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| <title>Using as: MMIX-Opts</title> |
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| <a name="MMIX_002dOpts"></a> |
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| Next: <a href="MMIX_002dExpand.html#MMIX_002dExpand" accesskey="n" rel="next">MMIX-Expand</a>, Up: <a href="MMIX_002dDependent.html#MMIX_002dDependent" accesskey="u" rel="up">MMIX-Dependent</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p> |
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| <a name="Command_002dline-Options-1"></a> |
| <h4 class="subsection">9.28.1 Command-line Options</h4> |
| |
| <a name="index-options_002c-MMIX"></a> |
| <a name="index-MMIX-options"></a> |
| <p>The MMIX version of <code>as</code> has some machine-dependent options. |
| </p> |
| <a name="index-_002d_002dfixed_002dspecial_002dregister_002dnames-command-line-option_002c-MMIX"></a> |
| <p>When ‘<samp>--fixed-special-register-names</samp>’ is specified, only the register |
| names specified in <a href="MMIX_002dRegs.html#MMIX_002dRegs">MMIX-Regs</a> are recognized in the instructions |
| <code>PUT</code> and <code>GET</code>. |
| </p> |
| <a name="index-_002d_002dglobalize_002dsymbols-command-line-option_002c-MMIX"></a> |
| <p>You can use the ‘<samp>--globalize-symbols</samp>’ to make all symbols global. |
| This option is useful when splitting up a <code>mmixal</code> program into |
| several files. |
| </p> |
| <a name="index-_002d_002dgnu_002dsyntax-command-line-option_002c-MMIX"></a> |
| <p>The ‘<samp>--gnu-syntax</samp>’ turns off most syntax compatibility with |
| <code>mmixal</code>. Its usability is currently doubtful. |
| </p> |
| <a name="index-_002d_002drelax-command-line-option_002c-MMIX"></a> |
| <p>The ‘<samp>--relax</samp>’ option is not fully supported, but will eventually make |
| the object file prepared for linker relaxation. |
| </p> |
| <a name="index-_002d_002dno_002dpredefined_002dsyms-command-line-option_002c-MMIX"></a> |
| <p>If you want to avoid inadvertently calling a predefined symbol and would |
| rather get an error, for example when using <code>as</code> with a |
| compiler or other machine-generated code, specify |
| ‘<samp>--no-predefined-syms</samp>’. This turns off built-in predefined |
| definitions of all such symbols, including rounding-mode symbols, segment |
| symbols, ‘<samp>BIT</samp>’ symbols, and <code>TRAP</code> symbols used in <code>mmix</code> |
| “system calls”. It also turns off predefined special-register names, |
| except when used in <code>PUT</code> and <code>GET</code> instructions. |
| </p> |
| <a name="index-_002d_002dno_002dexpand-command-line-option_002c-MMIX"></a> |
| <p>By default, some instructions are expanded to fit the size of the operand |
| or an external symbol (see <a href="MMIX_002dExpand.html#MMIX_002dExpand">MMIX-Expand</a>). By passing |
| ‘<samp>--no-expand</samp>’, no such expansion will be done, instead causing errors |
| at link time if the operand does not fit. |
| </p> |
| <a name="index-_002d_002dno_002dmerge_002dgregs-command-line-option_002c-MMIX"></a> |
| <p>The <code>mmixal</code> documentation (see <a href="MMIX_002dSyntax.html#mmixsite">mmixsite</a>) specifies that global |
| registers allocated with the ‘<samp>GREG</samp>’ directive (see <a href="MMIX_002dPseudos.html#MMIX_002dgreg">MMIX-greg</a>) and |
| initialized to the same non-zero value, will refer to the same global |
| register. This isn’t strictly enforceable in <code>as</code> since the |
| final addresses aren’t known until link-time, but it will do an effort |
| unless the ‘<samp>--no-merge-gregs</samp>’ option is specified. (Register merging |
| isn’t yet implemented in <code>ld</code>.) |
| </p> |
| <a name="index-_002dx-command-line-option_002c-MMIX"></a> |
| <p><code>as</code> will warn every time it expands an instruction to fit an |
| operand unless the option ‘<samp>-x</samp>’ is specified. It is believed that |
| this behaviour is more useful than just mimicking <code>mmixal</code>’s |
| behaviour, in which instructions are only expanded if the ‘<samp>-x</samp>’ option |
| is specified, and assembly fails otherwise, when an instruction needs to |
| be expanded. It needs to be kept in mind that <code>mmixal</code> is both an |
| assembler and linker, while <code>as</code> will expand instructions |
| that at link stage can be contracted. (Though linker relaxation isn’t yet |
| implemented in <code>ld</code>.) The option ‘<samp>-x</samp>’ also imples |
| ‘<samp>--linker-allocated-gregs</samp>’. |
| </p> |
| <a name="index-_002d_002dno_002dpushj_002dstubs-command-line-option_002c-MMIX"></a> |
| <a name="index-_002d_002dno_002dstubs-command-line-option_002c-MMIX"></a> |
| <p>If instruction expansion is enabled, <code>as</code> can expand a |
| ‘<samp>PUSHJ</samp>’ instruction into a series of instructions. The shortest |
| expansion is to not expand it, but just mark the call as redirectable to a |
| stub, which <code>ld</code> creates at link-time, but only if the |
| original ‘<samp>PUSHJ</samp>’ instruction is found not to reach the target. The |
| stub consists of the necessary instructions to form a jump to the target. |
| This happens if <code>as</code> can assert that the ‘<samp>PUSHJ</samp>’ |
| instruction can reach such a stub. The option ‘<samp>--no-pushj-stubs</samp>’ |
| disables this shorter expansion, and the longer series of instructions is |
| then created at assembly-time. The option ‘<samp>--no-stubs</samp>’ is a synonym, |
| intended for compatibility with future releases, where generation of stubs |
| for other instructions may be implemented. |
| </p> |
| <a name="index-_002d_002dlinker_002dallocated_002dgregs-command-line-option_002c-MMIX"></a> |
| <p>Usually a two-operand-expression (see <a href="MMIX_002dPseudos.html#GREG_002dbase">GREG-base</a>) without a matching |
| ‘<samp>GREG</samp>’ directive is treated as an error by <code>as</code>. When |
| the option ‘<samp>--linker-allocated-gregs</samp>’ is in effect, they are instead |
| passed through to the linker, which will allocate as many global registers |
| as is needed. |
| </p> |
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| <div class="header"> |
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| Next: <a href="MMIX_002dExpand.html#MMIX_002dExpand" accesskey="n" rel="next">MMIX-Expand</a>, Up: <a href="MMIX_002dDependent.html#MMIX_002dDependent" accesskey="u" rel="up">MMIX-Dependent</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p> |
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