On Thu, 2016-03-03 at 01:30 -0800, Kenneth Graunke wrote:
> From: Francisco Jerez <curroje...@riseup.net>
>
> The adjusted polynomial coefficients come from the numerical
> minimization of the L2 norm of the relative error. The old
> coefficients would give a maximum relative error of about 15000 ULP in
> the neighborhood around acos(x) = 0, the new ones give a relative
> error bounded by less than 2000 ULP in the same neighborhood.
>
> Fixes four dEQP subtests:
> dEQP-GLES31.functional.shaders.builtin_functions.precision.acos.
> highp_compute.{scalar,vec2,vec3,vec4}
Cool! I thought we would have to use higher order polynomials. Series
is:
Reviewed-by: Iago Toral Quiroga <ito...@igalia.com>
What about asin? It looks like the new coefficients should be useful
there as well.
> ---
> src/compiler/glsl/builtin_functions.cpp | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> Curro originally wrote this code for the SPIR-V front-end when working
> on Vulkan conformance. I copy and pasted it over to GLSL, but all of
> the actual work is Curro's.
>
> diff --git a/src/compiler/glsl/builtin_functions.cpp
> b/src/compiler/glsl/builtin_functions.cpp
> index 0d289c1..10fb21b 100644
> --- a/src/compiler/glsl/builtin_functions.cpp
> +++ b/src/compiler/glsl/builtin_functions.cpp
> @@ -3262,7 +3262,7 @@ builtin_builder::_acos(const glsl_type *type)
> ir_variable *x = in_var(type, "x");
> MAKE_SIG(type, always_available, 1, x);
>
> - body.emit(ret(sub(imm(M_PI_2f), asin_expr(x, 0.086566724f,
> -0.03102955f))));
> + body.emit(ret(sub(imm(M_PI_2f), asin_expr(x, 0.08132463f,
> -0.02363318f))));
>
> return sig;
> }
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