From owner-freebsd-bugs@freebsd.org Wed Apr 5 07:01:40 2017 Return-Path: Delivered-To: freebsd-bugs@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id B19FED2F481 for ; Wed, 5 Apr 2017 07:01:40 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org (kenobi.freebsd.org [IPv6:2001:1900:2254:206a::16:76]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 887E6C1 for ; Wed, 5 Apr 2017 07:01:40 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from bugs.freebsd.org ([127.0.1.118]) by kenobi.freebsd.org (8.15.2/8.15.2) with ESMTP id v3571eqM075214 for ; Wed, 5 Apr 2017 07:01:40 GMT (envelope-from bugzilla-noreply@freebsd.org) From: bugzilla-noreply@freebsd.org To: freebsd-bugs@FreeBSD.org Subject: [Bug 218387] -march=native or any specific CPU with clang seems to produce a lot of x87 instructions Date: Wed, 05 Apr 2017 07:01:40 +0000 X-Bugzilla-Reason: AssignedTo X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Base System X-Bugzilla-Component: bin X-Bugzilla-Version: 11.0-RELEASE X-Bugzilla-Keywords: X-Bugzilla-Severity: Affects Only Me X-Bugzilla-Who: dim@FreeBSD.org X-Bugzilla-Status: In Progress X-Bugzilla-Resolution: X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: dim@FreeBSD.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: bug_status assigned_to Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: https://bugs.freebsd.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-BeenThere: freebsd-bugs@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Bug reports List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 05 Apr 2017 07:01:40 -0000 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D218387 Dimitry Andric changed: What |Removed |Added ---------------------------------------------------------------------------- Status|New |In Progress Assignee|freebsd-bugs@FreeBSD.org |dim@FreeBSD.org --- Comment #4 from Dimitry Andric --- (In reply to Adam Stylinski from comment #0) > I think this is a bug, but perhaps I just think it is because the behavior > diverges from GCC by quite a bit. >=20 > When you compile an application that does floating point math with clang = in > current right now, specifying -march=3Dnative or -march=3Dsandybridge or = btver2 > or any number of CPUs I tried to target produces predominantly x87 > instructions. Typically GCC and most other compilers I've seen default to > targeting SSE instructions, instead. Do you have any concrete test case? I.e a minimized C or C++ program, with = the complete command line used to compile it, and pointers to the assembly where you think it is invalid? (Note that x87 instructions are still perfectly v= alid on even the newest x86 CPUs.) > If you specify -march=3Dx86-64, you get the results you'd expect > (predominantly SSE2 instructions for floating point). This leads me to > believe this is a bug, for most everything SSE units should be the most > optimal. There are a few parts in the FreeBSD source tree which go out of their way = to avoid SSE, so you might have hit those. Again, without a concrete example = it is not possible to say if there is any problem. (In reply to Adam Stylinski from comment #1) > Ahh, evidently this isn't a new issue. Any value of -march that is later > than nocona results in x87 instructions being emitted all over the binary. >=20 > I'd still consider it a bug, though, as Apple & Linux's clang ports appear > to have correct behavior for these values. I am highly skeptical about that, since there is no special "FreeBSD float" handling in LLVM or Clang. But if you provide a good test case, I can like= ly take it upstream. --=20 You are receiving this mail because: You are the assignee for the bug.=