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PowerPC: Program Priority Register support

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This patch add inline functions to change the Program Priority Register
from ISA 2.05.
This commit is contained in:
Adhemerval Zanella 2013-05-24 13:29:30 -05:00
parent e96e37676f
commit d116b7c414
3 changed files with 56 additions and 0 deletions
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6
ChangeLog
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@ -1,3 +1,9 @@
2013-05-24 Adhemerval Zanella <azanella@linux.vnet.ibm.com>
* manual/platform.texi: Add PowerPC PPR function set documentation.
* sysdeps/powerpc/sys/platform/ppc.h: Add PowerPC PPR set function
implementation.
2013-05-24 Carlos O'Donell <carlos@redhat.com>
* math/libm-test.inc (MAX_EXP): Define.

20
manual/platform.texi
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@ -57,4 +57,24 @@ Provide a hint that performance will probably be improved if shared resources
dedicated to the executing processor are released until all outstanding storage
accesses to cacheable storage for which the data is not in the cache have been
completed.
@deftypefun {void} __ppc_set_ppr_med (void)
Set the Program Priority Register to medium value (default).
The @dfn{Program Priority Register} (PPR) is a 64-bit register that controls
the program's priority. By adjusting the PPR value the programmer may
improve system throughput by causing the system resources to be used
more efficiently, especially in contention situations.
The three unprivileged states available are covered by the functions
@code{__ppc_set_ppr_med} (medium -- default), @code{__ppc_set_ppc_low} (low)
and @code{__ppc_set_ppc_med_low} (medium low). More information
available in @cite{Power ISA 2.06b - Book II - Section 3.1}.
@end deftypefun
@deftypefun {void} __ppc_set_ppr_low (void)
Set the Program Priority Register to low value.
@end deftypefun
@deftypefun {void} __ppc_set_ppr_med_low (void)
Set the Program Priority Register to medium low value.
@end deftypefun

30
sysdeps/powerpc/sys/platform/ppc.h
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@ -82,4 +82,34 @@ __ppc_mdoom (void)
__asm__ volatile ("or 30,30,30");
}
/* ISA 2.05 and beyond support the Program Priority Register (PPR) to adjust
thread priorities based on lock acquisition, wait and release. The ISA
defines the use of form 'or Rx,Rx,Rx' as the way to modify the PRI field.
The unprivileged priorities are:
Rx = 1 (low)
Rx = 2 (medium)
Rx = 6 (medium-low/normal)
The 'or' instruction form is a nop in previous hardware, so it is safe to
use unguarded. The default value is 'medium'.
*/
static inline void
__ppc_set_ppr_med (void)
{
__asm__ volatile ("or 2,2,2");
}
static inline void
__ppc_set_ppr_med_low (void)
{
__asm__ volatile ("or 6,6,6");
}
static inline void
__ppc_set_ppr_low (void)
{
__asm__ volatile ("or 1,1,1");
}
#endif /* sys/platform/ppc.h */