From patchwork Mon Feb 9 19:23:35 2026 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Samuel Thibault X-Patchwork-Id: 129819 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from vm01.sourceware.org (localhost [127.0.0.1]) by sourceware.org (Postfix) with ESMTP id 2E70848FEC3D for ; Mon, 9 Feb 2026 19:24:09 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 2E70848FEC3D X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from sonata.ens-lyon.org (sonata.ens-lyon.org [140.77.166.138]) by sourceware.org (Postfix) with ESMTPS id 03AFA48FED8E for ; Mon, 9 Feb 2026 19:23:41 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 03AFA48FED8E Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=ens-lyon.org Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=bounce.ens-lyon.org ARC-Filter: OpenARC Filter v1.0.0 sourceware.org 03AFA48FED8E Authentication-Results: server2.sourceware.org; arc=none smtp.remote-ip=140.77.166.138 ARC-Seal: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1770665021; cv=none; b=Tpqw2eu0FFV+EmcCCEcxjgJgxjeCPEn4M586UsAdX0uCgH4uyjZW/ItwX+Gd3D9Alhn7jlTGSijDKa21r8+7210YJfb5U8FngVprb/y2g64YIpNWugC3w1stf5SqEl5w++DOSJ/5bFCzb6HNUP448L1vlxMW/nDe8V513RJzaD4= ARC-Message-Signature: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1770665021; c=relaxed/simple; bh=3S7HHsRezNeP2MRmy3mmRVgrL5lY9iA+A8b8dhU5zzc=; h=From:To:Subject:Date:Message-ID:MIME-Version; b=Q3PXTdwwM61RcHFX3O9SjDgZqX4wG899lKp3gjerpb22SBc1bTCVxPNxgtTZGB24B5yH6aTyDfw3Xe6h4zRM8axqSU/BLHlV9BO0jQKog06moGVvQc+TdWSK6WdQgr6Gq1fmDk5ZDyPx35NI3U5QP+ZUFc5p6xQb3sLJTtePhNw= ARC-Authentication-Results: i=1; server2.sourceware.org DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 03AFA48FED8E Received: from localhost (localhost [127.0.0.1]) by sonata.ens-lyon.org (Postfix) with ESMTP id 571C3A71F0; Mon, 9 Feb 2026 20:23:38 +0100 (CET) Received: from sonata.ens-lyon.org ([127.0.0.1]) by localhost (sonata.ens-lyon.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id z5tKzP1w-2DJ; Mon, 9 Feb 2026 20:23:38 +0100 (CET) Received: from end (unknown [212.133.41.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by sonata.ens-lyon.org (Postfix) with ESMTPSA id 0F9EDA71C2; Mon, 9 Feb 2026 20:23:38 +0100 (CET) Received: from samy by end with local (Exim 4.99.1) (envelope-from ) id 1vpWrA-0000000FS8b-28Fl; Mon, 09 Feb 2026 20:23:36 +0100 From: Samuel Thibault To: libc-alpha@sourceware.org Cc: George Hu , commit-hurd@gnu.org, Samuel Thibault Subject: [hurd,commited] x86-64: Use 32-bit zero idiom for shorter encoding Date: Mon, 9 Feb 2026 20:23:35 +0100 Message-ID: <20260209192335.3683074-1-samuel.thibault@ens-lyon.org> X-Mailer: git-send-email 2.51.0 MIME-Version: 1.0 X-Spam-Status: No, score=-10.8 required=5.0 tests=BAYES_00, GIT_PATCH_0, JMQ_SPF_NEUTRAL, KAM_DMARC_STATUS, RCVD_IN_DNSWL_BLOCKED, RCVD_IN_SBL_CSS, RCVD_IN_VALIDITY_RPBL_BLOCKED, RCVD_IN_VALIDITY_SAFE_BLOCKED, SPF_HELO_PASS, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: libc-alpha-bounces~patchwork=sourceware.org@sourceware.org From: George Hu Replace the 64-bit zero idiom with the 32-bit form. In 64-bit mode, zeroing the lower 32 bits of a GPR implicitly clears the entire register. The 32-bit encoding is one byte shorter while preserving identical semantics. Reviewed-by: Samuel Thibault --- sysdeps/mach/hurd/x86_64/static-start.S | 2 +- sysdeps/mach/hurd/x86_64/tst-sig-redzone.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/sysdeps/mach/hurd/x86_64/static-start.S b/sysdeps/mach/hurd/x86_64/static-start.S index ec9c50239e..d670d45210 100644 --- a/sysdeps/mach/hurd/x86_64/static-start.S +++ b/sysdeps/mach/hurd/x86_64/static-start.S @@ -27,7 +27,7 @@ _start: movq %rsp, %rdi call _hurd_stack_setup - xorq %rdx, %rdx + xorl %edx, %edx jmp _start1 #define _start _start1 diff --git a/sysdeps/mach/hurd/x86_64/tst-sig-redzone.c b/sysdeps/mach/hurd/x86_64/tst-sig-redzone.c index 32c7ab90f4..24b510c0aa 100644 --- a/sysdeps/mach/hurd/x86_64/tst-sig-redzone.c +++ b/sysdeps/mach/hurd/x86_64/tst-sig-redzone.c @@ -103,7 +103,7 @@ asm ( "repe scasq\n" " jne fail\n" -" xor %rax,%rax\n" +" xor %eax,%eax\n" " ret\n" "fail:\n" " movq $1,%rax\n"