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   6 <TITLE>The SUIF Version 1 Library - ID Numbers</TITLE>
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  17 <H3><A NAME="SEC12" HREF="suif1_toc.html#TOC12">ID Numbers for Tree Nodes and Instructions</A></H3>
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  28 Within each procedure, the tree nodes and instructions are assigned
  29 unique ID numbers.  These numbers can be used to identify the nodes and
  30 instructions internally and in annotations that are written to the
  31 output files.  The <CODE>number</CODE> method retrieves the ID numbers.  It is
  32 generally best to avoid using the numbers on <CODE>tree_instr</CODE> nodes,
  33 because they are not written to the output files and the
  34 <CODE>tree_instr</CODE> nodes are automatically rearranged when converting
  35 between expression trees and flat lists of instructions.  Instead, use
  36 the ID numbers for the corresponding instructions.
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  43 The <CODE>number_instrs</CODE> method in the <CODE>tree_proc</CODE> class assigns ID
  44 numbers to tree nodes and instructions that do yet have numbers (i.e.
  45 those that were created since the procedure was read in).  This method
  46 is called automatically before each procedure is written out, but you
  47 may also call it whenever ID numbers are needed for new tree nodes or
  48 instructions.  The next unused ID number is recorded in the procedure
  49 symbol table.  In the <CODE>proc_symtab</CODE> class, the
  50 <CODE>next_instr_num</CODE> method returns the next ID number and increments
  51 the counter; the <CODE>instr_num</CODE> method returns the next number but
  52 does not increment the counter.  Since you can only assign new ID
  53 numbers with the <CODE>number_instrs</CODE> method, you will rarely, if ever,
  54 need to access this counter directly.
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  61 In some circumstances, the tree node and instruction ID numbers must be
  62 reset.  The most common case is when moving code from one procedure to
  63 another.  Since the ID numbers are only unique within each procedure,
  64 moving things between procedures is likely to create duplicate ID
  65 numbers.  To avoid this problem, the <CODE>tree_node</CODE>,
  66 <CODE>tree_node_list</CODE>, and <CODE>instruction</CODE> classes provide
  67 <CODE>clear_numbers</CODE> methods to reset the ID numbers.  These methods
  68 recursively descend the ASTs and expression trees to set all of the ID
  69 numbers within the object and its children to zero.
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