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e_exp.S revision 1.12 
      1 /*	$NetBSD: e_exp.S,v 1.12 2002/02/27 16:32:46 christos Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1993,94 Winning Strategies, Inc.
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  * 3. All advertising materials mentioning features or use of this software
     16  *    must display the following acknowledgement:
     17  *      This product includes software developed by Winning Strategies, Inc.
     18  * 4. The name of the author may not be used to endorse or promote products
     19  *    derived from this software without specific prior written permission.
     20  *
     21  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     22  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     23  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     24  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     25  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     26  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     27  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     28  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     29  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     30  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     31  */
     32 
     33 /*
     34  * Written by:
     35  *	J.T. Conklin (jtc (at) wimsey.com), Winning Strategies, Inc.
     36  */
     37 
     38 #include <machine/asm.h>
     39 
     40 #include "abi.h"
     41 
     42 RCSID("$NetBSD: e_exp.S,v 1.12 2002/02/27 16:32:46 christos Exp $")
     43 #if 0
     44 RCSID("$FreeBSD: src/lib/msun/i387/e_exp.S,v 1.8.2.1 2000/07/10 09:16:28 obrien Exp $")
     45 #endif
     46 
     47 /* e^x = 2^(x * log2(e)) */
     48 ENTRY(__ieee754_exp)
     49 #ifndef __i386__
     50 	/*
     51 	 * XXX: This code is broken and needs to be merged with the i386 case.
     52 	 */
     53 	fstcw	-12(%rsp)
     54 	movw	-12(%rsp),%dx
     55 	orw	$0x0180,%dx
     56 	movw	%dx,-16(%rsp)
     57 	fldcw	-16(%rsp)
     58 	movsd	%xmm0,-8(%rsp)
     59 	fldl	-8(%rsp)
     60 
     61 	fldl2e
     62 	fmulp				/* x * log2(e) */
     63 	fld	%st(0)
     64 	frndint				/* int(x * log2(e)) */
     65 	fxch	%st(1)
     66 	fsub	%st(1),%st		/* fract(x * log2(e)) */
     67 	f2xm1				/* 2^(fract(x * log2(e))) - 1 */
     68 	fld1
     69 	faddp				/* 2^(fract(x * log2(e))) */
     70 	fscale				/* e^x */
     71 	fstp	%st(1)
     72 
     73 	fstpl	-8(%rsp)
     74 	movsd	-8(%rsp),%xmm0
     75 	fldcw	-12(%rsp)
     76 	ret
     77 #else
     78 	/*
     79 	 * If x is +-Inf, then the subtraction would give Inf-Inf = NaN.
     80 	 * Avoid this.  Also avoid it if x is NaN for convenience.
     81 	 */
     82 	movl	8(%esp),%eax
     83 	andl	$0x7fffffff,%eax
     84 	cmpl	$0x7ff00000,%eax
     85 	jae	x_Inf_or_NaN
     86 
     87 	fldl	4(%esp)
     88 
     89 	/*
     90 	 * Ensure that the rounding mode is to nearest (to give the smallest
     91 	 * possible fraction) and that the precision is as high as possible.
     92 	 * We may as well mask interrupts if we switch the mode.
     93 	 */
     94 	fstcw	4(%esp)
     95 	movl	4(%esp),%eax
     96 	andl	$0x0300,%eax
     97 	cmpl	$0x0300,%eax		/* RC == 0 && PC == 3? */
     98 	je	1f			/* jump if mode is good */
     99 	movl	$0x137f,8(%esp)
    100 	fldcw	8(%esp)
    101 1:
    102 	fldl2e
    103 	fmulp				/* x * log2(e) */
    104 	fst	%st(1)
    105 	frndint				/* int(x * log2(e)) */
    106 	fst	%st(2)
    107 	fsubrp				/* fract(x * log2(e)) */
    108 	f2xm1				/* 2^(fract(x * log2(e))) - 1 */
    109 	fld1
    110 	faddp				/* 2^(fract(x * log2(e))) */
    111 	fscale				/* e^x */
    112 	fstp	%st(1)
    113 	je	1f
    114 	fldcw	4(%esp)
    115 1:
    116 	ret
    117 
    118 x_Inf_or_NaN:
    119 	/*
    120 	 * Return 0 if x is -Inf.  Otherwise just return x, although the
    121 	 * C version would return (x + x) (Real Indefinite) if x is a NaN.
    122 	 */
    123 	cmpl	$0xfff00000,8(%esp)
    124 	jne	x_not_minus_Inf
    125 	cmpl	$0,4(%esp)
    126 	jne	x_not_minus_Inf
    127 	fldz
    128 	ret
    129 
    130 x_not_minus_Inf:
    131 	fldl	4(%esp)
    132 	ret
    133 #endif
    134