Add an ir_if simplification pass.

This is relatively simple at the moment, recognizing only constant
values, and not (for example) values that are restricted to a range
that make the branching constant.  However, it does remove 59 lines
from the printout of CorrectParse2.vert.

Makefile.am

@@ -30,7 +30,8 @@ glsl_SOURCES = symbol_table.c hash_table.c glsl_types.cpp \
 	ir_print_visitor.cpp ir_variable.cpp ir_function.cpp \
 	ir_constant_expression.cpp \
 	ir_constant_folding.cpp \
-	ir_function_inlining.cpp
+	ir_function_inlining.cpp \
+	ir_if_simplification.cpp
 
 BUILT_SOURCES = glsl_parser.h builtin_types.h glsl_parser.cpp glsl_lexer.cpp
 CLEANFILES = $(BUILT_SOURCES)

glsl_parser_extras.cpp

@@ -36,6 +36,7 @@
 #include "glsl_parser.h"
 #include "ir_constant_folding.h"
 #include "ir_function_inlining.h"
+#include "ir_if_simplification.h"
 #include "ir_print_visitor.h"
 
 const char *
@@ -759,6 +760,7 @@ main(int argc, char **argv)
 	 progress = false;
 
 	 progress = do_function_inlining(&instructions) || progress;
+	 progress = do_if_simplification(&instructions) || progress;
 
 	 /* Constant folding */
 	 ir_constant_folding_visitor constant_folding;

ir.h

@@ -58,6 +58,7 @@ public:
    virtual class ir_assignment *        as_assignment()       { return NULL; }
    virtual class ir_call *              as_call()             { return NULL; }
    virtual class ir_return *            as_return()           { return NULL; }
+   virtual class ir_if *                as_if()               { return NULL; }
    /*@}*/
 
 protected:
@@ -299,6 +300,11 @@ public:
       /* empty */
    }
 
+   virtual ir_if *as_if()
+   {
+      return this;
+   }
+
    virtual void accept(ir_visitor *v)
    {
       v->visit(this);

ir_if_simplification.cpp

@@ -0,0 +1,235 @@
+/*
+ * 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_function_inlining.cpp
+ *
+ * Moves constant branches of if statements out to the surrounding
+ * instruction stream.
+ */
+
+#define NULL 0
+#include "ir.h"
+#include "ir_visitor.h"
+#include "ir_function_inlining.h"
+#include "glsl_types.h"
+
+class ir_if_simplification_visitor : public ir_visitor {
+public:
+   ir_if_simplification_visitor()
+   {
+      /* empty */
+   }
+
+   virtual ~ir_if_simplification_visitor()
+   {
+      /* empty */
+   }
+
+   /**
+    * \name Visit methods
+    *
+    * As typical for the visitor pattern, there must be one \c visit method for
+    * each concrete subclass of \c ir_instruction.  Virtual base classes within
+    * the hierarchy should not have \c visit methods.
+    */
+   /*@{*/
+   virtual void visit(ir_variable *);
+   virtual void visit(ir_label *);
+   virtual void visit(ir_loop *);
+   virtual void visit(ir_loop_jump *);
+   virtual void visit(ir_function_signature *);
+   virtual void visit(ir_function *);
+   virtual void visit(ir_expression *);
+   virtual void visit(ir_swizzle *);
+   virtual void visit(ir_dereference *);
+   virtual void visit(ir_assignment *);
+   virtual void visit(ir_constant *);
+   virtual void visit(ir_call *);
+   virtual void visit(ir_return *);
+   virtual void visit(ir_if *);
+   /*@}*/
+};
+
+bool
+do_if_simplification(exec_list *instructions)
+{
+   bool progress = false;
+
+   foreach_iter(exec_list_iterator, iter, *instructions) {
+      ir_instruction *ir = (ir_instruction *)iter.get();
+      ir_if *conditional = ir->as_if();
+
+      if (conditional) {
+	 ir_constant *condition_constant;
+
+	 condition_constant =
+	    conditional->condition->constant_expression_value();
+	 if (condition_constant) {
+	    /* Move the contents of the one branch of the conditional
+	     * that matters out.
+	     */
+	    if (condition_constant->value.b[0]) {
+	       foreach_iter(exec_list_iterator, then_iter,
+			    conditional->then_instructions) {
+		  ir_instruction *then_ir = (ir_instruction *)then_iter.get();
+		  ir->insert_before(then_ir);
+	       }
+	    } else {
+	       foreach_iter(exec_list_iterator, else_iter,
+			    conditional->else_instructions) {
+		  ir_instruction *else_ir = (ir_instruction *)else_iter.get();
+		  ir->insert_before(else_ir);
+	       }
+	    }
+	    ir->remove();
+	    progress = true;
+	    /* It would be nice to move the iterator back up to the point
+	     * that we just spliced in contents.
+	     */
+	 } else {
+	    ir_if_simplification_visitor v;
+	    ir->accept(&v);
+	 }
+      } else {
+	 ir_if_simplification_visitor v;
+	 ir->accept(&v);
+      }
+   }
+
+   return progress;
+}
+
+class variable_remap : public exec_node {
+public:
+   variable_remap(const ir_variable *old_var, ir_variable *new_var)
+      : old_var(old_var), new_var(new_var)
+   {
+      /* empty */
+   }
+   const ir_variable *old_var;
+   ir_variable *new_var;
+};
+
+void
+ir_if_simplification_visitor::visit(ir_variable *ir)
+{
+   (void) ir;
+}
+
+
+void
+ir_if_simplification_visitor::visit(ir_label *ir)
+{
+   ir->signature->accept(this);
+}
+
+void
+ir_if_simplification_visitor::visit(ir_loop *ir)
+{
+   do_if_simplification(&ir->body_instructions);
+}
+
+void
+ir_if_simplification_visitor::visit(ir_loop_jump *ir)
+{
+   (void) ir;
+}
+
+
+void
+ir_if_simplification_visitor::visit(ir_function_signature *ir)
+{
+   do_if_simplification(&ir->body);
+}
+
+
+void
+ir_if_simplification_visitor::visit(ir_function *ir)
+{
+   (void) ir;
+}
+
+void
+ir_if_simplification_visitor::visit(ir_expression *ir)
+{
+   unsigned int operand;
+
+   for (operand = 0; operand < ir->get_num_operands(); operand++) {
+      ir->operands[operand]->accept(this);
+   }
+}
+
+
+void
+ir_if_simplification_visitor::visit(ir_swizzle *ir)
+{
+   ir->val->accept(this);
+}
+
+
+void
+ir_if_simplification_visitor::visit(ir_dereference *ir)
+{
+   if (ir->mode == ir_dereference::ir_reference_array) {
+      ir->selector.array_index->accept(this);
+   }
+   ir->var->accept(this);
+}
+
+void
+ir_if_simplification_visitor::visit(ir_assignment *ir)
+{
+   ir->rhs->accept(this);
+}
+
+
+void
+ir_if_simplification_visitor::visit(ir_constant *ir)
+{
+   (void) ir;
+}
+
+
+void
+ir_if_simplification_visitor::visit(ir_call *ir)
+{
+   (void) ir;
+}
+
+
+void
+ir_if_simplification_visitor::visit(ir_return *ir)
+{
+   (void) ir;
+}
+
+
+void
+ir_if_simplification_visitor::visit(ir_if *ir)
+{
+   ir->condition->accept(this);
+
+   do_if_simplification(&ir->then_instructions);
+   do_if_simplification(&ir->else_instructions);
+}

ir_if_simplification.h

@@ -0,0 +1,31 @@
+/*
+ * 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_if_simplification.h
+ *
+ * Moves constant branches of if statements out to the surrounding
+ * instruction stream.
+ */
+
+bool do_if_simplification(exec_list *instructions);