[Beignet] [PATCH] fix built-in function "length"

[Zhigang Gong]

LGTM, pushed, thanks.

On Mon, Oct 28, 2013 at 09:02:32AM +0800, Homer Hsing wrote:
> if vector is zero, then returns zero.
> if vector is very large, then do a scaling first.
> 
> Signed-off-by: Homer Hsing <homer.xing at intel.com>
> ---
>  backend/src/ocl_stdlib.tmpl.h | 25 ++++++++++++++++++++++---
>  1 file changed, 22 insertions(+), 3 deletions(-)
> 
> diff --git a/backend/src/ocl_stdlib.tmpl.h b/backend/src/ocl_stdlib.tmpl.h
> index e6d7910..a3bf0a0 100644
> --- a/backend/src/ocl_stdlib.tmpl.h
> +++ b/backend/src/ocl_stdlib.tmpl.h
> @@ -1740,9 +1740,28 @@ INLINE_OVERLOADABLE float dot(float4 p0, float4 p1) {
>    return p0.x * p1.x + p0.y * p1.y + p0.z * p1.z + p0.w * p1.w;
>  }
>  INLINE_OVERLOADABLE float length(float x) { return __gen_ocl_fabs(x); }
> -INLINE_OVERLOADABLE float length(float2 x) { return sqrt(dot(x,x)); }
> -INLINE_OVERLOADABLE float length(float3 x) { return sqrt(dot(x,x)); }
> -INLINE_OVERLOADABLE float length(float4 x) { return sqrt(dot(x,x)); }
> +#define BODY \
> +  if(m == 0) \
> +    return 0; \
> +  if(isinf(m)) \
> +    return INFINITY; \
> +  if(m < 1) \
> +    m = 1; \
> +  x /= m; \
> +  return m * sqrt(dot(x,x));
> +INLINE_OVERLOADABLE float length(float2 x) {
> +  float m = max(__gen_ocl_fabs(x.s0), __gen_ocl_fabs(x.s1));
> +  BODY;
> +}
> +INLINE_OVERLOADABLE float length(float3 x) {
> +  float m = max(__gen_ocl_fabs(x.s0), max(__gen_ocl_fabs(x.s1), __gen_ocl_fabs(x.s2)));
> +  BODY;
> +}
> +INLINE_OVERLOADABLE float length(float4 x) {
> +  float m = max(__gen_ocl_fabs(x.s0), max(__gen_ocl_fabs(x.s1), max(__gen_ocl_fabs(x.s2), __gen_ocl_fabs(x.s3))));
> +  BODY;
> +}
> +#undef BODY
>  INLINE_OVERLOADABLE float distance(float x, float y) { return length(x-y); }
>  INLINE_OVERLOADABLE float distance(float2 x, float2 y) { return length(x-y); }
>  INLINE_OVERLOADABLE float distance(float3 x, float3 y) { return length(x-y); }
> -- 
> 1.8.3.2
> 
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