From patchwork Thu Aug 7 13:40:20 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Wilco Dijkstra X-Patchwork-Id: 2338 Received: (qmail 24396 invoked by alias); 7 Aug 2014 13:40:39 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Delivered-To: mailing list libc-alpha@sourceware.org Received: (qmail 24309 invoked by uid 89); 7 Aug 2014 13:40:38 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.0 required=5.0 tests=AWL, BAYES_00, SPF_PASS autolearn=ham version=3.3.2 X-HELO: service87.mimecast.com From: "Wilco Dijkstra" To: Subject: [PATCH] ARM: Fix performance issue in strcpy Date: Thu, 7 Aug 2014 14:40:20 +0100 Message-ID: <000501cfb245$2248d600$66da8200$@com> MIME-Version: 1.0 X-MC-Unique: 114080714403406201 Hi, This patch fixes a performance bug in strcp. The code dealing with unaligned copies uses mvns to detect whether a register is 0. This is incorrect - the zero flag is only set if the value is -1. As a result the code always does a byte-by-byte copy for the full string rather than doing the word-based copy for the misaligned cases. Fixing this more than doubles performance. OK for commit? ChangeLog: 2014-08-07 Wilco Dijkstra * sysdeps/arm/armv6/strcpy.S (strcpy): Fix performance issue in misaligned cases. --- sysdeps/arm/armv6/strcpy.S | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/sysdeps/arm/armv6/strcpy.S b/sysdeps/arm/armv6/strcpy.S index 833a83c..67bd9d8 100644 --- a/sysdeps/arm/armv6/strcpy.S +++ b/sysdeps/arm/armv6/strcpy.S @@ -159,7 +159,7 @@ ENTRY (strcpy) @ Prologue to unaligned loop. Seed shifted non-zero bytes. uqsub8 r4, r7, r2 @ Find EOS uqsub8 r5, r7, r3 - mvns r4, r4 @ EOS in first word? + cmp r4, #0 @ EOS in first word? it ne subne r1, r1, #8 bne .Lbyte_loop @@ -179,7 +179,7 @@ ENTRY (strcpy) @ Rotated unaligned copy loop. The tail of the prologue is @ shared with the loop itself. .balign 8 -1: mvns r5, r5 @ EOS in second word? +1: cmp r5, #0 @ EOS in second word? bne 4f @ Combine first and second words orr r2, r2, r3, lsh_gt #(\unalign*8) @@ -194,7 +194,7 @@ ENTRY (strcpy) sfi_pld r1, #128 uqsub8 r5, r7, r3 sfi_pld r0, #128 - mvns r4, r4 @ EOS in first word? + cmp r4, #0 @ EOS in first word? bne 3f @ Combine the leftover and the first word orr r6, r6, r2, lsh_gt #(\unalign*8)