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|
; $Id: expf.asm $
;; @file
; IPRT - No-CRT expf - AMD64 & X86.
;
;
; Copyright (C) 2006-2022 Oracle and/or its affiliates.
;
; This file is part of VirtualBox base platform packages, as
; available from https://www.virtualbox.org.
;
; This program is free software; you can redistribute it and/or
; modify it under the terms of the GNU General Public License
; as published by the Free Software Foundation, in version 3 of the
; License.
;
; This program is distributed in the hope that it will be useful, but
; WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
; General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program; if not, see <https://www.gnu.org/licenses>.
;
; The contents of this file may alternatively be used under the terms
; of the Common Development and Distribution License Version 1.0
; (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
; in the VirtualBox 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.
;
; SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
;
%define RT_ASM_WITH_SEH64
%include "iprt/asmdefs.mac"
%include "iprt/x86.mac"
BEGINCODE
extern NAME(RT_NOCRT(feraiseexcept))
;;
; Compute the e (2.7182818...) to the power of rd.
; @returns st(0) / xmm0
; @param rd [xSP + xCB*2] / xmm0
RT_NOCRT_BEGINPROC expf
push xBP
SEH64_PUSH_xBP
mov xBP, xSP
SEH64_SET_FRAME_xBP 0
sub xSP, 20h
SEH64_ALLOCATE_STACK 20h
SEH64_END_PROLOGUE
;
; Load the input into st0.
;
%ifdef RT_ARCH_AMD64
movss [xBP - 10h], xmm0
fld dword [xBP - 10h]
%else
fld dword [xBP + xCB*2]
%endif
;
; Weed out non-normal values.
;
fxam
fnstsw ax
mov cx, ax
and ax, X86_FSW_C3 | X86_FSW_C2 | X86_FSW_C0
cmp ax, X86_FSW_C2 ; Normal finite number (excluding zero)
je .finite
cmp ax, X86_FSW_C3 ; Zero
je .zero
cmp ax, X86_FSW_C3 | X86_FSW_C2 ; Denormals
je .finite
cmp ax, X86_FSW_C0 | X86_FSW_C2 ; Infinity.
je .inf
jmp .nan
.finite:
;
; Convert to power of 2 and it'll be the same as exp2.
;
fldl2e ; -> st0=log2(e); st1=input
fmulp ; -> st0=input*log2(e)
;
; Split the job in two on the fraction and integer input parts.
;
fld st0 ; Push a copy of the input on the stack.
frndint ; st0 = (int)(input*log2(e))
fsub st1, st0 ; st1 = input*log2(e) - (int)input*log2(e); i.e. st1 = fraction, st0 = integer.
fxch ; st0 = fraction, st1 = integer.
; 1. Calculate on the fraction.
f2xm1 ; st0 = 2**fraction - 1.0
fld1
faddp ; st0 = 2**fraction
; 2. Apply the integer power of two.
fscale ; st0 = result; st1 = integer part of input.
fstp st1 ; st0 = result; no st1.
;
; Return st0.
;
.return_val:
%ifdef RT_ARCH_AMD64
fstp dword [xBP - 10h]
movss xmm0, [xBP - 10h]
%endif
.return:
leave
ret
;
; +/-0.0: Return +1.0
;
.zero:
ffreep st0
fld1
jmp .return_val
;
; -Inf: Return +0.0.
; +Inf: Return +Inf. Join path with NaN.
;
.inf:
test cx, X86_FSW_C1 ; sign bit
jz .nan
ffreep st0
fldz
jmp .return_val
;
; NaN: Return the input NaN value as is, if we can.
;
.nan:
%ifdef RT_ARCH_AMD64
ffreep st0
%endif
jmp .return
ENDPROC RT_NOCRT(expf)
|
