#include "dbgcnt.def"

Include dependency graph for dbgcnt.h:

Macros
#define	DEBUG_COUNTER(a) a,

Enumerations
enum	debug_counter { DEBUG_COUNTER }

Functions
bool	dbg_cnt_is_enabled (enum debug_counter index)
bool	dbg_cnt (enum debug_counter index)
void	dbg_cnt_process_opt (const char *arg)
void	dbg_cnt_list_all_counters (void)

Macro Definition Documentation

#define DEBUG_COUNTER ( a ) a,

@verbatim

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with GCC; see the file COPYING3. If not see http://www.gnu.org/licenses/.

See dbgcnt.def for usage information.

Enumeration Type Documentation

enum debug_counter

Enumerator:

DEBUG_COUNTER

@verbatim

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with GCC; see the file COPYING3. If not see http://www.gnu.org/licenses/.

   A debug counter provides you a way to count an event
   and return false after the counter has exceeded the threshold
   specified by the option.

   What is it used for ?

   This is primarily used to speed up the search for the bad transformation
   an optimization pass does. By doing a binary search on N,
   you can quickly narrow down to one transformation
   which is bad, or which triggers the bad behavior downstream
   (usually in the form of the badly generated code).

   How does it work ?

   Every time dbg_cnt(named-counter) is called,
   the counter is incremented for the named-counter.
   And the incremented value is compared against the threshold (limit)
   specified by the option.
   dbg_cnt () returns true if it is at or below threshold, and false if above.

   How to add a new one ?

   To add a new counter, simply add an entry below with some descriptive name,
   and add call(s) to dbg_cnt(your-counter-name) in appropriate places.
   Usually, you want to control at the finest granularity
   any particular transformation can happen.
   e.g. for each instruction in a dead code elimination,
   or for each copy instruction in register coalescing,
   or constant-propagation for each insn,
   or a block straightening, etc.
   See dce.c for an example. With the dbg_cnt () call in dce.c,
   now a developer can use -fdbg-cnt=dce:N
   to stop doing the dead code elimination after N times.

   How to use it ?

   By default, all limits are UINT_MAX.
   Since debug count is unsigned int, <= UINT_MAX returns true always.
   i.e.  dbg_cnt() returns true always regardless of the counter value
   (although it still counts the event).
   Use -fdbg-cnt=counter1:N,counter2:M,...
   which sets the limit for counter1 to N, and the limit for counter2 to M, etc.
   e.g. setting a limit to zero will make dbg_cnt () return false *always*.

   The following shell file can then be used to binary search for
   exact transformation that causes the bug.  A second shell script
   should be written, say "tryTest", which exits with 1 if the
   compiled program fails and exits with 0 if the program succeeds.
   This shell script should take 1 parameter, the value to be passed
   to set the counter of the compilation command in tryTest.  Then,
   assuming that the following script is called binarySearch,
   the command:

        binarySearch tryTest

   will automatically find the highest value of the counter for which
   the program fails.  If tryTest never fails, binarySearch will
   produce unpredictable results as it will try to find an upper bound
   that does not exist.

   When dbgcnt does hits the limit, it writes a comment in the current
   dump_file of the form:

       ***dbgcnt: limit reached for %s.***

   Assuming that the dump file is logging the analysis/transformations
   it is making, this pinpoints the exact position in the log file
   where the problem transformation is being logged.

=====================================
#!/bin/bash

while getopts "l:u:i:" opt
do
    case $opt in
        l) lb="$OPTARG";;
        u) ub="$OPTARG";;
        i) init="$OPTARG";;
        ?) usage; exit 3;;
    esac
done

shift $(($OPTIND - 1))
echo $@
cmd=${1+"${@}"}

lb=${lb:=0}
init=${init:=100}

$cmd $lb
lb_val=$?
if [ -z "$ub" ]; then
    # find the upper bound
    ub=$(($init + $lb))
    true
    while [ $? -eq $lb_val ]; do
        ub=$(($ub * 10))
        #ub=`expr $ub \* 10`
        $cmd $ub
    done
fi

echo command: $cmd

true
while [ `expr $ub - $lb` -gt 1 ]; do
    try=$(($lb + ( $ub - $lb ) / 2))
    $cmd $try
    if [ $? -eq $lb_val ]; then
        lb=$try
    else
        ub=$try
    fi
done

echo lbound: $lb
echo ubound: $ub

=====================================

   Debug counter definitions.

Function Documentation

bool dbg_cnt ( enum debug_counter index )

bool dbg_cnt_is_enabled ( enum debug_counter index )

void dbg_cnt_list_all_counters ( void )

   Print name, limit and count of all counters.

void dbg_cnt_process_opt ( const char * arg )

Macros

Enumerations

Functions

Macro Definition Documentation

Enumeration Type Documentation

Function Documentation