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/* Copyright (c) 2002 Michael Stumpf <mistumpf@de.pepperl-fuchs.com>
Copyright (c) 2006 Dmitry Xmelkov
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.
* Neither the name of the copyright holders nor the names of
contributors may be used to endorse or promote products derived
from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE. */
/* $Id: tanh.S,v 1.9 2007/01/14 15:13:54 dmix Exp $ */
#include "fp32def.h"
#include "asmdef.h"
/* float tanh (float x);
The tanh() function returns the hyperbolic tangent of x, which is
defined mathematically as sinh(x) / cosh(x).
Algorithm:
if (fabs(x) <= X2SMALL)
return Polinom(x)
else
return sign(x) * (1 - exp(-2*fabs(x))) / (1 + exp(-2*fabs(x)))
*/
#define X2SMALL 0x3e0fffff /* < 0.140625 */
#define FL_P1 0x3f800000 /* +1.0 */
#define exp_lo r20 /* float ldexp (float, int exp); */
#define exp_hi r21
ENTRY tanh
; save sign
push rA3
; is arg too small ?
andi rA3, 0x7f
ldi ZH, hhi8 (X2SMALL + 1)
cpi rA2, hlo8 (X2SMALL + 1)
cpc rA3, ZH
brsh 1f
; for small x
ldi ZL, lo8(.L_table)
ldi ZH, hi8(.L_table)
rcall _U(__fp_powsodd)
rjmp 2f
; exp(-2*fabs(x))
1: ori rA3, 0x80
ldi exp_lo, lo8(1)
ldi exp_hi, hi8(1)
rcall _U(ldexp) ; possible overflow -- no matter
rcall _U(exp)
; save result and calculate 1 + exp(-2*fabs(x))
push rA3
push rA2
push rA1
push rA0
ldi rB0, lo8(FL_P1)
ldi rB1, hi8(FL_P1)
ldi rB2, hlo8(FL_P1)
ldi rB3, hhi8(FL_P1)
rcall _U(__addsf3)
; save/restore and calculate 1 - exp(-2*fabs(x))
pop rB0
pop rB1
pop rB2
pop rB3
push rA3
push rA2
push rA1
push rA0
ldi rA0, lo8(FL_P1)
ldi rA1, hi8(FL_P1)
ldi rA2, hlo8(FL_P1)
ldi rA3, hhi8(FL_P1)
rcall _U(__subsf3)
; restore
pop rB0
pop rB1
pop rB2
pop rB3
; divide
rcall _U(__divsf3)
; sign
2: pop r0
sbrc r0, 7
subi rA3, 0x80
ret
ENDFUNC
PGM_SECTION
.L_table:
.byte 2
.byte 0x89,0x88,0x08,0x3e ; 2/15
.byte 0xab,0xaa,0xaa,0xaa,0xbe ; -1/3
.byte 0x00,0x00,0x00,0x80,0x3f ; 1
.end
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