Initial revision

1 files changed, 403 insertions, 0 deletions

diff --git a/libiberty/floatformat.c b/libiberty/floatformat.c
new file mode 100644
index 00000000000..c4f21e4ce89
--- /dev/null
+++ b/libiberty/floatformat.c
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+/* IEEE floating point support routines, for GDB, the GNU Debugger.
+   Copyright (C) 1991, 1994 Free Software Foundation, Inc.
+
+This file is part of GDB.
+
+This program 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 2 of the License, or
+(at your option) any later version.
+
+This program 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 this program; if not, write to the Free Software
+Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
+
+#include "floatformat.h"
+#include <math.h>		/* ldexp */
+#ifdef __STDC__
+#include <stddef.h>
+extern void *memcpy (void *s1, const void *s2, size_t n);
+extern void *memset (void *s, int c, size_t n);
+#else
+extern char *memcpy ();
+extern char *memset ();
+#endif
+
+/* The odds that CHAR_BIT will be anything but 8 are low enough that I'm not
+   going to bother with trying to muck around with whether it is defined in
+   a system header, what we do if not, etc.  */
+#define FLOATFORMAT_CHAR_BIT 8
+
+/* floatformats for IEEE single and double, big and little endian.  */
+const struct floatformat floatformat_ieee_single_big =
+{
+  floatformat_big, 32, 0, 1, 8, 127, 255, 9, 23, floatformat_intbit_no
+};
+const struct floatformat floatformat_ieee_single_little =
+{
+  floatformat_little, 32, 0, 1, 8, 127, 255, 9, 23, floatformat_intbit_no
+};
+const struct floatformat floatformat_ieee_double_big =
+{
+  floatformat_big, 64, 0, 1, 11, 1023, 2047, 12, 52, floatformat_intbit_no
+};
+const struct floatformat floatformat_ieee_double_little =
+{
+  floatformat_little, 64, 0, 1, 11, 1023, 2047, 12, 52, floatformat_intbit_no
+};
+
+/* floatformat for IEEE double, little endian byte order, with big endian word
+   ordering, as on the ARM.  */
+
+const struct floatformat floatformat_ieee_double_littlebyte_bigword =
+{
+  floatformat_littlebyte_bigword, 64, 0, 1, 11, 1023, 2047, 12, 52, floatformat_intbit_no
+};
+
+const struct floatformat floatformat_i387_ext =
+{
+  floatformat_little, 80, 0, 1, 15, 0x3fff, 0x7fff, 16, 64,
+  floatformat_intbit_yes
+};
+const struct floatformat floatformat_m68881_ext =
+{
+  /* Note that the bits from 16 to 31 are unused.  */
+  floatformat_big, 96, 0, 1, 15, 0x3fff, 0x7fff, 32, 64, floatformat_intbit_yes
+};
+const struct floatformat floatformat_i960_ext =
+{
+  /* Note that the bits from 0 to 15 are unused.  */
+  floatformat_little, 96, 16, 17, 15, 0x3fff, 0x7fff, 32, 64,
+  floatformat_intbit_yes
+};
+const struct floatformat floatformat_m88110_ext =
+{
+#ifdef HARRIS_FLOAT_FORMAT
+  /* Harris uses raw format 128 bytes long, but the number is just an ieee
+     double, and the last 64 bits are wasted. */
+  floatformat_big,128, 0, 1, 11,  0x3ff,  0x7ff, 12, 52,
+  floatformat_intbit_no
+#else
+  floatformat_big, 80, 0, 1, 15, 0x3fff, 0x7fff, 16, 64,
+  floatformat_intbit_yes
+#endif /* HARRIS_FLOAT_FORMAT */
+};
+const struct floatformat floatformat_arm_ext =
+{
+  /* Bits 1 to 16 are unused.  */
+  floatformat_big, 96, 0, 17, 15, 0x3fff, 0x7fff, 32, 64,
+  floatformat_intbit_yes
+};
+
+static unsigned long get_field PARAMS ((unsigned char *,
+					enum floatformat_byteorders,
+					unsigned int,
+					unsigned int,
+					unsigned int));
+
+/* Extract a field which starts at START and is LEN bytes long.  DATA and
+   TOTAL_LEN are the thing we are extracting it from, in byteorder ORDER.  */
+static unsigned long
+get_field (data, order, total_len, start, len)
+     unsigned char *data;
+     enum floatformat_byteorders order;
+     unsigned int total_len;
+     unsigned int start;
+     unsigned int len;
+{
+  unsigned long result;
+  unsigned int cur_byte;
+  int cur_bitshift;
+
+  /* Start at the least significant part of the field.  */
+  cur_byte = (start + len) / FLOATFORMAT_CHAR_BIT;
+  if (order == floatformat_little)
+    cur_byte = (total_len / FLOATFORMAT_CHAR_BIT) - cur_byte - 1;
+  cur_bitshift =
+    ((start + len) % FLOATFORMAT_CHAR_BIT) - FLOATFORMAT_CHAR_BIT;
+  result = *(data + cur_byte) >> (-cur_bitshift);
+  cur_bitshift += FLOATFORMAT_CHAR_BIT;
+  if (order == floatformat_little)
+    ++cur_byte;
+  else
+    --cur_byte;
+
+  /* Move towards the most significant part of the field.  */
+  while (cur_bitshift < len)
+    {
+      if (len - cur_bitshift < FLOATFORMAT_CHAR_BIT)
+	/* This is the last byte; zero out the bits which are not part of
+	   this field.  */
+	result |=
+	  (*(data + cur_byte) & ((1 << (len - cur_bitshift)) - 1))
+	    << cur_bitshift;
+      else
+	result |= *(data + cur_byte) << cur_bitshift;
+      cur_bitshift += FLOATFORMAT_CHAR_BIT;
+      if (order == floatformat_little)
+	++cur_byte;
+      else
+	--cur_byte;
+    }
+  return result;
+}
+  
+#ifndef min
+#define min(a, b) ((a) < (b) ? (a) : (b))
+#endif
+
+/* Convert from FMT to a double.
+   FROM is the address of the extended float.
+   Store the double in *TO.  */
+
+void
+floatformat_to_double (fmt, from, to)
+     const struct floatformat *fmt;
+     char *from;
+     double *to;
+{
+  unsigned char *ufrom = (unsigned char *)from;
+  double dto;
+  long exponent;
+  unsigned long mant;
+  unsigned int mant_bits, mant_off;
+  int mant_bits_left;
+  int special_exponent;		/* It's a NaN, denorm or zero */
+
+  exponent = get_field (ufrom, fmt->byteorder, fmt->totalsize,
+			fmt->exp_start, fmt->exp_len);
+  /* Note that if exponent indicates a NaN, we can't really do anything useful
+     (not knowing if the host has NaN's, or how to build one).  So it will
+     end up as an infinity or something close; that is OK.  */
+
+  mant_bits_left = fmt->man_len;
+  mant_off = fmt->man_start;
+  dto = 0.0;
+
+  special_exponent = exponent == 0 || exponent == fmt->exp_nan;
+
+  /* Don't bias zero's, denorms or NaNs.  */
+  if (!special_exponent)
+    exponent -= fmt->exp_bias;
+
+  /* Build the result algebraically.  Might go infinite, underflow, etc;
+     who cares. */
+
+  /* If this format uses a hidden bit, explicitly add it in now.  Otherwise,
+     increment the exponent by one to account for the integer bit.  */
+
+  if (!special_exponent)
+    {
+      if (fmt->intbit == floatformat_intbit_no)
+	dto = ldexp (1.0, exponent);
+      else
+	exponent++;
+    }
+
+  while (mant_bits_left > 0)
+    {
+      mant_bits = min (mant_bits_left, 32);
+
+      mant = get_field (ufrom, fmt->byteorder, fmt->totalsize,
+			 mant_off, mant_bits);
+
+      dto += ldexp ((double)mant, exponent - mant_bits);
+      exponent -= mant_bits;
+      mant_off += mant_bits;
+      mant_bits_left -= mant_bits;
+    }
+
+  /* Negate it if negative.  */
+  if (get_field (ufrom, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1))
+    dto = -dto;
+  *to = dto;
+}
+
+static void put_field PARAMS ((unsigned char *, enum floatformat_byteorders,
+			       unsigned int,
+			       unsigned int,
+			       unsigned int,
+			       unsigned long));
+
+/* Set a field which starts at START and is LEN bytes long.  DATA and
+   TOTAL_LEN are the thing we are extracting it from, in byteorder ORDER.  */
+static void
+put_field (data, order, total_len, start, len, stuff_to_put)
+     unsigned char *data;
+     enum floatformat_byteorders order;
+     unsigned int total_len;
+     unsigned int start;
+     unsigned int len;
+     unsigned long stuff_to_put;
+{
+  unsigned int cur_byte;
+  int cur_bitshift;
+
+  /* Start at the least significant part of the field.  */
+  cur_byte = (start + len) / FLOATFORMAT_CHAR_BIT;
+  if (order == floatformat_little)
+    cur_byte = (total_len / FLOATFORMAT_CHAR_BIT) - cur_byte - 1;
+  cur_bitshift =
+    ((start + len) % FLOATFORMAT_CHAR_BIT) - FLOATFORMAT_CHAR_BIT;
+  *(data + cur_byte) &=
+    ~(((1 << ((start + len) % FLOATFORMAT_CHAR_BIT)) - 1) << (-cur_bitshift));
+  *(data + cur_byte) |=
+    (stuff_to_put & ((1 << FLOATFORMAT_CHAR_BIT) - 1)) << (-cur_bitshift);
+  cur_bitshift += FLOATFORMAT_CHAR_BIT;
+  if (order == floatformat_little)
+    ++cur_byte;
+  else
+    --cur_byte;
+
+  /* Move towards the most significant part of the field.  */
+  while (cur_bitshift < len)
+    {
+      if (len - cur_bitshift < FLOATFORMAT_CHAR_BIT)
+	{
+	  /* This is the last byte.  */
+	  *(data + cur_byte) &=
+	    ~((1 << (len - cur_bitshift)) - 1);
+	  *(data + cur_byte) |= (stuff_to_put >> cur_bitshift);
+	}
+      else
+	*(data + cur_byte) = ((stuff_to_put >> cur_bitshift)
+			      & ((1 << FLOATFORMAT_CHAR_BIT) - 1));
+      cur_bitshift += FLOATFORMAT_CHAR_BIT;
+      if (order == floatformat_little)
+	++cur_byte;
+      else
+	--cur_byte;
+    }
+}
+
+/* The converse: convert the double *FROM to an extended float
+   and store where TO points.  Neither FROM nor TO have any alignment
+   restrictions.  */
+
+void
+floatformat_from_double (fmt, from, to)
+     const struct floatformat *fmt;
+     double *from;
+     char *to;
+{
+  double dfrom;
+  int exponent;
+  double mant;
+  unsigned int mant_bits, mant_off;
+  int mant_bits_left;
+  unsigned char *uto = (unsigned char *)to;
+
+  memcpy (&dfrom, from, sizeof (dfrom));
+  memset (uto, 0, fmt->totalsize / FLOATFORMAT_CHAR_BIT);
+  if (dfrom == 0)
+    return;			/* Result is zero */
+  if (dfrom != dfrom)
+    {
+      /* From is NaN */
+      put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start,
+		 fmt->exp_len, fmt->exp_nan);
+      /* Be sure it's not infinity, but NaN value is irrel */
+      put_field (uto, fmt->byteorder, fmt->totalsize, fmt->man_start,
+		 32, 1);
+      return;
+    }
+
+  /* If negative, set the sign bit.  */
+  if (dfrom < 0)
+    {
+      put_field (uto, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1, 1);
+      dfrom = -dfrom;
+    }
+
+  /* How to tell an infinity from an ordinary number?  FIXME-someday */
+
+  mant = frexp (dfrom, &exponent);
+  put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start, fmt->exp_len,
+	     exponent + fmt->exp_bias - 1);
+
+  mant_bits_left = fmt->man_len;
+  mant_off = fmt->man_start;
+  while (mant_bits_left > 0)
+    {
+      unsigned long mant_long;
+      mant_bits = mant_bits_left < 32 ? mant_bits_left : 32;
+
+      mant *= 4294967296.0;
+      mant_long = (unsigned long)mant;
+      mant -= mant_long;
+
+      /* If the integer bit is implicit, then we need to discard it.
+	 If we are discarding a zero, we should be (but are not) creating
+	 a denormalized	number which means adjusting the exponent
+	 (I think).  */
+      if (mant_bits_left == fmt->man_len
+	  && fmt->intbit == floatformat_intbit_no)
+	{
+	  mant_long &= 0x7fffffff;
+	  mant_bits -= 1;
+	}
+      else if (mant_bits < 32)
+	{
+	  /* The bits we want are in the most significant MANT_BITS bits of
+	     mant_long.  Move them to the least significant.  */
+	  mant_long >>= 32 - mant_bits;
+	}
+
+      put_field (uto, fmt->byteorder, fmt->totalsize,
+		 mant_off, mant_bits, mant_long);
+      mant_off += mant_bits;
+      mant_bits_left -= mant_bits;
+    }
+}
+
+
+#ifdef IEEE_DEBUG
+
+/* This is to be run on a host which uses IEEE floating point.  */
+
+void
+ieee_test (n)
+     double n;
+{
+  double result;
+  char exten[16];
+
+  floatformat_to_double (&floatformat_ieee_double_big, &n, &result);
+  if (n != result)
+    printf ("Differ(to): %.20g -> %.20g\n", n, result);
+  floatformat_from_double (&floatformat_ieee_double_big, &n, &result);
+  if (n != result)
+    printf ("Differ(from): %.20g -> %.20g\n", n, result);
+
+  floatformat_from_double (&floatformat_m68881_ext, &n, exten);
+  floatformat_to_double (&floatformat_m68881_ext, exten, &result);
+  if (n != result)
+    printf ("Differ(to+from): %.20g -> %.20g\n", n, result);
+
+#if IEEE_DEBUG > 1
+  /* This is to be run on a host which uses 68881 format.  */
+  {
+    long double ex = *(long double *)exten;
+    if (ex != n)
+      printf ("Differ(from vs. extended): %.20g\n", n);
+  }
+#endif
+}
+
+int
+main ()
+{
+  ieee_test (0.5);
+  ieee_test (256.0);
+  ieee_test (0.12345);
+  ieee_test (234235.78907234);
+  ieee_test (-512.0);
+  ieee_test (-0.004321);
+  return 0;
+}
+#endif