1 |
2 | scale.sa 3.3 7/30/91
3 |
4 | The entry point sSCALE computes the de
5 | scaled by the source operand. If the
6 | the source operand is (>= 2^14) an ove
7 | is returned.
8 |
9 | The entry point sscale is called from
10 | the fscale unimplemented instruction.
11 |
12 | Input: Double-extended destination ope
13 | double-extended source operand
14 |
15 | Output: The function returns scale(X,Y
16 |
17 | Modifies: fp0.
18 |
19 | Algorithm:
20 |
21 | Copyright (C) Motorola, Inc. 1
22 | All Rights Reserved
23 |
24 | For details on the license for this fi
25 | file, README, in this same directory.
26
27 |SCALE idnt 2,1 | Motorola 040 Floating
28
29 |section 8
30
31 #include "fpsp.h"
32
33 |xref t_ovfl2
34 |xref t_unfl
35 |xref round
36 |xref t_resdnrm
37
38 SRC_BNDS: .short 0x3fff,0x400c
39
40 |
41 | This entry point is used by the unimplemente
42 | handler.
43 |
44 |
45 |
46 | FSCALE
47 |
48 .global sscale
49 sscale:
50 fmovel #0,%fpcr
51 clrl %d1
52 movew FPTEMP(%a6),%d1 |get d
53 smi L_SCR1(%a6) |use L
54 andil #0x7fff,%d1 |strip
55 movew ETEMP(%a6),%d0 |check
56 andiw #0x7fff,%d0 |clr s
57 cmp2w SRC_BNDS,%d0
58 bccs src_in
59 cmpiw #0x400c,%d0 |test
60 bge src_out
61 |
62 | The source input is below 1, so we check for
63 | and set unfl.
64 |
65 src_small:
66 moveb DTAG(%a6),%d0
67 andib #0xe0,%d0
68 tstb %d0
69 beqs no_denorm
70 st STORE_FLG(%a6) |dest
71 orl #unfl_mask,USER_FPSR(%
72 den_done:
73 leal FPTEMP(%a6),%a0
74 bra t_resdnrm
75 no_denorm:
76 fmovel USER_FPCR(%a6),%FPCR
77 fmovex FPTEMP(%a6),%fp0
78 rts
79
80
81 |
82 | Source is within 2^14 range. To perform the
83 | move it to d0.
84 |
85 src_in:
86 fmovex ETEMP(%a6),%fp0 |move
87 fmovel #rz_mode,%fpcr |force
88 fmovel %fp0,%d0
89 fmovel #0,%FPSR
90 tstw ETEMP(%a6) |check
91 blt src_neg
92 |
93 | Source is positive. Add the src to the dest
94 | The result can be denormalized, if src = 0,
95 | if the result of the add sets a bit in the u
96 |
97 src_pos:
98 tstw %d1 |check
99 beq dst_dnrm
100 addl %d0,%d1 |add s
101 beqs denorm |if ze
102 cmpil #0x7fff,%d1 |test
103 bges ovfl
104 tstb L_SCR1(%a6)
105 beqs spos_pos
106 orw #0x8000,%d1
107 spos_pos:
108 movew %d1,FPTEMP(%a6) |resul
109 fmovel USER_FPCR(%a6),%FPCR
110 fmovex FPTEMP(%a6),%fp0
111 rts
112 ovfl:
113 tstb L_SCR1(%a6)
114 beqs sovl_pos
115 orw #0x8000,%d1
116 sovl_pos:
117 movew FPTEMP(%a6),ETEMP(%a6)
118 movel FPTEMP_HI(%a6),ETEMP_H
119 movel FPTEMP_LO(%a6),ETEMP_L
120 bra t_ovfl2
121
122 denorm:
123 tstb L_SCR1(%a6)
124 beqs den_pos
125 orw #0x8000,%d1
126 den_pos:
127 tstl FPTEMP_HI(%a6) |check
128 blts nden_exit |if se
129 movew %d1,ETEMP(%a6) |input
130 movel FPTEMP_HI(%a6),ETEMP_H
131 movel FPTEMP_LO(%a6),ETEMP_L
132 orl #unfl_bit,USER_FPSR(%a
133 leal ETEMP(%a6),%a0
134 bra t_resdnrm
135 nden_exit:
136 movew %d1,FPTEMP(%a6) |resul
137 fmovel USER_FPCR(%a6),%FPCR
138 fmovex FPTEMP(%a6),%fp0
139 rts
140
141 |
142 | Source is negative. Add the src to the dest
143 | (The result exponent will be reduced). The
144 | denormalized.
145 |
146 src_neg:
147 addl %d0,%d1 |add s
148 beqs denorm |if ze
149 blts fix_dnrm |if ne
150 | ;needi
151 tstb L_SCR1(%a6)
152 beqs sneg_pos
153 orw #0x8000,%d1
154 sneg_pos:
155 movew %d1,FPTEMP(%a6) |resul
156 fmovel USER_FPCR(%a6),%FPCR
157 fmovex FPTEMP(%a6),%fp0
158 rts
159
160
161 |
162 | The result exponent is below denorm value.
163 | underflow and force zero if true. If not, t
164 | mantissa right until a zero exponent exists.
165 |
166 fix_dnrm:
167 cmpiw #0xffc0,%d1 |lower
168 blt fix_unfl |if lo
169 movew %d1,%d0 |use d
170 movel %d2,-(%a7) |free
171 movel FPTEMP_HI(%a6),%d1
172 movel FPTEMP_LO(%a6),%d2
173 clrl L_SCR2(%a6)
174 fix_loop:
175 addw #1,%d0 |drive
176 lsrl #1,%d1 |while
177 roxrl #1,%d2 |manti
178 bccs no_carry
179 st L_SCR2(%a6) |use L
180 no_carry:
181 tstw %d0 |it is
182 blts fix_loop |d0 is
183 tstb L_SCR2(%a6)
184 beqs tst_zero
185 orl #unfl_inx_mask,USER_FP
186 | ;set u
187 |
188 | Test for zero. If zero, simply use fmove to
189 | to the fpu.
190 |
191 tst_zero:
192 clrw FPTEMP_EX(%a6)
193 tstb L_SCR1(%a6) |test
194 beqs tst_con
195 orw #0x8000,FPTEMP_EX(%a6)
196 tst_con:
197 movel %d1,FPTEMP_HI(%a6)
198 movel %d2,FPTEMP_LO(%a6)
199 movel (%a7)+,%d2
200 tstl %d1
201 bnes not_zero
202 tstl FPTEMP_LO(%a6)
203 bnes not_zero
204 |
205 | Result is zero. Check for rounding mode to
206 | mode is rp, and the zero is positive, return
207 | If the mode is rm, and the zero is negative,
208 | negative denorm.
209 |
210 btstb #5,FPCR_MODE(%a6) |tes
211 beqs no_dir
212 btstb #4,FPCR_MODE(%a6) |che
213 beqs zer_rm
214 zer_rp:
215 tstb L_SCR1(%a6) |check
216 bnes no_dir |if se
217 movel #1,FPTEMP_LO(%a6) |set
218 bras sm_dnrm
219 zer_rm:
220 tstb L_SCR1(%a6) |check
221 beqs no_dir |if cl
222 movel #1,FPTEMP_LO(%a6) |set
223 orl #neg_mask,USER_FPSR(%a
224 bras sm_dnrm
225 no_dir:
226 fmovel USER_FPCR(%a6),%FPCR
227 fmovex FPTEMP(%a6),%fp0
228 rts
229
230 |
231 | The rounding mode changed the zero to a smal
232 | t_resdnrm with exceptional operand in ETEMP.
233 |
234 sm_dnrm:
235 movel FPTEMP_EX(%a6),ETEMP_E
236 movel FPTEMP_HI(%a6),ETEMP_H
237 movel FPTEMP_LO(%a6),ETEMP_L
238 leal ETEMP(%a6),%a0
239 bra t_resdnrm
240
241 |
242 | Result is still denormalized.
243 |
244 not_zero:
245 orl #unfl_mask,USER_FPSR(%
246 tstb L_SCR1(%a6) |check
247 beqs fix_exit
248 orl #neg_mask,USER_FPSR(%a
249 fix_exit:
250 bras sm_dnrm
251
252
253 |
254 | The result has underflowed to zero. Return z
255 | unfl, aunfl, and ainex.
256 |
257 fix_unfl:
258 orl #unfl_inx_mask,USER_FP
259 btstb #5,FPCR_MODE(%a6) |tes
260 beqs no_dir2
261 btstb #4,FPCR_MODE(%a6) |che
262 beqs zer_rm2
263 zer_rp2:
264 tstb L_SCR1(%a6) |check
265 bnes no_dir2 |if se
266 clrl FPTEMP_EX(%a6)
267 clrl FPTEMP_HI(%a6)
268 movel #1,FPTEMP_LO(%a6) |set
269 bras sm_dnrm |retur
270 zer_rm2:
271 tstb L_SCR1(%a6) |check
272 beqs no_dir2 |if cl
273 movew #0x8000,FPTEMP_EX(%a6)
274 clrl FPTEMP_HI(%a6)
275 movel #1,FPTEMP_LO(%a6) |set
276 orl #neg_mask,USER_FPSR(%a
277 bra sm_dnrm |retur
278
279 no_dir2:
280 tstb L_SCR1(%a6)
281 bges pos_zero
282 neg_zero:
283 clrl FP_SCR1(%a6) |clear
284 clrl FP_SCR1+4(%a6) |for g
285 clrl FP_SCR1+8(%a6)
286 fmoves #0x80000000,%fp0
287 rts
288 pos_zero:
289 clrl FP_SCR1(%a6) |clear
290 clrl FP_SCR1+4(%a6) |for g
291 clrl FP_SCR1+8(%a6)
292 fmoves #0x00000000,%fp0
293 rts
294
295 |
296 | The destination is a denormalized number. I
297 | by first shifting the bits in the mantissa u
298 | then adding the remainder of the source to t
299 |
300 dst_dnrm:
301 moveml %d2/%d3,-(%a7)
302 movew FPTEMP_EX(%a6),%d1
303 movel FPTEMP_HI(%a6),%d2
304 movel FPTEMP_LO(%a6),%d3
305 dst_loop:
306 tstl %d2 |test
307 blts dst_norm |exit
308 tstl %d0 |other
309 beqs dst_fin |if ze
310 subil #1,%d0 |dec s
311 lsll #1,%d3
312 roxll #1,%d2
313 bras dst_loop
314 |
315 | Destination became normalized. Simply add t
316 | portion of the src to the exponent.
317 |
318 dst_norm:
319 addw %d0,%d1 |dst i
320 tstb L_SCR1(%a6)
321 beqs dnrm_pos
322 orl #0x8000,%d1
323 dnrm_pos:
324 movemw %d1,FPTEMP_EX(%a6)
325 moveml %d2,FPTEMP_HI(%a6)
326 moveml %d3,FPTEMP_LO(%a6)
327 fmovel USER_FPCR(%a6),%FPCR
328 fmovex FPTEMP(%a6),%fp0
329 moveml (%a7)+,%d2/%d3
330 rts
331
332 |
333 | Destination remained denormalized. Call t_e
334 | exceptional operand in ETEMP.
335 |
336 dst_fin:
337 tstb L_SCR1(%a6) |check
338 beqs dst_exit
339 orl #neg_mask,USER_FPSR(%a
340 orl #0x8000,%d1
341 dst_exit:
342 movemw %d1,ETEMP_EX(%a6)
343 moveml %d2,ETEMP_HI(%a6)
344 moveml %d3,ETEMP_LO(%a6)
345 orl #unfl_mask,USER_FPSR(%
346 moveml (%a7)+,%d2/%d3
347 leal ETEMP(%a6),%a0
348 bra t_resdnrm
349
350 |
351 | Source is outside of 2^14 range. Test the s
352 | to the appropriate exception handler.
353 |
354 src_out:
355 tstb L_SCR1(%a6)
356 beqs scro_pos
357 orl #0x8000,%d1
358 scro_pos:
359 movel FPTEMP_HI(%a6),ETEMP_H
360 movel FPTEMP_LO(%a6),ETEMP_L
361 tstw ETEMP(%a6)
362 blts res_neg
363 res_pos:
364 movew %d1,ETEMP(%a6) |resul
365 bra t_ovfl2
366 res_neg:
367 movew %d1,ETEMP(%a6) |resul
368 leal ETEMP(%a6),%a0
369 bra t_unfl
370 |end
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