aboutsummaryrefslogtreecommitdiffstats
path: root/arch/m68k/fpsp040/sgetem.S
blob: 0fcbd045ba757171b18309861b0eca269aa50506 (plain) (blame)
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
|
|	sgetem.sa 3.1 12/10/90
|
|	The entry point sGETEXP returns the exponent portion
|	of the input argument.  The exponent bias is removed
|	and the exponent value is returned as an extended
|	precision number in fp0.  sGETEXPD handles denormalized
|	numbers.
|
|	The entry point sGETMAN extracts the mantissa of the
|	input argument.  The mantissa is converted to an
|	extended precision number and returned in fp0.  The
|	range of the result is [1.0 - 2.0).
|
|
|	Input:  Double-extended number X in the ETEMP space in
|		the floating-point save stack.
|
|	Output:	The functions return exp(X) or man(X) in fp0.
|
|	Modified: fp0.
|
|
|		Copyright (C) Motorola, Inc. 1990
|			All Rights Reserved
|
|	THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA
|	The copyright notice above does not evidence any
|	actual or intended publication of such source code.

|SGETEM	idnt	2,1 | Motorola 040 Floating Point Software Package

	|section 8

#include "fpsp.h"

	|xref	nrm_set

|
| This entry point is used by the unimplemented instruction exception
| handler.  It points a0 to the input operand.
|
|
|
|	SGETEXP
|

	.global	sgetexp
sgetexp:
	movew	LOCAL_EX(%a0),%d0	|get the exponent
	bclrl	#15,%d0		|clear the sign bit
	subw	#0x3fff,%d0	|subtract off the bias
	fmovew  %d0,%fp0		|move the exp to fp0
	rts

	.global	sgetexpd
sgetexpd:
	bclrb	#sign_bit,LOCAL_EX(%a0)
	bsr	nrm_set		|normalize (exp will go negative)
	movew	LOCAL_EX(%a0),%d0	|load resulting exponent into d0
	subw	#0x3fff,%d0	|subtract off the bias
	fmovew	%d0,%fp0		|move the exp to fp0
	rts
|
|
| This entry point is used by the unimplemented instruction exception
| handler.  It points a0 to the input operand.
|
|
|
|	SGETMAN
|
|
| For normalized numbers, leave the mantissa alone, simply load
| with an exponent of +/- $3fff.
|
	.global	sgetman
sgetman:
	movel	USER_FPCR(%a6),%d0
	andil	#0xffffff00,%d0	|clear rounding precision and mode
	fmovel	%d0,%fpcr		|this fpcr setting is used by the 882
	movew	LOCAL_EX(%a0),%d0	|get the exp (really just want sign bit)
	orw	#0x7fff,%d0	|clear old exp
	bclrl	#14,%d0		|make it the new exp +-3fff
	movew	%d0,LOCAL_EX(%a0)	|move the sign & exp back to fsave stack
	fmovex	(%a0),%fp0	|put new value back in fp0
	rts

|
| For denormalized numbers, shift the mantissa until the j-bit = 1,
| then load the exponent with +/1 $3fff.
|
	.global	sgetmand
sgetmand:
	movel	LOCAL_HI(%a0),%d0	|load ms mant in d0
	movel	LOCAL_LO(%a0),%d1	|load ls mant in d1
	bsr	shft		|shift mantissa bits till msbit is set
	movel	%d0,LOCAL_HI(%a0)	|put ms mant back on stack
	movel	%d1,LOCAL_LO(%a0)	|put ls mant back on stack
	bras	sgetman

|
|	SHFT
|
|	Shifts the mantissa bits until msbit is set.
|	input:
|		ms mantissa part in d0
|		ls mantissa part in d1
|	output:
|		shifted bits in d0 and d1
shft:
	tstl	%d0		|if any bits set in ms mant
	bnes	upper		|then branch
|				;else no bits set in ms mant
	tstl	%d1		|test if any bits set in ls mant
	bnes	cont		|if set then continue
	bras	shft_end	|else return
cont:
	movel	%d3,-(%a7)	|save d3
	exg	%d0,%d1		|shift ls mant to ms mant
	bfffo	%d0{#0:#32},%d3	|find first 1 in ls mant to d0
	lsll	%d3,%d0		|shift first 1 to integer bit in ms mant
	movel	(%a7)+,%d3	|restore d3
	bras	shft_end
upper:

	moveml	%d3/%d5/%d6,-(%a7)	|save registers
	bfffo	%d0{#0:#32},%d3	|find first 1 in ls mant to d0
	lsll	%d3,%d0		|shift ms mant until j-bit is set
	movel	%d1,%d6		|save ls mant in d6
	lsll	%d3,%d1		|shift ls mant by count
	movel	#32,%d5
	subl	%d3,%d5		|sub 32 from shift for ls mant
	lsrl	%d5,%d6		|shift off all bits but those that will
|				;be shifted into ms mant
	orl	%d6,%d0		|shift the ls mant bits into the ms mant
	moveml	(%a7)+,%d3/%d5/%d6	|restore registers
shft_end:
	rts

	|end