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From: Matt Austern <austern@apple.com> To: bkoz@gcc.gnu.org Cc: gcc-prs@gcc.gnu.org, Subject: Re: libstdc++/8230: Buggy allocator behaviour Date: Thu, 21 Nov 2002 03:47:00 -0000 [thread overview] Message-ID: <20021114221603.20355.qmail@sources.redhat.com> (raw) The following reply was made to PR libstdc++/8230; it has been noted by GNATS. From: Matt Austern <austern@apple.com> To: Gabriel Dos Reis <gdr@integrable-solutions.net> Cc: Benjamin Kosnik <bkoz@redhat.com>, bkoz@gcc.gnu.org, gcc-bugs@gcc.gnu.org, jkanze@caicheuvreux.com, gcc-gnats@gcc.gnu.org, libstdc++@gcc.gnu.org Subject: Re: libstdc++/8230: Buggy allocator behaviour Date: Thu, 14 Nov 2002 14:10:55 -0800 On Thursday, November 14, 2002, at 12:39 PM, Gabriel Dos Reis wrote: > Benjamin Kosnik <bkoz@redhat.com> writes: > > | See attached patch for a way to fix this with the pool allocators. > > I agree with your patch. > > The following comment is for possible improvements. What about using > > if (__builtin_expect(__ret == 0, 0)) > __throw_bad_alloc("allocate::allocate"); > > ? > That gives a hint to the compiler that the branch is expected to be > taken very unfrequently, and it should make scheduling accordingly. > > In general, I would like to see us starting using use > __builtin_expect() > at places where we do checks for limits cases. Thoughts? Two questions. First, is it known how much of a speedup this gives on typical platforms? Second, if the answer to question 1 is "a lot": is there some sensible way to use this in the compiler itself? I suppose it'd have to involve some ghastly macro hackery because of the bootstrap problem, but it we're talking big performance wins, it might be worth it. --Matt
next reply other threads:[~2002-11-14 22:16 UTC|newest] Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top 2002-11-21 3:47 Matt Austern [this message] -- strict thread matches above, loose matches on Subject: below -- 2002-11-23 1:16 bkoz 2002-11-21 14:01 Richard Henderson 2002-11-21 4:06 Gabriel Dos Reis 2002-11-20 23:03 Gabriel Dos Reis 2002-11-20 19:09 Gabriel Dos Reis 2002-11-20 18:20 Benjamin Kosnik 2002-11-20 18:19 Benjamin Kosnik 2002-11-20 18:02 Gabriel Dos Reis 2002-11-20 5:07 bkoz 2002-10-15 5:56 gdr
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