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The current IFUNC selection is always using the most recent features which are available via AT_HWCAP. But in some scenarios it is useful to adjust this selection. The environment variable: GLIBC_TUNABLES=glibc.cpu.hwcaps=-xxx,yyy,zzz,.... can be used to enable HWCAP feature yyy, disable HWCAP feature xxx, where the feature name is case-sensitive and has to match the ones used in sysdeps/loongarch/cpu-tunables.c. Signed-off-by: caiyinyu <caiyinyu@loongson.cn>
88 lines
2.9 KiB
C
88 lines
2.9 KiB
C
/* LoongArch CPU feature tuning.
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This file is part of the GNU C Library.
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Copyright (C) 2024 Free Software Foundation, Inc.
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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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#include <stdbool.h>
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#include <stdint.h>
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#include <unistd.h> /* Get STDOUT_FILENO for _dl_printf. */
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#include <elf/dl-tunables.h>
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#include <string.h>
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#include <cpu-features.h>
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#include <ldsodefs.h>
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#include <sys/auxv.h>
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#include <dl-tunables-parse.h>
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#include <dl-symbol-redir-ifunc.h>
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#define CHECK_GLIBC_IFUNC_CPU(f, name, len) \
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_Static_assert (sizeof (#name) - 1 == len, #name " != " #len); \
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if (tunable_str_comma_strcmp_cte (&f, #name)) \
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{ \
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if (f.disable) \
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GLRO(dl_larch_cpu_features).hwcap &= (~HWCAP_LOONGARCH_##name); \
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else \
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GLRO(dl_larch_cpu_features).hwcap |= HWCAP_LOONGARCH_##name; \
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break; \
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}
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attribute_hidden void
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TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *valp)
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{
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/* The current IFUNC selection is based on microbenchmarks in glibc.
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It should give the best performance for most workloads. But other
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choices may have better performance for a particular workload or on
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the hardware which wasn't available when the selection was made.
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The environment variable:
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GLIBC_TUNABLES=glibc.cpu.hwcaps=-xxx,yyy,-zzz,....
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can be used to enable CPU/ARCH feature yyy, disable CPU/ARCH feature
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yyy and zzz, where the feature name is case-sensitive and has to
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match the ones in cpu-features.h. It can be used by glibc developers
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to tune for a new processor or override the IFUNC selection to
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improve performance for a particular workload.
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NOTE: the IFUNC selection may change over time. Please check all
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multiarch implementations when experimenting. */
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struct tunable_str_comma_state_t ts;
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tunable_str_comma_init (&ts, valp);
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struct tunable_str_comma_t n;
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while (tunable_str_comma_next (&ts, &n))
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{
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switch (n.len)
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{
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default:
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break;
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case 3:
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{
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CHECK_GLIBC_IFUNC_CPU (n, LSX, 3);
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CHECK_GLIBC_IFUNC_CPU (n, UAL, 3);
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}
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break;
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case 4:
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{
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CHECK_GLIBC_IFUNC_CPU (n, LASX, 4);
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}
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break;
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}
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}
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/* Ensure that the user has not enabled any unsupported features. */
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GLRO(dl_larch_cpu_features).hwcap &= GLRO(dl_hwcap);
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}
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