src/arch/arm32/include/bits/strings.h

#ifndef _BITS_STRINGS_H
#define _BITS_STRINGS_H

/** @file
 *
 * String functions
 *
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

/**
 * Find first (i.e. least significant) set bit
 *
 * @v value		Value
 * @ret lsb		Least significant bit set in value (LSB=1), or zero
 */
static inline __attribute__ (( always_inline )) int __ffsl ( long value ) {
	unsigned long bits = value;
	unsigned long lsb;
	unsigned int lz;

	/* Extract least significant set bit */
	lsb = ( bits & -bits );

	/* Count number of leading zeroes before LSB */
	__asm__ ( "clz %0, %1" : "=r" ( lz ) : "r" ( lsb ) );

	return ( 32 - lz );
}

/**
 * Find first (i.e. least significant) set bit
 *
 * @v value		Value
 * @ret lsb		Least significant bit set in value (LSB=1), or zero
 */
static inline __attribute__ (( always_inline )) int __ffsll ( long long value ){
	unsigned long high = ( value >> 32 );
	unsigned long low = ( value >> 0 );

	if ( low ) {
		return ( __ffsl ( low ) );
	} else if ( high ) {
		return ( 32 + __ffsl ( high ) );
	} else {
		return 0;
	}
}

/**
 * Find last (i.e. most significant) set bit
 *
 * @v value		Value
 * @ret msb		Most significant bit set in value (LSB=1), or zero
 */
static inline __attribute__ (( always_inline )) int __flsl ( long value ) {
	unsigned int lz;

	/* Count number of leading zeroes */
	__asm__ ( "clz %0, %1" : "=r" ( lz ) : "r" ( value ) );

	return ( 32 - lz );
}

/**
 * Find last (i.e. most significant) set bit
 *
 * @v value		Value
 * @ret msb		Most significant bit set in value (LSB=1), or zero
 */
static inline __attribute__ (( always_inline )) int __flsll ( long long value ){
	unsigned long high = ( value >> 32 );
	unsigned long low = ( value >> 0 );

	if ( high ) {
		return ( 32 + __flsl ( high ) );
	} else if ( low ) {
		return ( __flsl ( low ) );
	} else {
		return 0;
	}
}

#endif /* _BITS_STRINGS_H */