i965: Use NIR to lower legacy userclipping.

This allows us to drop legacy userclip plane handling in both the vec4
and FS backends, and simplifies a few interfaces.

v2 (Jason Ekstrand):
 - Move brw_nir_lower_legacy_clipping to brw_nir_uniforms.cpp because
   it's i965-specific.
 - Handle adding the params in brw_nir_lower_legacy_clipping
 - Call brw_nir_lower_legacy_clipping from brw_codegen_vs_prog

Co-authored-by: Jason Ekstrand <[email protected]>
Reviewed-by: Jason Ekstrand <[email protected]>
Reviewed-by: Kenneth Graunke <[email protected]>

7 files changed, 3 insertions, 158 deletions

diff --git a/src/intel/compiler/brw_fs.cpp b/src/intel/compiler/brw_fs.cpp
index b16ed3be424..9a29c3ae702 100644
--- a/src/intel/compiler/brw_fs.cpp
+++ b/src/intel/compiler/brw_fs.cpp
@@ -7332,8 +7332,6 @@ fs_visitor::run_vs()
    if (failed)
       return false;
 
-   compute_clip_distance();
-
    emit_urb_writes();
 
    if (shader_time_index >= 0)
diff --git a/src/intel/compiler/brw_fs.h b/src/intel/compiler/brw_fs.h
index 4e7b5781827..2eb49dd5ace 100644
--- a/src/intel/compiler/brw_fs.h
+++ b/src/intel/compiler/brw_fs.h
@@ -80,8 +80,6 @@ public:
 
    fs_reg vgrf(const glsl_type *const type);
    void import_uniforms(fs_visitor *v);
-   void setup_uniform_clipplane_values();
-   void compute_clip_distance();
 
    void VARYING_PULL_CONSTANT_LOAD(const brw::fs_builder &bld,
                                    const fs_reg &dst,
@@ -380,7 +378,6 @@ public:
    fs_reg pixel_w;
    fs_reg delta_xy[BRW_BARYCENTRIC_MODE_COUNT];
    fs_reg shader_start_time;
-   fs_reg userplane[MAX_CLIP_PLANES];
    fs_reg final_gs_vertex_count;
    fs_reg control_data_bits;
    fs_reg invocation_id;
diff --git a/src/intel/compiler/brw_fs_visitor.cpp b/src/intel/compiler/brw_fs_visitor.cpp
index eb23b4087d0..869f8c9017b 100644
--- a/src/intel/compiler/brw_fs_visitor.cpp
+++ b/src/intel/compiler/brw_fs_visitor.cpp
@@ -564,87 +564,6 @@ fs_visitor::emit_fb_writes()
 }
 
 void
-fs_visitor::setup_uniform_clipplane_values()
-{
-   const struct brw_vs_prog_key *key =
-      (const struct brw_vs_prog_key *) this->key;
-
-   if (key->nr_userclip_plane_consts == 0)
-      return;
-
-   assert(stage_prog_data->nr_params == uniforms);
-   brw_stage_prog_data_add_params(stage_prog_data,
-                                  key->nr_userclip_plane_consts * 4);
-
-   for (int i = 0; i < key->nr_userclip_plane_consts; i++) {
-      this->userplane[i] = fs_reg(UNIFORM, uniforms);
-      for (int j = 0; j < 4; ++j) {
-         stage_prog_data->param[uniforms + j] =
-            BRW_PARAM_BUILTIN_CLIP_PLANE(i, j);
-      }
-      uniforms += 4;
-   }
-}
-
-/**
- * Lower legacy fixed-function and gl_ClipVertex clipping to clip distances.
- *
- * This does nothing if the shader uses gl_ClipDistance or user clipping is
- * disabled altogether.
- */
-void fs_visitor::compute_clip_distance()
-{
-   struct brw_vue_prog_data *vue_prog_data = brw_vue_prog_data(prog_data);
-   const struct brw_vs_prog_key *key =
-      (const struct brw_vs_prog_key *) this->key;
-
-   /* Bail unless some sort of legacy clipping is enabled */
-   if (key->nr_userclip_plane_consts == 0)
-      return;
-
-   /* From the GLSL 1.30 spec, section 7.1 (Vertex Shader Special Variables):
-    *
-    *     "If a linked set of shaders forming the vertex stage contains no
-    *     static write to gl_ClipVertex or gl_ClipDistance, but the
-    *     application has requested clipping against user clip planes through
-    *     the API, then the coordinate written to gl_Position is used for
-    *     comparison against the user clip planes."
-    *
-    * This function is only called if the shader didn't write to
-    * gl_ClipDistance.  Accordingly, we use gl_ClipVertex to perform clipping
-    * if the user wrote to it; otherwise we use gl_Position.
-    */
-
-   gl_varying_slot clip_vertex = VARYING_SLOT_CLIP_VERTEX;
-   if (!(vue_prog_data->vue_map.slots_valid & VARYING_BIT_CLIP_VERTEX))
-      clip_vertex = VARYING_SLOT_POS;
-
-   /* If the clip vertex isn't written, skip this.  Typically this means
-    * the GS will set up clipping. */
-   if (outputs[clip_vertex].file == BAD_FILE)
-      return;
-
-   setup_uniform_clipplane_values();
-
-   const fs_builder abld = bld.annotate("user clip distances");
-
-   this->outputs[VARYING_SLOT_CLIP_DIST0] = vgrf(glsl_type::vec4_type);
-   this->outputs[VARYING_SLOT_CLIP_DIST1] = vgrf(glsl_type::vec4_type);
-
-   for (int i = 0; i < key->nr_userclip_plane_consts; i++) {
-      fs_reg u = userplane[i];
-      const fs_reg output = offset(outputs[VARYING_SLOT_CLIP_DIST0 + i / 4],
-                                   bld, i & 3);
-
-      abld.MUL(output, outputs[clip_vertex], u);
-      for (int j = 1; j < 4; j++) {
-         u.nr = userplane[i].nr + j;
-         abld.MAD(output, output, offset(outputs[clip_vertex], bld, j), u);
-      }
-   }
-}
-
-void
 fs_visitor::emit_urb_writes(const fs_reg &gs_vertex_count)
 {
    int slot, urb_offset, length;
diff --git a/src/intel/compiler/brw_nir.h b/src/intel/compiler/brw_nir.h
index d3130476ab1..d8af2e66b3e 100644
--- a/src/intel/compiler/brw_nir.h
+++ b/src/intel/compiler/brw_nir.h
@@ -102,6 +102,9 @@ brw_nir_link_shaders(const struct brw_compiler *compiler,
 
 bool brw_nir_lower_cs_intrinsics(nir_shader *nir,
                                  unsigned dispatch_width);
+void brw_nir_lower_legacy_clipping(nir_shader *nir,
+                                   int nr_userclip_plane_consts,
+                                   struct brw_stage_prog_data *prog_data);
 void brw_nir_lower_vs_inputs(nir_shader *nir,
                              const uint8_t *vs_attrib_wa_flags);
 void brw_nir_lower_vue_inputs(nir_shader *nir,
diff --git a/src/intel/compiler/brw_vec4.h b/src/intel/compiler/brw_vec4.h
index a8e0049bf9c..ab2ecc47f58 100644
--- a/src/intel/compiler/brw_vec4.h
+++ b/src/intel/compiler/brw_vec4.h
@@ -109,7 +109,6 @@ public:
    int *virtual_grf_start;
    int *virtual_grf_end;
    brw::vec4_live_variables *live_intervals;
-   dst_reg userplane[MAX_CLIP_PLANES];
 
    bool need_all_constants_in_pull_buffer;
 
diff --git a/src/intel/compiler/brw_vec4_vs.h b/src/intel/compiler/brw_vec4_vs.h
index b62e03aa8d9..7662b6a73d6 100644
--- a/src/intel/compiler/brw_vec4_vs.h
+++ b/src/intel/compiler/brw_vec4_vs.h
@@ -49,8 +49,6 @@ protected:
 
 private:
    int setup_attributes(int payload_reg);
-   void setup_uniform_clipplane_values();
-   void emit_clip_distances(dst_reg reg, int offset);
 
    const struct brw_vs_prog_key *const key;
    struct brw_vs_prog_data * const vs_prog_data;
diff --git a/src/intel/compiler/brw_vec4_vs_visitor.cpp b/src/intel/compiler/brw_vec4_vs_visitor.cpp
index 5aa1b9ac0b2..ab351dbd39b 100644
--- a/src/intel/compiler/brw_vec4_vs_visitor.cpp
+++ b/src/intel/compiler/brw_vec4_vs_visitor.cpp
@@ -87,77 +87,8 @@ vec4_vs_visitor::emit_urb_slot(dst_reg reg, int varying)
 
 
 void
-vec4_vs_visitor::emit_clip_distances(dst_reg reg, int offset)
-{
-   /* From the GLSL 1.30 spec, section 7.1 (Vertex Shader Special Variables):
-    *
-    *     "If a linked set of shaders forming the vertex stage contains no
-    *     static write to gl_ClipVertex or gl_ClipDistance, but the
-    *     application has requested clipping against user clip planes through
-    *     the API, then the coordinate written to gl_Position is used for
-    *     comparison against the user clip planes."
-    *
-    * This function is only called if the shader didn't write to
-    * gl_ClipDistance.  Accordingly, we use gl_ClipVertex to perform clipping
-    * if the user wrote to it; otherwise we use gl_Position.
-    */
-   gl_varying_slot clip_vertex = VARYING_SLOT_CLIP_VERTEX;
-   if (!(prog_data->vue_map.slots_valid & VARYING_BIT_CLIP_VERTEX)) {
-      clip_vertex = VARYING_SLOT_POS;
-   }
-
-   for (int i = 0; i + offset < key->nr_userclip_plane_consts && i < 4;
-        ++i) {
-      reg.writemask = 1 << i;
-      emit(DP4(reg,
-               src_reg(output_reg[clip_vertex][0]),
-               src_reg(this->userplane[i + offset])));
-   }
-}
-
-
-void
-vec4_vs_visitor::setup_uniform_clipplane_values()
-{
-   if (key->nr_userclip_plane_consts == 0)
-      return;
-
-   assert(stage_prog_data->nr_params == (unsigned)this->uniforms * 4);
-   brw_stage_prog_data_add_params(stage_prog_data,
-                                  key->nr_userclip_plane_consts * 4);
-
-   for (int i = 0; i < key->nr_userclip_plane_consts; ++i) {
-      this->userplane[i] = dst_reg(UNIFORM, this->uniforms);
-      this->userplane[i].type = BRW_REGISTER_TYPE_F;
-      for (int j = 0; j < 4; ++j) {
-         stage_prog_data->param[this->uniforms * 4 + j] =
-            BRW_PARAM_BUILTIN_CLIP_PLANE(i, j);
-      }
-      ++this->uniforms;
-   }
-}
-
-
-void
 vec4_vs_visitor::emit_thread_end()
 {
-   setup_uniform_clipplane_values();
-
-   /* Lower legacy ff and ClipVertex clipping to clip distances */
-   if (key->nr_userclip_plane_consts > 0) {
-      current_annotation = "user clip distances";
-
-      output_reg[VARYING_SLOT_CLIP_DIST0][0] =
-         dst_reg(this, glsl_type::vec4_type);
-      output_reg[VARYING_SLOT_CLIP_DIST1][0] =
-         dst_reg(this, glsl_type::vec4_type);
-      output_num_components[VARYING_SLOT_CLIP_DIST0][0] = 4;
-      output_num_components[VARYING_SLOT_CLIP_DIST1][0] = 4;
-
-      emit_clip_distances(output_reg[VARYING_SLOT_CLIP_DIST0][0], 0);
-      emit_clip_distances(output_reg[VARYING_SLOT_CLIP_DIST1][0], 4);
-   }
-
    /* For VS, we always end the thread by emitting a single vertex.
     * emit_urb_write_opcode() will take care of setting the eot flag on the
     * SEND instruction.