nir: support lowering clipdist to arrays

This allows us to make sure clipdist is emitted as a scalar array rather
than two vec4s. This matches SPIR-V semantics, and will be useful for
Zink.

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

src/broadcom/compiler/vir.c

@@ -825,7 +825,7 @@ v3d_nir_lower_vs_late(struct v3d_compile *c)
 
         if (c->key->ucp_enables) {
                 NIR_PASS_V(c->s, nir_lower_clip_vs, c->key->ucp_enables,
-                           false);
+                           false, false);
                 NIR_PASS_V(c->s, nir_lower_io_to_scalar,
                            nir_var_shader_out);
         }
@@ -850,7 +850,8 @@ v3d_nir_lower_fs_late(struct v3d_compile *c)
         }
 
         if (c->key->ucp_enables)
-                NIR_PASS_V(c->s, nir_lower_clip_fs, c->key->ucp_enables);
+                NIR_PASS_V(c->s, nir_lower_clip_fs, c->key->ucp_enables,
+                           false);
 
         /* Note: FS input scalarizing must happen after
          * nir_lower_two_sided_color, which only handles a vec4 at a time.

src/compiler/nir/nir.h

@@ -3906,9 +3906,13 @@ bool nir_lower_idiv(nir_shader *shader);
 
 bool nir_lower_input_attachments(nir_shader *shader, bool use_fragcoord_sysval);
 
-bool nir_lower_clip_vs(nir_shader *shader, unsigned ucp_enables, bool use_vars);
-bool nir_lower_clip_gs(nir_shader *shader, unsigned ucp_enables);
-bool nir_lower_clip_fs(nir_shader *shader, unsigned ucp_enables);
+bool nir_lower_clip_vs(nir_shader *shader, unsigned ucp_enables,
+                       bool use_vars,
+                       bool use_clipdist_array);
+bool nir_lower_clip_gs(nir_shader *shader, unsigned ucp_enables,
+                       bool use_clipdist_array);
+bool nir_lower_clip_fs(nir_shader *shader, unsigned ucp_enables,
+                       bool use_clipdist_array);
 bool nir_lower_clip_cull_distance_arrays(nir_shader *nir);
 
 void nir_lower_point_size_mov(nir_shader *shader,

src/compiler/nir/nir_lower_clip.c

@@ -42,17 +42,23 @@
 
 static nir_variable *
 create_clipdist_var(nir_shader *shader, unsigned drvloc,
-                    bool output, gl_varying_slot slot)
+                    bool output, gl_varying_slot slot, unsigned array_size)
 {
    nir_variable *var = rzalloc(shader, nir_variable);
 
    var->data.driver_location = drvloc;
-   var->type = glsl_vec4_type();
    var->data.mode = output ? nir_var_shader_out : nir_var_shader_in;
    var->name = ralloc_asprintf(var, "clipdist_%d", drvloc);
    var->data.index = 0;
    var->data.location = slot;
 
+   if (array_size > 0) {
+      var->type = glsl_array_type(glsl_float_type(), array_size,
+                                  sizeof(float));
+      var->data.compact = 1;
+   } else
+      var->type = glsl_vec4_type();
+
    if (output) {
       exec_list_push_tail(&shader->outputs, &var->node);
       shader->num_outputs++; /* TODO use type_size() */
@@ -66,16 +72,24 @@ create_clipdist_var(nir_shader *shader, unsigned drvloc,
 
 static void
 create_clipdist_vars(nir_shader *shader, nir_variable **io_vars,
-                     unsigned ucp_enables, int *drvloc, bool output)
+                     unsigned ucp_enables, int *drvloc, bool output,
+                     bool use_clipdist_array)
 {
-   if (ucp_enables & 0x0f)
+   if (use_clipdist_array) {
       io_vars[0] =
-         create_clipdist_var(shader, ++(*drvloc), output,
-                             VARYING_SLOT_CLIP_DIST0);
-   if (ucp_enables & 0xf0)
-      io_vars[1] =
-         create_clipdist_var(shader, ++(*drvloc), output,
-                             VARYING_SLOT_CLIP_DIST1);
+         create_clipdist_var(shader, ++(*drvloc), true,
+                             VARYING_SLOT_CLIP_DIST0,
+                             util_last_bit(ucp_enables));
+   } else {
+      if (ucp_enables & 0x0f)
+         io_vars[0] =
+            create_clipdist_var(shader, ++(*drvloc), output,
+                                VARYING_SLOT_CLIP_DIST0, 0);
+      if (ucp_enables & 0xf0)
+         io_vars[1] =
+            create_clipdist_var(shader, ++(*drvloc), output,
+                                VARYING_SLOT_CLIP_DIST1, 0);
+   }
 }
 
 static void
@@ -192,7 +206,8 @@ find_clipvertex_and_position_outputs(nir_shader *shader,
 static void
 lower_clip_outputs(nir_builder *b, nir_variable *position,
                    nir_variable *clipvertex, nir_variable **out,
-                   unsigned ucp_enables, bool use_vars)
+                   unsigned ucp_enables, bool use_vars,
+                   bool use_clipdist_array)
 {
    nir_ssa_def *clipdist[MAX_CLIP_PLANES];
    nir_ssa_def *cv;
@@ -224,18 +239,28 @@ lower_clip_outputs(nir_builder *b, nir_variable *position,
          /* 0.0 == don't-clip == disabled: */
          clipdist[plane] = nir_imm_float(b, 0.0);
       }
+      if (use_clipdist_array && plane < util_last_bit(ucp_enables)) {
+         assert(use_vars);
+         nir_deref_instr *deref;
+         deref = nir_build_deref_array_imm(b,
+                                           nir_build_deref_var(b, out[0]),
+                                           plane);
+         nir_store_deref(b, deref, clipdist[plane], 1);
+      }
    }
 
-   if (use_vars) {
-      if (ucp_enables & 0x0f)
-         nir_store_var(b, out[0], nir_vec(b, clipdist, 4), 0xf);
-      if (ucp_enables & 0xf0)
-         nir_store_var(b, out[1], nir_vec(b, &clipdist[4], 4), 0xf);
-   } else {
-      if (ucp_enables & 0x0f)
-         store_clipdist_output(b, out[0], &clipdist[0]);
-      if (ucp_enables & 0xf0)
-         store_clipdist_output(b, out[1], &clipdist[4]);
+   if (!use_clipdist_array) {
+      if (use_vars) {
+         if (ucp_enables & 0x0f)
+            nir_store_var(b, out[0], nir_vec(b, clipdist, 4), 0xf);
+         if (ucp_enables & 0xf0)
+            nir_store_var(b, out[1], nir_vec(b, &clipdist[4], 4), 0xf);
+      } else {
+         if (ucp_enables & 0x0f)
+            store_clipdist_output(b, out[0], &clipdist[0]);
+         if (ucp_enables & 0xf0)
+            store_clipdist_output(b, out[1], &clipdist[4]);
+      }
    }
 }
 
@@ -248,9 +273,13 @@ lower_clip_outputs(nir_builder *b, nir_variable *position,
  *
  * If use_vars is true, the pass will use variable loads and stores instead
  * of working with store_output intrinsics.
+ *
+ * If use_clipdist_array is true, the pass will use compact arrays for the
+ * clipdist output instead of two vec4s.
  */
 bool
-nir_lower_clip_vs(nir_shader *shader, unsigned ucp_enables, bool use_vars)
+nir_lower_clip_vs(nir_shader *shader, unsigned ucp_enables, bool use_vars,
+                  bool use_clipdist_array)
 {
    nir_function_impl *impl = nir_shader_get_entrypoint(shader);
    nir_builder b;
@@ -281,9 +310,11 @@ nir_lower_clip_vs(nir_shader *shader, unsigned ucp_enables, bool use_vars)
       return false;
 
    /* insert CLIPDIST outputs */
-   create_clipdist_vars(shader, out, ucp_enables, &maxloc, true);
+   create_clipdist_vars(shader, out, ucp_enables, &maxloc, true,
+                        use_clipdist_array);
 
-   lower_clip_outputs(&b, position, clipvertex, out, ucp_enables, use_vars);
+   lower_clip_outputs(&b, position, clipvertex, out, ucp_enables, use_vars,
+                      use_clipdist_array);
 
    nir_metadata_preserve(impl, nir_metadata_dominance);
 
@@ -293,7 +324,7 @@ nir_lower_clip_vs(nir_shader *shader, unsigned ucp_enables, bool use_vars)
 static void
 lower_clip_in_gs_block(nir_builder *b, nir_block *block, nir_variable *position,
                        nir_variable *clipvertex, nir_variable **out,
-                       unsigned ucp_enables)
+                       unsigned ucp_enables, bool use_clipdist_array)
 {
    nir_foreach_instr_safe(instr, block) {
       if (instr->type != nir_instr_type_intrinsic)
@@ -304,7 +335,8 @@ lower_clip_in_gs_block(nir_builder *b, nir_block *block, nir_variable *position,
       case nir_intrinsic_emit_vertex_with_counter:
       case nir_intrinsic_emit_vertex:
          b->cursor = nir_before_instr(instr);
-         lower_clip_outputs(b, position, clipvertex, out, ucp_enables, true);
+         lower_clip_outputs(b, position, clipvertex, out, ucp_enables, true,
+                            use_clipdist_array);
          break;
       default:
          /* not interesting; skip this */
@@ -318,7 +350,8 @@ lower_clip_in_gs_block(nir_builder *b, nir_block *block, nir_variable *position,
  */
 
 bool
-nir_lower_clip_gs(nir_shader *shader, unsigned ucp_enables)
+nir_lower_clip_gs(nir_shader *shader, unsigned ucp_enables,
+                  bool use_clipdist_array)
 {
    nir_function_impl *impl = nir_shader_get_entrypoint(shader);
    nir_builder b;
@@ -335,12 +368,14 @@ nir_lower_clip_gs(nir_shader *shader, unsigned ucp_enables)
       return false;
 
    /* insert CLIPDIST outputs */
-   create_clipdist_vars(shader, out, ucp_enables, &maxloc, true);
+   create_clipdist_vars(shader, out, ucp_enables, &maxloc, true,
+                        use_clipdist_array);
 
    nir_builder_init(&b, impl);
 
    nir_foreach_block(block, impl)
-      lower_clip_in_gs_block(&b, block, position, clipvertex, out, ucp_enables);
+      lower_clip_in_gs_block(&b, block, position, clipvertex, out,
+                             ucp_enables, use_clipdist_array);
 
    nir_metadata_preserve(impl, nir_metadata_dominance);
 
@@ -388,7 +423,8 @@ lower_clip_fs(nir_function_impl *impl, unsigned ucp_enables,
 /* insert conditional kill based on interpolated CLIPDIST
  */
 bool
-nir_lower_clip_fs(nir_shader *shader, unsigned ucp_enables)
+nir_lower_clip_fs(nir_shader *shader, unsigned ucp_enables,
+                  bool use_clipdist_array)
 {
    nir_variable *in[2];
    int maxloc = -1;
@@ -410,7 +446,8 @@ nir_lower_clip_fs(nir_shader *shader, unsigned ucp_enables)
     * must add our own:
     */
    /* insert CLIPDIST inputs */
-   create_clipdist_vars(shader, in, ucp_enables, &maxloc, false);
+   create_clipdist_vars(shader, in, ucp_enables, &maxloc, false,
+                        use_clipdist_array);
 
    nir_foreach_function(function, shader) {
       if (!strcmp(function->name, "main"))

src/freedreno/ir3/ir3_nir.c

@@ -223,11 +223,11 @@ ir3_optimize_nir(struct ir3_shader *shader, nir_shader *s,
 
 	if (key) {
 		if (s->info.stage == MESA_SHADER_VERTEX) {
-			OPT_V(s, nir_lower_clip_vs, key->ucp_enables, false);
+			OPT_V(s, nir_lower_clip_vs, key->ucp_enables, false, false);
 			if (key->vclamp_color)
 				OPT_V(s, nir_lower_clamp_color_outputs);
 		} else if (s->info.stage == MESA_SHADER_FRAGMENT) {
-			OPT_V(s, nir_lower_clip_fs, key->ucp_enables);
+			OPT_V(s, nir_lower_clip_fs, key->ucp_enables, false);
 			if (key->fclamp_color)
 				OPT_V(s, nir_lower_clamp_color_outputs);
 		}

src/gallium/drivers/iris/iris_program.c

@@ -938,7 +938,8 @@ iris_compile_vs(struct iris_context *ice,
 
    if (key->nr_userclip_plane_consts) {
       nir_function_impl *impl = nir_shader_get_entrypoint(nir);
-      nir_lower_clip_vs(nir, (1 << key->nr_userclip_plane_consts) - 1, true);
+      nir_lower_clip_vs(nir, (1 << key->nr_userclip_plane_consts) - 1, true,
+                        false);
       nir_lower_io_to_temporaries(nir, impl, true, false);
       nir_lower_global_vars_to_local(nir);
       nir_lower_vars_to_ssa(nir);
@@ -1281,7 +1282,8 @@ iris_compile_tes(struct iris_context *ice,
 
    if (key->nr_userclip_plane_consts) {
       nir_function_impl *impl = nir_shader_get_entrypoint(nir);
-      nir_lower_clip_vs(nir, (1 << key->nr_userclip_plane_consts) - 1, true);
+      nir_lower_clip_vs(nir, (1 << key->nr_userclip_plane_consts) - 1, true,
+                        false);
       nir_lower_io_to_temporaries(nir, impl, true, false);
       nir_lower_global_vars_to_local(nir);
       nir_lower_vars_to_ssa(nir);
@@ -1401,7 +1403,7 @@ iris_compile_gs(struct iris_context *ice,
 
    if (key->nr_userclip_plane_consts) {
       nir_function_impl *impl = nir_shader_get_entrypoint(nir);
-      nir_lower_clip_gs(nir, (1 << key->nr_userclip_plane_consts) - 1);
+      nir_lower_clip_gs(nir, (1 << key->nr_userclip_plane_consts) - 1, false);
       nir_lower_io_to_temporaries(nir, impl, true, false);
       nir_lower_global_vars_to_local(nir);
       nir_lower_vars_to_ssa(nir);

src/gallium/drivers/vc4/vc4_program.c

@@ -2313,10 +2313,11 @@ vc4_shader_ntq(struct vc4_context *vc4, enum qstage stage,
 
         if (c->key->ucp_enables) {
                 if (stage == QSTAGE_FRAG) {
-                        NIR_PASS_V(c->s, nir_lower_clip_fs, c->key->ucp_enables);
+                        NIR_PASS_V(c->s, nir_lower_clip_fs,
+                                   c->key->ucp_enables, false);
                 } else {
                         NIR_PASS_V(c->s, nir_lower_clip_vs,
-				   c->key->ucp_enables, false);
+                                   c->key->ucp_enables, false, false);
                         NIR_PASS_V(c->s, nir_lower_io_to_scalar,
                                    nir_var_shader_out);
                 }

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

@@ -407,7 +407,7 @@ brw_nir_lower_legacy_clipping(nir_shader *nir, int nr_userclip_plane_consts,
 
    nir_function_impl *impl = nir_shader_get_entrypoint(nir);
 
-   nir_lower_clip_vs(nir, (1 << nr_userclip_plane_consts) - 1, true);
+   nir_lower_clip_vs(nir, (1 << nr_userclip_plane_consts) - 1, true, false);
    nir_lower_io_to_temporaries(nir, impl, true, false);
    nir_lower_global_vars_to_local(nir);
    nir_lower_vars_to_ssa(nir);