[Mesa-dev] [PATCH 11/13] nir: Add lrp lowering for doubles in opt_algebraic

[Jason Ekstrand]

On Tue, Apr 12, 2016 at 1:05 AM, Samuel Iglesias Gonsálvez <
siglesias at igalia.com> wrote:

> Some hardware (i965 on Broadwell generation, for example) does not support
> natively the execution of lrp instruction with double arguments.
>
> Add 'lower_lrp_double' flag to lower this instruction in that case.
>
> Signed-off-by: Samuel Iglesias Gonsálvez <siglesias at igalia.com>
> ---
>  src/compiler/nir/nir.h                | 2 ++
>  src/compiler/nir/nir_opt_algebraic.py | 7 +++++--
>  2 files changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
> index 0d17ce0..0bfc849 100644
> --- a/src/compiler/nir/nir.h
> +++ b/src/compiler/nir/nir.h
> @@ -1582,6 +1582,8 @@ typedef struct nir_shader_compiler_options {
>     bool lower_fdiv;
>     bool lower_ffma;
>     bool lower_flrp;
> +   /** Lowers flrp when it does not supports doubles */
>

"does not support"


> +   bool lower_flrp_double;
>

Maybe rename the first one to lower_flrp32 and call this lower_flrp64?


>     bool lower_fpow;
>     bool lower_fsat;
>     bool lower_fsqrt;
> diff --git a/src/compiler/nir/nir_opt_algebraic.py
> b/src/compiler/nir/nir_opt_algebraic.py
> index ec8929a..f971585 100644
> --- a/src/compiler/nir/nir_opt_algebraic.py
> +++ b/src/compiler/nir/nir_opt_algebraic.py
> @@ -92,11 +92,14 @@ optimizations = [
>     (('~flrp', 0.0, a, b), ('fmul', a, b)),
>     (('~flrp', a, b, ('b2f', c)), ('bcsel', c, b, a),
> 'options->lower_flrp'),
>     (('flrp', a, b, c), ('fadd', ('fmul', c, ('fsub', b, a)), a),
> 'options->lower_flrp'),
> +   (('flrp', a, b, c), ('fadd', ('fmul', c, ('fsub', b, a)), a),
> '!options->lower_flrp && options->lower_flrp_double', 64),
>

With the new mechanism, the first one because 'flrp at 32' and this becomes
'flrp at 64'

Also, I think we can just treat lower_flrp and lower_flrp64 as orthogonal
and require drivers to specify both if they want it.


>     (('ffract', a), ('fsub', a, ('ffloor', a)), 'options->lower_ffract'),
>     (('~fadd', ('fmul', a, ('fadd', 1.0, ('fneg', ('b2f', c)))), ('fmul',
> b, ('b2f', c))), ('bcsel', c, b, a), 'options->lower_flrp'),
> -   (('~fadd', ('fmul', a, ('fadd', 1.0, ('fneg',         c ))), ('fmul',
> b,         c )), ('flrp', a, b, c), '!options->lower_flrp'),
> +   (('~fadd', ('fmul', a, ('fadd', 1.0, ('fneg',         c ))), ('fmul',
> b,         c )), ('flrp', a, b, c), '!options->lower_flrp', 32),
> +   (('~fadd', ('fmul', a, ('fadd', 1.0, ('fneg',         c ))), ('fmul',
> b,         c )), ('flrp', a, b, c), '!options->lower_flrp &&
> !options->lower_flrp_double', 64),
>     (('~fadd', a, ('fmul', ('b2f', c), ('fadd', b, ('fneg', a)))),
> ('bcsel', c, b, a), 'options->lower_flrp'),
> -   (('~fadd', a, ('fmul',         c , ('fadd', b, ('fneg', a)))),
> ('flrp', a, b, c), '!options->lower_flrp'),
> +   (('~fadd', a, ('fmul',         c , ('fadd', b, ('fneg', a)))),
> ('flrp', a, b, c), '!options->lower_flrp', 32),
> +   (('~fadd', a, ('fmul',         c , ('fadd', b, ('fneg', a)))),
> ('flrp', a, b, c), '!options->lower_flrp && !options->lower_flrp_double',
> 64),
>     (('ffma', a, b, c), ('fadd', ('fmul', a, b), c),
> 'options->lower_ffma'),
>     (('~fadd', ('fmul', a, b), c), ('ffma', a, b, c),
> '!options->lower_ffma'),
>     # Comparison simplifications
> --
> 2.5.0
>
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