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f06a4faf8a
This patch adds an optimized POWER8 st{r,p}ncpy using unaligned accesses.
It shows 10%-80% improvement over the optimized POWER7 one that uses
only aligned accesses, specially on unaligned inputs.
The algorithm first read and check 16 bytes (if inputs do not cross a 4K
page size). The it realign source to 16-bytes and issue a 16 bytes read
and compare loop to speedup null byte checks for large strings. Also,
different from POWER7 optimization, the null pad is done inline in the
implementation using possible unaligned accesses, instead of realying on
a memset call. Special case is added for page cross reads.
39 lines
1.4 KiB
C
39 lines
1.4 KiB
C
/* Multiple versions of strncpy.
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Copyright (C) 2014-2015 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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<http://www.gnu.org/licenses/ >. */
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/* Define multiple versions only for definition in libc. */
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#if IS_IN (libc)
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# include <string.h>
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# include <shlib-compat.h>
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# include "init-arch.h"
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extern __typeof (strncpy) __strncpy_ppc attribute_hidden;
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extern __typeof (strncpy) __strncpy_power7 attribute_hidden;
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extern __typeof (strncpy) __strncpy_power8 attribute_hidden;
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/* Avoid DWARF definition DIE on ifunc symbol so that GDB can handle
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ifunc symbol properly. */
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libc_ifunc (strncpy,
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(hwcap2 & PPC_FEATURE2_ARCH_2_07)
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? __strncpy_power8 :
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(hwcap & PPC_FEATURE_HAS_VSX)
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? __strncpy_power7
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: __strncpy_ppc);
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#endif
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