NetBSD/lib/libm/arch/i387/e_exp.S

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

#include <machine/asm.h>

RCSID("$NetBSD: e_exp.S,v 1.7 1996/07/03 17:31:28 jtc Exp $")

/* e^x = 2^(x * log2(e)) */
ENTRY(__ieee754_exp)
	pushl	%ebp
	movl	%esp,%ebp
	subl	$8,%esp

	fstcw	-12(%ebp)		/* store fpu control word */
	movw	-12(%ebp),%dx
	orw	$0x0180,%dx
	movw	%dx,-16(%ebp)
	fldcw	-16(%ebp)		/* load modfied control word */

	fldl	8(%ebp)
	fldl2e
	fmulp				/* x * log2(e) */
	fstl	%st(1)
	frndint				/* int(x * log2(e)) */
	fxch	%st(1)
	fsub	%st(1),%st		/* fract(x * log2(e)) */
	f2xm1				/* 2^(fract(x * log2(e))) - 1 */ 
	fld1
	faddp				/* 2^(fract(x * log2(e))) */
	fscale				/* e^x */
	fstpl	%st(1)

	fldcw	-12(%ebp)		/* restore original control word */

	leave
	ret
FPU specific math code. 1994-02-11 21:20:17 +03:00			`/*`
Winning Strategies has placed this code into the Public Domain 1995-04-29 02:43:31 +04:00			`* Written by J.T. Conklin <jtc@netbsd.org>.`
			`* Public domain.`
FPU specific math code. 1994-02-11 21:20:17 +03:00			`*/`

			`#include <machine/asm.h>`

use one less fp stack slot 1996-07-03 21:31:28 +04:00			`RCSID("$NetBSD: e_exp.S,v 1.7 1996/07/03 17:31:28 jtc Exp $")`
Added RCS ID's. ID's use new RCSID macro from <machine/asm.h>. 1994-03-12 04:30:22 +03:00
FPU specific math code. 1994-02-11 21:20:17 +03:00			`/* e^x = 2^(x * log2(e)) */`
			`ENTRY(__ieee754_exp)`
It's necessary to use 64 bit precision to avoid errors in the least significant bit(s) (for some operands). 1996-07-03 21:27:34 +04:00			`pushl %ebp`
			`movl %esp,%ebp`
			`subl $8,%esp`

			`fstcw -12(%ebp) /* store fpu control word */`
			`movw -12(%ebp),%dx`
			`orw $0x0180,%dx`
			`movw %dx,-16(%ebp)`
			`fldcw -16(%ebp) /* load modfied control word */`

			`fldl 8(%ebp)`
FPU specific math code. 1994-02-11 21:20:17 +03:00			`fldl2e`
			`fmulp /* x * log2(e) */`
			`fstl %st(1)`
			`frndint /* int(x * log2(e)) */`
use one less fp stack slot 1996-07-03 21:31:28 +04:00			`fxch %st(1)`
			`fsub %st(1),%st /* fract(x * log2(e)) */`
FPU specific math code. 1994-02-11 21:20:17 +03:00			`f2xm1 /* 2^(fract(x * log2(e))) - 1 */`
			`fld1`
			`faddp /* 2^(fract(x * log2(e))) */`
			`fscale /* e^x */`
Fix from Bruce Evans. Commited to FreeBSD earlier this month, but was never forwarded to me :-(. > Clean up the FP stack before returning. The i387 exp() leaked an FP > register on its first call. Subsequent calls reused the register so > the leak didn't accumulate. 1996-06-25 06:07:09 +04:00			`fstpl %st(1)`
It's necessary to use 64 bit precision to avoid errors in the least significant bit(s) (for some operands). 1996-07-03 21:27:34 +04:00
			`fldcw -12(%ebp) /* restore original control word */`

			`leave`
FPU specific math code. 1994-02-11 21:20:17 +03:00			`ret`