function rsqrtf( x ) {
	return float64ToFloat32( 1.0 / sqrt( float64ToFloat32( x ) ) );
}
Compute the reciprocal square root of a single-precision floating-point number.

@param {number} x - input value
@returns {number} reciprocal square root

@example
var v = rsqrtf( 4.0 );
// returns 0.5

@example
var v = rsqrtf( 0.0 );
// returns Infinity

@example
var v = rsqrtf( Infinity );
// returns 0.0

@example
var v = rsqrtf( -4.0 );
// returns NaN

@example
var v = rsqrtf( NaN );
// returns NaN