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ppc64: Optimizing bit operation

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Introduce optimized bit operation for PowerPc

Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
This commit is contained in:
Laurent Dufour 2015-05-13 18:45:11 +02:00 • committed by Pavel Emelyanov
parent d28984e80e
commit 61c1936ed9
1 changed files with 166 additions and 3 deletions
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169
arch/ppc64/include/asm/bitops.h
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@ -1,11 +1,174 @@
#ifndef __CR_BITOPS_H__
#define __CR_BITOPS_H__
/*
* PowerPC atomic bit operations.
*
* Merged version by David Gibson <david@gibson.dropbear.id.au>.
* Based on ppc64 versions by: Dave Engebretsen, Todd Inglett, Don
* Reed, Pat McCarthy, Peter Bergner, Anton Blanchard. They
* originally took it from the ppc32 code.
*
* Within a word, bits are numbered LSB first. Lot's of places make
* this assumption by directly testing bits with (val & (1<<nr)).
* This can cause confusion for large (> 1 word) bitmaps on a
* big-endian system because, unlike little endian, the number of each
* bit depends on the word size.
*
* The bitop functions are defined to work on unsigned longs, so for a
* ppc64 system the bits end up numbered:
* |63..............0|127............64|191...........128|255...........192|
* and on ppc32:
* |31.....0|63....32|95....64|127...96|159..128|191..160|223..192|255..224|
*
* There are a few little-endian macros used mostly for filesystem
* bitmaps, these work on similar bit arrays layouts, but
* byte-oriented:
* |7...0|15...8|23...16|31...24|39...32|47...40|55...48|63...56|
*
* The main difference is that bit 3-5 (64b) or 3-4 (32b) in the bit
* number field needs to be reversed compared to the big-endian bit
* fields. This can be achieved by XOR with 0x38 (64b) or 0x18 (32b).
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
* --
* Copied from the kernel file arch/powerpc/include/asm/bitops.h
*/
#include "compiler.h"
#include "asm/bitsperlong.h"
#define DIV_ROUND_UP(n,d) (((n) + (d) - 1) / (d))
#define BITS_TO_LONGS(nr) DIV_ROUND_UP(nr, BITS_PER_LONG)
#define DECLARE_BITMAP(name,bits) \
unsigned long name[BITS_TO_LONGS(bits)]
#define __stringify_in_c(...) #__VA_ARGS__
#define stringify_in_c(...) __stringify_in_c(__VA_ARGS__) " "
#define BIT_MASK(nr) (1UL << ((nr) % BITS_PER_LONG))
#define BIT_WORD(nr) ((nr) / BITS_PER_LONG)
/* PPC bit number conversion */
#define PPC_BITLSHIFT(be) (BITS_PER_LONG - 1 - (be))
#define PPC_BIT(bit) (1UL << PPC_BITLSHIFT(bit))
#define PPC_BITMASK(bs, be) ((PPC_BIT(bs) - PPC_BIT(be)) | PPC_BIT(bs))
/* Macro for generating the ***_bits() functions */
#define DEFINE_BITOP(fn, op) \
static __inline__ void fn(unsigned long mask, \
volatile unsigned long *_p) \
{ \
unsigned long old; \
unsigned long *p = (unsigned long *)_p; \
__asm__ __volatile__ ( \
"1: ldarx %0,0,%3,0\n" \
stringify_in_c(op) "%0,%0,%2\n" \
"stdcx. %0,0,%3\n" \
"bne- 1b\n" \
: "=&r" (old), "+m" (*p) \
: "r" (mask), "r" (p) \
: "cc", "memory"); \
}
DEFINE_BITOP(set_bits, or)
DEFINE_BITOP(clear_bits, andc)
DEFINE_BITOP(change_bits, xor)
static __inline__ void set_bit(int nr, volatile unsigned long *addr)
{
set_bits(BIT_MASK(nr), addr + BIT_WORD(nr));
}
static __inline__ void clear_bit(int nr, volatile unsigned long *addr)
{
clear_bits(BIT_MASK(nr), addr + BIT_WORD(nr));
}
static __inline__ void change_bit(int nr, volatile unsigned long *addr)
{
change_bits(BIT_MASK(nr), addr + BIT_WORD(nr));
}
static inline int test_bit(int nr, const volatile unsigned long *addr)
{
return 1UL & (addr[BIT_WORD(nr)] >> (nr & (BITS_PER_LONG-1)));
}
/*
* TODO: create some optimized version instead of falling down with the
* generic ones.
* Return the zero-based bit position (LE, not IBM bit numbering) of
* the most significant 1-bit in a double word.
*/
#include "asm-generic/bitops.h"
static __inline__ __attribute__((const))
int __ilog2(unsigned long x)
{
int lz;
asm ("cntlzd %0,%1" : "=r" (lz) : "r" (x));
return BITS_PER_LONG - 1 - lz;
}
static __inline__ unsigned long __ffs(unsigned long x)
{
return __ilog2(x & -x);
}
#define BITOP_WORD(nr) ((nr) / BITS_PER_LONG)
/*
* Find the next set bit in a memory region.
*/
static inline
unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
unsigned long offset)
{
const unsigned long *p = addr + BITOP_WORD(offset);
unsigned long result = offset & ~(BITS_PER_LONG-1);
unsigned long tmp;
if (offset >= size)
return size;
size -= result;
offset %= BITS_PER_LONG;
if (offset) {
tmp = *(p++);
tmp &= (~0UL << offset);
if (size < BITS_PER_LONG)
goto found_first;
if (tmp)
goto found_middle;
size -= BITS_PER_LONG;
result += BITS_PER_LONG;
}
while (size & ~(BITS_PER_LONG-1)) {
if ((tmp = *(p++)))
goto found_middle;
result += BITS_PER_LONG;
size -= BITS_PER_LONG;
}
if (!size)
return result;
tmp = *p;
found_first:
tmp &= (~0UL >> (BITS_PER_LONG - size));
if (tmp == 0UL) /* Are any bits set? */
return result + size; /* Nope. */
found_middle:
return result + __ffs(tmp);
}
#define for_each_bit(i, bitmask) \
for (i = find_next_bit(bitmask, sizeof(bitmask), 0); \
i < sizeof(bitmask); \
i = find_next_bit(bitmask, sizeof(bitmask), i + 1))
#endif /* __CR_BITOPS_H__ */