sgetem.sa revision 1.1
1 * MOTOROLA MICROPROCESSOR & MEMORY TECHNOLOGY GROUP 2 * M68000 Hi-Performance Microprocessor Division 3 * M68040 Software Package 4 * 5 * M68040 Software Package Copyright (c) 1993, 1994 Motorola Inc. 6 * All rights reserved. 7 * 8 * THE SOFTWARE is provided on an "AS IS" basis and without warranty. 9 * To the maximum extent permitted by applicable law, 10 * MOTOROLA DISCLAIMS ALL WARRANTIES WHETHER EXPRESS OR IMPLIED, 11 * INCLUDING IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A 12 * PARTICULAR PURPOSE and any warranty against infringement with 13 * regard to the SOFTWARE (INCLUDING ANY MODIFIED VERSIONS THEREOF) 14 * and any accompanying written materials. 15 * 16 * To the maximum extent permitted by applicable law, 17 * IN NO EVENT SHALL MOTOROLA BE LIABLE FOR ANY DAMAGES WHATSOEVER 18 * (INCLUDING WITHOUT LIMITATION, DAMAGES FOR LOSS OF BUSINESS 19 * PROFITS, BUSINESS INTERRUPTION, LOSS OF BUSINESS INFORMATION, OR 20 * OTHER PECUNIARY LOSS) ARISING OF THE USE OR INABILITY TO USE THE 21 * SOFTWARE. Motorola assumes no responsibility for the maintenance 22 * and support of the SOFTWARE. 23 * 24 * You are hereby granted a copyright license to use, modify, and 25 * distribute the SOFTWARE so long as this entire notice is retained 26 * without alteration in any modified and/or redistributed versions, 27 * and that such modified versions are clearly identified as such. 28 * No licenses are granted by implication, estoppel or otherwise 29 * under any patents or trademarks of Motorola, Inc. 30 31 * 32 * sgetem.sa 3.1 12/10/90 33 * 34 * The entry point sGETEXP returns the exponent portion 35 * of the input argument. The exponent bias is removed 36 * and the exponent value is returned as an extended 37 * precision number in fp0. sGETEXPD handles denormalized 38 * numbers. 39 * 40 * The entry point sGETMAN extracts the mantissa of the 41 * input argument. The mantissa is converted to an 42 * extended precision number and returned in fp0. The 43 * range of the result is [1.0 - 2.0). 44 * 45 * 46 * Input: Double-extended number X in the ETEMP space in 47 * the floating-point save stack. 48 * 49 * Output: The functions return exp(X) or man(X) in fp0. 50 * 51 * Modified: fp0. 52 * 53 54 SGETEM IDNT 2,1 Motorola 040 Floating Point Software Package 55 56 section 8 57 58 include fpsp.h 59 60 xref nrm_set 61 62 * 63 * This entry point is used by the unimplemented instruction exception 64 * handler. It points a0 to the input operand. 65 * 66 * 67 * 68 * SGETEXP 69 * 70 71 xdef sgetexp 72 sgetexp: 73 move.w LOCAL_EX(a0),d0 ;get the exponent 74 bclr.l #15,d0 ;clear the sign bit 75 sub.w #$3fff,d0 ;subtract off the bias 76 fmove.w d0,fp0 ;move the exp to fp0 77 rts 78 79 xdef sgetexpd 80 sgetexpd: 81 bclr.b #sign_bit,LOCAL_EX(a0) 82 bsr nrm_set ;normalize (exp will go negative) 83 move.w LOCAL_EX(a0),d0 ;load resulting exponent into d0 84 sub.w #$3fff,d0 ;subtract off the bias 85 fmove.w d0,fp0 ;move the exp to fp0 86 rts 87 * 88 * 89 * This entry point is used by the unimplemented instruction exception 90 * handler. It points a0 to the input operand. 91 * 92 * 93 * 94 * SGETMAN 95 * 96 * 97 * For normalized numbers, leave the mantissa alone, simply load 98 * with an exponent of +/- $3fff. 99 * 100 xdef sgetman 101 sgetman: 102 move.l USER_FPCR(a6),d0 103 andi.l #$ffffff00,d0 ;clear rounding precision and mode 104 fmove.l d0,fpcr ;this fpcr setting is used by the 882 105 move.w LOCAL_EX(a0),d0 ;get the exp (really just want sign bit) 106 or.w #$7fff,d0 ;clear old exp 107 bclr.l #14,d0 ;make it the new exp +-3fff 108 move.w d0,LOCAL_EX(a0) ;move the sign & exp back to fsave stack 109 fmove.x (a0),fp0 ;put new value back in fp0 110 rts 111 112 * 113 * For denormalized numbers, shift the mantissa until the j-bit = 1, 114 * then load the exponent with +/1 $3fff. 115 * 116 xdef sgetmand 117 sgetmand: 118 move.l LOCAL_HI(a0),d0 ;load ms mant in d0 119 move.l LOCAL_LO(a0),d1 ;load ls mant in d1 120 bsr shft ;shift mantissa bits till msbit is set 121 move.l d0,LOCAL_HI(a0) ;put ms mant back on stack 122 move.l d1,LOCAL_LO(a0) ;put ls mant back on stack 123 bra.b sgetman 124 125 * 126 * SHFT 127 * 128 * Shifts the mantissa bits until msbit is set. 129 * input: 130 * ms mantissa part in d0 131 * ls mantissa part in d1 132 * output: 133 * shifted bits in d0 and d1 134 shft: 135 tst.l d0 ;if any bits set in ms mant 136 bne.b upper ;then branch 137 * ;else no bits set in ms mant 138 tst.l d1 ;test if any bits set in ls mant 139 bne.b cont ;if set then continue 140 bra.b shft_end ;else return 141 cont: 142 move.l d3,-(a7) ;save d3 143 exg d0,d1 ;shift ls mant to ms mant 144 bfffo d0{0:32},d3 ;find first 1 in ls mant to d0 145 lsl.l d3,d0 ;shift first 1 to integer bit in ms mant 146 move.l (a7)+,d3 ;restore d3 147 bra.b shft_end 148 upper: 149 150 movem.l d3/d5/d6,-(a7) ;save registers 151 bfffo d0{0:32},d3 ;find first 1 in ls mant to d0 152 lsl.l d3,d0 ;shift ms mant until j-bit is set 153 move.l d1,d6 ;save ls mant in d6 154 lsl.l d3,d1 ;shift ls mant by count 155 move.l #32,d5 156 sub.l d3,d5 ;sub 32 from shift for ls mant 157 lsr.l d5,d6 ;shift off all bits but those that will 158 * ;be shifted into ms mant 159 or.l d6,d0 ;shift the ls mant bits into the ms mant 160 movem.l (a7)+,d3/d5/d6 ;restore registers 161 shft_end: 162 rts 163 164 end 165
Indexes created Fri Oct 31 11:10:07 GMT 2025