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   6 <TITLE>The SUIF Version 1 Library - Tree Node Lists</TITLE>
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  17 <H2><A NAME="SEC20" HREF="suif1_toc.html#TOC20">Tree Node Lists</A></H2>
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  26 A <CODE>tree_node_list</CODE> is a doubly-linked list of tree nodes, derived
  27 from the <CODE>dlist</CODE> class.  See section <A HREF="suif1_95.html#SEC95">Doubly-Linked Lists</A>.  Most nodes in
  28 an AST have their children recorded in tree node lists.  For example,
  29 the body of a block node is a tree node list.  Besides the standard list
  30 features, each tree node list includes a back-pointer to its parent tree
  31 node.  These pointers are maintained automatically by the SUIF library
  32 and can be accessed using the <CODE>parent</CODE> method.  In addition, each
  33 node on a tree node list contains pointers back to the list and the list
  34 element.  See section <A HREF="suif1_13.html#SEC13">Other Features Shared by All Tree Nodes</A>.  These pointers are set by the
  35 <CODE>set_elem</CODE> method (see section <A HREF="suif1_92.html#SEC92">Generic Lists</A>) which is automatically
  36 called every time an element is added to the list.
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  44 In a <CODE>tree_for</CODE> node, the lower bound, upper bound, and step value
  45 are usually treated as operands; however, the operands are actually
  46 stored as tree node lists.  See section <A HREF="suif1_17.html#SEC17">For Nodes</A>.  Each of these lists is
  47 required to contain a single expression with a dummy copy instruction at
  48 the root.  The destination of the dummy copy must be a null operand.
  49 The <CODE>tree_node_list</CODE> class includes several methods to handle these
  50 special lists.  The <CODE>is_op</CODE> method checks if the list consists of a
  51 single copy instruction with a null destination.  The <CODE>op</CODE> method
  52 retrieves the operand stored in the list.  If after converting the list
  53 to expression tree form, the <CODE>is_op</CODE> method returns <CODE>TRUE</CODE>,
  54 the <CODE>op</CODE> method returns the source operand of the dummy copy
  55 instruction; otherwise, an error occurs.  The <CODE>set_op</CODE> method is
  56 used to set the contents of the tree node list to a dummy copy
  57 instruction with the specified operand as its source.  The list must
  58 either be empty or already contain the dummy copy.  Finally, the
  59 <CODE>op_is_intconst</CODE> method checks if the operand in the tree node list
  60 is a constant integer, and if so, returns the value.
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  66 Tree node lists can easily be printed out as text.  The <CODE>print</CODE>
  67 method simply iterates through the list and calls the <CODE>print</CODE>
  68 method for each tree node.  The optional <CODE>depth</CODE> parameter
  69 specifies the indentation level to be used.  A separate method is used
  70 to print tree node lists that hold <CODE>tree_for</CODE> operands.  If the
  71 <CODE>is_op</CODE> method for one of these lists returns <CODE>TRUE</CODE>, the
  72 <CODE>print_expr</CODE> method prints the operand directly.  Otherwise, it
  73 prints the list as usual.
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