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authormarha <marha@users.sourceforge.net>2010-11-22 19:42:40 +0000
committermarha <marha@users.sourceforge.net>2010-11-22 19:42:40 +0000
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+/* -*- c++ -*- */
+/*
+ * 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.
+ */
+
+#pragma once
+#ifndef IR_HIERARCHICAL_VISITOR_H
+#define IR_HIERARCHICAL_VISITOR_H
+
+/**
+ * Enumeration values returned by visit methods to guide processing
+ */
+enum ir_visitor_status {
+ visit_continue, /**< Continue visiting as normal. */
+ visit_continue_with_parent, /**< Don't visit siblings, continue w/parent. */
+ visit_stop /**< Stop visiting immediately. */
+};
+
+
+/**
+ * Base class of hierarchical visitors of IR instruction trees
+ *
+ * Hierarchical visitors differ from traditional visitors in a couple of
+ * important ways. Rather than having a single \c visit method for each
+ * subclass in the composite, there are three kinds of visit methods.
+ * Leaf-node classes have a traditional \c visit method. Internal-node
+ * classes have a \c visit_enter method, which is invoked just before
+ * processing child nodes, and a \c visit_leave method which is invoked just
+ * after processing child nodes.
+ *
+ * In addition, each visit method and the \c accept methods in the composite
+ * have a return value which guides the navigation. Any of the visit methods
+ * can choose to continue visiting the tree as normal (by returning \c
+ * visit_continue), terminate visiting any further nodes immediately (by
+ * returning \c visit_stop), or stop visiting sibling nodes (by returning \c
+ * visit_continue_with_parent).
+ *
+ * These two changes combine to allow nagivation of children to be implemented
+ * in the composite's \c accept method. The \c accept method for a leaf-node
+ * class will simply call the \c visit method, as usual, and pass its return
+ * value on. The \c accept method for internal-node classes will call the \c
+ * visit_enter method, call the \c accpet method of each child node, and,
+ * finally, call the \c visit_leave method. If any of these return a value
+ * other that \c visit_continue, the correct action must be taken.
+ *
+ * The final benefit is that the hierarchical visitor base class need not be
+ * abstract. Default implementations of every \c visit, \c visit_enter, and
+ * \c visit_leave method can be provided. By default each of these methods
+ * simply returns \c visit_continue. This allows a significant reduction in
+ * derived class code.
+ *
+ * For more information about hierarchical visitors, see:
+ *
+ * http://c2.com/cgi/wiki?HierarchicalVisitorPattern
+ * http://c2.com/cgi/wiki?HierarchicalVisitorDiscussion
+ */
+
+class ir_hierarchical_visitor {
+public:
+ ir_hierarchical_visitor();
+
+ /**
+ * \name Visit methods for leaf-node classes
+ */
+ /*@{*/
+ virtual ir_visitor_status visit(class ir_variable *);
+ virtual ir_visitor_status visit(class ir_constant *);
+ virtual ir_visitor_status visit(class ir_loop_jump *);
+
+ /**
+ * ir_dereference_variable isn't technically a leaf, but it is treated as a
+ * leaf here for a couple reasons. By not automatically visiting the one
+ * child ir_variable node from the ir_dereference_variable, ir_variable
+ * nodes can always be handled as variable declarations. Code that used
+ * non-hierarchical visitors had to set an "in a dereference" flag to
+ * determine how to handle an ir_variable. By forcing the visitor to
+ * handle the ir_variable within the ir_dereference_variable visitor, this
+ * kludge can be avoided.
+ *
+ * In addition, I can envision no use for having separate enter and leave
+ * methods. Anything that could be done in the enter and leave methods
+ * that couldn't just be done in the visit method.
+ */
+ virtual ir_visitor_status visit(class ir_dereference_variable *);
+ /*@}*/
+
+ /**
+ * \name Visit methods for internal-node classes
+ */
+ /*@{*/
+ virtual ir_visitor_status visit_enter(class ir_loop *);
+ virtual ir_visitor_status visit_leave(class ir_loop *);
+ virtual ir_visitor_status visit_enter(class ir_function_signature *);
+ virtual ir_visitor_status visit_leave(class ir_function_signature *);
+ virtual ir_visitor_status visit_enter(class ir_function *);
+ virtual ir_visitor_status visit_leave(class ir_function *);
+ virtual ir_visitor_status visit_enter(class ir_expression *);
+ virtual ir_visitor_status visit_leave(class ir_expression *);
+ virtual ir_visitor_status visit_enter(class ir_texture *);
+ virtual ir_visitor_status visit_leave(class ir_texture *);
+ virtual ir_visitor_status visit_enter(class ir_swizzle *);
+ virtual ir_visitor_status visit_leave(class ir_swizzle *);
+ virtual ir_visitor_status visit_enter(class ir_dereference_array *);
+ virtual ir_visitor_status visit_leave(class ir_dereference_array *);
+ virtual ir_visitor_status visit_enter(class ir_dereference_record *);
+ virtual ir_visitor_status visit_leave(class ir_dereference_record *);
+ virtual ir_visitor_status visit_enter(class ir_assignment *);
+ virtual ir_visitor_status visit_leave(class ir_assignment *);
+ virtual ir_visitor_status visit_enter(class ir_call *);
+ virtual ir_visitor_status visit_leave(class ir_call *);
+ virtual ir_visitor_status visit_enter(class ir_return *);
+ virtual ir_visitor_status visit_leave(class ir_return *);
+ virtual ir_visitor_status visit_enter(class ir_discard *);
+ virtual ir_visitor_status visit_leave(class ir_discard *);
+ virtual ir_visitor_status visit_enter(class ir_if *);
+ virtual ir_visitor_status visit_leave(class ir_if *);
+ /*@}*/
+
+
+ /**
+ * Utility function to process a linked list of instructions with a visitor
+ */
+ void run(struct exec_list *instructions);
+
+ /* Some visitors may need to insert new variable declarations and
+ * assignments for portions of a subtree, which means they need a
+ * pointer to the current instruction in the stream, not just their
+ * node in the tree rooted at that instruction.
+ *
+ * This is implemented by visit_list_elements -- if the visitor is
+ * not called by it, nothing good will happen.
+ */
+ class ir_instruction *base_ir;
+
+ /**
+ * Callback function that is invoked on entry to each node visited.
+ *
+ * \warning
+ * Visitor classes derived from \c ir_hierarchical_visitor \b may \b not
+ * invoke this function. This can be used, for example, to cause the
+ * callback to be invoked on every node type execpt one.
+ */
+ void (*callback)(class ir_instruction *ir, void *data);
+
+ /**
+ * Extra data parameter passed to the per-node callback function
+ */
+ void *data;
+
+ /**
+ * Currently in the LHS of an assignment?
+ *
+ * This is set and cleared by the \c ir_assignment::accept method.
+ */
+ bool in_assignee;
+};
+
+void visit_tree(ir_instruction *ir,
+ void (*callback)(class ir_instruction *ir, void *data),
+ void *data);
+
+ir_visitor_status visit_list_elements(ir_hierarchical_visitor *v, exec_list *l);
+
+#endif /* IR_HIERARCHICAL_VISITOR_H */