[Beignet] [PATCH] GBE: improve builtin exp.

[Zhigang Gong]

LGTM, will push latter. Thanks.

On Mon, Jun 23, 2014 at 10:33:17AM +0800, Ruiling Song wrote:
> Put some variables into register.
> This could improve luxMark sala about 10% under strict conformance.
> 
> Signed-off-by: Ruiling Song <ruiling.song at intel.com>
> ---
>  backend/src/ocl_stdlib.tmpl.h |   22 +++++++++++-----------
>  1 file changed, 11 insertions(+), 11 deletions(-)
> 
> diff --git a/backend/src/ocl_stdlib.tmpl.h b/backend/src/ocl_stdlib.tmpl.h
> index c2eca7c..fc6de25 100755
> --- a/backend/src/ocl_stdlib.tmpl.h
> +++ b/backend/src/ocl_stdlib.tmpl.h
> @@ -2648,16 +2648,15 @@ INLINE_OVERLOADABLE float __gen_ocl_internal_exp(float x) {
>    P3 = 6.6137559770e-05, /* 0x388ab355 */
>    P4 = -1.6533901999e-06, /* 0xb5ddea0e */
>    P5 =	4.1381369442e-08; /* 0x3331bb4c */
> -  float ln2HI[2],ln2LO[2],halF[2];
>    float y,hi=0.0,lo=0.0,c,t;
>    int k=0,xsb;
>    unsigned hx;
> -  ln2HI[0] = 6.9313812256e-01;	/* 0x3f317180 */
> -  ln2HI[1] = -6.9313812256e-01;	/* 0xbf317180 */
> -  ln2LO[0] = 9.0580006145e-06;  	/* 0x3717f7d1 */
> -  ln2LO[1] = -9.0580006145e-06; /* 0xb717f7d1 */
> -  halF[0] = 0.5;
> -  halF[1] =	-0.5;
> +  float ln2HI_0 = 6.9313812256e-01;	/* 0x3f317180 */
> +  float ln2HI_1 = -6.9313812256e-01;	/* 0xbf317180 */
> +  float ln2LO_0 = 9.0580006145e-06;  	/* 0x3717f7d1 */
> +  float ln2LO_1 = -9.0580006145e-06; /* 0xb717f7d1 */
> +  float half_0 = 0.5;
> +  float half_1 =	-0.5;
>  
>    GEN_OCL_GET_FLOAT_WORD(hx,x);
>    xsb = (hx>>31)&1;		/* sign bit of x */
> @@ -2675,12 +2674,13 @@ INLINE_OVERLOADABLE float __gen_ocl_internal_exp(float x) {
>    /* argument reduction */
>    if(hx > 0x3eb17218) {		/* if  |x| > 0.5 ln2 */
>      if(hx < 0x3F851592) {	/* and |x| < 1.5 ln2 */
> -      hi = x-ln2HI[xsb]; lo=ln2LO[xsb]; k = 1-xsb-xsb;
> +      hi = x-(xsb ==1 ? ln2HI_1 : ln2HI_0); lo= xsb == 1? ln2LO_1 : ln2LO_0; k = 1-xsb-xsb;
>      } else {
> -      k  = ivln2*x+halF[xsb];
> +      float tmp = xsb == 1 ? half_1 : half_0;
> +      k  = ivln2*x+tmp;
>        t  = k;
> -      hi = x - t*ln2HI[0];	/* t*ln2HI is exact here */
> -      lo = t*ln2LO[0];
> +      hi = x - t*ln2HI_0;	/* t*ln2HI is exact here */
> +      lo = t*ln2LO_0;
>      }
>      x  = hi - lo;
>    }
> -- 
> 1.7.10.4
> 
> _______________________________________________
> Beignet mailing list
> Beignet at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/beignet