blob: 973f12af97df55a837eae72484aeffbabc08d704 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001 .file "reg_u_mul.S"
2/*---------------------------------------------------------------------------+
3 | reg_u_mul.S |
4 | |
5 | Core multiplication routine |
6 | |
7 | Copyright (C) 1992,1993,1995,1997 |
8 | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
9 | E-mail billm@suburbia.net |
10 | |
11 | |
12 +---------------------------------------------------------------------------*/
13
14/*---------------------------------------------------------------------------+
15 | Basic multiplication routine. |
16 | Does not check the resulting exponent for overflow/underflow |
17 | |
18 | FPU_u_mul(FPU_REG *a, FPU_REG *b, FPU_REG *c, unsigned int cw); |
19 | |
20 | Internal working is at approx 128 bits. |
21 | Result is rounded to nearest 53 or 64 bits, using "nearest or even". |
22 +---------------------------------------------------------------------------*/
23
24#include "exception.h"
25#include "fpu_emu.h"
26#include "control_w.h"
27
28
29
30#ifndef NON_REENTRANT_FPU
31/* Local storage on the stack: */
32#define FPU_accum_0 -4(%ebp) /* ms word */
33#define FPU_accum_1 -8(%ebp)
34
35#else
36/* Local storage in a static area: */
37.data
38 .align 4,0
39FPU_accum_0:
40 .long 0
41FPU_accum_1:
42 .long 0
43#endif /* NON_REENTRANT_FPU */
44
45
46.text
47ENTRY(FPU_u_mul)
48 pushl %ebp
49 movl %esp,%ebp
50#ifndef NON_REENTRANT_FPU
51 subl $8,%esp
52#endif /* NON_REENTRANT_FPU */
53
54 pushl %esi
55 pushl %edi
56 pushl %ebx
57
58 movl PARAM1,%esi
59 movl PARAM2,%edi
60
61#ifdef PARANOID
62 testl $0x80000000,SIGH(%esi)
63 jz L_bugged
64 testl $0x80000000,SIGH(%edi)
65 jz L_bugged
66#endif /* PARANOID */
67
68 xorl %ecx,%ecx
69 xorl %ebx,%ebx
70
71 movl SIGL(%esi),%eax
72 mull SIGL(%edi)
73 movl %eax,FPU_accum_0
74 movl %edx,FPU_accum_1
75
76 movl SIGL(%esi),%eax
77 mull SIGH(%edi)
78 addl %eax,FPU_accum_1
79 adcl %edx,%ebx
80/* adcl $0,%ecx // overflow here is not possible */
81
82 movl SIGH(%esi),%eax
83 mull SIGL(%edi)
84 addl %eax,FPU_accum_1
85 adcl %edx,%ebx
86 adcl $0,%ecx
87
88 movl SIGH(%esi),%eax
89 mull SIGH(%edi)
90 addl %eax,%ebx
91 adcl %edx,%ecx
92
93 /* Get the sum of the exponents. */
94 movl PARAM6,%eax
95 subl EXP_BIAS-1,%eax
96
97 /* Two denormals can cause an exponent underflow */
98 cmpl EXP_WAY_UNDER,%eax
99 jg Exp_not_underflow
100
101 /* Set to a really low value allow correct handling */
102 movl EXP_WAY_UNDER,%eax
103
104Exp_not_underflow:
105
106/* Have now finished with the sources */
107 movl PARAM3,%edi /* Point to the destination */
108 movw %ax,EXP(%edi)
109
110/* Now make sure that the result is normalized */
111 testl $0x80000000,%ecx
112 jnz LResult_Normalised
113
114 /* Normalize by shifting left one bit */
115 shll $1,FPU_accum_0
116 rcll $1,FPU_accum_1
117 rcll $1,%ebx
118 rcll $1,%ecx
119 decw EXP(%edi)
120
121LResult_Normalised:
122 movl FPU_accum_0,%eax
123 movl FPU_accum_1,%edx
124 orl %eax,%eax
125 jz L_extent_zero
126
127 orl $1,%edx
128
129L_extent_zero:
130 movl %ecx,%eax
131 jmp fpu_reg_round
132
133
134#ifdef PARANOID
135L_bugged:
136 pushl EX_INTERNAL|0x205
137 call EXCEPTION
138 pop %ebx
139 jmp L_exit
140
141L_exit:
142 popl %ebx
143 popl %edi
144 popl %esi
145 leave
146 ret
147#endif /* PARANOID */
148