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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.
29 lines
1021 B
Plaintext
29 lines
1021 B
Plaintext
@node Platform, Contributors, Maintenance, Top
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@c %MENU% Describe all platform-specific facilities provided
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@appendix Platform-specific facilities
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@Theglibc{} can provide machine-specific functionality.
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@menu
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* PowerPC:: Facilities Specific to the PowerPC Architecture
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@end menu
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@node PowerPC
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@appendixsec PowerPC-specific Facilities
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Facilities specific to PowerPC that are not specific to a particular
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operating system are declared in @file{sys/platform/ppc.h}.
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@deftypefun {uint64_t} __ppc_get_timebase (void)
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Read the current value of the Time Base Register.
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The @dfn{Time Base Register} is a 64-bit register that stores a monotonically
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incremented value updated at a system-dependent frequency that may be
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different from the processor frequency. More information is available in
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@cite{Power ISA 2.06b - Book II - Section 5.2}.
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@code{__ppc_get_timebase} uses the processor's time base facility directly
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without requiring assistance from the operating system, so it is very
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efficient.
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@end deftypefun
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