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 Multiply two registers to give a register result.
25 The sources are st(deststnr) and (b,tagb,signb).
26 The destination is st(deststnr).
27 */
28 /* This routine must be called with non-empty source registers */
FPU_mul(FPU_REG const * b,u_char tagb,int deststnr,int control_w)29 int FPU_mul(FPU_REG const *b, u_char tagb, int deststnr, int control_w)
30 {
31 FPU_REG *a = &st(deststnr);
32 FPU_REG *dest = a;
33 u_char taga = FPU_gettagi(deststnr);
34 u_char saved_sign = getsign(dest);
35 u_char sign = (getsign(a) ^ getsign(b));
36 int tag;
37
38 if (!(taga | tagb)) {
39 /* Both regs Valid, this should be the most common case. */
40
41 tag =
42 FPU_u_mul(a, b, dest, control_w, sign,
43 exponent(a) + exponent(b));
44 if (tag < 0) {
45 setsign(dest, saved_sign);
46 return tag;
47 }
48 FPU_settagi(deststnr, tag);
49 return tag;
50 }
51
52 if (taga == TAG_Special)
53 taga = FPU_Special(a);
54 if (tagb == TAG_Special)
55 tagb = FPU_Special(b);
56
57 if (((taga == TAG_Valid) && (tagb == TW_Denormal))
58 || ((taga == TW_Denormal) && (tagb == TAG_Valid))
59 || ((taga == TW_Denormal) && (tagb == TW_Denormal))) {
60 FPU_REG x, y;
61 if (denormal_operand() < 0)
62 return FPU_Exception;
63
64 FPU_to_exp16(a, &x);
65 FPU_to_exp16(b, &y);
66 tag = FPU_u_mul(&x, &y, dest, control_w, sign,
67 exponent16(&x) + exponent16(&y));
68 if (tag < 0) {
69 setsign(dest, saved_sign);
70 return tag;
71 }
72 FPU_settagi(deststnr, tag);
73 return tag;
74 } else if ((taga <= TW_Denormal) && (tagb <= TW_Denormal)) {
75 if (((tagb == TW_Denormal) || (taga == TW_Denormal))
76 && (denormal_operand() < 0))
77 return FPU_Exception;
78
79 /* Must have either both arguments == zero, or
80 one valid and the other zero.
81 The result is therefore zero. */
82 FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
83 /* The 80486 book says that the answer is +0, but a real
84 80486 behaves this way.
85 IEEE-754 apparently says it should be this way. */
86 setsign(dest, sign);
87 return TAG_Zero;
88 }
89 /* Must have infinities, NaNs, etc */
90 else if ((taga == TW_NaN) || (tagb == TW_NaN)) {
91 return real_2op_NaN(b, tagb, deststnr, &st(0));
92 } else if (((taga == TW_Infinity) && (tagb == TAG_Zero))
93 || ((tagb == TW_Infinity) && (taga == TAG_Zero))) {
94 return arith_invalid(deststnr); /* Zero*Infinity is invalid */
95 } else if (((taga == TW_Denormal) || (tagb == TW_Denormal))
96 && (denormal_operand() < 0)) {
97 return FPU_Exception;
98 } else if (taga == TW_Infinity) {
99 FPU_copy_to_regi(a, TAG_Special, deststnr);
100 setsign(dest, sign);
101 return TAG_Special;
102 } else if (tagb == TW_Infinity) {
103 FPU_copy_to_regi(b, TAG_Special, deststnr);
104 setsign(dest, sign);
105 return TAG_Special;
106 }
107 #ifdef PARANOID
108 else {
109 EXCEPTION(EX_INTERNAL | 0x102);
110 return FPU_Exception;
111 }
112 #endif /* PARANOID */
113
114 return 0;
115 }
116