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<title>Using the GNU Compiler Collection (GCC): Floating Types</title>
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<a name="Floating-Types"></a>
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<p>
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Next: <a href="Half_002dPrecision.html#Half_002dPrecision" accesskey="n" rel="next">Half-Precision</a>, Previous: <a href="Complex.html#Complex" accesskey="p" rel="prev">Complex</a>, Up: <a href="C-Extensions.html#C-Extensions" accesskey="u" rel="up">C Extensions</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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<a name="Additional-Floating-Types"></a>
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<h3 class="section">6.11 Additional Floating Types</h3>
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<a name="index-additional-floating-types"></a>
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<a name="index-_005f_005ffloat80-data-type"></a>
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<a name="index-_005f_005ffloat128-data-type"></a>
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<a name="index-_005f_005fibm128-data-type"></a>
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<a name="index-w-floating-point-suffix"></a>
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<a name="index-q-floating-point-suffix"></a>
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<a name="index-W-floating-point-suffix"></a>
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<a name="index-Q-floating-point-suffix"></a>
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<p>As an extension, GNU C supports additional floating
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types, <code>__float80</code> and <code>__float128</code> to support 80-bit
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(<code>XFmode</code>) and 128-bit (<code>TFmode</code>) floating types.
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Support for additional types includes the arithmetic operators:
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add, subtract, multiply, divide; unary arithmetic operators;
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relational operators; equality operators; and conversions to and from
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integer and other floating types. Use a suffix ‘<samp>w</samp>’ or ‘<samp>W</samp>’
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in a literal constant of type <code>__float80</code> or type
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<code>__ibm128</code>. Use a suffix ‘<samp>q</samp>’ or ‘<samp>Q</samp>’ for <code>_float128</code>.
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</p>
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<p>On the i386, x86_64, IA-64, and HP-UX targets, you can declare complex
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types using the corresponding internal complex type, <code>XCmode</code> for
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<code>__float80</code> type and <code>TCmode</code> for <code>__float128</code> type:
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</p>
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<div class="smallexample">
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<pre class="smallexample">typedef _Complex float __attribute__((mode(TC))) _Complex128;
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typedef _Complex float __attribute__((mode(XC))) _Complex80;
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</pre></div>
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<p>In order to use <code>__float128</code> and <code>__ibm128</code> on PowerPC Linux
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systems, you must use the <samp>-mfloat128</samp>. It is expected in
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future versions of GCC that <code>__float128</code> will be enabled
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automatically. In addition, there are currently problems in using the
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complex <code>__float128</code> type. When these problems are fixed, you
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would use the following syntax to declare <code>_Complex128</code> to be a
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complex <code>__float128</code> type:
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</p>
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<p>On the PowerPC Linux VSX targets, you can declare complex types using
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the corresponding internal complex type, <code>KCmode</code> for
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<code>__float128</code> type and <code>ICmode</code> for <code>__ibm128</code> type:
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</p>
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<div class="smallexample">
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<pre class="smallexample">typedef _Complex float __attribute__((mode(KC))) _Complex_float128;
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typedef _Complex float __attribute__((mode(IC))) _Complex_ibm128;
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</pre></div>
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<p>Not all targets support additional floating-point types.
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<code>__float80</code> and <code>__float128</code> types are supported on x86 and
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IA-64 targets. The <code>__float128</code> type is supported on hppa HP-UX.
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The <code>__float128</code> type is supported on PowerPC 64-bit Linux
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systems by default if the vector scalar instruction set (VSX) is
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enabled.
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</p>
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<p>On the PowerPC, <code>__ibm128</code> provides access to the IBM extended
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double format, and it is intended to be used by the library functions
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that handle conversions if/when long double is changed to be IEEE
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128-bit floating point.
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</p>
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Next: <a href="Half_002dPrecision.html#Half_002dPrecision" accesskey="n" rel="next">Half-Precision</a>, Previous: <a href="Complex.html#Complex" accesskey="p" rel="prev">Complex</a>, Up: <a href="C-Extensions.html#C-Extensions" accesskey="u" rel="up">C Extensions</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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