1 files changed, 81 insertions, 0 deletions
diff --git a/src/glsl/opt_dead_builtin_variables.cpp b/src/glsl/opt_dead_builtin_variables.cpp
new file mode 100644
index 00000000000..85c75d6f21f
--- /dev/null
+++ b/src/glsl/opt_dead_builtin_variables.cpp
@@ -0,0 +1,81 @@
+/*
+ * Copyright © 2014 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#include "ir.h"
+#include "ir_visitor.h"
+#include "ir_optimization.h"
+
+/**
+ * Pre-linking, optimize unused built-in variables
+ *
+ * Uniforms, constants, system values, inputs (vertex shader only), and
+ * outputs (fragment shader only) that are not used can be removed.
+ */
+void
+optimize_dead_builtin_variables(exec_list *instructions,
+                                enum ir_variable_mode other)
+{
+   foreach_in_list_safe(ir_variable, var, instructions) {
+      if (var->ir_type != ir_type_variable || var->data.used)
+         continue;
+
+      if (var->data.mode != ir_var_uniform
+          && var->data.mode != ir_var_auto
+          && var->data.mode != ir_var_system_value
+          && var->data.mode != other)
+         continue;
+
+      /* So that linker rules can later be enforced, we cannot elimate
+       * variables that were redeclared in the shader code.
+       */
+      if ((var->data.mode == other || var->data.mode == ir_var_system_value)
+          && var->data.how_declared != ir_var_declared_implicitly)
+         continue;
+
+      if (strncmp(var->name, "gl_", 3) != 0)
+         continue;
+
+      /* gl_ModelViewProjectionMatrix and gl_Vertex are special because they
+       * are used by ftransform.  No other built-in variable is used by a
+       * built-in function.  The forward declarations of these variables in
+       * the built-in function shader does not have the "state slot"
+       * information, so removing these variables from the user shader will
+       * cause problems later.
+       *
+       * Matrix uniforms with "Transpose" are not eliminated because there's
+       * an optimization pass that can turn references to the regular matrix
+       * into references to the transpose matrix.  Eliminating the transpose
+       * matrix would cause that pass to generate references to undeclareds
+       * variables (thank you, ir_validate).
+       *
+       * It doesn't seem worth the effort to track when the transpose could be
+       * eliminated (i.e., when the non-transpose was eliminated).
+       */
+      if (strcmp(var->name, "gl_ModelViewProjectionMatrix") == 0
+          || strcmp(var->name, "gl_Vertex") == 0
+          || strstr(var->name, "Transpose") != NULL)
+         continue;
+
+      var->remove();
+   }
+}