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   6 <TITLE>The SUIF Version 1 Library - Miscellaneous Annotes</TITLE>
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  15
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  17 <H3><A NAME="SEC78" HREF="suif1_toc.html#TOC78">Miscellaneous Annotations</A></H3>
  18 <P>
  19 <A NAME="IDX573"></A>
  20 <A NAME="IDX574"></A>
  21 <A NAME="IDX575"></A>
  22 <A NAME="IDX576"></A>
  23
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  25 <P>
  26 The SUIF library defines a few other annotations to record various
  27 attributes of SUIF programs.  These are straightforward except for the
  28 <CODE>fields</CODE> annotation which is described here in more detail.
  29
  30 </P>
  31 <DL COMPACT>
  32
  33 <DT><CODE>k_line</CODE>
  34 <DD>
  35 <A NAME="IDX577"></A>
  36 This annotation records line numbers from the source code to be used
  37 when debugging the object code.  It is usually attached to a <CODE>mrk</CODE>
  38 instruction.  The first list entry is the integer line number and the
  39 second is the character string for the file name.
  40
  41 <DT><CODE>k_history</CODE>
  42 <DD>
  43 <A NAME="IDX578"></A>
  44 As each SUIF pass runs, the library automatically records the
  45 command-line for the pass as an annotation on the file set entries.
  46 These <CODE>history</CODE> annotations allow you to see how a particular SUIF
  47 file was generated.
  48
  49 <DT><CODE>k_enable_exceptions</CODE>
  50 <DD>
  51 <A NAME="IDX579"></A>
  52 This annotation is attached to a <CODE>proc_symtab</CODE> to indicate which
  53 run-time exceptions should be detected within that procedure.  The
  54 entries on the <CODE>immed</CODE> list are character strings.  The system
  55 currently recognizes <CODE>"int_divide-by-0"</CODE> and <CODE>"int_overflow"</CODE>.
  56 IEEE floating point exceptions need to be added.
  57
  58 <DT><CODE>k_reg_num</CODE>
  59 <DD>
  60 <A NAME="IDX580"></A>
  61 This annotation is attached to variables that represent machine
  62 registers to record the register numbers.  It has one immediate value
  63 which is the integer register number.  The meaning of the register
  64 numbers are machine-dependent.
  65
  66 <DT><CODE>k_fields</CODE>
  67 <DD>
  68 <A NAME="IDX581"></A>
  69 A field within a structure or union variable is specified in SUIF by a
  70 constant offset and a base address.  That is all that is needed to
  71 generate code.  However, if the offset is zero or if the variable is a
  72 union, that information is not sufficient to determine the field.  The
  73 <CODE>fields</CODE> annotation may be used to provide the field names that
  74 were used in the original source code.  The <CODE>immed</CODE> list for one of
  75 these annotations contains the names of the fields being accessed.
  76 (There may be multiple field names because of nested structures or
  77 unions.)
  78 </DL>
  79
  80 <P>
  81 The <CODE>fields</CODE> annotation is somewhat more complicated than the
  82 others.  The difficulty is in defining where this annotation should be
  83 used.  Intuitively, the <CODE>fields</CODE> annotation should be placed on
  84 the first instruction that produces a pointer to the field.  There are
  85 basically three different situations to consider.
  86
  87 </P>
  88 <P>
  89 In the simplest case, a field can be addressed directly with an
  90 <CODE>ldc</CODE> instruction (see section <A HREF="suif1_34.html#SEC34">Load Constant Instructions</A>).  Since that
  91 produces a pointer to the field, a <CODE>fields</CODE> annotation may be
  92 placed on the <CODE>ldc</CODE> instruction.  Of course, the entries on the
  93 annotation must be valid field names for the variable that is addressed.
  94
  95 </P>
  96 <P>
  97 To access a field of a structure or union variable that is referenced by
  98 a pointer, the constant offset must be included with an explicit
  99 <CODE>add</CODE> instruction.  Since the result of
 100 the addition is a pointer to the field, the <CODE>fields</CODE> annotation
 101 should be placed on the <CODE>add</CODE> instruction.  Note that if the field
 102 offset is zero, the <CODE>add</CODE> instruction may be replaced by a
 103 <CODE>cvt</CODE> instruction.  The same rule applies: the <CODE>cvt</CODE>
 104 instruction gets the <CODE>fields</CODE> annotation because it produces a
 105 pointer to the field.
 106
 107 </P>
 108 <P>
 109 For arrays of structures or unions, an <CODE>array</CODE> instruction
 110 (see section <A HREF="suif1_36.html#SEC36">Array Instructions</A>) may include a constant offset for a field
 111 within the array element being addressed, so this is another type of
 112 instruction that may include a <CODE>fields</CODE> annotation.  The entries on
 113 the <CODE>fields</CODE> annotation must be valid fields within the array
 114 element type.
 115
 116 </P>
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