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527 lines
14 KiB
C
527 lines
14 KiB
C
/* atof_ieee.c - turn a Flonum into an IEEE floating point number
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Copyright (C) 1987, 1992 Free Software Foundation, Inc.
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This file is part of GAS, the GNU Assembler.
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GAS is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GAS is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GAS; see the file COPYING. If not, write to
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the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
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#include "as.h"
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#ifdef USG
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#define bzero(s,n) memset(s,0,n)
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#define bcopy(from,to,n) memcpy((to),(from),(n))
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#endif
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extern FLONUM_TYPE generic_floating_point_number; /* Flonums returned here. */
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#ifndef NULL
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#define NULL (0)
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#endif
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extern char EXP_CHARS[];
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/* Precision in LittleNums. */
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#define MAX_PRECISION (6)
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#define F_PRECISION (2)
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#define D_PRECISION (4)
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#define X_PRECISION (6)
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#define P_PRECISION (6)
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/* Length in LittleNums of guard bits. */
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#define GUARD (2)
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static unsigned long mask [] = {
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0x00000000,
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0x00000001,
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0x00000003,
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0x00000007,
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0x0000000f,
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0x0000001f,
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0x0000003f,
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0x0000007f,
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0x000000ff,
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0x000001ff,
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0x000003ff,
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0x000007ff,
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0x00000fff,
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0x00001fff,
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0x00003fff,
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0x00007fff,
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0x0000ffff,
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0x0001ffff,
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0x0003ffff,
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0x0007ffff,
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0x000fffff,
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0x001fffff,
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0x003fffff,
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0x007fffff,
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0x00ffffff,
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0x01ffffff,
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0x03ffffff,
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0x07ffffff,
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0x0fffffff,
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0x1fffffff,
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0x3fffffff,
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0x7fffffff,
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0xffffffff,
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};
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static int bits_left_in_littlenum;
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static int littlenums_left;
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static LITTLENUM_TYPE *littlenum_pointer;
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static int
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next_bits (number_of_bits)
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int number_of_bits;
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{
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int return_value;
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if (!littlenums_left)
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return(0);
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if (number_of_bits >= bits_left_in_littlenum) {
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return_value = mask[bits_left_in_littlenum] & *littlenum_pointer;
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number_of_bits -= bits_left_in_littlenum;
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return_value <<= number_of_bits;
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if (--littlenums_left) {
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bits_left_in_littlenum = LITTLENUM_NUMBER_OF_BITS - number_of_bits;
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--littlenum_pointer;
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return_value |= (*littlenum_pointer >> bits_left_in_littlenum) & mask[number_of_bits];
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}
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} else {
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bits_left_in_littlenum -= number_of_bits;
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return_value = mask[number_of_bits] & (*littlenum_pointer >> bits_left_in_littlenum);
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}
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return(return_value);
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}
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/* Num had better be less than LITTLENUM_NUMBER_OF_BITS */
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static void
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unget_bits(num)
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int num;
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{
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if (!littlenums_left) {
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++littlenum_pointer;
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++littlenums_left;
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bits_left_in_littlenum = num;
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} else if (bits_left_in_littlenum + num > LITTLENUM_NUMBER_OF_BITS) {
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bits_left_in_littlenum = num - (LITTLENUM_NUMBER_OF_BITS - bits_left_in_littlenum);
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++littlenum_pointer;
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++littlenums_left;
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} else
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bits_left_in_littlenum += num;
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}
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static void
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make_invalid_floating_point_number(words)
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LITTLENUM_TYPE *words;
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{
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as_bad("cannot create floating-point number");
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words[0] = ((unsigned) -1) >> 1; /* Zero the leftmost bit */
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words[1] = -1;
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words[2] = -1;
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words[3] = -1;
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words[4] = -1;
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words[5] = -1;
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}
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/***********************************************************************\
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* Warning: this returns 16-bit LITTLENUMs. It is up to the caller *
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* to figure out any alignment problems and to conspire for the *
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* bytes/word to be emitted in the right order. Bigendians beware! *
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* *
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\***********************************************************************/
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/* Note that atof-ieee always has X and P precisions enabled. it is up
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to md_atof to filter them out if the target machine does not support
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them. */
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char * /* Return pointer past text consumed. */
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atof_ieee(str, what_kind, words)
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char *str; /* Text to convert to binary. */
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char what_kind; /* 'd', 'f', 'g', 'h' */
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LITTLENUM_TYPE *words; /* Build the binary here. */
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{
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static LITTLENUM_TYPE bits[MAX_PRECISION + MAX_PRECISION + GUARD];
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/* Extra bits for zeroed low-order bits. */
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/* The 1st MAX_PRECISION are zeroed, */
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/* the last contain flonum bits. */
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char *return_value;
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int precision; /* Number of 16-bit words in the format. */
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long exponent_bits;
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FLONUM_TYPE save_gen_flonum;
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/* We have to save the generic_floating_point_number because it
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contains storage allocation about the array of LITTLENUMs
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where the value is actually stored. We will allocate our
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own array of littlenums below, but have to restore the global
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one on exit. */
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save_gen_flonum = generic_floating_point_number;
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return_value = str;
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generic_floating_point_number.low = bits + MAX_PRECISION;
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generic_floating_point_number.high = NULL;
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generic_floating_point_number.leader = NULL;
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generic_floating_point_number.exponent = NULL;
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generic_floating_point_number.sign = '\0';
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/* Use more LittleNums than seems */
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/* necessary: the highest flonum may have */
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/* 15 leading 0 bits, so could be useless. */
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bzero(bits, sizeof(LITTLENUM_TYPE) * MAX_PRECISION);
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switch (what_kind) {
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case 'f':
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case 'F':
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case 's':
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case 'S':
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precision = F_PRECISION;
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exponent_bits = 8;
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break;
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case 'd':
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case 'D':
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case 'r':
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case 'R':
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precision = D_PRECISION;
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exponent_bits = 11;
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break;
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case 'x':
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case 'X':
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case 'e':
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case 'E':
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precision = X_PRECISION;
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exponent_bits = 15;
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break;
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case 'p':
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case 'P':
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precision = P_PRECISION;
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exponent_bits = -1;
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break;
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default:
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make_invalid_floating_point_number(words);
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return(NULL);
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}
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generic_floating_point_number.high = generic_floating_point_number.low + precision - 1 + GUARD;
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if (atof_generic(&return_value, ".", EXP_CHARS, &generic_floating_point_number)) {
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/* as_bad("Error converting floating point number (Exponent overflow?)"); */
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make_invalid_floating_point_number(words);
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return(NULL);
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}
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gen_to_words(words, precision, exponent_bits);
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/* Restore the generic_floating_point_number's storage alloc
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(and everything else). */
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generic_floating_point_number = save_gen_flonum;
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return(return_value);
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}
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/* Turn generic_floating_point_number into a real float/double/extended */
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int gen_to_words(words, precision, exponent_bits)
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LITTLENUM_TYPE *words;
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int precision;
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long exponent_bits;
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{
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int return_value = 0;
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long exponent_1;
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long exponent_2;
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long exponent_3;
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long exponent_4;
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int exponent_skippage;
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LITTLENUM_TYPE word1;
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LITTLENUM_TYPE *lp;
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if (generic_floating_point_number.low > generic_floating_point_number.leader) {
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/* 0.0e0 seen. */
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if (generic_floating_point_number.sign == '+')
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words[0] = 0x0000;
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else
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words[0] = 0x8000;
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bzero(&words[1], sizeof(LITTLENUM_TYPE) * (precision - 1));
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return(return_value);
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}
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/* NaN: Do the right thing */
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if (generic_floating_point_number.sign == 0) {
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if (precision == F_PRECISION) {
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words[0] = 0x7fff;
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words[1] = 0xffff;
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} else {
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words[0] = 0x7fff;
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words[1] = 0xffff;
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words[2] = 0xffff;
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words[3] = 0xffff;
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}
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return return_value;
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} else if (generic_floating_point_number.sign == 'P') {
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/* +INF: Do the right thing */
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if (precision == F_PRECISION) {
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words[0] = 0x7f80;
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words[1] = 0;
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} else {
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words[0] = 0x7ff0;
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words[1] = 0;
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words[2] = 0;
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words[3] = 0;
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}
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return(return_value);
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} else if (generic_floating_point_number.sign == 'N') {
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/* Negative INF */
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if (precision == F_PRECISION) {
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words[0] = 0xff80;
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words[1] = 0x0;
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} else {
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words[0] = 0xfff0;
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words[1] = 0x0;
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words[2] = 0x0;
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words[3] = 0x0;
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}
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return(return_value);
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}
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/*
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* The floating point formats we support have:
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* Bit 15 is sign bit.
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* Bits 14:n are excess-whatever exponent.
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* Bits n-1:0 (if any) are most significant bits of fraction.
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* Bits 15:0 of the next word(s) are the next most significant bits.
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*
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* So we need: number of bits of exponent, number of bits of
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* mantissa.
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*/
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bits_left_in_littlenum = LITTLENUM_NUMBER_OF_BITS;
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littlenum_pointer = generic_floating_point_number.leader;
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littlenums_left = 1 + generic_floating_point_number.leader - generic_floating_point_number.low;
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/* Seek (and forget) 1st significant bit */
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for (exponent_skippage = 0;! next_bits(1); exponent_skippage ++) ;;
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exponent_1 = generic_floating_point_number.exponent + generic_floating_point_number.leader
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+ 1 - generic_floating_point_number.low;
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/* Radix LITTLENUM_RADIX, point just higher than generic_floating_point_number.leader. */
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exponent_2 = exponent_1 * LITTLENUM_NUMBER_OF_BITS;
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/* Radix 2. */
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exponent_3 = exponent_2 - exponent_skippage;
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/* Forget leading zeros, forget 1st bit. */
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exponent_4 = exponent_3 + ((1 << (exponent_bits - 1)) - 2);
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/* Offset exponent. */
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lp = words;
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/* Word 1. Sign, exponent and perhaps high bits. */
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word1 = (generic_floating_point_number.sign == '+') ? 0 : (1 << (LITTLENUM_NUMBER_OF_BITS - 1));
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/* Assume 2's complement integers. */
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if (exponent_4 < 1 && exponent_4 >= -62) {
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int prec_bits;
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int num_bits;
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unget_bits(1);
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num_bits = -exponent_4;
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prec_bits = LITTLENUM_NUMBER_OF_BITS * precision - (exponent_bits + 1 + num_bits);
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if(precision == X_PRECISION && exponent_bits == 15)
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prec_bits -= LITTLENUM_NUMBER_OF_BITS + 1;
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if (num_bits >= LITTLENUM_NUMBER_OF_BITS - exponent_bits) {
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/* Bigger than one littlenum */
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num_bits -= (LITTLENUM_NUMBER_OF_BITS - 1) - exponent_bits;
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*lp++ = word1;
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if (num_bits + exponent_bits + 1 >= precision * LITTLENUM_NUMBER_OF_BITS) {
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/* Exponent overflow */
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make_invalid_floating_point_number(words);
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return(return_value);
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}
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if (precision == X_PRECISION && exponent_bits == 15) {
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*lp++ = 0;
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*lp++ = 0;
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num_bits -= LITTLENUM_NUMBER_OF_BITS - 1;
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}
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while (num_bits >= LITTLENUM_NUMBER_OF_BITS) {
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num_bits -= LITTLENUM_NUMBER_OF_BITS;
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*lp++ = 0;
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}
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if (num_bits)
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*lp++ = next_bits(LITTLENUM_NUMBER_OF_BITS - (num_bits));
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} else {
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if (precision == X_PRECISION && exponent_bits == 15) {
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*lp++ = word1;
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*lp++ = 0;
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if (num_bits == LITTLENUM_NUMBER_OF_BITS) {
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*lp++ = 0;
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*lp++ = next_bits(LITTLENUM_NUMBER_OF_BITS - 1);
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} else if (num_bits == LITTLENUM_NUMBER_OF_BITS - 1)
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*lp++ = 0;
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else
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*lp++ = next_bits(LITTLENUM_NUMBER_OF_BITS - 1 - num_bits);
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num_bits = 0;
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} else {
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word1 |= next_bits((LITTLENUM_NUMBER_OF_BITS - 1) - (exponent_bits + num_bits));
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*lp++ = word1;
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}
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}
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while (lp < words + precision)
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*lp++ = next_bits(LITTLENUM_NUMBER_OF_BITS);
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/* Round the mantissa up, but don't change the number */
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if (next_bits(1)) {
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--lp;
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if (prec_bits > LITTLENUM_NUMBER_OF_BITS) {
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int n = 0;
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int tmp_bits;
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n = 0;
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tmp_bits = prec_bits;
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while (tmp_bits > LITTLENUM_NUMBER_OF_BITS) {
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if (lp[n] != (LITTLENUM_TYPE) - 1)
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break;
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--n;
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tmp_bits -= LITTLENUM_NUMBER_OF_BITS;
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}
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if (tmp_bits > LITTLENUM_NUMBER_OF_BITS || (lp[n] & mask[tmp_bits]) != mask[tmp_bits]) {
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unsigned long carry;
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for (carry = 1; carry && (lp >= words); lp --) {
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carry = *lp + carry;
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*lp = carry;
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carry >>= LITTLENUM_NUMBER_OF_BITS;
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}
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}
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} else if ((*lp & mask[prec_bits]) != mask[prec_bits])
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lp++;
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}
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return return_value;
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} else if (exponent_4 & ~ mask [exponent_bits]) {
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/*
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* Exponent overflow. Lose immediately.
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*/
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/*
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* We leave return_value alone: admit we read the
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* number, but return a floating exception
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* because we can't encode the number.
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*/
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make_invalid_floating_point_number (words);
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return return_value;
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} else {
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word1 |= (exponent_4 << ((LITTLENUM_NUMBER_OF_BITS - 1) - exponent_bits))
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| next_bits ((LITTLENUM_NUMBER_OF_BITS - 1) - exponent_bits);
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}
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*lp++ = word1;
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/* X_PRECISION is special: it has 16 bits of zero in the middle,
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followed by a 1 bit. */
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if (exponent_bits == 15 && precision == X_PRECISION) {
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*lp++ = 0;
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*lp++ = 1 << (LITTLENUM_NUMBER_OF_BITS) | next_bits(LITTLENUM_NUMBER_OF_BITS - 1);
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}
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/* The rest of the words are just mantissa bits. */
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while(lp < words + precision)
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*lp++ = next_bits(LITTLENUM_NUMBER_OF_BITS);
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if (next_bits(1)) {
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unsigned long carry;
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/*
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* Since the NEXT bit is a 1, round UP the mantissa.
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* The cunning design of these hidden-1 floats permits
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* us to let the mantissa overflow into the exponent, and
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* it 'does the right thing'. However, we lose if the
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* highest-order bit of the lowest-order word flips.
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* Is that clear?
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*/
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/* #if (sizeof(carry)) < ((sizeof(bits[0]) * BITS_PER_CHAR) + 2)
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Please allow at least 1 more bit in carry than is in a LITTLENUM.
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We need that extra bit to hold a carry during a LITTLENUM carry
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propagation. Another extra bit (kept 0) will assure us that we
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don't get a sticky sign bit after shifting right, and that
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permits us to propagate the carry without any masking of bits.
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#endif */
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for (carry = 1, lp--; carry && (lp >= words); lp--) {
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carry = *lp + carry;
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*lp = carry;
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carry >>= LITTLENUM_NUMBER_OF_BITS;
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}
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if ((word1 ^ *words) & (1 << (LITTLENUM_NUMBER_OF_BITS - 1))) {
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/* We leave return_value alone: admit we read the
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* number, but return a floating exception
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* because we can't encode the number.
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*/
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*words &= ~(1 << (LITTLENUM_NUMBER_OF_BITS - 1));
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/* make_invalid_floating_point_number (words); */
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/* return return_value; */
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}
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}
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return (return_value);
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}
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/* This routine is a real kludge. Someone really should do it better, but
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I'm too lazy, and I don't understand this stuff all too well anyway
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(JF)
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*/
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void
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int_to_gen(x)
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long x;
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{
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char buf[20];
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char *bufp;
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sprintf(buf,"%ld",x);
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bufp = &buf[0];
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||
if (atof_generic(&bufp, ".", EXP_CHARS, &generic_floating_point_number))
|
||
as_bad("Error converting number to floating point (Exponent overflow?)");
|
||
}
|
||
|
||
#ifdef TEST
|
||
char *
|
||
print_gen(gen)
|
||
FLONUM_TYPE *gen;
|
||
{
|
||
FLONUM_TYPE f;
|
||
LITTLENUM_TYPE arr[10];
|
||
double dv;
|
||
float fv;
|
||
static char sbuf[40];
|
||
|
||
if (gen) {
|
||
f = generic_floating_point_number;
|
||
generic_floating_point_number = *gen;
|
||
}
|
||
gen_to_words(&arr[0], 4, 11);
|
||
bcopy(&arr[0], &dv, sizeof(double));
|
||
sprintf(sbuf, "%x %x %x %x %.14G ", arr[0], arr[1], arr[2], arr[3], dv);
|
||
gen_to_words(&arr[0],2,8);
|
||
bcopy(&arr[0],&fv,sizeof(float));
|
||
sprintf(sbuf + strlen(sbuf), "%x %x %.12g\n", arr[0], arr[1],
|
||
fv);
|
||
|
||
if (gen) {
|
||
generic_floating_point_number = f;
|
||
}
|
||
|
||
return(sbuf);
|
||
}
|
||
#endif
|
||
|
||
/* end of atof-ieee.c */
|