1/* $OpenBSD: bcopy.S,v 1.3 2005/08/07 16:40:15 espie 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 <machine/asm.h> 35 36/* bcopy(s1, s2, n) */ 37 38 39LEAF(bcopy, 0) 40 .set noreorder 41 addu t0, a0, a2 # t0 = end of s1 region 42 sltu t1, a1, t0 43 sltu t2, a0, a1 44 and t1, t1, t2 # t1 = true if from < to < (from+len) 45 beq t1, zero, forward # non overlapping, do forward copy 46 slt t2, a2, 12 # check for small copy 47 48 ble a2, zero, 2f 49 addu t1, a1, a2 # t1 = end of to region 501: 51 lb v0, -1(t0) # copy bytes backwards, 52 subu t0, t0, 1 # does not happen often so do slow way 53 subu t1, t1, 1 54 bne t0, a0, 1b 55 sb v0, 0(t1) 562: 57 j ra 58 nop 59forward: 60 bne t2, zero, smallcpy # do a small bcopy 61 xor v0, a0, a1 # compare low two bits of addresses 62 and v0, v0, 3 63 subu a3, zero, a1 # compute # bytes to word align address 64 beq v0, zero, aligned # addresses can be word aligned 65 and a3, a3, 3 66 67 beq a3, zero, 1f 68 subu a2, a2, a3 # subtract from remaining count 69 LWHI v0, 0(a0) # get next 4 bytes (unaligned) 70 LWLO v0, 3(a0) 71 addu a0, a0, a3 72 SWHI v0, 0(a1) # store 1, 2, or 3 bytes to align a1 73 addu a1, a1, a3 741: 75 and v0, a2, 3 # compute number of words left 76 subu a3, a2, v0 77 move a2, v0 78 addu a3, a3, a0 # compute ending address 792: 80 LWHI v0, 0(a0) # copy words a0 unaligned, a1 aligned 81 LWLO v0, 3(a0) 82 addu a0, a0, 4 83 addu a1, a1, 4 84 bne a0, a3, 2b 85 sw v0, -4(a1) 86 b smallcpy 87 nop 88aligned: 89 beq a3, zero, 1f 90 subu a2, a2, a3 # subtract from remaining count 91 LWHI v0, 0(a0) # copy 1, 2, or 3 bytes to align 92 addu a0, a0, a3 93 SWHI v0, 0(a1) 94 addu a1, a1, a3 951: 96 and v0, a2, 3 # compute number of whole words left 97 subu a3, a2, v0 98 move a2, v0 99 addu a3, a3, a0 # compute ending address 1002: 101 lw v0, 0(a0) # copy words 102 addu a0, a0, 4 103 addu a1, a1, 4 104 bne a0, a3, 2b 105 sw v0, -4(a1) 106smallcpy: 107 ble a2, zero, 2f 108 addu a3, a2, a0 # compute ending address 1091: 110 lbu v0, 0(a0) # copy bytes 111 addu a0, a0, 1 112 addu a1, a1, 1 113 bne a0, a3, 1b 114 sb v0, -1(a1) 1152: 116 j ra 117 nop 118 .set reorder 119END(bcopy) 120