i386/src/round.s

	round.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   "round.s"

#include "libm.h"
LIBM_ANSI_PRAGMA_WEAK(round,function)
#include "libm_synonyms.h"
#undef fabs

    .section .rodata
    .align  4
.Lhalf: .float  0.5

    ENTRY(round)
    movl    %esp,%ecx
    subl    $8,%esp
    fstcw   -8(%ecx)
    fldl    4(%ecx)
    movw    -8(%ecx),%dx
    andw    $0xf3ff,%dx
    movw    %dx,-4(%ecx)
    fldcw   -4(%ecx)        / set RD = to_nearest
    fld %st(0)
    frndint             / [x],x
    fstcw   -4(%ecx)
    movw    -4(%ecx),%dx
    andw    $0xf3ff,%dx
    movw    -8(%ecx),%ax
    andw    $0x0c00,%ax
    orw %dx,%ax
    movw    %ax,-8(%ecx)
    fldcw   -8(%ecx)        / restore RD
    fucom               / check if x is already an integer
    fstsw   %ax
    sahf
    jp  0f
    je  0f
    fxch                / x,[x]
    fsub    %st(1),%st      / x-[x],[x]
    fabs                / |x-[x]|,[x]
    PIC_SETUP(1)
    fcoms   PIC_L(.Lhalf)
    PIC_WRAPUP
    fnstsw  %ax
    sahf
    jae 2f          / if |x-[x]| = 0.5 goto halfway,
                    / most cases will not take branch.
0:
    addl    $8,%esp
    fstp    %st(0)
    ret
2:
    / x = n+0.5, recompute round(x) as x+sign(x)*0.5
    fldl    4(%ecx)         / x, 0.5, [x]
    movl    8(%ecx),%eax        / high part of x
    andl    $0x80000000,%eax
    jnz 3f
    faddp
    addl    $8,%esp
    fstp    %st(1)
    ret
3:
    / here, x is negative, so return x-0.5
    fsubp   %st,%st(1)      / x-0.5,[x]
    addl    $8,%esp
    fstp    %st(1)
    ret
    .align  4
    SET_SIZE(round)