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|
|
| 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.
|
|
| Copyright (C) Motorola, Inc. 1990
| All Rights Reserved
|
| For details on the license for this file, please see the
| file, README, in this same directory.
|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
|
.global sgetexp
sgetexp:
movew LOCAL_EX(%a0),%d0 |get the exponent
bclrl #15,%d0 |clear the sign bit
subw #0x3fff,%d0 |subtract off the bias
fmovew %d0,%fp0 |move the exp to fp0
rts
.global sgetexpd
sgetexpd:
bclrb #sign_bit,LOCAL_EX(%a0)
bsr nrm_set |normalize (exp will go negative)
movew LOCAL_EX(%a0),%d0 |load resulting exponent into d0
subw #0x3fff,%d0 |subtract off the bias
fmovew %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.
|
.global sgetman
sgetman:
movel USER_FPCR(%a6),%d0
andil #0xffffff00,%d0 |clear rounding precision and mode
fmovel %d0,%fpcr |this fpcr setting is used by the 882
movew LOCAL_EX(%a0),%d0 |get the exp (really just want sign bit)
orw #0x7fff,%d0 |clear old exp
bclrl #14,%d0 |make it the new exp +-3fff
movew %d0,LOCAL_EX(%a0) |move the sign & exp back to fsave stack
fmovex (%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.
|
.global sgetmand
sgetmand:
movel LOCAL_HI(%a0),%d0 |load ms mant in d0
movel LOCAL_LO(%a0),%d1 |load ls mant in d1
bsr shft |shift mantissa bits till msbit is set
movel %d0,LOCAL_HI(%a0) |put ms mant back on stack
movel %d1,LOCAL_LO(%a0) |put ls mant back on stack
bras 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:
tstl %d0 |if any bits set in ms mant
bnes upper |then branch
| ;else no bits set in ms mant
tstl %d1 |test if any bits set in ls mant
bnes cont |if set then continue
bras shft_end |else return
cont:
movel %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
lsll %d3,%d0 |shift first 1 to integer bit in ms mant
movel (%a7)+,%d3 |restore d3
bras shft_end
upper:
moveml %d3/%d5/%d6,-(%a7) |save registers
bfffo %d0{#0:#32},%d3 |find first 1 in ls mant to d0
lsll %d3,%d0 |shift ms mant until j-bit is set
movel %d1,%d6 |save ls mant in d6
lsll %d3,%d1 |shift ls mant by count
movel #32,%d5
subl %d3,%d5 |sub 32 from shift for ls mant
lsrl %d5,%d6 |shift off all bits but those that will
| ;be shifted into ms mant
orl %d6,%d0 |shift the ls mant bits into the ms mant
moveml (%a7)+,%d3/%d5/%d6 |restore registers
shft_end:
rts
|end
|
