source: vbox/trunk/src/VBox/Runtime/common/math/floor.asm@ 10949

; $Id: floor.asm 8256 2008-04-21 20:53:28Z vboxsync $
;; @file
; IPRT - No-CRT floor - AMD64 & X86.
;

;
; Copyright (C) 2006-2007 Sun Microsystems, Inc.
;
; This file is part of VirtualBox Open Source Edition (OSE), as
; available from http://www.virtualbox.org. This file is free software;
; you can redistribute it and/or modify it under the terms of the GNU
; General Public License (GPL) as published by the Free Software
; Foundation, in version 2 as it comes in the "COPYING" file of the
; VirtualBox OSE distribution. VirtualBox OSE is distributed in the
; hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
;
; The contents of this file may alternatively be used under the terms
; of the Common Development and Distribution License Version 1.0
; (CDDL) only, as it comes in the "COPYING.CDDL" file of the
; VirtualBox OSE distribution, in which case the provisions of the
; CDDL are applicable instead of those of the GPL.
;
; You may elect to license modified versions of this file under the
; terms and conditions of either the GPL or the CDDL or both.
;
; Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa
; Clara, CA 95054 USA or visit http://www.sun.com if you need
; additional information or have any questions.
;

%include "iprt/asmdefs.mac"

BEGINCODE

%ifdef RT_ARCH_AMD64
 %define _SP rsp
 %define _BP rbp
 %define _S  8
%else
 %define _SP esp
 %define _BP ebp
 %define _S  4
%endif

;;
; Compute the largest integral value not greater than rd.
; @returns 32-bit: st(0)   64-bit: xmm0
; @param    rd      32-bit: [ebp + 8]   64-bit: xmm0
BEGINPROC RT_NOCRT(floor)
    push    _BP
    mov     _BP, _SP
    sub     _SP, 10h

%ifdef RT_ARCH_AMD64
    movsd   [_SP], xmm0
    fld     qword [_SP]
%else
    fld     qword [_BP + _S*2]
%endif

    ; Make it round down by modifying the fpu control word.
    fstcw   [_BP - 10h]
    mov     eax, [_BP - 10h]
    or      eax, 00400h
    and     eax, 0f7ffh
    mov     [_BP - 08h], eax
    fldcw   [_BP - 08h]

    ; Round ST(0) to integer.
    frndint

    ; Restore the fpu control word.
    fldcw   [_BP - 10h]

%ifdef RT_ARCH_AMD64
    fstp    qword [_SP]
    movsd   xmm0, [_SP]
%endif
    leave
    ret
ENDPROC   RT_NOCRT(floor)