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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.
*/
/*
mulsf3x.S is part of FPlib V 0.3.0 ported to avr-as
for details see readme.fplib
*----------------------------------------------------------------------------------------
*
*--- multiplication kernel : used by other high level functions
* multiply two extended numbers RX = AX * BX
* sign not considered, resulting stored in T by ___mulsf3
* AX rA3 : rA2:rA1:rA0:rAE
* BX rB3 : rB2:rB1:rB0:rBE
* RX rA3 : rA2:rA1:rA0:rAE
*/
#if !defined(DOXYGEN)
#include "gasava.inc"
#include "fplib.inc"
TEXT_SEG(fplib, __mulsf3x)
FUNCTION(__mulsf3x)
GLOBAL(__mulsf3x)
TST rA3
BREQ ___mulsf3x_ZERO
___mulsf3_10:
TST rB3
BREQ ___mulsf3x_ZERO
___mulsf3x_00:
SUBI rA3,0x7F ; exp(A) now signed char
SUBI rB3,0x7F ; exp(B) now signed char
ADD rA3,rB3 ; add two signed registers
BRVC ___mulsf3x_20 ; no signed overflow
BRMI ___mulsf3x_INF ; signed overflow : if now negative -> positive overflow
___mulsf3x_ZERO:
RJMP _U(__fp_zerox)
___mulsf3x_20:
SUBI rA3,0x81 ; = ADI,0x7F
CPI rA3,0xFF
BREQ ___mulsf3x_ZERO ; no (unsigned overflow) -> signed underflow
; now multiply mantissa A[rA2:rA1:rA0] * B[rb5:rb4:rb3:rB2:rB1:rB0]
; result : [rr5:rr4:rr3:rr2:rr1:rr0]
#define loop rTI0
#define rr5 rA2 /* push rA2 before */
#define rr4 rA1 /* push rA1 before */
#define rr3 rA0 /* push rA0 before */
#define rr2 rAE /* not used, but right position later on */
#define rr1 rT1c /* free to use, needed after pop */
#define rr0 rT0 /* scratch register, needed after pop */
#define rb5 rTI1 /* */
#define rb4 rBE /* not used */
#define rb3 rB3 /* no longer used */
MOV rb4,rA0 ; rB4 not yet needed
CLR rr0
CLR rr1 ; not conclusive zero for high level function
CLR rr2
CLR rr3
CLR rb3
LDI loop,8 ; loop counter
___mulsf3x_100:
LSR rb4
BRCC ___mulsf3x_101
ADD rr0,rB0
adc rr1,rB1
adc rr2,rB2
adc rr3,rb3
___mulsf3x_101:
ADD rB0,rB0
adc rB1,rB1
adc rB2,rB2
adc rb3,rb3
DEC loop
BRNE ___mulsf3x_100 ;
LDI loop,8 ; loop counter
MOV rb5,rA1 ; rb5 not yet needed
CLR rr4 ; rb4 is allready clear
LDI loop,8 ; loop counter
___mulsf3x_200:
LSR rb5
BRCC ___mulsf3x_201
ADD rr1,rB1
adc rr2,rB2
adc rr3,rb3
adc rr4,rb4
___mulsf3x_201:
ADD rB1,rB1
adc rB2,rB2
adc rb3,rb3
adc rb4,rb4
DEC loop
BRNE ___mulsf3x_200 ;
MOV loop,rA2 ; loop no longer needed, check
CLR rr5 ; rb5 is allready clear
___mulsf3x_300:
LSR loop
BRCC ___mulsf3x_301
ADD rr2,rB2
adc rr3,rb3
adc rr4,rb4
adc rr5,rb5
___mulsf3x_301:
ADD rB2,rB2
adc rb3,rb3
adc rb4,rb4
adc rb5,rb5
TST loop
BRNE ___mulsf3x_300 ;
; multiplication done : result in rr5:rr4:rr3:rr2:rr1:rr0
; = rA2:rA1:rA0:rAE:rr1:rr0
___mulsf3x_400: ; normalize 1.0 * 1.0 = 1.0
; 0x800000 * 0x800000 = 0x40 00 00 00 00 00
; 1.999999 * 1.999999 = 3.99999 ~ 4.0
; 0xFFFFFF * 0xFFFFFF = 0xFF FF FE 00 00 01
TST rA2
BRPL ___mulsf3x_405 ; if MSB erg is clr
INC rA3 ;
BRNE ___mulsf3x_420
___mulsf3x_INF:
RJMP _U(__fp_nanx) ; returns to ___mulsf3 or a high level function : rT1c ok
___mulsf3x_405:
ADD rr0,rr0
adc rr1,rr1
adc rAE,rAE
adc rA0,rA0
adc rA1,rA1
adc rA2,rA2
___mulsf3x_420:
OR rr0,rr1 ; rr0 = rT0 which holds the mantissae extension beyond rAE
RET
ENDFUNC
#endif /* not DOXYGEN */
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