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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: fp_trunc.S,v 1.1 2007/01/14 15:00:13 dmix Exp $ */
#include "fp32def.h"
#include "asmdef.h"
/* <non_standart> __fp_trunc (float A);
This is an internal functions. __fp_trunc() splits argument and
truncates to zero direction. It is intended as first part of work
in floor(), ceil(), trunc() functions.
Return:
T - sign bit
C - set if A is not finite (A is splited)
rA3 - exponent:
0 - A is zero
1..126 - fabs(A) < 1
127.. - fabs(A) >= 1
rA2.rA1.rA0 - mantissa (with hidden bit)
rAE - flag of nonzero fraction
Notes:
* Return value is not a float value. Function, like __fp_mpack(),
is needed to merge a float.
* In case of 'fabs(A) < 1' rA2.rA1.rA0 and rAE are random.
*/
ENTRY __fp_trunc
rcall _U(__fp_splitA)
brcs 9f
; A is finite
ldi rAE, 126
cp rAE, rA3
brsh 9f
; fabs (A) >= 1.0
clr rAE
3: cpi rA3, 127+23-7
brsh 5f ; shift by 1..7 positions or no shift
; quick shift by 8
cp r1, rA0
adc rAE, r1
mov rA0, rA1
mov rA1, rA2
clr rA2
subi rA3, -8
rjmp 3b
; slow shift
4: lsr rA2
ror rA1
ror rA0
adc rAE, r1
inc rA3
5: cpi rA3, 127+23
brlo 4b
9: ret ; C == 0
ENDFUNC
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