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  1. /* -*- c++ -*- */
  2. /*
  3.  * Copyright © 2010 Intel Corporation
  4.  *
  5.  * Permission is hereby granted, free of charge, to any person obtaining a
  6.  * copy of this software and associated documentation files (the "Software"),
  7.  * to deal in the Software without restriction, including without limitation
  8.  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  9.  * and/or sell copies of the Software, and to permit persons to whom the
  10.  * Software is furnished to do so, subject to the following conditions:
  11.  *
  12.  * The above copyright notice and this permission notice (including the next
  13.  * paragraph) shall be included in all copies or substantial portions of the
  14.  * Software.
  15.  *
  16.  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17.  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18.  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  19.  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20.  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  21.  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  22.  * DEALINGS IN THE SOFTWARE.
  23.  */
  24.  
  25. #pragma once
  26. #ifndef IR_HIERARCHICAL_VISITOR_H
  27. #define IR_HIERARCHICAL_VISITOR_H
  28.  
  29. /**
  30.  * Enumeration values returned by visit methods to guide processing
  31.  */
  32. enum ir_visitor_status {
  33.    visit_continue,              /**< Continue visiting as normal. */
  34.    visit_continue_with_parent,  /**< Don't visit siblings, continue w/parent. */
  35.    visit_stop                   /**< Stop visiting immediately. */
  36. };
  37.  
  38.  
  39. /**
  40.  * Base class of hierarchical visitors of IR instruction trees
  41.  *
  42.  * Hierarchical visitors differ from traditional visitors in a couple of
  43.  * important ways.  Rather than having a single \c visit method for each
  44.  * subclass in the composite, there are three kinds of visit methods.
  45.  * Leaf-node classes have a traditional \c visit method.  Internal-node
  46.  * classes have a \c visit_enter method, which is invoked just before
  47.  * processing child nodes, and a \c visit_leave method which is invoked just
  48.  * after processing child nodes.
  49.  *
  50.  * In addition, each visit method and the \c accept methods in the composite
  51.  * have a return value which guides the navigation.  Any of the visit methods
  52.  * can choose to continue visiting the tree as normal (by returning \c
  53.  * visit_continue), terminate visiting any further nodes immediately (by
  54.  * returning \c visit_stop), or stop visiting sibling nodes (by returning \c
  55.  * visit_continue_with_parent).
  56.  *
  57.  * These two changes combine to allow nagivation of children to be implemented
  58.  * in the composite's \c accept method.  The \c accept method for a leaf-node
  59.  * class will simply call the \c visit method, as usual, and pass its return
  60.  * value on.  The \c accept method for internal-node classes will call the \c
  61.  * visit_enter method, call the \c accpet method of each child node, and,
  62.  * finally, call the \c visit_leave method.  If any of these return a value
  63.  * other that \c visit_continue, the correct action must be taken.
  64.  *
  65.  * The final benefit is that the hierarchical visitor base class need not be
  66.  * abstract.  Default implementations of every \c visit, \c visit_enter, and
  67.  * \c visit_leave method can be provided.  By default each of these methods
  68.  * simply returns \c visit_continue.  This allows a significant reduction in
  69.  * derived class code.
  70.  *
  71.  * For more information about hierarchical visitors, see:
  72.  *
  73.  *    http://c2.com/cgi/wiki?HierarchicalVisitorPattern
  74.  *    http://c2.com/cgi/wiki?HierarchicalVisitorDiscussion
  75.  */
  76.  
  77. class ir_hierarchical_visitor {
  78. public:
  79.    ir_hierarchical_visitor();
  80.  
  81.    /**
  82.     * \name Visit methods for leaf-node classes
  83.     */
  84.    /*@{*/
  85.    virtual ir_visitor_status visit(class ir_variable *);
  86.    virtual ir_visitor_status visit(class ir_constant *);
  87.    virtual ir_visitor_status visit(class ir_loop_jump *);
  88.  
  89.    /**
  90.     * ir_dereference_variable isn't technically a leaf, but it is treated as a
  91.     * leaf here for a couple reasons.  By not automatically visiting the one
  92.     * child ir_variable node from the ir_dereference_variable, ir_variable
  93.     * nodes can always be handled as variable declarations.  Code that used
  94.     * non-hierarchical visitors had to set an "in a dereference" flag to
  95.     * determine how to handle an ir_variable.  By forcing the visitor to
  96.     * handle the ir_variable within the ir_dereference_variable visitor, this
  97.     * kludge can be avoided.
  98.     *
  99.     * In addition, I can envision no use for having separate enter and leave
  100.     * methods.  Anything that could be done in the enter and leave methods
  101.     * that couldn't just be done in the visit method.
  102.     */
  103.    virtual ir_visitor_status visit(class ir_dereference_variable *);
  104.    /*@}*/
  105.  
  106.    /**
  107.     * \name Visit methods for internal-node classes
  108.     */
  109.    /*@{*/
  110.    virtual ir_visitor_status visit_enter(class ir_loop *);
  111.    virtual ir_visitor_status visit_leave(class ir_loop *);
  112.    virtual ir_visitor_status visit_enter(class ir_function_signature *);
  113.    virtual ir_visitor_status visit_leave(class ir_function_signature *);
  114.    virtual ir_visitor_status visit_enter(class ir_function *);
  115.    virtual ir_visitor_status visit_leave(class ir_function *);
  116.    virtual ir_visitor_status visit_enter(class ir_expression *);
  117.    virtual ir_visitor_status visit_leave(class ir_expression *);
  118.    virtual ir_visitor_status visit_enter(class ir_texture *);
  119.    virtual ir_visitor_status visit_leave(class ir_texture *);
  120.    virtual ir_visitor_status visit_enter(class ir_swizzle *);
  121.    virtual ir_visitor_status visit_leave(class ir_swizzle *);
  122.    virtual ir_visitor_status visit_enter(class ir_dereference_array *);
  123.    virtual ir_visitor_status visit_leave(class ir_dereference_array *);
  124.    virtual ir_visitor_status visit_enter(class ir_dereference_record *);
  125.    virtual ir_visitor_status visit_leave(class ir_dereference_record *);
  126.    virtual ir_visitor_status visit_enter(class ir_assignment *);
  127.    virtual ir_visitor_status visit_leave(class ir_assignment *);
  128.    virtual ir_visitor_status visit_enter(class ir_call *);
  129.    virtual ir_visitor_status visit_leave(class ir_call *);
  130.    virtual ir_visitor_status visit_enter(class ir_return *);
  131.    virtual ir_visitor_status visit_leave(class ir_return *);
  132.    virtual ir_visitor_status visit_enter(class ir_discard *);
  133.    virtual ir_visitor_status visit_leave(class ir_discard *);
  134.    virtual ir_visitor_status visit_enter(class ir_if *);
  135.    virtual ir_visitor_status visit_leave(class ir_if *);
  136.    /*@}*/
  137.  
  138.  
  139.    /**
  140.     * Utility function to process a linked list of instructions with a visitor
  141.     */
  142.    void run(struct exec_list *instructions);
  143.  
  144.    /* Some visitors may need to insert new variable declarations and
  145.     * assignments for portions of a subtree, which means they need a
  146.     * pointer to the current instruction in the stream, not just their
  147.     * node in the tree rooted at that instruction.
  148.     *
  149.     * This is implemented by visit_list_elements -- if the visitor is
  150.     * not called by it, nothing good will happen.
  151.     */
  152.    class ir_instruction *base_ir;
  153.  
  154.    /**
  155.     * Callback function that is invoked on entry to each node visited.
  156.     *
  157.     * \warning
  158.     * Visitor classes derived from \c ir_hierarchical_visitor \b may \b not
  159.     * invoke this function.  This can be used, for example, to cause the
  160.     * callback to be invoked on every node type execpt one.
  161.     */
  162.    void (*callback)(class ir_instruction *ir, void *data);
  163.  
  164.    /**
  165.     * Extra data parameter passed to the per-node callback function
  166.     */
  167.    void *data;
  168.  
  169.    /**
  170.     * Currently in the LHS of an assignment?
  171.     *
  172.     * This is set and cleared by the \c ir_assignment::accept method.
  173.     */
  174.    bool in_assignee;
  175. };
  176.  
  177. void visit_tree(ir_instruction *ir,
  178.                 void (*callback)(class ir_instruction *ir, void *data),
  179.                 void *data);
  180.  
  181. ir_visitor_status visit_list_elements(ir_hierarchical_visitor *v, exec_list *l);
  182.  
  183. #endif /* IR_HIERARCHICAL_VISITOR_H */
  184.