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Annotation of sys/lib/libkern/arch/arm/memset.S, Revision 1.1.1.1

1.1       nbrk        1: /*     $OpenBSD: memset.S,v 1.2 2004/02/01 05:47:10 drahn Exp $        */
                      2: /*     $NetBSD: memset.S,v 1.1 2000/12/29 20:51:57 bjh21 Exp $ */
                      3:
                      4: /*
                      5:  * Copyright (c) 1995 Mark Brinicombe.
                      6:  * All rights reserved.
                      7:  *
                      8:  * Redistribution and use in source and binary forms, with or without
                      9:  * modification, are permitted provided that the following conditions
                     10:  * are met:
                     11:  * 1. Redistributions of source code must retain the above copyright
                     12:  *    notice, this list of conditions and the following disclaimer.
                     13:  * 2. Redistributions in binary form must reproduce the above copyright
                     14:  *    notice, this list of conditions and the following disclaimer in the
                     15:  *    documentation and/or other materials provided with the distribution.
                     16:  * 3. All advertising materials mentioning features or use of this software
                     17:  *    must display the following acknowledgement:
                     18:  *     This product includes software developed by Mark Brinicombe.
                     19:  * 4. The name of the company nor the name of the author may be used to
                     20:  *    endorse or promote products derived from this software without specific
                     21:  *    prior written permission.
                     22:  *
                     23:  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
                     24:  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
                     25:  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
                     26:  * IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
                     27:  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
                     28:  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
                     29:  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
                     30:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
                     31:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
                     32:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
                     33:  * SUCH DAMAGE.
                     34:  */
                     35:
                     36: #include <machine/asm.h>
                     37:
                     38: /*
                     39:  * Sets a block of memory to the specified value
                     40:  *
                     41:  * On entry:
                     42:  *   r0 - dest address
                     43:  *   r1 - byte to write
                     44:  *   r2 - number of bytes to write
                     45:  *
                     46:  * On exit:
                     47:  *   r0 - dest address
                     48:  */
                     49:
                     50: ENTRY(memset)
                     51:        stmfd   sp!, {r0}               /* Remember address for return value */
                     52:        and     r1, r1, #0x000000ff     /* We write bytes */
                     53:
                     54:        cmp     r2, #0x00000004         /* Do we have less than 4 bytes */
                     55:        blt     Lmemset_lessthanfour
                     56:
                     57:        /* Ok first we will word align the address */
                     58:
                     59:        ands    r3, r0, #0x00000003     /* Get the bottom two bits */
                     60:        beq     Lmemset_addraligned     /* The address is word aligned */
                     61:
                     62:        rsb     r3, r3, #0x00000004
                     63:        sub     r2, r2, r3
                     64:        cmp     r3, #0x00000002
                     65:        strb    r1, [r0], #0x0001       /* Set 1 byte */
                     66:        strgeb  r1, [r0], #0x0001       /* Set another byte */
                     67:        strgtb  r1, [r0], #0x0001       /* and a third */
                     68:
                     69:        cmp     r2, #0x00000004
                     70:        blt     Lmemset_lessthanfour
                     71:
                     72:        /* Now we must be word aligned */
                     73:
                     74: Lmemset_addraligned:
                     75:
                     76:        orr     r3, r1, r1, lsl #8      /* Repeat the byte into a word */
                     77:        orr     r3, r3, r3, lsl #16
                     78:
                     79:        /* We know we have at least 4 bytes ... */
                     80:
                     81:        cmp     r2, #0x00000020         /* If less than 32 then use words */
                     82:        blt     Lmemset_lessthan32
                     83:
                     84:        /* We have at least 32 so lets use quad words */
                     85:
                     86:        stmfd   sp!, {r4-r6}            /* Store registers */
                     87:        mov     r4, r3                  /* Duplicate data */
                     88:        mov     r5, r3
                     89:        mov     r6, r3
                     90:
                     91: Lmemset_loop16:
                     92:        stmia   r0!, {r3-r6}            /* Store 16 bytes */
                     93:        sub     r2, r2, #0x00000010     /* Adjust count */
                     94:        cmp     r2, #0x00000010         /* Still got at least 16 bytes ? */
                     95:        bgt     Lmemset_loop16
                     96:
                     97:        ldmfd   sp!, {r4-r6}            /* Restore registers */
                     98:
                     99:        /* Do we need to set some words as well ? */
                    100:
                    101:        cmp     r2, #0x00000004
                    102:        blt     Lmemset_lessthanfour
                    103:
                    104:        /* Have either less than 16 or less than 32 depending on route taken */
                    105:
                    106: Lmemset_lessthan32:
                    107:
                    108:        /* We have at least 4 bytes so copy as words */
                    109:
                    110: Lmemset_loop4:
                    111:        str     r3, [r0], #0x0004
                    112:        sub     r2, r2, #0x0004
                    113:        cmp     r2, #0x00000004
                    114:        bge     Lmemset_loop4
                    115:
                    116: Lmemset_lessthanfour:
                    117:        cmp     r2, #0x00000000
                    118:        ldmeqfd sp!, {r0}
                    119: #ifdef __APCS_26__
                    120:        moveqs  pc, lr                  /* Zero length so exit */
                    121: #else
                    122:        moveq   pc, lr                  /* Zero length so exit */
                    123: #endif
                    124:
                    125:        cmp     r2, #0x00000002
                    126:        strb    r1, [r0], #0x0001       /* Set 1 byte */
                    127:        strgeb  r1, [r0], #0x0001       /* Set another byte */
                    128:        strgtb  r1, [r0], #0x0001       /* and a third */
                    129:
                    130:        ldmfd   sp!, {r0}
                    131: #ifdef __APCS_26__
                    132:        movs    pc, lr                  /* Exit */
                    133: #else
                    134:        mov     pc, lr                  /* Exit */
                    135: #endif