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1da177e4 LT |
1 | /*---------------------------------------------------------------------------+ |
2 | | reg_mul.c | | |
3 | | | | |
4 | | Multiply one FPU_REG by another, put the result in a destination FPU_REG. | | |
5 | | | | |
6 | | Copyright (C) 1992,1993,1997 | | |
7 | | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia | | |
8 | | E-mail billm@suburbia.net | | |
9 | | | | |
10 | | Returns the tag of the result if no exceptions or errors occurred. | | |
11 | | | | |
12 | +---------------------------------------------------------------------------*/ | |
13 | ||
14 | /*---------------------------------------------------------------------------+ | |
15 | | The destination may be any FPU_REG, including one of the source FPU_REGs. | | |
16 | +---------------------------------------------------------------------------*/ | |
17 | ||
18 | #include "fpu_emu.h" | |
19 | #include "exception.h" | |
20 | #include "reg_constant.h" | |
21 | #include "fpu_system.h" | |
22 | ||
23 | ||
24 | /* | |
25 | Multiply two registers to give a register result. | |
26 | The sources are st(deststnr) and (b,tagb,signb). | |
27 | The destination is st(deststnr). | |
28 | */ | |
29 | /* This routine must be called with non-empty source registers */ | |
30 | int FPU_mul(FPU_REG const *b, u_char tagb, int deststnr, int control_w) | |
31 | { | |
32 | FPU_REG *a = &st(deststnr); | |
33 | FPU_REG *dest = a; | |
34 | u_char taga = FPU_gettagi(deststnr); | |
35 | u_char saved_sign = getsign(dest); | |
36 | u_char sign = (getsign(a) ^ getsign(b)); | |
37 | int tag; | |
38 | ||
39 | ||
40 | if ( !(taga | tagb) ) | |
41 | { | |
42 | /* Both regs Valid, this should be the most common case. */ | |
43 | ||
44 | tag = FPU_u_mul(a, b, dest, control_w, sign, exponent(a) + exponent(b)); | |
45 | if ( tag < 0 ) | |
46 | { | |
47 | setsign(dest, saved_sign); | |
48 | return tag; | |
49 | } | |
50 | FPU_settagi(deststnr, tag); | |
51 | return tag; | |
52 | } | |
53 | ||
54 | if ( taga == TAG_Special ) | |
55 | taga = FPU_Special(a); | |
56 | if ( tagb == TAG_Special ) | |
57 | tagb = FPU_Special(b); | |
58 | ||
59 | if ( ((taga == TAG_Valid) && (tagb == TW_Denormal)) | |
60 | || ((taga == TW_Denormal) && (tagb == TAG_Valid)) | |
61 | || ((taga == TW_Denormal) && (tagb == TW_Denormal)) ) | |
62 | { | |
63 | FPU_REG x, y; | |
64 | if ( denormal_operand() < 0 ) | |
65 | return FPU_Exception; | |
66 | ||
67 | FPU_to_exp16(a, &x); | |
68 | FPU_to_exp16(b, &y); | |
69 | tag = FPU_u_mul(&x, &y, dest, control_w, sign, | |
70 | exponent16(&x) + exponent16(&y)); | |
71 | if ( tag < 0 ) | |
72 | { | |
73 | setsign(dest, saved_sign); | |
74 | return tag; | |
75 | } | |
76 | FPU_settagi(deststnr, tag); | |
77 | return tag; | |
78 | } | |
79 | else if ( (taga <= TW_Denormal) && (tagb <= TW_Denormal) ) | |
80 | { | |
81 | if ( ((tagb == TW_Denormal) || (taga == TW_Denormal)) | |
82 | && (denormal_operand() < 0) ) | |
83 | return FPU_Exception; | |
84 | ||
85 | /* Must have either both arguments == zero, or | |
86 | one valid and the other zero. | |
87 | The result is therefore zero. */ | |
88 | FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr); | |
89 | /* The 80486 book says that the answer is +0, but a real | |
90 | 80486 behaves this way. | |
91 | IEEE-754 apparently says it should be this way. */ | |
92 | setsign(dest, sign); | |
93 | return TAG_Zero; | |
94 | } | |
95 | /* Must have infinities, NaNs, etc */ | |
96 | else if ( (taga == TW_NaN) || (tagb == TW_NaN) ) | |
97 | { | |
98 | return real_2op_NaN(b, tagb, deststnr, &st(0)); | |
99 | } | |
100 | else if ( ((taga == TW_Infinity) && (tagb == TAG_Zero)) | |
101 | || ((tagb == TW_Infinity) && (taga == TAG_Zero)) ) | |
102 | { | |
103 | return arith_invalid(deststnr); /* Zero*Infinity is invalid */ | |
104 | } | |
105 | else if ( ((taga == TW_Denormal) || (tagb == TW_Denormal)) | |
106 | && (denormal_operand() < 0) ) | |
107 | { | |
108 | return FPU_Exception; | |
109 | } | |
110 | else if (taga == TW_Infinity) | |
111 | { | |
112 | FPU_copy_to_regi(a, TAG_Special, deststnr); | |
113 | setsign(dest, sign); | |
114 | return TAG_Special; | |
115 | } | |
116 | else if (tagb == TW_Infinity) | |
117 | { | |
118 | FPU_copy_to_regi(b, TAG_Special, deststnr); | |
119 | setsign(dest, sign); | |
120 | return TAG_Special; | |
121 | } | |
122 | ||
123 | #ifdef PARANOID | |
124 | else | |
125 | { | |
126 | EXCEPTION(EX_INTERNAL|0x102); | |
127 | return FPU_Exception; | |
128 | } | |
129 | #endif /* PARANOID */ | |
130 | ||
131 | return 0; | |
132 | } |