From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-334848-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 14278 invoked by alias); 26 Oct 2010 19:12:10 -0000
Received: (qmail 14263 invoked by uid 22791); 26 Oct 2010 19:12:09 -0000
X-SWARE-Spam-Status: No, hits=-2.4 required=5.0	tests=ALL_TRUSTED,AWL,BAYES_00,MISSING_MID
X-Spam-Check-By: sourceware.org
Received: from localhost (HELO gcc.gnu.org) (127.0.0.1)    by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Tue, 26 Oct 2010 19:12:03 +0000
From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/46186] Clang creates code running 1600 times faster than gcc's
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: c
X-Bugzilla-Keywords:
X-Bugzilla-Severity: minor
X-Bugzilla-Who: jakub at gcc dot gnu.org
X-Bugzilla-Status: NEW
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Changed-Fields:
In-Reply-To: <bug-46186-4@http.gcc.gnu.org/bugzilla/>
References: <bug-46186-4@http.gcc.gnu.org/bugzilla/>
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
Content-Type: text/plain; charset="UTF-8"
MIME-Version: 1.0
Date: Tue, 26 Oct 2010 19:12:00 -0000
Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
List-Id: <gcc-bugs.gcc.gnu.org>
List-Archive: <http://gcc.gnu.org/ml/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-help@gcc.gnu.org>
Sender: gcc-bugs-owner@gcc.gnu.org
X-SW-Source: 2010-10/txt/msg02237.txt.bz2
Message-ID: <20101026191200.qLVsL4Y8vahtvzFoR_AAOaqWha1kRld-vperb-ezwzY@z>

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46186

--- Comment #18 from Jakub Jelinek <jakub at gcc dot gnu.org> 2010-10-26 19:11:59 UTC ---
I guess you mean LLVM instead of clang, I'm pretty sure the FE doesn't perform
this optimization.

Anyway, given:

#define F(n, exp) \
unsigned long                                   \
f##n (unsigned long a, unsigned long b)         \
{                                               \
  unsigned long sum = 0;                        \
  for (; a < b; a++)                            \
    exp;                                        \
  return sum;                                   \
}

F (1, sum += a)
F (2, sum += 2)
F (3, sum += b)
F (4, sum += a * a)
F (5, sum += a * a * a)
F (6, a * a * a * a * a + 2 * a * a * a + 5 * a)

only the f1/f2/f3 cases make it into chrec_apply (and only f2/f3 are currently
handled there).