summaryrefslogtreecommitdiff
path: root/arch/x86/math-emu/reg_u_add.S
blob: 3b1bc5e9b2f6383a6a4f518cf6e70f568b125df9 (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
	.file	"reg_u_add.S"
/*---------------------------------------------------------------------------+
 |  reg_u_add.S                                                              |
 |                                                                           |
 | Add two valid (TAG_Valid) FPU_REG numbers, of the same sign, and put the  |
 |   result in a destination FPU_REG.                                        |
 |                                                                           |
 | Copyright (C) 1992,1993,1995,1997                                         |
 |                  W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
 |                  E-mail   billm@suburbia.net                              |
 |                                                                           |
 | Call from C as:                                                           |
 |   int  FPU_u_add(FPU_REG *arg1, FPU_REG *arg2, FPU_REG *answ,             |
 |                                                int control_w)             |
 |    Return value is the tag of the answer, or-ed with FPU_Exception if     |
 |    one was raised, or -1 on internal error.                               |
 |                                                                           |
 +---------------------------------------------------------------------------*/

/*
 |    Kernel addition routine FPU_u_add(reg *arg1, reg *arg2, reg *answ).
 |    Takes two valid reg f.p. numbers (TAG_Valid), which are
 |    treated as unsigned numbers,
 |    and returns their sum as a TAG_Valid or TAG_Special f.p. number.
 |    The returned number is normalized.
 |    Basic checks are performed if PARANOID is defined.
 */

#include "exception.h"
#include "fpu_emu.h"
#include "control_w.h"

.text
ENTRY(FPU_u_add)
	pushl	%ebp
	movl	%esp,%ebp
	pushl	%esi
	pushl	%edi
	pushl	%ebx

	movl	PARAM1,%esi		/* source 1 */
	movl	PARAM2,%edi		/* source 2 */

	movl	PARAM6,%ecx
	movl	%ecx,%edx
	subl	PARAM7,%ecx			/* exp1 - exp2 */
	jge	L_arg1_larger

	/* num1 is smaller */
	movl	SIGL(%esi),%ebx
	movl	SIGH(%esi),%eax

	movl	%edi,%esi
	movl	PARAM7,%edx
	negw	%cx
	jmp	L_accum_loaded

L_arg1_larger:
	/* num1 has larger or equal exponent */
	movl	SIGL(%edi),%ebx
	movl	SIGH(%edi),%eax

L_accum_loaded:
	movl	PARAM3,%edi		/* destination */
	movw	%dx,EXP(%edi)		/* Copy exponent to destination */

	xorl	%edx,%edx		/* clear the extension */

#ifdef PARANOID
	testl	$0x80000000,%eax
	je	L_bugged

	testl	$0x80000000,SIGH(%esi)
	je	L_bugged
#endif /* PARANOID */

/* The number to be shifted is in %eax:%ebx:%edx */
	cmpw	$32,%cx		/* shrd only works for 0..31 bits */
	jnc	L_more_than_31

/* less than 32 bits */
	shrd	%cl,%ebx,%edx
	shrd	%cl,%eax,%ebx
	shr	%cl,%eax
	jmp	L_shift_done

L_more_than_31:
	cmpw	$64,%cx
	jnc	L_more_than_63

	subb	$32,%cl
	jz	L_exactly_32

	shrd	%cl,%eax,%edx
	shr	%cl,%eax
	orl	%ebx,%ebx
	jz	L_more_31_no_low	/* none of the lowest bits is set */

	orl	$1,%edx			/* record the fact in the extension */

L_more_31_no_low:
	movl	%eax,%ebx
	xorl	%eax,%eax
	jmp	L_shift_done

L_exactly_32:
	movl	%ebx,%edx
	movl	%eax,%ebx
	xorl	%eax,%eax
	jmp	L_shift_done

L_more_than_63:
	cmpw	$65,%cx
	jnc	L_more_than_64

	movl	%eax,%edx
	orl	%ebx,%ebx
	jz	L_more_63_no_low

	orl	$1,%edx
	jmp	L_more_63_no_low

L_more_than_64:
	movl	$1,%edx		/* The shifted nr always at least one '1' */

L_more_63_no_low:
	xorl	%ebx,%ebx
	xorl	%eax,%eax

L_shift_done:
	/* Now do the addition */
	addl	SIGL(%esi),%ebx
	adcl	SIGH(%esi),%eax
	jnc	L_round_the_result

	/* Overflow, adjust the result */
	rcrl	$1,%eax
	rcrl	$1,%ebx
	rcrl	$1,%edx
	jnc	L_no_bit_lost

	orl	$1,%edx

L_no_bit_lost:
	incw	EXP(%edi)

L_round_the_result:
	jmp	fpu_reg_round	/* Round the result */



#ifdef PARANOID
/* If we ever get here then we have problems! */
L_bugged:
	pushl	EX_INTERNAL|0x201
	call	EXCEPTION
	pop	%ebx
	movl	$-1,%eax
	jmp	L_exit

L_exit:
	popl	%ebx
	popl	%edi
	popl	%esi
	leave
	ret
#endif /* PARANOID */
ENDPROC(FPU_u_add)