nir: Add a concept of per-member structs and a lowering pass

This adds a concept of "members" to a variable with an interface type.
It allows you to specify the full variable data for each member of the
interface instead of once for the variable.  We also add a lowering pass
to lower those variables to a sequence of variables and rewrite all the
derefs accordingly.

Acked-by: Rob Clark <robdclark@gmail.com>
Acked-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Acked-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/compiler/Makefile.sources

@@ -295,6 +295,7 @@ NIR_FILES = \
 	nir/nir_search_helpers.h \
 	nir/nir_serialize.c \
 	nir/nir_serialize.h \
+	nir/nir_split_per_member_structs.c \
 	nir/nir_split_var_copies.c \
 	nir/nir_sweep.c \
 	nir/nir_to_lcssa.c \

src/compiler/nir/meson.build

@@ -180,6 +180,7 @@ files_libnir = files(
   'nir_search_helpers.h',
   'nir_serialize.c',
   'nir_serialize.h',
+  'nir_split_per_member_structs.c',
   'nir_split_var_copies.c',
   'nir_sweep.c',
   'nir_to_lcssa.c',

src/compiler/nir/nir.h

@@ -370,6 +370,17 @@ typedef struct nir_variable {
     * \sa ir_variable::location
     */
    const struct glsl_type *interface_type;
+
+   /**
+    * Description of per-member data for per-member struct variables
+    *
+    * This is used for variables which are actually an amalgamation of
+    * multiple entities such as a struct of built-in values or a struct of
+    * inputs each with their own layout specifier.  This is only allowed on
+    * variables with a struct or array of array of struct type.
+    */
+   unsigned num_members;
+   struct nir_variable_data *members;
 } nir_variable;
 
 #define nir_foreach_variable(var, var_list) \
@@ -2678,6 +2689,7 @@ void nir_dump_cfg(nir_shader *shader, FILE *fp);
 int nir_gs_count_vertices(const nir_shader *shader);
 
 bool nir_split_var_copies(nir_shader *shader);
+bool nir_split_per_member_structs(nir_shader *shader);
 
 bool nir_lower_returns_impl(nir_function_impl *impl);
 bool nir_lower_returns(nir_shader *shader);

src/compiler/nir/nir_clone.c

@@ -161,6 +161,14 @@ nir_variable_clone(const nir_variable *var, nir_shader *shader)
    }
    nvar->interface_type = var->interface_type;
 
+   nvar->num_members = var->num_members;
+   if (var->num_members) {
+      nvar->members = ralloc_array(nvar, struct nir_variable_data,
+                                   var->num_members);
+      memcpy(nvar->members, var->members,
+             var->num_members * sizeof(*var->members));
+   }
+
    return nvar;
 }
 

src/compiler/nir/nir_serialize.c

@@ -149,6 +149,11 @@ write_variable(write_ctx *ctx, const nir_variable *var)
    blob_write_uint32(ctx->blob, !!(var->interface_type));
    if (var->interface_type)
       encode_type_to_blob(ctx->blob, var->interface_type);
+   blob_write_uint32(ctx->blob, var->num_members);
+   if (var->num_members > 0) {
+      blob_write_bytes(ctx->blob, (uint8_t *) var->members,
+                       var->num_members * sizeof(*var->members));
+   }
 }
 
 static nir_variable *
@@ -180,6 +185,13 @@ read_variable(read_ctx *ctx)
       var->interface_type = decode_type_from_blob(ctx->blob);
    else
       var->interface_type = NULL;
+   var->num_members = blob_read_uint32(ctx->blob);
+   if (var->num_members > 0) {
+      var->members = ralloc_array(var, struct nir_variable_data,
+                                  var->num_members);
+      blob_copy_bytes(ctx->blob, (uint8_t *) var->members,
+                      var->num_members * sizeof(*var->members));
+   }
 
    return var;
 }

src/compiler/nir/nir_split_per_member_structs.c

@@ -0,0 +1,290 @@
+/*
+ * Copyright © 2018 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "nir.h"
+#include "nir_deref.h"
+
+struct split_struct_state {
+   void *dead_ctx;
+
+   struct hash_table *var_to_member_map;
+};
+
+static nir_variable *
+find_var_member(struct nir_variable *var, unsigned member,
+                struct hash_table *var_to_member_map)
+{
+   struct hash_entry *map_entry =
+      _mesa_hash_table_search(var_to_member_map, var);
+   if (map_entry == NULL)
+      return NULL;
+
+   nir_variable **members = map_entry->data;
+   assert(member < var->num_members);
+   return members[member];
+}
+
+static const struct glsl_type *
+member_type(const struct glsl_type *type, unsigned index)
+{
+   if (glsl_type_is_array(type)) {
+      const struct glsl_type *elem =
+         member_type(glsl_get_array_element(type), index);
+      return glsl_get_array_instance(elem, glsl_get_length(type));
+   } else {
+      assert(glsl_type_is_struct(type));
+      assert(index < glsl_get_length(type));
+      return glsl_get_struct_field(type, index);
+   }
+}
+
+static void
+split_variable(struct nir_variable *var, nir_shader *shader,
+               struct hash_table *var_to_member_map, void *dead_ctx)
+{
+   assert(var->state_slots == NULL);
+
+   /* Constant initializers are currently not handled */
+   assert(var->constant_initializer == NULL);
+
+   nir_variable **members =
+      ralloc_array(dead_ctx, nir_variable *, var->num_members);
+
+   for (unsigned i = 0; i < var->num_members; i++) {
+      char *member_name = NULL;
+      if (var->name) {
+         /* Calculate a reasonable variable name */
+         member_name = ralloc_strdup(dead_ctx, var->name);
+         const struct glsl_type *t = var->type;
+         while (glsl_type_is_array(t)) {
+            ralloc_strcat(&member_name, "[*]");
+            t = glsl_get_array_element(t);
+         }
+         const char *field_name = glsl_get_struct_elem_name(t, i);
+         if (field_name) {
+            member_name = ralloc_asprintf(dead_ctx, "%s.%s",
+                                          member_name, field_name);
+         } else {
+            member_name = ralloc_asprintf(dead_ctx, "%s.@%d", member_name, i);
+         }
+      }
+
+      members[i] =
+         nir_variable_create(shader, var->members[i].mode,
+                             member_type(var->type, i), member_name);
+      if (var->interface_type) {
+         members[i]->interface_type =
+            glsl_get_struct_field(var->interface_type, i);
+      }
+      members[i]->data = var->members[i];
+   }
+
+   _mesa_hash_table_insert(var_to_member_map, var, members);
+}
+
+static bool
+split_variables_in_list(struct exec_list *var_list, nir_shader *shader,
+                        struct hash_table *var_to_member_map, void *dead_ctx)
+{
+   bool progress = false;
+
+   nir_foreach_variable_safe(var, var_list) {
+      if (var->num_members == 0)
+         continue;
+
+      split_variable(var, shader, var_to_member_map, dead_ctx);
+      exec_node_remove(&var->node);
+      progress = true;
+   }
+
+   return progress;
+}
+
+static nir_deref_instr *
+build_member_deref(nir_builder *b, nir_deref_instr *deref, nir_variable *member)
+{
+   if (deref->deref_type == nir_deref_type_var) {
+      return nir_build_deref_var(b, member);
+   } else {
+      nir_deref_instr *parent =
+         build_member_deref(b, nir_deref_instr_parent(deref), member);
+      return nir_build_deref_follower(b, parent, deref);
+   }
+}
+
+static void
+rewrite_deref_instr(nir_builder *b, nir_deref_instr *deref,
+                    struct hash_table *var_to_member_map)
+{
+   /* We must be a struct deref */
+   if (deref->deref_type != nir_deref_type_struct)
+      return;
+
+   nir_deref_instr *base;
+   for (base = nir_deref_instr_parent(deref);
+        base && base->deref_type != nir_deref_type_var;
+        base = nir_deref_instr_parent(base)) {
+
+      /* If this struct is nested inside another, bail */
+      if (base->deref_type == nir_deref_type_struct)
+         return;
+   }
+
+   /* We must be on a variable with members */
+   if (!base || base->var->num_members == 0)
+      return;
+
+   nir_variable *member = find_var_member(base->var, deref->strct.index,
+                                          var_to_member_map);
+   assert(member);
+
+   b->cursor = nir_before_instr(&deref->instr);
+   nir_deref_instr *member_deref =
+      build_member_deref(b, nir_deref_instr_parent(deref), member);
+   nir_ssa_def_rewrite_uses(&deref->dest.ssa,
+                            nir_src_for_ssa(&member_deref->dest.ssa));
+
+   /* The referenced variable is no longer valid, clean up the deref */
+   nir_deref_instr_remove_if_unused(deref);
+}
+
+static void
+rewrite_deref_var(nir_instr *instr, nir_deref_var **deref,
+                 struct hash_table *var_to_member_map)
+{
+   if ((*deref)->var->members == 0)
+      return;
+
+   nir_deref_struct *strct = NULL;
+   for (nir_deref *d = (*deref)->deref.child; d; d = d->child) {
+      if (d->deref_type == nir_deref_type_struct) {
+         strct = nir_deref_as_struct(d);
+         break;
+      }
+   }
+   assert(strct);
+
+   nir_variable *member = find_var_member((*deref)->var, strct->index,
+                                          var_to_member_map);
+
+   nir_deref_var *head = nir_deref_var_create(ralloc_parent(*deref), member);
+   nir_deref *tail = &head->deref;
+   for (nir_deref *d = (*deref)->deref.child;
+        d != &strct->deref; d = d->child) {
+      nir_deref_array *arr = nir_deref_as_array(d);
+
+      nir_deref_array *narr = nir_deref_array_create(tail);
+      narr->deref.type = glsl_get_array_element(tail->type);
+      narr->deref_array_type = arr->deref_array_type;
+      narr->base_offset = arr->base_offset;
+
+      if (arr->deref_array_type == nir_deref_array_type_indirect)
+         nir_instr_move_src(instr, &narr->indirect, &arr->indirect);
+
+      assert(tail->child == NULL);
+      tail->child = &narr->deref;
+      tail = &narr->deref;
+   }
+
+   ralloc_steal(tail, strct->deref.child);
+   tail->child = strct->deref.child;
+
+   ralloc_free(*deref);
+   *deref = head;
+}
+
+static void
+rewrite_intrinsic_instr(nir_intrinsic_instr *intrin,
+                        struct hash_table *var_to_member_map)
+{
+   for (unsigned i = 0;
+        i < nir_intrinsic_infos[intrin->intrinsic].num_variables; i++) {
+      rewrite_deref_var(&intrin->instr, &intrin->variables[i],
+                        var_to_member_map);
+   }
+}
+
+static void
+rewrite_tex_instr(nir_tex_instr *tex, struct hash_table *var_to_member_map)
+{
+   if (tex->texture)
+      rewrite_deref_var(&tex->instr, &tex->texture, var_to_member_map);
+   if (tex->sampler)
+      rewrite_deref_var(&tex->instr, &tex->sampler, var_to_member_map);
+}
+
+bool
+nir_split_per_member_structs(nir_shader *shader)
+{
+   bool progress = false;
+   void *dead_ctx = ralloc_context(NULL);
+   struct hash_table *var_to_member_map =
+      _mesa_hash_table_create(dead_ctx, _mesa_hash_pointer,
+                              _mesa_key_pointer_equal);
+
+   progress |= split_variables_in_list(&shader->inputs, shader,
+                                       var_to_member_map, dead_ctx);
+   progress |= split_variables_in_list(&shader->outputs, shader,
+                                       var_to_member_map, dead_ctx);
+   progress |= split_variables_in_list(&shader->system_values, shader,
+                                       var_to_member_map, dead_ctx);
+   if (!progress)
+      return false;
+
+   nir_foreach_function(function, shader) {
+      if (!function->impl)
+         continue;
+
+      nir_builder b;
+      nir_builder_init(&b, function->impl);
+      nir_foreach_block(block, function->impl) {
+         nir_foreach_instr_safe(instr, block) {
+            switch (instr->type) {
+            case nir_instr_type_deref:
+               rewrite_deref_instr(&b, nir_instr_as_deref(instr),
+                                   var_to_member_map);
+               break;
+
+            case nir_instr_type_intrinsic:
+               rewrite_intrinsic_instr(nir_instr_as_intrinsic(instr),
+                                       var_to_member_map);
+               break;
+
+            case nir_instr_type_tex:
+               rewrite_tex_instr(nir_instr_as_tex(instr), var_to_member_map);
+               break;
+
+            case nir_instr_type_call:
+               unreachable("Functions must be inlined before this pass");
+
+            default:
+               break;
+            }
+         }
+      }
+   }
+
+   ralloc_free(dead_ctx);
+
+   return progress;
+}

src/compiler/nir/nir_validate.c

@@ -1100,6 +1100,13 @@ validate_var_decl(nir_variable *var, bool is_global, validate_state *state)
       }
    }
 
+   if (var->num_members > 0) {
+      const struct glsl_type *without_array = glsl_without_array(var->type);
+      validate_assert(state, glsl_type_is_struct(without_array));
+      validate_assert(state, var->num_members == glsl_get_length(without_array));
+      validate_assert(state, var->members != NULL);
+   }
+
    /*
     * TODO validate some things ir_validate.cpp does (requires more GLSL type
     * support)