From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received-SPF: Pass (sender SPF authorized) identity=mailfrom; client-ip=209.132.183.28; helo=mx1.redhat.com; envelope-from=lersek@redhat.com; receiver=edk2-devel@lists.01.org Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id DE7072119681D for ; Wed, 12 Dec 2018 03:50:00 -0800 (PST) Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 6294C3001BC6; Wed, 12 Dec 2018 11:50:00 +0000 (UTC) Received: from lacos-laptop-7.usersys.redhat.com (ovpn-120-211.rdu2.redhat.com [10.10.120.211]) by smtp.corp.redhat.com (Postfix) with ESMTP id C66C160C44; Wed, 12 Dec 2018 11:49:58 +0000 (UTC) To: Ard Biesheuvel , edk2-devel@lists.01.org Cc: Michael D Kinney , Liming Gao , Bob Feng , Leif Lindholm References: <20181212103308.8099-1-ard.biesheuvel@linaro.org> <20181212103308.8099-3-ard.biesheuvel@linaro.org> From: Laszlo Ersek Message-ID: <0f1b613c-e027-e025-ccc1-d2526653d0ca@redhat.com> Date: Wed, 12 Dec 2018 12:49:57 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20181212103308.8099-3-ard.biesheuvel@linaro.org> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.45]); Wed, 12 Dec 2018 11:50:00 +0000 (UTC) Subject: Re: [PATCH 2/3] BaseTools/tools_def ARM CLANG35: work around -mno-movt option name change X-BeenThere: edk2-devel@lists.01.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: EDK II Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 12 Dec 2018 11:50:01 -0000 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit On 12/12/18 11:33, Ard Biesheuvel wrote: > PE/COFF only has a very limited id space for runtime relocations, and > so it defines only a single relocation for movw/movt instruction pairs, > which can be combined to load a 32-bit symbol reference into a register. > For this to work as expected, these instructions must always appear in > the same order and adjacently, and this is something few compilers take > into account, unless they target PE/COFF explicitly (and this is not the > case for our ELF based toolchains) > > For Clang 3.6 and later, we can pass the -mno-movt option to suppress > movw/movt pairs entirely, which works around the issue. Unfortunately, > for Clang 3.5, the option is called differently (-mllvm -arm-use-movt=0) > and mutually incompatible between 3.5 and 3.6. > > Since it is desirable for the CLANG35 toolchain to be usable on newer > versions of Clang as well (given that it is the only non-LTO alternative > to CLANG38), let's work around this issue in a way that permits versions > 3.5 and newer of Clang to be used with the CLANG35 profile. > > So pass the -mkernel flag instead (and drop the -mno-unaligned-access > in *_CLANG35_ARM_CC_XIPFLAGS which now becomes redundant, and which > Clang complains about). This also inhibits movw/movt generation, along > with some other changes (e.g., long calls) which do affect code generation > but not in a undesirable manner. > > Contributed-under: TianoCore Contribution Agreement 1.1 > Signed-off-by: Ard Biesheuvel > --- > BaseTools/Conf/tools_def.template | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/BaseTools/Conf/tools_def.template b/BaseTools/Conf/tools_def.template > index ac2b95e0f5ba..2ba833e1fb06 100755 > --- a/BaseTools/Conf/tools_def.template > +++ b/BaseTools/Conf/tools_def.template > @@ -5249,7 +5249,7 @@ DEFINE CLANG35_AARCH64_CC_FLAGS = DEF(GCC_AARCH64_CC_FLAGS) DEF(CLANG35_AARCH64 > *_CLANG35_ARM_ASM_FLAGS = DEF(GCC_ASM_FLAGS) DEF(CLANG35_ARM_TARGET) $(ARCHASM_FLAGS) $(PLATFORM_FLAGS) -Qunused-arguments > *_CLANG35_ARM_DLINK_FLAGS = DEF(CLANG35_ARM_TARGET) DEF(GCC_ARM_DLINK_FLAGS) > *_CLANG35_ARM_DLINK2_FLAGS = DEF(GCC_DLINK2_FLAGS_COMMON) -Wl,--defsym=PECOFF_HEADER_SIZE=0x220 > -*_CLANG35_ARM_PLATFORM_FLAGS = -march=armv7-a > +*_CLANG35_ARM_PLATFORM_FLAGS = -march=armv7-a -mkernel -Qunused-arguments > *_CLANG35_ARM_PP_FLAGS = DEF(GCC_PP_FLAGS) DEF(CLANG35_ARM_TARGET) $(ARCHCC_FLAGS) $(PLATFORM_FLAGS) > *_CLANG35_ARM_RC_FLAGS = DEF(GCC_ARM_RC_FLAGS) > *_CLANG35_ARM_VFRPP_FLAGS = DEF(GCC_VFRPP_FLAGS) DEF(CLANG35_ARM_TARGET) $(ARCHCC_FLAGS) $(PLATFORM_FLAGS) > The commit message speaks about adding -mkernel, and removing -mno-unaligned-access (elsewhere). In the patch, I only see -mkernel (plus an un-announced -Qunused-arguments option). Is the commit message slightly out-of-date relative to the code? (Or perhaps the other way around?) Thanks! Laszlo