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s390: add optimized array_index_mask_nospec

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Add an optimized version of the array_index_mask_nospec function for
s390 based on a compare and a subtract with borrow.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky 2018-01-26 12:01:55 +01:00
parent 7041d28115
commit e2dd833389
1 changed files with 24 additions and 0 deletions
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24
arch/s390/include/asm/barrier.h
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@ -49,6 +49,30 @@ do { \
#define __smp_mb__before_atomic() barrier()
#define __smp_mb__after_atomic() barrier()
/**
* array_index_mask_nospec - generate a mask for array_idx() that is
* ~0UL when the bounds check succeeds and 0 otherwise
* @index: array element index
* @size: number of elements in array
*/
#define array_index_mask_nospec array_index_mask_nospec
static inline unsigned long array_index_mask_nospec(unsigned long index,
unsigned long size)
{
unsigned long mask;
if (__builtin_constant_p(size) && size > 0) {
asm(" clgr %2,%1\n"
" slbgr %0,%0\n"
:"=d" (mask) : "d" (size-1), "d" (index) :"cc");
return mask;
}
asm(" clgr %1,%2\n"
" slbgr %0,%0\n"
:"=d" (mask) : "d" (size), "d" (index) :"cc");
return ~mask;
}
#include <asm-generic/barrier.h>
#endif /* __ASM_BARRIER_H */