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Diffstat (limited to 'gdb/ieee-float.c')
-rw-r--r-- | gdb/ieee-float.c | 141 |
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 |