html/suif1_14.html

   1 <HTML>
   2 <HEAD>
   3 <!-- This HTML file has been created by texi2html 1.54
   4      from suif1.texi on 28 April 1999 -->
   5
   6 <TITLE>The SUIF Version 1 Library - Instruction Nodes</TITLE>
   7 <link href="suif1_15.html" rel=Next>
   8 <link href="suif1_13.html" rel=Previous>
   9 <link href="suif1_toc.html" rel=ToC>
  10
  11 </HEAD>
  12 <BODY>
  13 <p>Go to the <A HREF="suif1_1.html">first</A>, <A HREF="suif1_13.html">previous</A>, <A HREF="suif1_15.html">next</A>, <A HREF="suif1_113.html">last</A> section, <A HREF="suif1_toc.html">table of contents</A>.
  14 <P><HR><P>
  15
  16
  17 <H3><A NAME="SEC14" HREF="suif1_toc.html#TOC14">Instruction Nodes</A></H3>
  18 <P>
  19 <A NAME="IDX44"></A>
  20 <A NAME="IDX45"></A>
  21 <A NAME="IDX46"></A>
  22
  23 </P>
  24 <P>
  25 <A NAME="IDX47"></A>
  26 <A NAME="IDX48"></A>
  27 <A NAME="IDX49"></A>
  28 <A NAME="IDX50"></A>
  29 Instruction nodes, implemented by the <CODE>tree_instr</CODE> class, are the
  30 leaves of the abstract syntax trees.  Each instruction node contains a
  31 single instruction or expression tree which can be accessed using the
  32 <CODE>instr</CODE> method.  The <CODE>set_instr</CODE> method attaches an
  33 instruction to a <CODE>tree_instr</CODE>, and the <CODE>remove_instr</CODE> method
  34 detaches an instruction.  Note that <CODE>remove_instr</CODE> does not free
  35 the storage for the instruction, and unlike the <CODE>remove</CODE> method in
  36 the <CODE>instruction</CODE> class (see section <A HREF="suif1_28.html#SEC28">Source Operands</A>), it does not
  37 remove the instruction from its expression tree.  Conversely, removing
  38 an instruction from an expression tree with the <CODE>remove</CODE> method
  39 will automatically call <CODE>remove_instr</CODE> if necessary.
  40
  41 </P>
  42 <P>
  43 The SUIF library automatically maintains back-pointers from instructions
  44 to their parent <CODE>tree_instr</CODE> nodes.  As a result, the
  45 <CODE>set_instr</CODE> and <CODE>remove_instr</CODE> methods must always be used to
  46 attach and detach instructions to <CODE>tree_instr</CODE> nodes.  Never use
  47 the instruction in a <CODE>tree_instr</CODE> elsewhere without first calling
  48 <CODE>remove_instr</CODE>, and never use <CODE>set_instr</CODE> with a
  49 <CODE>tree_instr</CODE> that already contains an instruction.
  50
  51 </P>
  52 <P>
  53 Unlike other tree nodes, instruction nodes are considered temporary
  54 objects.  They are destroyed and created automatically by the SUIF
  55 library when switching between expression trees and flat lists, and
  56 their annotations and ID numbers are not written to the output files.
  57 Consequently, annotations should generally not be attached to them but
  58 should instead be placed directly on the instructions.
  59
  60 </P>
  61 <P>
  62 The destructor for the <CODE>tree_instr</CODE> class also deletes the
  63 instruction or expression tree contained in the node.  This is the
  64 desired behavior for most cases.  However, if you only want to delete
  65 the <CODE>tree_instr</CODE> node, simply call <CODE>remove_instr</CODE> first and
  66 save a pointer to the instruction.
  67
  68 </P>
  69 <P>
  70 <A NAME="IDX51"></A>
  71 <A NAME="IDX52"></A>
  72 Often in SUIF one needs to perform some operation on all the
  73 instructions in a procedure.  The <CODE>map</CODE> methods in the
  74 <CODE>tree_node</CODE> and <CODE>tree_node_list</CODE> classes (see section <A HREF="suif1_21.html#SEC21">Mapping Functions Over Subtrees</A>) make it easy to visit all of the instruction nodes.  Once an
  75 instruction node is reached, its <CODE>instr_map</CODE> method may be used to
  76 apply a function to every instruction in the associated expression tree.
  77 Given a function of type <CODE>instr_map_f</CODE>, <CODE>instr_map</CODE> will
  78 traverse the expression tree and apply the function to every
  79 instruction.  The <CODE>preorder</CODE> parameter is used to select either
  80 preorder or postorder traversals; the default is preorder.  The
  81 <CODE>instr_map_f</CODE> function takes two arguments: the instruction pointer
  82 and a <CODE>void*</CODE> value that you provide to <CODE>instr_map</CODE>.
  83
  84 </P>
  85
  86 <P><HR><P>
  87 <p>Go to the <A HREF="suif1_1.html">first</A>, <A HREF="suif1_13.html">previous</A>, <A HREF="suif1_15.html">next</A>, <A HREF="suif1_113.html">last</A> section, <A HREF="suif1_toc.html">table of contents</A>.
  88 </BODY>
  89 </HTML>