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-rw-r--r--arch/x86/math-emu/reg_add_sub.c334
1 files changed, 334 insertions, 0 deletions
diff --git a/arch/x86/math-emu/reg_add_sub.c b/arch/x86/math-emu/reg_add_sub.c
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+++ b/arch/x86/math-emu/reg_add_sub.c
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+// SPDX-License-Identifier: GPL-2.0
+/*---------------------------------------------------------------------------+
+ | reg_add_sub.c |
+ | |
+ | Functions to add or subtract two registers and put the result in a third. |
+ | |
+ | Copyright (C) 1992,1993,1997 |
+ | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
+ | E-mail billm@suburbia.net |
+ | |
+ | |
+ +---------------------------------------------------------------------------*/
+
+/*---------------------------------------------------------------------------+
+ | For each function, the destination may be any FPU_REG, including one of |
+ | the source FPU_REGs. |
+ | Each function returns 0 if the answer is o.k., otherwise a non-zero |
+ | value is returned, indicating either an exception condition or an |
+ | internal error. |
+ +---------------------------------------------------------------------------*/
+
+#include "exception.h"
+#include "reg_constant.h"
+#include "fpu_emu.h"
+#include "control_w.h"
+#include "fpu_system.h"
+
+static
+int add_sub_specials(FPU_REG const *a, u_char taga, u_char signa,
+ FPU_REG const *b, u_char tagb, u_char signb,
+ FPU_REG * dest, int deststnr, int control_w);
+
+/*
+ Operates on st(0) and st(n), or on st(0) and temporary data.
+ The destination must be one of the source st(x).
+ */
+int FPU_add(FPU_REG const *b, u_char tagb, int deststnr, int control_w)
+{
+ FPU_REG *a = &st(0);
+ FPU_REG *dest = &st(deststnr);
+ u_char signb = getsign(b);
+ u_char taga = FPU_gettag0();
+ u_char signa = getsign(a);
+ u_char saved_sign = getsign(dest);
+ int diff, tag, expa, expb;
+
+ if (!(taga | tagb)) {
+ expa = exponent(a);
+ expb = exponent(b);
+
+ valid_add:
+ /* Both registers are valid */
+ if (!(signa ^ signb)) {
+ /* signs are the same */
+ tag =
+ FPU_u_add(a, b, dest, control_w, signa, expa, expb);
+ } else {
+ /* The signs are different, so do a subtraction */
+ diff = expa - expb;
+ if (!diff) {
+ diff = a->sigh - b->sigh; /* This works only if the ms bits
+ are identical. */
+ if (!diff) {
+ diff = a->sigl > b->sigl;
+ if (!diff)
+ diff = -(a->sigl < b->sigl);
+ }
+ }
+
+ if (diff > 0) {
+ tag =
+ FPU_u_sub(a, b, dest, control_w, signa,
+ expa, expb);
+ } else if (diff < 0) {
+ tag =
+ FPU_u_sub(b, a, dest, control_w, signb,
+ expb, expa);
+ } else {
+ FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
+ /* sign depends upon rounding mode */
+ setsign(dest, ((control_w & CW_RC) != RC_DOWN)
+ ? SIGN_POS : SIGN_NEG);
+ return TAG_Zero;
+ }
+ }
+
+ if (tag < 0) {
+ setsign(dest, saved_sign);
+ return tag;
+ }
+ FPU_settagi(deststnr, tag);
+ return tag;
+ }
+
+ if (taga == TAG_Special)
+ taga = FPU_Special(a);
+ if (tagb == TAG_Special)
+ tagb = FPU_Special(b);
+
+ if (((taga == TAG_Valid) && (tagb == TW_Denormal))
+ || ((taga == TW_Denormal) && (tagb == TAG_Valid))
+ || ((taga == TW_Denormal) && (tagb == TW_Denormal))) {
+ FPU_REG x, y;
+
+ if (denormal_operand() < 0)
+ return FPU_Exception;
+
+ FPU_to_exp16(a, &x);
+ FPU_to_exp16(b, &y);
+ a = &x;
+ b = &y;
+ expa = exponent16(a);
+ expb = exponent16(b);
+ goto valid_add;
+ }
+
+ if ((taga == TW_NaN) || (tagb == TW_NaN)) {
+ if (deststnr == 0)
+ return real_2op_NaN(b, tagb, deststnr, a);
+ else
+ return real_2op_NaN(a, taga, deststnr, a);
+ }
+
+ return add_sub_specials(a, taga, signa, b, tagb, signb,
+ dest, deststnr, control_w);
+}
+
+/* Subtract b from a. (a-b) -> dest */
+int FPU_sub(int flags, int rm, int control_w)
+{
+ FPU_REG const *a, *b;
+ FPU_REG *dest;
+ u_char taga, tagb, signa, signb, saved_sign, sign;
+ int diff, tag = 0, expa, expb, deststnr;
+
+ a = &st(0);
+ taga = FPU_gettag0();
+
+ deststnr = 0;
+ if (flags & LOADED) {
+ b = (FPU_REG *) rm;
+ tagb = flags & 0x0f;
+ } else {
+ b = &st(rm);
+ tagb = FPU_gettagi(rm);
+
+ if (flags & DEST_RM)
+ deststnr = rm;
+ }
+
+ signa = getsign(a);
+ signb = getsign(b);
+
+ if (flags & REV) {
+ signa ^= SIGN_NEG;
+ signb ^= SIGN_NEG;
+ }
+
+ dest = &st(deststnr);
+ saved_sign = getsign(dest);
+
+ if (!(taga | tagb)) {
+ expa = exponent(a);
+ expb = exponent(b);
+
+ valid_subtract:
+ /* Both registers are valid */
+
+ diff = expa - expb;
+
+ if (!diff) {
+ diff = a->sigh - b->sigh; /* Works only if ms bits are identical */
+ if (!diff) {
+ diff = a->sigl > b->sigl;
+ if (!diff)
+ diff = -(a->sigl < b->sigl);
+ }
+ }
+
+ switch ((((int)signa) * 2 + signb) / SIGN_NEG) {
+ case 0: /* P - P */
+ case 3: /* N - N */
+ if (diff > 0) {
+ /* |a| > |b| */
+ tag =
+ FPU_u_sub(a, b, dest, control_w, signa,
+ expa, expb);
+ } else if (diff == 0) {
+ FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
+
+ /* sign depends upon rounding mode */
+ setsign(dest, ((control_w & CW_RC) != RC_DOWN)
+ ? SIGN_POS : SIGN_NEG);
+ return TAG_Zero;
+ } else {
+ sign = signa ^ SIGN_NEG;
+ tag =
+ FPU_u_sub(b, a, dest, control_w, sign, expb,
+ expa);
+ }
+ break;
+ case 1: /* P - N */
+ tag =
+ FPU_u_add(a, b, dest, control_w, SIGN_POS, expa,
+ expb);
+ break;
+ case 2: /* N - P */
+ tag =
+ FPU_u_add(a, b, dest, control_w, SIGN_NEG, expa,
+ expb);
+ break;
+#ifdef PARANOID
+ default:
+ EXCEPTION(EX_INTERNAL | 0x111);
+ return -1;
+#endif
+ }
+ if (tag < 0) {
+ setsign(dest, saved_sign);
+ return tag;
+ }
+ FPU_settagi(deststnr, tag);
+ return tag;
+ }
+
+ if (taga == TAG_Special)
+ taga = FPU_Special(a);
+ if (tagb == TAG_Special)
+ tagb = FPU_Special(b);
+
+ if (((taga == TAG_Valid) && (tagb == TW_Denormal))
+ || ((taga == TW_Denormal) && (tagb == TAG_Valid))
+ || ((taga == TW_Denormal) && (tagb == TW_Denormal))) {
+ FPU_REG x, y;
+
+ if (denormal_operand() < 0)
+ return FPU_Exception;
+
+ FPU_to_exp16(a, &x);
+ FPU_to_exp16(b, &y);
+ a = &x;
+ b = &y;
+ expa = exponent16(a);
+ expb = exponent16(b);
+
+ goto valid_subtract;
+ }
+
+ if ((taga == TW_NaN) || (tagb == TW_NaN)) {
+ FPU_REG const *d1, *d2;
+ if (flags & REV) {
+ d1 = b;
+ d2 = a;
+ } else {
+ d1 = a;
+ d2 = b;
+ }
+ if (flags & LOADED)
+ return real_2op_NaN(b, tagb, deststnr, d1);
+ if (flags & DEST_RM)
+ return real_2op_NaN(a, taga, deststnr, d2);
+ else
+ return real_2op_NaN(b, tagb, deststnr, d2);
+ }
+
+ return add_sub_specials(a, taga, signa, b, tagb, signb ^ SIGN_NEG,
+ dest, deststnr, control_w);
+}
+
+static
+int add_sub_specials(FPU_REG const *a, u_char taga, u_char signa,
+ FPU_REG const *b, u_char tagb, u_char signb,
+ FPU_REG * dest, int deststnr, int control_w)
+{
+ if (((taga == TW_Denormal) || (tagb == TW_Denormal))
+ && (denormal_operand() < 0))
+ return FPU_Exception;
+
+ if (taga == TAG_Zero) {
+ if (tagb == TAG_Zero) {
+ /* Both are zero, result will be zero. */
+ u_char different_signs = signa ^ signb;
+
+ FPU_copy_to_regi(a, TAG_Zero, deststnr);
+ if (different_signs) {
+ /* Signs are different. */
+ /* Sign of answer depends upon rounding mode. */
+ setsign(dest, ((control_w & CW_RC) != RC_DOWN)
+ ? SIGN_POS : SIGN_NEG);
+ } else
+ setsign(dest, signa); /* signa may differ from the sign of a. */
+ return TAG_Zero;
+ } else {
+ reg_copy(b, dest);
+ if ((tagb == TW_Denormal) && (b->sigh & 0x80000000)) {
+ /* A pseudoDenormal, convert it. */
+ addexponent(dest, 1);
+ tagb = TAG_Valid;
+ } else if (tagb > TAG_Empty)
+ tagb = TAG_Special;
+ setsign(dest, signb); /* signb may differ from the sign of b. */
+ FPU_settagi(deststnr, tagb);
+ return tagb;
+ }
+ } else if (tagb == TAG_Zero) {
+ reg_copy(a, dest);
+ if ((taga == TW_Denormal) && (a->sigh & 0x80000000)) {
+ /* A pseudoDenormal */
+ addexponent(dest, 1);
+ taga = TAG_Valid;
+ } else if (taga > TAG_Empty)
+ taga = TAG_Special;
+ setsign(dest, signa); /* signa may differ from the sign of a. */
+ FPU_settagi(deststnr, taga);
+ return taga;
+ } else if (taga == TW_Infinity) {
+ if ((tagb != TW_Infinity) || (signa == signb)) {
+ FPU_copy_to_regi(a, TAG_Special, deststnr);
+ setsign(dest, signa); /* signa may differ from the sign of a. */
+ return taga;
+ }
+ /* Infinity-Infinity is undefined. */
+ return arith_invalid(deststnr);
+ } else if (tagb == TW_Infinity) {
+ FPU_copy_to_regi(b, TAG_Special, deststnr);
+ setsign(dest, signb); /* signb may differ from the sign of b. */
+ return tagb;
+ }
+#ifdef PARANOID
+ EXCEPTION(EX_INTERNAL | 0x101);
+#endif
+
+ return FPU_Exception;
+}
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