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  1. <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

  2. <html>

  3. <!-- This file documents the GNU Assembler "as".

  4. 

  5. Copyright (C) 1991-2020 Free Software Foundation, Inc.

  6. 

  7. Permission is granted to copy, distribute and/or modify this document

  8. under the terms of the GNU Free Documentation License, Version 1.3

  9. or any later version published by the Free Software Foundation;

  10. with no Invariant Sections, with no Front-Cover Texts, and with no

  11. Back-Cover Texts.  A copy of the license is included in the

  12. section entitled "GNU Free Documentation License".

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  15. <head>

  16. <meta http-equiv="Content-Type" content="text/html; charset=utf-8">

  17. <title>MMIX-Opts (Using as)</title>

  18. 

  19. <meta name="description" content="MMIX-Opts (Using as)">

  20. <meta name="keywords" content="MMIX-Opts (Using as)">

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  24. <link href="index.html#Top" rel="start" title="Top">

  25. <link href="AS-Index.html#AS-Index" rel="index" title="AS Index">

  26. <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">

  27. <link href="MMIX_002dDependent.html#MMIX_002dDependent" rel="up" title="MMIX-Dependent">

  28. <link href="MMIX_002dExpand.html#MMIX_002dExpand" rel="next" title="MMIX-Expand">

  29. <link href="MMIX_002dDependent.html#MMIX_002dDependent" rel="prev" title="MMIX-Dependent">

  30. <style type="text/css">

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  56. </style>

  57. 

  58. 

  59. </head>

  60. 

  61. <body lang="en">

  62. <a name="MMIX_002dOpts"></a>

  63. <div class="header">

  64. <p>

  65. 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> &nbsp; [<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>

  66. </div>

  67. <hr>

  68. <a name="Command_002dline-Options-1"></a>

  69. <h4 class="subsection">9.28.1 Command-line Options</h4>

  70. 

  71. <a name="index-options_002c-MMIX"></a>

  72. <a name="index-MMIX-options"></a>

  73. <p>The MMIX version of <code>as</code> has some machine-dependent options.

  74. </p>

  75. <a name="index-_002d_002dfixed_002dspecial_002dregister_002dnames-command_002dline-option_002c-MMIX"></a>

  76. <p>When &lsquo;<samp>--fixed-special-register-names</samp>&rsquo; is specified, only the register

  77. names specified in <a href="MMIX_002dRegs.html#MMIX_002dRegs">MMIX-Regs</a> are recognized in the instructions

  78. <code>PUT</code> and <code>GET</code>.

  79. </p>

  80. <a name="index-_002d_002dglobalize_002dsymbols-command_002dline-option_002c-MMIX"></a>

  81. <p>You can use the &lsquo;<samp>--globalize-symbols</samp>&rsquo; to make all symbols global.

  82. This option is useful when splitting up a <code>mmixal</code> program into

  83. several files.

  84. </p>

  85. <a name="index-_002d_002dgnu_002dsyntax-command_002dline-option_002c-MMIX"></a>

  86. <p>The &lsquo;<samp>--gnu-syntax</samp>&rsquo; turns off most syntax compatibility with

  87. <code>mmixal</code>.  Its usability is currently doubtful.

  88. </p>

  89. <a name="index-_002d_002drelax-command_002dline-option_002c-MMIX"></a>

  90. <p>The &lsquo;<samp>--relax</samp>&rsquo; option is not fully supported, but will eventually make

  91. the object file prepared for linker relaxation.

  92. </p>

  93. <a name="index-_002d_002dno_002dpredefined_002dsyms-command_002dline-option_002c-MMIX"></a>

  94. <p>If you want to avoid inadvertently calling a predefined symbol and would

  95. rather get an error, for example when using <code>as</code> with a

  96. compiler or other machine-generated code, specify

  97. &lsquo;<samp>--no-predefined-syms</samp>&rsquo;.  This turns off built-in predefined

  98. definitions of all such symbols, including rounding-mode symbols, segment

  99. symbols, &lsquo;<samp>BIT</samp>&rsquo; symbols, and <code>TRAP</code> symbols used in <code>mmix</code>

  100. &ldquo;system calls&rdquo;.  It also turns off predefined special-register names,

  101. except when used in <code>PUT</code> and <code>GET</code> instructions.

  102. </p>

  103. <a name="index-_002d_002dno_002dexpand-command_002dline-option_002c-MMIX"></a>

  104. <p>By default, some instructions are expanded to fit the size of the operand

  105. or an external symbol (see <a href="MMIX_002dExpand.html#MMIX_002dExpand">MMIX-Expand</a>).  By passing

  106. &lsquo;<samp>--no-expand</samp>&rsquo;, no such expansion will be done, instead causing errors

  107. at link time if the operand does not fit.

  108. </p>

  109. <a name="index-_002d_002dno_002dmerge_002dgregs-command_002dline-option_002c-MMIX"></a>

  110. <p>The <code>mmixal</code> documentation (see <a href="MMIX_002dSyntax.html#mmixsite">mmixsite</a>) specifies that global

  111. registers allocated with the &lsquo;<samp>GREG</samp>&rsquo; directive (see <a href="MMIX_002dPseudos.html#MMIX_002dgreg">MMIX-greg</a>) and

  112. initialized to the same non-zero value, will refer to the same global

  113. register.  This isn&rsquo;t strictly enforceable in <code>as</code> since the

  114. final addresses aren&rsquo;t known until link-time, but it will do an effort

  115. unless the &lsquo;<samp>--no-merge-gregs</samp>&rsquo; option is specified.  (Register merging

  116. isn&rsquo;t yet implemented in <code>ld</code>.)

  117. </p>

  118. <a name="index-_002dx-command_002dline-option_002c-MMIX"></a>

  119. <p><code>as</code> will warn every time it expands an instruction to fit an

  120. operand unless the option &lsquo;<samp>-x</samp>&rsquo; is specified.  It is believed that

  121. this behaviour is more useful than just mimicking <code>mmixal</code>&rsquo;s

  122. behaviour, in which instructions are only expanded if the &lsquo;<samp>-x</samp>&rsquo; option

  123. is specified, and assembly fails otherwise, when an instruction needs to

  124. be expanded.  It needs to be kept in mind that <code>mmixal</code> is both an

  125. assembler and linker, while <code>as</code> will expand instructions

  126. that at link stage can be contracted.  (Though linker relaxation isn&rsquo;t yet

  127. implemented in <code>ld</code>.)  The option &lsquo;<samp>-x</samp>&rsquo; also implies

  128. &lsquo;<samp>--linker-allocated-gregs</samp>&rsquo;.

  129. </p>

  130. <a name="index-_002d_002dno_002dpushj_002dstubs-command_002dline-option_002c-MMIX"></a>

  131. <a name="index-_002d_002dno_002dstubs-command_002dline-option_002c-MMIX"></a>

  132. <p>If instruction expansion is enabled, <code>as</code> can expand a

  133. &lsquo;<samp>PUSHJ</samp>&rsquo; instruction into a series of instructions.  The shortest

  134. expansion is to not expand it, but just mark the call as redirectable to a

  135. stub, which <code>ld</code> creates at link-time, but only if the

  136. original &lsquo;<samp>PUSHJ</samp>&rsquo; instruction is found not to reach the target.  The

  137. stub consists of the necessary instructions to form a jump to the target.

  138. This happens if <code>as</code> can assert that the &lsquo;<samp>PUSHJ</samp>&rsquo;

  139. instruction can reach such a stub.  The option &lsquo;<samp>--no-pushj-stubs</samp>&rsquo;

  140. disables this shorter expansion, and the longer series of instructions is

  141. then created at assembly-time.  The option &lsquo;<samp>--no-stubs</samp>&rsquo; is a synonym,

  142. intended for compatibility with future releases, where generation of stubs

  143. for other instructions may be implemented.

  144. </p>

  145. <a name="index-_002d_002dlinker_002dallocated_002dgregs-command_002dline-option_002c-MMIX"></a>

  146. <p>Usually a two-operand-expression (see <a href="MMIX_002dPseudos.html#GREG_002dbase">GREG-base</a>) without a matching

  147. &lsquo;<samp>GREG</samp>&rsquo; directive is treated as an error by <code>as</code>.  When

  148. the option &lsquo;<samp>--linker-allocated-gregs</samp>&rsquo; is in effect, they are instead

  149. passed through to the linker, which will allocate as many global registers

  150. as is needed.

  151. </p>

  152. <hr>

  153. <div class="header">

  154. <p>

  155. 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> &nbsp; [<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>

  156. </div>

  157. 

  158. 

  159. 

  160. </body>

  161. </html>