[Bug gdb/27979] New: Performance regression of ~10% in conditional breakpoint testcase

[mhov at undo dot io]

https://sourceware.org/bugzilla/show_bug.cgi?id=27979

            Bug ID: 27979
           Summary: Performance regression of ~10% in conditional
                    breakpoint testcase
           Product: gdb
           Version: 10.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: gdb
          Assignee: unassigned at sourceware dot org
          Reporter: mhov at undo dot io
  Target Milestone: ---

Created attachment 13491
  --> https://sourceware.org/bugzilla/attachment.cgi?id=13491&action=edit
reproducer program

There seems to be a performance regression from 9.2 to 10.2 that is observable
in the time to run the following command on the attached reproducer program.
This has been used to benchmark the performance of conditional breakpoints.

  $ gcc --version
    gcc (Ubuntu 9.3.0-17ubuntu1~20.04) 9.3.0
  $ gcc -g repro.c
  $ ./gdb --batch --ex "b foo if bar==0x7ffffff" --ex "run" --args ./a.out

Also attached is a log from the libera.chat #gdb channel where this regression
was discussed.

As can be seen in the attached chat log, bisection by Simon suggests that this
commit is to blame:
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=1009d92fc621bc4d017029b90a5bfab16e17fde5

I'm not currently in a position to delve deeper into this, so I'm posting here
in case anyone wants to pick it up.

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