184 lines
4.9 KiB
C
184 lines
4.9 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*---------------------------------------------------------------------------+
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| reg_divide.c |
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| Divide one FPU_REG by another and put the result in a destination FPU_REG.|
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| Copyright (C) 1996 |
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| W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
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| E-mail billm@jacobi.maths.monash.edu.au |
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| Return value is the tag of the answer, or-ed with FPU_Exception if |
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| one was raised, or -1 on internal error. |
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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 "exception.h"
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#include "reg_constant.h"
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#include "fpu_emu.h"
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#include "fpu_system.h"
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/*
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Divide one register by another and put the result into a third register.
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*/
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int FPU_div(int flags, int rm, int control_w)
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{
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FPU_REG x, y;
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FPU_REG const *a, *b, *st0_ptr, *st_ptr;
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FPU_REG *dest;
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u_char taga, tagb, signa, signb, sign, saved_sign;
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int tag, deststnr;
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if (flags & DEST_RM)
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deststnr = rm;
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else
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deststnr = 0;
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if (flags & REV) {
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b = &st(0);
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st0_ptr = b;
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tagb = FPU_gettag0();
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if (flags & LOADED) {
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a = (FPU_REG *) rm;
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taga = flags & 0x0f;
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} else {
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a = &st(rm);
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st_ptr = a;
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taga = FPU_gettagi(rm);
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}
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} else {
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a = &st(0);
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st0_ptr = a;
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taga = FPU_gettag0();
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if (flags & LOADED) {
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b = (FPU_REG *) rm;
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tagb = flags & 0x0f;
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} else {
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b = &st(rm);
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st_ptr = b;
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tagb = FPU_gettagi(rm);
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}
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}
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signa = getsign(a);
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signb = getsign(b);
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sign = signa ^ signb;
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dest = &st(deststnr);
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saved_sign = getsign(dest);
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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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reg_copy(a, &x);
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reg_copy(b, &y);
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setpositive(&x);
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setpositive(&y);
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tag = FPU_u_div(&x, &y, dest, control_w, sign);
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if (tag < 0)
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return tag;
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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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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_div(&x, &y, dest, control_w, sign);
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if (tag < 0)
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return tag;
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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 != TAG_Zero) {
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/* Want to find Zero/Valid */
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if (tagb == TW_Denormal) {
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if (denormal_operand() < 0)
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return FPU_Exception;
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}
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/* The result is zero. */
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FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
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setsign(dest, sign);
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return TAG_Zero;
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}
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/* We have an exception condition, either 0/0 or Valid/Zero. */
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if (taga == TAG_Zero) {
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/* 0/0 */
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return arith_invalid(deststnr);
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}
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/* Valid/Zero */
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return FPU_divide_by_zero(deststnr, sign);
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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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if (flags & LOADED)
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return real_2op_NaN((FPU_REG *) rm, flags & 0x0f, 0,
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st0_ptr);
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if (flags & DEST_RM) {
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int tag;
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tag = FPU_gettag0();
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if (tag == TAG_Special)
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tag = FPU_Special(st0_ptr);
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return real_2op_NaN(st0_ptr, tag, rm,
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(flags & REV) ? st0_ptr : &st(rm));
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} else {
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int tag;
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tag = FPU_gettagi(rm);
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if (tag == TAG_Special)
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tag = FPU_Special(&st(rm));
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return real_2op_NaN(&st(rm), tag, 0,
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(flags & REV) ? st0_ptr : &st(rm));
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}
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} else if (taga == TW_Infinity) {
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if (tagb == TW_Infinity) {
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/* infinity/infinity */
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return arith_invalid(deststnr);
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} else {
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/* tagb must be Valid or Zero */
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if ((tagb == TW_Denormal) && (denormal_operand() < 0))
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return FPU_Exception;
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/* Infinity divided by Zero or Valid does
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not raise and exception, but returns 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 taga;
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}
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} else if (tagb == TW_Infinity) {
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if ((taga == TW_Denormal) && (denormal_operand() < 0))
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return FPU_Exception;
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/* The result is zero. */
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FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
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setsign(dest, sign);
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return TAG_Zero;
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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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