[Libclc-dev] [PATCH v2 1/1] rootn: Flush denormals if not supported.

[Jan Vesely via Libclc-dev]

On Tue, 2018-04-24 at 12:31 -0400, Jan Vesely wrote:
> It's OK to either flush to 0 or return denormal result if the device
> does not support denormals. See sec 7.2 and 7.5.3 of OCL specs
> 
> v2: Use 0.0f explicitly intead of relying on GPU to flush it.
> 
> Fixes CTS on carrizo and turks
> Signed-off-by: Jan Vesely <jan.vesely at rutgers.edu>
> ---
> This removes the need for the second patch
>  generic/lib/math/clc_rootn.cl | 11 +----------
>  1 file changed, 1 insertion(+), 10 deletions(-)
> 
> diff --git a/generic/lib/math/clc_rootn.cl b/generic/lib/math/clc_rootn.cl
> index d7ee185..0a2c98d 100644
> --- a/generic/lib/math/clc_rootn.cl
> +++ b/generic/lib/math/clc_rootn.cl
> @@ -170,16 +170,7 @@ _CLC_DEF _CLC_OVERLOAD float __clc_rootn(float x, int ny)
>      tv = USE_TABLE(exp_tbl_ep, j);
>  
>      float expylogx = mad(tv.s0, poly, mad(tv.s1, poly, tv.s1)) + tv.s0;
> -    float sexpylogx;
> -    if (!__clc_fp32_subnormals_supported()) {
> -		int explg = ((as_uint(expylogx) & EXPBITS_SP32 >> 23) - 127);
> -		m = (23-(m + 149)) == 0 ? 1: m;
> -		uint mantissa =  ((as_uint(expylogx) & MANTBITS_SP32)|IMPBIT_SP32) >> (23-(m + 149));
> -		sexpylogx = as_float(mantissa);
> -    } else {
> -		sexpylogx = expylogx * as_float(0x1 << (m + 149));
> -    }
> -
> +    float sexpylogx = __clc_fp32_subnormals_supported() ? expylogx * as_float(0x1 << (m + 149)) : 0.0f;
>  
>      float texpylogx = as_float(as_int(expylogx) + m2);
>      expylogx = m < -125 ? sexpylogx : texpylogx;
ping.
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