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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: frexp.S,v 1.9.2.1 2008/03/29 00:54:24 dmix Exp $ */
#include "fp32def.h"
#include "asmdef.h"
/* float frexp (float A, int *pexp);
The frexp() function is used to split the number A into a normalized
fraction and an exponent which is stored by pexp.
Return:
If A is a normal float point number, the frexp() function returns the
value v, such that v has a magnitude in the interval [1/2, 1) or zero,
and A equals v times 2 raised to the power *pexp. If A is zero, both
parts of the result are zero. If A is not a finite number, the frexp()
returns A as is and stores 0 by pexp.
Note:
This implementation permits a zero pointer as a directive to skip
a storing the exponent.
*/
#define pexp_lo r20
ENTRY frexp
X_movw ZL, pexp_lo
; Write 0 for next cases: Zero, Inf or NaN.
#if defined(__AVR_XMEGA__) && __AVR_XMEGA__
adiw ZL, 0
breq 1f
#endif
st Z, r1
std Z+1, r1
1:
rcall _U(__fp_splitA)
brcs .L_nf ; return the same value
tst rA3
breq 3f
subi rA3, 126
sbc rB3, rB3
sbrs rA2, 7
rcall _U(__fp_norm2)
#if defined(__AVR_XMEGA__) && __AVR_XMEGA__
adiw ZL, 0
breq 2f
st Z, rA3
std Z+1, rB3
2:
#else
; NULL is a legal address. Instead to check Z==0, will simply
; write and restore r1.
st Z, rA3
std Z+1, rB3
clr r1 ; protection to Z == 0
#endif
andi rA2, 0x7f
ldi rA3, 0x3f
3: bld rA3, 7 ; restore sign
ret
.L_nf:
rjmp _U(__fp_mpack)
ENDFUNC
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