st/mesa: add a fallback for clear_with_quad when no vs_layer

Not all drivers can set gl_Layer from VS. Add a fallback that passes the
instance id from VS to GS, and then uses the GS to set the layer.

Tested by adding

  quad_buffers |= clear_buffers;
  clear_buffers = 0;

to the st_Clear logic, and forcing set_vertex_shader_layered in all
cases. No piglit regressions (on piglits with 'clear' in the name).

Signed-off-by: Ilia Mirkin <[email protected]>
Reviewed-by: Marek Olšák <[email protected]>
Cc: "10.4 10.3" <[email protected]>

2 files changed, 76 insertions, 0 deletions

diff --git a/src/gallium/auxiliary/util/u_simple_shaders.c b/src/gallium/auxiliary/util/u_simple_shaders.c
index 0eeb7d99173..edb30379b31 100644
--- a/src/gallium/auxiliary/util/u_simple_shaders.c
+++ b/src/gallium/auxiliary/util/u_simple_shaders.c
@@ -130,6 +130,76 @@ void *util_make_layered_clear_vertex_shader(struct pipe_context *pipe)
    return pipe->create_vs_state(pipe, &state);
 }
 
+/**
+ * Takes position and color, and outputs position, color, and instance id.
+ */
+void *util_make_layered_clear_helper_vertex_shader(struct pipe_context *pipe)
+{
+   static const char text[] =
+         "VERT\n"
+         "DCL IN[0]\n"
+         "DCL IN[1]\n"
+         "DCL SV[0], INSTANCEID\n"
+         "DCL OUT[0], POSITION\n"
+         "DCL OUT[1], GENERIC[0]\n"
+         "DCL OUT[2], GENERIC[1]\n"
+
+         "MOV OUT[0], IN[0]\n"
+         "MOV OUT[1], IN[1]\n"
+         "MOV OUT[2].x, SV[0].xxxx\n"
+         "END\n";
+   struct tgsi_token tokens[1000];
+   struct pipe_shader_state state = {tokens};
+
+   if (!tgsi_text_translate(text, tokens, Elements(tokens))) {
+      assert(0);
+      return NULL;
+   }
+   return pipe->create_vs_state(pipe, &state);
+}
+
+/**
+ * Takes position, color, and target layer, and emits vertices on that target
+ * layer, with the specified color.
+ */
+void *util_make_layered_clear_geometry_shader(struct pipe_context *pipe)
+{
+   static const char text[] =
+      "GEOM\n"
+      "PROPERTY GS_INPUT_PRIMITIVE TRIANGLES\n"
+      "PROPERTY GS_OUTPUT_PRIMITIVE TRIANGLE_STRIP\n"
+      "PROPERTY GS_MAX_OUTPUT_VERTICES 3\n"
+      "PROPERTY GS_INVOCATIONS 1\n"
+      "DCL IN[][0], POSITION\n" /* position */
+      "DCL IN[][1], GENERIC[0]\n" /* color */
+      "DCL IN[][2], GENERIC[1]\n" /* vs invocation */
+      "DCL OUT[0], POSITION\n"
+      "DCL OUT[1], GENERIC[0]\n"
+      "DCL OUT[2], LAYER\n"
+      "IMM[0] INT32 {0, 0, 0, 0}\n"
+
+      "MOV OUT[0], IN[0][0]\n"
+      "MOV OUT[1], IN[0][1]\n"
+      "MOV OUT[2].x, IN[0][2].xxxx\n"
+      "EMIT IMM[0].xxxx\n"
+      "MOV OUT[0], IN[1][0]\n"
+      "MOV OUT[1], IN[1][1]\n"
+      "MOV OUT[2].x, IN[1][2].xxxx\n"
+      "EMIT IMM[0].xxxx\n"
+      "MOV OUT[0], IN[2][0]\n"
+      "MOV OUT[1], IN[2][1]\n"
+      "MOV OUT[2].x, IN[2][2].xxxx\n"
+      "EMIT IMM[0].xxxx\n"
+      "END\n";
+   struct tgsi_token tokens[1000];
+   struct pipe_shader_state state = {tokens};
+
+   if (!tgsi_text_translate(text, tokens, Elements(tokens))) {
+      assert(0);
+      return NULL;
+   }
+   return pipe->create_gs_state(pipe, &state);
+}
 
 /**
  * Make simple fragment texture shader:
diff --git a/src/gallium/auxiliary/util/u_simple_shaders.h b/src/gallium/auxiliary/util/u_simple_shaders.h
index 2ba3f2a9ab3..dd282e02a13 100644
--- a/src/gallium/auxiliary/util/u_simple_shaders.h
+++ b/src/gallium/auxiliary/util/u_simple_shaders.h
@@ -62,6 +62,12 @@ extern void *
 util_make_layered_clear_vertex_shader(struct pipe_context *pipe);
 
 extern void *
+util_make_layered_clear_helper_vertex_shader(struct pipe_context *pipe);
+
+extern void *
+util_make_layered_clear_geometry_shader(struct pipe_context *pipe);
+
+extern void *
 util_make_fragment_tex_shader_writemask(struct pipe_context *pipe, 
                                         unsigned tex_target,
                                         unsigned interp_mode,