mirror of
https://github.com/torvalds/linux.git
synced 2024-12-24 11:51:27 +00:00
d0cebfa650
This is an optimization for the PowerPC in 64-bit little-endian. Bit counting is used in find_zero(), instead of the multiply and shift. It is modelled after Alan Modra's PowerPC LE strlen patch http://sourceware.org/ml/libc-alpha/2013-08/msg00097.html. Signed-off-by: Philippe Bergheaud <felix@linux.vnet.ibm.com> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
120 lines
2.8 KiB
C
120 lines
2.8 KiB
C
#ifndef _ASM_WORD_AT_A_TIME_H
|
|
#define _ASM_WORD_AT_A_TIME_H
|
|
|
|
/*
|
|
* Word-at-a-time interfaces for PowerPC.
|
|
*/
|
|
|
|
#include <linux/kernel.h>
|
|
#include <asm/asm-compat.h>
|
|
|
|
#ifdef __BIG_ENDIAN__
|
|
|
|
struct word_at_a_time {
|
|
const unsigned long high_bits, low_bits;
|
|
};
|
|
|
|
#define WORD_AT_A_TIME_CONSTANTS { REPEAT_BYTE(0xfe) + 1, REPEAT_BYTE(0x7f) }
|
|
|
|
/* Bit set in the bytes that have a zero */
|
|
static inline long prep_zero_mask(unsigned long val, unsigned long rhs, const struct word_at_a_time *c)
|
|
{
|
|
unsigned long mask = (val & c->low_bits) + c->low_bits;
|
|
return ~(mask | rhs);
|
|
}
|
|
|
|
#define create_zero_mask(mask) (mask)
|
|
|
|
static inline long find_zero(unsigned long mask)
|
|
{
|
|
long leading_zero_bits;
|
|
|
|
asm (PPC_CNTLZL "%0,%1" : "=r" (leading_zero_bits) : "r" (mask));
|
|
return leading_zero_bits >> 3;
|
|
}
|
|
|
|
static inline bool has_zero(unsigned long val, unsigned long *data, const struct word_at_a_time *c)
|
|
{
|
|
unsigned long rhs = val | c->low_bits;
|
|
*data = rhs;
|
|
return (val + c->high_bits) & ~rhs;
|
|
}
|
|
|
|
#else
|
|
|
|
struct word_at_a_time {
|
|
const unsigned long one_bits, high_bits;
|
|
};
|
|
|
|
#define WORD_AT_A_TIME_CONSTANTS { REPEAT_BYTE(0x01), REPEAT_BYTE(0x80) }
|
|
|
|
#ifdef CONFIG_64BIT
|
|
|
|
/* Alan Modra's little-endian strlen tail for 64-bit */
|
|
#define create_zero_mask(mask) (mask)
|
|
|
|
static inline unsigned long find_zero(unsigned long mask)
|
|
{
|
|
unsigned long leading_zero_bits;
|
|
long trailing_zero_bit_mask;
|
|
|
|
asm ("addi %1,%2,-1\n\t"
|
|
"andc %1,%1,%2\n\t"
|
|
"popcntd %0,%1"
|
|
: "=r" (leading_zero_bits), "=&r" (trailing_zero_bit_mask)
|
|
: "r" (mask));
|
|
return leading_zero_bits >> 3;
|
|
}
|
|
|
|
#else /* 32-bit case */
|
|
|
|
/*
|
|
* This is largely generic for little-endian machines, but the
|
|
* optimal byte mask counting is probably going to be something
|
|
* that is architecture-specific. If you have a reliably fast
|
|
* bit count instruction, that might be better than the multiply
|
|
* and shift, for example.
|
|
*/
|
|
|
|
/* Carl Chatfield / Jan Achrenius G+ version for 32-bit */
|
|
static inline long count_masked_bytes(long mask)
|
|
{
|
|
/* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */
|
|
long a = (0x0ff0001+mask) >> 23;
|
|
/* Fix the 1 for 00 case */
|
|
return a & mask;
|
|
}
|
|
|
|
static inline unsigned long create_zero_mask(unsigned long bits)
|
|
{
|
|
bits = (bits - 1) & ~bits;
|
|
return bits >> 7;
|
|
}
|
|
|
|
static inline unsigned long find_zero(unsigned long mask)
|
|
{
|
|
return count_masked_bytes(mask);
|
|
}
|
|
|
|
#endif
|
|
|
|
/* Return nonzero if it has a zero */
|
|
static inline unsigned long has_zero(unsigned long a, unsigned long *bits, const struct word_at_a_time *c)
|
|
{
|
|
unsigned long mask = ((a - c->one_bits) & ~a) & c->high_bits;
|
|
*bits = mask;
|
|
return mask;
|
|
}
|
|
|
|
static inline unsigned long prep_zero_mask(unsigned long a, unsigned long bits, const struct word_at_a_time *c)
|
|
{
|
|
return bits;
|
|
}
|
|
|
|
/* The mask we created is directly usable as a bytemask */
|
|
#define zero_bytemask(mask) (mask)
|
|
|
|
#endif
|
|
|
|
#endif /* _ASM_WORD_AT_A_TIME_H */
|