Loading...
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 | | | scale.sa 3.3 7/30/91 | | The entry point sSCALE computes the destination operand | scaled by the source operand. If the absolute value of | the source operand is (>= 2^14) an overflow or underflow | is returned. | | The entry point sscale is called from do_func to emulate | the fscale unimplemented instruction. | | Input: Double-extended destination operand in FPTEMP, | double-extended source operand in ETEMP. | | Output: The function returns scale(X,Y) to fp0. | | Modifies: fp0. | | Algorithm: | | 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. |SCALE idnt 2,1 | Motorola 040 Floating Point Software Package |section 8 #include "fpsp.h" |xref t_ovfl2 |xref t_unfl |xref round |xref t_resdnrm SRC_BNDS: .short 0x3fff,0x400c | | This entry point is used by the unimplemented instruction exception | handler. | | | | FSCALE | .global sscale sscale: fmovel #0,%fpcr |clr user enabled exc clrl %d1 movew FPTEMP(%a6),%d1 |get dest exponent smi L_SCR1(%a6) |use L_SCR1 to hold sign andil #0x7fff,%d1 |strip sign movew ETEMP(%a6),%d0 |check src bounds andiw #0x7fff,%d0 |clr sign bit cmp2w SRC_BNDS,%d0 bccs src_in cmpiw #0x400c,%d0 |test for too large bge src_out | | The source input is below 1, so we check for denormalized numbers | and set unfl. | src_small: moveb DTAG(%a6),%d0 andib #0xe0,%d0 tstb %d0 beqs no_denorm st STORE_FLG(%a6) |dest already contains result orl #unfl_mask,USER_FPSR(%a6) |set UNFL den_done: leal FPTEMP(%a6),%a0 bra t_resdnrm no_denorm: fmovel USER_FPCR(%a6),%FPCR fmovex FPTEMP(%a6),%fp0 |simply return dest rts | | Source is within 2^14 range. To perform the int operation, | move it to d0. | src_in: fmovex ETEMP(%a6),%fp0 |move in src for int fmovel #rz_mode,%fpcr |force rz for src conversion fmovel %fp0,%d0 |int src to d0 fmovel #0,%FPSR |clr status from above tstw ETEMP(%a6) |check src sign blt src_neg | | Source is positive. Add the src to the dest exponent. | The result can be denormalized, if src = 0, or overflow, | if the result of the add sets a bit in the upper word. | src_pos: tstw %d1 |check for denorm beq dst_dnrm addl %d0,%d1 |add src to dest exp beqs denorm |if zero, result is denorm cmpil #0x7fff,%d1 |test for overflow bges ovfl tstb L_SCR1(%a6) beqs spos_pos orw #0x8000,%d1 spos_pos: movew %d1,FPTEMP(%a6) |result in FPTEMP fmovel USER_FPCR(%a6),%FPCR fmovex FPTEMP(%a6),%fp0 |write result to fp0 rts ovfl: tstb L_SCR1(%a6) beqs sovl_pos orw #0x8000,%d1 sovl_pos: movew FPTEMP(%a6),ETEMP(%a6) |result in ETEMP movel FPTEMP_HI(%a6),ETEMP_HI(%a6) movel FPTEMP_LO(%a6),ETEMP_LO(%a6) bra t_ovfl2 denorm: tstb L_SCR1(%a6) beqs den_pos orw #0x8000,%d1 den_pos: tstl FPTEMP_HI(%a6) |check j bit blts nden_exit |if set, not denorm movew %d1,ETEMP(%a6) |input expected in ETEMP movel FPTEMP_HI(%a6),ETEMP_HI(%a6) movel FPTEMP_LO(%a6),ETEMP_LO(%a6) orl #unfl_bit,USER_FPSR(%a6) |set unfl leal ETEMP(%a6),%a0 bra t_resdnrm nden_exit: movew %d1,FPTEMP(%a6) |result in FPTEMP fmovel USER_FPCR(%a6),%FPCR fmovex FPTEMP(%a6),%fp0 |write result to fp0 rts | | Source is negative. Add the src to the dest exponent. | (The result exponent will be reduced). The result can be | denormalized. | src_neg: addl %d0,%d1 |add src to dest beqs denorm |if zero, result is denorm blts fix_dnrm |if negative, result is | ;needing denormalization tstb L_SCR1(%a6) beqs sneg_pos orw #0x8000,%d1 sneg_pos: movew %d1,FPTEMP(%a6) |result in FPTEMP fmovel USER_FPCR(%a6),%FPCR fmovex FPTEMP(%a6),%fp0 |write result to fp0 rts | | The result exponent is below denorm value. Test for catastrophic | underflow and force zero if true. If not, try to shift the | mantissa right until a zero exponent exists. | fix_dnrm: cmpiw #0xffc0,%d1 |lower bound for normalization blt fix_unfl |if lower, catastrophic unfl movew %d1,%d0 |use d0 for exp movel %d2,-(%a7) |free d2 for norm movel FPTEMP_HI(%a6),%d1 movel FPTEMP_LO(%a6),%d2 clrl L_SCR2(%a6) fix_loop: addw #1,%d0 |drive d0 to 0 lsrl #1,%d1 |while shifting the roxrl #1,%d2 |mantissa to the right bccs no_carry st L_SCR2(%a6) |use L_SCR2 to capture inex no_carry: tstw %d0 |it is finished when blts fix_loop |d0 is zero or the mantissa tstb L_SCR2(%a6) beqs tst_zero orl #unfl_inx_mask,USER_FPSR(%a6) | ;set unfl, aunfl, ainex | | Test for zero. If zero, simply use fmove to return +/- zero | to the fpu. | tst_zero: clrw FPTEMP_EX(%a6) tstb L_SCR1(%a6) |test for sign beqs tst_con orw #0x8000,FPTEMP_EX(%a6) |set sign bit tst_con: movel %d1,FPTEMP_HI(%a6) movel %d2,FPTEMP_LO(%a6) movel (%a7)+,%d2 tstl %d1 bnes not_zero tstl FPTEMP_LO(%a6) bnes not_zero | | Result is zero. Check for rounding mode to set lsb. If the | mode is rp, and the zero is positive, return smallest denorm. | If the mode is rm, and the zero is negative, return smallest | negative denorm. | btstb #5,FPCR_MODE(%a6) |test if rm or rp beqs no_dir btstb #4,FPCR_MODE(%a6) |check which one beqs zer_rm zer_rp: tstb L_SCR1(%a6) |check sign bnes no_dir |if set, neg op, no inc movel #1,FPTEMP_LO(%a6) |set lsb bras sm_dnrm zer_rm: tstb L_SCR1(%a6) |check sign beqs no_dir |if clr, neg op, no inc movel #1,FPTEMP_LO(%a6) |set lsb orl #neg_mask,USER_FPSR(%a6) |set N bras sm_dnrm no_dir: fmovel USER_FPCR(%a6),%FPCR fmovex FPTEMP(%a6),%fp0 |use fmove to set cc's rts | | The rounding mode changed the zero to a smallest denorm. Call | t_resdnrm with exceptional operand in ETEMP. | sm_dnrm: movel FPTEMP_EX(%a6),ETEMP_EX(%a6) movel FPTEMP_HI(%a6),ETEMP_HI(%a6) movel FPTEMP_LO(%a6),ETEMP_LO(%a6) leal ETEMP(%a6),%a0 bra t_resdnrm | | Result is still denormalized. | not_zero: orl #unfl_mask,USER_FPSR(%a6) |set unfl tstb L_SCR1(%a6) |check for sign beqs fix_exit orl #neg_mask,USER_FPSR(%a6) |set N fix_exit: bras sm_dnrm | | The result has underflowed to zero. Return zero and set | unfl, aunfl, and ainex. | fix_unfl: orl #unfl_inx_mask,USER_FPSR(%a6) btstb #5,FPCR_MODE(%a6) |test if rm or rp beqs no_dir2 btstb #4,FPCR_MODE(%a6) |check which one beqs zer_rm2 zer_rp2: tstb L_SCR1(%a6) |check sign bnes no_dir2 |if set, neg op, no inc clrl FPTEMP_EX(%a6) clrl FPTEMP_HI(%a6) movel #1,FPTEMP_LO(%a6) |set lsb bras sm_dnrm |return smallest denorm zer_rm2: tstb L_SCR1(%a6) |check sign beqs no_dir2 |if clr, neg op, no inc movew #0x8000,FPTEMP_EX(%a6) clrl FPTEMP_HI(%a6) movel #1,FPTEMP_LO(%a6) |set lsb orl #neg_mask,USER_FPSR(%a6) |set N bra sm_dnrm |return smallest denorm no_dir2: tstb L_SCR1(%a6) bges pos_zero neg_zero: clrl FP_SCR1(%a6) |clear the exceptional operand clrl FP_SCR1+4(%a6) |for gen_except. clrl FP_SCR1+8(%a6) fmoves #0x80000000,%fp0 rts pos_zero: clrl FP_SCR1(%a6) |clear the exceptional operand clrl FP_SCR1+4(%a6) |for gen_except. clrl FP_SCR1+8(%a6) fmoves #0x00000000,%fp0 rts | | The destination is a denormalized number. It must be handled | by first shifting the bits in the mantissa until it is normalized, | then adding the remainder of the source to the exponent. | dst_dnrm: moveml %d2/%d3,-(%a7) movew FPTEMP_EX(%a6),%d1 movel FPTEMP_HI(%a6),%d2 movel FPTEMP_LO(%a6),%d3 dst_loop: tstl %d2 |test for normalized result blts dst_norm |exit loop if so tstl %d0 |otherwise, test shift count beqs dst_fin |if zero, shifting is done subil #1,%d0 |dec src lsll #1,%d3 roxll #1,%d2 bras dst_loop | | Destination became normalized. Simply add the remaining | portion of the src to the exponent. | dst_norm: addw %d0,%d1 |dst is normalized; add src tstb L_SCR1(%a6) beqs dnrm_pos orl #0x8000,%d1 dnrm_pos: movemw %d1,FPTEMP_EX(%a6) moveml %d2,FPTEMP_HI(%a6) moveml %d3,FPTEMP_LO(%a6) fmovel USER_FPCR(%a6),%FPCR fmovex FPTEMP(%a6),%fp0 moveml (%a7)+,%d2/%d3 rts | | Destination remained denormalized. Call t_excdnrm with | exceptional operand in ETEMP. | dst_fin: tstb L_SCR1(%a6) |check for sign beqs dst_exit orl #neg_mask,USER_FPSR(%a6) |set N orl #0x8000,%d1 dst_exit: movemw %d1,ETEMP_EX(%a6) moveml %d2,ETEMP_HI(%a6) moveml %d3,ETEMP_LO(%a6) orl #unfl_mask,USER_FPSR(%a6) |set unfl moveml (%a7)+,%d2/%d3 leal ETEMP(%a6),%a0 bra t_resdnrm | | Source is outside of 2^14 range. Test the sign and branch | to the appropriate exception handler. | src_out: tstb L_SCR1(%a6) beqs scro_pos orl #0x8000,%d1 scro_pos: movel FPTEMP_HI(%a6),ETEMP_HI(%a6) movel FPTEMP_LO(%a6),ETEMP_LO(%a6) tstw ETEMP(%a6) blts res_neg res_pos: movew %d1,ETEMP(%a6) |result in ETEMP bra t_ovfl2 res_neg: movew %d1,ETEMP(%a6) |result in ETEMP leal ETEMP(%a6),%a0 bra t_unfl |end |