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/* $NetBSD: memcmp.S,v 1.4 2013/07/04 20:57:59 matt Exp $ */
/* stropt/memcmp.S, pl_string_common, pl_linux 10/11/04 11:45:35
* ==========================================================================
* Optimized memcmp implementation for IBM PowerPC 405/440.
*
* Copyright (c) 2003, IBM Corporation
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or
* without modification, are permitted provided that the following
* conditions are met:
*
* * Redistributions of source code must retain the above
* copyright notice, this list of conditions and the following
* disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials
* provided with the distribution.
* * Neither the name of IBM nor the names of its contributors
* may be used to endorse or promote products derived from this
* software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
* OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
* USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* ==========================================================================
*
* Function: Compare two character strings (up to n characters)
*
* int memcmp(const char *s1, const char *s2, int n)
*
* Input: r3 - buffer 1 address
* r4 - buffer 2 address
* r5 - maximum characters to compare
* Output: r3 <0 (less), 0 (equal), >0 (greater)
*
* ==========================================================================
*/
#include <machine/asm.h>
.text
.align 4
/* LINTSTUB: Func: void *memcmp(const void *, const void *, size_t) */
ENTRY(memcmp)
/*
* Check count passed in R5. If zero, return 0; otherwise continue.
*/
cmpwi %r5,0
beq- ret_0;
/*
* Most of the time the difference is found in the first
* several bytes. The following code minimizes the number
* of load operations for short compares.
*/
mr %r11, %r3 /* Save buffer 1 */
again:
not %r10, %r4 /* buffer 2: bytes to page bdy */
rlwinm. %r10, %r10,29,23,31 /* buffer 2: dwords to page bdy */
beq- bytebybyte /* If < 8 bytes to the page bdy */
/* do byte by byte */
lwz %r8, 0(%r4) /* load 1st buffer 2 word */
not %r12, %r11 /* buffer 1: bytes to page bdy */
rlwinm. %r12, %r12,29,23,31 /* buffer 1: dwords to page bdy */
beq- bytebybyte /* If < 8 bytes to the page bdy */
/* do byte by byte */
lwz %r6, 0(%r11) /* load 1st buffer 1 word */
cmpwi %r5, 4 /* If remaining count <= 4 */
ble+ first4 /* handle specially. DWG */
cmplw %r8, %r6 /* compare buffer 2 and buffer 1*/
bne+ all_done /* different => we're done */
lwzu %r9, 4(%r4) /* load 2nd buffer 2 word */
lwzu %r7, 4(%r11) /* load 2nd buffer 1 word */
cmpwi %r5, 8 /* If remaining count <= 8 */
ble+ last4 /* handle specially. DWG */
cmplw %r9, %r7 /* compare buffer 2 and buffer 1*/
bne+ all_done /* different => we're done */
addi %r5, %r5, -8 /* Update character counter DWG */
addi %r10, %r4, 0x0004 /* DWG*/
not %r10, %r10 /* buffer 2: bytes to page bdy DWG */
rlwinm. %r10, %r10,29,23,31 /* buffer 2: dwords to page bdy DWG */
addi %r12, %r11, 0x0004 /* DWG */
not %r12, %r12 /* buffer 1: bytes to page bdy DWG */
rlwinm. %r12, %r12,29,23,31 /* buffer 1: dwords to page bdy DWG */
/* The following section prior to loop: figures out whether */
/* the buffer 1 or buffer 2 is closer to the page boundary. */
/* The main loop count is then set up to reflect the number of */
/* double words of the buffer that is closest */
cmpw %r10, %r12 /* Find closest */
blt lt
mr %r10, %r12
lt:
srwi %r12, %r5, 3 /* Double check the total count */
cmpw %r10, %r12 /* limitation */
blt lt2
mr %r10, %r12 /* DWG */
lt2: /* DWG */
cmpwi %r10, 0 /* DWG */
bne lt3 /* DWG */
addi %r4, %r4, 0x0004 /* DWG */
addi %r11,%r11,0x0004 /* DWG */
b again /* DWG */
lt3: /* DWG */
mtctr %r10 /* dword count for loop */
lwzu %r6, 4(%r11) /* pre-load buffer 1 word */
b in /* To the loop */
loop: /* main loop */
cmplw %r8, %r6 /* Compare first buffer 2 word */
bne- all_done /* with first buffer 1 word */
/* If different, we're done */
cmplw %r9, %r7 /* Compare second buffer 2 word */
/* with second buffer 1 word */
lwzu %r6, 4(%r11) /* pre-load buffer 1 word */
bne- all_done /* If different, we're done */
in:
lwzu %r7, 4(%r11) /* pre-load buffer 1 word */
lwzu %r8, 4(%r4) /* pre-load buffer 2 word */
lwzu %r9, 4(%r4) /* pre-load buffer 2 word */
bdnz+ loop /* Do more DW's if cnt > 0 */
/*mfctr %r12*/ /*DWG*/ /* number of dwords left */
/*subf %r10, %r12, %r10*/ /*DWG*//* number of dwords compared */
slwi %r10, %r10, 3
subf %r5, %r10, %r5 /* adjust byte counter */
/*bne+ partial*/ /*DWG*/ /* If less than 8 bytes, handle */
/* specially */
/*cmpwi %r5, 8*/ /* Removed. DWG */
/*blt partial*/ /* Removed. DWG */
/*addic %r5, %r5, -8*/ /*DWG*/ /* Subtract two words from count*/
cmplw %r8, %r6 /* compare last dword */
addi %r4, %r4, 4
bne- all_done
cmplw %r9, %r7
addi %r11, %r11, 4
bne- all_done
bytebybyte:
/* We've gotten close to a page boundary: do a byte-byte-byte
* compare for the following 8 bytes, and then go back to
* the full-word compare loop.
*/
li %r3, 8 /* loop count */
cmpw %r3, %r5 /* take min(8, counter) */
ble f2
mr. %r3, %r5
beqlr
f2:
mtctr %r3
subf %r5, %r3, %r5 /* adjust counter */
bbb:
lbz %r6, 0(%r11) /* byte copy loop */
addi %r11, %r11, 1
lbz %r8, 0(%r4)
addi %r4, %r4, 1
cmplw %r8, %r6
bdnzt eq, bbb
bne all_done
cmpwi %r5, 0
bgt again /* handle the rest */
xor %r3,%r3,%r3
blr
#if 0 /* Removed code section. DWG */
partial:
mr. %r3, %r5
beqlr /* If count -> 0, we're done */
f1:
subfic %r3, %r3, 4 /* zero/end in first word? */
cmpwi %r3, 0
blt last4
#endif /* DWG */
first4:
subfic %r3, %r5, 4 /* If count <= 4, handle */
rlwinm %r3, %r3, 3, 0, 31 /* count *= 8 */
srw %r6, %r6, %r3 /* align 1st buffer 1 word */
srw %r8, %r8, %r3 /* align 1st buffer 2 word */
cmplw %r8, %r6 /* get result */
bne all_done
xor %r3,%r3,%r3
blr
last4:
subfic %r10, %r5, 8 /*DWG*/
rlwinm %r10, %r10, 3, 0, 31 /* count *= 8 */
srw %r7, %r7, %r10 /* align 2nd buffer 1 word */
srw %r9, %r9, %r10 /* align 2nd buffer 2 word */
cmplw %r9, %r7 /* get result */
bne all_done
ret_0:
xor %r3,%r3,%r3 /* Equal result */
blr
all_done:
blt finish_lt
addi %r3,0,-1 /* Less than result */
blr
finish_lt:
addi %r3,0,1 /* Greater than result */
blr
END(memcmp)
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