116 lines
3.9 KiB
C
116 lines
3.9 KiB
C
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/*---------------------------------------------------------------------------+
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| reg_mul.c |
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| Multiply one FPU_REG by another, put the result in a destination FPU_REG. |
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| Copyright (C) 1992,1993,1997 |
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| W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
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| E-mail billm@suburbia.net |
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| Returns the tag of the result if no exceptions or errors occurred. |
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+---------------------------------------------------------------------------*/
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/*---------------------------------------------------------------------------+
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| The destination may be any FPU_REG, including one of the source FPU_REGs. |
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+---------------------------------------------------------------------------*/
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#include "fpu_emu.h"
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#include "exception.h"
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#include "reg_constant.h"
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#include "fpu_system.h"
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/*
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Multiply two registers to give a register result.
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The sources are st(deststnr) and (b,tagb,signb).
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The destination is st(deststnr).
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*/
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/* This routine must be called with non-empty source registers */
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int FPU_mul(FPU_REG const *b, u_char tagb, int deststnr, int control_w)
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{
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FPU_REG *a = &st(deststnr);
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FPU_REG *dest = a;
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u_char taga = FPU_gettagi(deststnr);
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u_char saved_sign = getsign(dest);
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u_char sign = (getsign(a) ^ getsign(b));
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int tag;
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if (!(taga | tagb)) {
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/* Both regs Valid, this should be the most common case. */
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tag =
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FPU_u_mul(a, b, dest, control_w, sign,
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exponent(a) + exponent(b));
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if (tag < 0) {
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setsign(dest, saved_sign);
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return tag;
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}
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FPU_settagi(deststnr, tag);
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return tag;
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}
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if (taga == TAG_Special)
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taga = FPU_Special(a);
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if (tagb == TAG_Special)
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tagb = FPU_Special(b);
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if (((taga == TAG_Valid) && (tagb == TW_Denormal))
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|| ((taga == TW_Denormal) && (tagb == TAG_Valid))
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|| ((taga == TW_Denormal) && (tagb == TW_Denormal))) {
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FPU_REG x, y;
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if (denormal_operand() < 0)
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return FPU_Exception;
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FPU_to_exp16(a, &x);
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FPU_to_exp16(b, &y);
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tag = FPU_u_mul(&x, &y, dest, control_w, sign,
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exponent16(&x) + exponent16(&y));
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if (tag < 0) {
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setsign(dest, saved_sign);
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return tag;
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}
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FPU_settagi(deststnr, tag);
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return tag;
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} else if ((taga <= TW_Denormal) && (tagb <= TW_Denormal)) {
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if (((tagb == TW_Denormal) || (taga == TW_Denormal))
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&& (denormal_operand() < 0))
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return FPU_Exception;
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/* Must have either both arguments == zero, or
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one valid and the other zero.
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The result is therefore zero. */
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FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
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/* The 80486 book says that the answer is +0, but a real
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80486 behaves this way.
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IEEE-754 apparently says it should be this way. */
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setsign(dest, sign);
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return TAG_Zero;
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}
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/* Must have infinities, NaNs, etc */
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else if ((taga == TW_NaN) || (tagb == TW_NaN)) {
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return real_2op_NaN(b, tagb, deststnr, &st(0));
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} else if (((taga == TW_Infinity) && (tagb == TAG_Zero))
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|| ((tagb == TW_Infinity) && (taga == TAG_Zero))) {
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return arith_invalid(deststnr); /* Zero*Infinity is invalid */
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} else if (((taga == TW_Denormal) || (tagb == TW_Denormal))
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&& (denormal_operand() < 0)) {
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return FPU_Exception;
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} else if (taga == TW_Infinity) {
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FPU_copy_to_regi(a, TAG_Special, deststnr);
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setsign(dest, sign);
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return TAG_Special;
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} else if (tagb == TW_Infinity) {
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FPU_copy_to_regi(b, TAG_Special, deststnr);
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setsign(dest, sign);
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return TAG_Special;
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}
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#ifdef PARANOID
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else {
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EXCEPTION(EX_INTERNAL | 0x102);
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return FPU_Exception;
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}
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#endif /* PARANOID */
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return 0;
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}
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