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/* Optimized rawmemchr 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, see
<http://www.gnu.org/licenses/>. */
#include <sysdep.h>
#include <bp-sym.h>
#include <bp-asm.h>
/* int [r3] rawmemchr (void *s [r3], int c [r4]) */
.machine power7
ENTRY (BP_SYM(__rawmemchr))
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
/* Now r4 has a word of c bytes. */
rlwinm r6,r3,3,27,28 /* Calculate padding. */
lwz r12,0(r8) /* Load word from memory. */
cmpb r5,r12,r4 /* Compare each byte against c byte. */
slw r5,r5,r6 /* Move left to discard ignored bits. */
srw r5,r5,r6 /* Bring the bits back as zeros. */
cmpwi cr7,r5,0 /* If r5 == 0, no c bytes have been found. */
bne cr7,L(done)
mtcrf 0x01,r8
/* Are we now aligned to a doubleword 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 r5,r12,r4
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. */
/* Main loop to look for the end of the string. Since it's a
small loop (< 8 instructions), align it to 32-bytes. */
.p2align 5
L(loop):
/* Load two words, compare and merge in a
single register for speed. This is an attempt
to speed up the byte-checking process for bigger strings. */
lwz r12,4(r8)
lwzu r11,8(r8)
cmpb r5,r12,r4
cmpb r6,r11,r4
or r7,r5,r6
cmpwi cr7,r7,0
beq cr7,L(loop)
/* OK, one (or both) of the words contains a 'c' byte. Check
the first word and decrement the address in case the first
word really contains a c byte. */
cmpwi cr6,r5,0
addi r8,r8,-4
bne cr6,L(done)
/* The 'c' 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,r6
addi r8,r8,4
/* r5 has the output of the cmpb instruction, that is, it contains
0xff in the same position as the 'c' byte in the original
word from the string. Use that fact to find out what is
the position of the byte inside the string. */
L(done):
cntlzw r0,r5 /* Count leading zeros before the match. */
srwi r0,r0,3 /* Convert leading zeroes to bytes. */
add r3,r8,r0 /* Return address of the matching char. */
blr
END (BP_SYM (__rawmemchr))
weak_alias (__rawmemchr,rawmemchr)
libc_hidden_builtin_def (__rawmemchr)
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