gcc/dbgcnt.def

   1 /* This file contains the list of the debug counter for GCC.
   2    Copyright (C) 2006, 2007, 2008 Free Software Foundation, Inc.
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify it under
   7 the terms of the GNU General Public License as published by the Free
   8 Software Foundation; either version 3, or (at your option) any later
   9 version.
  10
  11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14 for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GCC; see the file COPYING3.  If not see
  18 <http://www.gnu.org/licenses/>.  */
  19
  20
  21 /* A debug counter provides you a way to count an event
  22    and return false after the counter has exceeded the threshold
  23    specified by the option.
  24
  25    What is it used for ?
  26
  27    This is primarily used to speed up the search for the bad transformation
  28    an optimization pass does. By doing a binary search on N,
  29    you can quickly narrow down to one transformation
  30    which is bad, or which triggers the bad behavior downstream
  31    (usually in the form of the badly generated code).
  32
  33    How does it work ?
  34
  35    Every time dbg_cnt(named-counter) is called,
  36    the counter is incremented for the named-counter.
  37    And the incremented value is compared against the threshold (limit)
  38    specified by the option.
  39    dbg_cnt () returns true if it is at or below threshold, and false if above.
  40
  41    How to add a new one ?
  42
  43    To add a new counter, simply add an entry below with some descriptive name,
  44    and add call(s) to dbg_cnt(your-counter-name) in appropriate places.
  45    Usually, you want to control at the finest granularity
  46    any particular transformation can happen.
  47    e.g. for each instruction in a dead code elimination,
  48    or for each copy instruction in register coalescing,
  49    or constant-propagation for each insn,
  50    or a block straightening, etc.
  51    See dce.c for an example. With the dbg_cnt () call in dce.c,
  52    now a developer can use -fdbg-cnt=dce:N
  53    to stop doing the dead code elimination after N times.
  54
  55    How to use it ?
  56
  57    By default, all limits are UINT_MAX.
  58    Since debug count is unsigned int, <= UINT_MAX returns true always.
  59    i.e.  dbg_cnt() returns true always regardless of the counter value
  60    (although it still counts the event).
  61    Use -fdbg-cnt=counter1:N,counter2:M,...
  62    which sets the limit for counter1 to N, and the limit for counter2 to M, etc.
  63    e.g. setting a limit to zero will make dbg_cnt () return false *always*.
  64
  65    The following shell file can then be used to binary search for
  66    exact transformation that causes the bug.  A second shell script
  67    should be written, say "tryTest", which exits with 1 if the
  68    compiled program fails and exits with 0 if the program succeeds.
  69    This shell script should take 1 parameter, the value to be passed
  70    to set the counter of the compilation command in tryTest.  Then,
  71    assuming that the following script is called binarySearch,
  72    the command:
  73
  74         binarySearch tryTest
  75
  76    will automatically find the highest value of the counter for which
  77    the program fails.  If tryTest never fails, binarySearch will
  78    produce unpredictable results as it will try to find an upper bound
  79    that does not exist.
  80
  81    When dbgcnt does hits the limit, it writes a comment in the current
  82    dump_file of the form:
  83
  84        ***dbgcnt: limit reached for %s.***
  85
  86    Assuming that the dump file is logging the analysis/transformations
  87    it is making, this pinpoints the exact position in the log file
  88    where the problem transformation is being logged.
  89
  90 =====================================
  91 #!/bin/bash
  92
  93 while getopts "l:u:i:" opt
  94 do
  95     case $opt in
  96         l) lb="$OPTARG";;
  97         u) ub="$OPTARG";;
  98         i) init="$OPTARG";;
  99         ?) usage; exit 3;;
 100     esac
 101 done
 102
 103 shift $(($OPTIND - 1))
 104 echo $@
 105 cmd=${1+"${@}"}
 106
 107 lb=${lb:=0}
 108 init=${init:=100}
 109
 110 $cmd $lb
 111 lb_val=$?
 112 if [ -z "$ub" ]; then
 113     # find the upper bound
 114     ub=$(($init + $lb))
 115     true
 116     while [ $? -eq $lb_val ]; do
 117         ub=$(($ub * 10))
 118         #ub=`expr $ub \* 10`
 119         $cmd $ub
 120     done
 121 fi
 122
 123 echo command: $cmd
 124
 125 true
 126 while [ `expr $ub - $lb` -gt 1 ]; do
 127     try=$(($lb + ( $ub - $lb ) / 2))
 128     $cmd $try
 129     if [ $? -eq $lb_val ]; then
 130         lb=$try
 131     else
 132         ub=$try
 133     fi
 134 done
 135
 136 echo lbound: $lb
 137 echo ubound: $ub
 138
 139 =====================================
 140
 141 */
 142
 143 /* Debug counter definitions.  */
 144 DEBUG_COUNTER (auto_inc_dec)
 145 DEBUG_COUNTER (ccp)
 146 DEBUG_COUNTER (cfg_cleanup)
 147 DEBUG_COUNTER (cse2_move2add)
 148 DEBUG_COUNTER (cprop)
 149 DEBUG_COUNTER (dce)
 150 DEBUG_COUNTER (dce_fast)
 151 DEBUG_COUNTER (dce_ud)
 152 DEBUG_COUNTER (delete_trivial_dead)
 153 DEBUG_COUNTER (df_byte_scan)
 154 DEBUG_COUNTER (dse)
 155 DEBUG_COUNTER (dse1)
 156 DEBUG_COUNTER (dse2)
 157 DEBUG_COUNTER (gcse2_delete)
 158 DEBUG_COUNTER (global_alloc_at_func)
 159 DEBUG_COUNTER (global_alloc_at_reg)
 160 DEBUG_COUNTER (hoist)
 161 DEBUG_COUNTER (ia64_sched2)
 162 DEBUG_COUNTER (if_conversion)
 163 DEBUG_COUNTER (if_after_combine)
 164 DEBUG_COUNTER (if_after_reload)
 165 DEBUG_COUNTER (local_alloc_for_sched)
 166 DEBUG_COUNTER (postreload_cse)
 167 DEBUG_COUNTER (pre)
 168 DEBUG_COUNTER (pre_insn)
 169 DEBUG_COUNTER (treepre_insert)
 170 DEBUG_COUNTER (sched2_func)
 171 DEBUG_COUNTER (sched_block)
 172 DEBUG_COUNTER (sched_func)
 173 DEBUG_COUNTER (sched_insn)
 174 DEBUG_COUNTER (sched_region)
 175 DEBUG_COUNTER (sel_sched_cnt)
 176 DEBUG_COUNTER (sel_sched_region_cnt)
 177 DEBUG_COUNTER (sel_sched_insn_cnt)
 178 DEBUG_COUNTER (sms_sched_loop)
 179 DEBUG_COUNTER (store_motion)
 180 DEBUG_COUNTER (split_for_sched2)
 181 DEBUG_COUNTER (tail_call)