glsl/linker: check for xfb_offset aliasing
[mesa.git] / src / compiler / glsl / link_varyings.cpp
index e6947692affd2a5e5bc349733c883b6f0ce8cf29..4e00840c53e84b77c76d6e623ff072c3a7f76c3a 100644 (file)
@@ -29,6 +29,7 @@
  */
 
 
+#include "main/errors.h"
 #include "main/mtypes.h"
 #include "glsl_symbol_table.h"
 #include "glsl_parser_extras.h"
@@ -37,6 +38,7 @@
 #include "link_varyings.h"
 #include "main/macros.h"
 #include "util/hash_table.h"
+#include "util/u_math.h"
 #include "program.h"
 
 
@@ -77,7 +79,7 @@ create_xfb_varying_names(void *mem_ctx, const glsl_type *t, char **name,
 
       create_xfb_varying_names(mem_ctx, ifc_member_t, name, new_length, count,
                                NULL, NULL, varying_names);
-   } else if (t->is_record()) {
+   } else if (t->is_struct()) {
       for (unsigned i = 0; i < t->length; i++) {
          const char *field = t->fields.structure[i].name;
          size_t new_length = name_length;
@@ -88,7 +90,7 @@ create_xfb_varying_names(void *mem_ctx, const glsl_type *t, char **name,
                                   new_length, count, NULL, NULL,
                                   varying_names);
       }
-   } else if (t->without_array()->is_record() ||
+   } else if (t->without_array()->is_struct() ||
               t->without_array()->is_interface() ||
               (t->is_array() && t->fields.array->is_array())) {
       for (unsigned i = 0; i < t->length; i++) {
@@ -165,10 +167,12 @@ process_xfb_layout_qualifiers(void *mem_ctx, const gl_linked_shader *sh,
 
          if (var->data.from_named_ifc_block) {
             type = var->get_interface_type();
+
             /* Find the member type before it was altered by lowering */
+            const glsl_type *type_wa = type->without_array();
             member_type =
-               type->fields.structure[type->field_index(var->name)].type;
-            name = ralloc_strdup(NULL, type->without_array()->name);
+               type_wa->fields.structure[type_wa->field_index(var->name)].type;
+            name = ralloc_strdup(NULL, type_wa->name);
          } else {
             type = var->type;
             member_type = NULL;
@@ -184,31 +188,13 @@ process_xfb_layout_qualifiers(void *mem_ctx, const gl_linked_shader *sh,
    return has_xfb_qualifiers;
 }
 
-static bool
-anonymous_struct_type_matches(const glsl_type *output_type,
-                              const glsl_type *to_match)
-{
-    while (output_type->is_array() && to_match->is_array()) {
-        /* if the lengths at each level don't match fail. */
-        if (output_type->length != to_match->length)
-            return false;
-        output_type = output_type->fields.array;
-        to_match = to_match->fields.array;
-    }
-
-    if (output_type->is_array() || to_match->is_array())
-        return false;
-    return output_type->is_anonymous() &&
-           to_match->is_anonymous() &&
-           to_match->record_compare(output_type);
-}
-
 /**
  * Validate the types and qualifiers of an output from one stage against the
  * matching input to another stage.
  */
 static void
-cross_validate_types_and_qualifiers(struct gl_shader_program *prog,
+cross_validate_types_and_qualifiers(struct gl_context *ctx,
+                                    struct gl_shader_program *prog,
                                     const ir_variable *input,
                                     const ir_variable *output,
                                     gl_shader_stage consumer_stage,
@@ -228,38 +214,51 @@ cross_validate_types_and_qualifiers(struct gl_shader_program *prog,
    }
 
    if (type_to_match != output->type) {
-      /* There is a bit of a special case for gl_TexCoord.  This
-       * built-in is unsized by default.  Applications that variable
-       * access it must redeclare it with a size.  There is some
-       * language in the GLSL spec that implies the fragment shader
-       * and vertex shader do not have to agree on this size.  Other
-       * driver behave this way, and one or two applications seem to
-       * rely on it.
-       *
-       * Neither declaration needs to be modified here because the array
-       * sizes are fixed later when update_array_sizes is called.
-       *
-       * From page 48 (page 54 of the PDF) of the GLSL 1.10 spec:
-       *
-       *     "Unlike user-defined varying variables, the built-in
-       *     varying variables don't have a strict one-to-one
-       *     correspondence between the vertex language and the
-       *     fragment language."
-       */
-      if (!output->type->is_array() || !is_gl_identifier(output->name)) {
-         bool anon_matches = anonymous_struct_type_matches(output->type, type_to_match);
-
-         if (!anon_matches) {
+      if (output->type->is_struct()) {
+         /* Structures across shader stages can have different name
+          * and considered to match in type if and only if structure
+          * members match in name, type, qualification, and declaration
+          * order.
+          */
+         if (!output->type->record_compare(type_to_match, false, true)) {
             linker_error(prog,
-                         "%s shader output `%s' declared as type `%s', "
-                         "but %s shader input declared as type `%s'\n",
-                         _mesa_shader_stage_to_string(producer_stage),
-                         output->name,
-                         output->type->name,
-                         _mesa_shader_stage_to_string(consumer_stage),
-                         input->type->name);
-            return;
+                  "%s shader output `%s' declared as struct `%s', "
+                  "doesn't match in type with %s shader input "
+                  "declared as struct `%s'\n",
+                  _mesa_shader_stage_to_string(producer_stage),
+                  output->name,
+                  output->type->name,
+                  _mesa_shader_stage_to_string(consumer_stage),
+                  input->type->name);
          }
+      } else if (!output->type->is_array() || !is_gl_identifier(output->name)) {
+         /* There is a bit of a special case for gl_TexCoord.  This
+          * built-in is unsized by default.  Applications that variable
+          * access it must redeclare it with a size.  There is some
+          * language in the GLSL spec that implies the fragment shader
+          * and vertex shader do not have to agree on this size.  Other
+          * driver behave this way, and one or two applications seem to
+          * rely on it.
+          *
+          * Neither declaration needs to be modified here because the array
+          * sizes are fixed later when update_array_sizes is called.
+          *
+          * From page 48 (page 54 of the PDF) of the GLSL 1.10 spec:
+          *
+          *     "Unlike user-defined varying variables, the built-in
+          *     varying variables don't have a strict one-to-one
+          *     correspondence between the vertex language and the
+          *     fragment language."
+          */
+         linker_error(prog,
+                      "%s shader output `%s' declared as type `%s', "
+                      "but %s shader input declared as type `%s'\n",
+                      _mesa_shader_stage_to_string(producer_stage),
+                      output->name,
+                      output->type->name,
+                      _mesa_shader_stage_to_string(consumer_stage),
+                      input->type->name);
+         return;
       }
    }
 
@@ -327,16 +326,16 @@ cross_validate_types_and_qualifiers(struct gl_shader_program *prog,
     *    "The invariance of varyings that are declared in both the vertex
     *     and fragment shaders must match."
     */
-   if (input->data.invariant != output->data.invariant &&
+   if (input->data.explicit_invariant != output->data.explicit_invariant &&
        prog->data->Version < (prog->IsES ? 300 : 430)) {
       linker_error(prog,
                    "%s shader output `%s' %s invariant qualifier, "
                    "but %s shader input %s invariant qualifier\n",
                    _mesa_shader_stage_to_string(producer_stage),
                    output->name,
-                   (output->data.invariant) ? "has" : "lacks",
+                   (output->data.explicit_invariant) ? "has" : "lacks",
                    _mesa_shader_stage_to_string(consumer_stage),
-                   (input->data.invariant) ? "has" : "lacks");
+                   (input->data.explicit_invariant) ? "has" : "lacks");
       return;
    }
 
@@ -348,20 +347,48 @@ cross_validate_types_and_qualifiers(struct gl_shader_program *prog,
     *     "It is a link-time error if, within the same stage, the interpolation
     *     qualifiers of variables of the same name do not match.
     *
+    * Section 4.3.9 (Interpolation) of the GLSL ES 3.00 spec says:
+    *
+    *    "When no interpolation qualifier is present, smooth interpolation
+    *    is used."
+    *
+    * So we match variables where one is smooth and the other has no explicit
+    * qualifier.
     */
-   if (input->data.interpolation != output->data.interpolation &&
+   unsigned input_interpolation = input->data.interpolation;
+   unsigned output_interpolation = output->data.interpolation;
+   if (prog->IsES) {
+      if (input_interpolation == INTERP_MODE_NONE)
+         input_interpolation = INTERP_MODE_SMOOTH;
+      if (output_interpolation == INTERP_MODE_NONE)
+         output_interpolation = INTERP_MODE_SMOOTH;
+   }
+   if (input_interpolation != output_interpolation &&
        prog->data->Version < 440) {
-      linker_error(prog,
-                   "%s shader output `%s' specifies %s "
-                   "interpolation qualifier, "
-                   "but %s shader input specifies %s "
-                   "interpolation qualifier\n",
-                   _mesa_shader_stage_to_string(producer_stage),
-                   output->name,
-                   interpolation_string(output->data.interpolation),
-                   _mesa_shader_stage_to_string(consumer_stage),
-                   interpolation_string(input->data.interpolation));
-      return;
+      if (!ctx->Const.AllowGLSLCrossStageInterpolationMismatch) {
+         linker_error(prog,
+                      "%s shader output `%s' specifies %s "
+                      "interpolation qualifier, "
+                      "but %s shader input specifies %s "
+                      "interpolation qualifier\n",
+                      _mesa_shader_stage_to_string(producer_stage),
+                      output->name,
+                      interpolation_string(output->data.interpolation),
+                      _mesa_shader_stage_to_string(consumer_stage),
+                      interpolation_string(input->data.interpolation));
+         return;
+      } else {
+         linker_warning(prog,
+                        "%s shader output `%s' specifies %s "
+                        "interpolation qualifier, "
+                        "but %s shader input specifies %s "
+                        "interpolation qualifier\n",
+                        _mesa_shader_stage_to_string(producer_stage),
+                        output->name,
+                        interpolation_string(output->data.interpolation),
+                        _mesa_shader_stage_to_string(consumer_stage),
+                        interpolation_string(input->data.interpolation));
+      }
    }
 }
 
@@ -369,7 +396,8 @@ cross_validate_types_and_qualifiers(struct gl_shader_program *prog,
  * Validate front and back color outputs against single color input
  */
 static void
-cross_validate_front_and_back_color(struct gl_shader_program *prog,
+cross_validate_front_and_back_color(struct gl_context *ctx,
+                                    struct gl_shader_program *prog,
                                     const ir_variable *input,
                                     const ir_variable *front_color,
                                     const ir_variable *back_color,
@@ -377,25 +405,342 @@ cross_validate_front_and_back_color(struct gl_shader_program *prog,
                                     gl_shader_stage producer_stage)
 {
    if (front_color != NULL && front_color->data.assigned)
-      cross_validate_types_and_qualifiers(prog, input, front_color,
+      cross_validate_types_and_qualifiers(ctx, prog, input, front_color,
                                           consumer_stage, producer_stage);
 
    if (back_color != NULL && back_color->data.assigned)
-      cross_validate_types_and_qualifiers(prog, input, back_color,
+      cross_validate_types_and_qualifiers(ctx, prog, input, back_color,
                                           consumer_stage, producer_stage);
 }
 
+static unsigned
+compute_variable_location_slot(ir_variable *var, gl_shader_stage stage)
+{
+   unsigned location_start = VARYING_SLOT_VAR0;
+
+   switch (stage) {
+      case MESA_SHADER_VERTEX:
+         if (var->data.mode == ir_var_shader_in)
+            location_start = VERT_ATTRIB_GENERIC0;
+         break;
+      case MESA_SHADER_TESS_CTRL:
+      case MESA_SHADER_TESS_EVAL:
+         if (var->data.patch)
+            location_start = VARYING_SLOT_PATCH0;
+         break;
+      case MESA_SHADER_FRAGMENT:
+         if (var->data.mode == ir_var_shader_out)
+            location_start = FRAG_RESULT_DATA0;
+         break;
+      default:
+         break;
+   }
+
+   return var->data.location - location_start;
+}
+
+struct explicit_location_info {
+   ir_variable *var;
+   bool base_type_is_integer;
+   unsigned base_type_bit_size;
+   unsigned interpolation;
+   bool centroid;
+   bool sample;
+   bool patch;
+};
+
+static bool
+check_location_aliasing(struct explicit_location_info explicit_locations[][4],
+                        ir_variable *var,
+                        unsigned location,
+                        unsigned component,
+                        unsigned location_limit,
+                        const glsl_type *type,
+                        unsigned interpolation,
+                        bool centroid,
+                        bool sample,
+                        bool patch,
+                        gl_shader_program *prog,
+                        gl_shader_stage stage)
+{
+   unsigned last_comp;
+   unsigned base_type_bit_size;
+   const glsl_type *type_without_array = type->without_array();
+   const bool base_type_is_integer =
+      glsl_base_type_is_integer(type_without_array->base_type);
+   const bool is_struct = type_without_array->is_struct();
+   if (is_struct) {
+      /* structs don't have a defined underlying base type so just treat all
+       * component slots as used and set the bit size to 0. If there is
+       * location aliasing, we'll fail anyway later.
+       */
+      last_comp = 4;
+      base_type_bit_size = 0;
+   } else {
+      unsigned dmul = type_without_array->is_64bit() ? 2 : 1;
+      last_comp = component + type_without_array->vector_elements * dmul;
+      base_type_bit_size =
+         glsl_base_type_get_bit_size(type_without_array->base_type);
+   }
+
+   while (location < location_limit) {
+      unsigned comp = 0;
+      while (comp < 4) {
+         struct explicit_location_info *info =
+            &explicit_locations[location][comp];
+
+         if (info->var) {
+            if (info->var->type->without_array()->is_struct() || is_struct) {
+               /* Structs cannot share location since they are incompatible
+                * with any other underlying numerical type.
+                */
+               linker_error(prog,
+                            "%s shader has multiple %sputs sharing the "
+                            "same location that don't have the same "
+                            "underlying numerical type. Struct variable '%s', "
+                            "location %u\n",
+                            _mesa_shader_stage_to_string(stage),
+                            var->data.mode == ir_var_shader_in ? "in" : "out",
+                            is_struct ? var->name : info->var->name,
+                            location);
+               return false;
+            } else if (comp >= component && comp < last_comp) {
+               /* Component aliasing is not allowed */
+               linker_error(prog,
+                            "%s shader has multiple %sputs explicitly "
+                            "assigned to location %d and component %d\n",
+                            _mesa_shader_stage_to_string(stage),
+                            var->data.mode == ir_var_shader_in ? "in" : "out",
+                            location, comp);
+               return false;
+            } else {
+               /* From the OpenGL 4.60.5 spec, section 4.4.1 Input Layout
+                * Qualifiers, Page 67, (Location aliasing):
+                *
+                *   " Further, when location aliasing, the aliases sharing the
+                *     location must have the same underlying numerical type
+                *     and bit width (floating-point or integer, 32-bit versus
+                *     64-bit, etc.) and the same auxiliary storage and
+                *     interpolation qualification."
+                */
+
+               /* If the underlying numerical type isn't integer, implicitly
+                * it will be float or else we would have failed by now.
+                */
+               if (info->base_type_is_integer != base_type_is_integer) {
+                  linker_error(prog,
+                               "%s shader has multiple %sputs sharing the "
+                               "same location that don't have the same "
+                               "underlying numerical type. Location %u "
+                               "component %u.\n",
+                               _mesa_shader_stage_to_string(stage),
+                               var->data.mode == ir_var_shader_in ?
+                               "in" : "out", location, comp);
+                  return false;
+               }
+
+               if (info->base_type_bit_size != base_type_bit_size) {
+                  linker_error(prog,
+                               "%s shader has multiple %sputs sharing the "
+                               "same location that don't have the same "
+                               "underlying numerical bit size. Location %u "
+                               "component %u.\n",
+                               _mesa_shader_stage_to_string(stage),
+                               var->data.mode == ir_var_shader_in ?
+                               "in" : "out", location, comp);
+                  return false;
+               }
+
+               if (info->interpolation != interpolation) {
+                  linker_error(prog,
+                               "%s shader has multiple %sputs sharing the "
+                               "same location that don't have the same "
+                               "interpolation qualification. Location %u "
+                               "component %u.\n",
+                               _mesa_shader_stage_to_string(stage),
+                               var->data.mode == ir_var_shader_in ?
+                               "in" : "out", location, comp);
+                  return false;
+               }
+
+               if (info->centroid != centroid ||
+                   info->sample != sample ||
+                   info->patch != patch) {
+                  linker_error(prog,
+                               "%s shader has multiple %sputs sharing the "
+                               "same location that don't have the same "
+                               "auxiliary storage qualification. Location %u "
+                               "component %u.\n",
+                               _mesa_shader_stage_to_string(stage),
+                               var->data.mode == ir_var_shader_in ?
+                               "in" : "out", location, comp);
+                  return false;
+               }
+            }
+         } else if (comp >= component && comp < last_comp) {
+            info->var = var;
+            info->base_type_is_integer = base_type_is_integer;
+            info->base_type_bit_size = base_type_bit_size;
+            info->interpolation = interpolation;
+            info->centroid = centroid;
+            info->sample = sample;
+            info->patch = patch;
+         }
+
+         comp++;
+
+         /* We need to do some special handling for doubles as dvec3 and
+          * dvec4 consume two consecutive locations. We don't need to
+          * worry about components beginning at anything other than 0 as
+          * the spec does not allow this for dvec3 and dvec4.
+          */
+         if (comp == 4 && last_comp > 4) {
+            last_comp = last_comp - 4;
+            /* Bump location index and reset the component index */
+            location++;
+            comp = 0;
+            component = 0;
+         }
+      }
+
+      location++;
+   }
+
+   return true;
+}
+
+static bool
+validate_explicit_variable_location(struct gl_context *ctx,
+                                    struct explicit_location_info explicit_locations[][4],
+                                    ir_variable *var,
+                                    gl_shader_program *prog,
+                                    gl_linked_shader *sh)
+{
+   const glsl_type *type = get_varying_type(var, sh->Stage);
+   unsigned num_elements = type->count_attribute_slots(false);
+   unsigned idx = compute_variable_location_slot(var, sh->Stage);
+   unsigned slot_limit = idx + num_elements;
+
+   /* Vertex shader inputs and fragment shader outputs are validated in
+    * assign_attribute_or_color_locations() so we should not attempt to
+    * validate them again here.
+    */
+   unsigned slot_max;
+   if (var->data.mode == ir_var_shader_out) {
+      assert(sh->Stage != MESA_SHADER_FRAGMENT);
+      slot_max =
+         ctx->Const.Program[sh->Stage].MaxOutputComponents / 4;
+   } else {
+      assert(var->data.mode == ir_var_shader_in);
+      assert(sh->Stage != MESA_SHADER_VERTEX);
+      slot_max =
+         ctx->Const.Program[sh->Stage].MaxInputComponents / 4;
+   }
+
+   if (slot_limit > slot_max) {
+      linker_error(prog,
+                   "Invalid location %u in %s shader\n",
+                   idx, _mesa_shader_stage_to_string(sh->Stage));
+      return false;
+   }
+
+   const glsl_type *type_without_array = type->without_array();
+   if (type_without_array->is_interface()) {
+      for (unsigned i = 0; i < type_without_array->length; i++) {
+         glsl_struct_field *field = &type_without_array->fields.structure[i];
+         unsigned field_location = field->location -
+            (field->patch ? VARYING_SLOT_PATCH0 : VARYING_SLOT_VAR0);
+         if (!check_location_aliasing(explicit_locations, var,
+                                      field_location,
+                                      0, field_location + 1,
+                                      field->type,
+                                      field->interpolation,
+                                      field->centroid,
+                                      field->sample,
+                                      field->patch,
+                                      prog, sh->Stage)) {
+            return false;
+         }
+      }
+   } else if (!check_location_aliasing(explicit_locations, var,
+                                       idx, var->data.location_frac,
+                                       slot_limit, type,
+                                       var->data.interpolation,
+                                       var->data.centroid,
+                                       var->data.sample,
+                                       var->data.patch,
+                                       prog, sh->Stage)) {
+      return false;
+   }
+
+   return true;
+}
+
+/**
+ * Validate explicit locations for the inputs to the first stage and the
+ * outputs of the last stage in a program, if those are not the VS and FS
+ * shaders.
+ */
+void
+validate_first_and_last_interface_explicit_locations(struct gl_context *ctx,
+                                                     struct gl_shader_program *prog,
+                                                     gl_shader_stage first_stage,
+                                                     gl_shader_stage last_stage)
+{
+   /* VS inputs and FS outputs are validated in
+    * assign_attribute_or_color_locations()
+    */
+   bool validate_first_stage = first_stage != MESA_SHADER_VERTEX;
+   bool validate_last_stage = last_stage != MESA_SHADER_FRAGMENT;
+   if (!validate_first_stage && !validate_last_stage)
+      return;
+
+   struct explicit_location_info explicit_locations[MAX_VARYING][4];
+
+   gl_shader_stage stages[2] = { first_stage, last_stage };
+   bool validate_stage[2] = { validate_first_stage, validate_last_stage };
+   ir_variable_mode var_direction[2] = { ir_var_shader_in, ir_var_shader_out };
+
+   for (unsigned i = 0; i < 2; i++) {
+      if (!validate_stage[i])
+         continue;
+
+      gl_shader_stage stage = stages[i];
+
+      gl_linked_shader *sh = prog->_LinkedShaders[stage];
+      assert(sh);
+
+      memset(explicit_locations, 0, sizeof(explicit_locations));
+
+      foreach_in_list(ir_instruction, node, sh->ir) {
+         ir_variable *const var = node->as_variable();
+
+         if (var == NULL ||
+             !var->data.explicit_location ||
+             var->data.location < VARYING_SLOT_VAR0 ||
+             var->data.mode != var_direction[i])
+            continue;
+
+         if (!validate_explicit_variable_location(
+               ctx, explicit_locations, var, prog, sh)) {
+            return;
+         }
+      }
+   }
+}
+
 /**
  * Validate that outputs from one stage match inputs of another
  */
 void
-cross_validate_outputs_to_inputs(struct gl_shader_program *prog,
+cross_validate_outputs_to_inputs(struct gl_context *ctx,
+                                 struct gl_shader_program *prog,
                                  gl_linked_shader *producer,
                                  gl_linked_shader *consumer)
 {
    glsl_symbol_table parameters;
-   ir_variable *explicit_locations[MAX_VARYINGS_INCL_PATCH][4] =
-      { {NULL, NULL} };
+   struct explicit_location_info output_explicit_locations[MAX_VARYING][4] = {};
+   struct explicit_location_info input_explicit_locations[MAX_VARYING][4] = {};
 
    /* Find all shader outputs in the "producer" stage.
     */
@@ -412,66 +757,10 @@ cross_validate_outputs_to_inputs(struct gl_shader_program *prog,
          /* User-defined varyings with explicit locations are handled
           * differently because they do not need to have matching names.
           */
-         const glsl_type *type = get_varying_type(var, producer->Stage);
-         unsigned num_elements = type->count_attribute_slots(false);
-         unsigned idx = var->data.location - VARYING_SLOT_VAR0;
-         unsigned slot_limit = idx + num_elements;
-         unsigned last_comp;
-
-         if (type->without_array()->is_record()) {
-            /* The component qualifier can't be used on structs so just treat
-             * all component slots as used.
-             */
-            last_comp = 4;
-         } else {
-            unsigned dmul = type->without_array()->is_64bit() ? 2 : 1;
-            last_comp = var->data.location_frac +
-               type->without_array()->vector_elements * dmul;
-         }
-
-         while (idx < slot_limit) {
-            unsigned i = var->data.location_frac;
-            while (i < last_comp) {
-               if (explicit_locations[idx][i] != NULL) {
-                  linker_error(prog,
-                               "%s shader has multiple outputs explicitly "
-                               "assigned to location %d and component %d\n",
-                               _mesa_shader_stage_to_string(producer->Stage),
-                               idx, var->data.location_frac);
-                  return;
-               }
-
-               /* Make sure all component at this location have the same type.
-                */
-               for (unsigned j = 0; j < 4; j++) {
-                  if (explicit_locations[idx][j] &&
-                      (explicit_locations[idx][j]->type->without_array()
-                       ->base_type != type->without_array()->base_type)) {
-                     linker_error(prog,
-                                  "Varyings sharing the same location must "
-                                  "have the same underlying numerical type. "
-                                  "Location %u component %u\n", idx,
-                                  var->data.location_frac);
-                     return;
-                  }
-               }
-
-               explicit_locations[idx][i] = var;
-               i++;
-
-               /* We need to do some special handling for doubles as dvec3 and
-                * dvec4 consume two consecutive locations. We don't need to
-                * worry about components beginning at anything other than 0 as
-                * the spec does not allow this for dvec3 and dvec4.
-                */
-               if (i == 4 && last_comp > 4) {
-                  last_comp = last_comp - 4;
-                  /* Bump location index and reset the component index */
-                  idx++;
-                  i = 0;
-               }
-            }
-            idx++;
+         if (!validate_explicit_variable_location(ctx,
+                                                  output_explicit_locations,
+                                                  var, prog, producer)) {
+            return;
          }
       }
    }
@@ -498,7 +787,7 @@ cross_validate_outputs_to_inputs(struct gl_shader_program *prog,
          const ir_variable *const back_color =
             parameters.get_variable("gl_BackColor");
 
-         cross_validate_front_and_back_color(prog, input,
+         cross_validate_front_and_back_color(ctx, prog, input,
                                              front_color, back_color,
                                              consumer->Stage, producer->Stage);
       } else if (strcmp(input->name, "gl_SecondaryColor") == 0 && input->data.used) {
@@ -508,7 +797,7 @@ cross_validate_outputs_to_inputs(struct gl_shader_program *prog,
          const ir_variable *const back_color =
             parameters.get_variable("gl_BackSecondaryColor");
 
-         cross_validate_front_and_back_color(prog, input,
+         cross_validate_front_and_back_color(ctx, prog, input,
                                              front_color, back_color,
                                              consumer->Stage, producer->Stage);
       } else {
@@ -523,14 +812,40 @@ cross_validate_outputs_to_inputs(struct gl_shader_program *prog,
 
             const glsl_type *type = get_varying_type(input, consumer->Stage);
             unsigned num_elements = type->count_attribute_slots(false);
-            unsigned idx = input->data.location - VARYING_SLOT_VAR0;
+            unsigned idx =
+               compute_variable_location_slot(input, consumer->Stage);
             unsigned slot_limit = idx + num_elements;
 
+            if (!validate_explicit_variable_location(ctx,
+                                                     input_explicit_locations,
+                                                     input, prog, consumer)) {
+               return;
+            }
+
             while (idx < slot_limit) {
-               output = explicit_locations[idx][input->data.location_frac];
+               if (idx >= MAX_VARYING) {
+                  linker_error(prog,
+                               "Invalid location %u in %s shader\n", idx,
+                               _mesa_shader_stage_to_string(consumer->Stage));
+                  return;
+               }
+
+               output = output_explicit_locations[idx][input->data.location_frac].var;
 
-               if (output == NULL ||
-                   input->data.location != output->data.location) {
+               if (output == NULL) {
+                  /* A linker failure should only happen when there is no
+                   * output declaration and there is Static Use of the
+                   * declared input.
+                   */
+                  if (input->data.used) {
+                     linker_error(prog,
+                                  "%s shader input `%s' with explicit location "
+                                  "has no matching output\n",
+                                  _mesa_shader_stage_to_string(consumer->Stage),
+                                  input->name);
+                     break;
+                  }
+               } else if (input->data.location != output->data.location) {
                   linker_error(prog,
                                "%s shader input `%s' with explicit location "
                                "has no matching output\n",
@@ -550,7 +865,7 @@ cross_validate_outputs_to_inputs(struct gl_shader_program *prog,
              */
             if (!(input->get_interface_type() &&
                   output->get_interface_type()))
-               cross_validate_types_and_qualifiers(prog, input, output,
+               cross_validate_types_and_qualifiers(ctx, prog, input, output,
                                                    consumer->Stage,
                                                    producer->Stage);
          } else {
@@ -560,7 +875,7 @@ cross_validate_outputs_to_inputs(struct gl_shader_program *prog,
              */
             assert(!input->data.assigned);
             if (input->data.used && !input->get_interface_type() &&
-                !input->data.explicit_location && !prog->SeparateShader)
+                !input->data.explicit_location)
                linker_error(prog,
                             "%s shader input `%s' "
                             "has no matching output in the previous stage\n",
@@ -854,8 +1169,10 @@ bool
 tfeedback_decl::store(struct gl_context *ctx, struct gl_shader_program *prog,
                       struct gl_transform_feedback_info *info,
                       unsigned buffer, unsigned buffer_index,
-                      const unsigned max_outputs, bool *explicit_stride,
-                      bool has_xfb_qualifiers) const
+                      const unsigned max_outputs,
+                      BITSET_WORD *used_components[MAX_FEEDBACK_BUFFERS],
+                      bool *explicit_stride, bool has_xfb_qualifiers,
+                      const void* mem_ctx) const
 {
    unsigned xfb_offset = 0;
    unsigned size = this->size;
@@ -882,6 +1199,72 @@ tfeedback_decl::store(struct gl_context *ctx, struct gl_shader_program *prog,
       unsigned location = this->location;
       unsigned location_frac = this->location_frac;
       unsigned num_components = this->num_components();
+
+      /* From GL_EXT_transform_feedback:
+       *
+       *   " A program will fail to link if:
+       *
+       *       * the total number of components to capture is greater than the
+       *         constant MAX_TRANSFORM_FEEDBACK_INTERLEAVED_COMPONENTS_EXT
+       *         and the buffer mode is INTERLEAVED_ATTRIBS_EXT."
+       *
+       * From GL_ARB_enhanced_layouts:
+       *
+       *   " The resulting stride (implicit or explicit) must be less than or
+       *     equal to the implementation-dependent constant
+       *     gl_MaxTransformFeedbackInterleavedComponents."
+       */
+      if ((prog->TransformFeedback.BufferMode == GL_INTERLEAVED_ATTRIBS ||
+           has_xfb_qualifiers) &&
+          xfb_offset + num_components >
+          ctx->Const.MaxTransformFeedbackInterleavedComponents) {
+         linker_error(prog,
+                      "The MAX_TRANSFORM_FEEDBACK_INTERLEAVED_COMPONENTS "
+                      "limit has been exceeded.");
+         return false;
+      }
+
+      /* From the OpenGL 4.60.5 spec, section 4.4.2. Output Layout Qualifiers,
+       * Page 76, (Transform Feedback Layout Qualifiers):
+       *
+       *   " No aliasing in output buffers is allowed: It is a compile-time or
+       *     link-time error to specify variables with overlapping transform
+       *     feedback offsets."
+       */
+      const unsigned max_components =
+         ctx->Const.MaxTransformFeedbackInterleavedComponents;
+      const unsigned first_component = xfb_offset;
+      const unsigned last_component = xfb_offset + num_components - 1;
+      const unsigned start_word = BITSET_BITWORD(first_component);
+      const unsigned end_word = BITSET_BITWORD(last_component);
+      BITSET_WORD *used;
+      assert(last_component < max_components);
+
+      if (!used_components[buffer]) {
+         used_components[buffer] =
+            rzalloc_array(mem_ctx, BITSET_WORD, BITSET_WORDS(max_components));
+      }
+      used = used_components[buffer];
+
+      for (unsigned word = start_word; word <= end_word; word++) {
+         unsigned start_range = 0;
+         unsigned end_range = BITSET_WORDBITS - 1;
+
+         if (word == start_word)
+            start_range = first_component % BITSET_WORDBITS;
+
+         if (word == end_word)
+            end_range = last_component % BITSET_WORDBITS;
+
+         if (used[word] & BITSET_RANGE(start_range, end_range)) {
+            linker_error(prog,
+                         "variable '%s', xfb_offset (%d) is causing aliasing.",
+                         this->orig_name, xfb_offset * 4);
+            return false;
+         }
+         used[word] |= BITSET_RANGE(start_range, end_range);
+      }
+
       while (num_components > 0) {
          unsigned output_size = MIN2(num_components, 4 - location_frac);
          assert((info->NumOutputs == 0 && max_outputs == 0) ||
@@ -922,8 +1305,7 @@ tfeedback_decl::store(struct gl_context *ctx, struct gl_shader_program *prog,
          return false;
       }
 
-      if ((this->offset / 4) / info->Buffers[buffer].Stride !=
-          (xfb_offset - 1) / info->Buffers[buffer].Stride) {
+      if (xfb_offset > info->Buffers[buffer].Stride) {
          linker_error(prog, "xfb_offset (%d) overflows xfb_stride (%d) for "
                       "buffer (%d)", xfb_offset * 4,
                       info->Buffers[buffer].Stride * 4, buffer);
@@ -933,28 +1315,6 @@ tfeedback_decl::store(struct gl_context *ctx, struct gl_shader_program *prog,
       info->Buffers[buffer].Stride = xfb_offset;
    }
 
-   /* From GL_EXT_transform_feedback:
-    *   A program will fail to link if:
-    *
-    *     * the total number of components to capture is greater than
-    *       the constant MAX_TRANSFORM_FEEDBACK_INTERLEAVED_COMPONENTS_EXT
-    *       and the buffer mode is INTERLEAVED_ATTRIBS_EXT.
-    *
-    * From GL_ARB_enhanced_layouts:
-    *
-    *   "The resulting stride (implicit or explicit) must be less than or
-    *   equal to the implementation-dependent constant
-    *   gl_MaxTransformFeedbackInterleavedComponents."
-    */
-   if ((prog->TransformFeedback.BufferMode == GL_INTERLEAVED_ATTRIBS ||
-        has_xfb_qualifiers) &&
-       info->Buffers[buffer].Stride >
-       ctx->Const.MaxTransformFeedbackInterleavedComponents) {
-      linker_error(prog, "The MAX_TRANSFORM_FEEDBACK_INTERLEAVED_COMPONENTS "
-                   "limit has been exceeded.");
-      return false;
-   }
-
  store_varying:
    info->Varyings[info->NumVarying].Name = ralloc_strdup(prog,
                                                          this->orig_name);
@@ -1040,13 +1400,12 @@ parse_tfeedback_decls(struct gl_context *ctx, struct gl_shader_program *prog,
        * feedback of arrays would be useless otherwise.
        */
       for (unsigned j = 0; j < i; ++j) {
-         if (!decls[j].is_varying())
-            continue;
-
-         if (tfeedback_decl::is_same(decls[i], decls[j])) {
-            linker_error(prog, "Transform feedback varying %s specified "
-                         "more than once.", varying_names[i]);
-            return false;
+         if (decls[j].is_varying()) {
+            if (tfeedback_decl::is_same(decls[i], decls[j])) {
+               linker_error(prog, "Transform feedback varying %s specified "
+                            "more than once.", varying_names[i]);
+               return false;
+            }
          }
       }
    }
@@ -1076,7 +1435,8 @@ cmp_xfb_offset(const void * x_generic, const void * y_generic)
 static bool
 store_tfeedback_info(struct gl_context *ctx, struct gl_shader_program *prog,
                      unsigned num_tfeedback_decls,
-                     tfeedback_decl *tfeedback_decls, bool has_xfb_qualifiers)
+                     tfeedback_decl *tfeedback_decls, bool has_xfb_qualifiers,
+                     const void *mem_ctx)
 {
    if (!prog->last_vert_prog)
       return true;
@@ -1097,9 +1457,10 @@ store_tfeedback_info(struct gl_context *ctx, struct gl_shader_program *prog,
     * however some drivers expect to receive the list of transform feedback
     * declarations in order so sort it now for convenience.
     */
-   if (has_xfb_qualifiers)
+   if (has_xfb_qualifiers) {
       qsort(tfeedback_decls, num_tfeedback_decls, sizeof(*tfeedback_decls),
             cmp_xfb_offset);
+   }
 
    xfb_prog->sh.LinkedTransformFeedback->Varyings =
       rzalloc_array(xfb_prog, struct gl_transform_feedback_varying_info,
@@ -1117,6 +1478,7 @@ store_tfeedback_info(struct gl_context *ctx, struct gl_shader_program *prog,
 
    unsigned num_buffers = 0;
    unsigned buffers = 0;
+   BITSET_WORD *used_components[MAX_FEEDBACK_BUFFERS] = {};
 
    if (!has_xfb_qualifiers && separate_attribs_mode) {
       /* GL_SEPARATE_ATTRIBS */
@@ -1124,7 +1486,8 @@ store_tfeedback_info(struct gl_context *ctx, struct gl_shader_program *prog,
          if (!tfeedback_decls[i].store(ctx, prog,
                                        xfb_prog->sh.LinkedTransformFeedback,
                                        num_buffers, num_buffers, num_outputs,
-                                       NULL, has_xfb_qualifiers))
+                                       used_components, NULL,
+                                       has_xfb_qualifiers, mem_ctx))
             return false;
 
          buffers |= 1 << num_buffers;
@@ -1142,7 +1505,6 @@ store_tfeedback_info(struct gl_context *ctx, struct gl_shader_program *prog,
       if (has_xfb_qualifiers) {
          for (unsigned j = 0; j < MAX_FEEDBACK_BUFFERS; j++) {
             if (prog->TransformFeedback.BufferStride[j]) {
-               buffers |= 1 << j;
                explicit_stride[j] = true;
                xfb_prog->sh.LinkedTransformFeedback->Buffers[j].Stride =
                   prog->TransformFeedback.BufferStride[j] / 4;
@@ -1162,15 +1524,30 @@ store_tfeedback_info(struct gl_context *ctx, struct gl_shader_program *prog,
             if (!tfeedback_decls[i].store(ctx, prog,
                                           xfb_prog->sh.LinkedTransformFeedback,
                                           buffer, num_buffers, num_outputs,
-                                          explicit_stride, has_xfb_qualifiers))
+                                          used_components, explicit_stride,
+                                          has_xfb_qualifiers, mem_ctx))
                return false;
             num_buffers++;
             buffer_stream_id = -1;
             continue;
-         } else if (tfeedback_decls[i].is_varying()) {
+         }
+
+         if (has_xfb_qualifiers) {
+            buffer = tfeedback_decls[i].get_buffer();
+         } else {
+            buffer = num_buffers;
+         }
+
+         if (tfeedback_decls[i].is_varying()) {
             if (buffer_stream_id == -1)  {
                /* First varying writing to this buffer: remember its stream */
                buffer_stream_id = (int) tfeedback_decls[i].get_stream_id();
+
+               /* Only mark a buffer as active when there is a varying
+                * attached to it. This behaviour is based on a revised version
+                * of section 13.2.2 of the GL 4.6 spec.
+                */
+               buffers |= 1 << buffer;
             } else if (buffer_stream_id !=
                        (int) tfeedback_decls[i].get_stream_id()) {
                /* Varying writes to the same buffer from a different stream */
@@ -1186,17 +1563,11 @@ store_tfeedback_info(struct gl_context *ctx, struct gl_shader_program *prog,
             }
          }
 
-         if (has_xfb_qualifiers) {
-            buffer = tfeedback_decls[i].get_buffer();
-         } else {
-            buffer = num_buffers;
-         }
-         buffers |= 1 << buffer;
-
          if (!tfeedback_decls[i].store(ctx, prog,
                                        xfb_prog->sh.LinkedTransformFeedback,
                                        buffer, num_buffers, num_outputs,
-                                       explicit_stride, has_xfb_qualifiers))
+                                       used_components, explicit_stride,
+                                       has_xfb_qualifiers, mem_ctx))
             return false;
       }
    }
@@ -1217,18 +1588,19 @@ class varying_matches
 {
 public:
    varying_matches(bool disable_varying_packing, bool xfb_enabled,
+                   bool enhanced_layouts_enabled,
                    gl_shader_stage producer_stage,
                    gl_shader_stage consumer_stage);
    ~varying_matches();
    void record(ir_variable *producer_var, ir_variable *consumer_var);
    unsigned assign_locations(struct gl_shader_program *prog,
-                             uint8_t *components,
+                             uint8_t components[],
                              uint64_t reserved_slots);
    void store_locations() const;
 
 private:
    bool is_varying_packing_safe(const glsl_type *type,
-                                const ir_variable *var);
+                                const ir_variable *var) const;
 
    /**
     * If true, this driver disables varying packing, so all varyings need to
@@ -1250,6 +1622,8 @@ private:
     */
    const bool xfb_enabled;
 
+   const bool enhanced_layouts_enabled;
+
    /**
     * Enum representing the order in which varyings are packed within a
     * packing class.
@@ -1326,10 +1700,12 @@ private:
 
 varying_matches::varying_matches(bool disable_varying_packing,
                                  bool xfb_enabled,
+                                 bool enhanced_layouts_enabled,
                                  gl_shader_stage producer_stage,
                                  gl_shader_stage consumer_stage)
    : disable_varying_packing(disable_varying_packing),
      xfb_enabled(xfb_enabled),
+     enhanced_layouts_enabled(enhanced_layouts_enabled),
      producer_stage(producer_stage),
      consumer_stage(consumer_stage)
 {
@@ -1357,14 +1733,14 @@ varying_matches::~varying_matches()
  */
 bool
 varying_matches::is_varying_packing_safe(const glsl_type *type,
-                                         const ir_variable *var)
+                                         const ir_variable *var) const
 {
    if (consumer_stage == MESA_SHADER_TESS_EVAL ||
        consumer_stage == MESA_SHADER_TESS_CTRL ||
        producer_stage == MESA_SHADER_TESS_CTRL)
       return false;
 
-   return xfb_enabled && (type->is_array() || type->is_record() ||
+   return xfb_enabled && (type->is_array() || type->is_struct() ||
                           type->is_matrix() || var->data.is_xfb_only);
 }
 
@@ -1407,7 +1783,7 @@ varying_matches::record(ir_variable *producer_var, ir_variable *consumer_var)
 
    if (!disable_varying_packing &&
        (needs_flat_qualifier ||
-        (consumer_stage != -1 && consumer_stage != MESA_SHADER_FRAGMENT))) {
+        (consumer_stage != MESA_SHADER_NONE && consumer_stage != MESA_SHADER_FRAGMENT))) {
       /* Since this varying is not being consumed by the fragment shader, its
        * interpolation type varying cannot possibly affect rendering.
        * Also, this variable is non-flat and is (or contains) an integer
@@ -1461,17 +1837,24 @@ varying_matches::record(ir_variable *producer_var, ir_variable *consumer_var)
       ? consumer_stage : producer_stage;
    const glsl_type *type = get_varying_type(var, stage);
 
+   if (producer_var && consumer_var &&
+       consumer_var->data.must_be_shader_input) {
+      producer_var->data.must_be_shader_input = 1;
+   }
+
    this->matches[this->num_matches].packing_class
       = this->compute_packing_class(var);
    this->matches[this->num_matches].packing_order
       = this->compute_packing_order(var);
-   if (this->disable_varying_packing && !is_varying_packing_safe(type, var)) {
+   if ((this->disable_varying_packing && !is_varying_packing_safe(type, var)) ||
+       var->data.must_be_shader_input) {
       unsigned slots = type->count_attribute_slots(false);
       this->matches[this->num_matches].num_components = slots * 4;
    } else {
       this->matches[this->num_matches].num_components
          = type->component_slots();
    }
+
    this->matches[this->num_matches].producer_var = producer_var;
    this->matches[this->num_matches].consumer_var = consumer_var;
    this->num_matches++;
@@ -1485,10 +1868,15 @@ varying_matches::record(ir_variable *producer_var, ir_variable *consumer_var)
 /**
  * Choose locations for all of the variable matches that were previously
  * passed to varying_matches::record().
+ * \param components  returns array[slot] of number of components used
+ *                    per slot (1, 2, 3 or 4)
+ * \param reserved_slots  bitmask indicating which varying slots are already
+ *                        allocated
+ * \return number of slots (4-element vectors) allocated
  */
 unsigned
 varying_matches::assign_locations(struct gl_shader_program *prog,
-                                  uint8_t *components,
+                                  uint8_t components[],
                                   uint64_t reserved_slots)
 {
    /* If packing has been disabled then we cannot safely sort the varyings by
@@ -1513,13 +1901,24 @@ varying_matches::assign_locations(struct gl_shader_program *prog,
    unsigned generic_location = 0;
    unsigned generic_patch_location = MAX_VARYING*4;
    bool previous_var_xfb_only = false;
+   unsigned previous_packing_class = ~0u;
+
+   /* For tranform feedback separate mode, we know the number of attributes
+    * is <= the number of buffers.  So packing isn't critical.  In fact,
+    * packing vec3 attributes can cause trouble because splitting a vec3
+    * effectively creates an additional transform feedback output.  The
+    * extra TFB output may exceed device driver limits.
+    */
+   const bool dont_pack_vec3 =
+      (prog->TransformFeedback.BufferMode == GL_SEPARATE_ATTRIBS &&
+       prog->TransformFeedback.NumVarying > 0);
 
    for (unsigned i = 0; i < this->num_matches; i++) {
       unsigned *location = &generic_location;
-
       const ir_variable *var;
       const glsl_type *type;
       bool is_vertex_input = false;
+
       if (matches[i].consumer_var) {
          var = matches[i].consumer_var;
          type = get_varying_type(var, consumer_stage);
@@ -1544,14 +1943,17 @@ varying_matches::assign_locations(struct gl_shader_program *prog,
        * we can pack varyings together that are only used for transform
        * feedback.
        */
-      if ((this->disable_varying_packing &&
+      if (var->data.must_be_shader_input ||
+          (this->disable_varying_packing &&
            !(previous_var_xfb_only && var->data.is_xfb_only)) ||
-          (i > 0 && this->matches[i - 1].packing_class
-          != this->matches[i].packing_class )) {
+          (previous_packing_class != this->matches[i].packing_class) ||
+          (this->matches[i].packing_order == PACKING_ORDER_VEC3 &&
+           dont_pack_vec3)) {
          *location = ALIGN(*location, 4);
       }
 
       previous_var_xfb_only = var->data.is_xfb_only;
+      previous_packing_class = this->matches[i].packing_class;
 
       /* The number of components taken up by this variable. For vertex shader
        * inputs, we use the number of slots * 4, as they have different
@@ -1575,13 +1977,13 @@ varying_matches::assign_locations(struct gl_shader_program *prog,
          const uint64_t slot_mask = ((1ull << slots) - 1) << (*location / 4u);
 
          assert(slots > 0);
-         if (reserved_slots & slot_mask) {
-            *location = ALIGN(*location + 1, 4);
-            slot_end = *location + num_components - 1;
-            continue;
+
+         if ((reserved_slots & slot_mask) == 0) {
+            break;
          }
 
-         break;
+         *location = ALIGN(*location + 1, 4);
+         slot_end = *location + num_components - 1;
       }
 
       if (!var->data.patch && slot_end >= MAX_VARYING * 4u) {
@@ -1614,6 +2016,12 @@ varying_matches::assign_locations(struct gl_shader_program *prog,
 void
 varying_matches::store_locations() const
 {
+   /* Check is location needs to be packed with lower_packed_varyings() or if
+    * we can just use ARB_enhanced_layouts packing.
+    */
+   bool pack_loc[MAX_VARYINGS_INCL_PATCH] = { 0 };
+   const glsl_type *loc_type[MAX_VARYINGS_INCL_PATCH][4] = { {NULL, NULL} };
+
    for (unsigned i = 0; i < this->num_matches; i++) {
       ir_variable *producer_var = this->matches[i].producer_var;
       ir_variable *consumer_var = this->matches[i].consumer_var;
@@ -1631,6 +2039,64 @@ varying_matches::store_locations() const
          consumer_var->data.location = VARYING_SLOT_VAR0 + slot;
          consumer_var->data.location_frac = offset;
       }
+
+      /* Find locations suitable for native packing via
+       * ARB_enhanced_layouts.
+       */
+      if (producer_var && consumer_var) {
+         if (enhanced_layouts_enabled) {
+            const glsl_type *type =
+               get_varying_type(producer_var, producer_stage);
+            if (type->is_array() || type->is_matrix() || type->is_struct() ||
+                type->is_double()) {
+               unsigned comp_slots = type->component_slots() + offset;
+               unsigned slots = comp_slots / 4;
+               if (comp_slots % 4)
+                  slots += 1;
+
+               for (unsigned j = 0; j < slots; j++) {
+                  pack_loc[slot + j] = true;
+               }
+            } else if (offset + type->vector_elements > 4) {
+               pack_loc[slot] = true;
+               pack_loc[slot + 1] = true;
+            } else {
+               loc_type[slot][offset] = type;
+            }
+         }
+      }
+   }
+
+   /* Attempt to use ARB_enhanced_layouts for more efficient packing if
+    * suitable.
+    */
+   if (enhanced_layouts_enabled) {
+      for (unsigned i = 0; i < this->num_matches; i++) {
+         ir_variable *producer_var = this->matches[i].producer_var;
+         ir_variable *consumer_var = this->matches[i].consumer_var;
+         unsigned generic_location = this->matches[i].generic_location;
+         unsigned slot = generic_location / 4;
+
+         if (pack_loc[slot] || !producer_var || !consumer_var)
+            continue;
+
+         const glsl_type *type =
+            get_varying_type(producer_var, producer_stage);
+         bool type_match = true;
+         for (unsigned j = 0; j < 4; j++) {
+            if (loc_type[slot][j]) {
+               if (type->base_type != loc_type[slot][j]->base_type)
+                  type_match = false;
+            }
+         }
+
+         if (type_match) {
+            producer_var->data.explicit_location = 1;
+            consumer_var->data.explicit_location = 1;
+            producer_var->data.explicit_component = 1;
+            consumer_var->data.explicit_component = 1;
+         }
+      }
    }
 }
 
@@ -1659,11 +2125,17 @@ varying_matches::compute_packing_class(const ir_variable *var)
     *
     * Therefore, the packing class depends only on the interpolation type.
     */
-   unsigned packing_class = var->data.centroid | (var->data.sample << 1) |
-                            (var->data.patch << 2);
-   packing_class *= 4;
-   packing_class += var->is_interpolation_flat()
+   const unsigned interp = var->is_interpolation_flat()
       ? unsigned(INTERP_MODE_FLAT) : var->data.interpolation;
+
+   assert(interp < (1 << 3));
+
+   const unsigned packing_class = (interp << 0) |
+                                  (var->data.centroid << 3) |
+                                  (var->data.sample << 4) |
+                                  (var->data.patch << 5) |
+                                  (var->data.must_be_shader_input << 6);
+
    return packing_class;
 }
 
@@ -1720,7 +2192,7 @@ varying_matches::xfb_comparator(const void *x_generic, const void *y_generic)
    const match *x = (const match *) x_generic;
 
    if (x->producer_var != NULL && x->producer_var->data.is_xfb_only)
-         return match_comparator(x_generic, y_generic);
+      return match_comparator(x_generic, y_generic);
 
    /* FIXME: When the comparator returns 0 it means the elements being
     * compared are equivalent. However the qsort documentation says:
@@ -1773,9 +2245,11 @@ class tfeedback_candidate_generator : public program_resource_visitor
 {
 public:
    tfeedback_candidate_generator(void *mem_ctx,
-                                 hash_table *tfeedback_candidates)
+                                 hash_table *tfeedback_candidates,
+                                 gl_shader_stage stage)
       : mem_ctx(mem_ctx),
         tfeedback_candidates(tfeedback_candidates),
+        stage(stage),
         toplevel_var(NULL),
         varying_floats(0)
    {
@@ -1785,10 +2259,17 @@ public:
    {
       /* All named varying interface blocks should be flattened by now */
       assert(!var->is_interface_instance());
+      assert(var->data.mode == ir_var_shader_out);
 
       this->toplevel_var = var;
       this->varying_floats = 0;
-      program_resource_visitor::process(var);
+      const glsl_type *t =
+         var->data.from_named_ifc_block ? var->get_interface_type() : var->type;
+      if (!var->data.patch && stage == MESA_SHADER_TESS_CTRL) {
+         assert(t->is_array());
+         t = t->fields.array;
+      }
+      program_resource_visitor::process(var, t, false);
    }
 
 private:
@@ -1798,7 +2279,7 @@ private:
                             const enum glsl_interface_packing,
                             bool /* last_field */)
    {
-      assert(!type->without_array()->is_record());
+      assert(!type->without_array()->is_struct());
       assert(!type->without_array()->is_interface());
 
       tfeedback_candidate *candidate
@@ -1822,6 +2303,8 @@ private:
     */
    hash_table * const tfeedback_candidates;
 
+   gl_shader_stage stage;
+
    /**
     * Pointer to the toplevel variable that is being traversed.
     */
@@ -2017,7 +2500,8 @@ reserved_varying_slot(struct gl_linked_shader *stage,
       var_slot = var->data.location - VARYING_SLOT_VAR0;
 
       unsigned num_elements = get_varying_type(var, stage->Stage)
-         ->count_attribute_slots(stage->Stage == MESA_SHADER_VERTEX);
+         ->count_attribute_slots(io_mode == ir_var_shader_in &&
+                                 stage->Stage == MESA_SHADER_VERTEX);
       for (unsigned i = 0; i < num_elements; i++) {
          if (var_slot >= 0 && var_slot < MAX_VARYINGS_INCL_PATCH)
             slots |= UINT64_C(1) << var_slot;
@@ -2091,8 +2575,9 @@ assign_varying_locations(struct gl_context *ctx,
       disable_varying_packing = true;
 
    varying_matches matches(disable_varying_packing, xfb_enabled,
-                           producer ? producer->Stage : (gl_shader_stage)-1,
-                           consumer ? consumer->Stage : (gl_shader_stage)-1);
+                           ctx->Extensions.ARB_enhanced_layouts,
+                           producer ? producer->Stage : MESA_SHADER_NONE,
+                           consumer ? consumer->Stage : MESA_SHADER_NONE);
    hash_table *tfeedback_candidates =
          _mesa_hash_table_create(NULL, _mesa_key_hash_string,
                                  _mesa_key_string_equal);
@@ -2150,8 +2635,28 @@ assign_varying_locations(struct gl_context *ctx,
                  producer->Stage == MESA_SHADER_GEOMETRY));
 
          if (num_tfeedback_decls > 0) {
-            tfeedback_candidate_generator g(mem_ctx, tfeedback_candidates);
-            g.process(output_var);
+            tfeedback_candidate_generator g(mem_ctx, tfeedback_candidates, producer->Stage);
+            /* From OpenGL 4.6 (Core Profile) spec, section 11.1.2.1
+             * ("Vertex Shader Variables / Output Variables")
+             *
+             * "Each program object can specify a set of output variables from
+             * one shader to be recorded in transform feedback mode (see
+             * section 13.3). The variables that can be recorded are those
+             * emitted by the first active shader, in order, from the
+             * following list:
+             *
+             *  * geometry shader
+             *  * tessellation evaluation shader
+             *  * tessellation control shader
+             *  * vertex shader"
+             *
+             * But on OpenGL ES 3.2, section 11.1.2.1 ("Vertex Shader
+             * Variables / Output Variables") tessellation control shader is
+             * not included in the stages list.
+             */
+            if (!prog->IsES || producer->Stage != MESA_SHADER_TESS_CTRL) {
+               g.process(output_var);
+            }
          }
 
          ir_variable *const input_var =
@@ -2188,17 +2693,12 @@ assign_varying_locations(struct gl_context *ctx,
        */
       foreach_in_list(ir_instruction, node, consumer->ir) {
          ir_variable *const input_var = node->as_variable();
-
-         if (input_var == NULL || input_var->data.mode != ir_var_shader_in)
-            continue;
-
-         matches.record(NULL, input_var);
+         if (input_var && input_var->data.mode == ir_var_shader_in) {
+            matches.record(NULL, input_var);
+         }
       }
    }
 
-   _mesa_hash_table_destroy(consumer_inputs, NULL);
-   _mesa_hash_table_destroy(consumer_interface_inputs, NULL);
-
    for (unsigned i = 0; i < num_tfeedback_decls; ++i) {
       if (!tfeedback_decls[i].is_varying())
          continue;
@@ -2211,24 +2711,45 @@ assign_varying_locations(struct gl_context *ctx,
          return false;
       }
 
+      /* Mark xfb varyings as always active */
+      matched_candidate->toplevel_var->data.always_active_io = 1;
+
+      /* Mark any corresponding inputs as always active also. We must do this
+       * because we have a NIR pass that lowers vectors to scalars and another
+       * that removes unused varyings.
+       * We don't split varyings marked as always active because there is no
+       * point in doing so. This means we need to mark both sides of the
+       * interface as always active otherwise we will have a mismatch and
+       * start removing things we shouldn't.
+       */
+      ir_variable *const input_var =
+         linker::get_matching_input(mem_ctx, matched_candidate->toplevel_var,
+                                    consumer_inputs,
+                                    consumer_interface_inputs,
+                                    consumer_inputs_with_locations);
+      if (input_var)
+         input_var->data.always_active_io = 1;
+
       if (matched_candidate->toplevel_var->data.is_unmatched_generic_inout) {
          matched_candidate->toplevel_var->data.is_xfb_only = 1;
          matches.record(matched_candidate->toplevel_var, NULL);
       }
    }
 
+   _mesa_hash_table_destroy(consumer_inputs, NULL);
+   _mesa_hash_table_destroy(consumer_interface_inputs, NULL);
+
    uint8_t components[MAX_VARYINGS_INCL_PATCH] = {0};
    const unsigned slots_used = matches.assign_locations(
          prog, components, reserved_slots);
    matches.store_locations();
 
    for (unsigned i = 0; i < num_tfeedback_decls; ++i) {
-      if (!tfeedback_decls[i].is_varying())
-         continue;
-
-      if (!tfeedback_decls[i].assign_location(ctx, prog)) {
-         _mesa_hash_table_destroy(tfeedback_candidates, NULL);
-         return false;
+      if (tfeedback_decls[i].is_varying()) {
+         if (!tfeedback_decls[i].assign_location(ctx, prog)) {
+            _mesa_hash_table_destroy(tfeedback_candidates, NULL);
+            return false;
+         }
       }
    }
    _mesa_hash_table_destroy(tfeedback_candidates, NULL);
@@ -2293,7 +2814,7 @@ assign_varying_locations(struct gl_context *ctx,
    return true;
 }
 
-bool
+static bool
 check_against_output_limit(struct gl_context *ctx,
                            struct gl_shader_program *prog,
                            gl_linked_shader *producer,
@@ -2337,7 +2858,7 @@ check_against_output_limit(struct gl_context *ctx,
    return true;
 }
 
-bool
+static bool
 check_against_input_limit(struct gl_context *ctx,
                           struct gl_shader_program *prog,
                           gl_linked_shader *consumer,
@@ -2516,13 +3037,13 @@ link_varyings(struct gl_shader_program *prog, unsigned first, unsigned last,
 
             /* This must be done after all dead varyings are eliminated. */
             if (sh_i != NULL) {
-               unsigned slots_used = _mesa_bitcount_64(reserved_out_slots);
+               unsigned slots_used = util_bitcount64(reserved_out_slots);
                if (!check_against_output_limit(ctx, prog, sh_i, slots_used)) {
                   return false;
                }
             }
 
-            unsigned slots_used = _mesa_bitcount_64(reserved_in_slots);
+            unsigned slots_used = util_bitcount64(reserved_in_slots);
             if (!check_against_input_limit(ctx, prog, sh_next, slots_used))
                return false;
 
@@ -2532,7 +3053,7 @@ link_varyings(struct gl_shader_program *prog, unsigned first, unsigned last,
    }
 
    if (!store_tfeedback_info(ctx, prog, num_tfeedback_decls, tfeedback_decls,
-                             has_xfb_qualifiers))
+                             has_xfb_qualifiers, mem_ctx))
       return false;
 
    return true;