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Mon, 03 Aug 2026 10:08:43 -0700 (PDT) Received: from localhost ([2600:1702:7a90:6f9f:8bc4:8aec:108d:7a04]) by smtp.gmail.com with ESMTPSA id 00721157ae682-81fcd14658csm58796907b3.45.2026.08.03.10.08.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 03 Aug 2026 10:08:42 -0700 (PDT) From: Matt Turner Subject: [PATCH 0/2] alpha: enable building with clang Date: Mon, 03 Aug 2026 13:08:40 -0400 Message-Id: <20260803-alpha-clang-v1-0-1c4ba5ba7a64@gmail.com> Precedence: bulk X-Mailing-List: linux-alpha@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-B4-Tracking: v=1; b=H4sIAAAAAAAC/x2MQQqAIBAAvxJ7TlATkb4SHUy3XBAThQjEvycdh 2GmQcVCWGGdGhR8qNKdBoh5AhdsupCRHwySS80NX5iNOVjm4nBMW+eFUngY7WAUueBJ73/b9t4 /5aH0Ql0AAAA= X-Change-ID: 20260803-alpha-clang-6acd144eb86c To: Richard Henderson , Matt Turner , Magnus Lindholm , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , Nicolas Schier Cc: linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, linux-kbuild@vger.kernel.org X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=1804; i=mattst88@gmail.com; h=from:subject:message-id; bh=81MWPbgRttoR+0d8yfKjqdwgj8cHpLV4Tc5BStoCbiU=; b=owGbwMvMwCW25rVmCc8sv+mMp9WSGLIKTkv2xB08G3BGNvB3wKKIV5UPJmpLhfCV3otRE3QTO /pu7vZPHR9ZGMS4GGaKKbLErVdkmdW2Y6nPaelfMHNYmUCGSIs0MAABCwNfbmJeqZGOkZ6ptqGe IZChYxQPkdNj0MgsLi5NLdJNKyhyyMsvSSzJzM8r1ssvSM0rSC/QS8tMK8nIyC8qTgUaoZeXWmL q6uhmZGhgYuloYeZk4Whq4uzsZOjk5ujo7OpkZGluYuBs6WjiamnOwMUpAHPNEQtGhtNqv7yftT 8TMuCZfPHp2r5rauVq4f7za//zm+mnLs5QqmNk+MnzNqy4YuHGD85HvB8IBl1boij6tvr1C+7/C StebAwJ4wQA X-Developer-Key: i=mattst88@gmail.com; a=openpgp; fpr=3BB639E56F861FA2E86505690FDD682D974CA72A Two small patches to let the alpha kernel build with clang. The first registers the clang target triple and stops passing -Wa,-mev6 when the compiler is not gcc. That flag exists to keep gas from emulating instructions it believes the target lacks; it is a gas-only option and clang's integrated assembler does not emulate instructions, so it is not needed there. The second fixes two uses of local register-asm variables that clang does not honor. clang treats `register unsigned long x __asm__("$N")` as the named register only where the variable appears as an inline-asm operand, so reading one to get the live $gp or $sp yields an undefined value. trap_init() passed that to PAL_wrkgp and load_PCB() stored it into the PCB for swpctx, either of which wedges an early boot. Note that the alpha backend is not in upstream LLVM. It lives in https://github.com/alphalinux-org/llvm-project and is a work in progress, so the scripts/Makefile.clang entry has no effect with an upstream clang today. I am sending this now because the second patch is a real bug in its own right -- the register-asm reads are only guaranteed to work by gcc's implementation, not by anything either compiler documents -- but I understand if the kbuild side would rather wait for the backend to land upstream. --- Matt Turner (2): alpha: enable building with clang alpha: read $gp and $sp explicitly for clang arch/alpha/Makefile | 8 +++++++- arch/alpha/kernel/traps.c | 4 +++- arch/alpha/mm/init.c | 3 +-- scripts/Makefile.clang | 1 + 4 files changed, 12 insertions(+), 4 deletions(-) --- base-commit: 0e6be1d34ae92e2b0dbc1b7410d422b22464389a change-id: 20260803-alpha-clang-6acd144eb86c Best regards, -- Matt Turner