/* strcmp.S * Copyright (C) 2003-2007 Analog Devices Inc., All Rights Reserved. * * This file is subject to the terms and conditions of the GNU Library General * Public License. See the file "COPYING.LIB" in the main directory of this * archive for more details. * * Non-LGPL License also available as part of VisualDSP++ * http://www.analog.com/processors/resources/crosscore/visualDspDevSoftware.html */ #include <sysdep.h> /* Fast strcmp() for Blackfin. * When both strings are aligned, this processes four characters at * a time. Uses a hw loop with "very big" count to loop "forever", * until difference or a terminating zero is found. * Once the end-case word has been identified, breaks out of the * loop to check more carefully (same as the unaligned case). */ .text .align 2 .weak _strcmp ENTRY(_strcmp) [--sp] = (R7:4); p1 = r0; p2 = r1; p0 = -1; // (need for loop counter init) // check if byte aligned r0 = r0 | r1; // check both pointers at same time r0 <<= 30; // dump all but last 2 bits cc = az; // are they zero? if !cc jump .Lunaligned; // no; use unaligned code. // fall-thru for aligned case.. // note that r0 is zero from the previous... // p0 set to -1 LSETUP (.Lbeginloop, .Lendloop) lc0=p0; // pick up first words r1 = [p1++]; r2 = [p2++]; // make up mask: 0FF0FF r7 = 0xFF; r7.h = 0xFF; // loop : 9 cycles to check 4 characters cc = r1 == r2; .Lbeginloop: if !cc jump .Lnotequal4; // compare failure, exit loop // starting with 44332211 // see if char 3 or char 1 is 0 r3 = r1 & r7; // form 00330011 // add to zero, and (r2 is free, reload) r6 = r3 +|+ r0 || r2 = [p2++] || nop; cc = az; // true if either is zero r3 = r1 ^ r3; // form 44002200 (4321^0301 => 4020) // (trick, saves having another mask) // add to zero, and (r1 is free, reload) r6 = r3 +|+ r0 || r1 = [p1++] || nop; cc |= az; // true if either is zero if cc jump .Lzero4; // leave if a zero somewhere .Lendloop: cc = r1 == r2; // loop exits .Lnotequal4: // compare failure on 4-char compare // address pointers are one word ahead; // faster to use zero4 exit code p1 += 4; p2 += 4; .Lzero4: // one of the bytes in word 1 is zero // but we've already fetched the next word; so // backup two to look at failing word again p1 += -8; p2 += -8; // here when pointers are unaligned: checks one // character at a time. Also use at the end of // the word-check algorithm to figure out what happened .Lunaligned: // R0 is non-zero from before. // p0 set to -1 r0 = 0 (Z); r1 = B[p1++] (Z); r2 = B[p2++] (Z); LSETUP (.Lbeginloop1, .Lendloop1) lc0=p0; .Lbeginloop1: cc = r1; // first char must be non-zero // chars must be the same r3 = r2 - r1 (NS) || r1 = B[p1++] (Z) || nop; cc &= az; r3 = r0 - r2; // second char must be non-zero cc &= an; if !cc jump .Lexitloop1; .Lendloop1: r2 = B[p2++] (Z); .Lexitloop1: // here means we found a zero or a difference. // we have r2(N), p2(N), r1(N+1), p1(N+2) r1=B[p1+ -2] (Z); r0 = r1 - r2; (r7:4) = [sp++]; rts; .size _strcmp,.-_strcmp libc_hidden_def (strcmp) #ifndef __UCLIBC_HAS_LOCALE__ weak_alias (strcmp,strcoll) libc_hidden_def (strcoll) #endif