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/* Optimized memchr implementation for PowerPC64/POWER7 using cmpb insn.
Copyright (C) 2010-2013 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>
/* int [r3] memchr (char *s [r3], int byte [r4], int size [r5]) */
.machine power7
ENTRY (__memchr)
CALL_MCOUNT 2
dcbt 0,r3
clrrdi r8,r3,3
rlwimi r4,r4,8,16,23
rlwimi r4,r4,16,0,15
add r7,r3,r5 /* Calculate the last acceptable address. */
cmpldi r5,32
insrdi r4,r4,32,0
ble L(small_range)
cmpld cr7,r3,r7 /* Compare the starting address (r3) with the
ending address (r7). If (r3 >= r7),
the size passed in was zero or negative. */
ble cr7,L(proceed)
li r7,-1 /* Artificially set our ending address (r7)
such that we will exit early. */
L(proceed):
rlwinm r6,r3,3,26,28 /* Calculate padding. */
cmpldi cr6,r6,0 /* cr6 == Do we have padding? */
ld r12,0(r8) /* Load doubleword from memory. */
cmpb r10,r12,r4 /* Check for BYTEs in DWORD1. */
beq cr6,L(proceed_no_padding)
sld r10,r10,r6
srd r10,r10,r6
L(proceed_no_padding):
cmpldi cr7,r10,0 /* Does r10 indicate we got a hit? */
bne cr7,L(done)
/* See if we are at the last acceptable address yet. */
addi r9,r8,8
cmpld cr6,r9,r7
bge cr6,L(null)
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 28,L(loop_setup)
/* Handle DWORD2 of pair. */
ldu r12,8(r8)
cmpb r10,r12,r4
cmpldi cr7,r10,0
bne cr7,L(done)
/* Are we done already? */
addi r9,r8,8
cmpld cr6,r9,r7
bge cr6,L(null)
L(loop_setup):
sub r5,r7,r9
srdi r6,r5,4 /* Number of loop iterations. */
mtctr r6 /* Setup the counter. */
b L(loop)
/* Main loop to look for BYTE backwards in the string. Since
it's a small loop (< 8 instructions), align it to 32-bytes. */
.p2align 5
L(loop):
/* Load two doublewords, compare and merge in a
single register for speed. This is an attempt
to speed up the byte-checking process for bigger strings. */
ld r12,8(r8)
ldu r11,16(r8)
cmpb r10,r12,r4
cmpb r9,r11,r4
or r5,r9,r10 /* Merge everything in one doubleword. */
cmpldi cr7,r5,0
bne cr7,L(found)
bdnz L(loop)
/* We're here because the counter reached 0, and that means we
didn't have any matches for BYTE in the whole range. */
subi r11,r7,8
cmpld cr6,r8,r11
blt cr6,L(loop_small)
b L(null)
/* OK, one (or both) of the doublewords contains BYTE. Check
the first doubleword and decrement the address in case the first
doubleword really contains BYTE. */
.align 4
L(found):
cmpldi cr6,r10,0
addi r8,r8,-8
bne cr6,L(done)
/* BYTE must be in the second doubleword. Adjust the address
again and move the result of cmpb to r10 so we can calculate the
pointer. */
mr r10,r9
addi r8,r8,8
/* r10 has the output of the cmpb instruction, that is, it contains
0xff in the same position as BYTE in the original
doubleword from the string. Use that to calculate the pointer.
We need to make sure BYTE is *before* the end of the range. */
L(done):
cntlzd r0,r10 /* Count leading zeroes before the match. */
srdi r0,r0,3 /* Convert leading zeroes to bytes. */
add r3,r8,r0
cmpld r3,r7
bge L(null)
blr
.align 4
L(null):
li r3,0
blr
/* Deals with size <= 32. */
.align 4
L(small_range):
cmpldi r5,0
rlwinm r6,r3,3,26,28 /* Calculate padding. */
beq L(null) /* This branch is for the cmpldi r5,0 above. */
ld r12,0(r8) /* Load word from memory. */
cmpldi cr6,r6,0 /* cr6 == Do we have padding? */
cmpb r10,r12,r4 /* Check for BYTE in DWORD1. */
/* If no padding, skip the shifts. */
beq cr6,L(small_no_padding)
sld r10,r10,r6
srd r10,r10,r6
L(small_no_padding):
cmpldi cr7,r10,0
bne cr7,L(done)
/* Are we done already? */
addi r9,r8,8
cmpld r9,r7
bge L(null)
/* If we're not done, drop through into loop_small. */
L(loop_small): /* loop_small has been unrolled. */
ldu r12,8(r8)
cmpb r10,r12,r4
addi r9,r8,8
cmpldi cr6,r10,0
cmpld r9,r7
bne cr6,L(done) /* Found something. */
bge L(null) /* Hit end of string (length). */
ldu r12,8(r8)
cmpb r10,r12,r4
addi r9,r8,8
cmpldi cr6,r10,0
cmpld r9,r7
bne cr6,L(done) /* Found something. */
bge L(null)
ldu r12,8(r8)
subi r11,r7,8
cmpb r10,r12,r4
cmpldi cr6,r10,0
ori r2,r2,0 /* Force a dispatch group. */
bne cr6,L(done)
cmpld r8,r11 /* At end of range? */
bge L(null)
/* For most cases we will never get here. Under some combinations of
padding + length there is a leftover double that still needs to be
checked. */
ldu r12,8(r8)
cmpb r10,r12,r4
addi r9,r8,8
cmpldi cr6,r10,0
cmpld r9,r7
bne cr6,L(done) /* Found something. */
/* Save a branch and exit directly. */
li r3,0
blr
END (__memchr)
weak_alias (__memchr, memchr)
libc_hidden_builtin_def (memchr)
|
