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84 lines
4.2 KiB
HTML
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<title>MIPS ISA - Using as</title>
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<link rel="up" href="MIPS_002dDependent.html#MIPS_002dDependent" title="MIPS-Dependent">
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<!--
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This file documents the GNU Assembler "as".
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Copyright (C) 1991-2015 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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or any later version published by the Free Software Foundation;
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<a name="MIPS-ISA"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="MIPS-assembly-options.html#MIPS-assembly-options">MIPS assembly options</a>,
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Previous: <a rel="previous" accesskey="p" href="MIPS-Small-Data.html#MIPS-Small-Data">MIPS Small Data</a>,
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Up: <a rel="up" accesskey="u" href="MIPS_002dDependent.html#MIPS_002dDependent">MIPS-Dependent</a>
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<h4 class="subsection">9.27.5 Directives to override the ISA level</h4>
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<p><a name="index-MIPS-ISA-override-1496"></a><a name="index-g_t_0040code_007b_002eset-mips_0040var_007bn_007d_007d-1497"></a><span class="sc">gnu</span> <code>as</code> supports an additional directive to change
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the MIPS Instruction Set Architecture level on the fly: <code>.set
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mips</code><var>n</var>. <var>n</var> should be a number from 0 to 5, or 32, 32r2, 32r3,
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32r5, 32r6, 64, 64r2, 64r3, 64r5 or 64r6.
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The values other than 0 make the assembler accept instructions
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for the corresponding ISA level, from that point on in the
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assembly. <code>.set mips</code><var>n</var> affects not only which instructions
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are permitted, but also how certain macros are expanded. <code>.set
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mips0</code> restores the ISA level to its original level: either the
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level you selected with command line options, or the default for your
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configuration. You can use this feature to permit specific MIPS III
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instructions while assembling in 32 bit mode. Use this directive with
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care!
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<p><a name="index-MIPS-CPU-override-1498"></a><a name="index-g_t_0040code_007b_002eset-arch_003d_0040var_007bcpu_007d_007d-1499"></a>The <code>.set arch=</code><var>cpu</var> directive provides even finer control.
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It changes the effective CPU target and allows the assembler to use
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instructions specific to a particular CPU. All CPUs supported by the
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‘<samp><span class="samp">-march</span></samp>’ command line option are also selectable by this directive.
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The original value is restored by <code>.set arch=default</code>.
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<p>The directive <code>.set mips16</code> puts the assembler into MIPS 16 mode,
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in which it will assemble instructions for the MIPS 16 processor. Use
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<code>.set nomips16</code> to return to normal 32 bit mode.
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<p>Traditional MIPS assemblers do not support this directive.
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<p>The directive <code>.set micromips</code> puts the assembler into microMIPS mode,
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in which it will assemble instructions for the microMIPS processor. Use
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<code>.set nomicromips</code> to return to normal 32 bit mode.
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<p>Traditional MIPS assemblers do not support this directive.
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