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| <h4 class="subsection">9.27.5 Directives to override the ISA level</h4> |
| |
| <p><a name="index-MIPS-ISA-override-1580"></a><a name="index-g_t_0040code_007b_002eset-mips_0040var_007bn_007d_007d-1581"></a><span class="sc">gnu</span> <code>as</code> supports an additional directive to change |
| the MIPS Instruction Set Architecture level on the fly: <code>.set |
| mips</code><var>n</var>. <var>n</var> should be a number from 0 to 5, or 32, 32r2, 32r3, |
| 32r5, 32r6, 64, 64r2, 64r3, 64r5 or 64r6. |
| The values other than 0 make the assembler accept instructions |
| for the corresponding ISA level, from that point on in the |
| assembly. <code>.set mips</code><var>n</var> affects not only which instructions |
| are permitted, but also how certain macros are expanded. <code>.set |
| mips0</code> restores the ISA level to its original level: either the |
| level you selected with command-line options, or the default for your |
| configuration. You can use this feature to permit specific MIPS III |
| instructions while assembling in 32 bit mode. Use this directive with |
| care! |
| |
| <p><a name="index-MIPS-CPU-override-1582"></a><a name="index-g_t_0040code_007b_002eset-arch_003d_0040var_007bcpu_007d_007d-1583"></a>The <code>.set arch=</code><var>cpu</var> directive provides even finer control. |
| It changes the effective CPU target and allows the assembler to use |
| instructions specific to a particular CPU. All CPUs supported by the |
| ‘<samp><span class="samp">-march</span></samp>’ command-line option are also selectable by this directive. |
| The original value is restored by <code>.set arch=default</code>. |
| |
| <p>The directive <code>.set mips16</code> puts the assembler into MIPS 16 mode, |
| in which it will assemble instructions for the MIPS 16 processor. Use |
| <code>.set nomips16</code> to return to normal 32 bit mode. |
| |
| <p>Traditional MIPS assemblers do not support this directive. |
| |
| <p>The directive <code>.set micromips</code> puts the assembler into microMIPS mode, |
| in which it will assemble instructions for the microMIPS processor. Use |
| <code>.set nomicromips</code> to return to normal 32 bit mode. |
| |
| <p>Traditional MIPS assemblers do not support this directive. |
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