sim/README-HACKING

   1 This is a loose collection of notes for people hacking on simulators.
   2 If this document gets big enough it can be prettied up then.
   3
   4 Contents
   5
   6 - The "common" directory
   7 - Common Makefile Support
   8 - TAGS support
   9 - Generating "configure" files
  10 - tconfig.in
  11 - C Language Assumptions
  12 - "dump" commands under gdb
  13 \f
  14 The "common" directory
  15 ======================
  16
  17 The common directory contains:
  18
  19 - common documentation files (e.g. run.1, and maybe in time .texi files)
  20 - common source files (e.g. run.c)
  21 - common Makefile fragment and configury (e.g. Make-common.in, aclocal.m4).
  22
  23 In addition "common" contains portions of the system call support
  24 (e.g. callback.c, nltvals.def).
  25
  26 Even though no files are built in this directory, it is still configured
  27 so support for regenerating nltvals.def is present.
  28 \f
  29 Common Makefile Support
  30 =======================
  31
  32 A common configuration framework is available for simulators that want
  33 to use it.  The common framework exists to remove a lot of duplication
  34 in configure.in and Makefile.in, and it also provides a foundation for
  35 enhancing the simulators uniformly (e.g. the more they share in common
  36 the easier a feature added to one is added to all).
  37
  38 The configure.in of a simulator using the common framework should look like:
  39
  40 --- snip ---
  41 dnl Process this file with autoconf to produce a configure script.
  42 AC_PREREQ(2.5)dnl
  43 AC_INIT(Makefile.in)
  44
  45 SIM_AC_COMMON
  46
  47 ... target specific additions ...
  48
  49 SIM_AC_OUTPUT
  50 --- snip ---
  51
  52 SIM_AC_COMMON:
  53
  54 - invokes the autoconf macros most often used by the simulators
  55 - defines --enable/--with options usable by all simulators
  56 - initializes sim_link_files/sim_link_links as the set of symbolic links
  57   to set up
  58
  59 SIM_AC_OUTPUT:
  60
  61 - creates the symbolic links defined in sim_link_{files,links}
  62 - creates config.h
  63 - creates the Makefile
  64
  65 The Makefile.in of a simulator using the common framework should look like:
  66
  67 --- snip ---
  68 # Makefile for blah ...
  69 # Copyright blah ...
  70
  71 ## COMMON_PRE_CONFIG_FRAG
  72
  73 # These variables are given default values in COMMON_PRE_CONFIG_FRAG.
  74 # We override the ones we need to here.
  75 # Not all of these need to be mentioned, only the necessary ones.
  76 # In fact it is better to *not* mention ones if the value is the default.
  77
  78 # List of object files, less common parts.
  79 SIM_OBJS =
  80 # List of extra dependencies.
  81 # Generally this consists of simulator specific files included by sim-main.h.
  82 SIM_EXTRA_DEPS =
  83 # List of flags to always pass to $(CC).
  84 SIM_EXTRA_CFLAGS =
  85 # List of extra libraries to link with.
  86 SIM_EXTRA_LIBS =
  87 # List of extra program dependencies.
  88 SIM_EXTRA_LIBDEPS =
  89 # List of main object files for `run'.
  90 SIM_RUN_OBJS = run.o
  91 # Dependency of `all' to build any extra files.
  92 SIM_EXTRA_ALL =
  93 # Dependency of `install' to install any extra files.
  94 SIM_EXTRA_INSTALL =
  95 # Dependency of `clean' to clean any extra files.
  96 SIM_EXTRA_CLEAN =
  97
  98 ## COMMON_POST_CONFIG_FRAG
  99
 100 # Rules need to build $(SIM_OBJS), plus whatever else the target wants.
 101
 102 ... target specific rules ...
 103 --- snip ---
 104
 105 COMMON_{PRE,POST}_CONFIG_FRAG are markers for SIM_AC_OUTPUT to tell it
 106 where to insert the two pieces of common/Make-common.in.
 107 The resulting Makefile is created by doing autoconf substitions on
 108 both the target's Makefile.in and Make-common.in, and inserting
 109 the two pieces of Make-common.in into the target's Makefile.in at
 110 COMMON_{PRE,POST}_CONFIG_FRAG.
 111
 112 Note that SIM_EXTRA_{INSTALL,CLEAN} could be removed and "::" targets
 113 could be used instead.  However, it's not clear yet whether "::" targets
 114 are portable enough.
 115 \f
 116 TAGS support
 117 ============
 118
 119 Many files generate program symbols at compile time.
 120 Such symbols can't be found with grep nor do they normally appear in
 121 the TAGS file.  To get around this, source files can add the comment
 122
 123 /* TAGS: foo1 foo2 */
 124
 125 where foo1, foo2 are program symbols.  Symbols found in such comments
 126 are greppable and appear in the TAGS file.
 127 \f
 128 Generating "configure" files
 129 ============================
 130
 131 For target's using the common framework, "configure" can be generated
 132 by running `autoconf -l ../common'.  This will ensure that the
 133 qaclocal.m4 from the `common' directory is found.
 134
 135 To regenerate the configure files for all targets using the common framework:
 136
 137         $  cd devo/sim
 138         $  make -f Makefile.in SHELL=/bin/sh autoconf-common
 139
 140 To add a change-log entry to the ChangeLog file for each updated
 141 directory (WARNING - check the modified new-ChangeLog files before
 142 renaming):
 143
 144         $  make -f Makefile.in SHELL=/bin/sh autoconf-changelog
 145         $  more */new-ChangeLog
 146         $  make -f Makefile.in SHELL=/bin/sh autoconf-install
 147
 148 In a similar vein, both the configure and config.in files can be
 149 updated using the sequence:
 150
 151         $  cd devo/sim
 152         $  make -f Makefile.in SHELL=/bin/sh autoheader-common
 153         $  make -f Makefile.in SHELL=/bin/sh autoheader-changelog
 154         $  more */new-ChangeLog
 155         $  make -f Makefile.in SHELL=/bin/sh autoheader-install
 156 \f
 157 tconfig.in
 158 ==========
 159
 160 File tconfig.in defines one or more target configuration macros
 161 (e.g. a tm.h file).  There are very few that need defining.
 162 For a list of all of them, see common/tconfig.in.
 163 It contains them all, commented out.
 164 The intent is that a new port can just copy this file and
 165 define the ones it needs.
 166 \f
 167 C Language Assumptions
 168 ======================
 169
 170 The programmer may assume that the simulator is being built using an
 171 ANSI C compiler that supports a 64 bit data type.  Consequently:
 172
 173         o       prototypes can be used (although using
 174                 PARAMS() and K&R declarations wouldn't
 175                 go astray).
 176
 177         o       If sim-types.h is included, the two
 178                 types signed64 and unsigned64 are
 179                 available.
 180
 181         o       The type `unsigned' is valid.
 182
 183 However, the user should be aware of the following:
 184
 185         o       GCC's `<number>LL' is NOT acceptable.
 186                 Microsoft-C doesn't reconize it.
 187
 188         o       MSC's `<number>i64' is NOT acceptable.
 189                 GCC doesn't reconize it.
 190
 191         o       GCC's `long long' MSC's `_int64' can
 192                 NOT be used to define 64 bit integer data
 193                 types.
 194
 195         o       An empty array (eg int a[0]) is not valid.
 196
 197 When building with GCC it is effectivly a requirement that
 198 --enable-sim-warnings be specified during configuration.
 199 \f
 200 "dump" commands under gdb
 201 =========================
 202
 203 gdbinit.in contains the following
 204
 205 define dump
 206 set sim_debug_dump ()
 207 end
 208
 209 Simulators that define the sim_debug_dump function can then have their
 210 internal state pretty printed from gdb.
 211
 212 FIXME: This can obviously be made more elaborate.  As needed it will be.
 213 \f
 214 "dump" commands under gdb
 215 =========================
 216
 217 gdbinit.in contains the following
 218
 219 define dump
 220 set sim_debug_dump ()
 221 end
 222
 223 Simulators that define the sim_debug_dump function can then have their
 224 internal state pretty printed from gdb.
 225
 226 FIXME: This can obviously be made more elaborate.  As needed it will be.