+++ /dev/null
-/*
- * Copyright (c) 2009 Apple Inc. All rights reserved.
- *
- * @APPLE_LICENSE_HEADER_START@
- *
- * This file contains Original Code and/or Modifications of Original Code
- * as defined in and that are subject to the Apple Public Source License
- * Version 2.0 (the 'License'). You may not use this file except in
- * compliance with the License. Please obtain a copy of the License at
- * http://www.opensource.apple.com/apsl/ and read it before using this
- * file.
- *
- * The Original Code and all software distributed under the License are
- * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
- * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
- * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
- * Please see the License for the specific language governing rights and
- * limitations under the License.
- *
- * @APPLE_LICENSE_HEADER_END@
- */
-
-// ARM Assembly implementation of memcmp( ) from <string.h>
-// Uses Thumb2 if it is available, otherwise generates ARM code.
-//
-// -- Stephen Canon, August 2009
-//
-// The basic idea is to use word compares instead of byte compares as long as
-// at least four bytes remain to be compared. However, because memcmp( )
-// compares the buffers as though they were big-endian unsigned integers, we
-// need to byte-reverse each word before comparing them.
-//
-// If the buffers are not word aligned, or they are shorter than four bytes,
-// we just use a simple byte comparison loop instead.
-//
-// int bcmp(void *src1, void *src2, size_t length);
-// int memcmp(void *src1, void *src2, size_t length);
-
-.text
-.syntax unified
-#if defined __thumb2__
- .code 16
- .thumb_func _bcmp
- .thumb_func _memcmp
-#else
- .code 32
-#endif
-
-#define ESTABLISH_FRAME \
- push {r7,lr};\
- mov r7, sp
-#define CLEAR_FRAME_AND_RETURN \
- pop {r7,pc}
-
-#include <arm/arch.h>
-
-#if defined _ARM_ARCH_6
- #define BYTE_REVERSE(reg,tmp) \
- rev reg, reg
-#else // defined _ARM_ARCH_6
-// Prior to ARMv6, the REV instruction is not available. We use a very cute
-// software workaround instead, which needs only a single scratch register.
- #define BYTE_REVERSE(reg,tmp) \
- eor tmp, reg, reg, ror #16;\
- bic tmp, tmp, #0xff0000 ;\
- mov tmp, tmp, lsr #8 ;\
- eor reg, tmp, reg, ror #8
-#endif // defined _ARM_ARCH_6
-
-.globl _bcmp
-.globl _memcmp
-.align 2
-_bcmp:
-_memcmp:
- // If both buffers are not word aligned, jump to a byte-comparison loop.
- ESTABLISH_FRAME
- orr ip, r0, r1
- tst ip, #3
- bne L_useByteComparisons
-
- // As long as at least four bytes of length remain, load one word from each
- // buffer and check if they are equal.
-0: subs r2, #4
- blo L_lessThanFourBytesRemain
- ldr r3, [r0],#4
- ldr ip, [r1],#4
- cmp r3, ip
- beq 0b
-
- // If words from the two buffers compared unequal, we end up here. We need
- // to byte-swap both words, then subtract to determine the result (+/-1).
- BYTE_REVERSE(r3,r1)
- BYTE_REVERSE(ip,r2)
- mov r0, #1
- subs r3, ip
- it lo
- movlo r0, #-1
- CLEAR_FRAME_AND_RETURN
-
-L_lessThanFourBytesRemain:
- adds r2, #4
-L_useByteComparisons:
- mov r3, r0
- // If no bytes remain to compare, the buffers are equal and we return zero.
- // Otherwise, load one byte from each buffer and check if they are equal.
-0: subs r2, #1
- blo L_buffersAreEqual
- ldrb r0, [r3],#1
- ldrb ip, [r1],#1
- subs r0, ip
- beq 0b
- CLEAR_FRAME_AND_RETURN
-
-L_buffersAreEqual:
- mov r0, #0
- CLEAR_FRAME_AND_RETURN
projects / apple / libc.git / blobdiff