[Bug libstdc++/116140] New: [15 Regression] 5-35% slowdown of 483.xalancbmk and 523.xalancbmk_r since r15-2356-ge69456ff9a54ba

[pheeck at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116140

            Bug ID: 116140
           Summary: [15 Regression] 5-35% slowdown of 483.xalancbmk and
                    523.xalancbmk_r since r15-2356-ge69456ff9a54ba
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pheeck at gcc dot gnu.org
                CC: hubicka at gcc dot gnu.org, jamborm at gcc dot gnu.org,
                    redi at gcc dot gnu.org
            Blocks: 26163
  Target Milestone: ---

The SPEC benchmark xalancbmk has slowed down on recent versions of GCC. The
slowdowns range from 5% to 35%. Both the 2006 version and the 2017 version
slowed down. We have seen the slowdowns on both x86 and aarch64. We have
bisected the slowdown to r15-2356-ge69456ff9a54ba.

Here are some graphs of various configurations where the slowdown can be seen:
https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=1109.290.0
https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=469.290.0
https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=464.290.0
https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=476.290.0
https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=584.367.0
https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=472.367.0


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=26163
[Bug 26163] [meta-bug] missed optimization in SPEC (2k17, 2k and 2k6 and 95)