ir_vec_index_to_swizzle: Pass to convert indexing of vectors to swizzles.

This should remove the burden of handling constant vector indexing
well from backend codegen, and could help with swizzle optimizations.

Makefile.am

@@ -47,7 +47,8 @@ glsl_SOURCES = \
 	ir_reader.cpp s_expression.cpp \
 	ir_hv_accept.cpp \
 	ir_hierarchical_visitor.h \
-	ir_hierarchical_visitor.cpp
+	ir_hierarchical_visitor.cpp \
+	ir_vec_index_to_swizzle.cpp
 
 BUILT_SOURCES = glsl_parser.h glsl_parser.cpp glsl_lexer.cpp
 CLEANFILES = $(BUILT_SOURCES)

glsl_parser_extras.cpp

@@ -759,6 +759,7 @@ main(int argc, char **argv)
 	 progress = do_dead_code_local(&instructions) || progress;
 	 progress = do_dead_code_unlinked(&instructions) || progress;
 	 progress = do_constant_folding(&instructions) || progress;
+	 progress = do_vec_index_to_swizzle(&instructions) || progress;
       } while (progress);
    }
 

ir.h

@@ -56,6 +56,7 @@ public:
    virtual class ir_variable *          as_variable()         { return NULL; }
    virtual class ir_function *          as_function()         { return NULL; }
    virtual class ir_dereference *       as_dereference()      { return NULL; }
+   virtual class ir_dereference_array *	as_dereference_array() { return NULL; }
    virtual class ir_rvalue *            as_rvalue()           { return NULL; }
    virtual class ir_label *             as_label()            { return NULL; }
    virtual class ir_loop *              as_loop()             { return NULL; }
@@ -685,7 +686,6 @@ public:
 
    virtual ir_visitor_status accept(ir_hierarchical_visitor *);
 
-private:
    ir_rvalue *value;
 };
 
@@ -860,6 +860,11 @@ public:
 
    ir_dereference_array(ir_variable *var, ir_rvalue *array_index);
 
+   virtual ir_dereference_array *as_dereference_array()
+   {
+      return this;
+   }
+
    /**
     * Get the variable that is ultimately referenced by an r-value
     */

ir_optimization.h

@@ -35,3 +35,4 @@ bool do_dead_code_local(exec_list *instructions);
 bool do_dead_code_unlinked(exec_list *instructions);
 bool do_function_inlining(exec_list *instructions);
 bool do_if_simplification(exec_list *instructions);
+bool do_vec_index_to_swizzle(exec_list *instructions);

ir_vec_index_to_swizzle.cpp

@@ -0,0 +1,166 @@
+/*
+ * 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_vec_index_to_swizzle.cpp
+ *
+ * Turns constant indexing into vector types to swizzles.  This will
+ * let other swizzle-aware optimization passes catch these constructs,
+ * and codegen backends not have to worry about this case.
+ */
+
+#include <stdio.h>
+#include "ir.h"
+#include "ir_visitor.h"
+#include "ir_optimization.h"
+#include "ir_print_visitor.h"
+#include "glsl_types.h"
+
+/**
+ * Visitor class for replacing expressions with ir_constant values.
+ */
+
+class ir_vec_index_to_swizzle_visitor : public ir_hierarchical_visitor {
+public:
+   ir_vec_index_to_swizzle_visitor()
+   {
+      progress = false;
+   }
+
+   ir_rvalue *convert_vec_index_to_swizzle(ir_rvalue *val);
+
+   virtual ir_visitor_status visit_enter(ir_expression *);
+   virtual ir_visitor_status visit_enter(ir_swizzle *);
+   virtual ir_visitor_status visit_enter(ir_assignment *);
+   virtual ir_visitor_status visit_enter(ir_return *);
+   virtual ir_visitor_status visit_enter(ir_call *);
+   virtual ir_visitor_status visit_enter(ir_if *);
+
+   bool progress;
+};
+
+ir_rvalue *
+ir_vec_index_to_swizzle_visitor::convert_vec_index_to_swizzle(ir_rvalue *ir)
+{
+   ir_dereference_array *deref = ir->as_dereference_array();
+   ir_constant *ir_constant;
+   ir_rvalue *deref_var;
+
+   if (!deref)
+      return ir;
+
+   if (deref->array->type->is_matrix() || deref->array->type->is_array())
+      return ir;
+
+   deref_var = deref->array->as_rvalue();
+   if (!deref_var) {
+      ir_variable *var = deref->array->as_variable();
+      assert(var);
+      deref_var = new ir_dereference_variable(var);
+   }
+
+   assert(deref->array_index->type->base_type == GLSL_TYPE_INT);
+   ir_constant = deref->array_index->constant_expression_value();
+   if (!ir_constant)
+      return ir;
+
+   this->progress = true;
+   return new ir_swizzle(deref_var, ir_constant->value.i[0], 0, 0, 0, 1);
+}
+
+ir_visitor_status
+ir_vec_index_to_swizzle_visitor::visit_enter(ir_expression *ir)
+{
+   unsigned int i;
+
+   for (i = 0; i < ir->get_num_operands(); i++) {
+      ir->operands[i] = convert_vec_index_to_swizzle(ir->operands[i]);
+   }
+
+   return visit_continue;
+}
+
+ir_visitor_status
+ir_vec_index_to_swizzle_visitor::visit_enter(ir_swizzle *ir)
+{
+   /* Can't be hit from normal GLSL, since you can't swizzle a scalar (which
+    * the result of indexing a vector is.  But maybe at some point we'll end up
+    * using swizzling of scalars for vector construction.
+    */
+   ir->val = convert_vec_index_to_swizzle(ir->val);
+
+   return visit_continue;
+}
+
+ir_visitor_status
+ir_vec_index_to_swizzle_visitor::visit_enter(ir_assignment *ir)
+{
+   ir->lhs = convert_vec_index_to_swizzle(ir->lhs);
+   ir->rhs = convert_vec_index_to_swizzle(ir->rhs);
+
+   return visit_continue;
+}
+
+ir_visitor_status
+ir_vec_index_to_swizzle_visitor::visit_enter(ir_call *ir)
+{
+   foreach_iter(exec_list_iterator, iter, *ir) {
+      ir_rvalue *param = (ir_rvalue *)iter.get();
+      ir_rvalue *new_param = convert_vec_index_to_swizzle(param);
+
+      if (new_param != param) {
+	 param->insert_before(new_param);
+	 param->remove();
+      }
+   }
+
+   return visit_continue;
+}
+
+ir_visitor_status
+ir_vec_index_to_swizzle_visitor::visit_enter(ir_return *ir)
+{
+   if (ir->value) {
+      ir->value = convert_vec_index_to_swizzle(ir->value);
+   }
+
+   return visit_continue;
+}
+
+ir_visitor_status
+ir_vec_index_to_swizzle_visitor::visit_enter(ir_if *ir)
+{
+   ir->condition = convert_vec_index_to_swizzle(ir->condition);
+
+   return visit_continue;
+}
+
+bool
+do_vec_index_to_swizzle(exec_list *instructions)
+{
+   ir_vec_index_to_swizzle_visitor v;
+
+   v.run(instructions);
+
+   return false;
+}