1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /*---------------------------------------------------------------------------+ |
3 | | reg_mul.c | |
4 | | | |
5 | | Multiply one FPU_REG by another, put the result in a destination FPU_REG. | |
6 | | | |
7 | | Copyright (C) 1992,1993,1997 | |
8 | | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia | |
9 | | E-mail billm@suburbia.net | |
10 | | | |
11 | | Returns the tag of the result if no exceptions or errors occurred. | |
12 | | | |
13 | +---------------------------------------------------------------------------*/ |
14 | |
15 | /*---------------------------------------------------------------------------+ |
16 | | The destination may be any FPU_REG, including one of the source FPU_REGs. | |
17 | +---------------------------------------------------------------------------*/ |
18 | |
19 | #include "fpu_emu.h" |
20 | #include "exception.h" |
21 | #include "reg_constant.h" |
22 | #include "fpu_system.h" |
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(stnr: deststnr); |
35 | u_char saved_sign = getsign(dest); |
36 | u_char sign = (getsign(a) ^ getsign(b)); |
37 | int tag; |
38 | |
39 | if (!(taga | tagb)) { |
40 | /* Both regs Valid, this should be the most common case. */ |
41 | |
42 | tag = |
43 | FPU_u_mul(arg1: a, arg2: b, answ: dest, control_w, sign, |
44 | exponent(a) + exponent(b)); |
45 | if (tag < 0) { |
46 | setsign(dest, saved_sign); |
47 | return tag; |
48 | } |
49 | FPU_settagi(stnr: deststnr, tag); |
50 | return tag; |
51 | } |
52 | |
53 | if (taga == TAG_Special) |
54 | taga = FPU_Special(ptr: a); |
55 | if (tagb == TAG_Special) |
56 | tagb = FPU_Special(ptr: b); |
57 | |
58 | if (((taga == TAG_Valid) && (tagb == TW_Denormal)) |
59 | || ((taga == TW_Denormal) && (tagb == TAG_Valid)) |
60 | || ((taga == TW_Denormal) && (tagb == TW_Denormal))) { |
61 | FPU_REG x, y; |
62 | if (denormal_operand() < 0) |
63 | return FPU_Exception; |
64 | |
65 | FPU_to_exp16(a, x: &x); |
66 | FPU_to_exp16(a: b, x: &y); |
67 | tag = FPU_u_mul(arg1: &x, arg2: &y, answ: dest, control_w, sign, |
68 | exponent16(&x) + exponent16(&y)); |
69 | if (tag < 0) { |
70 | setsign(dest, saved_sign); |
71 | return tag; |
72 | } |
73 | FPU_settagi(stnr: deststnr, tag); |
74 | return tag; |
75 | } else if ((taga <= TW_Denormal) && (tagb <= TW_Denormal)) { |
76 | if (((tagb == TW_Denormal) || (taga == TW_Denormal)) |
77 | && (denormal_operand() < 0)) |
78 | return FPU_Exception; |
79 | |
80 | /* Must have either both arguments == zero, or |
81 | one valid and the other zero. |
82 | The result is therefore zero. */ |
83 | FPU_copy_to_regi(r: &CONST_Z, TAG_Zero, stnr: deststnr); |
84 | /* The 80486 book says that the answer is +0, but a real |
85 | 80486 behaves this way. |
86 | IEEE-754 apparently says it should be this way. */ |
87 | setsign(dest, sign); |
88 | return TAG_Zero; |
89 | } |
90 | /* Must have infinities, NaNs, etc */ |
91 | else if ((taga == TW_NaN) || (tagb == TW_NaN)) { |
92 | return real_2op_NaN(b, tagb, deststnr, defaultNaN: &st(0)); |
93 | } else if (((taga == TW_Infinity) && (tagb == TAG_Zero)) |
94 | || ((tagb == TW_Infinity) && (taga == TAG_Zero))) { |
95 | return arith_invalid(deststnr); /* Zero*Infinity is invalid */ |
96 | } else if (((taga == TW_Denormal) || (tagb == TW_Denormal)) |
97 | && (denormal_operand() < 0)) { |
98 | return FPU_Exception; |
99 | } else if (taga == TW_Infinity) { |
100 | FPU_copy_to_regi(r: a, TAG_Special, stnr: deststnr); |
101 | setsign(dest, sign); |
102 | return TAG_Special; |
103 | } else if (tagb == TW_Infinity) { |
104 | FPU_copy_to_regi(r: b, TAG_Special, stnr: deststnr); |
105 | setsign(dest, sign); |
106 | return TAG_Special; |
107 | } |
108 | #ifdef PARANOID |
109 | else { |
110 | EXCEPTION(EX_INTERNAL | 0x102); |
111 | return FPU_Exception; |
112 | } |
113 | #endif /* PARANOID */ |
114 | |
115 | return 0; |
116 | } |
117 | |