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-rw-r--r--gdb/ieee-float.c141
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diff --git a/gdb/ieee-float.c b/gdb/ieee-float.c
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+/* IEEE floating point support routines, for GDB, the GNU Debugger.
+ Copyright (C) 1991 Free Software Foundation, Inc.
+
+This file is part of GDB.
+
+GDB is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 1, or (at your option)
+any later version.
+
+GDB is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GDB; see the file COPYING. If not, write to
+the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
+
+#include "defs.h"
+#include "param.h"
+#include "ieee-float.h"
+#include <math.h> /* ldexp */
+
+/* Convert an IEEE extended float to a double.
+ FROM is the address of the extended float.
+ Store the double in *TO. */
+
+void
+ieee_extended_to_double (ext_format, from, to)
+ struct ext_format *ext_format;
+ char *from;
+ double *to;
+{
+ unsigned char *ufrom = (unsigned char *)from;
+ double dto;
+ unsigned long mant0, mant1, exp;
+
+ bcopy (&from[MANBYTE_H], &mant0, 4);
+ bcopy (&from[MANBYTE_L], &mant1, 4);
+ exp = ((ufrom[EXPBYTE_H] & (unsigned char)~SIGNMASK) << 8) | ufrom[EXPBYTE_L];
+
+ if (exp == EXT_EXP_NAN) {
+ /* We have a NaN source. */
+ dto = 0.123456789; /* Not much else useful to do */
+ } else if (exp == 0 && mant0 == 0 && mant1 == 0) {
+ dto = 0;
+ } else {
+ /* Build the result algebraically. Might go infinite, underflow, etc;
+ who cares. */
+ mant0 |= 0x80000000;
+ dto = ldexp ((double)mant0, exp - EXT_EXP_BIAS - 31);
+ dto += ldexp ((double)mant1, exp - EXT_EXP_BIAS - 31 - 32);
+ }
+ *to = dto;
+}
+
+/* The converse: convert the double *FROM to an extended float
+ and store where TO points. */
+
+void
+double_to_ieee_extended (ext_format, from, to)
+ struct ext_format *ext_format;
+ double *from;
+ char *to;
+{
+ double dfrom = *from;
+ unsigned long twolongs[2];
+ unsigned long mant0, mant1, exp;
+ unsigned char twobytes[2];
+
+ bzero (to, TOTALSIZE);
+ if (dfrom == 0)
+ return; /* Result is zero */
+ if (dfrom != dfrom) {
+ /* From is NaN */
+ to[EXPBYTE_H] = (unsigned char)(EXT_EXP_NAN >> 8);
+ to[EXPBYTE_L] = (unsigned char)EXT_EXP_NAN;
+ to[MANBYTE_H] = 1; /* Be sure it's not infinity, but NaN value is irrel */
+ return; /* Result is NaN */
+ }
+ if (dfrom < 0)
+ to[SIGNBYTE] |= SIGNMASK; /* Set negative sign */
+ /* How to tell an infinity from an ordinary number? FIXME-someday */
+
+ /* The following code assumes that the host has IEEE doubles. FIXME-someday.
+ It also assumes longs are 32 bits! FIXME-someday. */
+ bcopy (from, twolongs, 8);
+ bcopy (from, twobytes, 2);
+#if HOST_BYTE_ORDER == BIG_ENDIAN
+ exp = ((twobytes[1] & 0xF0) >> 4) | (twobytes[0] & 0x7F) << 4;
+ mant0 = (twolongs[0] << 11) | twolongs[1] >> 21;
+ mant1 = (twolongs[1] << 11);
+#else
+ exp = ((twobytes[0] & 0xF0) >> 4) | (twobytes[1] & 0x7F) << 4;
+ mant0 = (twolongs[1] << 11) | twolongs[0] >> 21;
+ mant1 = (twolongs[0] << 11);
+#endif
+
+ /* Fiddle with leading 1-bit, implied in double, explicit in extended. */
+ if (exp == 0)
+ mant0 &= 0x7FFFFFFF;
+ else
+ mant0 |= 0x80000000;
+
+ exp -= DBL_EXP_BIAS; /* Get integer exp */
+ exp += EXT_EXP_BIAS; /* Offset for extended *&/
+
+ /* OK, now store it in extended format. */
+ to[EXPBYTE_H] |= (unsigned char)(exp >> 8); /* Retain sign */
+ to[EXPBYTE_L] = (unsigned char) exp;
+
+ bcopy (&mant0, &to[MANBYTE_H], 4);
+ bcopy (&mant1, &to[MANBYTE_L], 4);
+}
+
+
+#ifdef DEBUG
+
+/* Test some numbers to see that extended/double conversion works for them. */
+
+ieee_test (n)
+ int n;
+{
+ union { double d; int i[2]; } di;
+ double result;
+ int i;
+ char exten[16];
+ extern struct ext_format ext_format_68881;
+
+ for (i = 0; i < n; i++) {
+ di.i[0] = random();
+ di.i[1] = random();
+ double_to_ieee_extended (ext_format_68881, &di.d, exten);
+ ieee_extended_to_double (ext_format_68881, exten, &result);
+ if (di.d != result)
+ printf ("Differ: %x %x %g => %x %x %g\n", di.d, di.d, result, result);
+ }
+}
+
+#endif