From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf1-x433.google.com (mail-pf1-x433.google.com [IPv6:2607:f8b0:4864:20::433]) by sourceware.org (Postfix) with ESMTPS id 9C8C0384D14A for ; Wed, 29 Jun 2022 22:13:23 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 9C8C0384D14A Received: by mail-pf1-x433.google.com with SMTP id x138so13670312pfc.3 for ; Wed, 29 Jun 2022 15:13:23 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=/JhciMAPp6DyFS0ejAcgIzTW/TxdfTSQ9sQ39lvT2Cg=; b=I+TBQQmQ3cBSi9HywrO1BhG8AqsVxHpsXkDoBx4umMdwWoCSw21fFJQaTuiyDM07en 0zkkbxBMPdblpsL8SNYI9MLfd5kBbT4xB5Ka1ojzj3whIpkdIXhX2fv2hbvc8gqSO1YR 6v83eV0mBwhQmGPRUHA6FR52OHfmLlARhAoy0q9f/wgYL0rqfcyUWlP1UhMEDT9tnYIf NpYm8N8LJlZnyS2nzGGDVPVHeDcTxbGLoS9LVO61inw8rDVUXvJ2Ii4yCj/+2pfMkm4U HZcpK/NXBJIhTNvW44u8ut+zf56u7djGooSfkMJ89qqAO34/PoOtiIm7I832/+wTFH2E FB1A== X-Gm-Message-State: AJIora8PQ23iwaz0VB+i0lviVb0VrWD490JHMvQ+UVOuWhJeyEbMFEjZ xnNL14GCWorR77ZOsL2DHKyjt8QwIj8798mDmh4= X-Google-Smtp-Source: AGRyM1uX4ENqLpqdEQgM9LWaJ8uXYmcaB84PYnymLgK8lk5vLwbP8ml3sdYDhpCk46kZT+Ajgzs20+4wja5yKq5OQ2g= X-Received: by 2002:a05:6a00:1592:b0:525:7809:42c6 with SMTP id u18-20020a056a00159200b00525780942c6mr11306422pfk.64.1656540802543; Wed, 29 Jun 2022 15:13:22 -0700 (PDT) MIME-Version: 1.0 References: <20220628152717.17838-1-goldstein.w.n@gmail.com> <20220629220552.1241553-1-goldstein.w.n@gmail.com> In-Reply-To: <20220629220552.1241553-1-goldstein.w.n@gmail.com> From: "H.J. Lu" Date: Wed, 29 Jun 2022 15:12:46 -0700 Message-ID: Subject: Re: [PATCH v2 1/2] x86: Add comment explaining no Slow_SSE4_2 check in ifunc-sse4_2 To: Noah Goldstein Cc: GNU C Library , "Carlos O'Donell" Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-3024.7 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: Wed, 29 Jun 2022 22:13:25 -0000 On Wed, Jun 29, 2022 at 3:05 PM Noah Goldstein wrote: > > 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 | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/sysdeps/x86_64/multiarch/ifunc-sse4_2.h b/sysdeps/x86_64/multiarch/ifunc-sse4_2.h > index ee36525bcf..973041d23b 100644 > --- a/sysdeps/x86_64/multiarch/ifunc-sse4_2.h > +++ b/sysdeps/x86_64/multiarch/ifunc-sse4_2.h > @@ -27,7 +27,11 @@ IFUNC_SELECTOR (void) > { > const struct cpu_features* cpu_features = __get_cpu_features (); > > - if (CPU_FEATURE_USABLE_P (cpu_features, SSE4_2)) > + /* 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 (ISA_CPU_FEATURE_USABLE_P (cpu_features, SSE4_2)) > return OPTIMIZE (sse42); > > return OPTIMIZE (generic); > -- > 2.34.1 > LGTM. Thanks. -- H.J.