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   6 <TITLE>The SUIF Version 1 Library - Multi-way Branch Instructions</TITLE>
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  17 <H2><A NAME="SEC37" HREF="suif1_toc.html#TOC37">Multi-way Branch Instructions</A></H2>
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  25 Fortran computed <CODE>goto</CODE> statements and C <CODE>switch</CODE> statements
  26 are represented in SUIF by multi-way branch (<CODE>mbr</CODE>) instructions.
  27 These are easier to analyze than the equivalent series of conditional
  28 branches, and they can easily be used to generate efficient jump table
  29 code.  The <CODE>in_mbr</CODE> class holds these multi-way branch
  30 instructions.
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  38 The <CODE>in_mbr</CODE> class contains a field with a pointer to an array of
  39 label symbols.  The <CODE>num_labs</CODE> method returns the number of labels
  40 in the array.  The size of the array can be changed at any time using
  41 the <CODE>set_num_labs</CODE> method; if necessary the array will be
  42 reallocated.  A particular element within the array can be accessed
  43 using the <CODE>label</CODE> and <CODE>set_label</CODE> methods.  You must specify
  44 the array index, and, as usual, the elements are numbered beginning with
  45 zero.
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  55 A multi-way branch instruction transfers control to one of the target
  56 labels depending on the value in the source operand.  This operand must
  57 have an integer type.  It can be accessed using the <CODE>src_op</CODE> and
  58 <CODE>set_src</CODE> methods.  The value of the source operand is combined
  59 with an integer offset to determine the target label.  The offset can be
  60 accessed with the <CODE>lower</CODE> and <CODE>set_lower</CODE> methods.  The offset
  61 is subtracted from the value in the source operand and the result is
  62 used to index into the array of target labels.  If the index is within
  63 the range of the array, the instruction branches to the label at that
  64 position in the array; otherwise, it branches to the default target
  65 label.  The <CODE>default_lab</CODE> and <CODE>set_default_lab</CODE> methods access
  66 this default label field.  The destination operand of a multi-way branch
  67 is unused and trying to set it will cause an error.  The result type
  68 should always be the SUIF <CODE>void</CODE> type.
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