1 files changed, 219 insertions, 0 deletions
diff --git a/src/glsl/ir_dead_code.cpp b/src/glsl/ir_dead_code.cpp
new file mode 100644
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+++ b/src/glsl/ir_dead_code.cpp
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+/*
+ * Copyright © 2010 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.
+ */
+
+/**
+ * \file ir_dead_code.cpp
+ *
+ * Eliminates dead assignments and variable declarations from the code.
+ */
+
+#include "ir.h"
+#include "ir_visitor.h"
+#include "ir_expression_flattening.h"
+#include "glsl_types.h"
+
+class variable_entry : public exec_node
+{
+public:
+   variable_entry(ir_variable *var)
+   {
+      this->var = var;
+      assign = NULL;
+      referenced_count = 0;
+      assigned_count = 0;
+      declaration = false;
+   }
+
+   ir_variable *var; /* The key: the variable's pointer. */
+   ir_assignment *assign; /* An assignment to the variable, if any */
+
+   /** Number of times the variable is referenced, including assignments. */
+   unsigned referenced_count;
+
+   /** Number of times the variable is assignmened. */
+   unsigned assigned_count;
+
+   bool declaration; /* If the variable had a decl in the instruction stream */
+};
+
+class ir_dead_code_visitor : public ir_hierarchical_visitor {
+public:
+   virtual ir_visitor_status visit(ir_variable *);
+   virtual ir_visitor_status visit(ir_dereference_variable *);
+
+   virtual ir_visitor_status visit_enter(ir_function *);
+   virtual ir_visitor_status visit_leave(ir_assignment *);
+
+   variable_entry *get_variable_entry(ir_variable *var);
+
+   bool (*predicate)(ir_instruction *ir);
+   ir_instruction *base_ir;
+
+   /* List of variable_entry */
+   exec_list variable_list;
+};
+
+
+variable_entry *
+ir_dead_code_visitor::get_variable_entry(ir_variable *var)
+{
+   assert(var);
+   foreach_iter(exec_list_iterator, iter, this->variable_list) {
+      variable_entry *entry = (variable_entry *)iter.get();
+      if (entry->var == var)
+	 return entry;
+   }
+
+   void *ctx = talloc_parent(var);
+
+   variable_entry *entry = new(ctx) variable_entry(var);
+   this->variable_list.push_tail(entry);
+   return entry;
+}
+
+
+ir_visitor_status
+ir_dead_code_visitor::visit(ir_variable *ir)
+{
+   variable_entry *entry = this->get_variable_entry(ir);
+   if (entry)
+      entry->declaration = true;
+
+   return visit_continue;
+}
+
+
+ir_visitor_status
+ir_dead_code_visitor::visit(ir_dereference_variable *ir)
+{
+   ir_variable *const var = ir->variable_referenced();
+   variable_entry *entry = this->get_variable_entry(var);
+
+   if (entry)
+      entry->referenced_count++;
+
+   return visit_continue;
+}
+
+
+ir_visitor_status
+ir_dead_code_visitor::visit_enter(ir_function *ir)
+{
+   (void) ir;
+   return visit_continue_with_parent;
+}
+
+
+ir_visitor_status
+ir_dead_code_visitor::visit_leave(ir_assignment *ir)
+{
+   variable_entry *entry;
+   entry = this->get_variable_entry(ir->lhs->variable_referenced());
+   if (entry) {
+      entry->assigned_count++;
+      if (entry->assign == NULL)
+	 entry->assign = ir;
+   }
+
+   return visit_continue;
+}
+
+
+/**
+ * Do a dead code pass over instructions and everything that instructions
+ * references.
+ *
+ * Note that this will remove assignments to globals, so it is not suitable
+ * for usage on an unlinked instruction stream.
+ */
+bool
+do_dead_code(exec_list *instructions)
+{
+   ir_dead_code_visitor v;
+   bool progress = false;
+
+   v.run(instructions);
+
+   foreach_iter(exec_list_iterator, iter, v.variable_list) {
+      variable_entry *entry = (variable_entry *)iter.get();
+
+      /* Since each assignment is a reference, the refereneced count must be
+       * greater than or equal to the assignment count.  If they are equal,
+       * then all of the references are assignments, and the variable is
+       * dead.
+       *
+       * Note that if the variable is neither assigned nor referenced, both
+       * counts will be zero and will be caught by the equality test.
+       */
+      assert(entry->referenced_count >= entry->assigned_count);
+
+      if ((entry->referenced_count > entry->assigned_count)
+	  || !entry->declaration)
+	 continue;
+
+      if (entry->assign) {
+	 /* Remove a single dead assignment to the variable we found.
+	  * Don't do so if it's a shader output, though.
+	  */
+	 if (!entry->var->shader_out) {
+	    entry->assign->remove();
+	    progress = true;
+	 }
+      } else {
+	 /* If there are no assignments or references to the variable left,
+	  * then we can remove its declaration.
+	  */
+	 entry->var->remove();
+	 progress = true;
+      }
+   }
+   return progress;
+}
+
+/**
+ * Does a dead code pass on the functions present in the instruction stream.
+ *
+ * This is suitable for use while the program is not linked, as it will
+ * ignore variable declarations (and the assignments to them) for variables
+ * with global scope.
+ */
+bool
+do_dead_code_unlinked(exec_list *instructions)
+{
+   bool progress = false;
+
+   foreach_iter(exec_list_iterator, iter, *instructions) {
+      ir_instruction *ir = (ir_instruction *)iter.get();
+      ir_function *f = ir->as_function();
+      if (f) {
+	 foreach_iter(exec_list_iterator, sigiter, *f) {
+	    ir_function_signature *sig =
+	       (ir_function_signature *) sigiter.get();
+	    if (do_dead_code(&sig->body))
+	       progress = true;
+	 }
+      }
+   }
+
+   return progress;
+}