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91 lines
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91 lines
3.9 KiB
HTML
4 years ago
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<title>Mnemonic Attribute - GNU Compiler Collection (GCC) Internals</title>
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<div class="node">
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<a name="Mnemonic-Attribute"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Delay-Slots.html#Delay-Slots">Delay Slots</a>,
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Previous: <a rel="previous" accesskey="p" href="Constant-Attributes.html#Constant-Attributes">Constant Attributes</a>,
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Up: <a rel="up" accesskey="u" href="Insn-Attributes.html#Insn-Attributes">Insn Attributes</a>
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<hr>
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</div>
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<h4 class="subsection">16.19.7 Mnemonic Attribute</h4>
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<p><a name="index-mnemonic-attribute-3777"></a>
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The <code>mnemonic</code> attribute is a string type attribute holding the
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instruction mnemonic for an insn alternative. The attribute values
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will automatically be generated by the machine description parser if
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there is an attribute definition in the md file:
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<pre class="smallexample"> (define_attr "mnemonic" "unknown" (const_string "unknown"))
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</pre>
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<p>The default value can be freely chosen as long as it does not collide
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with any of the instruction mnemonics. This value will be used
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whenever the machine description parser is not able to determine the
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mnemonic string. This might be the case for output templates
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containing more than a single instruction as in
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<code>"mvcle\t%0,%1,0\;jo\t.-4"</code>.
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<p>The <code>mnemonic</code> attribute set is not generated automatically if the
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instruction string is generated via C code.
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<p>An existing <code>mnemonic</code> attribute set in an insn definition will not
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be overriden by the md file parser. That way it is possible to
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manually set the instruction mnemonics for the cases where the md file
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parser fails to determine it automatically.
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<p>The <code>mnemonic</code> attribute is useful for dealing with instruction
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specific properties in the pipeline description without defining
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additional insn attributes.
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<pre class="smallexample"> (define_attr "ooo_expanded" ""
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(cond [(eq_attr "mnemonic" "dlr,dsgr,d,dsgf,stam,dsgfr,dlgr")
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(const_int 1)]
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(const_int 0)))
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</pre>
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</body></html>
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