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2149da3683
The memcpy optimization (commit 587a1290a1af7bee6db) 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>
44 lines
1.5 KiB
C
44 lines
1.5 KiB
C
/* Enumerate available IFUNC implementations of a function. RISCV version.
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Copyright (C) 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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#include <ifunc-impl-list.h>
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#include <string.h>
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#include <sys/hwprobe.h>
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size_t
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__libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
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size_t max)
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{
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size_t i = max;
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bool fast_unaligned = false;
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struct riscv_hwprobe pair = { .key = RISCV_HWPROBE_KEY_CPUPERF_0 };
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if (__riscv_hwprobe (&pair, 1, 0, NULL, 0) == 0
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&& (pair.value & RISCV_HWPROBE_MISALIGNED_MASK)
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== RISCV_HWPROBE_MISALIGNED_FAST)
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fast_unaligned = true;
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IFUNC_IMPL (i, name, memcpy,
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IFUNC_IMPL_ADD (array, i, memcpy, fast_unaligned,
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__memcpy_noalignment)
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IFUNC_IMPL_ADD (array, i, memcpy, 1, __memcpy_generic))
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return 0;
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}
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