/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
 */
/*
 * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

        .file "expl.s"

#include "libm.h"
LIBM_ANSI_PRAGMA_WEAK(expl,function)

        .data
        .align  4
ln2_hi: .long   0xd1d00000, 0xb17217f7, 0x00003ffe
ln2_lo: .long   0x4c67fc0d, 0x8654361c, 0x0000bfce

        ENTRY(expl)
        movl    12(%esp),%ecx           / cx <--sign&bexp(x)
        andl    $0x7fff,%ecx            / ecx <-- zero_xtnd(bexp(x))
        cmpl    $0x3ffe,%ecx            / Is |x| < 0.5?
        jb      2f                      / If so, see which shortcut to take
        je      .check_tail             / More checking if 0.5 <= |x| < 1
        cmpl    $0x00007fff,%ecx        / bexp(|x|) = bexp(INF)?
        je      .not_finite             / if so, x is not finite
        cmpl    $0x0000400e,%ecx        / |x| < 32768 = 2^15?
        jb      .finite_non_special     / if so, proceed with argument reduction
        fldt    4(%esp)                 / x
        fld1                            / 1, x
        jmp     1f
.finite_non_special:                    / Here, ln(2) < |x| < 2^15
        fldt    4(%esp)                 / x
        fld     %st(0)                  / x, x
        fldl2e                          / log2(e), x, x
        fmulp                           / z := x*log2(e), x
        frndint                         / [z], x
        fst     %st(2)                  / [z], x, [z]
        PIC_SETUP(1)
        fldt    PIC_L(ln2_hi)           / ln2_hi, [z], x, [z]
        fmulp                           / [z]*ln2_hi, x, [z]
        fsubrp  %st,%st(1)              / x-[z]*ln2_hi, [z]
        fldt    PIC_L(ln2_lo)           / ln2_lo, x-[z]*ln2_hi, [z]
        PIC_WRAPUP
        fmul    %st(2),%st              / [z]*ln2_lo, x-[z]*ln2_hi, [z]
        fsubrp  %st,%st(1)              / r := x-[z]*ln(2), [z]
        fldl2e                          / log2(e), r, [z]
        fmulp                           / f := r*log2(e), [z]
        f2xm1                           / 2^f-1,[z]
        fld1                            / 1, 2^f-1, [z]
        faddp   %st,%st(1)              / 2^f, [z]
1:
        fscale                          / e^x, [z]
        fstp    %st(1)
        ret

2:                                      / Here, |x| < 0.5
        cmpl    $0x3fbe,%ecx            / Is |x| >= 2^-65?
        jae     .shortcut               / If so, take a shortcut
        fldt    4(%esp)                 / x
        fld1                            / 1, x
        faddp   %st,%st(1)              / 1+x (for inexact & directed rounding)
        ret

.check_tail:
        movl    8(%esp),%ecx            / ecx <-- hi_32(sgnfcnd(x))
        cmpl    $0xb17217f7,%ecx        / Is |x| < ln(2)?
        ja      .finite_non_special
        jb      .shortcut
        movl    4(%esp),%edx            / edx <-- lo_32(x)
        cmpl    $0xd1cf79ab,%edx        / Is |x| slightly < ln(2)?
        ja      .finite_non_special     / branch if |x| slightly > ln(2)
.shortcut:
        / Here, |x| < ln(2), so |z| = |x/ln(2)| < 1,
        / whence z is in f2xm1's domain.
        fldt    4(%esp)                 / x
        fldl2e                          / log2(e), x
        fmulp                           / x*log2(e)
        f2xm1                           / 2^(x*log2(e))-1 = e^x-1
        fld1                            / 1, e^x-1
        faddp   %st,%st(1)              / e^x
        ret

.not_finite:
        movl    8(%esp),%ecx            / ecx <-- hi_32(sgnfcnd(x))
        cmpl    $0x80000000,%ecx        / hi_32(|x|) = hi_32(INF)?
        jne     .NaN_or_pinf            / if not, x is NaN
        movl    4(%esp),%edx            / edx <-- lo_32(x)
        cmpl    $0,%edx                 / lo_32(x) = 0?
        jne     .NaN_or_pinf            / if not, x is NaN
        movl    12(%esp),%eax           / ax <-- sign&bexp((x))
        andl    $0x00008000,%eax        / here, x is infinite, but +/-?
        jz      .NaN_or_pinf            / branch if x = +INF
        fldz                            / Here, x = -inf, so return 0
        ret

.NaN_or_pinf:
        / Here, x = NaN or +inf, so load x and return immediately.
        fldt    4(%esp)
        fadd    %st(0),%st              / quiet SNaN
        ret
        .align  4
        SET_SIZE(expl)