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2149da3683
The memcpy optimization (commit 587a1290a1) has a series
of mistakes:
- The implementation is wrong: the chunk size calculation is wrong
leading to invalid memory access.
- It adds ifunc supports as default, so --disable-multi-arch does
not work as expected for riscv.
- It mixes Linux files (memcpy ifunc selection which requires the
vDSO/syscall mechanism) with generic support (the memcpy
optimization itself).
- There is no __libc_ifunc_impl_list, which makes testing only
check the selected implementation instead of all supported
by the system.
This patch also simplifies the required bits to enable ifunc: there
is no need to memcopy.h; nor to add Linux-specific files.
The __memcpy_noalignment tail handling now uses a branchless strategy
similar to aarch64 (overlap 32-bits copies for sizes 4..7 and byte
copies for size 1..3).
Checked on riscv64 and riscv32 by explicitly enabling the function
on __libc_ifunc_impl_list on qemu-system.
Changes from v1:
* Implement the memcpy in assembly to correctly handle RISCV
strict-alignment.
Reviewed-by: Evan Green <evan@rivosinc.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
57 lines
2 KiB
C
57 lines
2 KiB
C
/* Multiple versions of memcpy.
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All versions must be listed in ifunc-impl-list.c.
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Copyright (C) 2017-2024 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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#if IS_IN (libc)
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/* Redefine memcpy so that the compiler won't complain about the type
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mismatch with the IFUNC selector in strong_alias, below. */
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# undef memcpy
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# define memcpy __redirect_memcpy
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# include <stdint.h>
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# include <string.h>
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# include <ifunc-init.h>
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# include <riscv-ifunc.h>
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# include <sys/hwprobe.h>
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extern __typeof (__redirect_memcpy) __libc_memcpy;
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extern __typeof (__redirect_memcpy) __memcpy_generic attribute_hidden;
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extern __typeof (__redirect_memcpy) __memcpy_noalignment attribute_hidden;
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static inline __typeof (__redirect_memcpy) *
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select_memcpy_ifunc (uint64_t dl_hwcap, __riscv_hwprobe_t hwprobe_func)
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{
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unsigned long long int v;
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if (__riscv_hwprobe_one (hwprobe_func, RISCV_HWPROBE_KEY_CPUPERF_0, &v) == 0
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&& (v & RISCV_HWPROBE_MISALIGNED_MASK) == RISCV_HWPROBE_MISALIGNED_FAST)
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return __memcpy_noalignment;
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return __memcpy_generic;
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}
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riscv_libc_ifunc (__libc_memcpy, select_memcpy_ifunc);
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# undef memcpy
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strong_alias (__libc_memcpy, memcpy);
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# ifdef SHARED
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__hidden_ver1 (memcpy, __GI_memcpy, __redirect_memcpy)
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__attribute__ ((visibility ("hidden"))) __attribute_copy__ (memcpy);
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# endif
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#else
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# include <string/memcpy.c>
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#endif
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