This is the mail archive of the
gcc-bugs@gcc.gnu.org
mailing list for the GCC project.
[Bug rtl-optimization/64317] [5 Regression] Ineffective allocation of PIC base register
- From: "law at redhat dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Thu, 12 Feb 2015 21:21:28 +0000
- Subject: [Bug rtl-optimization/64317] [5 Regression] Ineffective allocation of PIC base register
- Auto-submitted: auto-generated
- References: <bug-64317-4 at http dot gcc dot gnu dot org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64317
--- Comment #8 from Jeffrey A. Law <law at redhat dot com> ---
And for GCC 5, ISTM the question that hasn't been answered, particularly with
regard to the second reproducer is whether or this is a regression for the
overall performance of that code.
It's certainly possible that IRA determined that %ebx was better used to hold a
different value and that the PIC register might end up in a call-clobbered
register. If the object in %ebx is heavily used, the benefits of keeping that
value in %ebx may outweigh the cost of having the PIC value in a different
register (say perhaps one that is call-clobbered).