x_store.S

  1|
  2|	x_store.sa 3.2 1/24/91
  3|
  4|	store --- store operand to memory or register
  5|
  6|	Used by underflow and overflow handlers.
  7|
  8|	a6 = points to fp value to be stored.
  9|
 10
 11|		Copyright (C) Motorola, Inc. 1990
 12|			All Rights Reserved
 13|
 14|       For details on the license for this file, please see the
 15|       file, README, in this same directory.
 16
 17X_STORE:	|idnt    2,1 | Motorola 040 Floating Point Software Package
 18
 19	|section	8
 20
 21fpreg_mask:
 22	.byte	0x80,0x40,0x20,0x10,0x08,0x04,0x02,0x01
 23
 24#include "fpsp.h"
 25
 26	|xref	mem_write
 27	|xref	get_fline
 28	|xref	g_opcls
 29	|xref	g_dfmtou
 30	|xref	reg_dest
 31
 32	.global	dest_ext
 33	.global	dest_dbl
 34	.global	dest_sgl
 35
 36	.global	store
 37store:
 38	btstb	#E3,E_BYTE(%a6)
 39	beqs	E1_sto
 40E3_sto:
 41	movel	CMDREG3B(%a6),%d0
 42	bfextu	%d0{#6:#3},%d0		|isolate dest. reg from cmdreg3b
 43sto_fp:
 44	lea	fpreg_mask,%a1
 45	moveb	(%a1,%d0.w),%d0		|convert reg# to dynamic register mask
 46	tstb	LOCAL_SGN(%a0)
 47	beqs	is_pos
 48	bsetb	#sign_bit,LOCAL_EX(%a0)
 49is_pos:
 50	fmovemx (%a0),%d0		|move to correct register
 51|
 52|	if fp0-fp3 is being modified, we must put a copy
 53|	in the USER_FPn variable on the stack because all exception
 54|	handlers restore fp0-fp3 from there.
 55|
 56	cmpb	#0x80,%d0
 57	bnes	not_fp0
 58	fmovemx %fp0-%fp0,USER_FP0(%a6)
 59	rts
 60not_fp0:
 61	cmpb	#0x40,%d0
 62	bnes	not_fp1
 63	fmovemx %fp1-%fp1,USER_FP1(%a6)
 64	rts
 65not_fp1:
 66	cmpb	#0x20,%d0
 67	bnes	not_fp2
 68	fmovemx %fp2-%fp2,USER_FP2(%a6)
 69	rts
 70not_fp2:
 71	cmpb	#0x10,%d0
 72	bnes	not_fp3
 73	fmovemx %fp3-%fp3,USER_FP3(%a6)
 74	rts
 75not_fp3:
 76	rts
 77
 78E1_sto:
 79	bsrl	g_opcls		|returns opclass in d0
 80	cmpib	#3,%d0
 81	beq	opc011		|branch if opclass 3
 82	movel	CMDREG1B(%a6),%d0
 83	bfextu	%d0{#6:#3},%d0	|extract destination register
 84	bras	sto_fp
 85
 86opc011:
 87	bsrl	g_dfmtou	|returns dest format in d0
 88|				;ext=00, sgl=01, dbl=10
 89	movel	%a0,%a1		|save source addr in a1
 90	movel	EXC_EA(%a6),%a0	|get the address
 91	cmpil	#0,%d0		|if dest format is extended
 92	beq	dest_ext	|then branch
 93	cmpil	#1,%d0		|if dest format is single
 94	beq	dest_sgl	|then branch
 95|
 96|	fall through to dest_dbl
 97|
 98
 99|
100|	dest_dbl --- write double precision value to user space
101|
102|Input
103|	a0 -> destination address
104|	a1 -> source in extended precision
105|Output
106|	a0 -> destroyed
107|	a1 -> destroyed
108|	d0 -> 0
109|
110|Changes extended precision to double precision.
111| Note: no attempt is made to round the extended value to double.
112|	dbl_sign = ext_sign
113|	dbl_exp = ext_exp - $3fff(ext bias) + $7ff(dbl bias)
114|	get rid of ext integer bit
115|	dbl_mant = ext_mant{62:12}
116|
117|		---------------   ---------------    ---------------
118|  extended ->  |s|    exp    |   |1| ms mant   |    | ls mant     |
119|		---------------   ---------------    ---------------
120|		 95	    64    63 62	      32      31     11	  0
121|				     |			     |
122|				     |			     |
123|				     |			     |
124|			             v			     v
125|			      ---------------   ---------------
126|  double   ->		      |s|exp| mant  |   |  mant       |
127|			      ---------------   ---------------
128|			      63     51   32   31	       0
129|
130dest_dbl:
131	clrl	%d0		|clear d0
132	movew	LOCAL_EX(%a1),%d0	|get exponent
133	subw	#0x3fff,%d0	|subtract extended precision bias
134	cmpw	#0x4000,%d0	|check if inf
135	beqs	inf		|if so, special case
136	addw	#0x3ff,%d0	|add double precision bias
137	swap	%d0		|d0 now in upper word
138	lsll	#4,%d0		|d0 now in proper place for dbl prec exp
139	tstb	LOCAL_SGN(%a1)
140	beqs	get_mant	|if positive, go process mantissa
141	bsetl	#31,%d0		|if negative, put in sign information
142|				; before continuing
143	bras	get_mant	|go process mantissa
144inf:
145	movel	#0x7ff00000,%d0	|load dbl inf exponent
146	clrl	LOCAL_HI(%a1)	|clear msb
147	tstb	LOCAL_SGN(%a1)
148	beqs	dbl_inf		|if positive, go ahead and write it
149	bsetl	#31,%d0		|if negative put in sign information
150dbl_inf:
151	movel	%d0,LOCAL_EX(%a1)	|put the new exp back on the stack
152	bras	dbl_wrt
153get_mant:
154	movel	LOCAL_HI(%a1),%d1	|get ms mantissa
155	bfextu	%d1{#1:#20},%d1	|get upper 20 bits of ms
156	orl	%d1,%d0		|put these bits in ms word of double
157	movel	%d0,LOCAL_EX(%a1)	|put the new exp back on the stack
158	movel	LOCAL_HI(%a1),%d1	|get ms mantissa
159	movel	#21,%d0		|load shift count
160	lsll	%d0,%d1		|put lower 11 bits in upper bits
161	movel	%d1,LOCAL_HI(%a1)	|build lower lword in memory
162	movel	LOCAL_LO(%a1),%d1	|get ls mantissa
163	bfextu	%d1{#0:#21},%d0	|get ls 21 bits of double
164	orl	%d0,LOCAL_HI(%a1)	|put them in double result
165dbl_wrt:
166	movel	#0x8,%d0		|byte count for double precision number
167	exg	%a0,%a1		|a0=supervisor source, a1=user dest
168	bsrl	mem_write	|move the number to the user's memory
169	rts
170|
171|	dest_sgl --- write single precision value to user space
172|
173|Input
174|	a0 -> destination address
175|	a1 -> source in extended precision
176|
177|Output
178|	a0 -> destroyed
179|	a1 -> destroyed
180|	d0 -> 0
181|
182|Changes extended precision to single precision.
183|	sgl_sign = ext_sign
184|	sgl_exp = ext_exp - $3fff(ext bias) + $7f(sgl bias)
185|	get rid of ext integer bit
186|	sgl_mant = ext_mant{62:12}
187|
188|		---------------   ---------------    ---------------
189|  extended ->  |s|    exp    |   |1| ms mant   |    | ls mant     |
190|		---------------   ---------------    ---------------
191|		 95	    64    63 62	   40 32      31     12	  0
192|				     |	   |
193|				     |	   |
194|				     |	   |
195|			             v     v
196|			      ---------------
197|  single   ->		      |s|exp| mant  |
198|			      ---------------
199|			      31     22     0
200|
201dest_sgl:
202	clrl	%d0
203	movew	LOCAL_EX(%a1),%d0	|get exponent
204	subw	#0x3fff,%d0	|subtract extended precision bias
205	cmpw	#0x4000,%d0	|check if inf
206	beqs	sinf		|if so, special case
207	addw	#0x7f,%d0		|add single precision bias
208	swap	%d0		|put exp in upper word of d0
209	lsll	#7,%d0		|shift it into single exp bits
210	tstb	LOCAL_SGN(%a1)
211	beqs	get_sman	|if positive, continue
212	bsetl	#31,%d0		|if negative, put in sign first
213	bras	get_sman	|get mantissa
214sinf:
215	movel	#0x7f800000,%d0	|load single inf exp to d0
216	tstb	LOCAL_SGN(%a1)
217	beqs	sgl_wrt		|if positive, continue
218	bsetl	#31,%d0		|if negative, put in sign info
219	bras	sgl_wrt
220
221get_sman:
222	movel	LOCAL_HI(%a1),%d1	|get ms mantissa
223	bfextu	%d1{#1:#23},%d1	|get upper 23 bits of ms
224	orl	%d1,%d0		|put these bits in ms word of single
225
226sgl_wrt:
227	movel	%d0,L_SCR1(%a6)	|put the new exp back on the stack
228	movel	#0x4,%d0		|byte count for single precision number
229	tstl	%a0		|users destination address
230	beqs	sgl_Dn		|destination is a data register
231	exg	%a0,%a1		|a0=supervisor source, a1=user dest
232	leal	L_SCR1(%a6),%a0	|point a0 to data
233	bsrl	mem_write	|move the number to the user's memory
234	rts
235sgl_Dn:
236	bsrl	get_fline	|returns fline word in d0
237	andw	#0x7,%d0		|isolate register number
238	movel	%d0,%d1		|d1 has size:reg formatted for reg_dest
239	orl	#0x10,%d1		|reg_dest wants size added to reg#
240	bral	reg_dest	|size is X, rts in reg_dest will
241|				;return to caller of dest_sgl
242
243dest_ext:
244	tstb	LOCAL_SGN(%a1)	|put back sign into exponent word
245	beqs	dstx_cont
246	bsetb	#sign_bit,LOCAL_EX(%a1)
247dstx_cont:
248	clrb	LOCAL_SGN(%a1)	|clear out the sign byte
249
250	movel	#0x0c,%d0		|byte count for extended number
251	exg	%a0,%a1		|a0=supervisor source, a1=user dest
252	bsrl	mem_write	|move the number to the user's memory
253	rts
254
255	|end