From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pj1-x102a.google.com (mail-pj1-x102a.google.com [IPv6:2607:f8b0:4864:20::102a]) by sourceware.org (Postfix) with ESMTPS id D131D38515CD for ; Thu, 30 Jun 2022 03:44:36 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org D131D38515CD Received: by mail-pj1-x102a.google.com with SMTP id b12-20020a17090a6acc00b001ec2b181c98so1510741pjm.4 for ; Wed, 29 Jun 2022 20:44:36 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=Q4fk77oyZWIjqm5nEjoWrrIuWbIh6DKLCepp2WSZ3N0=; b=DFB7kl45i16NfIW9O7oZlQyiGPMYrWzR+t+CMFkDberCDAoCawWLaxQlkuYaNsz9Zg vBHe9hm8XJ9Nh16x1S39RiIFcs+39OFexXmIQ20wPf5O7keeQqRqumiqLfdP30tnjkWW Laf+7EAd4w+bg+sYVejneCCkZjezu947y+59IlKajSGCkARwTqYVEfAFOV454l2tQYY5 FLkl6HOla4I8tJBMJZVah849PCsSNZPru8FTf+4kH1zlbm6PcK07z8LSzWpSR21etrm/ q2nARUo8z5bF1Eg9WzfUte1UF2tVpymjv7n5P53kxvDxvN0JHAfZogiuA0pi4itMfoCs hT6Q== X-Gm-Message-State: AJIora+flgYP/9DXdJex2BNU4e7sgg/yC4a6DiA8IrLGkQJaQbZ2MBAC LbDX5dkF5iThV9iyhfBBi9Wc/sLz/gA= X-Google-Smtp-Source: AGRyM1vxI0HnNMaGYtqEQpRnrQnbvNqXQbIM9XGwebmDE2Yda2FjNuwNWmGt1Cmzntk178VUqgv1lA== X-Received: by 2002:a17:902:ecc8:b0:16b:96b0:40b3 with SMTP id a8-20020a170902ecc800b0016b96b040b3mr9564550plh.65.1656560675807; Wed, 29 Jun 2022 20:44:35 -0700 (PDT) Received: from noah-tgl.. ([2600:1010:b06b:33eb:5bf6:2bd6:d829:32ab]) by smtp.gmail.com with ESMTPSA id o15-20020a170902d4cf00b0016a0d350b78sm12433960plg.58.2022.06.29.20.44.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 29 Jun 2022 20:44:35 -0700 (PDT) From: Noah Goldstein To: libc-alpha@sourceware.org Subject: [PATCH v6 1/2] x86: Add comment explaining no Slow_SSE4_2 check in ifunc-sse4_2 Date: Wed, 29 Jun 2022 20:44:31 -0700 Message-Id: <20220630034432.3749620-1-goldstein.w.n@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220628152717.17838-1-goldstein.w.n@gmail.com> References: <20220628152717.17838-1-goldstein.w.n@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-11.8 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, FREEMAIL_FROM, GIT_PATCH_0, KAM_NUMSUBJECT, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) 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-List-Received-Date: Thu, 30 Jun 2022 03:44:38 -0000 Just for clarities sake and so that if a future implementation is added we remember to add the check. --- sysdeps/x86_64/multiarch/ifunc-sse4_2.h | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/sysdeps/x86_64/multiarch/ifunc-sse4_2.h b/sysdeps/x86_64/multiarch/ifunc-sse4_2.h index ee36525bcf..4eb9cca7f0 100644 --- a/sysdeps/x86_64/multiarch/ifunc-sse4_2.h +++ b/sysdeps/x86_64/multiarch/ifunc-sse4_2.h @@ -27,6 +27,10 @@ IFUNC_SELECTOR (void) { const struct cpu_features* cpu_features = __get_cpu_features (); + /* This function uses slow sse4.2 instructions (pcmpstri) but since + there is no other optimized implementation keep using. If an + optimized fallback is added add a X86_ISA_CPU_FEATURE_ARCH_P + (cpu_features, Slow_SSE4_2) check. */ if (CPU_FEATURE_USABLE_P (cpu_features, SSE4_2)) return OPTIMIZE (sse42); -- 2.34.1