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<h3 class="section">6.40 Constraints for <code>asm</code> Operands</h3>

<p><a name="index-operand-constraints_002c-_0040code_007basm_007d-2531"></a><a name="index-constraints_002c-_0040code_007basm_007d-2532"></a><a name="index-g_t_0040code_007basm_007d-constraints-2533"></a>
Here are specific details on what constraint letters you can use with
<code>asm</code> operands. 
Constraints can say whether
an operand may be in a register, and which kinds of register; whether the
operand can be a memory reference, and which kinds of address; whether the
operand may be an immediate constant, and which possible values it may
have.  Constraints can also require two operands to match.

<ul class="menu">
<li><a accesskey="1" href="Simple-Constraints.html#Simple-Constraints">Simple Constraints</a>:   Basic use of constraints. 
<li><a accesskey="2" href="Multi_002dAlternative.html#Multi_002dAlternative">Multi-Alternative</a>:    When an insn has two alternative constraint-patterns. 
<li><a accesskey="3" href="Modifiers.html#Modifiers">Modifiers</a>:            More precise control over effects of constraints. 
<li><a accesskey="4" href="Machine-Constraints.html#Machine-Constraints">Machine Constraints</a>:  Special constraints for some particular machines. 
</ul>

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