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/* Optimized memchr implementation for PowerPC64/POWER7 using cmpb insn.
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Copyright (C) 2010 Free Software Foundation, Inc.
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Contributed by Luis Machado <luisgpm@br.ibm.com>.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, write to the Free
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Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA
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/* int [r3] memchr (char *s [r3], int byte [r4], int size [r5]) */
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ENTRY (BP_SYM (__memchr))
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add r7,r3,r5 /* Calculate the last acceptable address. */
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cmpld cr7,r3,r7 /* Is the address equal or less than r3? If
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it's equal or less, it means size is either 0
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or a negative number. */
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li r7,-1 /* Make r11 the biggest if r4 <= 0. */
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rlwinm r6,r3,3,26,28 /* Calculate padding. */
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ld r12,0(r8) /* Load doubleword from memory. */
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cmpb r10,r12,r4 /* Check for BYTE's in DWORD1. */
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cmpldi cr7,r10,0 /* If r10 == 0, no BYTE's's have been found. */
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/* Are we done already? */
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/* Are we now aligned to a quadword boundary? If so, skip to
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the main loop. Otherwise, go through the alignment code. */
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/* Handle DWORD2 of pair. */
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/* Are we done already? */
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srdi r6,r5,4 /* Number of loop iterations. */
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mtctr r6 /* Setup the counter. */
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/* Main loop to look for BYTE backwards in the string. Since
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it's a small loop (< 8 instructions), align it to 32-bytes. */
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/* Load two doublewords, compare and merge in a
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single register for speed. This is an attempt
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to speed up the byte-checking process for bigger strings. */
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or r5,r9,r10 /* Merge everything in one doubleword. */
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/* We're here because the counter reached 0, and that means we
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didn't have any matches for BYTE in the whole range. Just return
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the original range. */
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blt cr6,L(loop_small)
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/* OK, one (or both) of the doublewords contains BYTE. Check
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the first doubleword and decrement the address in case the first
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doubleword really contains BYTE. */
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/* BYTE must be in the second doubleword. Adjust the address
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again and move the result of cmpb to r10 so we can calculate the
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/* r10 has the output of the cmpb instruction, that is, it contains
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0xff in the same position as BYTE in the original
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doubleword from the string. Use that to calculate the pointer.
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We need to make sure BYTE is *before* the end of the
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cntlzd r0,r10 /* Count leading zeroes before the match. */
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srdi r0,r0,3 /* Convert leading zeroes to bytes. */
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/* Deals with size <= 32. */
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rlwinm r6,r3,3,26,28 /* Calculate padding. */
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ld r12,0(r8) /* Load word from memory. */
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cmpb r10,r12,r4 /* Check for BYTE in DWORD1. */
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/* Are we done already? */
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END (BP_SYM (__memchr))
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weak_alias (BP_SYM (__memchr), BP_SYM(memchr))
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libc_hidden_builtin_def (memchr)