/*
* Copyright (C) 2008 The Android Open Source Project
* 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.
*
* 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.
*/
/*
* Optimized memcpy() for ARM.
*
* note that memcpy() always returns the destination pointer,
* so we have to preserve R0.
*/
/*
* This file has been modified from the original for use in musl libc.
* The main changes are: addition of .type memcpy,%function to make the
* code safely callable from thumb mode, adjusting the return
* instructions to be compatible with pre-thumb ARM cpus, and removal
* of prefetch code that is not compatible with older cpus.
*/
.global memcpy
.type memcpy,%function
memcpy:
/* The stack must always be 64-bits aligned to be compliant with the
* ARM ABI. Since we have to save R0, we might as well save R4
* which we can use for better pipelining of the reads below
*/
.fnstart
.save {r0, r4, lr}
stmfd sp!, {r0, r4, lr}
/* Making room for r5-r11 which will be spilled later */
.pad #28
sub sp, sp, #28
/* it simplifies things to take care of len<4 early */
cmp r2, #4
blo copy_last_3_and_return
/* compute the offset to align the source
* offset = (4-(src&3))&3 = -src & 3
*/
rsb r3, r1, #0
ands r3, r3, #3
beq src_aligned
/* align source to 32 bits. We need to insert 2 instructions between
* a ldr[b|h] and str[b|h] because byte and half-word instructions
* stall 2 cycles.
*/
movs r12, r3, lsl #31
sub r2, r2, r3 /* we know that r3 <= r2 because r2 >= 4 */
ldrmib r3, [r1], #1
ldrcsb r4, [r1], #1
ldrcsb r12,[r1], #1
strmib r3, [r0], #1
strcsb r4, [r0], #1
strcsb r12,[r0], #1
src_aligned:
/* see if src and dst are aligned together (congruent) */
eor r12, r0, r1
tst r12, #3
bne non_congruent
/* Use post-incriment mode for stm to spill r5-r11 to reserved stack
* frame. Don't update sp.
*/
stmea sp, {r5-r11}
/* align the destination to a cache-line */
rsb r3, r0, #0
ands r3, r3, #0x1C
beq congruent_aligned32
cmp r3, r2
andhi r3, r2, #0x1C
/* conditionnaly copies 0 to 7 words (length in r3) */
movs r12, r3, lsl #28
ldmcsia r1!, {r4, r5, r6, r7} /* 16 bytes */
ldmmiia r1!, {r8, r9} /* 8 bytes */
stmcsia r0!, {r4, r5, r6, r7}
stmmiia r0!, {r8, r9}
tst r3, #0x4
ldrne r10,[r1], #4 /* 4 bytes */
strne r10,[r0], #4
sub r2, r2, r3
congruent_aligned32:
/*
* here source is aligned to 32 bytes.
*/
cached_aligned32:
subs r2, r2, #32
blo less_than_32_left
/*
* We preload a cache-line up to 64 bytes ahead. On the 926, this will
* stall only until the requested world is fetched, but the linefill
* continues in the the background.
* While the linefill is going, we write our previous cache-line
* into the write-buffer (which should have some free space).
* When the linefill is done, the writebuffer will
* start dumping its content into memory
*
* While all this is going, we then load a full cache line into
* 8 registers, this cache line should be in the cache by now
* (or partly in the cache).
*
* This code should work well regardless of the source/dest alignment.
*
*/
/* Align the preload register to a cache-line because the cpu does
* "critical word first" (the first word requested is loaded first).
*/
@ bic r12, r1, #0x1F
@ add r12, r12, #64
1: ldmia r1!, { r4-r11 }
subs r2, r2, #32
/*
* NOTE: if r12 is more than 64 ahead of r1, the following ldrhi
* for ARM9 preload will not be safely guarded by the preceding subs.
* When it is safely guarded the only possibility to have SIGSEGV here
* is because the caller overstates the length.
*/
@ ldrhi r3, [r12], #32 /* cheap ARM9 preload */
stmia r0!, { r4-r11 }
bhs 1b
add r2, r2, #32
less_than_32_left:
/*
* less than 32 bytes left at this point (length in r2)
*/
/* skip all this if there is nothing to do, which should
* be a common case (if not executed the code below takes
* about 16 cycles)
*/
tst r2, #0x1F
beq 1f
/* conditionnaly copies 0 to 31 bytes */
movs r12, r2, lsl #28
ldmcsia r1!, {r4, r5, r6, r7} /* 16 bytes */
ldmmiia r1!, {r8, r9} /* 8 bytes */
stmcsia r0!, {r4, r5, r6, r7}
stmmiia r0!, {r8, r9}
movs r12, r2, lsl #30
ldrcs r3, [r1], #4 /* 4 bytes */
ldrmih r4, [r1], #2 /* 2 bytes */
strcs r3, [r0], #4
strmih r4, [r0], #2
tst r2, #0x1
ldrneb r3, [r1] /* last byte */
strneb r3, [r0]
/* we're done! restore everything and return */
1: ldmfd sp!, {r5-r11}
ldmfd sp!, {r0, r4, lr}
tst lr, #1
moveq pc, lr
bx lr
/********************************************************************/
non_congruent:
/*
* here source is aligned to 4 bytes
* but destination is not.
*
* in the code below r2 is the number of bytes read
* (the number of bytes written is always smaller, because we have
* partial words in the shift queue)
*/
cmp r2, #4
blo copy_last_3_and_return
/* Use post-incriment mode for stm to spill r5-r11 to reserved stack
* frame. Don't update sp.
*/
stmea sp, {r5-r11}
/* compute shifts needed to align src to dest */
rsb r5, r0, #0
and r5, r5, #3 /* r5 = # bytes in partial words */
mov r12, r5, lsl #3 /* r12 = right */
rsb lr, r12, #32 /* lr = left */
/* read the first word */
ldr r3, [r1], #4
sub r2, r2, #4
/* write a partial word (0 to 3 bytes), such that destination
* becomes aligned to 32 bits (r5 = nb of words to copy for alignment)
*/
movs r5, r5, lsl #31
strmib r3, [r0], #1
movmi r3, r3, lsr #8
strcsb r3, [r0], #1
movcs r3, r3, lsr #8
strcsb r3, [r0], #1
movcs r3, r3, lsr #8
cmp r2, #4
blo partial_word_tail
/* Align destination to 32 bytes (cache line boundary) */
1: tst r0, #0x1c
beq 2f
ldr r5, [r1], #4
sub r2, r2, #4
orr r4, r3, r5, lsl lr
mov r3, r5, lsr r12
str r4, [r0], #4
cmp r2, #4
bhs 1b
blo partial_word_tail
/* copy 32 bytes at a time */
2: subs r2, r2, #32
blo less_than_thirtytwo
/* Use immediate mode for the shifts, because there is an extra cycle
* for register shifts, which could account for up to 50% of
* performance hit.
*/
cmp r12, #24
beq loop24
cmp r12, #8
beq loop8
loop16:
ldr r12, [r1], #4
1: mov r4, r12
ldmia r1!, { r5,r6,r7, r8,r9,r10,r11}
subs r2, r2, #32
ldrhs r12, [r1], #4
orr r3, r3, r4, lsl #16
mov r4, r4, lsr #16
orr r4, r4, r5, lsl #16
mov r5, r5, lsr #16
orr r5, r5, r6, lsl #16
mov r6, r6, lsr #16
orr r6, r6, r7, lsl #16
mov r7, r7, lsr #16
orr r7, r7, r8, lsl #16
mov r8, r8, lsr #16
orr r8, r8, r9, lsl #16
mov r9, r9, lsr #16
orr r9, r9, r10, lsl #16
mov r10, r10, lsr #16
orr r10, r10, r11, lsl #16
stmia r0!, {r3,r4,r5,r6, r7,r8,r9,r10}
mov r3, r11, lsr #16
bhs 1b
b less_than_thirtytwo
loop8:
ldr r12, [r1], #4
1: mov r4, r12
ldmia r1!, { r5,r6,r7, r8,r9,r10,r11}
subs r2, r2, #32
ldrhs r12, [r1], #4
orr r3, r3, r4, lsl #24
mov r4, r4, lsr #8
orr r4, r4, r5, lsl #24
mov r5, r5, lsr #8
orr r5, r5, r6, lsl #24
mov r6, r6, lsr #8
orr r6, r6, r7, lsl #24
mov r7, r7, lsr #8
orr r7, r7, r8, lsl #24
mov r8, r8, lsr #8
orr r8, r8, r9, lsl #24
mov r9, r9, lsr #8
orr r9, r9, r10, lsl #24
mov r10, r10, lsr #8
orr r10, r10, r11, lsl #24
stmia r0!, {r3,r4,r5,r6, r7,r8,r9,r10}
mov r3, r11, lsr #8
bhs 1b
b less_than_thirtytwo
loop24:
ldr r12, [r1], #4
1: mov r4, r12
ldmia r1!, { r5,r6,r7, r8,r9,r10,r11}
subs r2, r2, #32
ldrhs r12, [r1], #4
orr r3, r3, r4, lsl #8
mov r4, r4, lsr #24
orr r4, r4, r5, lsl #8
mov r5, r5, lsr #24
orr r5, r5, r6, lsl #8
mov r6, r6, lsr #24
orr r6, r6, r7, lsl #8
mov r7, r7, lsr #24
orr r7, r7, r8, lsl #8
mov r8, r8, lsr #24
orr r8, r8, r9, lsl #8
mov r9, r9, lsr #24
orr r9, r9, r10, lsl #8
mov r10, r10, lsr #24
orr r10, r10, r11, lsl #8
stmia r0!, {r3,r4,r5,r6, r7,r8,r9,r10}
mov r3, r11, lsr #24
bhs 1b
less_than_thirtytwo:
/* copy the last 0 to 31 bytes of the source */
rsb r12, lr, #32 /* we corrupted r12, recompute it */
add r2, r2, #32
cmp r2, #4
blo partial_word_tail
1: ldr r5, [r1], #4
sub r2, r2, #4
orr r4, r3, r5, lsl lr
mov r3, r5, lsr r12
str r4, [r0], #4
cmp r2, #4
bhs 1b
partial_word_tail:
/* we have a partial word in the input buffer */
movs r5, lr, lsl #(31-3)
strmib r3, [r0], #1
movmi r3, r3, lsr #8
strcsb r3, [r0], #1
movcs r3, r3, lsr #8
strcsb r3, [r0], #1
/* Refill spilled registers from the stack. Don't update sp. */
ldmfd sp, {r5-r11}
copy_last_3_and_return:
movs r2, r2, lsl #31 /* copy remaining 0, 1, 2 or 3 bytes */
ldrmib r2, [r1], #1
ldrcsb r3, [r1], #1
ldrcsb r12,[r1]
strmib r2, [r0], #1
strcsb r3, [r0], #1
strcsb r12,[r0]
/* we're done! restore sp and spilled registers and return */
add sp, sp, #28
ldmfd sp!, {r0, r4, lr}
tst lr, #1
moveq pc, lr
bx lr
