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27 | // THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA |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