summaryrefslogtreecommitdiff
path: root/arch/m68k/fpsp040/scale.S
blob: 04829dd4f1f48172b978a7d582fcd8f57067cb7b (plain)
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