Johns release

1 files changed, 141 insertions, 0 deletions

diff --git a/gdb/ieee-float.c b/gdb/ieee-float.c
new file mode 100644
index 0000000..7b7f9f1
--- /dev/null
+++ b/gdb/ieee-float.c
@@ -0,0 +1,141 @@
+/* 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