From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id A9AAB83D for ; Thu, 21 Jul 2016 14:02:16 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 29CB117F for ; Thu, 21 Jul 2016 14:02:16 +0000 (UTC) Message-ID: <1469109732.120686.168.camel@infradead.org> From: David Woodhouse To: Shuah Khan , Behan Webster Date: Thu, 21 Jul 2016 15:02:12 +0100 In-Reply-To: References: <87inw1skws.fsf@x220.int.ebiederm.org> <20160719173120.GE30372@sirena.org.uk> <20160720155319.GG6509@sirena.org.uk> <1469094899.120686.101.camel@infradead.org> Content-Type: multipart/signed; micalg="sha-256"; protocol="application/x-pkcs7-signature"; boundary="=-ftGmlp7qd2C0U4y6jojf" Mime-Version: 1.0 Cc: ksummit-discuss@lists.linuxfoundation.org Subject: Re: [Ksummit-discuss] [CORE TOPIC] [TECH TOPIC] Support (or move towards to) LLVM List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , --=-ftGmlp7qd2C0U4y6jojf Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, 2016-07-21 at 07:41 -0600, Shuah Khan wrote: > On Thu, Jul 21, 2016 at 3:54 AM, David Woodhouse wr= ote: > > On Wed, 2016-07-20 at 19:04 +0200, Jiri Kosina wrote: > > > On Wed, 20 Jul 2016, Mark Brown wrote: > > >=20 > > > > > > There's a push from certain quarters to move away from GCC to L= LVM. > > > >=20 > > > > > This might actually be an interesting topic per se. > > > >=20 > > > > Yes, indeed. > > >=20 > > > Let's make this a real proposal then ... (subject changed). I am agai= n a > > > bit unsure about the core / tech division here. > > >=20 > > > People who should be invited: proponents of the push from the certain > > > quarters mentioned by Mark above, and ideally some LLVM folks as well= . > > >=20 > > > I've never actually used llvm to compile the kernel (which makes me r= ather > > > poor contributor should any such discussion happen), but I've been on= the > > > "receiving side", debugging a crash that turned out to be llvm messin= g up > > > with IF in a way that interfers with local_irq_save(), and also suffe= red > > > from the followup frustration when I found out that this has been rep= orted > > > to llvm folks ages ago, and they haven't bothered to fix it (it's now= at > > > least worked around, in a very sub-optimal way (lahf/sahf)). > >=20 > > I got involved in building the kernel with LLVM a little while ago, > > after accidentally implementing .code16 support in LLVM =E2=80=94 for o= ther > > reasons, but it allowed the arch/x86/boot/ bits to be built with LLVM. > >=20 > > Apart from resolutely not wanting to implement variable length arrays > > on the stack, the LLVM folks actually seem quite keen to make things > > work. I'm interested in the problem you report above.. and note the > > absence of a bug number. Can you provide it? > >=20 > > You're right that it does take a while to get some things fixed, but > > people *are* doing a fairly good job of identifying them, filing bugs, > > and implementing workarounds until the bugs can be fixed. > >=20 > > Building with LLVM has also helped to find some real kernel bugs. I'd > > be keen to get this working more widely. > >=20 >=20 > Would you be willing to share your experiences and the nature of bugs > you were able to find using LLVM. Maybe that could be folded into this > discussion as a real life experience. http://llvm.linuxfoundation.org/index.php/Bugs Probably horrifically out of date. Behan is the best person to ask for a current status, I suspect... --=20 David Woodhouse Open Source Technology Centre David.Woodhouse@intel.com Intel Corporation --=-ftGmlp7qd2C0U4y6jojf Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCCEeAw ggXiMIIDyqADAgECAhBrp4p9CteI1lEK+Vnk57ThMA0GCSqGSIb3DQEBCwUAMH0xCzAJBgNVBAYT AklMMRYwFAYDVQQKEw1TdGFydENvbSBMdGQuMSswKQYDVQQLEyJTZWN1cmUgRGlnaXRhbCBDZXJ0 aWZpY2F0ZSBTaWduaW5nMSkwJwYDVQQDEyBTdGFydENvbSBDZXJ0aWZpY2F0aW9uIEF1dGhvcml0 eTAeFw0xNTEyMTYwMTAwMDVaFw0zMDEyMTYwMTAwMDVaMHUxCzAJBgNVBAYTAklMMRYwFAYDVQQK Ew1TdGFydENvbSBMdGQuMSkwJwYDVQQLEyBTdGFydENvbSBDZXJ0aWZpY2F0aW9uIEF1dGhvcml0 eTEjMCEGA1UEAxMaU3RhcnRDb20gQ2xhc3MgMSBDbGllbnQgQ0EwggEiMA0GCSqGSIb3DQEBAQUA A4IBDwAwggEKAoIBAQC9fdr3w6J9g/Zbgv3bW1+uHht1wLUZr5gkrLtXedg17AkefMyUGwrQdvwO 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