1 /* SPDX-License-Identifier: GPL-2.0 */
2 	.file	"reg_u_add.S"
3 /*---------------------------------------------------------------------------+
4  |  reg_u_add.S                                                              |
5  |                                                                           |
6  | Add two valid (TAG_Valid) FPU_REG numbers, of the same sign, and put the  |
7  |   result in a destination FPU_REG.                                        |
8  |                                                                           |
9  | Copyright (C) 1992,1993,1995,1997                                         |
10  |                  W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
11  |                  E-mail   billm@suburbia.net                              |
12  |                                                                           |
13  | Call from C as:                                                           |
14  |   int  FPU_u_add(FPU_REG *arg1, FPU_REG *arg2, FPU_REG *answ,             |
15  |                                                int control_w)             |
16  |    Return value is the tag of the answer, or-ed with FPU_Exception if     |
17  |    one was raised, or -1 on internal error.                               |
18  |                                                                           |
19  +---------------------------------------------------------------------------*/
20 
21 /*
22  |    Kernel addition routine FPU_u_add(reg *arg1, reg *arg2, reg *answ).
23  |    Takes two valid reg f.p. numbers (TAG_Valid), which are
24  |    treated as unsigned numbers,
25  |    and returns their sum as a TAG_Valid or TAG_Special f.p. number.
26  |    The returned number is normalized.
27  |    Basic checks are performed if PARANOID is defined.
28  */
29 
30 #include "exception.h"
31 #include "fpu_emu.h"
32 #include "control_w.h"
33 
34 .text
35 SYM_FUNC_START(FPU_u_add)
36 	pushl	%ebp
37 	movl	%esp,%ebp
38 	pushl	%esi
39 	pushl	%edi
40 	pushl	%ebx
41 
42 	movl	PARAM1,%esi		/* source 1 */
43 	movl	PARAM2,%edi		/* source 2 */
44 
45 	movl	PARAM6,%ecx
46 	movl	%ecx,%edx
47 	subl	PARAM7,%ecx			/* exp1 - exp2 */
48 	jge	L_arg1_larger
49 
50 	/* num1 is smaller */
51 	movl	SIGL(%esi),%ebx
52 	movl	SIGH(%esi),%eax
53 
54 	movl	%edi,%esi
55 	movl	PARAM7,%edx
56 	negw	%cx
57 	jmp	L_accum_loaded
58 
59 L_arg1_larger:
60 	/* num1 has larger or equal exponent */
61 	movl	SIGL(%edi),%ebx
62 	movl	SIGH(%edi),%eax
63 
64 L_accum_loaded:
65 	movl	PARAM3,%edi		/* destination */
66 	movw	%dx,EXP(%edi)		/* Copy exponent to destination */
67 
68 	xorl	%edx,%edx		/* clear the extension */
69 
70 #ifdef PARANOID
71 	testl	$0x80000000,%eax
72 	je	L_bugged
73 
74 	testl	$0x80000000,SIGH(%esi)
75 	je	L_bugged
76 #endif /* PARANOID */
77 
78 /* The number to be shifted is in %eax:%ebx:%edx */
79 	cmpw	$32,%cx		/* shrd only works for 0..31 bits */
80 	jnc	L_more_than_31
81 
82 /* less than 32 bits */
83 	shrd	%cl,%ebx,%edx
84 	shrd	%cl,%eax,%ebx
85 	shr	%cl,%eax
86 	jmp	L_shift_done
87 
88 L_more_than_31:
89 	cmpw	$64,%cx
90 	jnc	L_more_than_63
91 
92 	subb	$32,%cl
93 	jz	L_exactly_32
94 
95 	shrd	%cl,%eax,%edx
96 	shr	%cl,%eax
97 	orl	%ebx,%ebx
98 	jz	L_more_31_no_low	/* none of the lowest bits is set */
99 
100 	orl	$1,%edx			/* record the fact in the extension */
101 
102 L_more_31_no_low:
103 	movl	%eax,%ebx
104 	xorl	%eax,%eax
105 	jmp	L_shift_done
106 
107 L_exactly_32:
108 	movl	%ebx,%edx
109 	movl	%eax,%ebx
110 	xorl	%eax,%eax
111 	jmp	L_shift_done
112 
113 L_more_than_63:
114 	cmpw	$65,%cx
115 	jnc	L_more_than_64
116 
117 	movl	%eax,%edx
118 	orl	%ebx,%ebx
119 	jz	L_more_63_no_low
120 
121 	orl	$1,%edx
122 	jmp	L_more_63_no_low
123 
124 L_more_than_64:
125 	movl	$1,%edx		/* The shifted nr always at least one '1' */
126 
127 L_more_63_no_low:
128 	xorl	%ebx,%ebx
129 	xorl	%eax,%eax
130 
131 L_shift_done:
132 	/* Now do the addition */
133 	addl	SIGL(%esi),%ebx
134 	adcl	SIGH(%esi),%eax
135 	jnc	L_round_the_result
136 
137 	/* Overflow, adjust the result */
138 	rcrl	$1,%eax
139 	rcrl	$1,%ebx
140 	rcrl	$1,%edx
141 	jnc	L_no_bit_lost
142 
143 	orl	$1,%edx
144 
145 L_no_bit_lost:
146 	incw	EXP(%edi)
147 
148 L_round_the_result:
149 	jmp	fpu_reg_round	/* Round the result */
150 
151 
152 
153 #ifdef PARANOID
154 /* If we ever get here then we have problems! */
155 L_bugged:
156 	pushl	EX_INTERNAL|0x201
157 	call	EXCEPTION
158 	pop	%ebx
159 	movl	$-1,%eax
160 	jmp	L_exit
161 
162 L_exit:
163 	popl	%ebx
164 	popl	%edi
165 	popl	%esi
166 	leave
167 	ret
168 #endif /* PARANOID */
169 SYM_FUNC_END(FPU_u_add)
170