mesa/gallium: automatically lower two-sided lighting

Reviewed-by: Marek Olšák <marek.olsak@amd.com>

src/gallium/auxiliary/util/u_screen.c

@@ -397,6 +397,7 @@ u_pipe_screen_get_param_defaults(struct pipe_screen *pscreen,
    case PIPE_CAP_FLATSHADE:
    case PIPE_CAP_ALPHA_TEST:
    case PIPE_CAP_POINT_SIZE_FIXED:
+   case PIPE_CAP_TWO_SIDED_COLOR:
       return 1;
 
    default:

src/gallium/docs/source/screen.rst

@@ -562,6 +562,7 @@ The integer capabilities:
 * ``PIPE_CAP_ALPHA_TEST``: Driver supports alpha-testing.
 * ``PIPE_CAP_POINT_SIZE_FIXED``: Driver supports point-sizes that are fixed,
   as opposed to writing gl_PointSize for every point.
+* ``PIPE_CAP_TWO_SIDED_COLOR``: Driver supports two-sided coloring.
 
 .. _pipe_capf:
 

src/gallium/include/pipe/p_defines.h

@@ -907,6 +907,7 @@ enum pipe_cap
    PIPE_CAP_FLATSHADE,
    PIPE_CAP_ALPHA_TEST,
    PIPE_CAP_POINT_SIZE_FIXED,
+   PIPE_CAP_TWO_SIDED_COLOR,
 };
 
 /**

src/mesa/state_tracker/st_atom_rasterizer.c

@@ -101,7 +101,8 @@ st_update_rasterizer(struct st_context *st)
                              GL_FIRST_VERTEX_CONVENTION_EXT;
 
    /* _NEW_LIGHT | _NEW_PROGRAM */
-   raster->light_twoside = _mesa_vertex_program_two_side_enabled(ctx);
+   if (!st->lower_two_sided_color)
+      raster->light_twoside = _mesa_vertex_program_two_side_enabled(ctx);
 
    /*_NEW_LIGHT | _NEW_BUFFERS */
    raster->clamp_vertex_color = !st->clamp_vert_color_in_shader &&

src/mesa/state_tracker/st_atom_shader.c

@@ -38,6 +38,7 @@
 #include "main/imports.h"
 #include "main/mtypes.h"
 #include "main/framebuffer.h"
+#include "main/state.h"
 #include "main/texobj.h"
 #include "main/texstate.h"
 #include "program/program.h"
@@ -128,6 +129,10 @@ st_update_fp( struct st_context *st )
       if (st->lower_alpha_test && _mesa_is_alpha_test_enabled(st->ctx))
          key.lower_alpha_func = st->ctx->Color.AlphaFunc;
 
+      /* _NEW_LIGHT | _NEW_PROGRAM */
+      key.lower_two_sided_color = st->lower_two_sided_color &&
+         _mesa_vertex_program_two_side_enabled(st->ctx);
+
       /* _NEW_FRAG_CLAMP */
       key.clamp_color = st->clamp_frag_color_in_shader &&
                         st->ctx->Color._ClampFragmentColor;

src/mesa/state_tracker/st_context.c

@@ -228,7 +228,7 @@ st_invalidate_state(struct gl_context *ctx)
       st->dirty |= ST_NEW_RASTERIZER;
 
    if ((new_state & _NEW_LIGHT) &&
-       st->lower_flatshade)
+       (st->lower_flatshade || st->lower_two_sided_color))
       st->dirty |= ST_NEW_FS_STATE;
 
    if (new_state & _NEW_PROJECTION &&
@@ -679,6 +679,8 @@ st_create_context_priv(struct gl_context *ctx, struct pipe_context *pipe,
       !screen->get_param(screen, PIPE_CAP_ALPHA_TEST);
    st->lower_point_size =
       !screen->get_param(screen, PIPE_CAP_POINT_SIZE_FIXED);
+   st->lower_two_sided_color =
+      !screen->get_param(screen, PIPE_CAP_TWO_SIDED_COLOR);
 
    st->has_hw_atomics =
       screen->get_shader_param(screen, PIPE_SHADER_FRAGMENT,
@@ -751,7 +753,8 @@ st_create_context_priv(struct gl_context *ctx, struct pipe_context *pipe,
          !st->lower_alpha_test &&
          !st->clamp_frag_color_in_shader &&
          !st->clamp_frag_depth_in_shader &&
-         !st->force_persample_in_shader;
+         !st->force_persample_in_shader &&
+         !st->lower_two_sided_color;
 
    st->shader_has_one_variant[MESA_SHADER_TESS_CTRL] = st->has_shareable_shaders;
    st->shader_has_one_variant[MESA_SHADER_TESS_EVAL] =

src/mesa/state_tracker/st_context.h

@@ -150,6 +150,7 @@ struct st_context
    boolean lower_flatshade;
    boolean lower_alpha_test;
    boolean lower_point_size;
+   boolean lower_two_sided_color;
 
    /**
     * If a shader can be created when we get its source.

src/mesa/state_tracker/st_program.c

@@ -1181,6 +1181,9 @@ st_create_fp_variant(struct st_context *st,
                     false, alpha_ref_state);
       }
 
+      if (key->lower_two_sided_color)
+         NIR_PASS_V(tgsi.ir.nir, nir_lower_two_sided_color);
+
       if (key->persample_shading) {
           nir_shader *shader = tgsi.ir.nir;
           nir_foreach_variable(var, &shader->inputs)

src/mesa/state_tracker/st_program.h

@@ -126,6 +126,9 @@ struct st_fp_variant_key
    /** for ARB_depth_clamp */
    GLuint lower_depth_clamp:1;
 
+   /** for OpenGL 1.0 on modern hardware */
+   GLuint lower_two_sided_color:1;
+
    /** needed for ATI_fragment_shader */
    char texture_targets[MAX_NUM_FRAGMENT_REGISTERS_ATI];