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- Committer: Michael Hope
- Date: 2010-08-26 22:19:29 UTC
- Revision ID: michael.hope@linaro.org-20100826221929-ppeg01mnpx34aqrp
Pulled in the initial versions
- files added:
- src
- src/reference
- src/reference/bionic
- src/reference/glibc
- src/reference/helpers
- src/reference/newlib
- src/reference/plain
added
removed
src/reference/bionic/memcmp.S
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/*
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* Copyright (C) 2008 The Android Open Source Project
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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 without
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* modification, are permitted provided that the following conditions
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* are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <machine/cpu-features.h>
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.text
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.global memcmp
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.type memcmp, %function
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.align 4
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/*
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* Optimized memcmp() for ARM9.
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* This would not be optimal on XScale or ARM11, where more prefetching
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* and use of PLD will be needed.
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* The 2 major optimzations here are
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* (1) The main loop compares 16 bytes at a time
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* (2) The loads are scheduled in a way they won't stall
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*/
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memcmp:
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.fnstart
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PLD (r0, #0)
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PLD (r1, #0)
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/* take of the case where length is 0 or the buffers are the same */
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cmp r0, r1
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cmpne r2, #0
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moveq r0, #0
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bxeq lr
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.save {r4, lr}
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/* save registers */
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stmfd sp!, {r4, lr}
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PLD (r0, #32)
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PLD (r1, #32)
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/* since r0 hold the result, move the first source
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* pointer somewhere else
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*/
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mov r4, r0
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/* make sure we have at least 8+4 bytes, this simplify things below
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* and avoid some overhead for small blocks
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*/
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cmp r2, #(8+4)
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bmi 8f
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/* align first pointer to word boundary
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* offset = -src & 3
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*/
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rsb r3, r4, #0
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ands r3, r3, #3
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beq 0f
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/* align first pointer */
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sub r2, r2, r3
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1: ldrb r0, [r4], #1
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ldrb ip, [r1], #1
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subs r0, r0, ip
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bne 9f
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subs r3, r3, #1
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bne 1b
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0: /* here the first pointer is aligned, and we have at least 4 bytes
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* to process.
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*/
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/* see if the pointers are congruent */
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eor r0, r4, r1
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ands r0, r0, #3
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bne 5f
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/* congruent case, 32 bytes per iteration
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* We need to make sure there are at least 32+4 bytes left
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* because we effectively read ahead one word, and we could
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* read past the buffer (and segfault) if we're not careful.
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*/
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ldr ip, [r1]
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subs r2, r2, #(32 + 4)
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bmi 1f
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0: PLD (r4, #64)
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PLD (r1, #64)
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ldr r0, [r4], #4
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ldr lr, [r1, #4]!
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eors r0, r0, ip
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ldreq r0, [r4], #4
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ldreq ip, [r1, #4]!
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eoreqs r0, r0, lr
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ldreq r0, [r4], #4
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ldreq lr, [r1, #4]!
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eoreqs r0, r0, ip
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ldreq r0, [r4], #4
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ldreq ip, [r1, #4]!
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eoreqs r0, r0, lr
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ldreq r0, [r4], #4
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ldreq lr, [r1, #4]!
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eoreqs r0, r0, ip
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ldreq r0, [r4], #4
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ldreq ip, [r1, #4]!
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eoreqs r0, r0, lr
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ldreq r0, [r4], #4
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ldreq lr, [r1, #4]!
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eoreqs r0, r0, ip
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ldreq r0, [r4], #4
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ldreq ip, [r1, #4]!
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eoreqs r0, r0, lr
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bne 2f
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subs r2, r2, #32
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bhs 0b
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/* do we have at least 4 bytes left? */
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1: adds r2, r2, #(32 - 4 + 4)
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bmi 4f
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/* finish off 4 bytes at a time */
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3: ldr r0, [r4], #4
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ldr ip, [r1], #4
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eors r0, r0, ip
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bne 2f
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subs r2, r2, #4
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bhs 3b
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/* are we done? */
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4: adds r2, r2, #4
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moveq r0, #0
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beq 9f
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/* finish off the remaining bytes */
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b 8f
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2: /* the last 4 bytes are different, restart them */
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sub r4, r4, #4
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sub r1, r1, #4
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mov r2, #4
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/* process the last few bytes */
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8: ldrb r0, [r4], #1
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ldrb ip, [r1], #1
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// stall
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subs r0, r0, ip
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bne 9f
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subs r2, r2, #1
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bne 8b
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9: /* restore registers and return */
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ldmfd sp!, {r4, lr}
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bx lr
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.fnend
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5: /*************** non-congruent case ***************/
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and r0, r1, #3
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cmp r0, #2
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bne 4f
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/* here, offset is 2 (16-bits aligned, special cased) */
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/* make sure we have at least 16 bytes to process */
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subs r2, r2, #16
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addmi r2, r2, #16
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bmi 8b
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/* align the unaligned pointer */
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bic r1, r1, #3
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ldr lr, [r1], #4
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6: PLD (r1, #64)
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PLD (r4, #64)
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mov ip, lr, lsr #16
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ldr lr, [r1], #4
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ldr r0, [r4], #4
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orr ip, ip, lr, lsl #16
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eors r0, r0, ip
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moveq ip, lr, lsr #16
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ldreq lr, [r1], #4
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ldreq r0, [r4], #4
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orreq ip, ip, lr, lsl #16
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eoreqs r0, r0, ip
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moveq ip, lr, lsr #16
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ldreq lr, [r1], #4
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ldreq r0, [r4], #4
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orreq ip, ip, lr, lsl #16
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eoreqs r0, r0, ip
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moveq ip, lr, lsr #16
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ldreq lr, [r1], #4
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ldreq r0, [r4], #4
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orreq ip, ip, lr, lsl #16
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eoreqs r0, r0, ip
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bne 7f
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subs r2, r2, #16
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bhs 6b
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sub r1, r1, #2
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/* are we done? */
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adds r2, r2, #16
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moveq r0, #0
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beq 9b
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/* finish off the remaining bytes */
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b 8b
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7: /* fix up the 2 pointers and fallthrough... */
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sub r1, r1, #(4+2)
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sub r4, r4, #4
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mov r2, #4
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b 8b
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4: /*************** offset is 1 or 3 (less optimized) ***************/
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stmfd sp!, {r5, r6, r7}
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// r5 = rhs
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// r6 = lhs
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// r7 = scratch
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mov r5, r0, lsl #3 /* r5 = right shift */
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rsb r6, r5, #32 /* r6 = left shift */
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/* align the unaligned pointer */
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bic r1, r1, #3
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ldr r7, [r1], #4
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sub r2, r2, #8
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6: mov ip, r7, lsr r5
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ldr r7, [r1], #4
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ldr r0, [r4], #4
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orr ip, ip, r7, lsl r6
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eors r0, r0, ip
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moveq ip, r7, lsr r5
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ldreq r7, [r1], #4
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ldreq r0, [r4], #4
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orreq ip, ip, r7, lsl r6
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eoreqs r0, r0, ip
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bne 7f
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subs r2, r2, #8
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bhs 6b
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sub r1, r1, r6, lsr #3
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ldmfd sp!, {r5, r6, r7}
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/* are we done? */
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adds r2, r2, #8
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moveq r0, #0
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beq 9b
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/* finish off the remaining bytes */
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b 8b
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7: /* fix up the 2 pointers and fallthrough... */
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sub r1, r1, #4
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sub r1, r1, r6, lsr #3
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sub r4, r4, #4
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mov r2, #4
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ldmfd sp!, {r5, r6, r7}
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b 8b
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