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/* Optimized strchrnul implementation for PowerPC32/POWER7 using cmpb insn.
Copyright (C) 2010 Free Software Foundation, Inc.
Contributed by Luis Machado <luisgpm@br.ibm.com>.
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, write to the Free
Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA
02110-1301 USA. */
#include <sysdep.h>
#include <bp-sym.h>
#include <bp-asm.h>
/* int [r3] strchrnul (char *s [r3], int c [r4]) */
.machine power7
ENTRY (BP_SYM(__strchrnul))
CALL_MCOUNT
dcbt 0,r3
clrrwi r8,r3,2 /* Align the address to word boundary. */
/* Replicate byte to word. */
rlwimi r4,r4,8,16,23
rlwimi r4,r4,16,0,15
rlwinm r6,r3,3,27,28 /* Calculate padding. */
lwz r12,0(r8) /* Load word from memory. */
li r0,0 /* Word with null chars to use
with cmpb. */
/* Now r4 has a word of c bytes and r0 has
a word of null bytes. */
cmpb r10,r12,r0 /* Compare each byte against c byte. */
cmpb r9,r12,r4 /* Compare each byte against null byte. */
/* Move the words left and right to discard the bits that are
not part of the string and bring them back as zeros. */
slw r10,r10,r6
slw r9,r9,r6
srw r10,r10,r6
srw r9,r9,r6
or r5,r9,r10 /* OR the results to speed things up. */
cmpwi cr7,r5,0 /* If r5 == 0, no c or null bytes
have been found. */
bne cr7,L(done)
mtcrf 0x01,r8
/* Are we now aligned to a quadword boundary? If so, skip to
the main loop. Otherwise, go through the alignment code. */
bt 29,L(loop)
/* Handle WORD2 of pair. */
lwzu r12,4(r8)
cmpb r10,r12,r0
cmpb r9,r12,r4
or r5,r9,r10
cmpwi cr7,r5,0
bne cr7,L(done)
b L(loop) /* We branch here (rather than falling through)
to skip the nops due to heavy alignment
of the loop below. */
.p2align 5
L(loop):
/* Load two words, compare and merge in a
single register for speed. This is an attempt
to speed up the null-checking process for bigger strings. */
lwz r12,4(r8)
lwzu r11,8(r8)
cmpb r10,r12,r0
cmpb r9,r12,r4
cmpb r6,r11,r0
cmpb r7,r11,r4
or r5,r9,r10
or r10,r6,r7
or r11,r5,r10
cmpwi cr7,r11,0
beq cr7,L(loop)
/* OK, one (or both) of the words contains a c/null byte. Check
the first word and decrement the address in case the first
word really contains a c/null byte. */
cmpwi cr6,r5,0
addi r8,r8,-4
bne cr6,L(done)
/* The c/null byte must be in the second word. Adjust the
address again and move the result of cmpb to r10 so we can calculate
the pointer. */
mr r5,r10
addi r8,r8,4
/* r5 has the output of the cmpb instruction, that is, it contains
0xff in the same position as the c/null byte in the original
word from the string. Use that to calculate the pointer. */
L(done):
cntlzw r0,r5 /* Count leading zeros before the match. */
srwi r0,r0,3 /* Convert leading zeros to bytes. */
add r3,r8,r0 /* Return address of matching c/null byte. */
blr
END (BP_SYM (__strchrnul))
weak_alias (__strchrnul,strchrnul)
libc_hidden_builtin_def (__strchrnul)
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