1 * $NetBSD: sgetem.sa,v 1.2 1994/10/26 07:49:45 cgd Exp $ 2 3 * MOTOROLA MICROPROCESSOR & MEMORY TECHNOLOGY GROUP 4 * M68000 Hi-Performance Microprocessor Division 5 * M68040 Software Package 6 * 7 * M68040 Software Package Copyright (c) 1993, 1994 Motorola Inc. 8 * All rights reserved. 9 * 10 * THE SOFTWARE is provided on an "AS IS" basis and without warranty. 11 * To the maximum extent permitted by applicable law, 12 * MOTOROLA DISCLAIMS ALL WARRANTIES WHETHER EXPRESS OR IMPLIED, 13 * INCLUDING IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A 14 * PARTICULAR PURPOSE and any warranty against infringement with 15 * regard to the SOFTWARE (INCLUDING ANY MODIFIED VERSIONS THEREOF) 16 * and any accompanying written materials. 17 * 18 * To the maximum extent permitted by applicable law, 19 * IN NO EVENT SHALL MOTOROLA BE LIABLE FOR ANY DAMAGES WHATSOEVER 20 * (INCLUDING WITHOUT LIMITATION, DAMAGES FOR LOSS OF BUSINESS 21 * PROFITS, BUSINESS INTERRUPTION, LOSS OF BUSINESS INFORMATION, OR 22 * OTHER PECUNIARY LOSS) ARISING OF THE USE OR INABILITY TO USE THE 23 * SOFTWARE. Motorola assumes no responsibility for the maintenance 24 * and support of the SOFTWARE. 25 * 26 * You are hereby granted a copyright license to use, modify, and 27 * distribute the SOFTWARE so long as this entire notice is retained 28 * without alteration in any modified and/or redistributed versions, 29 * and that such modified versions are clearly identified as such. 30 * No licenses are granted by implication, estoppel or otherwise 31 * under any patents or trademarks of Motorola, Inc. 32 33 * 34 * sgetem.sa 3.1 12/10/90 35 * 36 * The entry point sGETEXP returns the exponent portion 37 * of the input argument. The exponent bias is removed 38 * and the exponent value is returned as an extended 39 * precision number in fp0. sGETEXPD handles denormalized 40 * numbers. 41 * 42 * The entry point sGETMAN extracts the mantissa of the 43 * input argument. The mantissa is converted to an 44 * extended precision number and returned in fp0. The 45 * range of the result is [1.0 - 2.0). 46 * 47 * 48 * Input: Double-extended number X in the ETEMP space in 49 * the floating-point save stack. 50 * 51 * Output: The functions return exp(X) or man(X) in fp0. 52 * 53 * Modified: fp0. 54 * 55 56 SGETEM IDNT 2,1 Motorola 040 Floating Point Software Package 57 58 section 8 59 60 include fpsp.h 61 62 xref nrm_set 63 64 * 65 * This entry point is used by the unimplemented instruction exception 66 * handler. It points a0 to the input operand. 67 * 68 * 69 * 70 * SGETEXP 71 * 72 73 xdef sgetexp 74 sgetexp: 75 move.w LOCAL_EX(a0),d0 ;get the exponent 76 bclr.l #15,d0 ;clear the sign bit 77 sub.w #$3fff,d0 ;subtract off the bias 78 fmove.w d0,fp0 ;move the exp to fp0 79 rts 80 81 xdef sgetexpd 82 sgetexpd: 83 bclr.b #sign_bit,LOCAL_EX(a0) 84 bsr nrm_set ;normalize (exp will go negative) 85 move.w LOCAL_EX(a0),d0 ;load resulting exponent into d0 86 sub.w #$3fff,d0 ;subtract off the bias 87 fmove.w d0,fp0 ;move the exp to fp0 88 rts 89 * 90 * 91 * This entry point is used by the unimplemented instruction exception 92 * handler. It points a0 to the input operand. 93 * 94 * 95 * 96 * SGETMAN 97 * 98 * 99 * For normalized numbers, leave the mantissa alone, simply load 100 * with an exponent of +/- $3fff. 101 * 102 xdef sgetman 103 sgetman: 104 move.l USER_FPCR(a6),d0 105 andi.l #$ffffff00,d0 ;clear rounding precision and mode 106 fmove.l d0,fpcr ;this fpcr setting is used by the 882 107 move.w LOCAL_EX(a0),d0 ;get the exp (really just want sign bit) 108 or.w #$7fff,d0 ;clear old exp 109 bclr.l #14,d0 ;make it the new exp +-3fff 110 move.w d0,LOCAL_EX(a0) ;move the sign & exp back to fsave stack 111 fmove.x (a0),fp0 ;put new value back in fp0 112 rts 113 114 * 115 * For denormalized numbers, shift the mantissa until the j-bit = 1, 116 * then load the exponent with +/1 $3fff. 117 * 118 xdef sgetmand 119 sgetmand: 120 move.l LOCAL_HI(a0),d0 ;load ms mant in d0 121 move.l LOCAL_LO(a0),d1 ;load ls mant in d1 122 bsr shft ;shift mantissa bits till msbit is set 123 move.l d0,LOCAL_HI(a0) ;put ms mant back on stack 124 move.l d1,LOCAL_LO(a0) ;put ls mant back on stack 125 bra.b sgetman 126 127 * 128 * SHFT 129 * 130 * Shifts the mantissa bits until msbit is set. 131 * input: 132 * ms mantissa part in d0 133 * ls mantissa part in d1 134 * output: 135 * shifted bits in d0 and d1 136 shft: 137 tst.l d0 ;if any bits set in ms mant 138 bne.b upper ;then branch 139 * ;else no bits set in ms mant 140 tst.l d1 ;test if any bits set in ls mant 141 bne.b cont ;if set then continue 142 bra.b shft_end ;else return 143 cont: 144 move.l d3,-(a7) ;save d3 145 exg d0,d1 ;shift ls mant to ms mant 146 bfffo d0{0:32},d3 ;find first 1 in ls mant to d0 147 lsl.l d3,d0 ;shift first 1 to integer bit in ms mant 148 move.l (a7)+,d3 ;restore d3 149 bra.b shft_end 150 upper: 151 152 movem.l d3/d5/d6,-(a7) ;save registers 153 bfffo d0{0:32},d3 ;find first 1 in ls mant to d0 154 lsl.l d3,d0 ;shift ms mant until j-bit is set 155 move.l d1,d6 ;save ls mant in d6 156 lsl.l d3,d1 ;shift ls mant by count 157 move.l #32,d5 158 sub.l d3,d5 ;sub 32 from shift for ls mant 159 lsr.l d5,d6 ;shift off all bits but those that will 160 * ;be shifted into ms mant 161 or.l d6,d0 ;shift the ls mant bits into the ms mant 162 movem.l (a7)+,d3/d5/d6 ;restore registers 163 shft_end: 164 rts 165 166 end 167
Indexes created Tue Oct 14 01:09:49 GMT 2025