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 */
FPU_mul(FPU_REG const * b,u_char tagb,int deststnr,int control_w)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 	if (!(taga | tagb)) {
40 		/* Both regs Valid, this should be the most common case. */
41 
42 		tag =
43 		    FPU_u_mul(a, b, 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(deststnr, tag);
50 		return tag;
51 	}
52 
53 	if (taga == TAG_Special)
54 		taga = FPU_Special(a);
55 	if (tagb == TAG_Special)
56 		tagb = FPU_Special(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);
66 		FPU_to_exp16(b, &y);
67 		tag = FPU_u_mul(&x, &y, 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(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(&CONST_Z, TAG_Zero, 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, &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(a, TAG_Special, deststnr);
101 		setsign(dest, sign);
102 		return TAG_Special;
103 	} else if (tagb == TW_Infinity) {
104 		FPU_copy_to_regi(b, TAG_Special, 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