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30891f35fa
We stopped adding "Contributed by" or similar lines in sources in 2012 in favour of git logs and keeping the Contributors section of the glibc manual up to date. Removing these lines makes the license header a bit more consistent across files and also removes the possibility of error in attribution when license blocks or files are copied across since the contributed-by lines don't actually reflect reality in those cases. Move all "Contributed by" and similar lines (Written by, Test by, etc.) into a new file CONTRIBUTED-BY to retain record of these contributions. These contributors are also mentioned in manual/contrib.texi, so we just maintain this additional record as a courtesy to the earlier developers. The following scripts were used to filter a list of files to edit in place and to clean up the CONTRIBUTED-BY file respectively. These were not added to the glibc sources because they're not expected to be of any use in future given that this is a one time task: https://gist.github.com/siddhesh/b5ecac94eabfd72ed2916d6d8157e7dc https://gist.github.com/siddhesh/15ea1f5e435ace9774f485030695ee02 Reviewed-by: Carlos O'Donell <carlos@redhat.com>
107 lines
3.4 KiB
ArmAsm
107 lines
3.4 KiB
ArmAsm
/* Optimized strlen implementation for PowerPC64/POWER7 using cmpb insn.
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Copyright (C) 2010-2021 Free Software Foundation, Inc.
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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, see
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<https://www.gnu.org/licenses/>. */
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#include <sysdep.h>
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/* int [r3] strlen (char *s [r3]) */
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#ifndef STRLEN
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# define STRLEN strlen
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#endif
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.machine power7
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ENTRY_TOCLESS (STRLEN)
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CALL_MCOUNT 1
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dcbt 0,r3
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clrrdi r4,r3,3 /* Align the address to doubleword boundary. */
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rlwinm r6,r3,3,26,28 /* Calculate padding. */
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li r0,0 /* Doubleword with null chars to use
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with cmpb. */
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li r5,-1 /* MASK = 0xffffffffffffffff. */
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ld r12,0(r4) /* Load doubleword from memory. */
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#ifdef __LITTLE_ENDIAN__
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sld r5,r5,r6
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#else
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srd r5,r5,r6 /* MASK = MASK >> padding. */
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#endif
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orc r9,r12,r5 /* Mask bits that are not part of the string. */
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cmpb r10,r9,r0 /* Check for null bytes in DWORD1. */
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cmpdi cr7,r10,0 /* If r10 == 0, no null's have been found. */
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bne cr7,L(done)
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mtcrf 0x01,r4
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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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bt 28,L(loop)
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/* Handle DWORD2 of pair. */
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ldu r12,8(r4)
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cmpb r10,r12,r0
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cmpdi cr7,r10,0
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bne cr7,L(done)
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/* Main loop to look for the end of the string. Since it's a
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small loop (< 8 instructions), align it to 32-bytes. */
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.p2align 5
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L(loop):
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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 null-checking process for bigger strings. */
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ld r12, 8(r4)
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ldu r11, 16(r4)
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cmpb r10,r12,r0
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cmpb r9,r11,r0
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or r8,r9,r10 /* Merge everything in one doubleword. */
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cmpdi cr7,r8,0
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beq cr7,L(loop)
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/* OK, one (or both) of the doublewords contains a null byte. Check
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the first doubleword and decrement the address in case the first
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doubleword really contains a null byte. */
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cmpdi cr6,r10,0
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addi r4,r4,-8
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bne cr6,L(done)
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/* The null 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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length. */
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mr r10,r9
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addi r4,r4,8
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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 the null byte in the original
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doubleword from the string. Use that to calculate the length. */
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L(done):
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#ifdef __LITTLE_ENDIAN__
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addi r9, r10, -1 /* Form a mask from trailing zeros. */
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andc r9, r9, r10
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popcntd r0, r9 /* Count the bits in the mask. */
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#else
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cntlzd r0,r10 /* Count leading zeros before the match. */
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#endif
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subf r5,r3,r4
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srdi r0,r0,3 /* Convert leading/trailing zeros to bytes. */
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add r3,r5,r0 /* Compute final length. */
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blr
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END (STRLEN)
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libc_hidden_builtin_def (strlen)
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