[Beignet] [PATCH] GBE: Fix builtin tanpi.

[Zhigang Gong]

LGTM, pushed to both master branch and Release_v0.9.x branch.
Thanks.

On Mon, Jul 07, 2014 at 01:59:24PM +0800, Ruiling Song wrote:
> To meet precision requirement of OCL Spec .
> 
> Signed-off-by: Ruiling Song <ruiling.song at intel.com>
> ---
>  backend/src/ocl_stdlib.tmpl.h |   28 +++++++++++++++++++++++++++-
>  1 file changed, 27 insertions(+), 1 deletion(-)
> 
> diff --git a/backend/src/ocl_stdlib.tmpl.h b/backend/src/ocl_stdlib.tmpl.h
> index 42f5e85..01bcbef 100755
> --- a/backend/src/ocl_stdlib.tmpl.h
> +++ b/backend/src/ocl_stdlib.tmpl.h
> @@ -2264,7 +2264,33 @@ INLINE_OVERLOADABLE float native_tan(float x) {
>    return native_sin(x) / native_cos(x);
>  }
>  INLINE_OVERLOADABLE float __gen_ocl_internal_tanpi(float x) {
> -  return native_tan(x * M_PI_F);
> +  float sign = 1.0f;
> +  int ix;
> +  if(isinf(x)) return NAN;
> +  if(x < 0.0f) { x = -x; sign = -1.0f; }
> +  GEN_OCL_GET_FLOAT_WORD(ix, x);
> +  if(x> 0x1.0p24) return 0.0f;
> +  float m = __gen_ocl_internal_floor(x);
> +  ix = (int)m;
> +  m = x-m;
> +  int n = __gen_ocl_internal_floor(m*4.0f);
> +  if(m == 0.5f) {
> +    return (ix&0x1) == 0 ? sign*INFINITY : sign*-INFINITY;
> +  }
> +  if(m == 0.0f) {
> +    return (ix&0x1) == 0 ? 0.0f : -0.0f;
> +  }
> +
> +  switch(n) {
> +    case 0:
> +      return sign * __kernel_tanf(m*M_PI_F, 0.0f, 1);
> +    case 1:
> +      return sign * 1.0f/__kernel_tanf((0.5f-m)*M_PI_F, 0.0f, 1);
> +    case 2:
> +      return sign * 1.0f/__kernel_tanf((0.5f-m)*M_PI_F, 0.0f, 1);
> +    default:
> +      return sign * -1.0f*__kernel_tanf((1.0f-m)*M_PI_F, 0.0f, 1);
> +  }
>  }
>  INLINE_OVERLOADABLE float native_exp2(float x) { return __gen_ocl_exp(x); }
>  INLINE_OVERLOADABLE float native_exp(float x) { return __gen_ocl_exp(M_LOG2E_F*x); }
> -- 
> 1.7.10.4
> 
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