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[69.181.90.243]) by smtp.gmail.com with ESMTPSA id u61sm7760879pjb.7.2020.06.13.04.23.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 13 Jun 2020 04:23:19 -0700 (PDT) Received: from gnu-cfl-2.localdomain (localhost [IPv6:::1]) by gnu-cfl-2.localdomain (Postfix) with ESMTP id 171D61A00D5; Sat, 13 Jun 2020 04:23:18 -0700 (PDT) To: libc-alpha@sourceware.org Subject: [PATCH] Fix avx2 strncmp offset compare condition check [BZ #25933] Date: Sat, 13 Jun 2020 04:23:17 -0700 Message-Id: <20200613112317.3631-1-hjl.tools@gmail.com> X-Mailer: git-send-email 2.26.2 MIME-Version: 1.0 X-Spam-Status: No, score=-13.5 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=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) 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-Patchwork-Original-From: "H.J. Lu via Libc-alpha" From: "H.J. Lu" Reply-To: "H.J. Lu" Cc: Sunil K Pandey Errors-To: libc-alpha-bounces@sourceware.org Sender: "Libc-alpha" From: Sunil K Pandey strcmp-avx2.S: In avx2 strncmp function, strings are compared in chunks of 4 vector size(i.e. 32x4=128 byte for avx2). After first 4 vector size comparison, code must check whether it already passed the given offset. This patch implement avx2 offset check condition for strncmp function, if both string compare same for first 4 vector size. --- sysdeps/x86_64/multiarch/strcmp-avx2.S | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/sysdeps/x86_64/multiarch/strcmp-avx2.S b/sysdeps/x86_64/multiarch/strcmp-avx2.S index 48d03a9f46..ee82fa3e19 100644 --- a/sysdeps/x86_64/multiarch/strcmp-avx2.S +++ b/sysdeps/x86_64/multiarch/strcmp-avx2.S @@ -591,7 +591,14 @@ L(loop_cross_page_2_vec): 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) +# else je L(back_to_loop) +# endif tzcntq %rdi, %rcx addq %r10, %rcx /* Adjust for number of bytes skipped. */ @@ -627,6 +634,14 @@ L(loop_cross_page_2_vec): VZEROUPPER 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) +# endif + .p2align 4 L(cross_page_loop): /* Check one byte/dword at a time. */