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#ifndef _BITS_STRINGS_H
#define _BITS_STRINGS_H
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 ) {
long lsb_minus_one;
/* If the input value is zero, the BSF instruction returns
* ZF=0 and leaves an undefined value in the output register.
* Perform this check in C rather than asm so that it can be
* omitted in cases where the compiler is able to prove that
* the input is non-zero.
*/
if ( value ) {
__asm__ ( "bsfl %1, %0"
: "=r" ( lsb_minus_one )
: "rm" ( value ) );
return ( lsb_minus_one + 1 );
} else {
return 0;
}
}
/**
* 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 ) {
long msb_minus_one;
/* If the input value is zero, the BSR instruction returns
* ZF=0 and leaves an undefined value in the output register.
* Perform this check in C rather than asm so that it can be
* omitted in cases where the compiler is able to prove that
* the input is non-zero.
*/
if ( value ) {
__asm__ ( "bsrl %1, %0"
: "=r" ( msb_minus_one )
: "rm" ( value ) );
return ( msb_minus_one + 1 );
} 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 __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 */
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