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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.

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

  18. 

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

  27. <link href="MMIX_002dSyntax.html#MMIX_002dSyntax" rel="up" title="MMIX-Syntax">

  28. <link href="MMIX_002dmmixal.html#MMIX_002dmmixal" rel="next" title="MMIX-mmixal">

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  57. 

  58. 

  59. </head>

  60. 

  61. <body lang="en">

  62. <a name="MMIX_002dPseudos"></a>

  63. <div class="header">

  64. <p>

  65. Previous: <a href="MMIX_002dRegs.html#MMIX_002dRegs" accesskey="p" rel="prev">MMIX-Regs</a>, Up: <a href="MMIX_002dSyntax.html#MMIX_002dSyntax" accesskey="u" rel="up">MMIX-Syntax</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="Assembler-Directives-3"></a>

  69. <h4 class="subsubsection">9.28.3.4 Assembler Directives</h4>

  70. <a name="index-assembler-directives_002c-MMIX"></a>

  71. <a name="index-pseudo_002dops_002c-MMIX"></a>

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

  73. <a name="index-MMIX-pseudo_002dops"></a>

  74. 

  75. <dl compact="compact">

  76. <dt><code>LOC</code></dt>

  77. <dd><a name="index-assembler-directive-LOC_002c-MMIX"></a>

  78. <a name="index-pseudo_002dop-LOC_002c-MMIX"></a>

  79. <a name="index-MMIX-assembler-directive-LOC"></a>

  80. <a name="index-MMIX-pseudo_002dop-LOC"></a>

  81. 

  82. <a name="MMIX_002dloc"></a><p>The <code>LOC</code> directive sets the current location to the value of the

  83. operand field, which may include changing sections.  If the operand is a

  84. constant, the section is set to either <code>.data</code> if the value is

  85. <code>0x2000000000000000</code> or larger, else it is set to <code>.text</code>.

  86. Within a section, the current location may only be changed to

  87. monotonically higher addresses.  A LOC expression must be a previously

  88. defined symbol or a &ldquo;pure&rdquo; constant.

  89. </p>

  90. <p>An example, which sets the label <var>prev</var> to the current location, and

  91. updates the current location to eight bytes forward:

  92. </p><div class="smallexample">

  93. <pre class="smallexample">prev LOC @+8

  94. </pre></div>

  95. 

  96. <p>When a LOC has a constant as its operand, a symbol

  97. <code>__.MMIX.start..text</code> or <code>__.MMIX.start..data</code> is defined

  98. depending on the address as mentioned above.  Each such symbol is

  99. interpreted as special by the linker, locating the section at that

  100. address.  Note that if multiple files are linked, the first object file

  101. with that section will be mapped to that address (not necessarily the file

  102. with the LOC definition).

  103. </p>

  104. </dd>

  105. <dt><code>LOCAL</code></dt>

  106. <dd><a name="index-assembler-directive-LOCAL_002c-MMIX"></a>

  107. <a name="index-pseudo_002dop-LOCAL_002c-MMIX"></a>

  108. <a name="index-MMIX-assembler-directive-LOCAL"></a>

  109. <a name="index-MMIX-pseudo_002dop-LOCAL"></a>

  110. 

  111. <a name="MMIX_002dlocal"></a><p>Example:

  112. </p><div class="smallexample">

  113. <pre class="smallexample"> LOCAL external_symbol

  114.  LOCAL 42

  115.  .local asymbol

  116. </pre></div>

  117. 

  118. <p>This directive-operation generates a link-time assertion that the operand

  119. does not correspond to a global register.  The operand is an expression

  120. that at link-time resolves to a register symbol or a number.  A number is

  121. treated as the register having that number.  There is one restriction on

  122. the use of this directive: the pseudo-directive must be placed in a

  123. section with contents, code or data.

  124. </p>

  125. </dd>

  126. <dt><code>IS</code></dt>

  127. <dd><a name="index-assembler-directive-IS_002c-MMIX"></a>

  128. <a name="index-pseudo_002dop-IS_002c-MMIX"></a>

  129. <a name="index-MMIX-assembler-directive-IS"></a>

  130. <a name="index-MMIX-pseudo_002dop-IS"></a>

  131. 

  132. <a name="MMIX_002dis"></a><p>The <code>IS</code> directive:

  133. </p><div class="smallexample">

  134. <pre class="smallexample">asymbol IS an_expression

  135. </pre></div>

  136. <p>sets the symbol &lsquo;<samp>asymbol</samp>&rsquo; to &lsquo;<samp>an_expression</samp>&rsquo;.  A symbol may not

  137. be set more than once using this directive.  Local labels may be set using

  138. this directive, for example:

  139. </p><div class="smallexample">

  140. <pre class="smallexample">5H IS @+4

  141. </pre></div>

  142. 

  143. </dd>

  144. <dt><code>GREG</code></dt>

  145. <dd><a name="index-assembler-directive-GREG_002c-MMIX"></a>

  146. <a name="index-pseudo_002dop-GREG_002c-MMIX"></a>

  147. <a name="index-MMIX-assembler-directive-GREG"></a>

  148. <a name="index-MMIX-pseudo_002dop-GREG"></a>

  149. 

  150. <a name="MMIX_002dgreg"></a><p>This directive reserves a global register, gives it an initial value and

  151. optionally gives it a symbolic name.  Some examples:

  152. </p>

  153. <div class="smallexample">

  154. <pre class="smallexample">areg GREG

  155. breg GREG data_value

  156.      GREG data_buffer

  157.      .greg creg, another_data_value

  158. </pre></div>

  159. 

  160. <p>The symbolic register name can be used in place of a (non-special)

  161. register.  If a value isn&rsquo;t provided, it defaults to zero.  Unless the

  162. option &lsquo;<samp>--no-merge-gregs</samp>&rsquo; is specified, non-zero registers allocated

  163. with this directive may be eliminated by <code>as</code>; another

  164. register with the same value used in its place.

  165. Any of the instructions

  166. &lsquo;<samp>CSWAP</samp>&rsquo;,

  167. &lsquo;<samp>GO</samp>&rsquo;,

  168. &lsquo;<samp>LDA</samp>&rsquo;,

  169. &lsquo;<samp>LDBU</samp>&rsquo;,

  170. &lsquo;<samp>LDB</samp>&rsquo;,

  171. &lsquo;<samp>LDHT</samp>&rsquo;,

  172. &lsquo;<samp>LDOU</samp>&rsquo;,

  173. &lsquo;<samp>LDO</samp>&rsquo;,

  174. &lsquo;<samp>LDSF</samp>&rsquo;,

  175. &lsquo;<samp>LDTU</samp>&rsquo;,

  176. &lsquo;<samp>LDT</samp>&rsquo;,

  177. &lsquo;<samp>LDUNC</samp>&rsquo;,

  178. &lsquo;<samp>LDVTS</samp>&rsquo;,

  179. &lsquo;<samp>LDWU</samp>&rsquo;,

  180. &lsquo;<samp>LDW</samp>&rsquo;,

  181. &lsquo;<samp>PREGO</samp>&rsquo;,

  182. &lsquo;<samp>PRELD</samp>&rsquo;,

  183. &lsquo;<samp>PREST</samp>&rsquo;,

  184. &lsquo;<samp>PUSHGO</samp>&rsquo;,

  185. &lsquo;<samp>STBU</samp>&rsquo;,

  186. &lsquo;<samp>STB</samp>&rsquo;,

  187. &lsquo;<samp>STCO</samp>&rsquo;,

  188. &lsquo;<samp>STHT</samp>&rsquo;,

  189. &lsquo;<samp>STOU</samp>&rsquo;,

  190. &lsquo;<samp>STSF</samp>&rsquo;,

  191. &lsquo;<samp>STTU</samp>&rsquo;,

  192. &lsquo;<samp>STT</samp>&rsquo;,

  193. &lsquo;<samp>STUNC</samp>&rsquo;,

  194. &lsquo;<samp>SYNCD</samp>&rsquo;,

  195. &lsquo;<samp>SYNCID</samp>&rsquo;,

  196. can have a value nearby <a name="GREG_002dbase"></a>an initial value in place of its

  197. second and third operands.  Here, &ldquo;nearby&rdquo; is defined as within the

  198. range 0&hellip;255 from the initial value of such an allocated register.

  199. </p>

  200. <div class="smallexample">

  201. <pre class="smallexample">buffer1 BYTE 0,0,0,0,0

  202. buffer2 BYTE 0,0,0,0,0

  203.  &hellip;

  204.  GREG buffer1

  205.  LDOU $42,buffer2

  206. </pre></div>

  207. <p>In the example above, the &lsquo;<samp>Y</samp>&rsquo; field of the <code>LDOUI</code> instruction

  208. (LDOU with a constant Z) will be replaced with the global register

  209. allocated for &lsquo;<samp>buffer1</samp>&rsquo;, and the &lsquo;<samp>Z</samp>&rsquo; field will have the value

  210. 5, the offset from &lsquo;<samp>buffer1</samp>&rsquo; to &lsquo;<samp>buffer2</samp>&rsquo;.  The result is

  211. equivalent to this code:

  212. </p><div class="smallexample">

  213. <pre class="smallexample">buffer1 BYTE 0,0,0,0,0

  214. buffer2 BYTE 0,0,0,0,0

  215.  &hellip;

  216. tmpreg GREG buffer1

  217.  LDOU $42,tmpreg,(buffer2-buffer1)

  218. </pre></div>

  219. 

  220. <p>Global registers allocated with this directive are allocated in order

  221. higher-to-lower within a file.  Other than that, the exact order of

  222. register allocation and elimination is undefined.  For example, the order

  223. is undefined when more than one file with such directives are linked

  224. together.  With the options &lsquo;<samp>-x</samp>&rsquo; and &lsquo;<samp>--linker-allocated-gregs</samp>&rsquo;,

  225. &lsquo;<samp>GREG</samp>&rsquo; directives for two-operand cases like the one mentioned above

  226. can be omitted.  Sufficient global registers will then be allocated by the

  227. linker.

  228. </p>

  229. </dd>

  230. <dt><code>BYTE</code></dt>

  231. <dd><a name="index-assembler-directive-BYTE_002c-MMIX"></a>

  232. <a name="index-pseudo_002dop-BYTE_002c-MMIX"></a>

  233. <a name="index-MMIX-assembler-directive-BYTE"></a>

  234. <a name="index-MMIX-pseudo_002dop-BYTE"></a>

  235. 

  236. <a name="MMIX_002dbyte"></a><p>The &lsquo;<samp>BYTE</samp>&rsquo; directive takes a series of operands separated by a comma.

  237. If an operand is a string (see <a href="Strings.html#Strings">Strings</a>), each character of that string

  238. is emitted as a byte.  Other operands must be constant expressions without

  239. forward references, in the range 0&hellip;255.  If you need operands having

  240. expressions with forward references, use &lsquo;<samp>.byte</samp>&rsquo; (see <a href="Byte.html#Byte">Byte</a>).  An

  241. operand can be omitted, defaulting to a zero value.

  242. </p>

  243. </dd>

  244. <dt><code>WYDE</code></dt>

  245. <dt><code>TETRA</code></dt>

  246. <dt><code>OCTA</code></dt>

  247. <dd><a name="index-assembler-directive-WYDE_002c-MMIX"></a>

  248. <a name="index-pseudo_002dop-WYDE_002c-MMIX"></a>

  249. <a name="index-MMIX-assembler-directive-WYDE"></a>

  250. <a name="index-MMIX-pseudo_002dop-WYDE"></a>

  251. <a name="index-assembler-directive-TETRA_002c-MMIX"></a>

  252. <a name="index-pseudo_002dop-TETRA_002c-MMIX"></a>

  253. <a name="index-MMIX-assembler-directive-TETRA"></a>

  254. <a name="index-MMIX-pseudo_002dop-TETRA"></a>

  255. <a name="index-assembler-directive-OCTA_002c-MMIX"></a>

  256. <a name="index-pseudo_002dop-OCTA_002c-MMIX"></a>

  257. <a name="index-MMIX-assembler-directive-OCTA"></a>

  258. <a name="index-MMIX-pseudo_002dop-OCTA"></a>

  259. 

  260. <a name="MMIX_002dconstants"></a><p>The directives &lsquo;<samp>WYDE</samp>&rsquo;, &lsquo;<samp>TETRA</samp>&rsquo; and &lsquo;<samp>OCTA</samp>&rsquo; emit constants of

  261. two, four and eight bytes size respectively.  Before anything else happens

  262. for the directive, the current location is aligned to the respective

  263. constant-size boundary.  If a label is defined at the beginning of the

  264. line, its value will be that after the alignment.  A single operand can be

  265. omitted, defaulting to a zero value emitted for the directive.  Operands

  266. can be expressed as strings (see <a href="Strings.html#Strings">Strings</a>), in which case each

  267. character in the string is emitted as a separate constant of the size

  268. indicated by the directive.

  269. </p>

  270. </dd>

  271. <dt><code>PREFIX</code></dt>

  272. <dd><a name="index-assembler-directive-PREFIX_002c-MMIX"></a>

  273. <a name="index-pseudo_002dop-PREFIX_002c-MMIX"></a>

  274. <a name="index-MMIX-assembler-directive-PREFIX"></a>

  275. <a name="index-MMIX-pseudo_002dop-PREFIX"></a>

  276. 

  277. <a name="MMIX_002dprefix"></a><p>The &lsquo;<samp>PREFIX</samp>&rsquo; directive sets a symbol name prefix to be prepended to

  278. all symbols (except local symbols, see <a href="MMIX_002dSymbols.html#MMIX_002dSymbols">MMIX-Symbols</a>), that are not

  279. prefixed with &lsquo;<samp>:</samp>&rsquo;, until the next &lsquo;<samp>PREFIX</samp>&rsquo; directive.  Such

  280. prefixes accumulate.  For example,

  281. </p><div class="smallexample">

  282. <pre class="smallexample"> PREFIX a

  283.  PREFIX b

  284. c IS 0

  285. </pre></div>

  286. <p>defines a symbol &lsquo;<samp>abc</samp>&rsquo; with the value 0.

  287. </p>

  288. </dd>

  289. <dt><code>BSPEC</code></dt>

  290. <dt><code>ESPEC</code></dt>

  291. <dd><a name="index-assembler-directive-BSPEC_002c-MMIX"></a>

  292. <a name="index-pseudo_002dop-BSPEC_002c-MMIX"></a>

  293. <a name="index-MMIX-assembler-directive-BSPEC"></a>

  294. <a name="index-MMIX-pseudo_002dop-BSPEC"></a>

  295. <a name="index-assembler-directive-ESPEC_002c-MMIX"></a>

  296. <a name="index-pseudo_002dop-ESPEC_002c-MMIX"></a>

  297. <a name="index-MMIX-assembler-directive-ESPEC"></a>

  298. <a name="index-MMIX-pseudo_002dop-ESPEC"></a>

  299. 

  300. <a name="MMIX_002dspec"></a><p>A pair of &lsquo;<samp>BSPEC</samp>&rsquo; and &lsquo;<samp>ESPEC</samp>&rsquo; directives delimit a section of

  301. special contents (without specified semantics).  Example:

  302. </p><div class="smallexample">

  303. <pre class="smallexample"> BSPEC 42

  304.  TETRA 1,2,3

  305.  ESPEC

  306. </pre></div>

  307. <p>The single operand to &lsquo;<samp>BSPEC</samp>&rsquo; must be number in the range

  308. 0&hellip;255.  The &lsquo;<samp>BSPEC</samp>&rsquo; number 80 is used by the GNU binutils

  309. implementation.

  310. </p></dd>

  311. </dl>

  312. 

  313. <hr>

  314. <div class="header">

  315. <p>

  316. Previous: <a href="MMIX_002dRegs.html#MMIX_002dRegs" accesskey="p" rel="prev">MMIX-Regs</a>, Up: <a href="MMIX_002dSyntax.html#MMIX_002dSyntax" accesskey="u" rel="up">MMIX-Syntax</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>

  317. </div>

  318. 

  319. 

  320. 

  321. </body>

  322. </html>