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/* Optimized memcpy implementation for PowerPC64.
Copyright (C) 2003-2025 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <sysdep.h>
/* void * [r3] memcpy (void *dst [r3], void *src [r4], size_t len [r5]);
Returns 'dst'.
Memcpy handles short copies (< 32-bytes) using a binary move blocks
(no loops) of lwz/stw. The tail (remaining 1-3) bytes is handled
with the appropriate combination of byte and halfword load/stores.
There is minimal effort to optimize the alignment of short moves.
The 64-bit implementations of POWER3 and POWER4 do a reasonable job
of handling unaligned load/stores that do not cross 32-byte boundaries.
Longer moves (>= 32-bytes) justify the effort to get at least the
destination doubleword (8-byte) aligned. Further optimization is
possible when both source and destination are doubleword aligned.
Each case has a optimized unrolled loop. */
#ifndef MEMCPY
# define MEMCPY memcpy
#endif
ENTRY_TOCLESS (MEMCPY, 5)
CALL_MCOUNT 3
cmpldi cr1,5,31
neg 0,3
std 3,-16(1)
std 31,-8(1)
cfi_offset(31,-8)
andi. 11,3,7 /* check alignment of dst. */
clrldi 0,0,61 /* Number of bytes until the 1st doubleword of dst. */
clrldi 10,4,61 /* check alignment of src. */
cmpldi cr6,5,8
ble- cr1,.L2 /* If move < 32 bytes use short move code. */
cmpld cr6,10,11
mr 12,4
srdi 9,5,3 /* Number of full double words remaining. */
mtcrf 0x01,0
mr 31,5
beq .L0
subf 31,0,5
/* Move 0-7 bytes as needed to get the destination doubleword aligned. */
1: bf 31,2f
lbz 6,0(12)
addi 12,12,1
stb 6,0(3)
addi 3,3,1
2: bf 30,4f
lhz 6,0(12)
addi 12,12,2
sth 6,0(3)
addi 3,3,2
4: bf 29,0f
lwz 6,0(12)
addi 12,12,4
stw 6,0(3)
addi 3,3,4
0:
clrldi 10,12,61 /* check alignment of src again. */
srdi 9,31,3 /* Number of full double words remaining. */
/* Copy doublewords from source to destination, assuming the
destination is aligned on a doubleword boundary.
At this point we know there are at least 25 bytes left (32-7) to copy.
The next step is to determine if the source is also doubleword aligned.
If not branch to the unaligned move code at .L6. which uses
a load, shift, store strategy.
Otherwise source and destination are doubleword aligned, and we can
the optimized doubleword copy loop. */
.L0:
clrldi 11,31,61
mtcrf 0x01,9
bne- cr6,.L6 /* If source is not DW aligned. */
/* Move doublewords where destination and source are DW aligned.
Use a unrolled loop to copy 4 doubleword (32-bytes) per iteration.
If the copy is not an exact multiple of 32 bytes, 1-3
doublewords are copied as needed to set up the main loop. After
the main loop exits there may be a tail of 1-7 bytes. These byte are
copied a word/halfword/byte at a time as needed to preserve alignment. */
srdi 8,31,5
cmpldi cr1,9,4
cmpldi cr6,11,0
mr 11,12
bf 30,1f
ld 6,0(12)
ld 7,8(12)
addi 11,12,16
mtctr 8
std 6,0(3)
std 7,8(3)
addi 10,3,16
bf 31,4f
ld 0,16(12)
std 0,16(3)
blt cr1,3f
addi 11,12,24
addi 10,3,24
b 4f
.align 4
1:
mr 10,3
mtctr 8
bf 31,4f
ld 6,0(12)
addi 11,12,8
std 6,0(3)
addi 10,3,8
.align 4
4:
ld 6,0(11)
ld 7,8(11)
ld 8,16(11)
ld 0,24(11)
addi 11,11,32
2:
std 6,0(10)
std 7,8(10)
std 8,16(10)
std 0,24(10)
addi 10,10,32
bdnz 4b
3:
rldicr 0,31,0,60
mtcrf 0x01,31
beq cr6,0f
.L9:
add 3,3,0
add 12,12,0
/* At this point we have a tail of 0-7 bytes and we know that the
destination is double word aligned. */
4: bf 29,2f
lwz 6,0(12)
addi 12,12,4
stw 6,0(3)
addi 3,3,4
2: bf 30,1f
lhz 6,0(12)
addi 12,12,2
sth 6,0(3)
addi 3,3,2
1: bf 31,0f
lbz 6,0(12)
stb 6,0(3)
0:
/* Return original dst pointer. */
ld 31,-8(1)
ld 3,-16(1)
blr
/* Copy up to 31 bytes. This divided into two cases 0-8 bytes and 9-31
bytes. Each case is handled without loops, using binary (1,2,4,8)
tests.
In the short (0-8 byte) case no attempt is made to force alignment
of either source or destination. The hardware will handle the
unaligned load/stores with small delays for crossing 32- 64-byte, and
4096-byte boundaries. Since these short moves are unlikely to be
unaligned or cross these boundaries, the overhead to force
alignment is not justified.
The longer (9-31 byte) move is more likely to cross 32- or 64-byte
boundaries. Since only loads are sensitive to the 32-/64-byte
boundaries it is more important to align the source then the
destination. If the source is not already word aligned, we first
move 1-3 bytes as needed. Since we are only word aligned we don't
use double word load/stores to insure that all loads are aligned.
While the destination and stores may still be unaligned, this
is only an issue for page (4096 byte boundary) crossing, which
should be rare for these short moves. The hardware handles this
case automatically with a small delay. */
.align 4
.L2:
mtcrf 0x01,5
neg 8,4
clrrdi 11,4,2
andi. 0,8,3
ble cr6,.LE8 /* Handle moves of 0-8 bytes. */
/* At least 9 bytes left. Get the source word aligned. */
cmpldi cr1,5,16
mr 10,5
mr 12,4
cmpldi cr6,0,2
beq .L3 /* If the source is already word aligned skip this. */
/* Copy 1-3 bytes to get source address word aligned. */
lwz 6,0(11)
subf 10,0,5
add 12,4,0
blt cr6,5f
srdi 7,6,16
bgt cr6,3f
#ifdef __LITTLE_ENDIAN__
sth 7,0(3)
#else
sth 6,0(3)
#endif
b 7f
.align 4
3:
#ifdef __LITTLE_ENDIAN__
rotlwi 6,6,24
stb 6,0(3)
sth 7,1(3)
#else
stb 7,0(3)
sth 6,1(3)
#endif
b 7f
.align 4
5:
#ifdef __LITTLE_ENDIAN__
rotlwi 6,6,8
#endif
stb 6,0(3)
7:
cmpldi cr1,10,16
add 3,3,0
mtcrf 0x01,10
.align 4
.L3:
/* At least 6 bytes left and the source is word aligned. */
blt cr1,8f
16: /* Move 16 bytes. */
lwz 6,0(12)
lwz 7,4(12)
stw 6,0(3)
lwz 6,8(12)
stw 7,4(3)
lwz 7,12(12)
addi 12,12,16
stw 6,8(3)
stw 7,12(3)
addi 3,3,16
8: /* Move 8 bytes. */
bf 28,4f
lwz 6,0(12)
lwz 7,4(12)
addi 12,12,8
stw 6,0(3)
stw 7,4(3)
addi 3,3,8
4: /* Move 4 bytes. */
bf 29,2f
lwz 6,0(12)
addi 12,12,4
stw 6,0(3)
addi 3,3,4
2: /* Move 2-3 bytes. */
bf 30,1f
lhz 6,0(12)
sth 6,0(3)
bf 31,0f
lbz 7,2(12)
stb 7,2(3)
ld 3,-16(1)
blr
1: /* Move 1 byte. */
bf 31,0f
lbz 6,0(12)
stb 6,0(3)
0:
/* Return original dst pointer. */
ld 3,-16(1)
blr
/* Special case to copy 0-8 bytes. */
.align 4
.LE8:
mr 12,4
bne cr6,4f
/* Would have liked to use use ld/std here but the 630 processors are
slow for load/store doubles that are not at least word aligned.
Unaligned Load/Store word execute with only a 1 cycle penalty. */
lwz 6,0(4)
lwz 7,4(4)
stw 6,0(3)
stw 7,4(3)
/* Return original dst pointer. */
ld 3,-16(1)
blr
.align 4
4: bf 29,2b
lwz 6,0(4)
stw 6,0(3)
6:
bf 30,5f
lhz 7,4(4)
sth 7,4(3)
bf 31,0f
lbz 8,6(4)
stb 8,6(3)
ld 3,-16(1)
blr
.align 4
5:
bf 31,0f
lbz 6,4(4)
stb 6,4(3)
.align 4
0:
/* Return original dst pointer. */
ld 3,-16(1)
blr
.align 4
.L6:
/* Copy doublewords where the destination is aligned but the source is
not. Use aligned doubleword loads from the source, shifted to realign
the data, to allow aligned destination stores. */
subf 5,10,12
andi. 0,9,1
cmpldi cr6,11,0
sldi 10,10,3
mr 11,9
mr 4,3
ld 6,0(5)
ld 7,8(5)
subfic 9,10,64
beq 2f
#ifdef __LITTLE_ENDIAN__
srd 0,6,10
#else
sld 0,6,10
#endif
cmpldi 11,1
mr 6,7
addi 4,4,-8
addi 11,11,-1
b 1f
2: addi 5,5,8
.align 4
#ifdef __LITTLE_ENDIAN__
0: srd 0,6,10
sld 8,7,9
#else
0: sld 0,6,10
srd 8,7,9
#endif
cmpldi 11,2
ld 6,8(5)
or 0,0,8
addi 11,11,-2
std 0,0(4)
#ifdef __LITTLE_ENDIAN__
srd 0,7,10
1: sld 8,6,9
#else
sld 0,7,10
1: srd 8,6,9
#endif
or 0,0,8
beq 8f
ld 7,16(5)
std 0,8(4)
addi 5,5,16
addi 4,4,16
b 0b
.align 4
8:
std 0,8(4)
rldicr 0,31,0,60
mtcrf 0x01,31
bne cr6,.L9 /* If the tail is 0 bytes we are done! */
/* Return original dst pointer. */
ld 31,-8(1)
ld 3,-16(1)
blr
END_GEN_TB (MEMCPY,TB_TOCLESS)
libc_hidden_builtin_def (memcpy)
|
