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

tejohnson at google dot com gcc-bugzilla@gcc.gnu.org
Fri Oct 3 20:18:00 GMT 2014


https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63432

--- Comment #10 from Teresa Johnson <tejohnson at google dot com> ---
On Fri, Oct 3, 2014 at 12:47 PM, hjl.tools at gmail dot com
<gcc-bugzilla@gcc.gnu.org> wrote:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63432
>
> H.J. Lu <hjl.tools at gmail dot com> changed:
>
>            What    |Removed                     |Added
> ----------------------------------------------------------------------------
>              Status|UNCONFIRMED                 |NEW
>    Last reconfirmed|                            |2014-10-03
>      Ever confirmed|0                           |1
>
> --- Comment #8 from H.J. Lu <hjl.tools at gmail dot com> ---
> Bug is in
>
> static void
> recompute_probabilities (basic_block bb)
> {
>   edge esucc;
>   edge_iterator ei;
>   FOR_EACH_EDGE (esucc, ei, bb->succs)
>     {
>       if (bb->count)
>         esucc->probability = GCOV_COMPUTE_SCALE (esucc->count,
>                                                  bb->count);
>       if (esucc->probability > REG_BR_PROB_BASE)
>         {
>
> We got
>
> (gdb) whatis esucc->probability
> type = int
> (gdb) p esucc->count
> $7 = 2822215
> (gdb) p bb->count
> $8 = 1
> (gdb) p esucc->probability
> $9 = -1842621072

This points to a bigger problem, since esucc->count should be <=
bb->count. Can you attach the input files and command line and I will
take a closer look?

Thanks,
Teresa

> (gdb)
>
> When count is set from frequency scaled up by REG_BR_PROB_BASE,
> probability may overflow.
>
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