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Diffstat (limited to 'libiberty/floatformat.c')
| -rw-r--r-- | libiberty/floatformat.c | 401 |
1 files changed, 401 insertions, 0 deletions
diff --git a/libiberty/floatformat.c b/libiberty/floatformat.c new file mode 100644 index 00000000000..7f6086f4306 --- /dev/null +++ b/libiberty/floatformat.c @@ -0,0 +1,401 @@ +/* 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 |