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