[Mesa-dev] [PATCH 02/12] i965: Remove legacy clip plane handling from geometry shaders.

[Kenneth Graunke]

We only support geometry shaders in core profiles, where gl_ClipVertex
doesn't exist.  Presumably the even older behavior of clipping to
gl_Position isn't supported either.  In fact, GLSL 1.50 page 76 claims:

"The shader must also set all values in gl_ClipDistance that have been
 enabled via the OpenGL API, or results are undefined."

So we don't need to handle legacy clipping in geometry shaders.  I think
Paul added this back when we were considering supporting the old
GL_ARB_geometry_shader4 extension.

This removes a non-orthagonal state dependency on GS compilation.

Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
---
 src/mesa/drivers/dri/i965/brw_context.h |  5 -----
 src/mesa/drivers/dri/i965/brw_gs.c      | 11 -----------
 src/mesa/drivers/dri/i965/brw_vs.c      | 25 ++++++++-----------------
 3 files changed, 8 insertions(+), 33 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_context.h b/src/mesa/drivers/dri/i965/brw_context.h
index b52bca7..c9c47dd 100644
--- a/src/mesa/drivers/dri/i965/brw_context.h
+++ b/src/mesa/drivers/dri/i965/brw_context.h
@@ -2058,11 +2058,6 @@ void gen8_hiz_exec(struct brw_context *brw, struct intel_mipmap_tree *mt,
 uint32_t get_hw_prim_for_gl_prim(int mode);
 
 void
-brw_setup_vue_key_clip_info(struct brw_context *brw,
-                            struct brw_vue_prog_key *key,
-                            bool program_uses_clip_distance);
-
-void
 gen6_upload_push_constants(struct brw_context *brw,
                            const struct gl_program *prog,
                            const struct brw_stage_prog_data *prog_data,
diff --git a/src/mesa/drivers/dri/i965/brw_gs.c b/src/mesa/drivers/dri/i965/brw_gs.c
index 5c0d923..f1da635 100644
--- a/src/mesa/drivers/dri/i965/brw_gs.c
+++ b/src/mesa/drivers/dri/i965/brw_gs.c
@@ -121,15 +121,6 @@ brw_codegen_gs_prog(struct brw_context *brw,
 
    GLbitfield64 outputs_written = gp->program.Base.OutputsWritten;
 
-   /* In order for legacy clipping to work, we need to populate the clip
-    * distance varying slots whenever clipping is enabled, even if the vertex
-    * shader doesn't write to gl_ClipDistance.
-    */
-   if (c.key.base.userclip_active) {
-      outputs_written |= BITFIELD64_BIT(VARYING_SLOT_CLIP_DIST0);
-      outputs_written |= BITFIELD64_BIT(VARYING_SLOT_CLIP_DIST1);
-   }
-
    brw_compute_vue_map(brw->intelScreen->devinfo,
                        &c.prog_data.base.vue_map, outputs_written);
 
@@ -310,8 +301,6 @@ brw_gs_populate_key(struct brw_context *brw,
    memset(key, 0, sizeof(*key));
 
    key->base.program_string_id = gp->id;
-   brw_setup_vue_key_clip_info(brw, &key->base,
-                               gp->program.Base.UsesClipDistanceOut);
 
    /* _NEW_TEXTURE */
    brw_populate_sampler_prog_key_data(ctx, prog, stage_state->sampler_count,
diff --git a/src/mesa/drivers/dri/i965/brw_vs.c b/src/mesa/drivers/dri/i965/brw_vs.c
index c53cb49..211929a 100644
--- a/src/mesa/drivers/dri/i965/brw_vs.c
+++ b/src/mesa/drivers/dri/i965/brw_vs.c
@@ -279,21 +279,6 @@ brw_vs_debug_recompile(struct brw_context *brw,
    }
 }
 
-
-void
-brw_setup_vue_key_clip_info(struct brw_context *brw,
-                            struct brw_vue_prog_key *key,
-                            bool program_uses_clip_distance)
-{
-   struct gl_context *ctx = &brw->ctx;
-
-   key->userclip_active = (ctx->Transform.ClipPlanesEnabled != 0);
-   if (key->userclip_active && !program_uses_clip_distance) {
-      key->nr_userclip_plane_consts
-         = _mesa_logbase2(ctx->Transform.ClipPlanesEnabled) + 1;
-   }
-}
-
 static bool
 brw_vs_state_dirty(struct brw_context *brw)
 {
@@ -325,8 +310,14 @@ brw_vs_populate_key(struct brw_context *brw,
     * the inputs it asks for, whether they are varying or not.
     */
    key->base.program_string_id = vp->id;
-   brw_setup_vue_key_clip_info(brw, &key->base,
-                               vp->program.Base.UsesClipDistanceOut);
+
+   if (ctx->Transform.ClipPlanesEnabled != 0) {
+      key->base.userclip_active = true;
+      if (!vp->program.Base.UsesClipDistanceOut) {
+         key->base.nr_userclip_plane_consts =
+            _mesa_logbase2(ctx->Transform.ClipPlanesEnabled) + 1;
+      }
+   }
 
    /* _NEW_POLYGON */
    if (brw->gen < 6) {
-- 
2.5.0