summaryrefslogtreecommitdiff
path: root/arch/x86/math-emu/reg_norm.S
blob: 8b6352efceef2629138490602f4e7fcb7519b533 (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
/*---------------------------------------------------------------------------+
 |  reg_norm.S                                                               |
 |                                                                           |
 | Copyright (C) 1992,1993,1994,1995,1997                                    |
 |                       W. Metzenthen, 22 Parker St, Ormond, Vic 3163,      |
 |                       Australia.  E-mail billm@suburbia.net               |
 |                                                                           |
 | Normalize the value in a FPU_REG.                                         |
 |                                                                           |
 | Call from C as:                                                           |
 |    int FPU_normalize(FPU_REG *n)                                          |
 |                                                                           |
 |    int FPU_normalize_nuo(FPU_REG *n)                                      |
 |                                                                           |
 |    Return value is the tag of the answer, or-ed with FPU_Exception if     |
 |    one was raised, or -1 on internal error.                               |
 |                                                                           |
 +---------------------------------------------------------------------------*/

#include "fpu_emu.h"


.text
ENTRY(FPU_normalize)
	pushl	%ebp
	movl	%esp,%ebp
	pushl	%ebx

	movl	PARAM1,%ebx

	movl	SIGH(%ebx),%edx
	movl	SIGL(%ebx),%eax

	orl	%edx,%edx	/* ms bits */
	js	L_done		/* Already normalized */
	jnz	L_shift_1	/* Shift left 1 - 31 bits */

	orl	%eax,%eax
	jz	L_zero		/* The contents are zero */

	movl	%eax,%edx
	xorl	%eax,%eax
	subw	$32,EXP(%ebx)	/* This can cause an underflow */

/* We need to shift left by 1 - 31 bits */
L_shift_1:
	bsrl	%edx,%ecx	/* get the required shift in %ecx */
	subl	$31,%ecx
	negl	%ecx
	shld	%cl,%eax,%edx
	shl	%cl,%eax
	subw	%cx,EXP(%ebx)	/* This can cause an underflow */

	movl	%edx,SIGH(%ebx)
	movl	%eax,SIGL(%ebx)

L_done:
	cmpw	EXP_OVER,EXP(%ebx)
	jge	L_overflow

	cmpw	EXP_UNDER,EXP(%ebx)
	jle	L_underflow

L_exit_valid:
	movl	TAG_Valid,%eax

	/* Convert the exponent to 80x87 form. */
	addw	EXTENDED_Ebias,EXP(%ebx)
	andw	$0x7fff,EXP(%ebx)

L_exit:
	popl	%ebx
	leave
	ret


L_zero:
	movw	$0,EXP(%ebx)
	movl	TAG_Zero,%eax
	jmp	L_exit

L_underflow:
	/* Convert the exponent to 80x87 form. */
	addw	EXTENDED_Ebias,EXP(%ebx)
	push	%ebx
	call	arith_underflow
	pop	%ebx
	jmp	L_exit

L_overflow:
	/* Convert the exponent to 80x87 form. */
	addw	EXTENDED_Ebias,EXP(%ebx)
	push	%ebx
	call	arith_overflow
	pop	%ebx
	jmp	L_exit



/* Normalise without reporting underflow or overflow */
ENTRY(FPU_normalize_nuo)
	pushl	%ebp
	movl	%esp,%ebp
	pushl	%ebx

	movl	PARAM1,%ebx

	movl	SIGH(%ebx),%edx
	movl	SIGL(%ebx),%eax

	orl	%edx,%edx	/* ms bits */
	js	L_exit_nuo_valid	/* Already normalized */
	jnz	L_nuo_shift_1	/* Shift left 1 - 31 bits */

	orl	%eax,%eax
	jz	L_exit_nuo_zero		/* The contents are zero */

	movl	%eax,%edx
	xorl	%eax,%eax
	subw	$32,EXP(%ebx)	/* This can cause an underflow */

/* We need to shift left by 1 - 31 bits */
L_nuo_shift_1:
	bsrl	%edx,%ecx	/* get the required shift in %ecx */
	subl	$31,%ecx
	negl	%ecx
	shld	%cl,%eax,%edx
	shl	%cl,%eax
	subw	%cx,EXP(%ebx)	/* This can cause an underflow */

	movl	%edx,SIGH(%ebx)
	movl	%eax,SIGL(%ebx)

L_exit_nuo_valid:
	movl	TAG_Valid,%eax

	popl	%ebx
	leave
	ret

L_exit_nuo_zero:
	movl	TAG_Zero,%eax
	movw	EXP_UNDER,EXP(%ebx)

	popl	%ebx
	leave
	ret