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/arch/x86/math-emu/reg_mul.c

https://bitbucket.org/thekraven/iscream_thunderc-2.6.35
C | 115 lines | 76 code | 10 blank | 29 comment | 55 complexity | 1b691c0e8092f5dc825003cd65dbc80e MD5 | raw file
Possible License(s): GPL-2.0, LGPL-2.0, AGPL-1.0
  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}