Re: [Mesa-dev] [PATCH 2/3] nir: Add a discard optimization pass
On Wed, Jul 4, 2018 at 2:22 AM, Grazvydas Ignotas wrote:
> On Wed, Jul 4, 2018 at 9:13 AM, Jason Ekstrand
> wrote:
> > Many fragment shaders do a discard using relatively little information
> > but still put the discard fairly far down in the shader for no good
> > reason. If the discard is moved higher up, we can possibly avoid doing
> > some or almost all of the work in the shader. When this lets us skip
> > texturing operations, it's an especially high win.
> >
> > One of the biggest offenders here is DXVK. The D3D APIs have different
> > rules for discards than OpenGL and Vulkan. One effective way (which is
> > what DXVK uses) to implement DX behavior on top of GL or Vulkan is to
> > wait until the very end of the shader to discard. This ends up in the
> > pessimal case where we always do all of the work before discarding.
> > This pass helps some DXVK shaders significantly.
> > ---
> > src/compiler/Makefile.sources | 1 +
> > src/compiler/nir/meson.build | 1 +
> > src/compiler/nir/nir.h | 10 +
> > src/compiler/nir/nir_opt_discard.c | 404 +
> > 4 files changed, 416 insertions(+)
> > create mode 100644 src/compiler/nir/nir_opt_discard.c
> >
> > diff --git a/src/compiler/Makefile.sources b/src/compiler/Makefile.
> sources
> > index 9e3fbdc2612..8600ce81281 100644
> > --- a/src/compiler/Makefile.sources
> > +++ b/src/compiler/Makefile.sources
> > @@ -271,6 +271,7 @@ NIR_FILES = \
> > nir/nir_opt_cse.c \
> > nir/nir_opt_dce.c \
> > nir/nir_opt_dead_cf.c \
> > + nir/nir_opt_discard.c \
> > nir/nir_opt_gcm.c \
> > nir/nir_opt_global_to_local.c \
> > nir/nir_opt_if.c \
> > diff --git a/src/compiler/nir/meson.build b/src/compiler/nir/meson.build
> > index 28aa8de7014..e339258bb94 100644
> > --- a/src/compiler/nir/meson.build
> > +++ b/src/compiler/nir/meson.build
> > @@ -156,6 +156,7 @@ files_libnir = files(
> >'nir_opt_cse.c',
> >'nir_opt_dce.c',
> >'nir_opt_dead_cf.c',
> > + 'nir_opt_discard.c',
> >'nir_opt_gcm.c',
> >'nir_opt_global_to_local.c',
> >'nir_opt_if.c',
> > diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
> > index 92ab3a699cc..44006dac160 100644
> > --- a/src/compiler/nir/nir.h
> > +++ b/src/compiler/nir/nir.h
> > @@ -2022,6 +2022,13 @@ typedef struct nir_shader_compiler_options {
> > */
> > bool vs_inputs_dual_locations;
> >
> > + /**
> > +* Whether or not derivatives are still a safe operation after a
> discard
> > +* has occurred. Optimization passes may be able to be a bit more
> > +* agressive if this is true.
> > +*/
> > + bool derivatives_safe_after_discard;
> > +
> > unsigned max_unroll_iterations;
> > } nir_shader_compiler_options;
> >
> > @@ -2899,6 +2906,9 @@ bool nir_opt_dce(nir_shader *shader);
> >
> > bool nir_opt_dead_cf(nir_shader *shader);
> >
> > +bool nir_opt_discard_if(nir_shader *shader);
> > +bool nir_opt_move_discards_to_top(nir_shader *shader);
> > +
> > bool nir_opt_gcm(nir_shader *shader, bool value_number);
> >
> > bool nir_opt_if(nir_shader *shader);
> > diff --git a/src/compiler/nir/nir_opt_discard.c
> b/src/compiler/nir/nir_opt_discard.c
> > new file mode 100644
> > index 000..eb1a8296282
> > --- /dev/null
> > +++ b/src/compiler/nir/nir_opt_discard.c
> > @@ -0,0 +1,404 @@
> > +/*
> > + * Copyright © 2014 Intel Corporation
>
> 2018?
>
Yeah...
> > + *
> > + * Permission is hereby granted, free of charge, to any person
> obtaining a
> > + * copy of this software and associated documentation files (the
> "Software"),
> > + * to deal in the Software without restriction, including without
> limitation
> > + * the rights to use, copy, modify, merge, publish, distribute,
> sublicense,
> > + * and/or sell copies of the Software, and to permit persons to whom the
> > + * Software is furnished to do so, subject to the following conditions:
> > + *
> > + * The above copyright notice and this permission notice (including the
> next
> > + * paragraph) shall be included in all copies or substantial portions
> of the
> > + * Software.
> > + *
> > + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
> EXPRESS OR
> > + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
> MERCHANTABILITY,
> > + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
> SHALL
> > + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
> OTHER
> > + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
> ARISING
> > + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
> DEALINGS
> > + * IN THE SOFTWARE.
> > + *
> > + * Authors:
> > + *Jason Ekstrand (ja...@jlekstrand.net)
> > + *
> > + */
> > +
> > +#include "nir.h"
> > +#include "nir_builder.h"
> > +#include "nir_control_flow.h"
> > +#include "nir_worklist.h"
> > +
> > +static bool
> > +block_has_only_discard(nir_block *block)
> > +{
> > + nir_instr *instr =
Re: [Mesa-dev] [PATCH 2/3] nir: Add a discard optimization pass
On Wed, Jul 4, 2018 at 9:13 AM, Jason Ekstrand wrote:
> Many fragment shaders do a discard using relatively little information
> but still put the discard fairly far down in the shader for no good
> reason. If the discard is moved higher up, we can possibly avoid doing
> some or almost all of the work in the shader. When this lets us skip
> texturing operations, it's an especially high win.
>
> One of the biggest offenders here is DXVK. The D3D APIs have different
> rules for discards than OpenGL and Vulkan. One effective way (which is
> what DXVK uses) to implement DX behavior on top of GL or Vulkan is to
> wait until the very end of the shader to discard. This ends up in the
> pessimal case where we always do all of the work before discarding.
> This pass helps some DXVK shaders significantly.
> ---
> src/compiler/Makefile.sources | 1 +
> src/compiler/nir/meson.build | 1 +
> src/compiler/nir/nir.h | 10 +
> src/compiler/nir/nir_opt_discard.c | 404 +
> 4 files changed, 416 insertions(+)
> create mode 100644 src/compiler/nir/nir_opt_discard.c
>
> diff --git a/src/compiler/Makefile.sources b/src/compiler/Makefile.sources
> index 9e3fbdc2612..8600ce81281 100644
> --- a/src/compiler/Makefile.sources
> +++ b/src/compiler/Makefile.sources
> @@ -271,6 +271,7 @@ NIR_FILES = \
> nir/nir_opt_cse.c \
> nir/nir_opt_dce.c \
> nir/nir_opt_dead_cf.c \
> + nir/nir_opt_discard.c \
> nir/nir_opt_gcm.c \
> nir/nir_opt_global_to_local.c \
> nir/nir_opt_if.c \
> diff --git a/src/compiler/nir/meson.build b/src/compiler/nir/meson.build
> index 28aa8de7014..e339258bb94 100644
> --- a/src/compiler/nir/meson.build
> +++ b/src/compiler/nir/meson.build
> @@ -156,6 +156,7 @@ files_libnir = files(
>'nir_opt_cse.c',
>'nir_opt_dce.c',
>'nir_opt_dead_cf.c',
> + 'nir_opt_discard.c',
>'nir_opt_gcm.c',
>'nir_opt_global_to_local.c',
>'nir_opt_if.c',
> diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
> index 92ab3a699cc..44006dac160 100644
> --- a/src/compiler/nir/nir.h
> +++ b/src/compiler/nir/nir.h
> @@ -2022,6 +2022,13 @@ typedef struct nir_shader_compiler_options {
> */
> bool vs_inputs_dual_locations;
>
> + /**
> +* Whether or not derivatives are still a safe operation after a discard
> +* has occurred. Optimization passes may be able to be a bit more
> +* agressive if this is true.
> +*/
> + bool derivatives_safe_after_discard;
> +
> unsigned max_unroll_iterations;
> } nir_shader_compiler_options;
>
> @@ -2899,6 +2906,9 @@ bool nir_opt_dce(nir_shader *shader);
>
> bool nir_opt_dead_cf(nir_shader *shader);
>
> +bool nir_opt_discard_if(nir_shader *shader);
> +bool nir_opt_move_discards_to_top(nir_shader *shader);
> +
> bool nir_opt_gcm(nir_shader *shader, bool value_number);
>
> bool nir_opt_if(nir_shader *shader);
> diff --git a/src/compiler/nir/nir_opt_discard.c
> b/src/compiler/nir/nir_opt_discard.c
> new file mode 100644
> index 000..eb1a8296282
> --- /dev/null
> +++ b/src/compiler/nir/nir_opt_discard.c
> @@ -0,0 +1,404 @@
> +/*
> + * Copyright © 2014 Intel Corporation
2018?
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice (including the next
> + * paragraph) shall be included in all copies or substantial portions of the
> + * Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
> DEALINGS
> + * IN THE SOFTWARE.
> + *
> + * Authors:
> + *Jason Ekstrand (ja...@jlekstrand.net)
> + *
> + */
> +
> +#include "nir.h"
> +#include "nir_builder.h"
> +#include "nir_control_flow.h"
> +#include "nir_worklist.h"
> +
> +static bool
> +block_has_only_discard(nir_block *block)
> +{
> + nir_instr *instr = nir_block_first_instr(block);
> + if (instr == NULL || instr != nir_block_last_instr(block))
> + return false;
> +
> + if (instr->type != nir_instr_type_intrinsic)
> + return false;
> +
> + nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
> + return intrin->intrinsic == nir_intrinsic_discard;
> +}
> +
