i386/src/nextafter.s

	nextafter.s revision 25c28e83beb90e7c80452a7c818c5e6f73a07dc8
/*
 * 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 "nextafter.s"

#include "libm.h"
LIBM_ANSI_PRAGMA_WEAK(nextafter,function)
    .weak _nextafter
    .type _nextafter,@function
_nextafter  = __nextafter
#include "libm_synonyms.h"
#include "libm_protos.h"

    .data
    .align  8
Fmin:   .long   0x1,0x0
ftmp:   .long   0,0     /// WILL WRITE INTO


    ENTRY(nextafter)
    pushl   %ebp
    movl    %esp,%ebp
    fldl    16(%ebp)    / y
    subl    $8,%esp
    fldl    8(%ebp)     / load x
    fucom           / x : y
    fstsw   %ax
    sahf
    jp  .NaN
    je  .equal
    fstp    %st(1)      / x
    ja  .bigger
    / x < y
    ftst
    movl    $1,%ecx     /// Fmin
    movl    %ecx,-8(%ebp)
    movl    $0,%ecx     /// Fmin+4
    movl    %ecx,-4(%ebp)
    fnstsw  %ax
    sahf
    je  .final
    ja  .addulp
    jb  .subulp
.bigger:
    / x > y
    ftst
    movl    $1,%ecx     /// Fmin
    movl    %ecx,-8(%ebp)
    movl    $0,%ecx     /// Fmin+4
    xorl    $0x80000000,%ecx
    movl    %ecx,-4(%ebp)
    fnstsw  %ax
    sahf
    je  .final
    jb  .addulp
.subulp:
    movl    8(%ebp),%eax    / low x
    movl    12(%ebp),%ecx   / high x
    subl    $1,%eax     / low x - ulp
    movl    %eax,-8(%ebp)
    sbbl    $0x0,%ecx
    movl    %ecx,-4(%ebp)
    jmp .final
.addulp:
    movl    8(%ebp),%eax    / low x
    movl    12(%ebp),%ecx   / high x
    addl    $1,%eax     / low x + ulp
    movl    %eax,-8(%ebp)
    adcl    $0x0,%ecx
    movl    %ecx,-4(%ebp)

.final:
    fstp    %st(0)
    fldl    -8(%ebp)
    andl    $0x7ff00000,%ecx
    jz  .underflow
    cmpl    $0x7ff00000,%ecx
    je  .overflow
    jmp .return
.overflow:
    PIC_SETUP(1)
    pushl   $46
    fstp    %st(0)      / stack empty
    pushl   -4(%ebp)
    pushl   -8(%ebp)
    pushl   -4(%ebp)
    pushl   -8(%ebp)
    call    PIC_F(_SVID_libm_err)
    addl    $20,%esp
    PIC_WRAPUP
    jmp .return
.underflow:
    PIC_SETUP(2)
    fldl    PIC_L(Fmin)
    fmul    %st(0),%st
    fstpl   PIC_L(ftmp) / create underflow signal
    PIC_WRAPUP
    jmp .return
.equal:
    fstp    %st(0)      / C99 says to return y when x == y
    jmp .return
.NaN:
    faddp   %st,%st(1)  / x+y,x
.return:
    fwait
    leave
    ret
    .align  4
    SET_SIZE(nextafter)