From: Peter Bergner <bergner@vnet.ibm.com>
To: GCC <gcc@gcc.gnu.org>
Cc: Vladimir N Makarov <vmakarov@redhat.com>,
Pat Haugen <pthaugen@linux.vnet.ibm.com>
Subject: Why does IRA force all pseudos live across a setjmp call to be spilled?
Date: Fri, 02 Mar 2018 19:45:00 -0000 [thread overview]
Message-ID: <141cfa78-f202-029a-e530-24e657692bff@vnet.ibm.com> (raw)
While debugging the PR84264 ICE caused by the following test case:
void _setjmp ();
void a (unsigned long *);
void
b ()
{
for (;;)
{
_setjmp ();
unsigned long args[9]{};
a (args);
}
}
I noticed that IRA is spilling all pseudos that are live across the call
to setjmp. Why is that? Trying to look through the history of this, I see
Jim committed a patch to reload that removed it spilling everything across
all setjmps:
https://gcc.gnu.org/ml/gcc-patches/2003-11/msg01667.html
But currently ira-lives.c:process_bb_node_lives() has:
/* Don't allocate allocnos that cross setjmps or any
call, if this function receives a nonlocal
goto. */
if (cfun->has_nonlocal_label
|| find_reg_note (insn, REG_SETJMP,
NULL_RTX) != NULL_RTX)
{
SET_HARD_REG_SET (OBJECT_CONFLICT_HARD_REGS (obj));
SET_HARD_REG_SET (OBJECT_TOTAL_CONFLICT_HARD_REGS (obj));
}
...which forces us to spill everything live across the setjmp by forcing
the pseudos to interfere all hardregs. That can't be good for performance.
What am I missing?
Peter
next reply other threads:[~2018-03-02 19:45 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-02 19:45 Peter Bergner [this message]
2018-03-02 19:55 ` Alexander Monakov
2018-03-02 21:26 ` Jeff Law
2018-03-03 3:28 ` Peter Bergner
2018-03-03 16:29 ` Jeff Law
2018-03-03 23:47 ` Peter Bergner
2018-03-04 0:30 ` Peter Bergner
2018-03-04 8:57 ` Richard Biener
2018-03-04 9:11 ` Andreas Schwab
2018-03-05 2:12 ` Jeff Law
2018-03-04 13:57 ` Eric Botcazou
2018-03-04 16:40 ` Peter Bergner
2018-03-04 17:39 ` Andreas Schwab
2018-03-05 0:16 ` Segher Boessenkool
2018-03-05 7:01 ` Eric Botcazou
2018-03-05 7:09 ` Eric Botcazou
2018-03-05 15:33 ` Segher Boessenkool
2018-03-05 16:18 ` Eric Botcazou
2018-03-06 16:20 ` Peter Bergner
2018-03-03 3:21 ` Vladimir Makarov
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=141cfa78-f202-029a-e530-24e657692bff@vnet.ibm.com \
--to=bergner@vnet.ibm.com \
--cc=gcc@gcc.gnu.org \
--cc=pthaugen@linux.vnet.ibm.com \
--cc=vmakarov@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).