From patchwork Wed Jun 23 23:59:04 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Noah Goldstein X-Patchwork-Id: 43994 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 4906E3982004 for ; Thu, 24 Jun 2021 00:00:52 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 4906E3982004 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1624492852; bh=HpUX23gfUQUk9edoZIvYAulS4BDs+FRsukUCTgdXLSs=; h=To:Subject:Date:In-Reply-To:References:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To: From; b=E2tDtHYKxie8Yu10ime0OGdLsBkH73RW/d1Jq14O725f+OAyoODrVXYKeI23BAbu0 s3tgkWF1BOZ/rFEZcHE+yk1yszj7NU3zyicltR2GG8g+tH8tWdqkd8kxLIMcgtQSkK jcPF0trNLVoVOs2aaTUbrijBwPY78Wvj+vEuwXuY= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from mail-qk1-x72c.google.com (mail-qk1-x72c.google.com [IPv6:2607:f8b0:4864:20::72c]) by sourceware.org (Postfix) with ESMTPS id 1345D394AC3B for ; Thu, 24 Jun 2021 00:00:30 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 1345D394AC3B Received: by mail-qk1-x72c.google.com with SMTP id y29so8312301qky.12 for ; Wed, 23 Jun 2021 17:00:30 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=HpUX23gfUQUk9edoZIvYAulS4BDs+FRsukUCTgdXLSs=; b=UIAxiNfDRMTdk1R4hthUZgwh2sgD+k3BHNCYJYqQS5afbZWgnQQEoAWfA/hDhQ1Wo3 AysDpvD1S6b7AnT0slAcvcrIwFWxFtOdpDfoUFZAdQ5E6BKKjpUcNEQVHaNk3PgsS+xb yEBHnY8Dn90EVsK4ckxiAix2fnH795MGIJvH7z/mBXmKByM2sU4oJM/FW0BLXqcWJs5p 0M7lSsYnSOzK0W1XXyMjGbDKsZKH34TgcubsgTpOeFiwVXP+Bbkt+Pvj3g0XoGflrZyc Fds+AgwMFnu5Ppbe1Iv6h2CQXpUqSfg3IEez8WNa53Cjq/xUsEN9V9VL6IUE5Zbw7Oi3 WO0w== X-Gm-Message-State: AOAM533tsX6vTJgXSRtviUy72mX66NWy3HvCD4zSHgKqkdMlOGIf+Br4 Nln3CbHYLQvKogRLOs0GfbEvohbsiks= X-Google-Smtp-Source: ABdhPJxDHLrM3NKQe1K8dYKRuRvJA1kf8IKnchiQrvnwq4K77mEBCKYsyO+P8xUBrYZ/OvSCFqdJrA== X-Received: by 2002:a05:620a:2483:: with SMTP id i3mr2756699qkn.376.1624492829488; Wed, 23 Jun 2021 17:00:29 -0700 (PDT) Received: from localhost.localdomain (pool-173-75-15-191.pitbpa.fios.verizon.net. [173.75.15.191]) by smtp.googlemail.com with ESMTPSA id x19sm975849qtj.79.2021.06.23.17.00.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 23 Jun 2021 17:00:29 -0700 (PDT) To: libc-alpha@sourceware.org Subject: [PATCH v1 2/2] x86: Remove unnecessary overflow check from wcsnlen-sse4_1.S Date: Wed, 23 Jun 2021 19:59:04 -0400 Message-Id: <20210623235902.1614933-2-goldstein.w.n@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210623235902.1614933-1-goldstein.w.n@gmail.com> References: <20210623235902.1614933-1-goldstein.w.n@gmail.com> MIME-Version: 1.0 X-Spam-Status: No, score=-12.4 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, FREEMAIL_FROM, GIT_PATCH_0, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: Noah Goldstein via Libc-alpha From: Noah Goldstein Reply-To: Noah Goldstein Errors-To: libc-alpha-bounces+patchwork=sourceware.org@sourceware.org Sender: "Libc-alpha" No bug. The way wcsnlen will check if near the end of maxlen is the following macro: mov %r11, %rsi; \ subq %rax, %rsi; \ andq $-64, %rax; \ testq $-64, %rsi; \ je L(strnlen_ret) Which words independently of s + maxlen overflowing. So the second overflow check is unnecissary for correctness and just extra overhead in the common no overflow case. test-strlen.c, test-wcslen.c, test-strnlen.c and test-wcsnlen.c are all passing Signed-off-by: Noah Goldstein Reviewed-by: H.J. Lu --- Sorry I didn't notice this earlier before my last commit. As of submitting this patch a775a7a3eb1e85b54af0b4ee5ff4dcf66772a1fb Is HEAD of master to maybe rebase so commit history isnt messy? sysdeps/x86_64/multiarch/strlen-vec.S | 7 ------- 1 file changed, 7 deletions(-) diff --git a/sysdeps/x86_64/multiarch/strlen-vec.S b/sysdeps/x86_64/multiarch/strlen-vec.S index 439e486a43..b7657282bd 100644 --- a/sysdeps/x86_64/multiarch/strlen-vec.S +++ b/sysdeps/x86_64/multiarch/strlen-vec.S @@ -71,19 +71,12 @@ L(n_nonzero): suffice. */ mov %RSI_LP, %R10_LP sar $62, %R10_LP - test %R10_LP, %R10_LP jnz __wcslen_sse4_1 sal $2, %RSI_LP # endif - /* Initialize long lived registers. */ - add %RDI_LP, %RSI_LP -# ifdef AS_WCSLEN -/* Check for overflow again from s + maxlen * sizeof(wchar_t). */ - jbe __wcslen_sse4_1 -# endif mov %RSI_LP, %R10_LP and $-64, %R10_LP mov %RSI_LP, %R11_LP