/*
 * 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 "exp.s"

#include "libm.h"
LIBM_ANSI_PRAGMA_WEAK(exp,function)
#include "libm_protos.h"

        ENTRY(exp)
        movl    8(%esp),%ecx            / ecx <-- hi_32(x)
        andl    $0x7fffffff,%ecx        / ecx <-- hi_32(|x|)
        cmpl    $0x3fe62e42,%ecx        / Is |x| < ln(2)?
        jb      .shortcut               / If so, take a shortcut.
        je      .check_tail             / |x| may be only slightly < ln(2)
        cmpl    $0x7ff00000,%ecx        / hi_32(|x|) >= hi_32(INF)?
        jae     .not_finite             / if so, x is not finite
.finite_non_special:                    / Here, ln(2) < |x| < INF
        fldl    4(%esp)                 / push x
        subl    $8,%esp
                                        /// overhead of RP save/restore; 63/15
        fstcw   (%esp)                  /// ; 15/3
        movw    (%esp),%ax              /// ; 4/1
        movw    %ax,4(%esp)             /// save old RP; 2/1
        orw     $0x0300,%ax             /// force 64-bit RP; 2/1
        movw    %ax,(%esp)              /// ; 2/1
        fldcw   (%esp)                  /// ; 19/4
        fldl2e                          / push log2e   }not for xtndd_dbl
        fmulp   %st,%st(1)              / z = x*log2e  }not for xtndd_dbl
        fld     %st(0)                  / duplicate stack top
        frndint                         / [z],z
        fucom                           / This and the next 3 instructions
        fstsw  %ax                      / add 10 clocks to runtime of the
        sahf                            / main branch, but save about 265
        je      .z_integral             / upon detection of integral z.
        / [z] != z, compute exp(x)
        fxch                            / z,[z]
        fsub    %st(1),%st              / z-[z],[z]
        f2xm1                           / 2**(z-[z])-1,[z]
        fld1                            / 1,2**(z-[z])-1,[z]
        faddp   %st,%st(1)              /   2**(z-[z])  ,[z]
.merge:
        fscale                          /   exp(x)      ,[z]
        fstp    %st(1)
        fstcw   (%esp)                  / restore RD
        movw    (%esp),%dx
        andw    $0xfcff,%dx
        movw    4(%esp),%cx
        andw    $0x0300,%cx
        orw     %dx,%cx
        movw    %cx,(%esp)
        fldcw   (%esp)                  /// restore old RP; 19/4
        fstpl   (%esp)                  / round to double
        fldl    (%esp)                  / exp(x) rounded to double
        fxam                            / determine class of exp(x)
        add     $8,%esp
        fstsw   %ax                     / store status in ax
        andw    $0x4500,%ax
        cmpw    $0x0500,%ax
        je      .overflow
        cmpw    $0x4000,%ax
        je      .underflow
        ret

.overflow:
        fstp    %st(0)                  / stack empty
        push    %ebp
        mov     %esp,%ebp
        PIC_SETUP(1)
        pushl   $6
        jmp     .error

.underflow:
        fstp    %st(0)                  / stack empty
        push    %ebp
        mov     %esp,%ebp
        PIC_SETUP(2)
        pushl   $7

.error:
        pushl   12(%ebp)                / high x
        pushl   8(%ebp)                 / low x
        pushl   12(%ebp)                / high x
        pushl   8(%ebp)                 / low x
        call    PIC_F(_SVID_libm_err)
        addl    $20,%esp
        PIC_WRAPUP
        leave
        ret

.z_integral:                            / here, z is integral
        fstp    %st(0)                  / ,z
        fld1                            / 1,z
        jmp     .merge

.check_tail:
        movl    4(%esp),%edx            / edx <-- lo_32(x)
        cmpl    $0xfefa39ef,%edx        / Is |x| slightly < ln(2)?
        ja      .finite_non_special     / branch if |x| slightly > ln(2)
.shortcut:
        / Here, |x| < ln(2), so |z| = |x*log2(e)| < 1,
        / whence z is in f2xm1's domain.
        fldl    4(%esp)                 / push x
        fldl2e                          / push log2e  }not for xtndd_dbl
        fmulp   %st,%st(1)              / z = x*log2e }not for xtndd_dbl
        f2xm1                           / 2**(x*log2(e))-1 = e**x - 1
        fld1                            / 1,2**(z)-1
        faddp   %st,%st(1)              /   2**(z) = e**x
        ret

.not_finite:
        / Here, flags still have settings from execution of
        /       cmpl    $0x7ff00000,%ecx        / hi_32(|x|) > hi_32(INF)?
        ja      .NaN_or_pinf            / if not, x may be +/- INF
        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    8(%esp),%eax            / eax <-- hi_32(x)
        andl    $0x80000000,%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.
        fldl    4(%esp)
        fwait
        ret
        .align  4
        SET_SIZE(exp)