Copyright (C) 1993, 1994, 1995, 1996, 1997, 1998, 1999,
2000, 2002, 2003 Free Software Foundation, Inc.
Contributed by Stephen L. Moshier (moshier@world.std.com).
- Re-written by Richard Henderson <rth@redhat.com>
+ Re-written by Richard Henderson <rth@redhat.com>
This file is part of GCC.
#include "tm_p.h"
/* The floating point model used internally is not exactly IEEE 754
- compliant, and close to the description in the ISO C standard,
+ compliant, and close to the description in the ISO C99 standard,
section 5.2.4.2.2 Characteristics of floating types.
Specifically
significand is fractional. Normalized significands are in the
range [0.5, 1.0).
- A requirement of the model is that P be larger than than the
- largest supported target floating-point type by at least 2 bits.
- This gives us proper rounding when we truncate to the target type.
- In addition, E must be large enough to hold the smallest supported
- denormal number in a normalized form.
+ A requirement of the model is that P be larger than the largest
+ supported target floating-point type by at least 2 bits. This gives
+ us proper rounding when we truncate to the target type. In addition,
+ E must be large enough to hold the smallest supported denormal number
+ in a normalized form.
Both of these requirements are easily satisfied. The largest target
significand is 113 bits; we store at least 160. The smallest
denormal number fits in 17 exponent bits; we store 29.
Note that the decimal string conversion routines are sensitive to
- rounding error. Since the raw arithmetic routines do not themselves
+ rounding errors. Since the raw arithmetic routines do not themselves
have guard digits or rounding, the computation of 10**exp can
accumulate more than a few digits of error. The previous incarnation
- of real.c successfully used a 144 bit fraction; given the current
+ of real.c successfully used a 144-bit fraction; given the current
layout of REAL_VALUE_TYPE we're forced to expand to at least 160 bits.
Target floating point models that use base 16 instead of base 2