[Mesa-dev] [PATCH 4/8] nir: add some helpers for doing linking

[Eduardo Lima Mitev]

On 09/13/2017 01:37 AM, Timothy Arceri wrote:
> The initial helpers as support for removing unused varyings between
> stages.
> ---
>  src/compiler/Makefile.sources          |   1 +
>  src/compiler/nir/nir.h                 |   6 ++
>  src/compiler/nir/nir_linking_helpers.c | 136 +++++++++++++++++++++++++++++++++
>  3 files changed, 143 insertions(+)
>  create mode 100644 src/compiler/nir/nir_linking_helpers.c
> 
> diff --git a/src/compiler/Makefile.sources b/src/compiler/Makefile.sources
> index 0153df2d812..9c7f057eecf 100644
> --- a/src/compiler/Makefile.sources
> +++ b/src/compiler/Makefile.sources
> @@ -203,6 +203,7 @@ NIR_FILES = \
>  	nir/nir_instr_set.h \
>  	nir/nir_intrinsics.c \
>  	nir/nir_intrinsics.h \
> +	nir/nir_linking_helpers.c \
>  	nir/nir_liveness.c \
>  	nir/nir_loop_analyze.c \
>  	nir/nir_loop_analyze.h \
> diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
> index e52a1006896..1e89c74d14c 100644
> --- a/src/compiler/nir/nir.h
> +++ b/src/compiler/nir/nir.h
> @@ -2448,6 +2448,12 @@ void nir_shader_gather_info(nir_shader *shader, nir_function_impl *entrypoint);
>  void nir_assign_var_locations(struct exec_list *var_list, unsigned *size,
>                                int (*type_size)(const struct glsl_type *));
>  
> +/* Some helpers to do very simple linking */
> +bool nir_remove_unwritten_outputs(nir_shader *shader);
> +bool nir_remove_unread_outputs(nir_shader *shader, uint64_t outputs_read);
> +bool nir_remove_unused_varyings(nir_shader *producer, nir_shader *consumer);
> +bool nir_compact_varyings(nir_shader *producer, nir_shader *consumer);
> +
>  typedef enum {
>     /* If set, this forces all non-flat fragment shader inputs to be
>      * interpolated as if with the "sample" qualifier.  This requires
> diff --git a/src/compiler/nir/nir_linking_helpers.c b/src/compiler/nir/nir_linking_helpers.c
> new file mode 100644
> index 00000000000..d567aa713ad
> --- /dev/null
> +++ b/src/compiler/nir/nir_linking_helpers.c
> @@ -0,0 +1,136 @@
> +/*
> + * Copyright © 2015 Intel Corporation
>

2017 :)

> + *
> + * 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.
> + */
> +
> +#include "nir.h"
> +#include "util/set.h"
> +#include "util/hash_table.h"
> +
> +/* This file contains various little helpers for doing simple linking in
> + * NIR.  Eventually, we'll probably want a full-blown varying packing
> + * implementation in here.  Right now, it just deletes unused things.
> + */
> +
> +static void
> +find_live_tcs_outputs(nir_shader *shader, struct set *live)
> +{
> +   nir_foreach_function(function, shader) {
> +      if (function->impl) {
> +         nir_foreach_block(block, function->impl) {
> +            nir_foreach_instr(instr, block) {
> +               if (instr->type == nir_instr_type_intrinsic) {
> +                  nir_intrinsic_instr *intrin_instr =
> +                     nir_instr_as_intrinsic(instr);
> +                  if (intrin_instr->intrinsic == nir_intrinsic_load_var &&
> +                      intrin_instr->variables[0]->var->data.mode ==
> +                      nir_var_shader_out) {
> +                     _mesa_set_add(live, intrin_instr->variables[0]->var);
> +                  }
> +               }
> +            }
> +         }
> +      }
> +   }
> +}
> +

Maybe rewrite the above function to use "continue" and avoid so much
nesting? More like this one below, for example.

> +static bool
> +remove_unused_io_vars(nir_shader *shader, struct exec_list *var_list,
> +                      uint64_t used_by_other_stage,
> +                      struct set *live_tcs_outputs)
> +{
> +   bool progress = false;
> +
> +   nir_foreach_variable_safe(var, var_list) {
> +      /* TODO: add patch support */
> +      if (var->data.patch)
> +         continue;
> +
> +      if (var->data.location < VARYING_SLOT_VAR0 && var->data.location >= 0)
> +         continue;
> +
> +      if (var->data.always_active_io)
> +         continue;
> +
> +      if (!(used_by_other_stage &
> +            nir_variable_get_io_mask(var, shader->stage))) {
> +         /* Each TCS invocation can read data written by other TCS invocations,
> +          * so even if the outputs are not used by the TES we must also make
> +          * sure they are not read by the TCS before demoting them to globals.
> +          */
> +         if (live_tcs_outputs) {
> +            assert(shader->stage == MESA_SHADER_TESS_CTRL &&
> +                   var->data.mode == nir_var_shader_out);
> +
> +            struct set_entry *entry = _mesa_set_search(live_tcs_outputs, var);
> +            if (entry) {
> +               continue;
> +            }
> +         }
> +
> +         /* This one is invalid, make it a global variable instead */
> +         var->data.location = 0;
> +         var->data.mode = nir_var_global;
> +
> +         exec_node_remove(&var->node);
> +         exec_list_push_tail(&shader->globals, &var->node);
> +
> +         progress = true;
> +      }
> +   }
> +
> +   return progress;
> +}
> +
> +bool
> +nir_remove_unused_varyings(nir_shader *producer, nir_shader *consumer)
> +{
> +   assert(producer->stage != MESA_SHADER_FRAGMENT);
> +   assert(consumer->stage != MESA_SHADER_VERTEX);
> +
> +   uint64_t read = 0, written = 0;
> +
> +   nir_foreach_variable(var, &producer->outputs)
> +      written |= nir_variable_get_io_mask(var, producer->stage);
> +
> +   nir_foreach_variable(var, &consumer->inputs)
> +      read |= nir_variable_get_io_mask(var, consumer->stage);
> +
> +   struct set *live_tcs_outputs;
> +   if (producer->stage == MESA_SHADER_TESS_CTRL) {
> +      live_tcs_outputs =
> +         _mesa_set_create(NULL, _mesa_hash_pointer, _mesa_key_pointer_equal);
> +      find_live_tcs_outputs(producer, live_tcs_outputs);
> +   } else {
> +      live_tcs_outputs = NULL;
> +   }
> +
> +   bool progress = false;
> +   progress = remove_unused_io_vars(producer, &producer->outputs, read,
> +                                    live_tcs_outputs);
> +
> +   progress = remove_unused_io_vars(consumer, &consumer->inputs, written,
> +                                    NULL) || progress;
> +
> +   _mesa_set_destroy(live_tcs_outputs, NULL);
> +
> +   return progress;
> +}
>