl
> > > @@ -0,0 +1,59 @@
> > > +/*
> > > + * Copyright (c) 2015 Advanced Micro Devices, Inc.
> > > + *
> > > + * Permission is hereby granted, free of charge, to any person
> obtaining a copy
> > > + * of this software and associated documentation files (the
> "Software"), to deal
> > > + * in the Software without restriction, including without limitation
> the rights
> > > + * to use, copy, modify, merge, publish, distribute, sublicense,
> and/or sell
> > > + * copies of the Software, and to permit persons to whom the Software
> is
> > > + * furnished to do so, subject to the following conditions:
> > > + *
> > > + * The above copyright notice and this permission notice shall be
> included in
> > > + * all copies or substantial portions of the Software.
> > > + *
> > > + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
> EXPRESS OR
> > > + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
> MERCHANTABILITY,
> > > + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
> SHALL THE
> > > + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
> OTHER
> > > + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
> ARISING FROM,
> > > + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
> DEALINGS IN
> > > + * THE SOFTWARE.
> > > + */
> > > +
> > > +#include <clc/clc.h>
> > > +#include "../../../generic/lib/clcmacro.h"
> > > +#include "math/clc_sqrt.h"
> > > +
> > > +_CLC_DEFINE_UNARY_BUILTIN(float, sqrt, __clc_sqrt, float)
> > > +
> > > +#ifdef cl_khr_fp64
> > > +
> > > +#pragma OPENCL EXTENSION cl_khr_fp64 : enable
> > > +
> > > +
> > > +_CLC_OVERLOAD _CLC_DEF double sqrt(double x) {
> > > +
> > > +  uint vcc = x < 0x1p-767;
> > > +  uint exp0 = vcc ? 0x100 : 0;
> > > +  unsigned exp1 = vcc ? 0xffffff80 : 0;
> > > +
> > > +  double v01 = ldexp(x, exp0);
> > > +  double v23 = __builtin_amdgpu_rsq(v01);
> > > +  double v45 = v01 * v23;
> > > +  v23 = v23 * 0.5;
> > > +
> > > +  double v67 = fma(-v23, v45, 0.5);
> > > +  v45 = fma(v45, v67, v45);
> > > +  double v89 = fma(-v45, v45, v01);
> > > +  v23 = fma(v23, v67, v23);
> > > +  v45 = fma(v89, v23, v45);
> > > +  v67 = fma(-v45, v45, v01);
> > > +  v23 = fma(v67, v23, v45);
> > > +
> > > +  v23 = ldexp(v23, exp1);
> > > +  return ((x == __builtin_inf()) || (x == 0.0)) ? v01 : v23;
> > > +}
> > > +
> > > +_CLC_UNARY_VECTORIZE(_CLC_OVERLOAD _CLC_DEF, double, sqrt, double);
> > > +
> > > +#endif
> >
> > --
> > Jan Vesely <jan.vesely at rutgers.edu>
>
>
>
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>
>
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