From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-vs1-xe30.google.com (mail-vs1-xe30.google.com [IPv6:2607:f8b0:4864:20::e30]) by sourceware.org (Postfix) with ESMTPS id D46563858C56; Wed, 4 May 2022 05:38:53 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org D46563858C56 Received: by mail-vs1-xe30.google.com with SMTP id q2so252359vsr.5; Tue, 03 May 2022 22:38:53 -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=XN43XK7CMbzy9hhNlwIzhYHK8sGnqmndAFfBiL+Jim8=; b=i8xPlfyL5k4AiJ9g1yZCBwUyPvtiua9z0onMCzE7nrnN1m7KbpZNZXJ9aHQC41poap KrV2vmBWUkCBCRFezlIOcMshJ3UXa/kxmcODbrXJyLlcd0n6Klon/CZhegHcSjUpi1h4 VYbORuqq9wBasJpSDvAwtVkvPgpQ2C2qJbxpRgI6+EJdxaF6rn08bPuTMo2esBLLDqmg n50plHUCFKl9yvtc7mQfkyZTX0864mVHBWqfgHFhmaeDilx1Zu62r47J9N+k1CJ39OdJ ZmyYghGxfTZiASyFdMaKWGu9XbGY5THk1A9K5Vfv5rl32FFQCAZ1TLhBcDmWkndzJhNQ mhzw== X-Gm-Message-State: AOAM530YrwYv8E18YFqVKKZXV3zHAdYaaYWvF15sgn6kWn5fV/T1VPnR P7szdzIAuRmZ2vfj+cEI73WL+PTRX0KPBKAftwU= X-Google-Smtp-Source: ABdhPJyKSYM+bFjEJxOu9/gdz8cWD4//qlRiJln14VQJ1FMeODLZ7WqGCA3UC/3daL6jKsgVxSubTt4fpZ9MCWL/jyI= X-Received: by 2002:a67:ef0a:0:b0:32d:4bb9:23f with SMTP id j10-20020a67ef0a000000b0032d4bb9023fmr3401416vsr.47.1651642732344; Tue, 03 May 2022 22:38:52 -0700 (PDT) MIME-Version: 1.0 References: <20220203214215.3275256-1-goldstein.w.n@gmail.com> <20220203214215.3275256-4-goldstein.w.n@gmail.com> In-Reply-To: From: Sunil Pandey Date: Tue, 3 May 2022 22:38:15 -0700 Message-ID: Subject: Re: [PATCH v4 4/5] x86: Optimize strcmp-evex.S To: "H.J. Lu" , Libc-stable Mailing List Cc: Noah Goldstein , GNU C Library Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-7.5 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, FREEMAIL_ENVFROM_END_DIGIT, FREEMAIL_FROM, GIT_PATCH_0, HK_RANDOM_ENVFROM, HK_RANDOM_FROM, 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-stable@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-stable mailing list List-Unsubscribe: , List-Archive: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 04 May 2022 05:38:59 -0000 On Thu, Feb 3, 2022 at 2:32 PM H.J. Lu via Libc-alpha wrote: > > On Thu, Feb 3, 2022 at 1:42 PM Noah Goldstein wrote: > > > > Optimization are primarily to the loop logic and how the page cross > > logic interacts with the loop. > > > > The page cross logic is at times more expensive for short strings near > > the end of a page but not crossing the page. This is done to retest > > the page cross conditions with a non-faulty check and to improve the > > logic for entering the loop afterwards. This is only particular cases, > > however, and is general made up for by more than 10x improvements on > > the transition from the page cross -> loop case. > > > > The non-page cross cases as well are nearly universally improved. > > > > test-strcmp, test-strncmp, test-wcscmp, and test-wcsncmp all pass. > > > > Signed-off-by: Noah Goldstein > > --- > > sysdeps/x86_64/multiarch/strcmp-evex.S | 1712 +++++++++++++----------- > > 1 file changed, 919 insertions(+), 793 deletions(-) > > > > diff --git a/sysdeps/x86_64/multiarch/strcmp-evex.S b/sysdeps/x86_64/multiarch/strcmp-evex.S > > index 0cd939d5af..e5070f3d53 100644 > > --- a/sysdeps/x86_64/multiarch/strcmp-evex.S > > +++ b/sysdeps/x86_64/multiarch/strcmp-evex.S > > @@ -26,54 +26,69 @@ > > > > # define PAGE_SIZE 4096 > > > > -/* VEC_SIZE = Number of bytes in a ymm register */ > > + /* VEC_SIZE = Number of bytes in a ymm register. */ > > # define VEC_SIZE 32 > > +# define CHAR_PER_VEC (VEC_SIZE / SIZE_OF_CHAR) > > > > -/* Shift for dividing by (VEC_SIZE * 4). */ > > -# define DIVIDE_BY_VEC_4_SHIFT 7 > > -# if (VEC_SIZE * 4) != (1 << DIVIDE_BY_VEC_4_SHIFT) > > -# error (VEC_SIZE * 4) != (1 << DIVIDE_BY_VEC_4_SHIFT) > > -# endif > > - > > -# define VMOVU vmovdqu64 > > -# define VMOVA vmovdqa64 > > +# define VMOVU vmovdqu64 > > +# define VMOVA vmovdqa64 > > > > # ifdef USE_AS_WCSCMP > > -/* Compare packed dwords. */ > > -# define VPCMP vpcmpd > > +# define TESTEQ subl $0xff, > > + /* Compare packed dwords. */ > > +# define VPCMP vpcmpd > > # define VPMINU vpminud > > # define VPTESTM vptestmd > > -# define SHIFT_REG32 r8d > > -# define SHIFT_REG64 r8 > > -/* 1 dword char == 4 bytes. */ > > + /* 1 dword char == 4 bytes. */ > > # define SIZE_OF_CHAR 4 > > # else > > -/* Compare packed bytes. */ > > -# define VPCMP vpcmpb > > +# define TESTEQ incl > > + /* Compare packed bytes. */ > > +# define VPCMP vpcmpb > > # define VPMINU vpminub > > # define VPTESTM vptestmb > > -# define SHIFT_REG32 ecx > > -# define SHIFT_REG64 rcx > > -/* 1 byte char == 1 byte. */ > > + /* 1 byte char == 1 byte. */ > > # define SIZE_OF_CHAR 1 > > # endif > > > > +# ifdef USE_AS_STRNCMP > > +# define LOOP_REG r9d > > +# define LOOP_REG64 r9 > > + > > +# define OFFSET_REG8 r9b > > +# define OFFSET_REG r9d > > +# define OFFSET_REG64 r9 > > +# else > > +# define LOOP_REG edx > > +# define LOOP_REG64 rdx > > + > > +# define OFFSET_REG8 dl > > +# define OFFSET_REG edx > > +# define OFFSET_REG64 rdx > > +# endif > > + > > +# if defined USE_AS_STRNCMP || defined USE_AS_WCSCMP > > +# define VEC_OFFSET 0 > > +# else > > +# define VEC_OFFSET (-VEC_SIZE) > > +# endif > > + > > # define XMMZERO xmm16 > > -# define XMM0 xmm17 > > -# define XMM1 xmm18 > > +# define XMM0 xmm17 > > +# define XMM1 xmm18 > > > > # define YMMZERO ymm16 > > -# define YMM0 ymm17 > > -# define YMM1 ymm18 > > -# define YMM2 ymm19 > > -# define YMM3 ymm20 > > -# define YMM4 ymm21 > > -# define YMM5 ymm22 > > -# define YMM6 ymm23 > > -# define YMM7 ymm24 > > -# define YMM8 ymm25 > > -# define YMM9 ymm26 > > -# define YMM10 ymm27 > > +# define YMM0 ymm17 > > +# define YMM1 ymm18 > > +# define YMM2 ymm19 > > +# define YMM3 ymm20 > > +# define YMM4 ymm21 > > +# define YMM5 ymm22 > > +# define YMM6 ymm23 > > +# define YMM7 ymm24 > > +# define YMM8 ymm25 > > +# define YMM9 ymm26 > > +# define YMM10 ymm27 > > > > /* Warning! > > wcscmp/wcsncmp have to use SIGNED comparison for elements. > > @@ -96,985 +111,1096 @@ > > the maximum offset is reached before a difference is found, zero is > > returned. */ > > > > - .section .text.evex,"ax",@progbits > > -ENTRY (STRCMP) > > + .section .text.evex, "ax", @progbits > > +ENTRY(STRCMP) > > # ifdef USE_AS_STRNCMP > > - /* Check for simple cases (0 or 1) in offset. */ > > - cmp $1, %RDX_LP > > - je L(char0) > > - jb L(zero) > > -# ifdef USE_AS_WCSCMP > > -# ifndef __ILP32__ > > - movq %rdx, %rcx > > - /* Check if length could overflow when multiplied by > > - sizeof(wchar_t). Checking top 8 bits will cover all potential > > - overflow cases as well as redirect cases where its impossible to > > - length to bound a valid memory region. In these cases just use > > - 'wcscmp'. */ > > - shrq $56, %rcx > > - jnz __wcscmp_evex > > -# endif > > - /* Convert units: from wide to byte char. */ > > - shl $2, %RDX_LP > > +# ifdef __ILP32__ > > + /* Clear the upper 32 bits. */ > > + movl %edx, %rdx > > # endif > > - /* Register %r11 tracks the maximum offset. */ > > - mov %RDX_LP, %R11_LP > > + cmp $1, %RDX_LP > > + /* Signed comparison intentional. We use this branch to also > > + test cases where length >= 2^63. These very large sizes can be > > + handled with strcmp as there is no way for that length to > > + actually bound the buffer. */ > > + jle L(one_or_less) > > # endif > > movl %edi, %eax > > - xorl %edx, %edx > > - /* Make %XMMZERO (%YMMZERO) all zeros in this function. */ > > - vpxorq %XMMZERO, %XMMZERO, %XMMZERO > > orl %esi, %eax > > - andl $(PAGE_SIZE - 1), %eax > > - cmpl $(PAGE_SIZE - (VEC_SIZE * 4)), %eax > > - jg L(cross_page) > > - /* Start comparing 4 vectors. */ > > + /* Shift out the bits irrelivant to page boundary ([63:12]). */ > > + sall $20, %eax > > + /* Check if s1 or s2 may cross a page in next 4x VEC loads. */ > > + cmpl $((PAGE_SIZE -(VEC_SIZE * 4)) << 20), %eax > > + ja L(page_cross) > > + > > +L(no_page_cross): > > + /* Safe to compare 4x vectors. */ > > VMOVU (%rdi), %YMM0 > > - > > - /* Each bit set in K2 represents a non-null CHAR in YMM0. */ > > VPTESTM %YMM0, %YMM0, %k2 > > - > > /* Each bit cleared in K1 represents a mismatch or a null CHAR > > in YMM0 and 32 bytes at (%rsi). */ > > VPCMP $0, (%rsi), %YMM0, %k1{%k2} > > - > > kmovd %k1, %ecx > > -# ifdef USE_AS_WCSCMP > > - subl $0xff, %ecx > > -# else > > - incl %ecx > > -# endif > > - je L(next_3_vectors) > > - tzcntl %ecx, %edx > > -# ifdef USE_AS_WCSCMP > > - /* NB: Multiply wchar_t count by 4 to get the number of bytes. */ > > - sall $2, %edx > > -# endif > > # ifdef USE_AS_STRNCMP > > - /* Return 0 if the mismatched index (%rdx) is after the maximum > > - offset (%r11). */ > > - cmpq %r11, %rdx > > - jae L(zero) > > + cmpq $CHAR_PER_VEC, %rdx > > + jbe L(vec_0_test_len) > > # endif > > + > > + /* TESTEQ is `incl` for strcmp/strncmp and `subl $0xff` for > > + wcscmp/wcsncmp. */ > > + > > + /* All 1s represents all equals. TESTEQ will overflow to zero in > > + all equals case. Otherwise 1s will carry until position of first > > + mismatch. */ > > + TESTEQ %ecx > > + jz L(more_3x_vec) > > + > > + .p2align 4,, 4 > > +L(return_vec_0): > > + tzcntl %ecx, %ecx > > # ifdef USE_AS_WCSCMP > > + movl (%rdi, %rcx, SIZE_OF_CHAR), %edx > > xorl %eax, %eax > > - movl (%rdi, %rdx), %ecx > > - cmpl (%rsi, %rdx), %ecx > > - je L(return) > > -L(wcscmp_return): > > + cmpl (%rsi, %rcx, SIZE_OF_CHAR), %edx > > + je L(ret0) > > setl %al > > negl %eax > > orl $1, %eax > > -L(return): > > # else > > - movzbl (%rdi, %rdx), %eax > > - movzbl (%rsi, %rdx), %edx > > - subl %edx, %eax > > + movzbl (%rdi, %rcx), %eax > > + movzbl (%rsi, %rcx), %ecx > > + subl %ecx, %eax > > # endif > > +L(ret0): > > ret > > > > -L(return_vec_size): > > - tzcntl %ecx, %edx > > -# ifdef USE_AS_WCSCMP > > - /* NB: Multiply wchar_t count by 4 to get the number of bytes. */ > > - sall $2, %edx > > -# endif > > # ifdef USE_AS_STRNCMP > > - /* Return 0 if the mismatched index (%rdx + VEC_SIZE) is after > > - the maximum offset (%r11). */ > > - addq $VEC_SIZE, %rdx > > - cmpq %r11, %rdx > > - jae L(zero) > > -# ifdef USE_AS_WCSCMP > > + .p2align 4,, 4 > > +L(vec_0_test_len): > > + notl %ecx > > + bzhil %edx, %ecx, %eax > > + jnz L(return_vec_0) > > + /* Align if will cross fetch block. */ > > + .p2align 4,, 2 > > +L(ret_zero): > > xorl %eax, %eax > > - movl (%rdi, %rdx), %ecx > > - cmpl (%rsi, %rdx), %ecx > > - jne L(wcscmp_return) > > -# else > > - movzbl (%rdi, %rdx), %eax > > - movzbl (%rsi, %rdx), %edx > > - subl %edx, %eax > > -# endif > > -# else > > + ret > > + > > + .p2align 4,, 5 > > +L(one_or_less): > > + jb L(ret_zero) > > # ifdef USE_AS_WCSCMP > > + /* 'nbe' covers the case where length is negative (large > > + unsigned). */ > > + jnbe __wcscmp_evex > > + movl (%rdi), %edx > > xorl %eax, %eax > > - movl VEC_SIZE(%rdi, %rdx), %ecx > > - cmpl VEC_SIZE(%rsi, %rdx), %ecx > > - jne L(wcscmp_return) > > + cmpl (%rsi), %edx > > + je L(ret1) > > + setl %al > > + negl %eax > > + orl $1, %eax > > # else > > - movzbl VEC_SIZE(%rdi, %rdx), %eax > > - movzbl VEC_SIZE(%rsi, %rdx), %edx > > - subl %edx, %eax > > + /* 'nbe' covers the case where length is negative (large > > + unsigned). */ > > + jnbe __strcmp_evex > > + movzbl (%rdi), %eax > > + movzbl (%rsi), %ecx > > + subl %ecx, %eax > > # endif > > -# endif > > +L(ret1): > > ret > > +# endif > > > > -L(return_2_vec_size): > > - tzcntl %ecx, %edx > > + .p2align 4,, 10 > > +L(return_vec_1): > > + tzcntl %ecx, %ecx > > +# ifdef USE_AS_STRNCMP > > + /* rdx must be > CHAR_PER_VEC so its safe to subtract without > > + worrying about underflow. */ > > + addq $-CHAR_PER_VEC, %rdx > > + cmpq %rcx, %rdx > > + jbe L(ret_zero) > > +# endif > > # ifdef USE_AS_WCSCMP > > - /* NB: Multiply wchar_t count by 4 to get the number of bytes. */ > > - sall $2, %edx > > + movl VEC_SIZE(%rdi, %rcx, SIZE_OF_CHAR), %edx > > + xorl %eax, %eax > > + cmpl VEC_SIZE(%rsi, %rcx, SIZE_OF_CHAR), %edx > > + je L(ret2) > > + setl %al > > + negl %eax > > + orl $1, %eax > > +# else > > + movzbl VEC_SIZE(%rdi, %rcx), %eax > > + movzbl VEC_SIZE(%rsi, %rcx), %ecx > > + subl %ecx, %eax > > # endif > > +L(ret2): > > + ret > > + > > + .p2align 4,, 10 > > # ifdef USE_AS_STRNCMP > > - /* Return 0 if the mismatched index (%rdx + 2 * VEC_SIZE) is > > - after the maximum offset (%r11). */ > > - addq $(VEC_SIZE * 2), %rdx > > - cmpq %r11, %rdx > > - jae L(zero) > > -# ifdef USE_AS_WCSCMP > > - xorl %eax, %eax > > - movl (%rdi, %rdx), %ecx > > - cmpl (%rsi, %rdx), %ecx > > - jne L(wcscmp_return) > > +L(return_vec_3): > > +# if CHAR_PER_VEC <= 16 > > + sall $CHAR_PER_VEC, %ecx > > # else > > - movzbl (%rdi, %rdx), %eax > > - movzbl (%rsi, %rdx), %edx > > - subl %edx, %eax > > + salq $CHAR_PER_VEC, %rcx > > # endif > > +# endif > > +L(return_vec_2): > > +# if (CHAR_PER_VEC <= 16) || !(defined USE_AS_STRNCMP) > > + tzcntl %ecx, %ecx > > # else > > -# ifdef USE_AS_WCSCMP > > - xorl %eax, %eax > > - movl (VEC_SIZE * 2)(%rdi, %rdx), %ecx > > - cmpl (VEC_SIZE * 2)(%rsi, %rdx), %ecx > > - jne L(wcscmp_return) > > -# else > > - movzbl (VEC_SIZE * 2)(%rdi, %rdx), %eax > > - movzbl (VEC_SIZE * 2)(%rsi, %rdx), %edx > > - subl %edx, %eax > > -# endif > > + tzcntq %rcx, %rcx > > # endif > > - ret > > > > -L(return_3_vec_size): > > - tzcntl %ecx, %edx > > -# ifdef USE_AS_WCSCMP > > - /* NB: Multiply wchar_t count by 4 to get the number of bytes. */ > > - sall $2, %edx > > -# endif > > # ifdef USE_AS_STRNCMP > > - /* Return 0 if the mismatched index (%rdx + 3 * VEC_SIZE) is > > - after the maximum offset (%r11). */ > > - addq $(VEC_SIZE * 3), %rdx > > - cmpq %r11, %rdx > > - jae L(zero) > > -# ifdef USE_AS_WCSCMP > > + cmpq %rcx, %rdx > > + jbe L(ret_zero) > > +# endif > > + > > +# ifdef USE_AS_WCSCMP > > + movl (VEC_SIZE * 2)(%rdi, %rcx, SIZE_OF_CHAR), %edx > > xorl %eax, %eax > > - movl (%rdi, %rdx), %ecx > > - cmpl (%rsi, %rdx), %ecx > > - jne L(wcscmp_return) > > -# else > > - movzbl (%rdi, %rdx), %eax > > - movzbl (%rsi, %rdx), %edx > > - subl %edx, %eax > > -# endif > > + cmpl (VEC_SIZE * 2)(%rsi, %rcx, SIZE_OF_CHAR), %edx > > + je L(ret3) > > + setl %al > > + negl %eax > > + orl $1, %eax > > # else > > + movzbl (VEC_SIZE * 2)(%rdi, %rcx), %eax > > + movzbl (VEC_SIZE * 2)(%rsi, %rcx), %ecx > > + subl %ecx, %eax > > +# endif > > +L(ret3): > > + ret > > + > > +# ifndef USE_AS_STRNCMP > > + .p2align 4,, 10 > > +L(return_vec_3): > > + tzcntl %ecx, %ecx > > # ifdef USE_AS_WCSCMP > > + movl (VEC_SIZE * 3)(%rdi, %rcx, SIZE_OF_CHAR), %edx > > xorl %eax, %eax > > - movl (VEC_SIZE * 3)(%rdi, %rdx), %ecx > > - cmpl (VEC_SIZE * 3)(%rsi, %rdx), %ecx > > - jne L(wcscmp_return) > > + cmpl (VEC_SIZE * 3)(%rsi, %rcx, SIZE_OF_CHAR), %edx > > + je L(ret4) > > + setl %al > > + negl %eax > > + orl $1, %eax > > # else > > - movzbl (VEC_SIZE * 3)(%rdi, %rdx), %eax > > - movzbl (VEC_SIZE * 3)(%rsi, %rdx), %edx > > - subl %edx, %eax > > + movzbl (VEC_SIZE * 3)(%rdi, %rcx), %eax > > + movzbl (VEC_SIZE * 3)(%rsi, %rcx), %ecx > > + subl %ecx, %eax > > # endif > > -# endif > > +L(ret4): > > ret > > +# endif > > > > - .p2align 4 > > -L(next_3_vectors): > > - VMOVU VEC_SIZE(%rdi), %YMM0 > > - /* Each bit set in K2 represents a non-null CHAR in YMM0. */ > > + /* 32 byte align here ensures the main loop is ideally aligned > > + for DSB. */ > > + .p2align 5 > > +L(more_3x_vec): > > + /* Safe to compare 4x vectors. */ > > + VMOVU (VEC_SIZE)(%rdi), %YMM0 > > VPTESTM %YMM0, %YMM0, %k2 > > - /* Each bit cleared in K1 represents a mismatch or a null CHAR > > - in YMM0 and 32 bytes at VEC_SIZE(%rsi). */ > > - VPCMP $0, VEC_SIZE(%rsi), %YMM0, %k1{%k2} > > + VPCMP $0, (VEC_SIZE)(%rsi), %YMM0, %k1{%k2} > > kmovd %k1, %ecx > > -# ifdef USE_AS_WCSCMP > > - subl $0xff, %ecx > > -# else > > - incl %ecx > > + TESTEQ %ecx > > + jnz L(return_vec_1) > > + > > +# ifdef USE_AS_STRNCMP > > + subq $(CHAR_PER_VEC * 2), %rdx > > + jbe L(ret_zero) > > # endif > > - jne L(return_vec_size) > > > > VMOVU (VEC_SIZE * 2)(%rdi), %YMM0 > > - /* Each bit set in K2 represents a non-null CHAR in YMM0. */ > > VPTESTM %YMM0, %YMM0, %k2 > > - /* Each bit cleared in K1 represents a mismatch or a null CHAR > > - in YMM0 and 32 bytes at (VEC_SIZE * 2)(%rsi). */ > > VPCMP $0, (VEC_SIZE * 2)(%rsi), %YMM0, %k1{%k2} > > kmovd %k1, %ecx > > -# ifdef USE_AS_WCSCMP > > - subl $0xff, %ecx > > -# else > > - incl %ecx > > -# endif > > - jne L(return_2_vec_size) > > + TESTEQ %ecx > > + jnz L(return_vec_2) > > > > VMOVU (VEC_SIZE * 3)(%rdi), %YMM0 > > - /* Each bit set in K2 represents a non-null CHAR in YMM0. */ > > VPTESTM %YMM0, %YMM0, %k2 > > - /* Each bit cleared in K1 represents a mismatch or a null CHAR > > - in YMM0 and 32 bytes at (VEC_SIZE * 2)(%rsi). */ > > VPCMP $0, (VEC_SIZE * 3)(%rsi), %YMM0, %k1{%k2} > > kmovd %k1, %ecx > > + TESTEQ %ecx > > + jnz L(return_vec_3) > > + > > +# ifdef USE_AS_STRNCMP > > + cmpq $(CHAR_PER_VEC * 2), %rdx > > + jbe L(ret_zero) > > +# endif > > + > > + > > # ifdef USE_AS_WCSCMP > > - subl $0xff, %ecx > > + /* any non-zero positive value that doesn't inference with 0x1. > > + */ > > + movl $2, %r8d > > + > > # else > > - incl %ecx > > + xorl %r8d, %r8d > > # endif > > - jne L(return_3_vec_size) > > -L(main_loop_header): > > - leaq (VEC_SIZE * 4)(%rdi), %rdx > > - movl $PAGE_SIZE, %ecx > > - /* Align load via RAX. */ > > - andq $-(VEC_SIZE * 4), %rdx > > - subq %rdi, %rdx > > - leaq (%rdi, %rdx), %rax > > + > > + /* The prepare labels are various entry points from the page > > + cross logic. */ > > +L(prepare_loop): > > + > > # ifdef USE_AS_STRNCMP > > - /* Starting from this point, the maximum offset, or simply the > > - 'offset', DECREASES by the same amount when base pointers are > > - moved forward. Return 0 when: > > - 1) On match: offset <= the matched vector index. > > - 2) On mistmach, offset is before the mistmatched index. > > - */ > > - subq %rdx, %r11 > > - jbe L(zero) > > +# ifdef USE_AS_WCSCMP > > +L(prepare_loop_no_len): > > + movl %edi, %ecx > > + andl $(VEC_SIZE * 4 - 1), %ecx > > + shrl $2, %ecx > > + leaq (CHAR_PER_VEC * 2)(%rdx, %rcx), %rdx > > +# else > > + /* Store N + (VEC_SIZE * 4) and place check at the begining of > > + the loop. */ > > + leaq (VEC_SIZE * 2)(%rdi, %rdx), %rdx > > +L(prepare_loop_no_len): > > +# endif > > +# else > > +L(prepare_loop_no_len): > > # endif > > - addq %rsi, %rdx > > - movq %rdx, %rsi > > - andl $(PAGE_SIZE - 1), %esi > > - /* Number of bytes before page crossing. */ > > - subq %rsi, %rcx > > - /* Number of VEC_SIZE * 4 blocks before page crossing. */ > > - shrq $DIVIDE_BY_VEC_4_SHIFT, %rcx > > - /* ESI: Number of VEC_SIZE * 4 blocks before page crossing. */ > > - movl %ecx, %esi > > - jmp L(loop_start) > > > > + /* Align s1 and adjust s2 accordingly. */ > > + subq %rdi, %rsi > > + andq $-(VEC_SIZE * 4), %rdi > > +L(prepare_loop_readj): > > + addq %rdi, %rsi > > +# if (defined USE_AS_STRNCMP) && !(defined USE_AS_WCSCMP) > > + subq %rdi, %rdx > > +# endif > > + > > +L(prepare_loop_aligned): > > + /* eax stores distance from rsi to next page cross. These cases > > + need to be handled specially as the 4x loop could potentially > > + read memory past the length of s1 or s2 and across a page > > + boundary. */ > > + movl $-(VEC_SIZE * 4), %eax > > + subl %esi, %eax > > + andl $(PAGE_SIZE - 1), %eax > > + > > + vpxorq %YMMZERO, %YMMZERO, %YMMZERO > > + > > + /* Loop 4x comparisons at a time. */ > > .p2align 4 > > L(loop): > > + > > + /* End condition for strncmp. */ > > # ifdef USE_AS_STRNCMP > > - /* Base pointers are moved forward by 4 * VEC_SIZE. Decrease > > - the maximum offset (%r11) by the same amount. */ > > - subq $(VEC_SIZE * 4), %r11 > > - jbe L(zero) > > + subq $(CHAR_PER_VEC * 4), %rdx > > + jbe L(ret_zero) > > # endif > > - addq $(VEC_SIZE * 4), %rax > > - addq $(VEC_SIZE * 4), %rdx > > -L(loop_start): > > - testl %esi, %esi > > - leal -1(%esi), %esi > > - je L(loop_cross_page) > > -L(back_to_loop): > > - /* Main loop, comparing 4 vectors are a time. */ > > - VMOVA (%rax), %YMM0 > > - VMOVA VEC_SIZE(%rax), %YMM2 > > - VMOVA (VEC_SIZE * 2)(%rax), %YMM4 > > - VMOVA (VEC_SIZE * 3)(%rax), %YMM6 > > + > > + subq $-(VEC_SIZE * 4), %rdi > > + subq $-(VEC_SIZE * 4), %rsi > > + > > + /* Check if rsi loads will cross a page boundary. */ > > + addl $-(VEC_SIZE * 4), %eax > > + jnb L(page_cross_during_loop) > > + > > + /* Loop entry after handling page cross during loop. */ > > +L(loop_skip_page_cross_check): > > + VMOVA (VEC_SIZE * 0)(%rdi), %YMM0 > > + VMOVA (VEC_SIZE * 1)(%rdi), %YMM2 > > + VMOVA (VEC_SIZE * 2)(%rdi), %YMM4 > > + VMOVA (VEC_SIZE * 3)(%rdi), %YMM6 > > > > VPMINU %YMM0, %YMM2, %YMM8 > > VPMINU %YMM4, %YMM6, %YMM9 > > > > - /* A zero CHAR in YMM8 means that there is a null CHAR. */ > > - VPMINU %YMM8, %YMM9, %YMM8 > > + /* A zero CHAR in YMM9 means that there is a null CHAR. */ > > + VPMINU %YMM8, %YMM9, %YMM9 > > > > /* Each bit set in K1 represents a non-null CHAR in YMM8. */ > > - VPTESTM %YMM8, %YMM8, %k1 > > + VPTESTM %YMM9, %YMM9, %k1 > > > > - /* (YMM ^ YMM): A non-zero CHAR represents a mismatch. */ > > - vpxorq (%rdx), %YMM0, %YMM1 > > - vpxorq VEC_SIZE(%rdx), %YMM2, %YMM3 > > - vpxorq (VEC_SIZE * 2)(%rdx), %YMM4, %YMM5 > > - vpxorq (VEC_SIZE * 3)(%rdx), %YMM6, %YMM7 > > + vpxorq (VEC_SIZE * 0)(%rsi), %YMM0, %YMM1 > > + vpxorq (VEC_SIZE * 1)(%rsi), %YMM2, %YMM3 > > + vpxorq (VEC_SIZE * 2)(%rsi), %YMM4, %YMM5 > > + /* Ternary logic to xor (VEC_SIZE * 3)(%rsi) with YMM6 while > > + oring with YMM1. Result is stored in YMM6. */ > > + vpternlogd $0xde, (VEC_SIZE * 3)(%rsi), %YMM1, %YMM6 > > > > - vporq %YMM1, %YMM3, %YMM9 > > - vporq %YMM5, %YMM7, %YMM10 > > + /* Or together YMM3, YMM5, and YMM6. */ > > + vpternlogd $0xfe, %YMM3, %YMM5, %YMM6 > > > > - /* A non-zero CHAR in YMM9 represents a mismatch. */ > > - vporq %YMM9, %YMM10, %YMM9 > > > > - /* Each bit cleared in K0 represents a mismatch or a null CHAR. */ > > - VPCMP $0, %YMMZERO, %YMM9, %k0{%k1} > > - kmovd %k0, %ecx > > -# ifdef USE_AS_WCSCMP > > - subl $0xff, %ecx > > -# else > > - incl %ecx > > -# endif > > - je L(loop) > > + /* A non-zero CHAR in YMM6 represents a mismatch. */ > > + VPCMP $0, %YMMZERO, %YMM6, %k0{%k1} > > + kmovd %k0, %LOOP_REG > > > > - /* Each bit set in K1 represents a non-null CHAR in YMM0. */ > > + TESTEQ %LOOP_REG > > + jz L(loop) > > + > > + > > + /* Find which VEC has the mismatch of end of string. */ > > VPTESTM %YMM0, %YMM0, %k1 > > - /* Each bit cleared in K0 represents a mismatch or a null CHAR > > - in YMM0 and (%rdx). */ > > VPCMP $0, %YMMZERO, %YMM1, %k0{%k1} > > kmovd %k0, %ecx > > -# ifdef USE_AS_WCSCMP > > - subl $0xff, %ecx > > -# else > > - incl %ecx > > -# endif > > - je L(test_vec) > > - tzcntl %ecx, %ecx > > -# ifdef USE_AS_WCSCMP > > - /* NB: Multiply wchar_t count by 4 to get the number of bytes. */ > > - sall $2, %ecx > > -# endif > > -# ifdef USE_AS_STRNCMP > > - cmpq %rcx, %r11 > > - jbe L(zero) > > -# ifdef USE_AS_WCSCMP > > - movq %rax, %rsi > > - xorl %eax, %eax > > - movl (%rsi, %rcx), %edi > > - cmpl (%rdx, %rcx), %edi > > - jne L(wcscmp_return) > > -# else > > - movzbl (%rax, %rcx), %eax > > - movzbl (%rdx, %rcx), %edx > > - subl %edx, %eax > > -# endif > > -# else > > -# ifdef USE_AS_WCSCMP > > - movq %rax, %rsi > > - xorl %eax, %eax > > - movl (%rsi, %rcx), %edi > > - cmpl (%rdx, %rcx), %edi > > - jne L(wcscmp_return) > > -# else > > - movzbl (%rax, %rcx), %eax > > - movzbl (%rdx, %rcx), %edx > > - subl %edx, %eax > > -# endif > > -# endif > > - ret > > + TESTEQ %ecx > > + jnz L(return_vec_0_end) > > > > - .p2align 4 > > -L(test_vec): > > -# ifdef USE_AS_STRNCMP > > - /* The first vector matched. Return 0 if the maximum offset > > - (%r11) <= VEC_SIZE. */ > > - cmpq $VEC_SIZE, %r11 > > - jbe L(zero) > > -# endif > > - /* Each bit set in K1 represents a non-null CHAR in YMM2. */ > > VPTESTM %YMM2, %YMM2, %k1 > > - /* Each bit cleared in K0 represents a mismatch or a null CHAR > > - in YMM2 and VEC_SIZE(%rdx). */ > > VPCMP $0, %YMMZERO, %YMM3, %k0{%k1} > > kmovd %k0, %ecx > > -# ifdef USE_AS_WCSCMP > > - subl $0xff, %ecx > > -# else > > - incl %ecx > > -# endif > > - je L(test_2_vec) > > - tzcntl %ecx, %edi > > -# ifdef USE_AS_WCSCMP > > - /* NB: Multiply wchar_t count by 4 to get the number of bytes. */ > > - sall $2, %edi > > -# endif > > -# ifdef USE_AS_STRNCMP > > - addq $VEC_SIZE, %rdi > > - cmpq %rdi, %r11 > > - jbe L(zero) > > -# ifdef USE_AS_WCSCMP > > - movq %rax, %rsi > > - xorl %eax, %eax > > - movl (%rsi, %rdi), %ecx > > - cmpl (%rdx, %rdi), %ecx > > - jne L(wcscmp_return) > > -# else > > - movzbl (%rax, %rdi), %eax > > - movzbl (%rdx, %rdi), %edx > > - subl %edx, %eax > > -# endif > > -# else > > -# ifdef USE_AS_WCSCMP > > - movq %rax, %rsi > > - xorl %eax, %eax > > - movl VEC_SIZE(%rsi, %rdi), %ecx > > - cmpl VEC_SIZE(%rdx, %rdi), %ecx > > - jne L(wcscmp_return) > > -# else > > - movzbl VEC_SIZE(%rax, %rdi), %eax > > - movzbl VEC_SIZE(%rdx, %rdi), %edx > > - subl %edx, %eax > > -# endif > > -# endif > > - ret > > + TESTEQ %ecx > > + jnz L(return_vec_1_end) > > > > - .p2align 4 > > -L(test_2_vec): > > + > > + /* Handle VEC 2 and 3 without branches. */ > > +L(return_vec_2_3_end): > > # ifdef USE_AS_STRNCMP > > - /* The first 2 vectors matched. Return 0 if the maximum offset > > - (%r11) <= 2 * VEC_SIZE. */ > > - cmpq $(VEC_SIZE * 2), %r11 > > - jbe L(zero) > > + subq $(CHAR_PER_VEC * 2), %rdx > > + jbe L(ret_zero_end) > > # endif > > - /* Each bit set in K1 represents a non-null CHAR in YMM4. */ > > + > > VPTESTM %YMM4, %YMM4, %k1 > > - /* Each bit cleared in K0 represents a mismatch or a null CHAR > > - in YMM4 and (VEC_SIZE * 2)(%rdx). */ > > VPCMP $0, %YMMZERO, %YMM5, %k0{%k1} > > kmovd %k0, %ecx > > -# ifdef USE_AS_WCSCMP > > - subl $0xff, %ecx > > + TESTEQ %ecx > > +# if CHAR_PER_VEC <= 16 > > + sall $CHAR_PER_VEC, %LOOP_REG > > + orl %ecx, %LOOP_REG > > # else > > - incl %ecx > > + salq $CHAR_PER_VEC, %LOOP_REG64 > > + orq %rcx, %LOOP_REG64 > > +# endif > > +L(return_vec_3_end): > > + /* LOOP_REG contains matches for null/mismatch from the loop. If > > + VEC 0,1,and 2 all have no null and no mismatches then mismatch > > + must entirely be from VEC 3 which is fully represented by > > + LOOP_REG. */ > > +# if CHAR_PER_VEC <= 16 > > + tzcntl %LOOP_REG, %LOOP_REG > > +# else > > + tzcntq %LOOP_REG64, %LOOP_REG64 > > +# endif > > +# ifdef USE_AS_STRNCMP > > + cmpq %LOOP_REG64, %rdx > > + jbe L(ret_zero_end) > > # endif > > - je L(test_3_vec) > > - tzcntl %ecx, %edi > > + > > # ifdef USE_AS_WCSCMP > > - /* NB: Multiply wchar_t count by 4 to get the number of bytes. */ > > - sall $2, %edi > > + movl (VEC_SIZE * 2)(%rdi, %LOOP_REG64, SIZE_OF_CHAR), %ecx > > + xorl %eax, %eax > > + cmpl (VEC_SIZE * 2)(%rsi, %LOOP_REG64, SIZE_OF_CHAR), %ecx > > + je L(ret5) > > + setl %al > > + negl %eax > > + xorl %r8d, %eax > > +# else > > + movzbl (VEC_SIZE * 2)(%rdi, %LOOP_REG64), %eax > > + movzbl (VEC_SIZE * 2)(%rsi, %LOOP_REG64), %ecx > > + subl %ecx, %eax > > + xorl %r8d, %eax > > + subl %r8d, %eax > > # endif > > +L(ret5): > > + ret > > + > > # ifdef USE_AS_STRNCMP > > - addq $(VEC_SIZE * 2), %rdi > > - cmpq %rdi, %r11 > > - jbe L(zero) > > -# ifdef USE_AS_WCSCMP > > - movq %rax, %rsi > > + .p2align 4,, 2 > > +L(ret_zero_end): > > xorl %eax, %eax > > - movl (%rsi, %rdi), %ecx > > - cmpl (%rdx, %rdi), %ecx > > - jne L(wcscmp_return) > > + ret > > +# endif > > + > > + > > + /* The L(return_vec_N_end) differ from L(return_vec_N) in that > > + they use the value of `r8` to negate the return value. This is > > + because the page cross logic can swap `rdi` and `rsi`. */ > > + .p2align 4,, 10 > > +# ifdef USE_AS_STRNCMP > > +L(return_vec_1_end): > > +# if CHAR_PER_VEC <= 16 > > + sall $CHAR_PER_VEC, %ecx > > # else > > - movzbl (%rax, %rdi), %eax > > - movzbl (%rdx, %rdi), %edx > > - subl %edx, %eax > > + salq $CHAR_PER_VEC, %rcx > > # endif > > +# endif > > +L(return_vec_0_end): > > +# if (CHAR_PER_VEC <= 16) || !(defined USE_AS_STRNCMP) > > + tzcntl %ecx, %ecx > > # else > > -# ifdef USE_AS_WCSCMP > > - movq %rax, %rsi > > - xorl %eax, %eax > > - movl (VEC_SIZE * 2)(%rsi, %rdi), %ecx > > - cmpl (VEC_SIZE * 2)(%rdx, %rdi), %ecx > > - jne L(wcscmp_return) > > -# else > > - movzbl (VEC_SIZE * 2)(%rax, %rdi), %eax > > - movzbl (VEC_SIZE * 2)(%rdx, %rdi), %edx > > - subl %edx, %eax > > -# endif > > + tzcntq %rcx, %rcx > > # endif > > - ret > > > > - .p2align 4 > > -L(test_3_vec): > > # ifdef USE_AS_STRNCMP > > - /* The first 3 vectors matched. Return 0 if the maximum offset > > - (%r11) <= 3 * VEC_SIZE. */ > > - cmpq $(VEC_SIZE * 3), %r11 > > - jbe L(zero) > > + cmpq %rcx, %rdx > > + jbe L(ret_zero_end) > > # endif > > - /* Each bit set in K1 represents a non-null CHAR in YMM6. */ > > - VPTESTM %YMM6, %YMM6, %k1 > > - /* Each bit cleared in K0 represents a mismatch or a null CHAR > > - in YMM6 and (VEC_SIZE * 3)(%rdx). */ > > - VPCMP $0, %YMMZERO, %YMM7, %k0{%k1} > > - kmovd %k0, %ecx > > + > > # ifdef USE_AS_WCSCMP > > - subl $0xff, %ecx > > + movl (%rdi, %rcx, SIZE_OF_CHAR), %edx > > + xorl %eax, %eax > > + cmpl (%rsi, %rcx, SIZE_OF_CHAR), %edx > > + je L(ret6) > > + setl %al > > + negl %eax > > + /* This is the non-zero case for `eax` so just xorl with `r8d` > > + flip is `rdi` and `rsi` where swapped. */ > > + xorl %r8d, %eax > > # else > > - incl %ecx > > + movzbl (%rdi, %rcx), %eax > > + movzbl (%rsi, %rcx), %ecx > > + subl %ecx, %eax > > + /* Flip `eax` if `rdi` and `rsi` where swapped in page cross > > + logic. Subtract `r8d` after xor for zero case. */ > > + xorl %r8d, %eax > > + subl %r8d, %eax > > # endif > > +L(ret6): > > + ret > > + > > +# ifndef USE_AS_STRNCMP > > + .p2align 4,, 10 > > +L(return_vec_1_end): > > tzcntl %ecx, %ecx > > -# ifdef USE_AS_WCSCMP > > - /* NB: Multiply wchar_t count by 4 to get the number of bytes. */ > > - sall $2, %ecx > > -# endif > > -# ifdef USE_AS_STRNCMP > > - addq $(VEC_SIZE * 3), %rcx > > - cmpq %rcx, %r11 > > - jbe L(zero) > > # ifdef USE_AS_WCSCMP > > - movq %rax, %rsi > > + movl VEC_SIZE(%rdi, %rcx, SIZE_OF_CHAR), %edx > > xorl %eax, %eax > > - movl (%rsi, %rcx), %esi > > - cmpl (%rdx, %rcx), %esi > > - jne L(wcscmp_return) > > -# else > > - movzbl (%rax, %rcx), %eax > > - movzbl (%rdx, %rcx), %edx > > - subl %edx, %eax > > -# endif > > -# else > > -# ifdef USE_AS_WCSCMP > > - movq %rax, %rsi > > - xorl %eax, %eax > > - movl (VEC_SIZE * 3)(%rsi, %rcx), %esi > > - cmpl (VEC_SIZE * 3)(%rdx, %rcx), %esi > > - jne L(wcscmp_return) > > + cmpl VEC_SIZE(%rsi, %rcx, SIZE_OF_CHAR), %edx > > + je L(ret7) > > + setl %al > > + negl %eax > > + xorl %r8d, %eax > > # else > > - movzbl (VEC_SIZE * 3)(%rax, %rcx), %eax > > - movzbl (VEC_SIZE * 3)(%rdx, %rcx), %edx > > - subl %edx, %eax > > + movzbl VEC_SIZE(%rdi, %rcx), %eax > > + movzbl VEC_SIZE(%rsi, %rcx), %ecx > > + subl %ecx, %eax > > + xorl %r8d, %eax > > + subl %r8d, %eax > > # endif > > -# endif > > +L(ret7): > > ret > > - > > - .p2align 4 > > -L(loop_cross_page): > > - xorl %r10d, %r10d > > - movq %rdx, %rcx > > - /* Align load via RDX. We load the extra ECX bytes which should > > - be ignored. */ > > - andl $((VEC_SIZE * 4) - 1), %ecx > > - /* R10 is -RCX. */ > > - subq %rcx, %r10 > > - > > - /* This works only if VEC_SIZE * 2 == 64. */ > > -# if (VEC_SIZE * 2) != 64 > > -# error (VEC_SIZE * 2) != 64 > > # endif > > > > - /* Check if the first VEC_SIZE * 2 bytes should be ignored. */ > > - cmpl $(VEC_SIZE * 2), %ecx > > - jge L(loop_cross_page_2_vec) > > > > - VMOVU (%rax, %r10), %YMM2 > > - VMOVU VEC_SIZE(%rax, %r10), %YMM3 > > + /* Page cross in rsi in next 4x VEC. */ > > > > - /* Each bit set in K2 represents a non-null CHAR in YMM2. */ > > - VPTESTM %YMM2, %YMM2, %k2 > > - /* Each bit cleared in K1 represents a mismatch or a null CHAR > > - in YMM2 and 32 bytes at (%rdx, %r10). */ > > - VPCMP $0, (%rdx, %r10), %YMM2, %k1{%k2} > > - kmovd %k1, %r9d > > - /* Don't use subl since it is the lower 16/32 bits of RDI > > - below. */ > > - notl %r9d > > -# ifdef USE_AS_WCSCMP > > - /* Only last 8 bits are valid. */ > > - andl $0xff, %r9d > > -# endif > > + /* TODO: Improve logic here. */ > > + .p2align 4,, 10 > > +L(page_cross_during_loop): > > + /* eax contains [distance_from_page - (VEC_SIZE * 4)]. */ > > > > - /* Each bit set in K4 represents a non-null CHAR in YMM3. */ > > - VPTESTM %YMM3, %YMM3, %k4 > > - /* Each bit cleared in K3 represents a mismatch or a null CHAR > > - in YMM3 and 32 bytes at VEC_SIZE(%rdx, %r10). */ > > - VPCMP $0, VEC_SIZE(%rdx, %r10), %YMM3, %k3{%k4} > > - kmovd %k3, %edi > > - /* Must use notl %edi here as lower bits are for CHAR > > - comparisons potentially out of range thus can be 0 without > > - indicating mismatch. */ > > - notl %edi > > -# ifdef USE_AS_WCSCMP > > - /* Don't use subl since it is the upper 8 bits of EDI below. */ > > - andl $0xff, %edi > > -# endif > > + /* Optimistically rsi and rdi and both aligned in which case we > > + don't need any logic here. */ > > + cmpl $-(VEC_SIZE * 4), %eax > > + /* Don't adjust eax before jumping back to loop and we will > > + never hit page cross case again. */ > > + je L(loop_skip_page_cross_check) > > > > -# ifdef USE_AS_WCSCMP > > - /* NB: Each bit in EDI/R9D represents 4-byte element. */ > > - sall $8, %edi > > - /* NB: Divide shift count by 4 since each bit in K1 represent 4 > > - bytes. */ > > - movl %ecx, %SHIFT_REG32 > > - sarl $2, %SHIFT_REG32 > > - > > - /* Each bit in EDI represents a null CHAR or a mismatch. */ > > - orl %r9d, %edi > > -# else > > - salq $32, %rdi > > + /* Check if we can safely load a VEC. */ > > + cmpl $-(VEC_SIZE * 3), %eax > > + jle L(less_1x_vec_till_page_cross) > > > > - /* Each bit in RDI represents a null CHAR or a mismatch. */ > > - orq %r9, %rdi > > -# endif > > + VMOVA (%rdi), %YMM0 > > + VPTESTM %YMM0, %YMM0, %k2 > > + VPCMP $0, (%rsi), %YMM0, %k1{%k2} > > + kmovd %k1, %ecx > > + TESTEQ %ecx > > + jnz L(return_vec_0_end) > > + > > + /* if distance >= 2x VEC then eax > -(VEC_SIZE * 2). */ > > + cmpl $-(VEC_SIZE * 2), %eax > > + jg L(more_2x_vec_till_page_cross) > > + > > + .p2align 4,, 4 > > +L(less_1x_vec_till_page_cross): > > + subl $-(VEC_SIZE * 4), %eax > > + /* Guranteed safe to read from rdi - VEC_SIZE here. The only > > + concerning case is first iteration if incoming s1 was near start > > + of a page and s2 near end. If s1 was near the start of the page > > + we already aligned up to nearest VEC_SIZE * 4 so gurnateed safe > > + to read back -VEC_SIZE. If rdi is truly at the start of a page > > + here, it means the previous page (rdi - VEC_SIZE) has already > > + been loaded earlier so must be valid. */ > > + VMOVU -VEC_SIZE(%rdi, %rax), %YMM0 > > + VPTESTM %YMM0, %YMM0, %k2 > > + VPCMP $0, -VEC_SIZE(%rsi, %rax), %YMM0, %k1{%k2} > > + > > + /* Mask of potentially valid bits. The lower bits can be out of > > + range comparisons (but safe regarding page crosses). */ > > > > - /* Since ECX < VEC_SIZE * 2, simply skip the first ECX bytes. */ > > - shrxq %SHIFT_REG64, %rdi, %rdi > > - testq %rdi, %rdi > > - je L(loop_cross_page_2_vec) > > - tzcntq %rdi, %rcx > > # ifdef USE_AS_WCSCMP > > - /* NB: Multiply wchar_t count by 4 to get the number of bytes. */ > > - sall $2, %ecx > > + movl $-1, %r10d > > + movl %esi, %ecx > > + andl $(VEC_SIZE - 1), %ecx > > + shrl $2, %ecx > > + shlxl %ecx, %r10d, %ecx > > + movzbl %cl, %r10d > > +# else > > + movl $-1, %ecx > > + shlxl %esi, %ecx, %r10d > > # endif > > + > > + kmovd %k1, %ecx > > + notl %ecx > > + > > + > > # ifdef USE_AS_STRNCMP > > - cmpq %rcx, %r11 > > - jbe L(zero) > > # ifdef USE_AS_WCSCMP > > - movq %rax, %rsi > > - xorl %eax, %eax > > - movl (%rsi, %rcx), %edi > > - cmpl (%rdx, %rcx), %edi > > - jne L(wcscmp_return) > > + movl %eax, %r11d > > + shrl $2, %r11d > > + cmpq %r11, %rdx > > # else > > - movzbl (%rax, %rcx), %eax > > - movzbl (%rdx, %rcx), %edx > > - subl %edx, %eax > > + cmpq %rax, %rdx > > # endif > > + jbe L(return_page_cross_end_check) > > +# endif > > + movl %eax, %OFFSET_REG > > + > > + /* Readjust eax before potentially returning to the loop. */ > > + addl $(PAGE_SIZE - VEC_SIZE * 4), %eax > > + > > + andl %r10d, %ecx > > + jz L(loop_skip_page_cross_check) > > + > > + .p2align 4,, 3 > > +L(return_page_cross_end): > > + tzcntl %ecx, %ecx > > + > > +# if (defined USE_AS_STRNCMP) || (defined USE_AS_WCSCMP) > > + leal -VEC_SIZE(%OFFSET_REG64, %rcx, SIZE_OF_CHAR), %ecx > > +L(return_page_cross_cmp_mem): > > # else > > -# ifdef USE_AS_WCSCMP > > - movq %rax, %rsi > > + addl %OFFSET_REG, %ecx > > +# endif > > +# ifdef USE_AS_WCSCMP > > + movl VEC_OFFSET(%rdi, %rcx), %edx > > xorl %eax, %eax > > - movl (%rsi, %rcx), %edi > > - cmpl (%rdx, %rcx), %edi > > - jne L(wcscmp_return) > > -# else > > - movzbl (%rax, %rcx), %eax > > - movzbl (%rdx, %rcx), %edx > > - subl %edx, %eax > > -# endif > > + cmpl VEC_OFFSET(%rsi, %rcx), %edx > > + je L(ret8) > > + setl %al > > + negl %eax > > + xorl %r8d, %eax > > +# else > > + movzbl VEC_OFFSET(%rdi, %rcx), %eax > > + movzbl VEC_OFFSET(%rsi, %rcx), %ecx > > + subl %ecx, %eax > > + xorl %r8d, %eax > > + subl %r8d, %eax > > # endif > > +L(ret8): > > ret > > > > - .p2align 4 > > -L(loop_cross_page_2_vec): > > - /* The first VEC_SIZE * 2 bytes match or are ignored. */ > > - VMOVU (VEC_SIZE * 2)(%rax, %r10), %YMM0 > > - VMOVU (VEC_SIZE * 3)(%rax, %r10), %YMM1 > > +# ifdef USE_AS_STRNCMP > > + .p2align 4,, 10 > > +L(return_page_cross_end_check): > > + tzcntl %ecx, %ecx > > + leal -VEC_SIZE(%rax, %rcx, SIZE_OF_CHAR), %ecx > > +# ifdef USE_AS_WCSCMP > > + sall $2, %edx > > +# endif > > + cmpl %ecx, %edx > > + ja L(return_page_cross_cmp_mem) > > + xorl %eax, %eax > > + ret > > +# endif > > + > > > > + .p2align 4,, 10 > > +L(more_2x_vec_till_page_cross): > > + /* If more 2x vec till cross we will complete a full loop > > + iteration here. */ > > + > > + VMOVA VEC_SIZE(%rdi), %YMM0 > > VPTESTM %YMM0, %YMM0, %k2 > > - /* Each bit cleared in K1 represents a mismatch or a null CHAR > > - in YMM0 and 32 bytes at (VEC_SIZE * 2)(%rdx, %r10). */ > > - VPCMP $0, (VEC_SIZE * 2)(%rdx, %r10), %YMM0, %k1{%k2} > > - kmovd %k1, %r9d > > - /* Don't use subl since it is the lower 16/32 bits of RDI > > - below. */ > > - notl %r9d > > -# ifdef USE_AS_WCSCMP > > - /* Only last 8 bits are valid. */ > > - andl $0xff, %r9d > > -# endif > > + VPCMP $0, VEC_SIZE(%rsi), %YMM0, %k1{%k2} > > + kmovd %k1, %ecx > > + TESTEQ %ecx > > + jnz L(return_vec_1_end) > > > > - VPTESTM %YMM1, %YMM1, %k4 > > - /* Each bit cleared in K3 represents a mismatch or a null CHAR > > - in YMM1 and 32 bytes at (VEC_SIZE * 3)(%rdx, %r10). */ > > - VPCMP $0, (VEC_SIZE * 3)(%rdx, %r10), %YMM1, %k3{%k4} > > - kmovd %k3, %edi > > - /* Must use notl %edi here as lower bits are for CHAR > > - comparisons potentially out of range thus can be 0 without > > - indicating mismatch. */ > > - notl %edi > > -# ifdef USE_AS_WCSCMP > > - /* Don't use subl since it is the upper 8 bits of EDI below. */ > > - andl $0xff, %edi > > +# ifdef USE_AS_STRNCMP > > + cmpq $(CHAR_PER_VEC * 2), %rdx > > + jbe L(ret_zero_in_loop_page_cross) > > # endif > > > > -# ifdef USE_AS_WCSCMP > > - /* NB: Each bit in EDI/R9D represents 4-byte element. */ > > - sall $8, %edi > > + subl $-(VEC_SIZE * 4), %eax > > > > - /* Each bit in EDI represents a null CHAR or a mismatch. */ > > - orl %r9d, %edi > > -# else > > - salq $32, %rdi > > + /* Safe to include comparisons from lower bytes. */ > > + VMOVU -(VEC_SIZE * 2)(%rdi, %rax), %YMM0 > > + VPTESTM %YMM0, %YMM0, %k2 > > + VPCMP $0, -(VEC_SIZE * 2)(%rsi, %rax), %YMM0, %k1{%k2} > > + kmovd %k1, %ecx > > + TESTEQ %ecx > > + jnz L(return_vec_page_cross_0) > > + > > + VMOVU -(VEC_SIZE * 1)(%rdi, %rax), %YMM0 > > + VPTESTM %YMM0, %YMM0, %k2 > > + VPCMP $0, -(VEC_SIZE * 1)(%rsi, %rax), %YMM0, %k1{%k2} > > + kmovd %k1, %ecx > > + TESTEQ %ecx > > + jnz L(return_vec_page_cross_1) > > > > - /* Each bit in RDI represents a null CHAR or a mismatch. */ > > - orq %r9, %rdi > > +# ifdef USE_AS_STRNCMP > > + /* Must check length here as length might proclude reading next > > + page. */ > > +# ifdef USE_AS_WCSCMP > > + movl %eax, %r11d > > + shrl $2, %r11d > > + cmpq %r11, %rdx > > +# else > > + cmpq %rax, %rdx > > +# endif > > + jbe L(ret_zero_in_loop_page_cross) > > # endif > > > > - xorl %r8d, %r8d > > - /* If ECX > VEC_SIZE * 2, skip ECX - (VEC_SIZE * 2) bytes. */ > > - subl $(VEC_SIZE * 2), %ecx > > - jle 1f > > - /* R8 has number of bytes skipped. */ > > - movl %ecx, %r8d > > -# ifdef USE_AS_WCSCMP > > - /* NB: Divide shift count by 4 since each bit in RDI represent 4 > > - bytes. */ > > - sarl $2, %ecx > > - /* Skip ECX bytes. */ > > - shrl %cl, %edi > > + /* Finish the loop. */ > > + VMOVA (VEC_SIZE * 2)(%rdi), %YMM4 > > + VMOVA (VEC_SIZE * 3)(%rdi), %YMM6 > > + VPMINU %YMM4, %YMM6, %YMM9 > > + VPTESTM %YMM9, %YMM9, %k1 > > + > > + vpxorq (VEC_SIZE * 2)(%rsi), %YMM4, %YMM5 > > + /* YMM6 = YMM5 | ((VEC_SIZE * 3)(%rsi) ^ YMM6). */ > > + vpternlogd $0xde, (VEC_SIZE * 3)(%rsi), %YMM5, %YMM6 > > + > > + VPCMP $0, %YMMZERO, %YMM6, %k0{%k1} > > + kmovd %k0, %LOOP_REG > > + TESTEQ %LOOP_REG > > + jnz L(return_vec_2_3_end) > > + > > + /* Best for code size to include ucond-jmp here. Would be faster > > + if this case is hot to duplicate the L(return_vec_2_3_end) code > > + as fall-through and have jump back to loop on mismatch > > + comparison. */ > > + subq $-(VEC_SIZE * 4), %rdi > > + subq $-(VEC_SIZE * 4), %rsi > > + addl $(PAGE_SIZE - VEC_SIZE * 8), %eax > > +# ifdef USE_AS_STRNCMP > > + subq $(CHAR_PER_VEC * 4), %rdx > > + ja L(loop_skip_page_cross_check) > > +L(ret_zero_in_loop_page_cross): > > + xorl %eax, %eax > > + ret > > # else > > - /* Skip ECX bytes. */ > > - shrq %cl, %rdi > > + jmp L(loop_skip_page_cross_check) > > # endif > > -1: > > - /* Before jumping back to the loop, set ESI to the number of > > - VEC_SIZE * 4 blocks before page crossing. */ > > - movl $(PAGE_SIZE / (VEC_SIZE * 4) - 1), %esi > > > > - testq %rdi, %rdi > > -# ifdef USE_AS_STRNCMP > > - /* At this point, if %rdi value is 0, it already tested > > - VEC_SIZE*4+%r10 byte starting from %rax. This label > > - checks whether strncmp maximum offset reached or not. */ > > - je L(string_nbyte_offset_check) > > + > > + .p2align 4,, 10 > > +L(return_vec_page_cross_0): > > + addl $-VEC_SIZE, %eax > > +L(return_vec_page_cross_1): > > + tzcntl %ecx, %ecx > > +# if defined USE_AS_STRNCMP || defined USE_AS_WCSCMP > > + leal -VEC_SIZE(%rax, %rcx, SIZE_OF_CHAR), %ecx > > +# ifdef USE_AS_STRNCMP > > +# ifdef USE_AS_WCSCMP > > + /* Must divide ecx instead of multiply rdx due to overflow. */ > > + movl %ecx, %eax > > + shrl $2, %eax > > + cmpq %rax, %rdx > > +# else > > + cmpq %rcx, %rdx > > +# endif > > + jbe L(ret_zero_in_loop_page_cross) > > +# endif > > # else > > - je L(back_to_loop) > > + addl %eax, %ecx > > # endif > > - tzcntq %rdi, %rcx > > + > > # ifdef USE_AS_WCSCMP > > - /* NB: Multiply wchar_t count by 4 to get the number of bytes. */ > > - sall $2, %ecx > > -# endif > > - addq %r10, %rcx > > - /* Adjust for number of bytes skipped. */ > > - addq %r8, %rcx > > -# ifdef USE_AS_STRNCMP > > - addq $(VEC_SIZE * 2), %rcx > > - subq %rcx, %r11 > > - jbe L(zero) > > -# ifdef USE_AS_WCSCMP > > - movq %rax, %rsi > > + movl VEC_OFFSET(%rdi, %rcx), %edx > > xorl %eax, %eax > > - movl (%rsi, %rcx), %edi > > - cmpl (%rdx, %rcx), %edi > > - jne L(wcscmp_return) > > -# else > > - movzbl (%rax, %rcx), %eax > > - movzbl (%rdx, %rcx), %edx > > - subl %edx, %eax > > -# endif > > + cmpl VEC_OFFSET(%rsi, %rcx), %edx > > + je L(ret9) > > + setl %al > > + negl %eax > > + xorl %r8d, %eax > > # else > > -# ifdef USE_AS_WCSCMP > > - movq %rax, %rsi > > - xorl %eax, %eax > > - movl (VEC_SIZE * 2)(%rsi, %rcx), %edi > > - cmpl (VEC_SIZE * 2)(%rdx, %rcx), %edi > > - jne L(wcscmp_return) > > -# else > > - movzbl (VEC_SIZE * 2)(%rax, %rcx), %eax > > - movzbl (VEC_SIZE * 2)(%rdx, %rcx), %edx > > - subl %edx, %eax > > -# endif > > + movzbl VEC_OFFSET(%rdi, %rcx), %eax > > + movzbl VEC_OFFSET(%rsi, %rcx), %ecx > > + subl %ecx, %eax > > + xorl %r8d, %eax > > + subl %r8d, %eax > > # endif > > +L(ret9): > > ret > > > > -# ifdef USE_AS_STRNCMP > > -L(string_nbyte_offset_check): > > - leaq (VEC_SIZE * 4)(%r10), %r10 > > - cmpq %r10, %r11 > > - jbe L(zero) > > - jmp L(back_to_loop) > > + > > + .p2align 4,, 10 > > +L(page_cross): > > +# ifndef USE_AS_STRNCMP > > + /* If both are VEC aligned we don't need any special logic here. > > + Only valid for strcmp where stop condition is guranteed to be > > + reachable by just reading memory. */ > > + testl $((VEC_SIZE - 1) << 20), %eax > > + jz L(no_page_cross) > > # endif > > > > - .p2align 4 > > -L(cross_page_loop): > > - /* Check one byte/dword at a time. */ > > + movl %edi, %eax > > + movl %esi, %ecx > > + andl $(PAGE_SIZE - 1), %eax > > + andl $(PAGE_SIZE - 1), %ecx > > + > > + xorl %OFFSET_REG, %OFFSET_REG > > + > > + /* Check which is closer to page cross, s1 or s2. */ > > + cmpl %eax, %ecx > > + jg L(page_cross_s2) > > + > > + /* The previous page cross check has false positives. Check for > > + true positive as page cross logic is very expensive. */ > > + subl $(PAGE_SIZE - VEC_SIZE * 4), %eax > > + jbe L(no_page_cross) > > + > > + > > + /* Set r8 to not interfere with normal return value (rdi and rsi > > + did not swap). */ > > # ifdef USE_AS_WCSCMP > > - cmpl %ecx, %eax > > + /* any non-zero positive value that doesn't inference with 0x1. > > + */ > > + movl $2, %r8d > > # else > > - subl %ecx, %eax > > + xorl %r8d, %r8d > > # endif > > - jne L(different) > > - addl $SIZE_OF_CHAR, %edx > > - cmpl $(VEC_SIZE * 4), %edx > > - je L(main_loop_header) > > + > > + /* Check if less than 1x VEC till page cross. */ > > + subl $(VEC_SIZE * 3), %eax > > + jg L(less_1x_vec_till_page) > > + > > + > > + /* If more than 1x VEC till page cross, loop throuh safely > > + loadable memory until within 1x VEC of page cross. */ > > + .p2align 4,, 8 > > +L(page_cross_loop): > > + VMOVU (%rdi, %OFFSET_REG64, SIZE_OF_CHAR), %YMM0 > > + VPTESTM %YMM0, %YMM0, %k2 > > + VPCMP $0, (%rsi, %OFFSET_REG64, SIZE_OF_CHAR), %YMM0, %k1{%k2} > > + kmovd %k1, %ecx > > + TESTEQ %ecx > > + jnz L(check_ret_vec_page_cross) > > + addl $CHAR_PER_VEC, %OFFSET_REG > > # ifdef USE_AS_STRNCMP > > - cmpq %r11, %rdx > > - jae L(zero) > > + cmpq %OFFSET_REG64, %rdx > > + jbe L(ret_zero_page_cross) > > # endif > > + addl $VEC_SIZE, %eax > > + jl L(page_cross_loop) > > + > > # ifdef USE_AS_WCSCMP > > - movl (%rdi, %rdx), %eax > > - movl (%rsi, %rdx), %ecx > > -# else > > - movzbl (%rdi, %rdx), %eax > > - movzbl (%rsi, %rdx), %ecx > > + shrl $2, %eax > > # endif > > - /* Check null CHAR. */ > > - testl %eax, %eax > > - jne L(cross_page_loop) > > - /* Since %eax == 0, subtract is OK for both SIGNED and UNSIGNED > > - comparisons. */ > > - subl %ecx, %eax > > -# ifndef USE_AS_WCSCMP > > -L(different): > > + > > + > > + subl %eax, %OFFSET_REG > > + /* OFFSET_REG has distance to page cross - VEC_SIZE. Guranteed > > + to not cross page so is safe to load. Since we have already > > + loaded at least 1 VEC from rsi it is also guranteed to be safe. > > + */ > > + VMOVU (%rdi, %OFFSET_REG64, SIZE_OF_CHAR), %YMM0 > > + VPTESTM %YMM0, %YMM0, %k2 > > + VPCMP $0, (%rsi, %OFFSET_REG64, SIZE_OF_CHAR), %YMM0, %k1{%k2} > > + > > + kmovd %k1, %ecx > > +# ifdef USE_AS_STRNCMP > > + leal CHAR_PER_VEC(%OFFSET_REG64), %eax > > + cmpq %rax, %rdx > > + jbe L(check_ret_vec_page_cross2) > > +# ifdef USE_AS_WCSCMP > > + addq $-(CHAR_PER_VEC * 2), %rdx > > +# else > > + addq %rdi, %rdx > > +# endif > > # endif > > - ret > > + TESTEQ %ecx > > + jz L(prepare_loop_no_len) > > > > + .p2align 4,, 4 > > +L(ret_vec_page_cross): > > +# ifndef USE_AS_STRNCMP > > +L(check_ret_vec_page_cross): > > +# endif > > + tzcntl %ecx, %ecx > > + addl %OFFSET_REG, %ecx > > +L(ret_vec_page_cross_cont): > > # ifdef USE_AS_WCSCMP > > - .p2align 4 > > -L(different): > > - /* Use movl to avoid modifying EFLAGS. */ > > - movl $0, %eax > > + movl (%rdi, %rcx, SIZE_OF_CHAR), %edx > > + xorl %eax, %eax > > + cmpl (%rsi, %rcx, SIZE_OF_CHAR), %edx > > + je L(ret12) > > setl %al > > negl %eax > > - orl $1, %eax > > - ret > > + xorl %r8d, %eax > > +# else > > + movzbl (%rdi, %rcx, SIZE_OF_CHAR), %eax > > + movzbl (%rsi, %rcx, SIZE_OF_CHAR), %ecx > > + subl %ecx, %eax > > + xorl %r8d, %eax > > + subl %r8d, %eax > > # endif > > +L(ret12): > > + ret > > + > > > > # ifdef USE_AS_STRNCMP > > - .p2align 4 > > -L(zero): > > + .p2align 4,, 10 > > +L(check_ret_vec_page_cross2): > > + TESTEQ %ecx > > +L(check_ret_vec_page_cross): > > + tzcntl %ecx, %ecx > > + addl %OFFSET_REG, %ecx > > + cmpq %rcx, %rdx > > + ja L(ret_vec_page_cross_cont) > > + .p2align 4,, 2 > > +L(ret_zero_page_cross): > > xorl %eax, %eax > > ret > > +# endif > > > > - .p2align 4 > > -L(char0): > > -# ifdef USE_AS_WCSCMP > > - xorl %eax, %eax > > - movl (%rdi), %ecx > > - cmpl (%rsi), %ecx > > - jne L(wcscmp_return) > > -# else > > - movzbl (%rsi), %ecx > > - movzbl (%rdi), %eax > > - subl %ecx, %eax > > -# endif > > - ret > > + .p2align 4,, 4 > > +L(page_cross_s2): > > + /* Ensure this is a true page cross. */ > > + subl $(PAGE_SIZE - VEC_SIZE * 4), %ecx > > + jbe L(no_page_cross) > > + > > + > > + movl %ecx, %eax > > + movq %rdi, %rcx > > + movq %rsi, %rdi > > + movq %rcx, %rsi > > + > > + /* set r8 to negate return value as rdi and rsi swapped. */ > > +# ifdef USE_AS_WCSCMP > > + movl $-4, %r8d > > +# else > > + movl $-1, %r8d > > # endif > > + xorl %OFFSET_REG, %OFFSET_REG > > > > - .p2align 4 > > -L(last_vector): > > - addq %rdx, %rdi > > - addq %rdx, %rsi > > -# ifdef USE_AS_STRNCMP > > - subq %rdx, %r11 > > + /* Check if more than 1x VEC till page cross. */ > > + subl $(VEC_SIZE * 3), %eax > > + jle L(page_cross_loop) > > + > > + .p2align 4,, 6 > > +L(less_1x_vec_till_page): > > +# ifdef USE_AS_WCSCMP > > + shrl $2, %eax > > # endif > > - tzcntl %ecx, %edx > > + /* Find largest load size we can use. */ > > + cmpl $(16 / SIZE_OF_CHAR), %eax > > + ja L(less_16_till_page) > > + > > + /* Use 16 byte comparison. */ > > + vmovdqu (%rdi), %xmm0 > > + VPTESTM %xmm0, %xmm0, %k2 > > + VPCMP $0, (%rsi), %xmm0, %k1{%k2} > > + kmovd %k1, %ecx > > # ifdef USE_AS_WCSCMP > > - /* NB: Multiply wchar_t count by 4 to get the number of bytes. */ > > - sall $2, %edx > > + subl $0xf, %ecx > > +# else > > + incw %cx > > # endif > > + jnz L(check_ret_vec_page_cross) > > + movl $(16 / SIZE_OF_CHAR), %OFFSET_REG > > # ifdef USE_AS_STRNCMP > > - cmpq %r11, %rdx > > - jae L(zero) > > + cmpq %OFFSET_REG64, %rdx > > + jbe L(ret_zero_page_cross_slow_case0) > > + subl %eax, %OFFSET_REG > > +# else > > + /* Explicit check for 16 byte alignment. */ > > + subl %eax, %OFFSET_REG > > + jz L(prepare_loop) > > # endif > > + vmovdqu (%rdi, %OFFSET_REG64, SIZE_OF_CHAR), %xmm0 > > + VPTESTM %xmm0, %xmm0, %k2 > > + VPCMP $0, (%rsi, %OFFSET_REG64, SIZE_OF_CHAR), %xmm0, %k1{%k2} > > + kmovd %k1, %ecx > > # ifdef USE_AS_WCSCMP > > - xorl %eax, %eax > > - movl (%rdi, %rdx), %ecx > > - cmpl (%rsi, %rdx), %ecx > > - jne L(wcscmp_return) > > + subl $0xf, %ecx > > # else > > - movzbl (%rdi, %rdx), %eax > > - movzbl (%rsi, %rdx), %edx > > - subl %edx, %eax > > + incw %cx > > # endif > > + jnz L(check_ret_vec_page_cross) > > +# ifdef USE_AS_STRNCMP > > + addl $(16 / SIZE_OF_CHAR), %OFFSET_REG > > + subq %OFFSET_REG64, %rdx > > + jbe L(ret_zero_page_cross_slow_case0) > > + subq $-(CHAR_PER_VEC * 4), %rdx > > + > > + leaq -(VEC_SIZE * 4)(%rdi, %OFFSET_REG64, SIZE_OF_CHAR), %rdi > > + leaq -(VEC_SIZE * 4)(%rsi, %OFFSET_REG64, SIZE_OF_CHAR), %rsi > > +# else > > + leaq (16 - VEC_SIZE * 4)(%rdi, %OFFSET_REG64, SIZE_OF_CHAR), %rdi > > + leaq (16 - VEC_SIZE * 4)(%rsi, %OFFSET_REG64, SIZE_OF_CHAR), %rsi > > +# endif > > + jmp L(prepare_loop_aligned) > > + > > +# ifdef USE_AS_STRNCMP > > + .p2align 4,, 2 > > +L(ret_zero_page_cross_slow_case0): > > + xorl %eax, %eax > > ret > > +# endif > > > > - /* Comparing on page boundary region requires special treatment: > > - It must done one vector at the time, starting with the wider > > - ymm vector if possible, if not, with xmm. If fetching 16 bytes > > - (xmm) still passes the boundary, byte comparison must be done. > > - */ > > - .p2align 4 > > -L(cross_page): > > - /* Try one ymm vector at a time. */ > > - cmpl $(PAGE_SIZE - VEC_SIZE), %eax > > - jg L(cross_page_1_vector) > > -L(loop_1_vector): > > - VMOVU (%rdi, %rdx), %YMM0 > > > > - VPTESTM %YMM0, %YMM0, %k2 > > - /* Each bit cleared in K1 represents a mismatch or a null CHAR > > - in YMM0 and 32 bytes at (%rsi, %rdx). */ > > - VPCMP $0, (%rsi, %rdx), %YMM0, %k1{%k2} > > + .p2align 4,, 10 > > +L(less_16_till_page): > > + cmpl $(24 / SIZE_OF_CHAR), %eax > > + ja L(less_8_till_page) > > + > > + /* Use 8 byte comparison. */ > > + vmovq (%rdi), %xmm0 > > + vmovq (%rsi), %xmm1 > > + VPTESTM %xmm0, %xmm0, %k2 > > + VPCMP $0, %xmm1, %xmm0, %k1{%k2} > > kmovd %k1, %ecx > > # ifdef USE_AS_WCSCMP > > - subl $0xff, %ecx > > + subl $0x3, %ecx > > # else > > - incl %ecx > > + incb %cl > > # endif > > - jne L(last_vector) > > + jnz L(check_ret_vec_page_cross) > > > > - addl $VEC_SIZE, %edx > > > > - addl $VEC_SIZE, %eax > > # ifdef USE_AS_STRNCMP > > - /* Return 0 if the current offset (%rdx) >= the maximum offset > > - (%r11). */ > > - cmpq %r11, %rdx > > - jae L(zero) > > + cmpq $(8 / SIZE_OF_CHAR), %rdx > > + jbe L(ret_zero_page_cross_slow_case0) > > # endif > > - cmpl $(PAGE_SIZE - VEC_SIZE), %eax > > - jle L(loop_1_vector) > > -L(cross_page_1_vector): > > - /* Less than 32 bytes to check, try one xmm vector. */ > > - cmpl $(PAGE_SIZE - 16), %eax > > - jg L(cross_page_1_xmm) > > - VMOVU (%rdi, %rdx), %XMM0 > > + movl $(24 / SIZE_OF_CHAR), %OFFSET_REG > > + subl %eax, %OFFSET_REG > > > > - VPTESTM %YMM0, %YMM0, %k2 > > - /* Each bit cleared in K1 represents a mismatch or a null CHAR > > - in XMM0 and 16 bytes at (%rsi, %rdx). */ > > - VPCMP $0, (%rsi, %rdx), %XMM0, %k1{%k2} > > + vmovq (%rdi, %OFFSET_REG64, SIZE_OF_CHAR), %xmm0 > > + vmovq (%rsi, %OFFSET_REG64, SIZE_OF_CHAR), %xmm1 > > + VPTESTM %xmm0, %xmm0, %k2 > > + VPCMP $0, %xmm1, %xmm0, %k1{%k2} > > kmovd %k1, %ecx > > # ifdef USE_AS_WCSCMP > > - subl $0xf, %ecx > > + subl $0x3, %ecx > > # else > > - subl $0xffff, %ecx > > + incb %cl > > # endif > > - jne L(last_vector) > > + jnz L(check_ret_vec_page_cross) > > + > > > > - addl $16, %edx > > -# ifndef USE_AS_WCSCMP > > - addl $16, %eax > > -# endif > > # ifdef USE_AS_STRNCMP > > - /* Return 0 if the current offset (%rdx) >= the maximum offset > > - (%r11). */ > > - cmpq %r11, %rdx > > - jae L(zero) > > + addl $(8 / SIZE_OF_CHAR), %OFFSET_REG > > + subq %OFFSET_REG64, %rdx > > + jbe L(ret_zero_page_cross_slow_case0) > > + subq $-(CHAR_PER_VEC * 4), %rdx > > + > > + leaq -(VEC_SIZE * 4)(%rdi, %OFFSET_REG64, SIZE_OF_CHAR), %rdi > > + leaq -(VEC_SIZE * 4)(%rsi, %OFFSET_REG64, SIZE_OF_CHAR), %rsi > > +# else > > + leaq (8 - VEC_SIZE * 4)(%rdi, %OFFSET_REG64, SIZE_OF_CHAR), %rdi > > + leaq (8 - VEC_SIZE * 4)(%rsi, %OFFSET_REG64, SIZE_OF_CHAR), %rsi > > # endif > > + jmp L(prepare_loop_aligned) > > > > -L(cross_page_1_xmm): > > -# ifndef USE_AS_WCSCMP > > - /* Less than 16 bytes to check, try 8 byte vector. NB: No need > > - for wcscmp nor wcsncmp since wide char is 4 bytes. */ > > - cmpl $(PAGE_SIZE - 8), %eax > > - jg L(cross_page_8bytes) > > - vmovq (%rdi, %rdx), %XMM0 > > - vmovq (%rsi, %rdx), %XMM1 > > > > - VPTESTM %YMM0, %YMM0, %k2 > > - /* Each bit cleared in K1 represents a mismatch or a null CHAR > > - in XMM0 and XMM1. */ > > - VPCMP $0, %XMM1, %XMM0, %k1{%k2} > > - kmovb %k1, %ecx > > + > > + > > + .p2align 4,, 10 > > +L(less_8_till_page): > > # ifdef USE_AS_WCSCMP > > - subl $0x3, %ecx > > + /* If using wchar then this is the only check before we reach > > + the page boundary. */ > > + movl (%rdi), %eax > > + movl (%rsi), %ecx > > + cmpl %ecx, %eax > > + jnz L(ret_less_8_wcs) > > +# ifdef USE_AS_STRNCMP > > + addq $-(CHAR_PER_VEC * 2), %rdx > > + /* We already checked for len <= 1 so cannot hit that case here. > > + */ > > +# endif > > + testl %eax, %eax > > + jnz L(prepare_loop) > > + ret > > + > > + .p2align 4,, 8 > > +L(ret_less_8_wcs): > > + setl %OFFSET_REG8 > > + negl %OFFSET_REG > > + movl %OFFSET_REG, %eax > > + xorl %r8d, %eax > > + ret > > + > > # else > > - subl $0xff, %ecx > > -# endif > > - jne L(last_vector) > > + cmpl $28, %eax > > + ja L(less_4_till_page) > > + > > + vmovd (%rdi), %xmm0 > > + vmovd (%rsi), %xmm1 > > + VPTESTM %xmm0, %xmm0, %k2 > > + VPCMP $0, %xmm1, %xmm0, %k1{%k2} > > + kmovd %k1, %ecx > > + subl $0xf, %ecx > > + jnz L(check_ret_vec_page_cross) > > > > - addl $8, %edx > > - addl $8, %eax > > # ifdef USE_AS_STRNCMP > > - /* Return 0 if the current offset (%rdx) >= the maximum offset > > - (%r11). */ > > - cmpq %r11, %rdx > > - jae L(zero) > > + cmpq $4, %rdx > > + jbe L(ret_zero_page_cross_slow_case1) > > # endif > > + movl $(28 / SIZE_OF_CHAR), %OFFSET_REG > > + subl %eax, %OFFSET_REG > > > > -L(cross_page_8bytes): > > - /* Less than 8 bytes to check, try 4 byte vector. */ > > - cmpl $(PAGE_SIZE - 4), %eax > > - jg L(cross_page_4bytes) > > - vmovd (%rdi, %rdx), %XMM0 > > - vmovd (%rsi, %rdx), %XMM1 > > - > > - VPTESTM %YMM0, %YMM0, %k2 > > - /* Each bit cleared in K1 represents a mismatch or a null CHAR > > - in XMM0 and XMM1. */ > > - VPCMP $0, %XMM1, %XMM0, %k1{%k2} > > + vmovd (%rdi, %OFFSET_REG64, SIZE_OF_CHAR), %xmm0 > > + vmovd (%rsi, %OFFSET_REG64, SIZE_OF_CHAR), %xmm1 > > + VPTESTM %xmm0, %xmm0, %k2 > > + VPCMP $0, %xmm1, %xmm0, %k1{%k2} > > kmovd %k1, %ecx > > -# ifdef USE_AS_WCSCMP > > - subl $0x1, %ecx > > -# else > > subl $0xf, %ecx > > -# endif > > - jne L(last_vector) > > + jnz L(check_ret_vec_page_cross) > > +# ifdef USE_AS_STRNCMP > > + addl $(4 / SIZE_OF_CHAR), %OFFSET_REG > > + subq %OFFSET_REG64, %rdx > > + jbe L(ret_zero_page_cross_slow_case1) > > + subq $-(CHAR_PER_VEC * 4), %rdx > > + > > + leaq -(VEC_SIZE * 4)(%rdi, %OFFSET_REG64, SIZE_OF_CHAR), %rdi > > + leaq -(VEC_SIZE * 4)(%rsi, %OFFSET_REG64, SIZE_OF_CHAR), %rsi > > +# else > > + leaq (4 - VEC_SIZE * 4)(%rdi, %OFFSET_REG64, SIZE_OF_CHAR), %rdi > > + leaq (4 - VEC_SIZE * 4)(%rsi, %OFFSET_REG64, SIZE_OF_CHAR), %rsi > > +# endif > > + jmp L(prepare_loop_aligned) > > + > > > > - addl $4, %edx > > # ifdef USE_AS_STRNCMP > > - /* Return 0 if the current offset (%rdx) >= the maximum offset > > - (%r11). */ > > - cmpq %r11, %rdx > > - jae L(zero) > > + .p2align 4,, 2 > > +L(ret_zero_page_cross_slow_case1): > > + xorl %eax, %eax > > + ret > > # endif > > > > -L(cross_page_4bytes): > > -# endif > > - /* Less than 4 bytes to check, try one byte/dword at a time. */ > > -# ifdef USE_AS_STRNCMP > > - cmpq %r11, %rdx > > - jae L(zero) > > -# endif > > -# ifdef USE_AS_WCSCMP > > - movl (%rdi, %rdx), %eax > > - movl (%rsi, %rdx), %ecx > > -# else > > - movzbl (%rdi, %rdx), %eax > > - movzbl (%rsi, %rdx), %ecx > > -# endif > > - testl %eax, %eax > > - jne L(cross_page_loop) > > + .p2align 4,, 10 > > +L(less_4_till_page): > > + subq %rdi, %rsi > > + /* Extremely slow byte comparison loop. */ > > +L(less_4_loop): > > + movzbl (%rdi), %eax > > + movzbl (%rsi, %rdi), %ecx > > subl %ecx, %eax > > + jnz L(ret_less_4_loop) > > + testl %ecx, %ecx > > + jz L(ret_zero_4_loop) > > +# ifdef USE_AS_STRNCMP > > + decq %rdx > > + jz L(ret_zero_4_loop) > > +# endif > > + incq %rdi > > + /* end condition is reach page boundary (rdi is aligned). */ > > + testl $31, %edi > > + jnz L(less_4_loop) > > + leaq -(VEC_SIZE * 4)(%rdi, %rsi), %rsi > > + addq $-(VEC_SIZE * 4), %rdi > > +# ifdef USE_AS_STRNCMP > > + subq $-(CHAR_PER_VEC * 4), %rdx > > +# endif > > + jmp L(prepare_loop_aligned) > > + > > +L(ret_zero_4_loop): > > + xorl %eax, %eax > > + ret > > +L(ret_less_4_loop): > > + xorl %r8d, %eax > > + subl %r8d, %eax > > ret > > -END (STRCMP) > > +# endif > > +END(STRCMP) > > #endif > > -- > > 2.25.1 > > > > LGTM. > > Reviewed-by: H.J. Lu > > Thanks. > > -- > H.J. I would like to backport this patch to release branches. Any comments or objections? --Sunil