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/* -*- Mode: Asm -*- */
/* Copyright (c) 2002 Michael Stumpf <mistumpf@de.pepperl-fuchs.com>
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: fp_merge.S,v 1.6 2005/09/13 13:29:54 joerg_wunsch Exp $ */
/*
fp_merge.S is part of FPlib V 0.3.0 ported to avr-as
for details see readme.fplib
*------------------------------------------------------------------------------------------
* merge up in sign : exponent : fraction : fraction extention
* x T rA3 rA2:rA1:rA0:rAE
*/
#if !defined(__DOXYGEN__)
#include "gasava.inc"
#include "macros.inc"
#include "fplib.inc"
TEXT_SEG(fplib, __fp_merge)
FUNCTION(__fp_merge)
1:
DEC rA3
ADD rAE,rAE
adc rA0,rA0
adc rA1,rA1
adc rA2,rA2
; normalize (?) does any split number comes here unnormal? ; yes, _floor, _ceil!
GLOBAL(__fp_merge)
CLR rT1c ; clr rT1c on all return paths
TST rA3 ; exponent == 0
BREQ 3f ; underflow
TST rA2
BRPL 1b ; shift left until MSB set
CPI rA3,0xFF
BREQ 2f ; keep exp == 0xFF, no rounding
; if rAE == 0x80 (exactely 0.5 LSB, half way between two numbers )
; choose the one which makes the lsb of the answer 0.
; what about rAE:rr1:rr0 of mul
ADD rAE,rAE
BRCC 2f ; no LSB : round to lower number
BRNE 1f ; rAE > 0x80 : round to upper number
TST rT0
BRNE 1f ; rAE=0x80:NN:MM , rT1c = NN | MM
SBRS rA0,0 ; R1 == 0x80 : round to even
RJMP 2f ;
1:
SUBI rA0,0xFF
SBCI rA1,0xFF
SBCI rA2,0xFF
SBCI rA3,0xFF
2: ; pack expanded FP number
ROL rA2 ; MSB is hidden 1
ROR rA3
ROR rA2
BLD rA3,7 ; get sign
RET
3:
RJMP _U(__fp_zero) ; merge segments
ENDFUNC
#endif /* not __DOXYGEN__ */
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