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/* Optimized strlen implementation for PowerPC64/POWER8 using a vectorized
loop.
Copyright (C) 2016-2025 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>
/* int [r3] strlen (char *s [r3]) */
#ifndef STRLEN
# define STRLEN strlen
#endif
.machine power8
ENTRY_TOCLESS (STRLEN, 4)
CALL_MCOUNT 1
dcbt 0,r3
clrrdi r4,r3,3 /* Align the address to doubleword boundary. */
rlwinm r6,r3,3,26,28 /* Calculate padding. */
li r0,0 /* Doubleword with null chars to use
with cmpb. */
li r5,-1 /* MASK = 0xffffffffffffffff. */
ld r12,0(r4) /* Load doubleword from memory. */
#ifdef __LITTLE_ENDIAN__
sld r5,r5,r6
#else
srd r5,r5,r6 /* MASK = MASK >> padding. */
#endif
orc r9,r12,r5 /* Mask bits that are not part of the string. */
cmpb r10,r9,r0 /* Check for null bytes in DWORD1. */
cmpdi cr7,r10,0 /* If r10 == 0, no null's have been found. */
bne cr7,L(done)
/* For shorter strings (< 64 bytes), we will not use vector registers,
as the overhead isn't worth it. So, let's use GPRs instead. This
will be done the same way as we do in the POWER7 implementation.
Let's see if we are aligned to a quadword boundary. If so, we can
jump to the first (non-vectorized) loop. Otherwise, we have to
handle the next DWORD first. */
mtcrf 0x01,r4
mr r9,r4
addi r9,r9,8
bt 28,L(align64)
/* Handle the next 8 bytes so we are aligned to a quadword
boundary. */
ldu r5,8(r4)
cmpb r10,r5,r0
cmpdi cr7,r10,0
addi r9,r9,8
bne cr7,L(done)
L(align64):
/* Proceed to the old (POWER7) implementation, checking two doublewords
per iteration. For the first 56 bytes, we will just check for null
characters. After that, we will also check if we are 64-byte aligned
so we can jump to the vectorized implementation. We will unroll
these loops to avoid excessive branching. */
ld r6,8(r4)
ldu r5,16(r4)
cmpb r10,r6,r0
cmpb r11,r5,r0
or r5,r10,r11
cmpdi cr7,r5,0
addi r9,r9,16
bne cr7,L(dword_zero)
ld r6,8(r4)
ldu r5,16(r4)
cmpb r10,r6,r0
cmpb r11,r5,r0
or r5,r10,r11
cmpdi cr7,r5,0
addi r9,r9,16
bne cr7,L(dword_zero)
ld r6,8(r4)
ldu r5,16(r4)
cmpb r10,r6,r0
cmpb r11,r5,r0
or r5,r10,r11
cmpdi cr7,r5,0
addi r9,r9,16
bne cr7,L(dword_zero)
/* Are we 64-byte aligned? If so, jump to the vectorized loop.
|
