mesa/st: Add get_compute_program

Add a function to create and cache the compute programs that will be
used to transcode ASTC to DXT5.

Note that the error paths in st_create_context_priv may actually lead to
segfaults if hit. I've been able to work around them by 1) moving them
further down and 2) returning early from st_glFlush if st->pipe is NULL.
I don't know if that's the right solution however.

Reviewed-by: Tapani Pälli <tapani.palli@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/19827>

src/mesa/meson.build

@@ -364,6 +364,8 @@ files_libmesa = files(
   'state_tracker/st_scissor.h',
   'state_tracker/st_shader_cache.c',
   'state_tracker/st_shader_cache.h',
+  'state_tracker/st_texcompress_compute.c',
+  'state_tracker/st_texcompress_compute.h',
   'state_tracker/st_texture.c',
   'state_tracker/st_texture.h',
   'state_tracker/st_util.h',

src/mesa/state_tracker/st_context.c

@@ -56,6 +56,7 @@
 #include "st_program.h"
 #include "st_sampler_view.h"
 #include "st_shader_cache.h"
+#include "st_texcompress_compute.h"
 #include "st_texture.h"
 #include "st_util.h"
 #include "pipe/p_context.h"
@@ -354,6 +355,10 @@ st_destroy_context_priv(struct st_context *st, bool destroy_pipe)
    st_destroy_drawpix(st);
    st_destroy_drawtex(st);
    st_destroy_pbo_helpers(st);
+
+   if (st->transcode_astc)
+      st_destroy_texcompress_compute(st);
+
    st_destroy_bound_texture_handles(st);
    st_destroy_bound_image_handles(st);
 
@@ -772,6 +777,17 @@ st_create_context_priv(struct gl_context *ctx, struct pipe_context *pipe,
       return NULL;
    }
 
+   if (_mesa_has_compute_shaders(ctx) &&
+       st->transcode_astc && !st_init_texcompress_compute(st)) {
+      /* Transcoding ASTC to DXT5 using compute shaders can provide a
+       * significant performance benefit over the CPU path. It isn't strictly
+       * necessary to fail if we can't use the compute shader path, but it's
+       * very convenient to do so. This should be rare.
+       */
+      st_destroy_context_priv(st, false);
+      return NULL;
+   }
+
    /* This must be done after extensions are initialized to enable persistent
     * mappings immediately.
     */

src/mesa/state_tracker/st_context.h

@@ -342,6 +342,10 @@ struct st_context
       bool use_gs;
    } pbo;
 
+   struct {
+      struct gl_program **progs;
+   } texcompress_compute;
+
    /** for drawing with st_util_vertex */
    struct cso_velems_state util_velems;
 

src/mesa/state_tracker/st_texcompress_compute.c

@@ -0,0 +1,98 @@
+/**************************************************************************
+ *
+ * Copyright © 2022 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 (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 "main/shaderapi.h"
+#include "main/shaderobj.h"
+
+#include "state_tracker/st_context.h"
+#include "state_tracker/st_texcompress_compute.h"
+
+#include "util/u_string.h"
+
+enum compute_program_id {
+   COMPUTE_PROGRAM_COUNT
+};
+
+static struct gl_program * PRINTFLIKE(3, 4)
+get_compute_program(struct st_context *st,
+                    enum compute_program_id prog_id,
+                    const char *source_fmt, ...)
+{
+   /* Try to get the program from the cache. */
+   assert(prog_id < COMPUTE_PROGRAM_COUNT);
+   if (st->texcompress_compute.progs[prog_id])
+      return st->texcompress_compute.progs[prog_id];
+
+   /* Cache miss. Create the final source string. */
+   char *source_str;
+   va_list ap;
+   va_start(ap, source_fmt);
+   int num_printed_bytes = vasprintf(&source_str, source_fmt, ap);
+   va_end(ap);
+   if (num_printed_bytes == -1)
+      return NULL;
+
+   /* Compile and link the shader. Then, destroy the shader string. */
+   const char *strings[] = { source_str };
+   GLuint program =
+      _mesa_CreateShaderProgramv_impl(st->ctx, GL_COMPUTE_SHADER, 1, strings);
+   free(source_str);
+
+   struct gl_shader_program *shProg =
+      _mesa_lookup_shader_program(st->ctx, program);
+   if (!shProg)
+      return NULL;
+
+   if (shProg->data->LinkStatus == LINKING_FAILURE) {
+      fprintf(stderr, "Linking failed:\n%s\n", shProg->data->InfoLog);
+      _mesa_reference_shader_program(st->ctx, &shProg, NULL);
+      return NULL;
+   }
+
+   /* Cache the program and return it. */
+   return st->texcompress_compute.progs[prog_id] =
+          shProg->_LinkedShaders[MESA_SHADER_COMPUTE]->Program;
+}
+
+bool
+st_init_texcompress_compute(struct st_context *st)
+{
+   st->texcompress_compute.progs =
+      calloc(COMPUTE_PROGRAM_COUNT, sizeof(struct gl_program *));
+   if (!st->texcompress_compute.progs)
+      return false;
+
+   return true;
+}
+
+void
+st_destroy_texcompress_compute(struct st_context *st)
+{
+   /* The programs in the array are part of the gl_context (in st->ctx).They
+    * are automatically destroyed when the context is destroyed (via
+    * _mesa_free_context_data -> ... -> free_shader_program_data_cb).
+    */
+   free(st->texcompress_compute.progs);
+}

src/mesa/state_tracker/st_texcompress_compute.h

@@ -0,0 +1,35 @@
+/**************************************************************************
+ *
+ * Copyright © 2022 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 (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.
+ *
+ **************************************************************************/
+
+#ifndef ST_TEXCOMPRESS_COMPUTE_H
+#define ST_TEXCOMPRESS_COMPUTE_H
+
+bool
+st_init_texcompress_compute(struct st_context *st);
+
+void
+st_destroy_texcompress_compute(struct st_context *st);
+
+#endif /* ST_TEXCOMPRESS_COMPUTE_H */