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 */
30int 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