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[BZ #13743] A new class of installed headers has been documented for low-level platform-specific functionality. PowerPC added the first instance with a function to provide time base register access (__ppc_get_timebase). This is required for applications that measure time at high frequencies with high precision that can't afford a syscall.
48 lines
1.5 KiB
C
48 lines
1.5 KiB
C
/* Facilities specific to the PowerPC architecture
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Copyright (C) 2012 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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#ifndef _SYS_PLATFORM_PPC_H
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#define _SYS_PLATFORM_PPC_H 1
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#include <stdint.h>
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/* Read the Time Base Register. */
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static inline uint64_t
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__ppc_get_timebase (void)
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{
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#ifdef __powerpc64__
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uint64_t __tb;
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/* "volatile" is necessary here, because the user expects this assembly
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isn't moved after an optimization. */
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__asm__ volatile ("mfspr %0, 268" : "=r" (__tb));
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return __tb;
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#else /* not __powerpc64__ */
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uint32_t __tbu, __tbl, __tmp; \
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__asm__ volatile ("0:\n\t"
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"mftbu %0\n\t"
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"mftbl %1\n\t"
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"mftbu %2\n\t"
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"cmpw %0, %2\n\t"
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"bne- 0b"
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: "=r" (__tbu), "=r" (__tbl), "=r" (__tmp));
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return (((uint64_t) __tbu << 32) | __tbl);
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#endif /* not __powerpc64__ */
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}
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#endif /* sys/platform/ppc.h */
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