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-rw-r--r--kernel/arch/x86/math-emu/reg_mul.c115
1 files changed, 115 insertions, 0 deletions
diff --git a/kernel/arch/x86/math-emu/reg_mul.c b/kernel/arch/x86/math-emu/reg_mul.c
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+++ b/kernel/arch/x86/math-emu/reg_mul.c
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+/*---------------------------------------------------------------------------+
+ | reg_mul.c |
+ | |
+ | Multiply one FPU_REG by another, put the result in a destination FPU_REG. |
+ | |
+ | Copyright (C) 1992,1993,1997 |
+ | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
+ | E-mail billm@suburbia.net |
+ | |
+ | Returns the tag of the result if no exceptions or errors occurred. |
+ | |
+ +---------------------------------------------------------------------------*/
+
+/*---------------------------------------------------------------------------+
+ | The destination may be any FPU_REG, including one of the source FPU_REGs. |
+ +---------------------------------------------------------------------------*/
+
+#include "fpu_emu.h"
+#include "exception.h"
+#include "reg_constant.h"
+#include "fpu_system.h"
+
+/*
+ Multiply two registers to give a register result.
+ The sources are st(deststnr) and (b,tagb,signb).
+ The destination is st(deststnr).
+ */
+/* This routine must be called with non-empty source registers */
+int FPU_mul(FPU_REG const *b, u_char tagb, int deststnr, int control_w)
+{
+ FPU_REG *a = &st(deststnr);
+ FPU_REG *dest = a;
+ u_char taga = FPU_gettagi(deststnr);
+ u_char saved_sign = getsign(dest);
+ u_char sign = (getsign(a) ^ getsign(b));
+ int tag;
+
+ if (!(taga | tagb)) {
+ /* Both regs Valid, this should be the most common case. */
+
+ tag =
+ FPU_u_mul(a, b, dest, control_w, sign,
+ exponent(a) + exponent(b));
+ 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);
+ tag = FPU_u_mul(&x, &y, dest, control_w, sign,
+ exponent16(&x) + exponent16(&y));
+ if (tag < 0) {
+ setsign(dest, saved_sign);
+ return tag;
+ }
+ FPU_settagi(deststnr, tag);
+ return tag;
+ } else if ((taga <= TW_Denormal) && (tagb <= TW_Denormal)) {
+ if (((tagb == TW_Denormal) || (taga == TW_Denormal))
+ && (denormal_operand() < 0))
+ return FPU_Exception;
+
+ /* Must have either both arguments == zero, or
+ one valid and the other zero.
+ The result is therefore zero. */
+ FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
+ /* The 80486 book says that the answer is +0, but a real
+ 80486 behaves this way.
+ IEEE-754 apparently says it should be this way. */
+ setsign(dest, sign);
+ return TAG_Zero;
+ }
+ /* Must have infinities, NaNs, etc */
+ else if ((taga == TW_NaN) || (tagb == TW_NaN)) {
+ return real_2op_NaN(b, tagb, deststnr, &st(0));
+ } else if (((taga == TW_Infinity) && (tagb == TAG_Zero))
+ || ((tagb == TW_Infinity) && (taga == TAG_Zero))) {
+ return arith_invalid(deststnr); /* Zero*Infinity is invalid */
+ } else if (((taga == TW_Denormal) || (tagb == TW_Denormal))
+ && (denormal_operand() < 0)) {
+ return FPU_Exception;
+ } else if (taga == TW_Infinity) {
+ FPU_copy_to_regi(a, TAG_Special, deststnr);
+ setsign(dest, sign);
+ return TAG_Special;
+ } else if (tagb == TW_Infinity) {
+ FPU_copy_to_regi(b, TAG_Special, deststnr);
+ setsign(dest, sign);
+ return TAG_Special;
+ }
+#ifdef PARANOID
+ else {
+ EXCEPTION(EX_INTERNAL | 0x102);
+ return FPU_Exception;
+ }
+#endif /* PARANOID */
+
+ return 0;
+}