From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl1-x62d.google.com (mail-pl1-x62d.google.com [IPv6:2607:f8b0:4864:20::62d]) by sourceware.org (Postfix) with ESMTPS id 31DEA3858D3C for ; Thu, 24 Mar 2022 18:54:48 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 31DEA3858D3C Received: by mail-pl1-x62d.google.com with SMTP id j13so5706240plj.8 for ; Thu, 24 Mar 2022 11:54:48 -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=l4JesB9/P886+jpl0pQdhOdA5MiB432fIdwwUkEeB5s=; b=HDwWZ4C3B2QnmBfrojgg/0NTtrAJjZv52QgMytGKmqMEAYtOHMrg/I+qm/CspiW9vK McpLucniCsJ00L9yT8mpMyMizrzyfnT0FxzxTBRLmrIKk6HBIcecS4AulAvoNylE1UK8 y7C5G6Un1V/FUBl2QbZ34rVRbgQdmejBkZZBlqlbifSu1Y7o8vZdHI7LYo+tJuz2rBhW Yddyz7pMnZtUYuikAO+klaQvDN37QIe7agdn/EB1ZZfLp4ak19Tn8WhRyOwKK0Jhvq2t j8lPmlWltgVTRbhlkBV1mpD4Uq4PI3UzYhavTUvykJfD3b4IUwhWKYiXRTJ0esQE5TtV gs9g== X-Gm-Message-State: AOAM532oEoyhkW1+1QSRYto9pIl8Yl5ltEteJVyXCiKb/xtEQgiSta2t J6Mcz1aW/q5PLDMi6yAt5HA65jQWh/VP68BPWdI= X-Google-Smtp-Source: ABdhPJyMHyaMqqXJAJIQKkf3skl8mOE8YeIptJwBPp93ZR9jJFutJCAnnGIXnZ8DxvqrHlkeLjVs5h2CmNwU+yMecO4= X-Received: by 2002:a17:902:d508:b0:154:2f99:a52e with SMTP id b8-20020a170902d50800b001542f99a52emr7247743plg.102.1648148085301; Thu, 24 Mar 2022 11:54:45 -0700 (PDT) MIME-Version: 1.0 References: <20220323215734.3927131-1-goldstein.w.n@gmail.com> <20220323215734.3927131-4-goldstein.w.n@gmail.com> In-Reply-To: <20220323215734.3927131-4-goldstein.w.n@gmail.com> From: "H.J. Lu" Date: Thu, 24 Mar 2022 11:54:09 -0700 Message-ID: Subject: Re: [PATCH v1 04/23] x86: Code cleanup in strchr-evex and comment justifying branch To: Noah Goldstein Cc: GNU C Library , "Carlos O'Donell" Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-3026.1 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, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) 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, 24 Mar 2022 18:54:51 -0000 On Wed, Mar 23, 2022 at 2:58 PM Noah Goldstein wrote: > > Small code cleanup for size: -81 bytes. > > Add comment justifying using a branch to do NULL/non-null return. > > All string/memory tests pass and no regressions in benchtests. > > geometric_mean(N=20) of all benchmarks New / Original: .985 > --- > Geomtric Mean N=20 runs; All functions page aligned > length, alignment, pos, rand, seek_char/branch, max_char/perc-zero, New Time / Old Time > 2048, 0, 32, 0, 23, 127, 0.878 > 2048, 1, 32, 0, 23, 127, 0.88 > 2048, 0, 64, 0, 23, 127, 0.997 > 2048, 2, 64, 0, 23, 127, 1.001 > 2048, 0, 128, 0, 23, 127, 0.973 > 2048, 3, 128, 0, 23, 127, 0.971 > 2048, 0, 256, 0, 23, 127, 0.976 > 2048, 4, 256, 0, 23, 127, 0.973 > 2048, 0, 512, 0, 23, 127, 1.001 > 2048, 5, 512, 0, 23, 127, 1.004 > 2048, 0, 1024, 0, 23, 127, 1.005 > 2048, 6, 1024, 0, 23, 127, 1.007 > 2048, 0, 2048, 0, 23, 127, 1.035 > 2048, 7, 2048, 0, 23, 127, 1.03 > 4096, 0, 32, 0, 23, 127, 0.889 > 4096, 1, 32, 0, 23, 127, 0.891 > 4096, 0, 64, 0, 23, 127, 1.012 > 4096, 2, 64, 0, 23, 127, 1.017 > 4096, 0, 128, 0, 23, 127, 0.975 > 4096, 3, 128, 0, 23, 127, 0.974 > 4096, 0, 256, 0, 23, 127, 0.974 > 4096, 4, 256, 0, 23, 127, 0.972 > 4096, 0, 512, 0, 23, 127, 1.002 > 4096, 5, 512, 0, 23, 127, 1.016 > 4096, 0, 1024, 0, 23, 127, 1.009 > 4096, 6, 1024, 0, 23, 127, 1.008 > 4096, 0, 2048, 0, 23, 127, 1.003 > 4096, 7, 2048, 0, 23, 127, 1.004 > 256, 1, 64, 0, 23, 127, 0.993 > 256, 2, 64, 0, 23, 127, 0.999 > 256, 3, 64, 0, 23, 127, 0.992 > 256, 4, 64, 0, 23, 127, 0.99 > 256, 5, 64, 0, 23, 127, 0.99 > 256, 6, 64, 0, 23, 127, 0.994 > 256, 7, 64, 0, 23, 127, 0.991 > 512, 0, 256, 0, 23, 127, 0.971 > 512, 16, 256, 0, 23, 127, 0.971 > 512, 32, 256, 0, 23, 127, 1.005 > 512, 48, 256, 0, 23, 127, 0.998 > 512, 64, 256, 0, 23, 127, 1.001 > 512, 80, 256, 0, 23, 127, 1.002 > 512, 96, 256, 0, 23, 127, 1.005 > 512, 112, 256, 0, 23, 127, 1.012 > 1, 0, 0, 0, 23, 127, 1.024 > 2, 0, 1, 0, 23, 127, 0.991 > 3, 0, 2, 0, 23, 127, 0.997 > 4, 0, 3, 0, 23, 127, 0.984 > 5, 0, 4, 0, 23, 127, 0.993 > 6, 0, 5, 0, 23, 127, 0.985 > 7, 0, 6, 0, 23, 127, 0.979 > 8, 0, 7, 0, 23, 127, 0.975 > 9, 0, 8, 0, 23, 127, 0.965 > 10, 0, 9, 0, 23, 127, 0.957 > 11, 0, 10, 0, 23, 127, 0.979 > 12, 0, 11, 0, 23, 127, 0.987 > 13, 0, 12, 0, 23, 127, 1.023 > 14, 0, 13, 0, 23, 127, 0.997 > 15, 0, 14, 0, 23, 127, 0.983 > 16, 0, 15, 0, 23, 127, 0.987 > 17, 0, 16, 0, 23, 127, 0.993 > 18, 0, 17, 0, 23, 127, 0.985 > 19, 0, 18, 0, 23, 127, 0.999 > 20, 0, 19, 0, 23, 127, 0.998 > 21, 0, 20, 0, 23, 127, 0.983 > 22, 0, 21, 0, 23, 127, 0.983 > 23, 0, 22, 0, 23, 127, 1.002 > 24, 0, 23, 0, 23, 127, 1.0 > 25, 0, 24, 0, 23, 127, 1.002 > 26, 0, 25, 0, 23, 127, 0.984 > 27, 0, 26, 0, 23, 127, 0.994 > 28, 0, 27, 0, 23, 127, 0.995 > 29, 0, 28, 0, 23, 127, 1.017 > 30, 0, 29, 0, 23, 127, 1.009 > 31, 0, 30, 0, 23, 127, 1.001 > 32, 0, 31, 0, 23, 127, 1.021 > 2048, 0, 32, 0, 0, 127, 0.899 > 2048, 1, 32, 0, 0, 127, 0.93 > 2048, 0, 64, 0, 0, 127, 1.009 > 2048, 2, 64, 0, 0, 127, 1.023 > 2048, 0, 128, 0, 0, 127, 0.973 > 2048, 3, 128, 0, 0, 127, 0.975 > 2048, 0, 256, 0, 0, 127, 0.974 > 2048, 4, 256, 0, 0, 127, 0.97 > 2048, 0, 512, 0, 0, 127, 0.999 > 2048, 5, 512, 0, 0, 127, 1.004 > 2048, 0, 1024, 0, 0, 127, 1.008 > 2048, 6, 1024, 0, 0, 127, 1.008 > 2048, 0, 2048, 0, 0, 127, 0.996 > 2048, 7, 2048, 0, 0, 127, 1.002 > 4096, 0, 32, 0, 0, 127, 0.872 > 4096, 1, 32, 0, 0, 127, 0.881 > 4096, 0, 64, 0, 0, 127, 1.006 > 4096, 2, 64, 0, 0, 127, 1.005 > 4096, 0, 128, 0, 0, 127, 0.973 > 4096, 3, 128, 0, 0, 127, 0.974 > 4096, 0, 256, 0, 0, 127, 0.969 > 4096, 4, 256, 0, 0, 127, 0.971 > 4096, 0, 512, 0, 0, 127, 1.0 > 4096, 5, 512, 0, 0, 127, 1.005 > 4096, 0, 1024, 0, 0, 127, 1.007 > 4096, 6, 1024, 0, 0, 127, 1.009 > 4096, 0, 2048, 0, 0, 127, 1.005 > 4096, 7, 2048, 0, 0, 127, 1.007 > 256, 1, 64, 0, 0, 127, 0.994 > 256, 2, 64, 0, 0, 127, 1.008 > 256, 3, 64, 0, 0, 127, 1.019 > 256, 4, 64, 0, 0, 127, 0.991 > 256, 5, 64, 0, 0, 127, 0.992 > 256, 6, 64, 0, 0, 127, 0.991 > 256, 7, 64, 0, 0, 127, 0.988 > 512, 0, 256, 0, 0, 127, 0.971 > 512, 16, 256, 0, 0, 127, 0.967 > 512, 32, 256, 0, 0, 127, 1.005 > 512, 48, 256, 0, 0, 127, 1.001 > 512, 64, 256, 0, 0, 127, 1.009 > 512, 80, 256, 0, 0, 127, 1.008 > 512, 96, 256, 0, 0, 127, 1.009 > 512, 112, 256, 0, 0, 127, 1.016 > 1, 0, 0, 0, 0, 127, 1.038 > 2, 0, 1, 0, 0, 127, 1.009 > 3, 0, 2, 0, 0, 127, 0.992 > 4, 0, 3, 0, 0, 127, 1.004 > 5, 0, 4, 0, 0, 127, 0.966 > 6, 0, 5, 0, 0, 127, 0.968 > 7, 0, 6, 0, 0, 127, 1.004 > 8, 0, 7, 0, 0, 127, 0.99 > 9, 0, 8, 0, 0, 127, 0.958 > 10, 0, 9, 0, 0, 127, 0.96 > 11, 0, 10, 0, 0, 127, 0.948 > 12, 0, 11, 0, 0, 127, 0.984 > 13, 0, 12, 0, 0, 127, 0.967 > 14, 0, 13, 0, 0, 127, 0.993 > 15, 0, 14, 0, 0, 127, 0.991 > 16, 0, 15, 0, 0, 127, 1.0 > 17, 0, 16, 0, 0, 127, 0.982 > 18, 0, 17, 0, 0, 127, 0.977 > 19, 0, 18, 0, 0, 127, 0.987 > 20, 0, 19, 0, 0, 127, 0.978 > 21, 0, 20, 0, 0, 127, 1.0 > 22, 0, 21, 0, 0, 127, 0.99 > 23, 0, 22, 0, 0, 127, 0.988 > 24, 0, 23, 0, 0, 127, 0.997 > 25, 0, 24, 0, 0, 127, 1.003 > 26, 0, 25, 0, 0, 127, 1.004 > 27, 0, 26, 0, 0, 127, 0.982 > 28, 0, 27, 0, 0, 127, 0.972 > 29, 0, 28, 0, 0, 127, 0.978 > 30, 0, 29, 0, 0, 127, 0.992 > 31, 0, 30, 0, 0, 127, 0.986 > 32, 0, 31, 0, 0, 127, 1.0 > > 16, 0, 15, 1, 1, 0, 0.997 > 16, 0, 15, 1, 0, 0, 1.001 > 16, 0, 15, 1, 1, 0.1, 0.984 > 16, 0, 15, 1, 0, 0.1, 0.999 > 16, 0, 15, 1, 1, 0.25, 0.929 > 16, 0, 15, 1, 0, 0.25, 1.001 > 16, 0, 15, 1, 1, 0.33, 0.892 > 16, 0, 15, 1, 0, 0.33, 0.996 > 16, 0, 15, 1, 1, 0.5, 0.897 > 16, 0, 15, 1, 0, 0.5, 1.009 > 16, 0, 15, 1, 1, 0.66, 0.882 > 16, 0, 15, 1, 0, 0.66, 0.967 > 16, 0, 15, 1, 1, 0.75, 0.919 > 16, 0, 15, 1, 0, 0.75, 1.027 > 16, 0, 15, 1, 1, 0.9, 0.949 > 16, 0, 15, 1, 0, 0.9, 1.021 > 16, 0, 15, 1, 1, 1, 0.998 > 16, 0, 15, 1, 0, 1, 0.999 > > sysdeps/x86_64/multiarch/strchr-evex.S | 146 ++++++++++++++----------- > 1 file changed, 80 insertions(+), 66 deletions(-) > > diff --git a/sysdeps/x86_64/multiarch/strchr-evex.S b/sysdeps/x86_64/multiarch/strchr-evex.S > index f62cd9d144..ec739fb8f9 100644 > --- a/sysdeps/x86_64/multiarch/strchr-evex.S > +++ b/sysdeps/x86_64/multiarch/strchr-evex.S > @@ -30,6 +30,7 @@ > # ifdef USE_AS_WCSCHR > # define VPBROADCAST vpbroadcastd > # define VPCMP vpcmpd > +# define VPTESTN vptestnmd > # define VPMINU vpminud > # define CHAR_REG esi > # define SHIFT_REG ecx > @@ -37,6 +38,7 @@ > # else > # define VPBROADCAST vpbroadcastb > # define VPCMP vpcmpb > +# define VPTESTN vptestnmb > # define VPMINU vpminub > # define CHAR_REG sil > # define SHIFT_REG edx > @@ -61,13 +63,11 @@ > # define CHAR_PER_VEC (VEC_SIZE / CHAR_SIZE) > > .section .text.evex,"ax",@progbits > -ENTRY (STRCHR) > +ENTRY_P2ALIGN (STRCHR, 5) > /* Broadcast CHAR to YMM0. */ > VPBROADCAST %esi, %YMM0 > movl %edi, %eax > andl $(PAGE_SIZE - 1), %eax > - vpxorq %XMMZERO, %XMMZERO, %XMMZERO > - > /* Check if we cross page boundary with one vector load. > Otherwise it is safe to use an unaligned load. */ > cmpl $(PAGE_SIZE - VEC_SIZE), %eax > @@ -81,49 +81,35 @@ ENTRY (STRCHR) > vpxorq %YMM1, %YMM0, %YMM2 > VPMINU %YMM2, %YMM1, %YMM2 > /* Each bit in K0 represents a CHAR or a null byte in YMM1. */ > - VPCMP $0, %YMMZERO, %YMM2, %k0 > + VPTESTN %YMM2, %YMM2, %k0 > kmovd %k0, %eax > testl %eax, %eax > jz L(aligned_more) > tzcntl %eax, %eax > +# ifndef USE_AS_STRCHRNUL > + /* Found CHAR or the null byte. */ > + cmp (%rdi, %rax, CHAR_SIZE), %CHAR_REG > + /* NB: Use a branch instead of cmovcc here. The expectation is > + that with strchr the user will branch based on input being > + null. Since this branch will be 100% predictive of the user > + branch a branch miss here should save what otherwise would > + be branch miss in the user code. Otherwise using a branch 1) > + saves code size and 2) is faster in highly predictable > + environments. */ > + jne L(zero) > +# endif > # ifdef USE_AS_WCSCHR > /* NB: Multiply wchar_t count by 4 to get the number of bytes. > */ > leaq (%rdi, %rax, CHAR_SIZE), %rax > # else > addq %rdi, %rax > -# endif > -# ifndef USE_AS_STRCHRNUL > - /* Found CHAR or the null byte. */ > - cmp (%rax), %CHAR_REG > - jne L(zero) > # endif > ret > > - /* .p2align 5 helps keep performance more consistent if ENTRY() > - alignment % 32 was either 16 or 0. As well this makes the > - alignment % 32 of the loop_4x_vec fixed which makes tuning it > - easier. */ > - .p2align 5 > -L(first_vec_x3): > - tzcntl %eax, %eax > -# ifndef USE_AS_STRCHRNUL > - /* Found CHAR or the null byte. */ > - cmp (VEC_SIZE * 3)(%rdi, %rax, CHAR_SIZE), %CHAR_REG > - jne L(zero) > -# endif > - /* NB: Multiply sizeof char type (1 or 4) to get the number of > - bytes. */ > - leaq (VEC_SIZE * 3)(%rdi, %rax, CHAR_SIZE), %rax > - ret > > -# ifndef USE_AS_STRCHRNUL > -L(zero): > - xorl %eax, %eax > - ret > -# endif > > - .p2align 4 > + .p2align 4,, 10 > L(first_vec_x4): > # ifndef USE_AS_STRCHRNUL > /* Check to see if first match was CHAR (k0) or null (k1). */ > @@ -144,9 +130,18 @@ L(first_vec_x4): > leaq (VEC_SIZE * 4)(%rdi, %rax, CHAR_SIZE), %rax > ret > > +# ifndef USE_AS_STRCHRNUL > +L(zero): > + xorl %eax, %eax > + ret > +# endif > + > + > .p2align 4 > L(first_vec_x1): > - tzcntl %eax, %eax > + /* Use bsf here to save 1-byte keeping keeping the block in 1x > + fetch block. eax guranteed non-zero. */ > + bsfl %eax, %eax > # ifndef USE_AS_STRCHRNUL > /* Found CHAR or the null byte. */ > cmp (VEC_SIZE)(%rdi, %rax, CHAR_SIZE), %CHAR_REG > @@ -158,7 +153,7 @@ L(first_vec_x1): > leaq (VEC_SIZE)(%rdi, %rax, CHAR_SIZE), %rax > ret > > - .p2align 4 > + .p2align 4,, 10 > L(first_vec_x2): > # ifndef USE_AS_STRCHRNUL > /* Check to see if first match was CHAR (k0) or null (k1). */ > @@ -179,6 +174,21 @@ L(first_vec_x2): > leaq (VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax > ret > > + .p2align 4,, 10 > +L(first_vec_x3): > + /* Use bsf here to save 1-byte keeping keeping the block in 1x > + fetch block. eax guranteed non-zero. */ > + bsfl %eax, %eax > +# ifndef USE_AS_STRCHRNUL > + /* Found CHAR or the null byte. */ > + cmp (VEC_SIZE * 3)(%rdi, %rax, CHAR_SIZE), %CHAR_REG > + jne L(zero) > +# endif > + /* NB: Multiply sizeof char type (1 or 4) to get the number of > + bytes. */ > + leaq (VEC_SIZE * 3)(%rdi, %rax, CHAR_SIZE), %rax > + ret > + > .p2align 4 > L(aligned_more): > /* Align data to VEC_SIZE. */ > @@ -195,7 +205,7 @@ L(cross_page_continue): > vpxorq %YMM1, %YMM0, %YMM2 > VPMINU %YMM2, %YMM1, %YMM2 > /* Each bit in K0 represents a CHAR or a null byte in YMM1. */ > - VPCMP $0, %YMMZERO, %YMM2, %k0 > + VPTESTN %YMM2, %YMM2, %k0 > kmovd %k0, %eax > testl %eax, %eax > jnz L(first_vec_x1) > @@ -206,7 +216,7 @@ L(cross_page_continue): > /* Each bit in K0 represents a CHAR in YMM1. */ > VPCMP $0, %YMM1, %YMM0, %k0 > /* Each bit in K1 represents a CHAR in YMM1. */ > - VPCMP $0, %YMM1, %YMMZERO, %k1 > + VPTESTN %YMM1, %YMM1, %k1 > kortestd %k0, %k1 > jnz L(first_vec_x2) > > @@ -215,7 +225,7 @@ L(cross_page_continue): > vpxorq %YMM1, %YMM0, %YMM2 > VPMINU %YMM2, %YMM1, %YMM2 > /* Each bit in K0 represents a CHAR or a null byte in YMM1. */ > - VPCMP $0, %YMMZERO, %YMM2, %k0 > + VPTESTN %YMM2, %YMM2, %k0 > kmovd %k0, %eax > testl %eax, %eax > jnz L(first_vec_x3) > @@ -224,7 +234,7 @@ L(cross_page_continue): > /* Each bit in K0 represents a CHAR in YMM1. */ > VPCMP $0, %YMM1, %YMM0, %k0 > /* Each bit in K1 represents a CHAR in YMM1. */ > - VPCMP $0, %YMM1, %YMMZERO, %k1 > + VPTESTN %YMM1, %YMM1, %k1 > kortestd %k0, %k1 > jnz L(first_vec_x4) > > @@ -265,33 +275,33 @@ L(loop_4x_vec): > VPMINU %YMM3, %YMM4, %YMM4 > VPMINU %YMM2, %YMM4, %YMM4{%k4}{z} > > - VPCMP $0, %YMMZERO, %YMM4, %k1 > + VPTESTN %YMM4, %YMM4, %k1 > kmovd %k1, %ecx > subq $-(VEC_SIZE * 4), %rdi > testl %ecx, %ecx > jz L(loop_4x_vec) > > - VPCMP $0, %YMMZERO, %YMM1, %k0 > + VPTESTN %YMM1, %YMM1, %k0 > kmovd %k0, %eax > testl %eax, %eax > jnz L(last_vec_x1) > > - VPCMP $0, %YMMZERO, %YMM2, %k0 > + VPTESTN %YMM2, %YMM2, %k0 > kmovd %k0, %eax > testl %eax, %eax > jnz L(last_vec_x2) > > - VPCMP $0, %YMMZERO, %YMM3, %k0 > + VPTESTN %YMM3, %YMM3, %k0 > kmovd %k0, %eax > /* Combine YMM3 matches (eax) with YMM4 matches (ecx). */ > # ifdef USE_AS_WCSCHR > sall $8, %ecx > orl %ecx, %eax > - tzcntl %eax, %eax > + bsfl %eax, %eax > # else > salq $32, %rcx > orq %rcx, %rax > - tzcntq %rax, %rax > + bsfq %rax, %rax > # endif > # ifndef USE_AS_STRCHRNUL > /* Check if match was CHAR or null. */ > @@ -303,28 +313,28 @@ L(loop_4x_vec): > leaq (VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax > ret > > -# ifndef USE_AS_STRCHRNUL > -L(zero_end): > - xorl %eax, %eax > - ret > + .p2align 4,, 8 > +L(last_vec_x1): > + bsfl %eax, %eax > +# ifdef USE_AS_WCSCHR > + /* NB: Multiply wchar_t count by 4 to get the number of bytes. > + */ > + leaq (%rdi, %rax, CHAR_SIZE), %rax > +# else > + addq %rdi, %rax > # endif > > - .p2align 4 > -L(last_vec_x1): > - tzcntl %eax, %eax > # ifndef USE_AS_STRCHRNUL > /* Check if match was null. */ > - cmp (%rdi, %rax, CHAR_SIZE), %CHAR_REG > + cmp (%rax), %CHAR_REG > jne L(zero_end) > # endif > - /* NB: Multiply sizeof char type (1 or 4) to get the number of > - bytes. */ > - leaq (%rdi, %rax, CHAR_SIZE), %rax > + > ret > > - .p2align 4 > + .p2align 4,, 8 > L(last_vec_x2): > - tzcntl %eax, %eax > + bsfl %eax, %eax > # ifndef USE_AS_STRCHRNUL > /* Check if match was null. */ > cmp (VEC_SIZE)(%rdi, %rax, CHAR_SIZE), %CHAR_REG > @@ -336,7 +346,7 @@ L(last_vec_x2): > ret > > /* Cold case for crossing page with first load. */ > - .p2align 4 > + .p2align 4,, 8 > L(cross_page_boundary): > movq %rdi, %rdx > /* Align rdi. */ > @@ -346,9 +356,9 @@ L(cross_page_boundary): > vpxorq %YMM1, %YMM0, %YMM2 > VPMINU %YMM2, %YMM1, %YMM2 > /* Each bit in K0 represents a CHAR or a null byte in YMM1. */ > - VPCMP $0, %YMMZERO, %YMM2, %k0 > + VPTESTN %YMM2, %YMM2, %k0 > kmovd %k0, %eax > - /* Remove the leading bits. */ > + /* Remove the leading bits. */ > # ifdef USE_AS_WCSCHR > movl %edx, %SHIFT_REG > /* NB: Divide shift count by 4 since each bit in K1 represent 4 > @@ -360,20 +370,24 @@ L(cross_page_boundary): > /* If eax is zero continue. */ > testl %eax, %eax > jz L(cross_page_continue) > - tzcntl %eax, %eax > -# ifndef USE_AS_STRCHRNUL > - /* Check to see if match was CHAR or null. */ > - cmp (%rdx, %rax, CHAR_SIZE), %CHAR_REG > - jne L(zero_end) > -# endif > + bsfl %eax, %eax > + > # ifdef USE_AS_WCSCHR > /* NB: Multiply wchar_t count by 4 to get the number of > bytes. */ > leaq (%rdx, %rax, CHAR_SIZE), %rax > # else > addq %rdx, %rax > +# endif > +# ifndef USE_AS_STRCHRNUL > + /* Check to see if match was CHAR or null. */ > + cmp (%rax), %CHAR_REG > + je L(cross_page_ret) > +L(zero_end): > + xorl %eax, %eax > +L(cross_page_ret): > # endif > ret > > END (STRCHR) > -# endif > +#endif > -- > 2.25.1 > LGTM. Reviewed-by: H.J. Lu Thanks. -- H.J.