From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-x52b.google.com (mail-pg1-x52b.google.com [IPv6:2607:f8b0:4864:20::52b]) by sourceware.org (Postfix) with ESMTPS id D577A3857C4B for ; Mon, 10 Jan 2022 00:41:46 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org D577A3857C4B Received: by mail-pg1-x52b.google.com with SMTP id f5so9771088pgk.12 for ; Sun, 09 Jan 2022 16:41:46 -0800 (PST) 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=za6xAVgZCsR5VVsNMG5HLunA6dUkNaXuYzxbawx3j4w=; b=tc2rt0n8nbmiiQOa0eUZHt+oT9YPbYMO4V4/1V4qAOf2Cw12pM3FYqeriPe0+m3Wlb LTaT9P++ZKx+5LcY3msXIPrWRuEohojFwVKFQWADt6QJldw/A53pLmQ/3fF7SuKhkpf0 PweJdAWXwZkiPFlLfz3Xnmuy57gDC1Q7zav4+iQl879FSBQQDs0DR4s3mqci3dj+LzKL zcEoVsxkT8b0X0cjXeR4cOc/y8lSzaUgzFYXruHFzk7bEIUfDSje08ikqMmdzynHrFiw Pi6a8UhNd3lJqMbeGIt3qVMXmtKXl7F6KeUWvYkSFeGE4unZm8hVc1eA0wMmzhtfJ7En UtJQ== X-Gm-Message-State: AOAM530Jje4H0An5jI3H95WvpLZrRtoOAGf66+7VTKAHCwo1ctTsbREW yLdrEuWXF1u2RZG/UanUSCFHIw1VrT5gv9cy1BFyTbV5uWs= X-Google-Smtp-Source: ABdhPJzpD0FyJUooTwlMyI5LbmbtOqhdTK2yYEIjFlHsMmx8rAdd4pce1fFPLkgEEWV6apdyO2JNz0jxd7hEAXzLymA= X-Received: by 2002:a63:e50b:: with SMTP id r11mr63457872pgh.210.1641775305275; Sun, 09 Jan 2022 16:41:45 -0800 (PST) MIME-Version: 1.0 References: <20220109122946.2754917-1-goldstein.w.n@gmail.com> <20220110002746.3653516-1-goldstein.w.n@gmail.com> <20220110002746.3653516-5-goldstein.w.n@gmail.com> In-Reply-To: <20220110002746.3653516-5-goldstein.w.n@gmail.com> From: "H.J. Lu" Date: Sun, 9 Jan 2022 16:41:09 -0800 Message-ID: Subject: Re: [PATCH v2 5/7] x86: Optimize strcmp-avx2.S To: Noah Goldstein Cc: GNU C Library Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-3027.9 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=3.4.4 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: Mon, 10 Jan 2022 00:41:51 -0000 On Sun, Jan 9, 2022 at 4:31 PM Noah Goldstein via Libc-alpha 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 are improved most for smaller sizes [0, 128] > and go about even for (128, 4096]. The loop page cross logic is > improved so some more significant speedup is seen there as well. > > test-strcmp, test-strncmp, test-wcscmp, and test-wcsncmp all pass. > > Signed-off-by: Noah Goldstein > --- > sysdeps/x86_64/multiarch/strcmp-avx2.S | 1590 ++++++++++++++---------- > 1 file changed, 939 insertions(+), 651 deletions(-) > > diff --git a/sysdeps/x86_64/multiarch/strcmp-avx2.S b/sysdeps/x86_64/multiarch/strcmp-avx2.S > index 9c73b5899d..28d6a0025a 100644 > --- a/sysdeps/x86_64/multiarch/strcmp-avx2.S > +++ b/sysdeps/x86_64/multiarch/strcmp-avx2.S > @@ -26,35 +26,57 @@ > > # 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 > > -/* 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 vmovdqu > +# define VMOVA vmovdqa > > # ifdef USE_AS_WCSCMP > -/* Compare packed dwords. */ > + /* Compare packed dwords. */ > # define VPCMPEQ vpcmpeqd > -/* Compare packed dwords and store minimum. */ > + /* Compare packed dwords and store minimum. */ > # define VPMINU vpminud > -/* 1 dword char == 4 bytes. */ > + /* 1 dword char == 4 bytes. */ > # define SIZE_OF_CHAR 4 > # else > -/* Compare packed bytes. */ > + /* Compare packed bytes. */ > # define VPCMPEQ vpcmpeqb > -/* Compare packed bytes and store minimum. */ > + /* Compare packed bytes and store minimum. */ > # define VPMINU vpminub > -/* 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 > + > # ifndef VZEROUPPER > # define VZEROUPPER vzeroupper > # endif > > +# if defined USE_AS_STRNCMP > +# define VEC_OFFSET 0 > +# else > +# define VEC_OFFSET (-VEC_SIZE) > +# endif > + > +# define xmmZERO xmm15 > +# define ymmZERO ymm15 > + > # ifndef SECTION > # define SECTION(p) p##.avx > # endif > @@ -79,783 +101,1049 @@ > the maximum offset is reached before a difference is found, zero is > returned. */ > > - .section SECTION(.text),"ax",@progbits > -ENTRY (STRCMP) > + .section SECTION(.text), "ax", @progbits > +ENTRY(STRCMP) > # ifdef USE_AS_STRNCMP > - /* Check for simple cases (0 or 1) in offset. */ > +# ifdef __ILP32__ > + /* Clear the upper 32 bits. */ > + movl %edx, %rdx > +# endif > cmp $1, %RDX_LP > - je L(char0) > - jb L(zero) > + /* 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) > # 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'. */ > + > + /* Multiplying length by sizeof(wchar_t) can result in overflow. > + Check if that is possible. All cases where overflow are possible > + are cases where length is large enough that it can never be a > + bound on valid memory so just use wcscmp. */ > shrq $56, %rcx > jnz __wcscmp_avx2 > + > + leaq (, %rdx, 4), %rdx > # endif > - /* Convert units: from wide to byte char. */ > - shl $2, %RDX_LP > -# endif > - /* Register %r11 tracks the maximum offset. */ > - mov %RDX_LP, %R11_LP > # endif > + vpxor %xmmZERO, %xmmZERO, %xmmZERO > movl %edi, %eax > - xorl %edx, %edx > - /* Make %xmm7 (%ymm7) all zeros in this function. */ > - vpxor %xmm7, %xmm7, %xmm7 > orl %esi, %eax > - andl $(PAGE_SIZE - 1), %eax > - cmpl $(PAGE_SIZE - (VEC_SIZE * 4)), %eax > - jg L(cross_page) > - /* Start comparing 4 vectors. */ > - vmovdqu (%rdi), %ymm1 > - VPCMPEQ (%rsi), %ymm1, %ymm0 > - VPMINU %ymm1, %ymm0, %ymm0 > - VPCMPEQ %ymm7, %ymm0, %ymm0 > - vpmovmskb %ymm0, %ecx > - testl %ecx, %ecx > - je L(next_3_vectors) > - tzcntl %ecx, %edx > + 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 > + /* 1s where s1 and s2 equal. */ > + VPCMPEQ (%rsi), %ymm0, %ymm1 > + /* 1s at null CHAR. */ > + VPCMPEQ %ymm0, %ymmZERO, %ymm2 > + /* 1s where s1 and s2 equal AND not null CHAR. */ > + vpandn %ymm1, %ymm2, %ymm1 > + > + /* All 1s -> keep going, any 0s -> return. */ > + vpmovmskb %ymm1, %ecx > # ifdef USE_AS_STRNCMP > - /* Return 0 if the mismatched index (%rdx) is after the maximum > - offset (%r11). */ > - cmpq %r11, %rdx > - jae L(zero) > + cmpq $VEC_SIZE, %rdx > + jbe L(vec_0_test_len) > # endif > + > + /* All 1s represents all equals. incl will overflow to zero in > + all equals case. Otherwise 1s will carry until position of first > + mismatch. */ > + incl %ecx > + jz L(more_3x_vec) > + > + .p2align 4,, 4 > +L(return_vec_0): > + tzcntl %ecx, %ecx > # ifdef USE_AS_WCSCMP > + movl (%rdi, %rcx), %edx > xorl %eax, %eax > - movl (%rdi, %rdx), %ecx > - cmpl (%rsi, %rdx), %ecx > - je L(return) > -L(wcscmp_return): > + cmpl (%rsi, %rcx), %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): > L(return_vzeroupper): > ZERO_UPPER_VEC_REGISTERS_RETURN > > - .p2align 4 > -L(return_vec_size): > - tzcntl %ecx, %edx > # 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,, 8 > +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 > + VZEROUPPER_RETURN > + > + .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_avx2 > + 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_avx2 > + movzbl (%rdi), %eax > + movzbl (%rsi), %ecx > + subl %ecx, %eax > # endif > +L(ret1): > + ret > # endif > - VZEROUPPER_RETURN > > - .p2align 4 > -L(return_2_vec_size): > - tzcntl %ecx, %edx > + .p2align 4,, 10 > +L(return_vec_1): > + tzcntl %ecx, %ecx > # 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 > + /* rdx must be > CHAR_PER_VEC so save to subtract w.o fear of > + overflow. */ > + addq $-VEC_SIZE, %rdx > + cmpq %rcx, %rdx > + jbe L(ret_zero) > +# endif > +# ifdef USE_AS_WCSCMP > + movl VEC_SIZE(%rdi, %rcx), %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(%rsi, %rcx), %edx > + je L(ret2) > + setl %al > + negl %eax > + orl $1, %eax > # 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 > + movzbl VEC_SIZE(%rdi, %rcx), %eax > + movzbl VEC_SIZE(%rsi, %rcx), %ecx > + subl %ecx, %eax > # endif > +L(ret2): > VZEROUPPER_RETURN > > - .p2align 4 > -L(return_3_vec_size): > - tzcntl %ecx, %edx > + .p2align 4,, 10 > # 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 > +L(return_vec_3): > + salq $32, %rcx > +# endif > + > +L(return_vec_2): > +# ifndef USE_AS_STRNCMP > + tzcntl %ecx, %ecx > +# else > + tzcntq %rcx, %rcx > + cmpq %rcx, %rdx > + jbe L(ret_zero) > +# endif > + > +# ifdef USE_AS_WCSCMP > + movl (VEC_SIZE * 2)(%rdi, %rcx), %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), %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): > + VZEROUPPER_RETURN > + > +# ifndef USE_AS_STRNCMP > + .p2align 4,, 10 > +L(return_vec_3): > + tzcntl %ecx, %ecx > # ifdef USE_AS_WCSCMP > + movl (VEC_SIZE * 3)(%rdi, %rcx), %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), %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): > VZEROUPPER_RETURN > +# endif > + > + .p2align 4,, 10 > +L(more_3x_vec): > + /* Safe to compare 4x vectors. */ > + VMOVU VEC_SIZE(%rdi), %ymm0 > + VPCMPEQ VEC_SIZE(%rsi), %ymm0, %ymm1 > + VPCMPEQ %ymm0, %ymmZERO, %ymm2 > + vpandn %ymm1, %ymm2, %ymm1 > + vpmovmskb %ymm1, %ecx > + incl %ecx > + jnz L(return_vec_1) > + > +# ifdef USE_AS_STRNCMP > + subq $(VEC_SIZE * 2), %rdx > + jbe L(ret_zero) > +# endif > + > + VMOVU (VEC_SIZE * 2)(%rdi), %ymm0 > + VPCMPEQ (VEC_SIZE * 2)(%rsi), %ymm0, %ymm1 > + VPCMPEQ %ymm0, %ymmZERO, %ymm2 > + vpandn %ymm1, %ymm2, %ymm1 > + vpmovmskb %ymm1, %ecx > + incl %ecx > + jnz L(return_vec_2) > + > + VMOVU (VEC_SIZE * 3)(%rdi), %ymm0 > + VPCMPEQ (VEC_SIZE * 3)(%rsi), %ymm0, %ymm1 > + VPCMPEQ %ymm0, %ymmZERO, %ymm2 > + vpandn %ymm1, %ymm2, %ymm1 > + vpmovmskb %ymm1, %ecx > + incl %ecx > + jnz L(return_vec_3) > > - .p2align 4 > -L(next_3_vectors): > - vmovdqu VEC_SIZE(%rdi), %ymm6 > - VPCMPEQ VEC_SIZE(%rsi), %ymm6, %ymm3 > - VPMINU %ymm6, %ymm3, %ymm3 > - VPCMPEQ %ymm7, %ymm3, %ymm3 > - vpmovmskb %ymm3, %ecx > - testl %ecx, %ecx > - jne L(return_vec_size) > - vmovdqu (VEC_SIZE * 2)(%rdi), %ymm5 > - vmovdqu (VEC_SIZE * 3)(%rdi), %ymm4 > - vmovdqu (VEC_SIZE * 3)(%rsi), %ymm0 > - VPCMPEQ (VEC_SIZE * 2)(%rsi), %ymm5, %ymm2 > - VPMINU %ymm5, %ymm2, %ymm2 > - VPCMPEQ %ymm4, %ymm0, %ymm0 > - VPCMPEQ %ymm7, %ymm2, %ymm2 > - vpmovmskb %ymm2, %ecx > - testl %ecx, %ecx > - jne L(return_2_vec_size) > - VPMINU %ymm4, %ymm0, %ymm0 > - VPCMPEQ %ymm7, %ymm0, %ymm0 > - vpmovmskb %ymm0, %ecx > - testl %ecx, %ecx > - 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 > # 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. > + cmpq $(VEC_SIZE * 2), %rdx > + jbe L(ret_zero) > +# endif > + > +# ifdef USE_AS_WCSCMP > + /* any non-zero positive value that doesn't inference with 0x1. > */ > - subq %rdx, %r11 > - jbe L(zero) > -# 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) > + movl $2, %r8d > > +# else > + xorl %r8d, %r8d > +# endif > + > + /* The prepare labels are various entry points from the page > + cross logic. */ > +L(prepare_loop): > + > +# ifdef USE_AS_STRNCMP > + /* Store N + (VEC_SIZE * 4) and place check at the begining of > + the loop. */ > + leaq (VEC_SIZE * 2)(%rdi, %rdx), %rdx > +# endif > +L(prepare_loop_no_len): > + > + /* Align s1 and adjust s2 accordingly. */ > + subq %rdi, %rsi > + andq $-(VEC_SIZE * 4), %rdi > + addq %rdi, %rsi > + > +# ifdef USE_AS_STRNCMP > + 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 > + > + /* 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) > -# 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. */ > - vmovdqa (%rax), %ymm0 > - vmovdqa VEC_SIZE(%rax), %ymm3 > - VPCMPEQ (%rdx), %ymm0, %ymm4 > - VPCMPEQ VEC_SIZE(%rdx), %ymm3, %ymm1 > - VPMINU %ymm0, %ymm4, %ymm4 > - VPMINU %ymm3, %ymm1, %ymm1 > - vmovdqa (VEC_SIZE * 2)(%rax), %ymm2 > - VPMINU %ymm1, %ymm4, %ymm0 > - vmovdqa (VEC_SIZE * 3)(%rax), %ymm3 > - VPCMPEQ (VEC_SIZE * 2)(%rdx), %ymm2, %ymm5 > - VPCMPEQ (VEC_SIZE * 3)(%rdx), %ymm3, %ymm6 > - VPMINU %ymm2, %ymm5, %ymm5 > - VPMINU %ymm3, %ymm6, %ymm6 > - VPMINU %ymm5, %ymm0, %ymm0 > - VPMINU %ymm6, %ymm0, %ymm0 > - VPCMPEQ %ymm7, %ymm0, %ymm0 > - > - /* Test each mask (32 bits) individually because for VEC_SIZE > - == 32 is not possible to OR the four masks and keep all bits > - in a 64-bit integer register, differing from SSE2 strcmp > - where ORing is possible. */ > - vpmovmskb %ymm0, %ecx > + subq $(VEC_SIZE * 4), %rdx > + jbe L(ret_zero) > +# endif > + > + 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 > + > + /* ymm1 all 1s where s1 and s2 equal. All 0s otherwise. */ > + VPCMPEQ (VEC_SIZE * 0)(%rsi), %ymm0, %ymm1 > + > + VPCMPEQ (VEC_SIZE * 1)(%rsi), %ymm2, %ymm3 > + VPCMPEQ (VEC_SIZE * 2)(%rsi), %ymm4, %ymm5 > + VPCMPEQ (VEC_SIZE * 3)(%rsi), %ymm6, %ymm7 > + > + > + /* If any mismatches or null CHAR then 0 CHAR, otherwise non- > + zero. */ > + vpand %ymm0, %ymm1, %ymm1 > + > + > + vpand %ymm2, %ymm3, %ymm3 > + vpand %ymm4, %ymm5, %ymm5 > + vpand %ymm6, %ymm7, %ymm7 > + > + VPMINU %ymm1, %ymm3, %ymm3 > + VPMINU %ymm5, %ymm7, %ymm7 > + > + /* Reduce all 0 CHARs for the 4x VEC into ymm7. */ > + VPMINU %ymm3, %ymm7, %ymm7 > + > + /* If any 0 CHAR then done. */ > + VPCMPEQ %ymm7, %ymmZERO, %ymm7 > + vpmovmskb %ymm7, %LOOP_REG > + testl %LOOP_REG, %LOOP_REG > + jz L(loop) > + > + /* Find which VEC has the mismatch of end of string. */ > + VPCMPEQ %ymm1, %ymmZERO, %ymm1 > + vpmovmskb %ymm1, %ecx > testl %ecx, %ecx > - je L(loop) > - VPCMPEQ %ymm7, %ymm4, %ymm0 > - vpmovmskb %ymm0, %edi > - testl %edi, %edi > - je L(test_vec) > - tzcntl %edi, %ecx > + jnz L(return_vec_0_end) > + > + > + VPCMPEQ %ymm3, %ymmZERO, %ymm3 > + vpmovmskb %ymm3, %ecx > + testl %ecx, %ecx > + jnz L(return_vec_1_end) > + > +L(return_vec_2_3_end): > # ifdef USE_AS_STRNCMP > - cmpq %rcx, %r11 > - jbe L(zero) > -# ifdef USE_AS_WCSCMP > - movq %rax, %rsi > + subq $(VEC_SIZE * 2), %rdx > + jbe L(ret_zero_end) > +# endif > + > + VPCMPEQ %ymm5, %ymmZERO, %ymm5 > + vpmovmskb %ymm5, %ecx > + testl %ecx, %ecx > + jnz L(return_vec_2_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. */ > + tzcntl %LOOP_REG, %LOOP_REG > + > +# ifdef USE_AS_STRNCMP > + subl $-(VEC_SIZE), %LOOP_REG > + cmpq %LOOP_REG64, %rdx > + jbe L(ret_zero_end) > +# endif > + > +# ifdef USE_AS_WCSCMP > + movl (VEC_SIZE * 2 - VEC_OFFSET)(%rdi, %LOOP_REG64), %ecx > 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_SIZE * 2 - VEC_OFFSET)(%rsi, %LOOP_REG64), %ecx > + je L(ret5) > + setl %al > + negl %eax > + xorl %r8d, %eax > # 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 > + movzbl (VEC_SIZE * 2 - VEC_OFFSET)(%rdi, %LOOP_REG64), %eax > + movzbl (VEC_SIZE * 2 - VEC_OFFSET)(%rsi, %LOOP_REG64), %ecx > + subl %ecx, %eax > + xorl %r8d, %eax > + subl %r8d, %eax > # endif > +L(ret5): > VZEROUPPER_RETURN > > - .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) > + .p2align 4,, 2 > +L(ret_zero_end): > + xorl %eax, %eax > + VZEROUPPER_RETURN > # endif > - VPCMPEQ %ymm7, %ymm1, %ymm1 > - vpmovmskb %ymm1, %ecx > - testl %ecx, %ecx > - je L(test_2_vec) > - tzcntl %ecx, %edi > + > + > + /* 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 > - addq $VEC_SIZE, %rdi > - cmpq %rdi, %r11 > - jbe L(zero) > -# ifdef USE_AS_WCSCMP > - movq %rax, %rsi > +L(return_vec_1_end): > + salq $32, %rcx > +# endif > +L(return_vec_0_end): > +# ifndef USE_AS_STRNCMP > + tzcntl %ecx, %ecx > +# else > + tzcntq %rcx, %rcx > + cmpq %rcx, %rdx > + jbe L(ret_zero_end) > +# endif > + > +# ifdef USE_AS_WCSCMP > + movl (%rdi, %rcx), %edx > 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 > + cmpl (%rsi, %rcx), %edx > + je L(ret6) > + setl %al > + negl %eax > + xorl %r8d, %eax > # else > + movzbl (%rdi, %rcx), %eax > + movzbl (%rsi, %rcx), %ecx > + subl %ecx, %eax > + xorl %r8d, %eax > + subl %r8d, %eax > +# endif > +L(ret6): > + VZEROUPPER_RETURN > + > +# ifndef USE_AS_STRNCMP > + .p2align 4,, 10 > +L(return_vec_1_end): > + tzcntl %ecx, %ecx > # ifdef USE_AS_WCSCMP > - movq %rax, %rsi > + movl VEC_SIZE(%rdi, %rcx), %edx > xorl %eax, %eax > - movl VEC_SIZE(%rsi, %rdi), %ecx > - cmpl VEC_SIZE(%rdx, %rdi), %ecx > - jne L(wcscmp_return) > + cmpl VEC_SIZE(%rsi, %rcx), %edx > + je L(ret7) > + setl %al > + negl %eax > + xorl %r8d, %eax > # else > - movzbl VEC_SIZE(%rax, %rdi), %eax > - movzbl VEC_SIZE(%rdx, %rdi), %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): > VZEROUPPER_RETURN > +# endif > > - .p2align 4 > -L(test_2_vec): > + .p2align 4,, 10 > +L(return_vec_2_end): > + tzcntl %ecx, %ecx > # 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) > + cmpq %rcx, %rdx > + jbe L(ret_zero_page_cross) > # endif > - VPCMPEQ %ymm7, %ymm5, %ymm5 > - vpmovmskb %ymm5, %ecx > - testl %ecx, %ecx > - je L(test_3_vec) > - tzcntl %ecx, %edi > -# ifdef USE_AS_STRNCMP > - addq $(VEC_SIZE * 2), %rdi > - cmpq %rdi, %r11 > - jbe L(zero) > -# ifdef USE_AS_WCSCMP > - movq %rax, %rsi > +# ifdef USE_AS_WCSCMP > + movl (VEC_SIZE * 2)(%rdi, %rcx), %edx > 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 > + cmpl (VEC_SIZE * 2)(%rsi, %rcx), %edx > + je L(ret11) > + setl %al > + negl %eax > + xorl %r8d, %eax > # 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 > + movzbl (VEC_SIZE * 2)(%rdi, %rcx), %eax > + movzbl (VEC_SIZE * 2)(%rsi, %rcx), %ecx > + subl %ecx, %eax > + xorl %r8d, %eax > + subl %r8d, %eax > # endif > +L(ret11): > VZEROUPPER_RETURN > > - .p2align 4 > -L(test_3_vec): > + > + /* Page cross in rsi in next 4x VEC. */ > + > + /* TODO: Improve logic here. */ > + .p2align 4,, 10 > +L(page_cross_during_loop): > + /* eax contains [distance_from_page - (VEC_SIZE * 4)]. */ > + > + /* Optimistically rsi and rdi and both aligned inwhich 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) > + > + /* Check if we can safely load a VEC. */ > + cmpl $-(VEC_SIZE * 3), %eax > + jle L(less_1x_vec_till_page_cross) > + > + VMOVA (%rdi), %ymm0 > + VPCMPEQ (%rsi), %ymm0, %ymm1 > + VPCMPEQ %ymm0, %ymmZERO, %ymm2 > + vpandn %ymm1, %ymm2, %ymm1 > + vpmovmskb %ymm1, %ecx > + incl %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 > + VPCMPEQ -VEC_SIZE(%rsi, %rax), %ymm0, %ymm1 > + VPCMPEQ %ymm0, %ymmZERO, %ymm2 > + vpandn %ymm1, %ymm2, %ymm1 > + vpmovmskb %ymm1, %ecx > + > + /* Mask of potentially valid bits. The lower bits can be out of > + range comparisons (but safe regarding page crosses). */ > + movl $-1, %r10d > + shlxl %esi, %r10d, %r10d > + notl %ecx > + > # 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) > -# endif > - VPCMPEQ %ymm7, %ymm6, %ymm6 > - vpmovmskb %ymm6, %esi > - tzcntl %esi, %ecx > + cmpq %rax, %rdx > + jbe L(return_page_cross_end_check) > +# endif > + movl %eax, %OFFSET_REG > + 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 > + > # ifdef USE_AS_STRNCMP > - addq $(VEC_SIZE * 3), %rcx > - cmpq %rcx, %r11 > - jbe L(zero) > -# ifdef USE_AS_WCSCMP > - movq %rax, %rsi > - 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 > + leal -VEC_SIZE(%OFFSET_REG64, %rcx), %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 (VEC_SIZE * 3)(%rsi, %rcx), %esi > - cmpl (VEC_SIZE * 3)(%rdx, %rcx), %esi > - jne L(wcscmp_return) > -# else > - movzbl (VEC_SIZE * 3)(%rax, %rcx), %eax > - movzbl (VEC_SIZE * 3)(%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): > VZEROUPPER_RETURN > > - .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) > - > - vmovdqu (%rax, %r10), %ymm2 > - vmovdqu VEC_SIZE(%rax, %r10), %ymm3 > - VPCMPEQ (%rdx, %r10), %ymm2, %ymm0 > - VPCMPEQ VEC_SIZE(%rdx, %r10), %ymm3, %ymm1 > - VPMINU %ymm2, %ymm0, %ymm0 > - VPMINU %ymm3, %ymm1, %ymm1 > - VPCMPEQ %ymm7, %ymm0, %ymm0 > - VPCMPEQ %ymm7, %ymm1, %ymm1 > - > - vpmovmskb %ymm0, %edi > - vpmovmskb %ymm1, %esi > - > - salq $32, %rsi > - xorq %rsi, %rdi > - > - /* Since ECX < VEC_SIZE * 2, simply skip the first ECX bytes. */ > - shrq %cl, %rdi > - > - testq %rdi, %rdi > - je L(loop_cross_page_2_vec) > - tzcntq %rdi, %rcx > # ifdef USE_AS_STRNCMP > - cmpq %rcx, %r11 > - jbe L(zero) > -# ifdef USE_AS_WCSCMP > - movq %rax, %rsi > + .p2align 4,, 10 > +L(return_page_cross_end_check): > + tzcntl %ecx, %ecx > + leal -VEC_SIZE(%rax, %rcx), %ecx > + cmpl %ecx, %edx > + ja L(return_page_cross_cmp_mem) > 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 > VZEROUPPER_RETURN > +# endif > > - .p2align 4 > -L(loop_cross_page_2_vec): > - /* The first VEC_SIZE * 2 bytes match or are ignored. */ > - vmovdqu (VEC_SIZE * 2)(%rax, %r10), %ymm2 > - vmovdqu (VEC_SIZE * 3)(%rax, %r10), %ymm3 > - VPCMPEQ (VEC_SIZE * 2)(%rdx, %r10), %ymm2, %ymm5 > - VPMINU %ymm2, %ymm5, %ymm5 > - VPCMPEQ (VEC_SIZE * 3)(%rdx, %r10), %ymm3, %ymm6 > - VPCMPEQ %ymm7, %ymm5, %ymm5 > - VPMINU %ymm3, %ymm6, %ymm6 > - VPCMPEQ %ymm7, %ymm6, %ymm6 > - > - vpmovmskb %ymm5, %edi > - vpmovmskb %ymm6, %esi > - > - salq $32, %rsi > - xorq %rsi, %rdi > > - xorl %r8d, %r8d > - /* If ECX > VEC_SIZE * 2, skip ECX - (VEC_SIZE * 2) bytes. */ > - subl $(VEC_SIZE * 2), %ecx > - jle 1f > - /* Skip ECX bytes. */ > - shrq %cl, %rdi > - /* R8 has number of bytes skipped. */ > - movl %ecx, %r8d > -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 > + .p2align 4,, 10 > +L(more_2x_vec_till_page_cross): > + /* If more 2x vec till cross we will complete a full loop > + iteration here. */ > + > + VMOVU VEC_SIZE(%rdi), %ymm0 > + VPCMPEQ VEC_SIZE(%rsi), %ymm0, %ymm1 > + VPCMPEQ %ymm0, %ymmZERO, %ymm2 > + vpandn %ymm1, %ymm2, %ymm1 > + vpmovmskb %ymm1, %ecx > + incl %ecx > + jnz L(return_vec_1_end) > + > # 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) > -# else > - je L(back_to_loop) > + cmpq $(VEC_SIZE * 2), %rdx > + jbe L(ret_zero_in_loop_page_cross) > # endif > - tzcntq %rdi, %rcx > - addq %r10, %rcx > - /* Adjust for number of bytes skipped. */ > - addq %r8, %rcx > + > + subl $-(VEC_SIZE * 4), %eax > + > + /* Safe to include comparisons from lower bytes. */ > + VMOVU -(VEC_SIZE * 2)(%rdi, %rax), %ymm0 > + VPCMPEQ -(VEC_SIZE * 2)(%rsi, %rax), %ymm0, %ymm1 > + VPCMPEQ %ymm0, %ymmZERO, %ymm2 > + vpandn %ymm1, %ymm2, %ymm1 > + vpmovmskb %ymm1, %ecx > + incl %ecx > + jnz L(return_vec_page_cross_0) > + > + VMOVU -(VEC_SIZE * 1)(%rdi, %rax), %ymm0 > + VPCMPEQ -(VEC_SIZE * 1)(%rsi, %rax), %ymm0, %ymm1 > + VPCMPEQ %ymm0, %ymmZERO, %ymm2 > + vpandn %ymm1, %ymm2, %ymm1 > + vpmovmskb %ymm1, %ecx > + incl %ecx > + jnz L(return_vec_page_cross_1) > + > # ifdef USE_AS_STRNCMP > - addq $(VEC_SIZE * 2), %rcx > - subq %rcx, %r11 > - jbe L(zero) > -# ifdef USE_AS_WCSCMP > - movq %rax, %rsi > + /* Must check length here as length might proclude reading next > + page. */ > + cmpq %rax, %rdx > + jbe L(ret_zero_in_loop_page_cross) > +# endif > + > + /* Finish the loop. */ > + VMOVA (VEC_SIZE * 2)(%rdi), %ymm4 > + VMOVA (VEC_SIZE * 3)(%rdi), %ymm6 > + > + VPCMPEQ (VEC_SIZE * 2)(%rsi), %ymm4, %ymm5 > + VPCMPEQ (VEC_SIZE * 3)(%rsi), %ymm6, %ymm7 > + vpand %ymm4, %ymm5, %ymm5 > + vpand %ymm6, %ymm7, %ymm7 > + VPMINU %ymm5, %ymm7, %ymm7 > + VPCMPEQ %ymm7, %ymmZERO, %ymm7 > + vpmovmskb %ymm7, %LOOP_REG > + testl %LOOP_REG, %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 $(VEC_SIZE * 4), %rdx > + ja L(loop_skip_page_cross_check) > +L(ret_zero_in_loop_page_cross): > 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 > + VZEROUPPER_RETURN > # 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 > + jmp L(loop_skip_page_cross_check) > # endif > - VZEROUPPER_RETURN > > + > + .p2align 4,, 10 > +L(return_vec_page_cross_0): > + addl $-VEC_SIZE, %eax > +L(return_vec_page_cross_1): > + tzcntl %ecx, %ecx > # 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) > + leal -VEC_SIZE(%rax, %rcx), %ecx > + cmpq %rcx, %rdx > + jbe L(ret_zero_in_loop_page_cross) > +# else > + addl %eax, %ecx > # endif > > - .p2align 4 > -L(cross_page_loop): > - /* Check one byte/dword at a time. */ > # ifdef USE_AS_WCSCMP > - cmpl %ecx, %eax > + movl VEC_OFFSET(%rdi, %rcx), %edx > + xorl %eax, %eax > + cmpl VEC_OFFSET(%rsi, %rcx), %edx > + je L(ret9) > + 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 > - jne L(different) > - addl $SIZE_OF_CHAR, %edx > - cmpl $(VEC_SIZE * 4), %edx > - je L(main_loop_header) > -# ifdef USE_AS_STRNCMP > - cmpq %r11, %rdx > - jae L(zero) > +L(ret9): > + VZEROUPPER_RETURN > + > + > + .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 > + > + 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 > - movl (%rdi, %rdx), %eax > - movl (%rsi, %rdx), %ecx > + /* any non-zero positive value that doesn't inference with 0x1. > + */ > + movl $2, %r8d > # else > - movzbl (%rdi, %rdx), %eax > - movzbl (%rsi, %rdx), %ecx > + xorl %r8d, %r8d > # 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): > + > + /* 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,, 10 > +L(page_cross_loop): > + > + VMOVU (%rdi, %OFFSET_REG64), %ymm0 > + VPCMPEQ (%rsi, %OFFSET_REG64), %ymm0, %ymm1 > + VPCMPEQ %ymm0, %ymmZERO, %ymm2 > + vpandn %ymm1, %ymm2, %ymm1 > + vpmovmskb %ymm1, %ecx > + incl %ecx > + > + jnz L(check_ret_vec_page_cross) > + addl $VEC_SIZE, %OFFSET_REG > +# ifdef USE_AS_STRNCMP > + cmpq %OFFSET_REG64, %rdx > + jbe L(ret_zero_page_cross) > # endif > - VZEROUPPER_RETURN > + addl $VEC_SIZE, %eax > + jl L(page_cross_loop) > + > + 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), %ymm0 > + VPCMPEQ (%rsi, %OFFSET_REG64), %ymm0, %ymm1 > + VPCMPEQ %ymm0, %ymmZERO, %ymm2 > + vpandn %ymm1, %ymm2, %ymm1 > + vpmovmskb %ymm1, %ecx > + > +# ifdef USE_AS_STRNCMP > + leal VEC_SIZE(%OFFSET_REG64), %eax > + cmpq %rax, %rdx > + jbe L(check_ret_vec_page_cross2) > + addq %rdi, %rdx > +# endif > + incl %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), %edx > + xorl %eax, %eax > + cmpl (%rsi, %rcx), %edx > + je L(ret12) > setl %al > negl %eax > - orl $1, %eax > - VZEROUPPER_RETURN > + xorl %r8d, %eax > +# else > + movzbl (%rdi, %rcx), %eax > + movzbl (%rsi, %rcx), %ecx > + subl %ecx, %eax > + xorl %r8d, %eax > + subl %r8d, %eax > # endif > +L(ret12): > + VZEROUPPER_RETURN > > # ifdef USE_AS_STRNCMP > - .p2align 4 > -L(zero): > + .p2align 4,, 10 > +L(check_ret_vec_page_cross2): > + incl %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 > VZEROUPPER_RETURN > +# 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 > - VZEROUPPER_RETURN > + .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 > + /* 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): > + /* Find largest load size we can use. */ > + cmpl $16, %eax > + ja L(less_16_till_page) > + > + VMOVU (%rdi), %xmm0 > + VPCMPEQ (%rsi), %xmm0, %xmm1 > + VPCMPEQ %xmm0, %xmmZERO, %xmm2 > + vpandn %xmm1, %xmm2, %xmm1 > + vpmovmskb %ymm1, %ecx > + incw %cx > + jnz L(check_ret_vec_page_cross) > + movl $16, %OFFSET_REG > # ifdef USE_AS_STRNCMP > - subq %rdx, %r11 > + 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 > - tzcntl %ecx, %edx > + > + VMOVU (%rdi, %OFFSET_REG64), %xmm0 > + VPCMPEQ (%rsi, %OFFSET_REG64), %xmm0, %xmm1 > + VPCMPEQ %xmm0, %xmmZERO, %xmm2 > + vpandn %xmm1, %xmm2, %xmm1 > + vpmovmskb %ymm1, %ecx > + incw %cx > + jnz L(check_ret_vec_page_cross) > + > # ifdef USE_AS_STRNCMP > - cmpq %r11, %rdx > - jae L(zero) > + addl $16, %OFFSET_REG > + subq %OFFSET_REG64, %rdx > + jbe L(ret_zero_page_cross_slow_case0) > + subq $-(VEC_SIZE * 4), %rdx > + > + leaq -(VEC_SIZE * 4)(%rdi, %OFFSET_REG64), %rdi > + leaq -(VEC_SIZE * 4)(%rsi, %OFFSET_REG64), %rsi > +# else > + leaq (16 - VEC_SIZE * 4)(%rdi, %OFFSET_REG64), %rdi > + leaq (16 - VEC_SIZE * 4)(%rsi, %OFFSET_REG64), %rsi > # endif > -# ifdef USE_AS_WCSCMP > + jmp L(prepare_loop_aligned) > + > +# ifdef USE_AS_STRNCMP > + .p2align 4,, 2 > +L(ret_zero_page_cross_slow_case0): > 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 > + ret > # endif > - VZEROUPPER_RETURN > > - /* 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): > - vmovdqu (%rdi, %rdx), %ymm1 > - VPCMPEQ (%rsi, %rdx), %ymm1, %ymm0 > - VPMINU %ymm1, %ymm0, %ymm0 > - VPCMPEQ %ymm7, %ymm0, %ymm0 > - vpmovmskb %ymm0, %ecx > - testl %ecx, %ecx > - jne L(last_vector) > > - addl $VEC_SIZE, %edx > + .p2align 4,, 10 > +L(less_16_till_page): > + /* Find largest load size we can use. */ > + cmpl $24, %eax > + ja L(less_8_till_page) > > - 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) > -# 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) > - vmovdqu (%rdi, %rdx), %xmm1 > - VPCMPEQ (%rsi, %rdx), %xmm1, %xmm0 > - VPMINU %xmm1, %xmm0, %xmm0 > - VPCMPEQ %xmm7, %xmm0, %xmm0 > - vpmovmskb %xmm0, %ecx > - testl %ecx, %ecx > - jne L(last_vector) > + vmovq (%rdi), %xmm0 > + vmovq (%rsi), %xmm1 > + VPCMPEQ %xmm0, %xmmZERO, %xmm2 > + VPCMPEQ %xmm1, %xmm0, %xmm1 > + vpandn %xmm1, %xmm2, %xmm1 > + vpmovmskb %ymm1, %ecx > + incb %cl > + jnz L(check_ret_vec_page_cross) > > - addl $16, %edx > -# ifndef USE_AS_WCSCMP > - addl $16, %eax > + > +# ifdef USE_AS_STRNCMP > + cmpq $8, %rdx > + jbe L(ret_zero_page_cross_slow_case0) > # endif > + movl $24, %OFFSET_REG > + /* Explicit check for 16 byte alignment. */ > + subl %eax, %OFFSET_REG > + > + > + > + vmovq (%rdi, %OFFSET_REG64), %xmm0 > + vmovq (%rsi, %OFFSET_REG64), %xmm1 > + VPCMPEQ %xmm0, %xmmZERO, %xmm2 > + VPCMPEQ %xmm1, %xmm0, %xmm1 > + vpandn %xmm1, %xmm2, %xmm1 > + vpmovmskb %ymm1, %ecx > + incb %cl > + jnz L(check_ret_vec_page_cross) > + > # ifdef USE_AS_STRNCMP > - /* Return 0 if the current offset (%rdx) >= the maximum offset > - (%r11). */ > - cmpq %r11, %rdx > - jae L(zero) > -# endif > - > -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), %xmm1 > - vmovq (%rsi, %rdx), %xmm0 > - VPCMPEQ %xmm0, %xmm1, %xmm0 > - VPMINU %xmm1, %xmm0, %xmm0 > - VPCMPEQ %xmm7, %xmm0, %xmm0 > - vpmovmskb %xmm0, %ecx > - /* Only last 8 bits are valid. */ > - andl $0xff, %ecx > - testl %ecx, %ecx > - jne L(last_vector) > + addl $8, %OFFSET_REG > + subq %OFFSET_REG64, %rdx > + jbe L(ret_zero_page_cross_slow_case0) > + subq $-(VEC_SIZE * 4), %rdx > > - addl $8, %edx > - addl $8, %eax > + leaq -(VEC_SIZE * 4)(%rdi, %OFFSET_REG64), %rdi > + leaq -(VEC_SIZE * 4)(%rsi, %OFFSET_REG64), %rsi > +# else > + leaq (8 - VEC_SIZE * 4)(%rdi, %OFFSET_REG64), %rdi > + leaq (8 - VEC_SIZE * 4)(%rsi, %OFFSET_REG64), %rsi > +# endif > + jmp L(prepare_loop_aligned) > + > + > + .p2align 4,, 10 > +L(less_8_till_page): > +# ifdef USE_AS_WCSCMP > + /* 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 > - /* Return 0 if the current offset (%rdx) >= the maximum offset > - (%r11). */ > - cmpq %r11, %rdx > - jae L(zero) > + addq %rdi, %rdx > + /* We already checked for len <= 1 so cannot hit that case here. > + */ > # endif > + testl %eax, %eax > + jnz L(prepare_loop_no_len) > + ret > > -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), %xmm1 > - vmovd (%rsi, %rdx), %xmm0 > - VPCMPEQ %xmm0, %xmm1, %xmm0 > - VPMINU %xmm1, %xmm0, %xmm0 > - VPCMPEQ %xmm7, %xmm0, %xmm0 > - vpmovmskb %xmm0, %ecx > - /* Only last 4 bits are valid. */ > - andl $0xf, %ecx > - testl %ecx, %ecx > - jne L(last_vector) > + .p2align 4,, 8 > +L(ret_less_8_wcs): > + setl %OFFSET_REG8 > + negl %OFFSET_REG > + movl %OFFSET_REG, %eax > + xorl %r8d, %eax > + ret > + > +# else > + > + /* Find largest load size we can use. */ > + cmpl $28, %eax > + ja L(less_4_till_page) > + > + vmovd (%rdi), %xmm0 > + vmovd (%rsi), %xmm1 > + VPCMPEQ %xmm0, %xmmZERO, %xmm2 > + VPCMPEQ %xmm1, %xmm0, %xmm1 > + vpandn %xmm1, %xmm2, %xmm1 > + vpmovmskb %ymm1, %ecx > + subl $0xf, %ecx > + jnz L(check_ret_vec_page_cross) > > - addl $4, %edx > # 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, %OFFSET_REG > + /* Explicit check for 16 byte alignment. */ > + subl %eax, %OFFSET_REG > > -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) > + > + > + vmovd (%rdi, %OFFSET_REG64), %xmm0 > + vmovd (%rsi, %OFFSET_REG64), %xmm1 > + VPCMPEQ %xmm0, %xmmZERO, %xmm2 > + VPCMPEQ %xmm1, %xmm0, %xmm1 > + vpandn %xmm1, %xmm2, %xmm1 > + vpmovmskb %ymm1, %ecx > + subl $0xf, %ecx > + jnz L(check_ret_vec_page_cross) > + > +# ifdef USE_AS_STRNCMP > + addl $4, %OFFSET_REG > + subq %OFFSET_REG64, %rdx > + jbe L(ret_zero_page_cross_slow_case1) > + subq $-(VEC_SIZE * 4), %rdx > + > + leaq -(VEC_SIZE * 4)(%rdi, %OFFSET_REG64), %rdi > + leaq -(VEC_SIZE * 4)(%rsi, %OFFSET_REG64), %rsi > +# else > + leaq (4 - VEC_SIZE * 4)(%rdi, %OFFSET_REG64), %rdi > + leaq (4 - VEC_SIZE * 4)(%rsi, %OFFSET_REG64), %rsi > +# endif > + jmp L(prepare_loop_aligned) > + > +# ifdef USE_AS_STRNCMP > + .p2align 4,, 2 > +L(ret_zero_page_cross_slow_case1): > + xorl %eax, %eax > + ret > +# endif > + > + .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 > - VZEROUPPER_RETURN > -END (STRCMP) > + 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 $-(VEC_SIZE * 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 > +# endif > +END(STRCMP) > #endif > -- > 2.25.1 > LGTM. Reviewed-by: H.J. Lu Thanks. -- H.J.