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* $OpenBSD: sgetem.sa,v 1.2 1996/05/29 21:05:37 niklas Exp $
* $NetBSD: sgetem.sa,v 1.2 1994/10/26 07:49:45 cgd Exp $
* MOTOROLA MICROPROCESSOR & MEMORY TECHNOLOGY GROUP
* M68000 Hi-Performance Microprocessor Division
* M68040 Software Package
*
* M68040 Software Package Copyright (c) 1993, 1994 Motorola Inc.
* All rights reserved.
*
* THE SOFTWARE is provided on an "AS IS" basis and without warranty.
* To the maximum extent permitted by applicable law,
* MOTOROLA DISCLAIMS ALL WARRANTIES WHETHER EXPRESS OR IMPLIED,
* INCLUDING IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A
* PARTICULAR PURPOSE and any warranty against infringement with
* regard to the SOFTWARE (INCLUDING ANY MODIFIED VERSIONS THEREOF)
* and any accompanying written materials.
*
* To the maximum extent permitted by applicable law,
* IN NO EVENT SHALL MOTOROLA BE LIABLE FOR ANY DAMAGES WHATSOEVER
* (INCLUDING WITHOUT LIMITATION, DAMAGES FOR LOSS OF BUSINESS
* PROFITS, BUSINESS INTERRUPTION, LOSS OF BUSINESS INFORMATION, OR
* OTHER PECUNIARY LOSS) ARISING OF THE USE OR INABILITY TO USE THE
* SOFTWARE. Motorola assumes no responsibility for the maintenance
* and support of the SOFTWARE.
*
* You are hereby granted a copyright license to use, modify, and
* distribute the SOFTWARE so long as this entire notice is retained
* without alteration in any modified and/or redistributed versions,
* and that such modified versions are clearly identified as such.
* No licenses are granted by implication, estoppel or otherwise
* under any patents or trademarks of Motorola, Inc.
*
* sgetem.sa 3.1 12/10/90
*
* The entry point sGETEXP returns the exponent portion
* of the input argument. The exponent bias is removed
* and the exponent value is returned as an extended
* precision number in fp0. sGETEXPD handles denormalized
* numbers.
*
* The entry point sGETMAN extracts the mantissa of the
* input argument. The mantissa is converted to an
* extended precision number and returned in fp0. The
* range of the result is [1.0 - 2.0).
*
*
* Input: Double-extended number X in the ETEMP space in
* the floating-point save stack.
*
* Output: The functions return exp(X) or man(X) in fp0.
*
* Modified: fp0.
*
SGETEM IDNT 2,1 Motorola 040 Floating Point Software Package
section 8
include fpsp.h
xref nrm_set
*
* This entry point is used by the unimplemented instruction exception
* handler. It points a0 to the input operand.
*
*
*
* SGETEXP
*
xdef sgetexp
sgetexp:
move.w LOCAL_EX(a0),d0 ;get the exponent
bclr.l #15,d0 ;clear the sign bit
sub.w #$3fff,d0 ;subtract off the bias
fmove.w d0,fp0 ;move the exp to fp0
rts
xdef sgetexpd
sgetexpd:
bclr.b #sign_bit,LOCAL_EX(a0)
bsr nrm_set ;normalize (exp will go negative)
move.w LOCAL_EX(a0),d0 ;load resulting exponent into d0
sub.w #$3fff,d0 ;subtract off the bias
fmove.w d0,fp0 ;move the exp to fp0
rts
*
*
* This entry point is used by the unimplemented instruction exception
* handler. It points a0 to the input operand.
*
*
*
* SGETMAN
*
*
* For normalized numbers, leave the mantissa alone, simply load
* with an exponent of +/- $3fff.
*
xdef sgetman
sgetman:
move.l USER_FPCR(a6),d0
andi.l #$ffffff00,d0 ;clear rounding precision and mode
fmove.l d0,fpcr ;this fpcr setting is used by the 882
move.w LOCAL_EX(a0),d0 ;get the exp (really just want sign bit)
or.w #$7fff,d0 ;clear old exp
bclr.l #14,d0 ;make it the new exp +-3fff
move.w d0,LOCAL_EX(a0) ;move the sign & exp back to fsave stack
fmove.x (a0),fp0 ;put new value back in fp0
rts
*
* For denormalized numbers, shift the mantissa until the j-bit = 1,
* then load the exponent with +/1 $3fff.
*
xdef sgetmand
sgetmand:
move.l LOCAL_HI(a0),d0 ;load ms mant in d0
move.l LOCAL_LO(a0),d1 ;load ls mant in d1
bsr shft ;shift mantissa bits till msbit is set
move.l d0,LOCAL_HI(a0) ;put ms mant back on stack
move.l d1,LOCAL_LO(a0) ;put ls mant back on stack
bra.b sgetman
*
* SHFT
*
* Shifts the mantissa bits until msbit is set.
* input:
* ms mantissa part in d0
* ls mantissa part in d1
* output:
* shifted bits in d0 and d1
shft:
tst.l d0 ;if any bits set in ms mant
bne.b upper ;then branch
* ;else no bits set in ms mant
tst.l d1 ;test if any bits set in ls mant
bne.b cont ;if set then continue
bra.b shft_end ;else return
cont:
move.l d3,-(a7) ;save d3
exg d0,d1 ;shift ls mant to ms mant
bfffo d0{0:32},d3 ;find first 1 in ls mant to d0
lsl.l d3,d0 ;shift first 1 to integer bit in ms mant
move.l (a7)+,d3 ;restore d3
bra.b shft_end
upper:
movem.l d3/d5/d6,-(a7) ;save registers
bfffo d0{0:32},d3 ;find first 1 in ls mant to d0
lsl.l d3,d0 ;shift ms mant until j-bit is set
move.l d1,d6 ;save ls mant in d6
lsl.l d3,d1 ;shift ls mant by count
move.l #32,d5
sub.l d3,d5 ;sub 32 from shift for ls mant
lsr.l d5,d6 ;shift off all bits but those that will
* ;be shifted into ms mant
or.l d6,d0 ;shift the ls mant bits into the ms mant
movem.l (a7)+,d3/d5/d6 ;restore registers
shft_end:
rts
end
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