[llvm] r214610 - Add a small utility called bisect that enables commandline bisecting on a counter.

[Chad Rosier]

Ah, very cool.  I've done something similar in the past to bisect
FastISel.  Specifically, I added a counter that would bail to the
SelectionDAGISel after N instructions in an attempt to identify
regressions.  This is just extends that idea to an automated tool for
finding the regression.

Thanks, Michael!

  Chad



> Sure. Lets assume that you are debugging InstCombine. You put a counter
> into InstCombine that is triggered by lets say the flag
> -max-instcombine-counter=<foo>
>
> Then you take the test case and run it for different values of N, stopping
> instcombine at N and while you are waiting, grab some coffee = ).
>
> Michael
>
> On Aug 1, 2014, at 6:54 PM, Chad Rosier <mcrosier at codeaurora.org> wrote:
>
>> Michael,
>> Can you provide a specific example of how this is used?  I'm sure it's a
>> very useful tool, but I still don't full understand it's utility.
>>
>> Chad
>>
>>> Author: mgottesman
>>> Date: Fri Aug  1 20:39:08 2014
>>> New Revision: 214610
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=214610&view=rev
>>> Log:
>>> Add a small utility called bisect that enables commandline bisecting on
>>> a
>>> counter.
>>>
>>> This is something that I have found to be very useful in my work and I
>>> wanted to contribute it back to the community since several people in
>>> the past have asked me for something along these lines. (Jakob, I know
>>> this has been a while coming ; )]
>>>
>>> The way you use this is you create a script that takes in as its first
>>> argument a count. The script passes into LLVM the count via a command
>>> line flag that disables a pass after LLVM has run after the pass has
>>> run for count number of times. Then the script invokes a test of some
>>> sort and indicates whether LLVM successfully compiled the test via the
>>> scripts exit status. Then you invoke bisect as follows:
>>>
>>> bisect --start=<start_num> --end=<end_num> ./script.sh "%(count)s"
>>>
>>> And bisect will continually call ./script.sh with various counts using
>>> the exit status to determine success and failure.
>>>
>>> Added:
>>>    llvm/trunk/utils/bisect   (with props)
>>>
>>> Added: llvm/trunk/utils/bisect
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/utils/bisect?rev=214610&view=auto
>>> ==============================================================================
>>> --- llvm/trunk/utils/bisect (added)
>>> +++ llvm/trunk/utils/bisect Fri Aug  1 20:39:08 2014
>>> @@ -0,0 +1,37 @@
>>> +#!/usr/bin/env python
>>> +
>>> +import os
>>> +import sys
>>> +import argparse
>>> +import subprocess
>>> +
>>> +parser = argparse.ArgumentParser()
>>> +
>>> +parser.add_argument('--start', type=int, default=0)
>>> +parser.add_argument('--end', type=int, default=(1 << 32))
>>> +parser.add_argument('command', nargs='+')
>>> +
>>> +args = parser.parse_args()
>>> +
>>> +start = args.start
>>> +end = args.end
>>> +
>>> +print("Bisect Starting!")
>>> +print("Start: %d" % start)
>>> +print("End: %d" % end)
>>> +
>>> +last = None
>>> +while start != end and start != end-1:
>>> +    count = start + (end - start)/2
>>> +    print("Visiting Count: %d with (Start, End) = (%d,%d)" % (count,
>>> start, end))
>>> +    cmd = [x % {'count':count} for x in args.command]
>>> +    print cmd
>>> +    result = subprocess.call(cmd)
>>> +    if result == 0:
>>> +        print("    PASSES! Setting start to count")
>>> +        start = count
>>> +    else:
>>> +        print("    FAILS! Setting end to count")
>>> +        end = count
>>> +
>>> +print("Last good count: %d" % start)
>>>
>>> Propchange: llvm/trunk/utils/bisect
>>> ------------------------------------------------------------------------------
>>>    svn:executable = *
>>>
>>>
>>> _______________________________________________
>>> llvm-commits mailing list
>>> llvm-commits at cs.uiuc.edu
>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>>>
>>
>>
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>>
>
>


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