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 */
29int 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