From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 84DF272 for ; Mon, 6 Sep 2021 18:27:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1630952853; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=zdZg7k52Zmj/hALie/T8LIPyy9j0vAZZQI7YDqk+68Q=; b=LocQZ6z1rcdHMKNmhVoHRP8JTMlDB8HfPZVlcNskuc6uYuaTAQJRHipi8lS6VqUL7nb7wn qSjdTUdpctt63wD+5M2t2DNPKmIahprGAKpIb7ntoRo2+ZSGHLplvoolQ554wBnq0inQO/ +T7Ee0f1lJ+vwJbGdxed4oBnk1AIeZ0= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-334-8aTRbxFEMw2lx2hBnSYCSQ-1; Mon, 06 Sep 2021 14:27:32 -0400 X-MC-Unique: 8aTRbxFEMw2lx2hBnSYCSQ-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 59C0C1883520; Mon, 6 Sep 2021 18:27:30 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.39.195.4]) by smtp.corp.redhat.com (Postfix) with ESMTPS id A66C25C22B; Mon, 6 Sep 2021 18:27:27 +0000 (UTC) From: Florian Weimer To: Linus Torvalds Cc: Segher Boessenkool , Nathan Chancellor , Masahiro Yamada , Nick Desaulniers , Linux Kbuild mailing list , Linux Kernel Mailing List , clang-built-linux , llvm@lists.linux.dev, linux-toolchains@vger.kernel.org Subject: Re: [GIT PULL v2] Kbuild updates for v5.15-rc1 References: <3b461878-a4a0-2f84-e177-9daf8fe285e7@kernel.org> <878s0c4vng.fsf@oldenburg.str.redhat.com> <20210904131911.GP1583@gate.crashing.org> <871r644bd2.fsf@oldenburg.str.redhat.com> <20210904191531.GS1583@gate.crashing.org> <20210906154642.GV1583@gate.crashing.org> <20210906172701.GX1583@gate.crashing.org> Date: Mon, 06 Sep 2021 20:27:25 +0200 In-Reply-To: (Linus Torvalds's message of "Mon, 6 Sep 2021 11:11:35 -0700") Message-ID: <87lf49wodu.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 * Linus Torvalds: > We use the compiler intrinsics without the C library header files for > everything else, so doing so for seems to actually be a > clarification and improvement. This is an exaggeration. On several architectures, the kernel cannot use the vector built-ins directly. Some of the implementing headers are very special and intertwined with the compiler. is currently not such a case, but it's just not technically not feasible to avoid dependencies on all compiler headers. I think this considerably weakens the case against because the compiler version is so obviously harmless. What the kernel is doing here is imposing an unnecesary constraint on compiler development. Basically, you are telling compiler writers that implementing features with the help of header files is a bad idea because it makes it more difficult to use them from the kernel. (See the proposed exceptions for vector code.) Thanks, Florian