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Annotation of sys/lib/libkern/arch/mips64/bcmp.S, Revision 1.1.1.1

1.1       nbrk        1: /*     $OpenBSD: bcmp.S,v 1.4 2004/10/08 14:42:09 pefo Exp $   */
                      2: /*-
                      3:  * Copyright (c) 1991, 1993
                      4:  *      The Regents of the University of California.  All rights reserved.
                      5:  *
                      6:  * This code is derived from software contributed to Berkeley by
                      7:  * Ralph Campbell.
                      8:  *
                      9:  * Redistribution and use in source and binary forms, with or without
                     10:  * modification, are permitted provided that the following conditions
                     11:  * are met:
                     12:  * 1. Redistributions of source code must retain the above copyright
                     13:  *    notice, this list of conditions and the following disclaimer.
                     14:  * 2. Redistributions in binary form must reproduce the above copyright
                     15:  *    notice, this list of conditions and the following disclaimer in the
                     16:  *    documentation and/or other materials provided with the distribution.
                     17:  * 3. Neither the name of the University nor the names of its contributors
                     18:  *    may be used to endorse or promote products derived from this software
                     19:  *    without specific prior written permission.
                     20:  *
                     21:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
                     22:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
                     23:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
                     24:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
                     25:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
                     26:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
                     27:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
                     28:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
                     29:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
                     30:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
                     31:  * SUCH DAMAGE.
                     32:  */
                     33:
                     34: #include "DEFS.h"
                     35:
                     36:
                     37: /*
                     38:  * bcmp(s1, s2, n)
                     39:  */
                     40: LEAF(bcmp, 0)
                     41:        .set    noreorder
                     42:        blt     a2, 16, smallcmp        # is it worth any trouble?
                     43:        xor     v0, a0, a1              # compare low two bits of addresses
                     44:        and     v0, v0, 3
                     45:        PTR_SUBU a3, zero, a1           # compute # bytes to word align address
                     46:        bne     v0, zero, unalignedcmp  # not possible to align addresses
                     47:        and     a3, a3, 3
                     48:
                     49:        beq     a3, zero, 1f
                     50:        PTR_SUBU a2, a2, a3             # subtract from remaining count
                     51:        move    v0, v1                  # init v0,v1 so unmodified bytes match
                     52:        LWHI    v0, 0(a0)               # read 1, 2, or 3 bytes
                     53:        LWHI    v1, 0(a1)
                     54:        PTR_ADDU a1, a1, a3
                     55:        bne     v0, v1, nomatch
                     56:        PTR_ADDU a0, a0, a3
                     57: 1:
                     58:        and     a3, a2, ~3              # compute number of whole words left
                     59:        PTR_SUBU a2, a2, a3             #   which has to be >= (16-3) & ~3
                     60:        PTR_ADDU a3, a3, a0             # compute ending address
                     61: 2:
                     62:        lw      v0, 0(a0)               # compare words
                     63:        lw      v1, 0(a1)
                     64:        PTR_ADDU a0, a0, 4
                     65:        bne     v0, v1, nomatch
                     66:        PTR_ADDU a1, a1, 4
                     67:        bne     a0, a3, 2b
                     68:        nop
                     69:        b       smallcmp                # finish remainder
                     70:        nop
                     71: unalignedcmp:
                     72:        beq     a3, zero, 2f
                     73:        PTR_SUBU a2, a2, a3             # subtract from remaining count
                     74:        PTR_ADDU a3, a3, a0             # compute ending address
                     75: 1:
                     76:        lbu     v0, 0(a0)               # compare bytes until a1 word aligned
                     77:        lbu     v1, 0(a1)
                     78:        PTR_ADDU a0, a0, 1
                     79:        bne     v0, v1, nomatch
                     80:        PTR_ADDU a1, a1, 1
                     81:        bne     a0, a3, 1b
                     82:        nop
                     83: 2:
                     84:        and     a3, a2, ~3              # compute number of whole words left
                     85:        PTR_SUBU a2, a2, a3             #   which has to be >= (16-3) & ~3
                     86:        PTR_ADDU a3, a3, a0             # compute ending address
                     87: 3:
                     88:        LWHI    v0, 0(a0)               # compare words a0 unaligned, a1 aligned
                     89:        LWLO    v0, 3(a0)
                     90:        lw      v1, 0(a1)
                     91:        PTR_ADDU a0, a0, 4
                     92:        bne     v0, v1, nomatch
                     93:        PTR_ADDU a1, a1, 4
                     94:        bne     a0, a3, 3b
                     95:        nop
                     96: smallcmp:
                     97:        ble     a2, zero, match
                     98:        PTR_ADDU a3, a2, a0             # compute ending address
                     99: 1:
                    100:        lbu     v0, 0(a0)
                    101:        lbu     v1, 0(a1)
                    102:        PTR_ADDU a0, a0, 1
                    103:        bne     v0, v1, nomatch
                    104:        PTR_ADDU a1, a1, 1
                    105:        bne     a0, a3, 1b
                    106:        nop
                    107: match:
                    108:        j       ra
                    109:        move    v0, zero
                    110: nomatch:
                    111:        j       ra
                    112:        dli     v0, 1
                    113: END(bcmp)