arch/alpha/include/asm/word-at-a-time.h

Source file repositories/reference/linux-study-clean/arch/alpha/include/asm/word-at-a-time.h

File Facts

System
Linux kernel
Corpus path
arch/alpha/include/asm/word-at-a-time.h
Extension
.h
Size
1376 bytes
Lines
59
Domain
Architecture Layer
Bucket
arch/alpha
Inferred role
Architecture Layer: implementation source
Status
source implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

struct word_at_a_time {
	const unsigned long unused;
};

#define WORD_AT_A_TIME_CONSTANTS { 0 }

/* Return nonzero if val has a zero */
static inline unsigned long has_zero(unsigned long val, unsigned long *bits, const struct word_at_a_time *c)
{
	unsigned long zero_locations = __kernel_cmpbge(0, val);
	*bits = zero_locations;
	return zero_locations;
}

static inline unsigned long prep_zero_mask(unsigned long val, unsigned long bits, const struct word_at_a_time *c)
{
	return bits;
}

#define create_zero_mask(bits) (bits)

static inline unsigned long find_zero(unsigned long bits)
{
#if defined(CONFIG_ALPHA_EV6) && defined(CONFIG_ALPHA_EV67)
	/* Simple if have CIX instructions */
	return __kernel_cttz(bits);
#else
	unsigned long t1, t2, t3;
	/* Retain lowest set bit only */
	bits &= -bits;
	/* Binary search for lowest set bit */
	t1 = bits & 0xf0;
	t2 = bits & 0xcc;
	t3 = bits & 0xaa;
	if (t1) t1 = 4;
	if (t2) t2 = 2;
	if (t3) t3 = 1;
	return t1 + t2 + t3;
#endif
}

#define zero_bytemask(mask) ((2ul << (find_zero(mask) * 8)) - 1)

#endif /* _ASM_WORD_AT_A_TIME_H */

Annotation

Implementation Notes