From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 11045 invoked by alias); 12 Jun 2012 18:26:18 -0000 Received: (qmail 11008 invoked by uid 22791); 12 Jun 2012 18:26:17 -0000 X-SWARE-Spam-Status: No, hits=-4.1 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00,KHOP_THREADED,TO_NO_BRKTS_PCNT 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, 12 Jun 2012 18:26:04 +0000 From: "matt at use dot net" To: gcc-bugs@gcc.gnu.org Subject: [Bug rtl-optimization/53533] [4.7/4.8 regression] vectorization causes loop unrolling test slowdown as measured by Adobe's C++Benchmark Date: Tue, 12 Jun 2012 18:26:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: rtl-optimization X-Bugzilla-Keywords: missed-optimization X-Bugzilla-Severity: normal X-Bugzilla-Who: matt at use dot net 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: Message-ID: In-Reply-To: References: X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org X-SW-Source: 2012-06/txt/msg00725.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53533 --- Comment #11 from Matt Hargett 2012-06-12 18:25:25 UTC --- Richard, Thanks for the quick analysis! Sounds like a perfect storm of sorts :/ re: cprop failure: this may be indicated by another major regression in their suite for the "simple constant folding" tests. in GCC 4.1-4.6, those tests are all 0.0s but in 4.7 take tens of seconds. Let me know if you want me to file a separate bug/reduced test case for that, and then have that new bug depend on this one. Otherwise, I'll wait until this one sees some resolution and then retest. re: multiple passes: if you think that feature has enough merit to be revisited now, I can look into re-proposing Maxim's patches from October/November 2011 that integrated your feedback at the time. re: -march workaround: our deployment platform's minimum arch is nocona, and enabling -march=nocona doesn't workaround the issue. For grins, I tried -march=amdfam10 (another deployment target, but would require a separate distributable binary), but that also didn't work around the issue. I see a small improvement when using -fno-tree-vectorize, but not nearly as dramatic as yours. For the int32_t for and while loop unrolling, the times go from ~107s and ~105s to ~96s and ~95s, respectively. The do and goto loop unrolling times get slightly worse (~2%), but it might be noise. Let me know if there's any additional testing/footwork you'd like me to do. Again, thanks for the quick turnaround on such a deep analysis!