/*

 * Written by J.T. Conklin <jtc@netbsd.org>.

 * Adapted for use as log2 by Ulrich Drepper <drepper@cygnus.com>.

 * Public domain.

 *

 * Changed to use fyl2xp1 for values near 1, <drepper@cygnus.com>.

 * Adapted for x86-64 by Andreas Jaeger <aj@suse.de>.

 */

#include <machine/asm.h>

	.section .rodata.cst8,"aM",@progbits,8

	.p2align 3

	.type one,@object

one:	.double 1.0

	ASM_SIZE_DIRECTIVE(one)

	/* It is not important that this constant is precise.  It is only

	   a value which is known to be on the safe side for using the

	   fyl2xp1 instruction.  */

	.type limit,@object

limit:	.double 0.29

	ASM_SIZE_DIRECTIVE(limit)

#ifdef PIC

# define MO(op) op##(%rip)

#else

# define MO(op) op

#endif

	.text

ENTRY(__ieee754_log2l)

	fldl	MO(one)

	fldt	8(%rsp)		// x : 1

	fxam

	fnstsw

	fld	%st		// x : x : 1

	testb	$1, %ah

	jnz	3f		// in case x is NaN or ±Inf

4:	fsub	%st(2), %st	// x-1 : x : 1

	fld	%st		// x-1 : x-1 : x : 1

	fabs			// |x-1| : x-1 : x : 1

	fcompl	MO(limit)	// x-1 : x : 1

	fnstsw			// x-1 : x : 1

	andb	$0x45, %ah

	jz	2f

	fxam

	fnstsw

	andb	$0x45, %ah

	cmpb	$0x40, %ah

	jne	5f

	fabs			// log2(1) is +0 in all rounding modes.

5:	fstp	%st(1)		// x-1 : 1

	fyl2xp1			// log(x)

	ret

2:	fstp	%st(0)		// x : 1

	fyl2x			// log(x)

	ret

3:	testb	$4, %ah

	jnz	4b		// in case x is ±Inf

	fstp	%st(1)

	fstp	%st(1)

	fadd	%st(0)

	ret

END (__ieee754_log2l)

ENTRY(__log2l_finite)

	fldl	MO(one)

	fldt	8(%rsp)		// x : 1

	fld	%st		// x : x : 1

	fsub	%st(2), %st	// x-1 : x : 1

	fld	%st		// x-1 : x-1 : x : 1

	fabs			// |x-1| : x-1 : x : 1

	fcompl	MO(limit)	// x-1 : x : 1

	fnstsw			// x-1 : x : 1

	andb	$0x45, %ah

	jz	2b

	fxam

	fnstsw

	andb	$0x45, %ah

	cmpb	$0x40, %ah

	jne	6f

	fabs			// log2(1) is +0 in all rounding modes.

6:	fstp	%st(1)		// x-1 : 1

	fyl2xp1			// log(x)

	ret

END (__log2l_finite)