On 22 August 2013 16:08, Matt Turner <matts...@gmail.com> wrote:
> ---
> src/glsl/builtins/ir/frexp.ir | 25
> +++++++++++++++++++++++++
> src/glsl/builtins/ir/ldexp.ir | 25
> +++++++++++++++++++++++++
> src/glsl/builtins/profiles/ARB_gpu_shader5.glsl | 10 ++++++++++
> 3 files changed, 60 insertions(+)
> create mode 100644 src/glsl/builtins/ir/frexp.ir
> create mode 100644 src/glsl/builtins/ir/ldexp.ir
>
> diff --git a/src/glsl/builtins/ir/frexp.ir b/src/glsl/builtins/ir/frexp.ir
> new file mode 100644
> index 0000000..a514994
> --- /dev/null
> +++ b/src/glsl/builtins/ir/frexp.ir
> @@ -0,0 +1,25 @@
> +((function frexp
> + (signature float
> + (parameters
> + (declare (in) float x)
> + (declare (out) int exp))
> + ((return (expression float frexp (var_ref x) (var_ref exp)))))
>
Having an ir_expression that writes to one of its parameters is going to
break assumptions in a lot of our optimization passes. For example, if
opt_tree_grafting encounters this code:
uniform float u;
void main()
{
int exp;
float f = frexp(u, out exp);
float g = float(exp)/256.0;
float h = float(exp) + 1.0;
gl_FragColor = vec4(f, g, h, g + h);
}
it may try to optimize it to this:
uniform float u;
void main()
{
int exp;
float g = float(exp)/256.0;
float h = float(exp) + 1.0;
gl_FragColor = vec4(frexp(u, out exp), g, h, g + h);
}
I think what we need to do is either:
1. Punt on the frexp_to_arith lowering pass for now, and instead just put
the lowered code right here, or
2. In patch 7, replace ir_binop_frexp with two unary ops, one that computes
the mantissa (return value of frexp()), and one that computes the integer
exponent. Then this code will be effectively:
float frexp(float x, out int exp)
{
exp = ir_unop_frexp_mantissa(x);
return ir_unop_frexp_exponent(x);
}
I'm leaning toward option 1, because I suspect it will generate more
efficient code (option 2 is likely to cause the if test in frexp_to_arith
to be duplicated).
> +
> + (signature vec2
> + (parameters
> + (declare (in) vec2 x)
> + (declare (out) ivec2 exp))
> + ((return (expression vec2 frexp (var_ref x) (var_ref exp)))))
> +
> + (signature vec3
> + (parameters
> + (declare (in) vec3 x)
> + (declare (out) ivec3 exp))
> + ((return (expression vec3 frexp (var_ref x) (var_ref exp)))))
> +
> + (signature vec4
> + (parameters
> + (declare (in) vec4 x)
> + (declare (out) ivec4 exp))
> + ((return (expression vec4 frexp (var_ref x) (var_ref exp)))))
> +))
> diff --git a/src/glsl/builtins/ir/ldexp.ir b/src/glsl/builtins/ir/ldexp.ir
> new file mode 100644
> index 0000000..dd25f5a
> --- /dev/null
> +++ b/src/glsl/builtins/ir/ldexp.ir
> @@ -0,0 +1,25 @@
> +((function ldexp
> + (signature float
> + (parameters
> + (declare (in) float x)
> + (declare (in) int exp))
> + ((return (expression float ldexp (var_ref x) (var_ref exp)))))
>
Note: ldexp is fine as a binop, since both its parameters are inputs.
> +
> + (signature vec2
> + (parameters
> + (declare (in) vec2 x)
> + (declare (in) ivec2 exp))
> + ((return (expression vec2 ldexp (var_ref x) (var_ref exp)))))
> +
> + (signature vec3
> + (parameters
> + (declare (in) vec3 x)
> + (declare (in) ivec3 exp))
> + ((return (expression vec3 ldexp (var_ref x) (var_ref exp)))))
> +
> + (signature vec4
> + (parameters
> + (declare (in) vec4 x)
> + (declare (in) ivec4 exp))
> + ((return (expression vec4 ldexp (var_ref x) (var_ref exp)))))
> +))
> diff --git a/src/glsl/builtins/profiles/ARB_gpu_shader5.glsl
> b/src/glsl/builtins/profiles/ARB_gpu_shader5.glsl
> index 3f76283..36fc0de 100644
> --- a/src/glsl/builtins/profiles/ARB_gpu_shader5.glsl
> +++ b/src/glsl/builtins/profiles/ARB_gpu_shader5.glsl
> @@ -59,3 +59,13 @@ float fma(float a, float b, float c);
> vec2 fma(vec2 a, vec2 b, vec2 c);
> vec3 fma(vec3 a, vec3 b, vec3 c);
> vec4 fma(vec4 a, vec4 b, vec4 c);
> +
> +float frexp(float x, out int exp);
> +vec2 frexp(vec2 x, out ivec2 exp);
> +vec3 frexp(vec3 x, out ivec3 exp);
> +vec4 frexp(vec4 x, out ivec4 exp);
> +
> +float ldexp(float x, int exp);
> +vec2 ldexp(vec2 x, ivec2 exp);
> +vec3 ldexp(vec3 x, ivec3 exp);
> +vec4 ldexp(vec4 x, ivec4 exp);
> --
> 1.8.3.2
>
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