i965: Delete the brw_vue_program_key::userclip_active flag.

There are two uses of this flag.

The primary use is checking whether we need to emit code to convert
legacy gl_ClipVertex/gl_Position clipping to clip distances.  In this
case, we also have to upload the clip planes as uniforms, which means
setting nr_userclip_plane_consts to a positive value.  Checking if it's
> 0 works for detecting this case.

Gen4-5 also wants to know whether we're doing clipping at all, so it can
emit user clip flags.  Checking if output_reg[VARYING_SLOT_CLIP_DIST0]
is set to a real register suffices for this.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Chris Forbes <chrisf@ijw.co.nz>

src/mesa/drivers/dri/i965/brw_fs_visitor.cpp

@@ -810,7 +810,7 @@ void fs_visitor::compute_clip_distance(gl_clip_plane *clip_planes)
       (const struct brw_vue_prog_key *) this->key;
 
    /* Bail unless some sort of legacy clipping is enabled */
-   if (!key->userclip_active || prog->UsesClipDistanceOut)
+   if (key->nr_userclip_plane_consts == 0)
       return;
 
    /* From the GLSL 1.30 spec, section 7.1 (Vertex Shader Special Variables):

src/mesa/drivers/dri/i965/brw_program.h

@@ -81,15 +81,12 @@ struct brw_sampler_prog_key_data {
 struct brw_vue_prog_key {
    unsigned program_string_id;
 
-   /**
-    * True if at least one clip flag is enabled, regardless of whether the
-    * shader uses clip planes or gl_ClipDistance.
-    */
-   bool userclip_active:1;
-
    /**
     * How many user clipping planes are being uploaded to the vertex shader as
     * push constants.
+    *
+    * These are used for lowering legacy gl_ClipVertex/gl_Position clipping to
+    * clip distances.
     */
    unsigned nr_userclip_plane_consts:4;
 

src/mesa/drivers/dri/i965/brw_vec4.cpp

@@ -1750,7 +1750,7 @@ vec4_visitor::run(gl_clip_plane *clip_planes)
    }
    base_ir = NULL;
 
-   if (key->userclip_active && !prog->UsesClipDistanceOut)
+   if (key->nr_userclip_plane_consts > 0)
       setup_uniform_clipplane_values(clip_planes);
 
    emit_thread_end();

src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp

@@ -3121,7 +3121,8 @@ vec4_visitor::emit_psiz_and_flags(dst_reg reg)
 {
    if (devinfo->gen < 6 &&
        ((prog_data->vue_map.slots_valid & VARYING_BIT_PSIZ) ||
-        key->userclip_active || devinfo->has_negative_rhw_bug)) {
+        output_reg[VARYING_SLOT_CLIP_DIST0].file != BAD_FILE ||
+        devinfo->has_negative_rhw_bug)) {
       dst_reg header1 = dst_reg(this, glsl_type::uvec4_type);
       dst_reg header1_w = header1;
       header1_w.writemask = WRITEMASK_W;
@@ -3136,7 +3137,7 @@ vec4_visitor::emit_psiz_and_flags(dst_reg reg)
 	 emit(AND(header1_w, src_reg(header1_w), 0x7ff << 8));
       }
 
-      if (key->userclip_active) {
+      if (output_reg[VARYING_SLOT_CLIP_DIST0].file != BAD_FILE) {
          current_annotation = "Clipping flags";
          dst_reg flags0 = dst_reg(this, glsl_type::uint_type);
          dst_reg flags1 = dst_reg(this, glsl_type::uint_type);
@@ -3354,7 +3355,7 @@ vec4_visitor::emit_vertex()
    }
 
    /* Lower legacy ff and ClipVertex clipping to clip distances */
-   if (key->userclip_active && !prog->UsesClipDistanceOut) {
+   if (key->nr_userclip_plane_consts > 0) {
       current_annotation = "user clip distances";
 
       output_reg[VARYING_SLOT_CLIP_DIST0] = dst_reg(this, glsl_type::vec4_type);

src/mesa/drivers/dri/i965/brw_vs.c

@@ -172,7 +172,7 @@ brw_codegen_vs_prog(struct brw_context *brw,
     * distance varying slots whenever clipping is enabled, even if the vertex
     * shader doesn't write to gl_ClipDistance.
     */
-   if (key->base.userclip_active) {
+   if (key->base.nr_userclip_plane_consts > 0) {
       outputs_written |= BITFIELD64_BIT(VARYING_SLOT_CLIP_DIST0);
       outputs_written |= BITFIELD64_BIT(VARYING_SLOT_CLIP_DIST1);
    }
@@ -257,10 +257,7 @@ brw_vs_debug_recompile(struct brw_context *brw,
                          key->gl_attrib_wa_flags[i]);
    }
 
-   found |= key_debug(brw, "user clip flags",
-                      old_key->base.userclip_active, key->base.userclip_active);
-
-   found |= key_debug(brw, "user clipping planes as push constants",
+   found |= key_debug(brw, "legacy user clipping",
                       old_key->base.nr_userclip_plane_consts,
                       key->base.nr_userclip_plane_consts);
 
@@ -311,12 +308,10 @@ brw_vs_populate_key(struct brw_context *brw,
     */
    key->base.program_string_id = vp->id;
 
-   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;
-      }
+   if (ctx->Transform.ClipPlanesEnabled != 0 &&
+       !vp->program.Base.UsesClipDistanceOut) {
+      key->base.nr_userclip_plane_consts =
+         _mesa_logbase2(ctx->Transform.ClipPlanesEnabled) + 1;
    }
 
    /* _NEW_POLYGON */