docs: Add sha256 sums for the 10.5.1 release
[mesa.git] / src / glsl / linker.cpp
index 7d605d7e59bdbcdd612000ad035212b7b7e85ffd..0c4467779707fcc7b9fb90cb982ef051a242869f 100644 (file)
@@ -64,6 +64,7 @@
  * \author Ian Romanick <ian.d.romanick@intel.com>
  */
 
+#include <ctype.h>
 #include "main/core.h"
 #include "glsl_symbol_table.h"
 #include "glsl_parser_extras.h"
 #include "link_varyings.h"
 #include "ir_optimization.h"
 #include "ir_rvalue_visitor.h"
+#include "ir_uniform.h"
 
-extern "C" {
 #include "main/shaderobj.h"
 #include "main/enums.h"
-}
+
 
 void linker_error(gl_shader_program *, const char *, ...);
 
@@ -249,31 +250,100 @@ public:
    }
 };
 
-
 /**
- * Visitor that determines whether or not a shader uses ir_end_primitive.
+ * Visitor that determines the highest stream id to which a (geometry) shader
+ * emits vertices. It also checks whether End{Stream}Primitive is ever called.
  */
-class find_end_primitive_visitor : public ir_hierarchical_visitor {
+class find_emit_vertex_visitor : public ir_hierarchical_visitor {
 public:
-   find_end_primitive_visitor()
-      : found(false)
+   find_emit_vertex_visitor(int max_allowed)
+      : max_stream_allowed(max_allowed),
+        invalid_stream_id(0),
+        invalid_stream_id_from_emit_vertex(false),
+        end_primitive_found(false),
+        uses_non_zero_stream(false)
    {
       /* empty */
    }
 
-   virtual ir_visitor_status visit(ir_end_primitive *)
+   virtual ir_visitor_status visit_leave(ir_emit_vertex *ir)
    {
-      found = true;
-      return visit_stop;
+      int stream_id = ir->stream_id();
+
+      if (stream_id < 0) {
+         invalid_stream_id = stream_id;
+         invalid_stream_id_from_emit_vertex = true;
+         return visit_stop;
+      }
+
+      if (stream_id > max_stream_allowed) {
+         invalid_stream_id = stream_id;
+         invalid_stream_id_from_emit_vertex = true;
+         return visit_stop;
+      }
+
+      if (stream_id != 0)
+         uses_non_zero_stream = true;
+
+      return visit_continue;
    }
 
-   bool end_primitive_found()
+   virtual ir_visitor_status visit_leave(ir_end_primitive *ir)
    {
-      return found;
+      end_primitive_found = true;
+
+      int stream_id = ir->stream_id();
+
+      if (stream_id < 0) {
+         invalid_stream_id = stream_id;
+         invalid_stream_id_from_emit_vertex = false;
+         return visit_stop;
+      }
+
+      if (stream_id > max_stream_allowed) {
+         invalid_stream_id = stream_id;
+         invalid_stream_id_from_emit_vertex = false;
+         return visit_stop;
+      }
+
+      if (stream_id != 0)
+         uses_non_zero_stream = true;
+
+      return visit_continue;
+   }
+
+   bool error()
+   {
+      return invalid_stream_id != 0;
+   }
+
+   const char *error_func()
+   {
+      return invalid_stream_id_from_emit_vertex ?
+         "EmitStreamVertex" : "EndStreamPrimitive";
+   }
+
+   int error_stream()
+   {
+      return invalid_stream_id;
+   }
+
+   bool uses_streams()
+   {
+      return uses_non_zero_stream;
+   }
+
+   bool uses_end_primitive()
+   {
+      return end_primitive_found;
    }
 
 private:
-   bool found;
+   int max_stream_allowed;
+   int invalid_stream_id;
+   bool invalid_stream_id_from_emit_vertex;
+   bool end_primitive_found;
+   bool uses_non_zero_stream;
 };
 
 } /* anonymous namespace */
@@ -297,7 +367,7 @@ linker_warning(gl_shader_program *prog, const char *fmt, ...)
 {
    va_list ap;
 
-   ralloc_strcat(&prog->InfoLog, "error: ");
+   ralloc_strcat(&prog->InfoLog, "warning: ");
    va_start(ap, fmt);
    ralloc_vasprintf_append(&prog->InfoLog, fmt, ap);
    va_end(ap);
@@ -367,8 +437,8 @@ parse_program_resource_name(const GLchar *name,
 void
 link_invalidate_variable_locations(exec_list *ir)
 {
-   foreach_list(node, ir) {
-      ir_variable *const var = ((ir_instruction *) node)->as_variable();
+   foreach_in_list(ir_instruction, node, ir) {
+      ir_variable *const var = node->as_variable();
 
       if (var == NULL)
          continue;
@@ -489,14 +559,21 @@ validate_vertex_shader_executable(struct gl_shader_program *prog,
     *      vertex processing has occurred. Its value is undefined if
     *      the vertex shader executable does not write gl_Position."
     *
-    * GLSL ES 3.00 is similar to GLSL 1.40--failing to write to gl_Position is
-    * not an error.
+    * All GLSL ES Versions are similar to GLSL 1.40--failing to write to
+    * gl_Position is not an error.
     */
    if (prog->Version < (prog->IsES ? 300 : 140)) {
       find_assignment_visitor find("gl_Position");
       find.run(shader->ir);
       if (!find.variable_found()) {
-        linker_error(prog, "vertex shader does not write to `gl_Position'\n");
+        if (prog->IsES) {
+          linker_warning(prog,
+                         "vertex shader does not write to `gl_Position'."
+                         "It's value is undefined. \n");
+        } else {
+          linker_error(prog,
+                       "vertex shader does not write to `gl_Position'. \n");
+        }
         return;
       }
    }
@@ -550,10 +627,97 @@ validate_geometry_shader_executable(struct gl_shader_program *prog,
 
    analyze_clip_usage(prog, shader, &prog->Geom.UsesClipDistance,
                       &prog->Geom.ClipDistanceArraySize);
+}
+
+/**
+ * Check if geometry shaders emit to non-zero streams and do corresponding
+ * validations.
+ */
+static void
+validate_geometry_shader_emissions(struct gl_context *ctx,
+                                   struct gl_shader_program *prog)
+{
+   if (prog->_LinkedShaders[MESA_SHADER_GEOMETRY] != NULL) {
+      find_emit_vertex_visitor emit_vertex(ctx->Const.MaxVertexStreams - 1);
+      emit_vertex.run(prog->_LinkedShaders[MESA_SHADER_GEOMETRY]->ir);
+      if (emit_vertex.error()) {
+         linker_error(prog, "Invalid call %s(%d). Accepted values for the "
+                      "stream parameter are in the range [0, %d].\n",
+                      emit_vertex.error_func(),
+                      emit_vertex.error_stream(),
+                      ctx->Const.MaxVertexStreams - 1);
+      }
+      prog->Geom.UsesStreams = emit_vertex.uses_streams();
+      prog->Geom.UsesEndPrimitive = emit_vertex.uses_end_primitive();
+
+      /* From the ARB_gpu_shader5 spec:
+       *
+       *   "Multiple vertex streams are supported only if the output primitive
+       *    type is declared to be "points".  A program will fail to link if it
+       *    contains a geometry shader calling EmitStreamVertex() or
+       *    EndStreamPrimitive() if its output primitive type is not "points".
+       *
+       * However, in the same spec:
+       *
+       *   "The function EmitVertex() is equivalent to calling EmitStreamVertex()
+       *    with <stream> set to zero."
+       *
+       * And:
+       *
+       *   "The function EndPrimitive() is equivalent to calling
+       *    EndStreamPrimitive() with <stream> set to zero."
+       *
+       * Since we can call EmitVertex() and EndPrimitive() when we output
+       * primitives other than points, calling EmitStreamVertex(0) or
+       * EmitEndPrimitive(0) should not produce errors. This it also what Nvidia
+       * does. Currently we only set prog->Geom.UsesStreams to TRUE when
+       * EmitStreamVertex() or EmitEndPrimitive() are called with a non-zero
+       * stream.
+       */
+      if (prog->Geom.UsesStreams && prog->Geom.OutputType != GL_POINTS) {
+         linker_error(prog, "EmitStreamVertex(n) and EndStreamPrimitive(n) "
+                      "with n>0 requires point output\n");
+      }
+   }
+}
 
-   find_end_primitive_visitor end_primitive;
-   end_primitive.run(shader->ir);
-   prog->Geom.UsesEndPrimitive = end_primitive.end_primitive_found();
+bool
+validate_intrastage_arrays(struct gl_shader_program *prog,
+                           ir_variable *const var,
+                          ir_variable *const existing)
+{
+   /* Consider the types to be "the same" if both types are arrays
+    * of the same type and one of the arrays is implicitly sized.
+    * In addition, set the type of the linked variable to the
+    * explicitly sized array.
+    */
+   if (var->type->is_array() && existing->type->is_array() &&
+       (var->type->fields.array == existing->type->fields.array) &&
+       ((var->type->length == 0)|| (existing->type->length == 0))) {
+      if (var->type->length != 0) {
+         if (var->type->length <= existing->data.max_array_access) {
+            linker_error(prog, "%s `%s' declared as type "
+                         "`%s' but outermost dimension has an index"
+                         " of `%i'\n",
+                         mode_string(var),
+                         var->name, var->type->name,
+                         existing->data.max_array_access);
+         }
+         existing->type = var->type;
+         return true;
+      } else if (existing->type->length != 0) {
+         if(existing->type->length <= var->data.max_array_access) {
+            linker_error(prog, "%s `%s' declared as type "
+                         "`%s' but outermost dimension has an index"
+                         " of `%i'\n",
+                         mode_string(var),
+                         var->name, existing->type->name,
+                         var->data.max_array_access);
+         }
+         return true;
+      }
+   }
+   return false;
 }
 
 
@@ -574,8 +738,8 @@ cross_validate_globals(struct gl_shader_program *prog,
       if (shader_list[i] == NULL)
         continue;
 
-      foreach_list(node, shader_list[i]->ir) {
-        ir_variable *const var = ((ir_instruction *) node)->as_variable();
+      foreach_in_list(ir_instruction, node, shader_list[i]->ir) {
+        ir_variable *const var = node->as_variable();
 
         if (var == NULL)
            continue;
@@ -595,31 +759,23 @@ cross_validate_globals(struct gl_shader_program *prog,
          */
         ir_variable *const existing = variables.get_variable(var->name);
         if (existing != NULL) {
-           if (var->type != existing->type) {
-              /* Consider the types to be "the same" if both types are arrays
-               * of the same type and one of the arrays is implicitly sized.
-               * In addition, set the type of the linked variable to the
-               * explicitly sized array.
-               */
-              if (var->type->is_array()
-                  && existing->type->is_array()
-                  && (var->type->fields.array == existing->type->fields.array)
-                  && ((var->type->length == 0)
-                      || (existing->type->length == 0))) {
-                 if (var->type->length != 0) {
-                    existing->type = var->type;
-                 }
-               } else if (var->type->is_record()
-                  && existing->type->is_record()
-                  && existing->type->record_compare(var->type)) {
-                 existing->type = var->type;
-              } else {
-                 linker_error(prog, "%s `%s' declared as type "
-                              "`%s' and type `%s'\n",
-                              mode_string(var),
-                              var->name, var->type->name,
-                              existing->type->name);
-                 return;
+            /* Check if types match. Interface blocks have some special
+             * rules so we handle those elsewhere.
+             */
+           if (var->type != existing->type &&
+                !var->is_interface_instance()) {
+              if (!validate_intrastage_arrays(prog, var, existing)) {
+                  if (var->type->is_record() && existing->type->is_record()
+                      && existing->type->record_compare(var->type)) {
+                     existing->type = var->type;
+                  } else {
+                     linker_error(prog, "%s `%s' declared as type "
+                                  "`%s' and type `%s'\n",
+                                  mode_string(var),
+                                  var->name, var->type->name,
+                                  existing->type->name);
+                     return;
+                  }
               }
            }
 
@@ -683,7 +839,7 @@ cross_validate_globals(struct gl_shader_program *prog,
                  linker_error(prog,
                               "All redeclarations of gl_FragDepth in all "
                               "fragment shaders in a single program must have "
-                              "the same set of qualifiers.");
+                              "the same set of qualifiers.\n");
               }
 
               if (var->data.used && layout_differs) {
@@ -692,7 +848,7 @@ cross_validate_globals(struct gl_shader_program *prog,
                               "qualifier in any fragment shader, it must be "
                               "redeclared with the same layout qualifier in "
                               "all fragment shaders that have assignments to "
-                              "gl_FragDepth");
+                              "gl_FragDepth\n");
               }
            }
 
@@ -823,7 +979,7 @@ interstage_cross_validate_uniform_blocks(struct gl_shader_program *prog)
                                                       &sh->UniformBlocks[j]);
 
         if (index == -1) {
-           linker_error(prog, "uniform block `%s' has mismatching definitions",
+           linker_error(prog, "uniform block `%s' has mismatching definitions\n",
                         sh->UniformBlocks[j].Name);
            return false;
         }
@@ -844,15 +1000,15 @@ populate_symbol_table(gl_shader *sh)
 {
    sh->symbols = new(sh) glsl_symbol_table;
 
-   foreach_list(node, sh->ir) {
-      ir_instruction *const inst = (ir_instruction *) node;
+   foreach_in_list(ir_instruction, inst, sh->ir) {
       ir_variable *var;
       ir_function *func;
 
       if ((func = inst->as_function()) != NULL) {
         sh->symbols->add_function(func);
       } else if ((var = inst->as_variable()) != NULL) {
-        sh->symbols->add_variable(var);
+         if (var->data.mode != ir_var_temporary)
+            sh->symbols->add_variable(var);
       }
    }
 }
@@ -961,9 +1117,7 @@ move_non_declarations(exec_list *instructions, exec_node *last,
       temps = hash_table_ctor(0, hash_table_pointer_hash,
                              hash_table_pointer_compare);
 
-   foreach_list_safe(node, instructions) {
-      ir_instruction *inst = (ir_instruction *) node;
-
+   foreach_in_list_safe(ir_instruction, inst, instructions) {
       if (inst->as_function())
         continue;
 
@@ -1000,8 +1154,8 @@ move_non_declarations(exec_list *instructions, exec_node *last,
 /**
  * Get the function signature for main from a shader
  */
-static ir_function_signature *
-get_main_function_signature(gl_shader *sh)
+ir_function_signature *
+link_get_main_function_signature(gl_shader *sh)
 {
    ir_function *const f = sh->symbols->get_function("main");
    if (f != NULL) {
@@ -1014,7 +1168,8 @@ get_main_function_signature(gl_shader *sh)
        * We don't have to check for multiple definitions of main (in multiple
        * shaders) because that would have already been caught above.
        */
-      ir_function_signature *sig = f->matching_signature(NULL, &void_parameters);
+      ir_function_signature *sig =
+         f->matching_signature(NULL, &void_parameters, false);
       if ((sig != NULL) && sig->is_defined) {
         return sig;
       }
@@ -1050,7 +1205,8 @@ public:
       if (var->type->is_interface()) {
          if (interface_contains_unsized_arrays(var->type)) {
             const glsl_type *new_type =
-               resize_interface_members(var->type, var->max_ifc_array_access);
+               resize_interface_members(var->type,
+                                        var->get_max_ifc_array_access());
             var->type = new_type;
             var->change_interface_type(new_type);
          }
@@ -1059,7 +1215,7 @@ public:
          if (interface_contains_unsized_arrays(var->type->fields.array)) {
             const glsl_type *new_type =
                resize_interface_members(var->type->fields.array,
-                                        var->max_ifc_array_access);
+                                        var->get_max_ifc_array_access());
             var->change_interface_type(new_type);
             var->type =
                glsl_type::get_array_instance(new_type, var->type->length);
@@ -1194,6 +1350,83 @@ private:
    hash_table *unnamed_interfaces;
 };
 
+/**
+ * Performs the cross-validation of layout qualifiers specified in
+ * redeclaration of gl_FragCoord for the attached fragment shaders,
+ * and propagates them to the linked FS and linked shader program.
+ */
+static void
+link_fs_input_layout_qualifiers(struct gl_shader_program *prog,
+                               struct gl_shader *linked_shader,
+                               struct gl_shader **shader_list,
+                               unsigned num_shaders)
+{
+   linked_shader->redeclares_gl_fragcoord = false;
+   linked_shader->uses_gl_fragcoord = false;
+   linked_shader->origin_upper_left = false;
+   linked_shader->pixel_center_integer = false;
+
+   if (linked_shader->Stage != MESA_SHADER_FRAGMENT ||
+       (prog->Version < 150 && !prog->ARB_fragment_coord_conventions_enable))
+      return;
+
+   for (unsigned i = 0; i < num_shaders; i++) {
+      struct gl_shader *shader = shader_list[i];
+      /* From the GLSL 1.50 spec, page 39:
+       *
+       *   "If gl_FragCoord is redeclared in any fragment shader in a program,
+       *    it must be redeclared in all the fragment shaders in that program
+       *    that have a static use gl_FragCoord."
+       *
+       * Exclude the case when one of the 'linked_shader' or 'shader' redeclares
+       * gl_FragCoord with no layout qualifiers but the other one doesn't
+       * redeclare it. If we strictly follow GLSL 1.50 spec's language, it
+       * should be a link error. But, generating link error for this case will
+       * be a wrong behaviour which spec didn't intend to do and it could also
+       * break some applications.
+       */
+      if ((linked_shader->redeclares_gl_fragcoord
+           && !shader->redeclares_gl_fragcoord
+           && shader->uses_gl_fragcoord
+           && (linked_shader->origin_upper_left
+               || linked_shader->pixel_center_integer))
+          || (shader->redeclares_gl_fragcoord
+              && !linked_shader->redeclares_gl_fragcoord
+              && linked_shader->uses_gl_fragcoord
+              && (shader->origin_upper_left
+                  || shader->pixel_center_integer))) {
+             linker_error(prog, "fragment shader defined with conflicting "
+                         "layout qualifiers for gl_FragCoord\n");
+      }
+
+      /* From the GLSL 1.50 spec, page 39:
+       *
+       *   "All redeclarations of gl_FragCoord in all fragment shaders in a
+       *    single program must have the same set of qualifiers."
+       */
+      if (linked_shader->redeclares_gl_fragcoord && shader->redeclares_gl_fragcoord
+          && (shader->origin_upper_left != linked_shader->origin_upper_left
+          || shader->pixel_center_integer != linked_shader->pixel_center_integer)) {
+         linker_error(prog, "fragment shader defined with conflicting "
+                      "layout qualifiers for gl_FragCoord\n");
+      }
+
+      /* Update the linked shader state. Â Note that uses_gl_fragcoord should
+       * accumulate the results. Â The other values should replace. Â If there
+       * are multiple redeclarations, all the fields except uses_gl_fragcoord
+       * are already known to be the same.
+       */
+      if (shader->redeclares_gl_fragcoord || shader->uses_gl_fragcoord) {
+         linked_shader->redeclares_gl_fragcoord =
+            shader->redeclares_gl_fragcoord;
+         linked_shader->uses_gl_fragcoord = linked_shader->uses_gl_fragcoord
+            || shader->uses_gl_fragcoord;
+         linked_shader->origin_upper_left = shader->origin_upper_left;
+         linked_shader->pixel_center_integer = shader->pixel_center_integer;
+      }
+   }
+}
+
 /**
  * Performs the cross-validation of geometry shader max_vertices and
  * primitive type layout qualifiers for the attached geometry shaders,
@@ -1206,6 +1439,7 @@ link_gs_inout_layout_qualifiers(struct gl_shader_program *prog,
                                unsigned num_shaders)
 {
    linked_shader->Geom.VerticesOut = 0;
+   linked_shader->Geom.Invocations = 0;
    linked_shader->Geom.InputType = PRIM_UNKNOWN;
    linked_shader->Geom.OutputType = PRIM_UNKNOWN;
 
@@ -1259,6 +1493,18 @@ link_gs_inout_layout_qualifiers(struct gl_shader_program *prog,
         }
         linked_shader->Geom.VerticesOut = shader->Geom.VerticesOut;
       }
+
+      if (shader->Geom.Invocations != 0) {
+        if (linked_shader->Geom.Invocations != 0 &&
+            linked_shader->Geom.Invocations != shader->Geom.Invocations) {
+           linker_error(prog, "geometry shader defined with conflicting "
+                        "invocation count (%d and %d)\n",
+                        linked_shader->Geom.Invocations,
+                        shader->Geom.Invocations);
+           return;
+        }
+        linked_shader->Geom.Invocations = shader->Geom.Invocations;
+      }
    }
 
    /* Just do the intrastage -> interstage propagation right now,
@@ -1285,6 +1531,11 @@ link_gs_inout_layout_qualifiers(struct gl_shader_program *prog,
       return;
    }
    prog->Geom.VerticesOut = linked_shader->Geom.VerticesOut;
+
+   if (linked_shader->Geom.Invocations == 0)
+      linked_shader->Geom.Invocations = 1;
+
+   prog->Geom.Invocations = linked_shader->Geom.Invocations;
 }
 
 
@@ -1383,13 +1634,15 @@ link_intrastage_shaders(void *mem_ctx,
    const unsigned num_uniform_blocks =
       link_uniform_blocks(mem_ctx, prog, shader_list, num_shaders,
                           &uniform_blocks);
+   if (!prog->LinkStatus)
+      return NULL;
 
    /* Check that there is only a single definition of each function signature
     * across all shaders.
     */
    for (unsigned i = 0; i < (num_shaders - 1); i++) {
-      foreach_list(node, shader_list[i]->ir) {
-        ir_function *const f = ((ir_instruction *) node)->as_function();
+      foreach_in_list(ir_instruction, node, shader_list[i]->ir) {
+        ir_function *const f = node->as_function();
 
         if (f == NULL)
            continue;
@@ -1404,9 +1657,7 @@ link_intrastage_shaders(void *mem_ctx,
            if (other == NULL)
               continue;
 
-           foreach_list(n, &f->signatures) {
-              ir_function_signature *sig = (ir_function_signature *) n;
-
+           foreach_in_list(ir_function_signature, sig, &f->signatures) {
               if (!sig->is_defined || sig->is_builtin())
                  continue;
 
@@ -1415,7 +1666,7 @@ link_intrastage_shaders(void *mem_ctx,
 
               if ((other_sig != NULL) && other_sig->is_defined
                   && !other_sig->is_builtin()) {
-                 linker_error(prog, "function `%s' is multiply defined",
+                 linker_error(prog, "function `%s' is multiply defined\n",
                               f->name);
                  return NULL;
               }
@@ -1433,7 +1684,7 @@ link_intrastage_shaders(void *mem_ctx,
     */
    gl_shader *main = NULL;
    for (unsigned i = 0; i < num_shaders; i++) {
-      if (get_main_function_signature(shader_list[i]) != NULL) {
+      if (link_get_main_function_signature(shader_list[i]) != NULL) {
         main = shader_list[i];
         break;
       }
@@ -1453,15 +1704,17 @@ link_intrastage_shaders(void *mem_ctx,
    linked->NumUniformBlocks = num_uniform_blocks;
    ralloc_steal(linked, linked->UniformBlocks);
 
+   link_fs_input_layout_qualifiers(prog, linked, shader_list, num_shaders);
    link_gs_inout_layout_qualifiers(prog, linked, shader_list, num_shaders);
    link_cs_input_layout_qualifiers(prog, linked, shader_list, num_shaders);
 
    populate_symbol_table(linked);
 
-   /* The pointer to the main function in the final linked shader (i.e., the
+   /* The pointer to the main function in the final linked shader (i.e., the
     * copy of the original shader that contained the main function).
     */
-   ir_function_signature *const main_sig = get_main_function_signature(linked);
+   ir_function_signature *const main_sig =
+      link_get_main_function_signature(linked);
 
    /* Move any instructions other than variable declarations or function
     * declarations into main.
@@ -1494,12 +1747,19 @@ link_intrastage_shaders(void *mem_ctx,
        */
       gl_shader **linking_shaders = (gl_shader **)
          calloc(num_shaders + 1, sizeof(gl_shader *));
-      memcpy(linking_shaders, shader_list, num_shaders * sizeof(gl_shader *));
-      linking_shaders[num_shaders] = _mesa_glsl_get_builtin_function_shader();
 
-      ok = link_function_calls(prog, linked, linking_shaders, num_shaders + 1);
+      ok = linking_shaders != NULL;
 
-      free(linking_shaders);
+      if (ok) {
+         memcpy(linking_shaders, shader_list, num_shaders * sizeof(gl_shader *));
+         linking_shaders[num_shaders] = _mesa_glsl_get_builtin_function_shader();
+
+         ok = link_function_calls(prog, linked, linking_shaders, num_shaders + 1);
+
+         free(linking_shaders);
+      } else {
+         _mesa_error_no_memory(__func__);
+      }
    } else {
       ok = link_function_calls(prog, linked, shader_list, num_shaders);
    }
@@ -1519,12 +1779,14 @@ link_intrastage_shaders(void *mem_ctx,
    if (linked->Stage == MESA_SHADER_GEOMETRY) {
       unsigned num_vertices = vertices_per_prim(prog->Geom.InputType);
       geom_array_resize_visitor input_resize_visitor(num_vertices, prog);
-      foreach_list(n, linked->ir) {
-         ir_instruction *ir = (ir_instruction *) n;
+      foreach_in_list(ir_instruction, ir, linked->ir) {
          ir->accept(&input_resize_visitor);
       }
    }
 
+   if (ctx->Const.VertexID_is_zero_based)
+      lower_vertex_id(linked);
+
    /* Make a pass over all variable declarations to ensure that arrays with
     * unspecified sizes have a size specified.  The size is inferred from the
     * max_array_access field.
@@ -1558,8 +1820,8 @@ update_array_sizes(struct gl_shader_program *prog)
         if (prog->_LinkedShaders[i] == NULL)
            continue;
 
-      foreach_list(node, prog->_LinkedShaders[i]->ir) {
-        ir_variable *const var = ((ir_instruction *) node)->as_variable();
+      foreach_in_list(ir_instruction, node, prog->_LinkedShaders[i]->ir) {
+        ir_variable *const var = node->as_variable();
 
         if ((var == NULL) || (var->data.mode != ir_var_uniform) ||
             !var->type->is_array())
@@ -1581,8 +1843,8 @@ update_array_sizes(struct gl_shader_program *prog)
               if (prog->_LinkedShaders[j] == NULL)
                  continue;
 
-           foreach_list(node2, prog->_LinkedShaders[j]->ir) {
-              ir_variable *other_var = ((ir_instruction *) node2)->as_variable();
+           foreach_in_list(ir_instruction, node2, prog->_LinkedShaders[j]->ir) {
+              ir_variable *other_var = node2->as_variable();
               if (!other_var)
                  continue;
 
@@ -1602,9 +1864,10 @@ update_array_sizes(struct gl_shader_program *prog)
             * Determine the number of slots per array element by dividing by
             * the old (total) size.
             */
-           if (var->num_state_slots > 0) {
-              var->num_state_slots = (size + 1)
-                 * (var->num_state_slots / var->type->length);
+            const unsigned num_slots = var->get_num_state_slots();
+           if (num_slots > 0) {
+              var->set_num_state_slots((size + 1)
+                                        * (num_slots / var->type->length));
            }
 
            var->type = glsl_type::get_array_instance(var->type->fields.array,
@@ -1650,7 +1913,7 @@ find_available_slots(unsigned used_mask, unsigned needed_count)
 
 
 /**
- * Assign locations for either VS inputs for FS outputs
+ * Assign locations for either VS inputs or FS outputs
  *
  * \param prog          Shader program whose variables need locations assigned
  * \param target_index  Selector for the program target to receive location
@@ -1724,8 +1987,8 @@ assign_attribute_or_color_locations(gl_shader_program *prog,
 
    unsigned num_attr = 0;
 
-   foreach_list(node, sh->ir) {
-      ir_variable *const var = ((ir_instruction *) node)->as_variable();
+   foreach_in_list(ir_instruction, node, sh->ir) {
+      ir_variable *const var = node->as_variable();
 
       if ((var == NULL) || (var->data.mode != (unsigned) direction))
         continue;
@@ -1780,10 +2043,12 @@ assign_attribute_or_color_locations(gl_shader_program *prog,
             *     active attribute array, both of which require multiple
             *     contiguous generic attributes."
             *
-            * Previous versions of the spec contain similar language but omit
-            * the bit about attribute arrays.
+            * I think above text prohibits the aliasing of explicit and
+            * automatic assignments. But, aliasing is allowed in manual
+            * assignments of attribute locations. See below comments for
+            * the details.
             *
-            * Page 61 of the OpenGL 4.0 spec also says:
+            * From OpenGL 4.0 spec, page 61:
             *
             *     "It is possible for an application to bind more than one
             *     attribute name to the same location. This is referred to as
@@ -1796,29 +2061,84 @@ assign_attribute_or_color_locations(gl_shader_program *prog,
             *     but implementations are not required to generate an error
             *     in this case."
             *
-            * These two paragraphs are either somewhat contradictory, or I
-            * don't fully understand one or both of them.
-            */
-           /* FINISHME: The code as currently written does not support
-            * FINISHME: attribute location aliasing (see comment above).
+            * From GLSL 4.30 spec, page 54:
+            *
+            *    "A program will fail to link if any two non-vertex shader
+            *     input variables are assigned to the same location. For
+            *     vertex shaders, multiple input variables may be assigned
+            *     to the same location using either layout qualifiers or via
+            *     the OpenGL API. However, such aliasing is intended only to
+            *     support vertex shaders where each execution path accesses
+            *     at most one input per each location. Implementations are
+            *     permitted, but not required, to generate link-time errors
+            *     if they detect that every path through the vertex shader
+            *     executable accesses multiple inputs assigned to any single
+            *     location. For all shader types, a program will fail to link
+            *     if explicit location assignments leave the linker unable
+            *     to find space for other variables without explicit
+            *     assignments."
+            *
+            * From OpenGL ES 3.0 spec, page 56:
+            *
+            *    "Binding more than one attribute name to the same location
+            *     is referred to as aliasing, and is not permitted in OpenGL
+            *     ES Shading Language 3.00 vertex shaders. LinkProgram will
+            *     fail when this condition exists. However, aliasing is
+            *     possible in OpenGL ES Shading Language 1.00 vertex shaders.
+            *     This will only work if only one of the aliased attributes
+            *     is active in the executable program, or if no path through
+            *     the shader consumes more than one attribute of a set of
+            *     attributes aliased to the same location. A link error can
+            *     occur if the linker determines that every path through the
+            *     shader consumes multiple aliased attributes, but implemen-
+            *     tations are not required to generate an error in this case."
+            *
+            * After looking at above references from OpenGL, OpenGL ES and
+            * GLSL specifications, we allow aliasing of vertex input variables
+            * in: OpenGL 2.0 (and above) and OpenGL ES 2.0.
+            *
+            * NOTE: This is not required by the spec but its worth mentioning
+            * here that we're not doing anything to make sure that no path
+            * through the vertex shader executable accesses multiple inputs
+            * assigned to any single location.
             */
+
            /* Mask representing the contiguous slots that will be used by
             * this attribute.
             */
            const unsigned attr = var->data.location - generic_base;
            const unsigned use_mask = (1 << slots) - 1;
+            const char *const string = (target_index == MESA_SHADER_VERTEX)
+               ? "vertex shader input" : "fragment shader output";
+
+            /* Generate a link error if the requested locations for this
+             * attribute exceed the maximum allowed attribute location.
+             */
+            if (attr + slots > max_index) {
+               linker_error(prog,
+                           "insufficient contiguous locations "
+                           "available for %s `%s' %d %d %d\n", string,
+                           var->name, used_locations, use_mask, attr);
+               return false;
+            }
 
            /* Generate a link error if the set of bits requested for this
             * attribute overlaps any previously allocated bits.
             */
            if ((~(use_mask << attr) & used_locations) != used_locations) {
-              const char *const string = (target_index == MESA_SHADER_VERTEX)
-                 ? "vertex shader input" : "fragment shader output";
-              linker_error(prog,
-                           "insufficient contiguous locations "
-                           "available for %s `%s' %d %d %d", string,
-                           var->name, used_locations, use_mask, attr);
-              return false;
+               if (target_index == MESA_SHADER_FRAGMENT ||
+                   (prog->IsES && prog->Version >= 300)) {
+                  linker_error(prog,
+                               "overlapping location is assigned "
+                               "to %s `%s' %d %d %d\n", string,
+                               var->name, used_locations, use_mask, attr);
+                  return false;
+               } else {
+                  linker_warning(prog,
+                                 "overlapping location is assigned "
+                                 "to %s `%s' %d %d %d\n", string,
+                                 var->name, used_locations, use_mask, attr);
+               }
            }
 
            used_locations |= (use_mask << attr);
@@ -1866,7 +2186,7 @@ assign_attribute_or_color_locations(gl_shader_program *prog,
 
         linker_error(prog,
                      "insufficient contiguous locations "
-                     "available for %s `%s'",
+                     "available for %s `%s'\n",
                      string, to_assign[i].var->name);
         return false;
       }
@@ -1886,8 +2206,8 @@ assign_attribute_or_color_locations(gl_shader_program *prog,
 void
 demote_shader_inputs_and_outputs(gl_shader *sh, enum ir_variable_mode mode)
 {
-   foreach_list(node, sh->ir) {
-      ir_variable *const var = ((ir_instruction *) node)->as_variable();
+   foreach_in_list(ir_instruction, node, sh->ir) {
+      ir_variable *const var = node->as_variable();
 
       if ((var == NULL) || (var->data.mode != int(mode)))
         continue;
@@ -1897,6 +2217,7 @@ demote_shader_inputs_and_outputs(gl_shader *sh, enum ir_variable_mode mode)
        * to have a location assigned.
        */
       if (var->data.is_unmatched_generic_inout) {
+         assert(var->data.mode != ir_var_temporary);
         var->data.mode = ir_var_auto;
       }
    }
@@ -1922,8 +2243,8 @@ store_fragdepth_layout(struct gl_shader_program *prog)
     * We're only interested in the cases where the variable is NOT removed
     * from the IR.
     */
-   foreach_list(node, ir) {
-      ir_variable *const var = ((ir_instruction *) node)->as_variable();
+   foreach_in_list(ir_instruction, node, ir) {
+      ir_variable *const var = node->as_variable();
 
       if (var == NULL || var->data.mode != ir_var_shader_out) {
          continue;
@@ -1967,7 +2288,7 @@ check_resources(struct gl_context *ctx, struct gl_shader_program *prog)
         continue;
 
       if (sh->num_samplers > ctx->Const.Program[i].MaxTextureImageUnits) {
-        linker_error(prog, "Too many %s shader texture samplers",
+        linker_error(prog, "Too many %s shader texture samplers\n",
                      _mesa_shader_stage_to_string(i));
       }
 
@@ -1981,7 +2302,7 @@ check_resources(struct gl_context *ctx, struct gl_shader_program *prog)
                            _mesa_shader_stage_to_string(i));
          } else {
             linker_error(prog, "Too many %s shader default uniform block "
-                        "components",
+                        "components\n",
                          _mesa_shader_stage_to_string(i));
          }
       }
@@ -1994,7 +2315,7 @@ check_resources(struct gl_context *ctx, struct gl_shader_program *prog)
                            "this is non-portable out-of-spec behavior\n",
                            _mesa_shader_stage_to_string(i));
          } else {
-            linker_error(prog, "Too many %s shader uniform components",
+            linker_error(prog, "Too many %s shader uniform components\n",
                          _mesa_shader_stage_to_string(i));
          }
       }
@@ -2012,7 +2333,7 @@ check_resources(struct gl_context *ctx, struct gl_shader_program *prog)
       }
 
       if (total_uniform_blocks > ctx->Const.MaxCombinedUniformBlocks) {
-        linker_error(prog, "Too many combined uniform blocks (%d/%d)",
+        linker_error(prog, "Too many combined uniform blocks (%d/%d)\n",
                      prog->NumUniformBlocks,
                      ctx->Const.MaxCombinedUniformBlocks);
       } else {
@@ -2020,7 +2341,7 @@ check_resources(struct gl_context *ctx, struct gl_shader_program *prog)
             const unsigned max_uniform_blocks =
                ctx->Const.Program[i].MaxUniformBlocks;
            if (blocks[i] > max_uniform_blocks) {
-              linker_error(prog, "Too many %s uniform blocks (%d/%d)",
+              linker_error(prog, "Too many %s uniform blocks (%d/%d)\n",
                            _mesa_shader_stage_to_string(i),
                            blocks[i],
                            max_uniform_blocks);
@@ -2048,14 +2369,14 @@ check_image_resources(struct gl_context *ctx, struct gl_shader_program *prog)
 
       if (sh) {
          if (sh->NumImages > ctx->Const.Program[i].MaxImageUniforms)
-            linker_error(prog, "Too many %s shader image uniforms",
+            linker_error(prog, "Too many %s shader image uniforms\n",
                          _mesa_shader_stage_to_string(i));
 
          total_image_units += sh->NumImages;
 
          if (i == MESA_SHADER_FRAGMENT) {
-            foreach_list(node, sh->ir) {
-               ir_variable *var = ((ir_instruction *)node)->as_variable();
+            foreach_in_list(ir_instruction, node, sh->ir) {
+               ir_variable *var = node->as_variable();
                if (var && var->data.mode == ir_var_shader_out)
                   fragment_outputs += var->type->count_attribute_slots();
             }
@@ -2064,11 +2385,122 @@ check_image_resources(struct gl_context *ctx, struct gl_shader_program *prog)
    }
 
    if (total_image_units > ctx->Const.MaxCombinedImageUniforms)
-      linker_error(prog, "Too many combined image uniforms");
+      linker_error(prog, "Too many combined image uniforms\n");
 
    if (total_image_units + fragment_outputs >
        ctx->Const.MaxCombinedImageUnitsAndFragmentOutputs)
-      linker_error(prog, "Too many combined image uniforms and fragment outputs");
+      linker_error(prog, "Too many combined image uniforms and fragment outputs\n");
+}
+
+
+/**
+ * Initializes explicit location slots to INACTIVE_UNIFORM_EXPLICIT_LOCATION
+ * for a variable, checks for overlaps between other uniforms using explicit
+ * locations.
+ */
+static bool
+reserve_explicit_locations(struct gl_shader_program *prog,
+                           string_to_uint_map *map, ir_variable *var)
+{
+   unsigned slots = var->type->uniform_locations();
+   unsigned max_loc = var->data.location + slots - 1;
+
+   /* Resize remap table if locations do not fit in the current one. */
+   if (max_loc + 1 > prog->NumUniformRemapTable) {
+      prog->UniformRemapTable =
+         reralloc(prog, prog->UniformRemapTable,
+                  gl_uniform_storage *,
+                  max_loc + 1);
+
+      if (!prog->UniformRemapTable) {
+         linker_error(prog, "Out of memory during linking.\n");
+         return false;
+      }
+
+      /* Initialize allocated space. */
+      for (unsigned i = prog->NumUniformRemapTable; i < max_loc + 1; i++)
+         prog->UniformRemapTable[i] = NULL;
+
+      prog->NumUniformRemapTable = max_loc + 1;
+   }
+
+   for (unsigned i = 0; i < slots; i++) {
+      unsigned loc = var->data.location + i;
+
+      /* Check if location is already used. */
+      if (prog->UniformRemapTable[loc] == INACTIVE_UNIFORM_EXPLICIT_LOCATION) {
+
+         /* Possibly same uniform from a different stage, this is ok. */
+         unsigned hash_loc;
+         if (map->get(hash_loc, var->name) && hash_loc == loc - i)
+               continue;
+
+         /* ARB_explicit_uniform_location specification states:
+          *
+          *     "No two default-block uniform variables in the program can have
+          *     the same location, even if they are unused, otherwise a compiler
+          *     or linker error will be generated."
+          */
+         linker_error(prog,
+                      "location qualifier for uniform %s overlaps "
+                      "previously used location\n",
+                      var->name);
+         return false;
+      }
+
+      /* Initialize location as inactive before optimization
+       * rounds and location assignment.
+       */
+      prog->UniformRemapTable[loc] = INACTIVE_UNIFORM_EXPLICIT_LOCATION;
+   }
+
+   /* Note, base location used for arrays. */
+   map->put(var->data.location, var->name);
+
+   return true;
+}
+
+/**
+ * Check and reserve all explicit uniform locations, called before
+ * any optimizations happen to handle also inactive uniforms and
+ * inactive array elements that may get trimmed away.
+ */
+static void
+check_explicit_uniform_locations(struct gl_context *ctx,
+                                 struct gl_shader_program *prog)
+{
+   if (!ctx->Extensions.ARB_explicit_uniform_location)
+      return;
+
+   /* This map is used to detect if overlapping explicit locations
+    * occur with the same uniform (from different stage) or a different one.
+    */
+   string_to_uint_map *uniform_map = new string_to_uint_map;
+
+   if (!uniform_map) {
+      linker_error(prog, "Out of memory during linking.\n");
+      return;
+   }
+
+   for (unsigned i = 0; i < MESA_SHADER_STAGES; i++) {
+      struct gl_shader *sh = prog->_LinkedShaders[i];
+
+      if (!sh)
+         continue;
+
+      foreach_in_list(ir_instruction, node, sh->ir) {
+         ir_variable *var = node->as_variable();
+         if ((var && var->data.mode == ir_var_uniform) &&
+             var->data.explicit_location) {
+            if (!reserve_explicit_locations(prog, uniform_map, var)) {
+               delete uniform_map;
+               return;
+            }
+         }
+      }
+   }
+
+   delete uniform_map;
 }
 
 void
@@ -2083,20 +2515,7 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
    prog->Validated = false;
    prog->_Used = false;
 
-   ralloc_free(prog->InfoLog);
-   prog->InfoLog = ralloc_strdup(NULL, "");
-
-   ralloc_free(prog->UniformBlocks);
-   prog->UniformBlocks = NULL;
-   prog->NumUniformBlocks = 0;
-   for (int i = 0; i < MESA_SHADER_STAGES; i++) {
-      ralloc_free(prog->UniformBlockStageIndex[i]);
-      prog->UniformBlockStageIndex[i] = NULL;
-   }
-
-   ralloc_free(prog->AtomicBuffers);
-   prog->AtomicBuffers = NULL;
-   prog->NumAtomicBuffers = 0;
+   prog->ARB_fragment_coord_conventions_enable = false;
 
    /* Separate the shaders into groups based on their type.
     */
@@ -2123,6 +2542,9 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
         goto done;
       }
 
+      prog->ARB_fragment_coord_conventions_enable |=
+         prog->Shaders[i]->ARB_fragment_coord_conventions_enable;
+
       gl_shader_stage shader_type = prog->Shaders[i]->Stage;
       shader_list[shader_type][num_shaders[shader_type]] = prog->Shaders[i];
       num_shaders[shader_type]++;
@@ -2143,7 +2565,8 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
    /* Geometry shaders have to be linked with vertex shaders.
     */
    if (num_shaders[MESA_SHADER_GEOMETRY] > 0 &&
-       num_shaders[MESA_SHADER_VERTEX] == 0) {
+       num_shaders[MESA_SHADER_VERTEX] == 0 &&
+       !prog->SeparateShader) {
       linker_error(prog, "Geometry shader must be linked with "
                   "vertex shader\n");
       goto done;
@@ -2214,6 +2637,10 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
          break;
    }
 
+   check_explicit_uniform_locations(ctx, prog);
+   if (!prog->LinkStatus)
+      goto done;
+
    /* Validate the inputs of each stage with the output of the preceding
     * stage.
     */
@@ -2274,28 +2701,26 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
       if (!prog->LinkStatus)
         goto done;
 
-      if (ctx->ShaderCompilerOptions[i].LowerClipDistance) {
+      if (ctx->Const.ShaderCompilerOptions[i].LowerClipDistance) {
          lower_clip_distance(prog->_LinkedShaders[i]);
       }
 
-      unsigned max_unroll = ctx->ShaderCompilerOptions[i].MaxUnrollIterations;
-
-      while (do_common_optimization(prog->_LinkedShaders[i]->ir, true, false, max_unroll, &ctx->ShaderCompilerOptions[i]))
+      while (do_common_optimization(prog->_LinkedShaders[i]->ir, true, false,
+                                    &ctx->Const.ShaderCompilerOptions[i],
+                                    ctx->Const.NativeIntegers))
         ;
+
+      lower_const_arrays_to_uniforms(prog->_LinkedShaders[i]->ir);
    }
 
+   /* Check and validate stream emissions in geometry shaders */
+   validate_geometry_shader_emissions(ctx, prog);
+
    /* Mark all generic shader inputs and outputs as unpaired. */
-   if (prog->_LinkedShaders[MESA_SHADER_VERTEX] != NULL) {
-      link_invalidate_variable_locations(
-            prog->_LinkedShaders[MESA_SHADER_VERTEX]->ir);
-   }
-   if (prog->_LinkedShaders[MESA_SHADER_GEOMETRY] != NULL) {
-      link_invalidate_variable_locations(
-            prog->_LinkedShaders[MESA_SHADER_GEOMETRY]->ir);
-   }
-   if (prog->_LinkedShaders[MESA_SHADER_FRAGMENT] != NULL) {
-      link_invalidate_variable_locations(
-            prog->_LinkedShaders[MESA_SHADER_FRAGMENT]->ir);
+   for (unsigned i = MESA_SHADER_VERTEX; i <= MESA_SHADER_FRAGMENT; i++) {
+      if (prog->_LinkedShaders[i] != NULL) {
+         link_invalidate_variable_locations(prog->_LinkedShaders[i]->ir);
+      }
    }
 
    /* FINISHME: The value of the max_attribute_index parameter is
@@ -2327,7 +2752,7 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
        */
       if (first == MESA_SHADER_FRAGMENT) {
          linker_error(prog, "Transform feedback varyings specified, but "
-                      "no vertex or geometry shader is present.");
+                      "no vertex or geometry shader is present.\n");
          goto done;
       }
 
@@ -2352,7 +2777,22 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
    if (last >= 0 && last < MESA_SHADER_FRAGMENT) {
       gl_shader *const sh = prog->_LinkedShaders[last];
 
-      if (num_tfeedback_decls != 0) {
+      if (first == MESA_SHADER_GEOMETRY) {
+         /* There was no vertex shader, but we still have to assign varying
+          * locations for use by geometry shader inputs in SSO.
+          *
+          * If the shader is not separable (i.e., prog->SeparateShader is
+          * false), linking will have already failed when first is
+          * MESA_SHADER_GEOMETRY.
+          */
+         if (!assign_varying_locations(ctx, mem_ctx, prog,
+                                       NULL, sh,
+                                       num_tfeedback_decls, tfeedback_decls,
+                                       prog->Geom.VerticesIn))
+            goto done;
+      }
+
+      if (num_tfeedback_decls != 0 || prog->SeparateShader) {
          /* There was no fragment shader, but we still have to assign varying
           * locations for use by transform feedback.
           */
@@ -2366,7 +2806,8 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
       do_dead_builtin_varyings(ctx, sh, NULL,
                                num_tfeedback_decls, tfeedback_decls);
 
-      demote_shader_inputs_and_outputs(sh, ir_var_shader_out);
+      if (!prog->SeparateShader)
+         demote_shader_inputs_and_outputs(sh, ir_var_shader_out);
 
       /* Eliminate code that is now dead due to unused outputs being demoted.
        */
@@ -2381,7 +2822,16 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
       do_dead_builtin_varyings(ctx, NULL, sh,
                                num_tfeedback_decls, tfeedback_decls);
 
-      demote_shader_inputs_and_outputs(sh, ir_var_shader_in);
+      if (prog->SeparateShader) {
+         if (!assign_varying_locations(ctx, mem_ctx, prog,
+                                       NULL /* producer */,
+                                       sh /* consumer */,
+                                       0 /* num_tfeedback_decls */,
+                                       NULL /* tfeedback_decls */,
+                                       0 /* gs_input_vertices */))
+            goto done;
+      } else
+         demote_shader_inputs_and_outputs(sh, ir_var_shader_in);
 
       while (do_dead_code(sh->ir, false))
          ;
@@ -2429,7 +2879,7 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
       goto done;
 
    update_array_sizes(prog);
-   link_assign_uniform_locations(prog);
+   link_assign_uniform_locations(prog, ctx->Const.UniformBooleanTrue);
    link_assign_atomic_counter_resources(ctx, prog);
    store_fragdepth_layout(prog);
 
@@ -2446,7 +2896,7 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
     * fragment shader) is absent. So, the extension shouldn't change the
     * behavior specified in GLSL specification.
     */
-   if (!prog->InternalSeparateShader && ctx->API == API_OPENGLES2) {
+   if (!prog->SeparateShader && ctx->API == API_OPENGLES2) {
       if (prog->_LinkedShaders[MESA_SHADER_VERTEX] == NULL) {
         linker_error(prog, "program lacks a vertex shader\n");
       } else if (prog->_LinkedShaders[MESA_SHADER_FRAGMENT] == NULL) {