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   9 <A HREF="#toc">Table of Contents</A><P>
  10
  11 <H2><A NAME="sect0" HREF="#toc0">Name</A></H2>
  12
  13 <P>
  14 snoot - translate pre-processed C to SUIF
  15
  16 <H2><A NAME="sect1" HREF="#toc1"><B>Synopsis</B></A></H2>
  17
  18 <P>
  19 <B>snoot</B> [ <I>options</I> ] <I>infile</I> <I>outfile</I>
  20
  21 <H2><A NAME="sect2" HREF="#toc2"><B>Description</B></A></H2>
  22
  23 <P>
  24 The <I>snoot</I> program is the core of the SUIF C front end. It
  25 translates from pre-processed ANSI-C to SUIF. The SUIF
  26 code that <I>snoot</I> produces is non-standard, however; it must
  27 be passed through <I>porky</I> with the <I>-defaults</I> flag before it
  28 becomes standard SUIF that other passes can handle.
  29 <P>
  30 The entire C front-end for SUIF consists of three passes.
  31 First, <I>cpp,</I> the ANSI-C pre-processor. This is not
  32 included with SUIF. Any standard ANSI-C pre-processor may
  33 be used; the gnu C pre-processor that is included with gcc
  34 is one option. The output of <I>cpp</I> is then fed into <I>snoot.</I>
  35 The output from <I>snoot</I> is the first SUIF file. Then the
  36 last stage is <I>porky</I> with the <I>-defaults</I> option. Together,
  37 these three passes turn ANSI-C into standard SUIF.
  38
  39 <H2><A NAME="sect3" HREF="#toc3"><B>Options</B></A></H2>
  40
  41
  42 <DL>
  43
  44 <DT><B>-W</B> </DT></DT>
  45 <DD>    Turn on more warning messages. By default, only
  46 important warnings are displayed. If used a second
  47 time, all possible warnings are issued.
  48 </DD>
  49
  50 <DT><B>-w</B> </DT></DT>
  51 <DD>    Suppress all warning messages. This overrides the
  52 <B>-W</B> option.
  53 </DD>
  54
  55 <DT><B>-keep-comments</B></DT></DT>
  56 <DD>
  57 Save all comments from the C code as \x01C comment"
  58 annotations on SUIF ``mrk'' instructions.    By
  59 default, comments are ignored.
  60 </DD>
  61 </DL>
  62 <P>
  63 Note that for this to have any effect, the C comments
  64 must have been preserved by the C pre-processor;
  65 by default <I>cpp</I> throws them away before <I>snoot</I>
  66 even sees the code. Use the <B>-C</B> option for <I>cpp</I> to
  67 save comments in the pre-processing stage.
  68
  69 <DL>
  70
  71 <DT><B>-ignore-comments</B></DT></DT>
  72 <DD>
  73 Do not save C comments. This is the default. If
  74 both <B>-keep-comments</B> and <B>-ignore-comments</B> are specified,
  75 the one that occurs latest on the command
  76 line takes effect.
  77 </DD>
  78
  79 <DT><B>-x</B> </DT></DT>
  80 <DD>    Write cross-reference of symbol uses as \x01source
  81 references\x02 annotations on the SUIF symbols. The
  82 location of each reference in the source file is
  83 recorded.
  84 </DD>
  85
  86 <DT><B>-P</B> </DT></DT>
  87 <DD>    Print function prototypes and global variable declarations
  88 to standard error. This output can be
  89 appended to the top of a source file so that the
  90 next time it's compiled more type checking can be
  91 done.
  92 </DD>
  93
  94 <DT><B>-s</B><I>density</I></DT></DT>
  95 <DD>
  96 Set the density of labels used as a cutoff for
  97 using SUIF mbr instructions instead of individual
  98 comparisons for switch statements. The <I>density</I> is
  99 interpreted as a floating point value. The default
 100 is 0.5, meaning that at least half the values in a
 101 range have to have case labels before an mbr
 102 instruction is used.
 103 </DD>
 104
 105 <DT><B>-e</B><I>n</I> </DT></DT>
 106 <DD>   Set the maximum number of error messages <I>snoot</I> will
 107 issue before giving up. The default is 20. Ordinarily,
 108 <I>snoot</I> will issue an error message and continue
 109 to look for more errors. Even if the rest of
 110 the program can successfully be translated, <I>snoot</I>
 111 will still return an error code. Once the limit is
 112 reached, <I>snoot</I> assumes that it is so hopelessly
 113 confused by earlier errors that there's no point in
 114 reporting any more.
 115 </DD>
 116
 117 <DT><B>-mark-execution-points</B></DT></DT>
 118 <DD>
 119 Put \x01sequence point\x02 annotations in the SUIF code
 120 corresponding to sequence points in the source
 121 code, when possible. Temporary values will be
 122 spilled into new variables if necessary. The one
 123 situation where sequence points are not properly
 124 inserted is for C ``for()'' statements that are
 125 translated into SUIF TREE_FOR nodes. There is no
 126 place on a SUIF TREE_FOR to put the sequence point
 127 that comes between evaluation of the incrementing
 128 expression and the test expression.
 129 </DD>
 130 </DL>
 131 <P>
 132 Sequence points are defined in the ANSI C standard
 133 as points in the execution where some things are
 134 guaranteed to have already been executed and others
 135 not yet executed. The standard defines exactly
 136 where they occur. The option of marking these in
 137 the SUIF code is provided in case later passes want
 138 to use them to print traces of variable values or
 139 something of that sort.
 140
 141 <DL>
 142
 143 <DT><B>-ignore-execution-points</B></DT></DT>
 144 <DD>
 145 Do not mark sequence points in the SUIF code. This
 146 is the default. If both <B>-mark-execution-points</B> and
 147 <B>-ignore-execution-points</B> are specified, the one
 148 that occurs latest on the command line takes
 149 effect.
 150 </DD>
 151
 152 <DT><B>-null-check</B></DT></DT>
 153 <DD>
 154 Insert code to check at runtime for a NULL pointer
 155 every time memory is explicitly read or written in
 156 the C code (i.e. for every use of the ``[]'',
 157 ``-&gt;'', or unary ``*'' operators). If a NULL
 158 pointer is found, an error message is issued giving
 159 the source line number and file and the program
 160 aborts.
 161 </DD>
 162
 163 <DT><B>-no-null-check</B></DT></DT>
 164 <DD>
 165 Do not insert code to check at runtime for NULL
 166 pointers. This is the default. If both <B>-nullcheck</B>
 167 and <B>-no-null-check</B> are specified, the one
 168 that occurs latest on the command line takes
 169 effect.
 170 </DD>
 171
 172 <DT><B>-T</B><I>target-name</I></DT></DT>
 173 <DD>
 174 Use the system-specific target parameters specified
 175 by <I>target-name</I> in compilation. This is used in
 176 cross-compilation or to generate code for a different
 177 back-end C compiler. The parameters include
 178 such things as the byte order of the machine, the
 179 sizes of the various types, and whether the type
 180 ``char'' is signed or unsigned. The default is to
 181 use the parameters from the C compiler used to
 182 build snoot (typically gcc).
 183 </DD>
 184 </DL>
 185 <P>
 186 To see a list of targets <I>snoot</I> understands, type
 187 <I>snoot</I> <I>-T-.</I> Target information is stored in the
 188 <I>snoot</I> source file <I>config.h.</I> See the <I>snoot</I> source
 189 file <I>find</I><B>_</B><I>params.c</I> for information on generating
 190 target information for new systems.
 191
 192 <DL>
 193
 194 <DT><B>-keep-typedef-info</B></DT></DT>
 195 <DD>
 196 Create dummy variables to represent typedef names.
 197 The dummy variables are given type ``int'' and have
 198 \x01typedef name\x02 annotations attached. The data on
 199 the annotation contains an immed list with one
 200 item, the type of the typedef.
 201 </DD>
 202
 203 <DT><B>-builtin</B> <I>builtin-name</I></DT></DT>
 204 <DD>
 205 Consider <I>builtin-name</I> to be a built-in identifier.
 206 That means that <I>builtin-name</I> can be used as a variable
 207 or followed by arguments in parentheses and
 208 each such expression will be translated to a SUIF
 209 generic instruction with <I>builtin-name</I> as its name.
 210 Within the parentheses can be a comma-separated
 211 argument list, where each argument can be a type, a
 212 string literal, or an expression. These generic
 213 instructions will be passed through most SUIF
 214 passes and <I>s2c</I> will translate them back into a form
 215 similar to their form in the original source code.
 216 This can be used to implement asm() directives, or
 217 built-in identifiers used for vararg macros in
 218 headers for some systems. Note that an alternative
 219 to specifying built-in identifiers on the commandline
 220 with this switch is to specify them in the
 221 configuration file \x01config.h".
 222 </DD>
 223
 224 <DT><B>-force-enum-is-int</B></DT></DT>
 225 <DD>
 226 Force all enum types to use type ``int'' as their
 227 equivalent type. Ordinarily, enum types are mapped
 228 to the smallest integer type that can contain all
 229 their enumeration constants. This option overrides
 230 that for compatibility, since some programs assume
 231 that the compiler maps enums only to ``int'' under
 232 all circumstances.
 233 </DD>
 234 </DL>
 235
 236 <H2><A NAME="sect4" HREF="#toc4"><B>History</B></A></H2>
 237
 238 <P>
 239 The first ANSI-C front-end for SUIF was <I>snout,</I> written by
 240 Robert French. It was based on <I>lcc,</I> a portable C frontend
 241 with a code-generation interface (see ``A Code Generation
 242 Interface for ANSI C'' by Fraser and Hanson). Since
 243 the back-end interface provided by <I>lcc</I> is too low-level
 244 for SUIF, some substantial changes were made in various
 245 levels of <I>lcc</I> code and data-structures to preserve more
 246 information when generating SUIF code.
 247 <P>
 248 When the SUIF system was overhauled, Todd Smith rewrote
 249 the SUIF-specific parts of <I>snout</I> to create <I>snoot</I> for new
 250 SUIF. When more changes were made to SUIF that required
 251 more information to be preserved that lcc was losing
 252 early-on, Chris Wilson rewrote <I>snoot.</I> Various internal
 253 transformations and datastructures used by lcc were
 254 removed. Now the front-end of lcc is used to generate
 255 SUIF code directly.
 256 <P>
 257
 258 <HR><P>
 259 <A NAME="toc"><B>Table of Contents</B></A><P>
 260 <UL>
 261 <LI><A NAME="toc0" HREF="#sect0">Name</A></LI>
 262 <LI><A NAME="toc1" HREF="#sect1">Synopsis</A></LI>
 263 <LI><A NAME="toc2" HREF="#sect2">Description</A></LI>
 264 <LI><A NAME="toc3" HREF="#sect3">Options</A></LI>
 265 <LI><A NAME="toc4" HREF="#sect4">History</A></LI>
 266 </UL>
 267 </BODY></HTML>