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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: ldexp.S,v 1.11 2007/01/14 15:10:40 dmix Exp $ */
#include "fp32def.h"
#include "asmdef.h"
/* double ldexp (double x, int exp)
The ldexp() function returns the result of multiplying the
floating-point number x by 2 raised to the power exp.
*/
#define exp_lo r20
#define exp_hi r21
FUNCTION ldexp
.L_inf: rjmp _U(__fp_inf)
.L_pk: rjmp _U(__fp_mpack)
ENTRY ldexp
rcall _U(__fp_splitA)
brcs .L_pk ; as is
tst rA3
breq .L_pk ; ldexp(0,*) is always 0
.ifnc rB3, exp_hi
.err ; rB3 and exp_hi are different
.endif
add rA3, exp_lo ; rB3.rA3 := new exponent
adc rB3, r1
brvs .L_inf ; overflow is possible for exp > 0 only
; check exponent for minus and zero
subi rA3, lo8(1)
sbci rB3, hi8(1)
brlt 5f ; denormalization is needed
breq .L_pack ; normalization is impossible
1: tst rA2
brmi 2f
lsl rA0
rol rA1
rol rA2
subi rA3, lo8(1)
sbci rB3, hi8(1)
brne 1b ; C == 0, Z == 0
; check to overflow
2: cpi rA3, 254
cpc rB3, r1
brge .L_inf
.L_pack:
lsl rA2
adc rA3, r1 ; restore exponent for normal numbers
lsr rA3
ror rA2
bld rA3, 7 ; sign
ret
; exponent <= 0
5: cpi rB3, hi8(-24)
brlt .L_zero
cpi rA3, lo8(-24)
brlt .L_zero
; denormalize A
clr rAE
6: lsr rA2
ror rA1
ror rA0
ror rAE
brcc 7f
ori rAE, 1
7: inc rA3
brne 6b
.L_round:
lsl rAE
brcc .L_pack
brne 4f
sbrs rA0, 0
rjmp .L_pack
4: subi rA0, -1
sbci rA1, -1
sbci rA2, -1
sbci rA3, -1
rjmp .L_pack
.L_zero:
rjmp _U(__fp_szero)
ENDFUNC
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