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104 lines
4.8 KiB
HTML
104 lines
4.8 KiB
HTML
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<head>
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<title>Explicit Register Variables (Using the GNU Compiler Collection (GCC))</title>
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<meta name="description" content="Explicit Register Variables (Using the GNU Compiler Collection (GCC))">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Using-Assembly-Language-with-C.html#Using-Assembly-Language-with-C" rel="up" title="Using Assembly Language with C">
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<link href="Global-Register-Variables.html#Global-Register-Variables" rel="next" title="Global Register Variables">
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<a name="Explicit-Register-Variables"></a>
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<p>
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Next: <a href="Size-of-an-asm.html#Size-of-an-asm" accesskey="n" rel="next">Size of an asm</a>, Previous: <a href="Asm-Labels.html#Asm-Labels" accesskey="p" rel="prev">Asm Labels</a>, Up: <a href="Using-Assembly-Language-with-C.html#Using-Assembly-Language-with-C" accesskey="u" rel="up">Using Assembly Language with C</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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</div>
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<hr>
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<a name="Variables-in-Specified-Registers"></a>
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<h4 class="subsection">6.45.5 Variables in Specified Registers</h4>
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<a name="Explicit-Reg-Vars"></a><a name="index-explicit-register-variables"></a>
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<a name="index-variables-in-specified-registers"></a>
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<a name="index-specified-registers"></a>
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<p>GNU C allows you to associate specific hardware registers with C
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variables. In almost all cases, allowing the compiler to assign
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registers produces the best code. However under certain unusual
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circumstances, more precise control over the variable storage is
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required.
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</p>
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<p>Both global and local variables can be associated with a register. The
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consequences of performing this association are very different between
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the two, as explained in the sections below.
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</p>
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<table class="menu" border="0" cellspacing="0">
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<tr><td align="left" valign="top">• <a href="Global-Register-Variables.html#Global-Register-Variables" accesskey="1">Global Register Variables</a>:</td><td> </td><td align="left" valign="top">Variables declared at global scope.
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</td></tr>
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<tr><td align="left" valign="top">• <a href="Local-Register-Variables.html#Local-Register-Variables" accesskey="2">Local Register Variables</a>:</td><td> </td><td align="left" valign="top">Variables declared within a function.
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</td></tr>
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