st/nir: Make new helpers for constructing built-in NIR shaders.

The state tracker generates several built-in shaders in order to
perform scissored clears, upload/download PBOs, and so on.  These
are currently constructed using TGSI, using ureg and u_simple_shader.

I want to have NIR versions of these shaders, for my Gallium driver
that has a NIR backend but no TGSI support.  To that end, we'll want
a few helpers to help construct simple shaders.

This patch adds two new helpers:

- st_nir_finish_builtin_shader() takes a manually constructed NIR
  shader, applies lowering passes (like st_link_nir would do for GLSL),
  and constructs the pipe_shader_state.

- st_nir_make_passthrough_shader() makes a simple passthrough shader,
  which copies inputs to outputs.  This is similar to u_simple_shaders.

v2: Set info->fs.untyped_color_outputs for vc4/v3d (thanks Eric!).

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Tested-by: Rob Clark <robdclark@gmail.com>
Tested-by: Eric Anholt <eric@anholt.net>

src/mesa/Makefile.sources

@@ -538,6 +538,7 @@ STATETRACKER_FILES = \
 	state_tracker/st_mesa_to_tgsi.c \
 	state_tracker/st_mesa_to_tgsi.h \
 	state_tracker/st_nir.h \
+	state_tracker/st_nir_builtins.c \
 	state_tracker/st_nir_lower_builtin.c \
 	state_tracker/st_nir_lower_tex_src_plane.c \
 	state_tracker/st_nir_lower_uniforms_to_ubo.c \

src/mesa/meson.build

@@ -582,6 +582,7 @@ files_libmesa_gallium = files(
   'state_tracker/st_mesa_to_tgsi.c',
   'state_tracker/st_mesa_to_tgsi.h',
   'state_tracker/st_nir.h',
+  'state_tracker/st_nir_builtins.c',
   'state_tracker/st_nir_lower_builtin.c',
   'state_tracker/st_nir_lower_tex_src_plane.c',
   'state_tracker/st_nir_lower_uniforms_to_ubo.c',

src/mesa/state_tracker/st_nir.h

@@ -55,6 +55,21 @@ st_link_nir(struct gl_context *ctx,
 void st_nir_assign_varying_locations(struct st_context *st,
                                      struct nir_shader *nir);
 
+struct pipe_shader_state *
+st_nir_finish_builtin_shader(struct st_context *st,
+                             struct nir_shader *nir,
+                             const char *name);
+
+struct pipe_shader_state *
+st_nir_make_passthrough_shader(struct st_context *st,
+                               const char *shader_name,
+                               gl_shader_stage stage,
+                               unsigned num_vars,
+                               unsigned *input_locations,
+                               unsigned *output_locations,
+                               unsigned *interpolation_modes,
+                               unsigned sysval_mask);
+
 #ifdef __cplusplus
 }
 #endif

src/mesa/state_tracker/st_nir_builtins.c

@@ -0,0 +1,138 @@
+/*
+ * Copyright © 2018 Intel Corporation
+ *
+ * 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 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 "tgsi/tgsi_from_mesa.h"
+#include "st_glsl_types.h"
+#include "st_nir.h"
+#include "nir_builder.h"
+
+struct pipe_shader_state *
+st_nir_finish_builtin_shader(struct st_context *st,
+                             nir_shader *nir,
+                             const char *name)
+{
+   struct pipe_context *pipe = st->pipe;
+   struct pipe_screen *screen = pipe->screen;
+   enum pipe_shader_type p_stage = pipe_shader_type_from_mesa(nir->info.stage);
+   bool is_scalar =
+      screen->get_shader_param(screen, p_stage, PIPE_SHADER_CAP_SCALAR_ISA);
+
+   nir->info.name = ralloc_strdup(nir, name);
+   nir->info.separate_shader = true;
+   if (nir->info.stage == MESA_SHADER_FRAGMENT)
+      nir->info.fs.untyped_color_outputs = true;
+
+   NIR_PASS_V(nir, nir_lower_global_vars_to_local);
+   NIR_PASS_V(nir, nir_split_var_copies);
+   NIR_PASS_V(nir, nir_lower_var_copies);
+   NIR_PASS_V(nir, nir_lower_system_values);
+
+   if (is_scalar) {
+      nir_variable_mode mask =
+         (nir->info.stage > MESA_SHADER_VERTEX ? nir_var_shader_in : 0) |
+         (nir->info.stage < MESA_SHADER_FRAGMENT ? nir_var_shader_out : 0);
+
+      NIR_PASS_V(nir, nir_lower_io_to_scalar_early, mask);
+   }
+
+   st_nir_opts(nir, is_scalar);
+
+   nir_shader_gather_info(nir, nir_shader_get_entrypoint(nir));
+
+   st_nir_assign_varying_locations(st, nir);
+
+   if (st->ctx->Const.PackedDriverUniformStorage) {
+      NIR_PASS_V(nir, nir_lower_io, nir_var_uniform, st_glsl_type_dword_size,
+                 (nir_lower_io_options)0);
+      NIR_PASS_V(nir, st_nir_lower_uniforms_to_ubo);
+   }
+
+   struct pipe_shader_state state = {
+      .type = PIPE_SHADER_IR_NIR,
+      .ir.nir = nir,
+   };
+
+   switch (nir->info.stage) {
+   case MESA_SHADER_VERTEX:
+      return pipe->create_vs_state(pipe, &state);
+   case MESA_SHADER_TESS_CTRL:
+      return pipe->create_tcs_state(pipe, &state);
+   case MESA_SHADER_TESS_EVAL:
+      return pipe->create_tes_state(pipe, &state);
+   case MESA_SHADER_GEOMETRY:
+      return pipe->create_gs_state(pipe, &state);
+   case MESA_SHADER_FRAGMENT:
+      return pipe->create_fs_state(pipe, &state);
+   default:
+      unreachable("unsupported shader stage");
+      return NULL;
+   }
+}
+
+/**
+ * Make a simple shader that copies inputs to corresponding outputs.
+ */
+struct pipe_shader_state *
+st_nir_make_passthrough_shader(struct st_context *st,
+                               const char *shader_name,
+                               gl_shader_stage stage,
+                               unsigned num_vars,
+                               unsigned *input_locations,
+                               unsigned *output_locations,
+                               unsigned *interpolation_modes,
+                               unsigned sysval_mask)
+{
+   struct nir_builder b;
+   const struct glsl_type *vec4 = glsl_vec4_type();
+   const nir_shader_compiler_options *options =
+      st->ctx->Const.ShaderCompilerOptions[stage].NirOptions;
+
+   nir_builder_init_simple_shader(&b, NULL, stage, options);
+
+   char var_name[15];
+
+   for (unsigned i = 0; i < num_vars; i++) {
+      nir_variable *in;
+      if (sysval_mask & (1 << i)) {
+         snprintf(var_name, sizeof(var_name), "sys_%u", input_locations[i]);
+         in = nir_variable_create(b.shader, nir_var_system_value,
+                                  glsl_int_type(), var_name);
+         in->data.interpolation = INTERP_MODE_FLAT;
+      } else {
+         snprintf(var_name, sizeof(var_name), "in_%u", input_locations[i]);
+         in = nir_variable_create(b.shader, nir_var_shader_in, vec4, var_name);
+      }
+      in->data.location = input_locations[i];
+      if (interpolation_modes)
+         in->data.interpolation = interpolation_modes[i];
+
+      snprintf(var_name, sizeof(var_name), "out_%u", output_locations[i]);
+      nir_variable *out =
+         nir_variable_create(b.shader, nir_var_shader_out, in->type, var_name);
+      out->data.location = output_locations[i];
+      out->data.interpolation = in->data.interpolation;
+
+      nir_copy_var(&b, out, in);
+   }
+
+   return st_nir_finish_builtin_shader(st, b.shader, shader_name);
+}