[Bug bootstrap/63432] [5 Regression] profiledbootstrap failure with bootstrap-lto

tejohnson at google dot com gcc-bugzilla@gcc.gnu.org
Mon Oct 13 21:33:00 GMT 2014


--- Comment #28 from Teresa Johnson <tejohnson at google dot com> ---
On Mon, Oct 13, 2014 at 8:53 AM, hjl.tools at gmail dot com
<gcc-bugzilla@gcc.gnu.org> wrote:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63432
> --- Comment #27 from H.J. Lu <hjl.tools at gmail dot com> ---
> (In reply to Teresa Johnson from comment #24)
>> Arg, looks very similar so maybe another instance of the duplicate
>> threading is slipping through? My own lto profiled bootstrap succeeded
>> with my patch. I will try updating to r216039 and redo it to see if I
>> can provoke the same failure.
> I sent you another testcase against r216150.

Thanks for the testcase, I reproduced it. It is a case of garbage in /
garbage out. The fre2 pass is introducing some big profile count
insanities, leading to the probability insanity being introduced when
we try to use the counts to compute the new probability in
recompute_probabilities. There is already handling for really large
probabilities due to this issue, and we need to add the same thing for
negative probabilities - essentially the patch you had originally
suggested for the first problem which wasn't necessary for that one
since that was an actually jump threading induced issue.

Will test that and send for review.

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