271 lines
7.3 KiB
ArmAsm
271 lines
7.3 KiB
ArmAsm
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/* $NetBSD: memcmp.S,v 1.3 2011/01/15 07:31:12 matt Exp $ */
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/* stropt/memcmp.S, pl_string_common, pl_linux 10/11/04 11:45:35
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* ==========================================================================
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* Optimized memcmp implementation for IBM PowerPC 405/440.
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*
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* Copyright (c) 2003, IBM Corporation
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or
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* without modification, are permitted provided that the following
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* conditions are met:
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*
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* * Redistributions of source code must retain the above
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* copyright notice, this list of conditions and the following
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* disclaimer.
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* * Redistributions in binary form must reproduce the above
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* copyright notice, this list of conditions and the following
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* disclaimer in the documentation and/or other materials
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* provided with the distribution.
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* * Neither the name of IBM nor the names of its contributors
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* may be used to endorse or promote products derived from this
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* software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
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* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
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* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
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* OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
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* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
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* USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* ==========================================================================
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*
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* Function: Compare two character strings (up to n characters)
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*
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* int memcmp(const char *s1, const char *s2, int n)
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*
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* Input: r3 - buffer 1 address
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* r4 - buffer 2 address
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* r5 - maximum characters to compare
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* Output: r3 <0 (less), 0 (equal), >0 (greater)
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*
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* ==========================================================================
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*/
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#include <machine/asm.h>
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.text
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.align 4
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/* LINTSTUB: Func: void *memcmp(const void *, const void *, size_t) */
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ENTRY(memcmp)
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/*
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* Check count passed in R5. If zero, return 0; otherwise continue.
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*/
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cmpwi %r5,0
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beq- ret_0;
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/*
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* Most of the time the difference is found in the first
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* several bytes. The following code minimizes the number
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* of load operations for short compares.
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*/
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mr %r11, %r3 /* Save buffer 1 */
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again:
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not %r10, %r4 /* buffer 2: bytes to page bdy */
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rlwinm. %r10, %r10,29,23,31 /* buffer 2: dwords to page bdy */
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beq- bytebybyte /* If < 8 bytes to the page bdy */
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/* do byte by byte */
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lwz %r8, 0(%r4) /* load 1st buffer 2 word */
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not %r12, %r11 /* buffer 1: bytes to page bdy */
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rlwinm. %r12, %r12,29,23,31 /* buffer 1: dwords to page bdy */
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beq- bytebybyte /* If < 8 bytes to the page bdy */
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/* do byte by byte */
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lwz %r6, 0(%r11) /* load 1st buffer 1 word */
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cmpwi %r5, 4 /* If remaining count <= 4 */
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ble+ first4 /* handle specially. DWG */
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cmplw %r8, %r6 /* compare buffer 2 and buffer 1*/
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bne+ all_done /* different => we're done */
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lwzu %r9, 4(%r4) /* load 2nd buffer 2 word */
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lwzu %r7, 4(%r11) /* load 2nd buffer 1 word */
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cmpwi %r5, 8 /* If remaining count <= 8 */
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ble+ last4 /* handle specially. DWG */
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cmplw %r9, %r7 /* compare buffer 2 and buffer 1*/
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bne+ all_done /* different => we're done */
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addi %r5, %r5, -8 /* Update character counter DWG */
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addi %r10, %r4, 0x0004 /* DWG*/
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not %r10, %r10 /* buffer 2: bytes to page bdy DWG */
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rlwinm. %r10, %r10,29,23,31 /* buffer 2: dwords to page bdy DWG */
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addi %r12, %r11, 0x0004 /* DWG */
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not %r12, %r12 /* buffer 1: bytes to page bdy DWG */
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rlwinm. %r12, %r12,29,23,31 /* buffer 1: dwords to page bdy DWG */
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/* The following section prior to loop: figures out whether */
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/* the buffer 1 or buffer 2 is closer to the page boundary. */
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/* The main loop count is then set up to reflect the number of */
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/* double words of the buffer that is closest */
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cmpw %r10, %r12 /* Find closest */
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blt lt
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mr %r10, %r12
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lt:
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srwi %r12, %r5, 3 /* Double check the total count */
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cmpw %r10, %r12 /* limitation */
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blt lt2
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mr %r10, %r12 /* DWG */
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lt2: /* DWG */
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cmpwi %r10, 0 /* DWG */
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bne lt3 /* DWG */
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addi %r4, %r4, 0x0004 /* DWG */
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addi %r11,%r11,0x0004 /* DWG */
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b again /* DWG */
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lt3: /* DWG */
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mtctr %r10 /* dword count for loop */
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lwzu %r6, 4(%r11) /* pre-load buffer 1 word */
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b in /* To the loop */
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loop: /* main loop */
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cmplw %r8, %r6 /* Compare first buffer 2 word */
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bne- all_done /* with first buffer 1 word */
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/* If different, we're done */
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cmplw %r9, %r7 /* Compare second buffer 2 word */
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/* with second buffer 1 word */
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lwzu %r6, 4(%r11) /* pre-load buffer 1 word */
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bne- all_done /* If different, we're done */
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in:
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lwzu %r7, 4(%r11) /* pre-load buffer 1 word */
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lwzu %r8, 4(%r4) /* pre-load buffer 2 word */
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lwzu %r9, 4(%r4) /* pre-load buffer 2 word */
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bdnz+ loop /* Do more DW's if cnt > 0 */
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/*mfctr %r12*/ /*DWG*/ /* number of dwords left */
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/*subf %r10, %r12, %r10*/ /*DWG*//* number of dwords compared */
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slwi %r10, %r10, 3
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subf %r5, %r10, %r5 /* adjust byte counter */
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/*bne+ partial*/ /*DWG*/ /* If less than 8 bytes, handle */
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/* specially */
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/*cmpwi %r5, 8*/ /* Removed. DWG */
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/*blt partial*/ /* Removed. DWG */
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/*addic %r5, %r5, -8*/ /*DWG*/ /* Subtract two words from count*/
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cmplw %r8, %r6 /* compare last dword */
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addi %r4, %r4, 4
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bne- all_done
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cmplw %r9, %r7
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addi %r11, %r11, 4
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bne- all_done
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bytebybyte:
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/* We've gotten close to a page boundary: do a byte-byte-byte
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* compare for the following 8 bytes, and then go back to
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* the full-word compare loop.
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*/
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li %r3, 8 /* loop count */
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cmpw %r3, %r5 /* take min(8, counter) */
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ble f2
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mr. %r3, %r5
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beqlr
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f2:
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mtctr %r3
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subf %r5, %r3, %r5 /* adjust counter */
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bbb:
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lbz %r6, 0(%r11) /* byte copy loop */
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addi %r11, %r11, 1
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lbz %r8, 0(%r4)
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addi %r4, %r4, 1
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cmplw %r8, %r6
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bdnzt+ eq, bbb
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bne all_done
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cmpwi %r5, 0
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bgt again /* handle the rest */
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xor %r3,%r3,%r3
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blr
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#if 0 /* Removed code section. DWG */
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partial:
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mr. %r3, %r5
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beqlr /* If count -> 0, we're done */
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f1:
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subfic %r3, %r3, 4 /* zero/end in first word? */
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cmpwi %r3, 0
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blt last4
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#endif /* DWG */
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first4:
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subfic %r3, %r5, 4 /* If count <= 4, handle */
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rlwinm %r3, %r3, 3, 0, 31 /* count *= 8 */
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srw %r6, %r6, %r3 /* align 1st buffer 1 word */
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srw %r8, %r8, %r3 /* align 1st buffer 2 word */
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cmplw %r8, %r6 /* get result */
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bne all_done
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xor %r3,%r3,%r3
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blr
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last4:
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subfic %r10, %r5, 8 /*DWG*/
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rlwinm %r10, %r10, 3, 0, 31 /* count *= 8 */
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srw %r7, %r7, %r10 /* align 2nd buffer 1 word */
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srw %r9, %r9, %r10 /* align 2nd buffer 2 word */
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cmplw %r9, %r7 /* get result */
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bne all_done
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ret_0:
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xor %r3,%r3,%r3 /* Equal result */
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blr
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all_done:
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blt finish_lt
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addi %r3,0,-1 /* Less than result */
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blr
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finish_lt:
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addi %r3,0,1 /* Greater than result */
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blr
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END(memcmp)
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