| 1 |
1623 |
jcastillo |
|
|
| 2 |
|
|
| sgetem.sa 3.1 12/10/90
|
| 3 |
|
|
|
|
| 4 |
|
|
| The entry point sGETEXP returns the exponent portion
|
| 5 |
|
|
| of the input argument. The exponent bias is removed
|
| 6 |
|
|
| and the exponent value is returned as an extended
|
| 7 |
|
|
| precision number in fp0. sGETEXPD handles denormalized
|
| 8 |
|
|
| numbers.
|
| 9 |
|
|
|
|
| 10 |
|
|
| The entry point sGETMAN extracts the mantissa of the
|
| 11 |
|
|
| input argument. The mantissa is converted to an
|
| 12 |
|
|
| extended precision number and returned in fp0. The
|
| 13 |
|
|
| range of the result is [1.0 - 2.0).
|
| 14 |
|
|
|
|
| 15 |
|
|
|
|
| 16 |
|
|
| Input: Double-extended number X in the ETEMP space in
|
| 17 |
|
|
| the floating-point save stack.
|
| 18 |
|
|
|
|
| 19 |
|
|
| Output: The functions return exp(X) or man(X) in fp0.
|
| 20 |
|
|
|
|
| 21 |
|
|
| Modified: fp0.
|
| 22 |
|
|
|
|
| 23 |
|
|
|
|
| 24 |
|
|
| Copyright (C) Motorola, Inc. 1990
|
| 25 |
|
|
| All Rights Reserved
|
| 26 |
|
|
|
|
| 27 |
|
|
| THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA
|
| 28 |
|
|
| The copyright notice above does not evidence any
|
| 29 |
|
|
| actual or intended publication of such source code.
|
| 30 |
|
|
|
| 31 |
|
|
|SGETEM idnt 2,1 | Motorola 040 Floating Point Software Package
|
| 32 |
|
|
|
| 33 |
|
|
|section 8
|
| 34 |
|
|
|
| 35 |
|
|
.include "fpsp.h"
|
| 36 |
|
|
|
| 37 |
|
|
|xref nrm_set
|
| 38 |
|
|
|
| 39 |
|
|
|
|
| 40 |
|
|
| This entry point is used by the unimplemented instruction exception
|
| 41 |
|
|
| handler. It points a0 to the input operand.
|
| 42 |
|
|
|
|
| 43 |
|
|
|
|
| 44 |
|
|
|
|
| 45 |
|
|
| SGETEXP
|
| 46 |
|
|
|
|
| 47 |
|
|
|
| 48 |
|
|
.global sgetexp
|
| 49 |
|
|
sgetexp:
|
| 50 |
|
|
movew LOCAL_EX(%a0),%d0 |get the exponent
|
| 51 |
|
|
bclrl #15,%d0 |clear the sign bit
|
| 52 |
|
|
subw #0x3fff,%d0 |subtract off the bias
|
| 53 |
|
|
fmovew %d0,%fp0 |move the exp to fp0
|
| 54 |
|
|
rts
|
| 55 |
|
|
|
| 56 |
|
|
.global sgetexpd
|
| 57 |
|
|
sgetexpd:
|
| 58 |
|
|
bclrb #sign_bit,LOCAL_EX(%a0)
|
| 59 |
|
|
bsr nrm_set |normalize (exp will go negative)
|
| 60 |
|
|
movew LOCAL_EX(%a0),%d0 |load resulting exponent into d0
|
| 61 |
|
|
subw #0x3fff,%d0 |subtract off the bias
|
| 62 |
|
|
fmovew %d0,%fp0 |move the exp to fp0
|
| 63 |
|
|
rts
|
| 64 |
|
|
|
|
| 65 |
|
|
|
|
| 66 |
|
|
| This entry point is used by the unimplemented instruction exception
|
| 67 |
|
|
| handler. It points a0 to the input operand.
|
| 68 |
|
|
|
|
| 69 |
|
|
|
|
| 70 |
|
|
|
|
| 71 |
|
|
| SGETMAN
|
| 72 |
|
|
|
|
| 73 |
|
|
|
|
| 74 |
|
|
| For normalized numbers, leave the mantissa alone, simply load
|
| 75 |
|
|
| with an exponent of +/- $3fff.
|
| 76 |
|
|
|
|
| 77 |
|
|
.global sgetman
|
| 78 |
|
|
sgetman:
|
| 79 |
|
|
movel USER_FPCR(%a6),%d0
|
| 80 |
|
|
andil #0xffffff00,%d0 |clear rounding precision and mode
|
| 81 |
|
|
fmovel %d0,%fpcr |this fpcr setting is used by the 882
|
| 82 |
|
|
movew LOCAL_EX(%a0),%d0 |get the exp (really just want sign bit)
|
| 83 |
|
|
orw #0x7fff,%d0 |clear old exp
|
| 84 |
|
|
bclrl #14,%d0 |make it the new exp +-3fff
|
| 85 |
|
|
movew %d0,LOCAL_EX(%a0) |move the sign & exp back to fsave stack
|
| 86 |
|
|
fmovex (%a0),%fp0 |put new value back in fp0
|
| 87 |
|
|
rts
|
| 88 |
|
|
|
| 89 |
|
|
|
|
| 90 |
|
|
| For denormalized numbers, shift the mantissa until the j-bit = 1,
|
| 91 |
|
|
| then load the exponent with +/1 $3fff.
|
| 92 |
|
|
|
|
| 93 |
|
|
.global sgetmand
|
| 94 |
|
|
sgetmand:
|
| 95 |
|
|
movel LOCAL_HI(%a0),%d0 |load ms mant in d0
|
| 96 |
|
|
movel LOCAL_LO(%a0),%d1 |load ls mant in d1
|
| 97 |
|
|
bsr shft |shift mantissa bits till msbit is set
|
| 98 |
|
|
movel %d0,LOCAL_HI(%a0) |put ms mant back on stack
|
| 99 |
|
|
movel %d1,LOCAL_LO(%a0) |put ls mant back on stack
|
| 100 |
|
|
bras sgetman
|
| 101 |
|
|
|
| 102 |
|
|
|
|
| 103 |
|
|
| SHFT
|
| 104 |
|
|
|
|
| 105 |
|
|
| Shifts the mantissa bits until msbit is set.
|
| 106 |
|
|
| input:
|
| 107 |
|
|
| ms mantissa part in d0
|
| 108 |
|
|
| ls mantissa part in d1
|
| 109 |
|
|
| output:
|
| 110 |
|
|
| shifted bits in d0 and d1
|
| 111 |
|
|
shft:
|
| 112 |
|
|
tstl %d0 |if any bits set in ms mant
|
| 113 |
|
|
bnes upper |then branch
|
| 114 |
|
|
| ;else no bits set in ms mant
|
| 115 |
|
|
tstl %d1 |test if any bits set in ls mant
|
| 116 |
|
|
bnes cont |if set then continue
|
| 117 |
|
|
bras shft_end |else return
|
| 118 |
|
|
cont:
|
| 119 |
|
|
movel %d3,-(%a7) |save d3
|
| 120 |
|
|
exg %d0,%d1 |shift ls mant to ms mant
|
| 121 |
|
|
bfffo %d0{#0:#32},%d3 |find first 1 in ls mant to d0
|
| 122 |
|
|
lsll %d3,%d0 |shift first 1 to integer bit in ms mant
|
| 123 |
|
|
movel (%a7)+,%d3 |restore d3
|
| 124 |
|
|
bras shft_end
|
| 125 |
|
|
upper:
|
| 126 |
|
|
|
| 127 |
|
|
moveml %d3/%d5/%d6,-(%a7) |save registers
|
| 128 |
|
|
bfffo %d0{#0:#32},%d3 |find first 1 in ls mant to d0
|
| 129 |
|
|
lsll %d3,%d0 |shift ms mant until j-bit is set
|
| 130 |
|
|
movel %d1,%d6 |save ls mant in d6
|
| 131 |
|
|
lsll %d3,%d1 |shift ls mant by count
|
| 132 |
|
|
movel #32,%d5
|
| 133 |
|
|
subl %d3,%d5 |sub 32 from shift for ls mant
|
| 134 |
|
|
lsrl %d5,%d6 |shift off all bits but those that will
|
| 135 |
|
|
| ;be shifted into ms mant
|
| 136 |
|
|
orl %d6,%d0 |shift the ls mant bits into the ms mant
|
| 137 |
|
|
moveml (%a7)+,%d3/%d5/%d6 |restore registers
|
| 138 |
|
|
shft_end:
|
| 139 |
|
|
rts
|
| 140 |
|
|
|
| 141 |
|
|
|end
|
