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      1 /*	$NetBSD: e_exp.S,v 1.14 2008/06/23 10:24:13 drochner 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 1.14 2008/06/23 10:24:13 drochner 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 	XMM_ONE_ARG_DOUBLE_PROLOGUE
     50 	/*
     51 	 * If x is +-Inf, then the subtraction would give Inf-Inf = NaN.
     52 	 * Avoid this.  Also avoid it if x is NaN for convenience.
     53 	 */
     54 	movl	ARG_DOUBLE_ONE_MSW, %eax
     55 	andl	$0x7fffffff, %eax
     56 	cmpl	$0x7ff00000, %eax
     57 	jae	x_Inf_or_NaN
     58 
     59 	fldl	ARG_DOUBLE_ONE
     60 
     61 	/*
     62 	 * Ensure that the rounding mode is to nearest (to give the smallest
     63 	 * possible fraction) and that the precision is as high as possible.
     64 	 * We may as well mask interrupts if we switch the mode.
     65 	 */
     66 #define CWSTORE_SAV ARG_DOUBLE_ONE_LSW /* XXX overwrites the argument */
     67 #define CWSTORE_TMP ARG_DOUBLE_ONE_MSW
     68 	fstcw	CWSTORE_SAV
     69 	movl	CWSTORE_SAV, %eax
     70 	andl	$0x0f00, %eax
     71 	cmpl	$0x0300, %eax		/* RC == 0 && PC == 3? */
     72 	je	1f			/* jump if mode is good */
     73 	movl	$0x137f, CWSTORE_TMP
     74 	fldcw	CWSTORE_TMP
     75 1:
     76 	fldl2e
     77 	fmulp				/* x * log2(e) */
     78 	fst	%st(1)
     79 	frndint				/* int(x * log2(e)) */
     80 	fst	%st(2)
     81 	fsubrp				/* fract(x * log2(e)) */
     82 	f2xm1				/* 2^(fract(x * log2(e))) - 1 */
     83 	fld1
     84 	faddp				/* 2^(fract(x * log2(e))) */
     85 	fscale				/* e^x */
     86 	fstp	%st(1)
     87 	je	1f
     88 	fldcw	CWSTORE_SAV
     89 1:
     90 	XMM_DOUBLE_EPILOGUE
     91 	ret
     92 x_Inf_or_NaN:
     93 	/*
     94 	 * Return 0 if x is -Inf.  Otherwise just return x, although the
     95 	 * C version would return (x + x) (Real Indefinite) if x is a NaN.
     96 	 */
     97 	cmpl	$0xfff00000, ARG_DOUBLE_ONE_MSW
     98 	jne	x_not_minus_Inf
     99 	cmpl	$0, ARG_DOUBLE_ONE_LSW
    100 	jne	x_not_minus_Inf
    101 	fldz
    102 	XMM_DOUBLE_EPILOGUE
    103 	ret
    104 
    105 x_not_minus_Inf:
    106 	fldl	ARG_DOUBLE_ONE
    107 	XMM_DOUBLE_EPILOGUE
    108 	ret
    109