You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
140 lines
6.0 KiB
HTML
140 lines
6.0 KiB
HTML
<html lang="en">
|
|
<head>
|
|
<title>Floating point implementation - Using the GNU Compiler Collection (GCC)</title>
|
|
<meta http-equiv="Content-Type" content="text/html">
|
|
<meta name="description" content="Using the GNU Compiler Collection (GCC)">
|
|
<meta name="generator" content="makeinfo 4.13">
|
|
<link title="Top" rel="start" href="index.html#Top">
|
|
<link rel="up" href="C-Implementation.html#C-Implementation" title="C Implementation">
|
|
<link rel="prev" href="Integers-implementation.html#Integers-implementation" title="Integers implementation">
|
|
<link rel="next" href="Arrays-and-pointers-implementation.html#Arrays-and-pointers-implementation" title="Arrays and pointers implementation">
|
|
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
|
|
<!--
|
|
Copyright (C) 1988-2015 Free Software Foundation, Inc.
|
|
|
|
Permission is granted to copy, distribute and/or modify this document
|
|
under the terms of the GNU Free Documentation License, Version 1.3 or
|
|
any later version published by the Free Software Foundation; with the
|
|
Invariant Sections being ``Funding Free Software'', the Front-Cover
|
|
Texts being (a) (see below), and with the Back-Cover Texts being (b)
|
|
(see below). A copy of the license is included in the section entitled
|
|
``GNU Free Documentation License''.
|
|
|
|
(a) The FSF's Front-Cover Text is:
|
|
|
|
A GNU Manual
|
|
|
|
(b) The FSF's Back-Cover Text is:
|
|
|
|
You have freedom to copy and modify this GNU Manual, like GNU
|
|
software. Copies published by the Free Software Foundation raise
|
|
funds for GNU development.-->
|
|
<meta http-equiv="Content-Style-Type" content="text/css">
|
|
<style type="text/css"><!--
|
|
pre.display { font-family:inherit }
|
|
pre.format { font-family:inherit }
|
|
pre.smalldisplay { font-family:inherit; font-size:smaller }
|
|
pre.smallformat { font-family:inherit; font-size:smaller }
|
|
pre.smallexample { font-size:smaller }
|
|
pre.smalllisp { font-size:smaller }
|
|
span.sc { font-variant:small-caps }
|
|
span.roman { font-family:serif; font-weight:normal; }
|
|
span.sansserif { font-family:sans-serif; font-weight:normal; }
|
|
--></style>
|
|
</head>
|
|
<body>
|
|
<div class="node">
|
|
<a name="Floating-point-implementation"></a>
|
|
<p>
|
|
Next: <a rel="next" accesskey="n" href="Arrays-and-pointers-implementation.html#Arrays-and-pointers-implementation">Arrays and pointers implementation</a>,
|
|
Previous: <a rel="previous" accesskey="p" href="Integers-implementation.html#Integers-implementation">Integers implementation</a>,
|
|
Up: <a rel="up" accesskey="u" href="C-Implementation.html#C-Implementation">C Implementation</a>
|
|
<hr>
|
|
</div>
|
|
|
|
<h3 class="section">4.6 Floating Point</h3>
|
|
|
|
<ul>
|
|
<li><cite>The accuracy of the floating-point operations and of the library
|
|
functions in </cite><code><math.h></code><cite> and </cite><code><complex.h></code><cite> that return floating-point
|
|
results (C90, C99 and C11 5.2.4.2.2).</cite>
|
|
|
|
<p>The accuracy is unknown.
|
|
|
|
<li><cite>The rounding behaviors characterized by non-standard values
|
|
of </cite><code>FLT_ROUNDS</code><cite>
|
|
(C90, C99 and C11 5.2.4.2.2).</cite>
|
|
|
|
<p>GCC does not use such values.
|
|
|
|
<li><cite>The evaluation methods characterized by non-standard negative
|
|
values of </cite><code>FLT_EVAL_METHOD</code><cite> (C99 and C11 5.2.4.2.2).</cite>
|
|
|
|
<p>GCC does not use such values.
|
|
|
|
<li><cite>The direction of rounding when an integer is converted to a
|
|
floating-point number that cannot exactly represent the original
|
|
value (C90 6.2.1.3, C99 and C11 6.3.1.4).</cite>
|
|
|
|
<p>C99 Annex F is followed.
|
|
|
|
<li><cite>The direction of rounding when a floating-point number is
|
|
converted to a narrower floating-point number (C90 6.2.1.4, C99 and C11
|
|
6.3.1.5).</cite>
|
|
|
|
<p>C99 Annex F is followed.
|
|
|
|
<li><cite>How the nearest representable value or the larger or smaller
|
|
representable value immediately adjacent to the nearest representable
|
|
value is chosen for certain floating constants (C90 6.1.3.1, C99 and C11
|
|
6.4.4.2).</cite>
|
|
|
|
<p>C99 Annex F is followed.
|
|
|
|
<li><cite>Whether and how floating expressions are contracted when not
|
|
disallowed by the </cite><code>FP_CONTRACT</code><cite> pragma (C99 and C11 6.5).</cite>
|
|
|
|
<p>Expressions are currently only contracted if <samp><span class="option">-ffp-contract=fast</span></samp>,
|
|
<samp><span class="option">-funsafe-math-optimizations</span></samp> or <samp><span class="option">-ffast-math</span></samp> are used.
|
|
This is subject to change.
|
|
|
|
<li><cite>The default state for the </cite><code>FENV_ACCESS</code><cite> pragma (C99 and C11
|
|
7.6.1).</cite>
|
|
|
|
<p>This pragma is not implemented, but the default is to “off” unless
|
|
<samp><span class="option">-frounding-math</span></samp> is used in which case it is “on”.
|
|
|
|
<li><cite>Additional floating-point exceptions, rounding modes, environments,
|
|
and classifications, and their macro names (C99 and C11 7.6, C99 and
|
|
C11 7.12).</cite>
|
|
|
|
<p>This is dependent on the implementation of the C library, and is not
|
|
defined by GCC itself.
|
|
|
|
<li><cite>The default state for the </cite><code>FP_CONTRACT</code><cite> pragma (C99 and C11
|
|
7.12.2).</cite>
|
|
|
|
<p>This pragma is not implemented. Expressions are currently only
|
|
contracted if <samp><span class="option">-ffp-contract=fast</span></samp>,
|
|
<samp><span class="option">-funsafe-math-optimizations</span></samp> or <samp><span class="option">-ffast-math</span></samp> are used.
|
|
This is subject to change.
|
|
|
|
<li><cite>Whether the “inexact” floating-point exception can be raised
|
|
when the rounded result actually does equal the mathematical result
|
|
in an IEC 60559 conformant implementation (C99 F.9).</cite>
|
|
|
|
<p>This is dependent on the implementation of the C library, and is not
|
|
defined by GCC itself.
|
|
|
|
<li><cite>Whether the “underflow” (and “inexact”) floating-point
|
|
exception can be raised when a result is tiny but not inexact in an
|
|
IEC 60559 conformant implementation (C99 F.9).</cite>
|
|
|
|
<p>This is dependent on the implementation of the C library, and is not
|
|
defined by GCC itself.
|
|
|
|
</ul>
|
|
|
|
</body></html>
|
|
|