| <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> |
| <html> |
| <!-- This file documents the GNU Assembler "as". |
| |
| Copyright (C) 1991-2013 Free Software Foundation, Inc. |
| |
| Permission is granted to copy, distribute and/or modify this document |
| under the terms of the GNU Free Documentation License, Version 1.3 |
| or any later version published by the Free Software Foundation; |
| with no Invariant Sections, with no Front-Cover Texts, and with no |
| Back-Cover Texts. A copy of the license is included in the |
| section entitled "GNU Free Documentation License". |
| --> |
| <!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ --> |
| <head> |
| <title>Using as: MMIX-Pseudos</title> |
| |
| <meta name="description" content="Using as: MMIX-Pseudos"> |
| <meta name="keywords" content="Using as: MMIX-Pseudos"> |
| <meta name="resource-type" content="document"> |
| <meta name="distribution" content="global"> |
| <meta name="Generator" content="makeinfo"> |
| <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> |
| <link href="index.html#Top" rel="start" title="Top"> |
| <link href="AS-Index.html#AS-Index" rel="index" title="AS Index"> |
| <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> |
| <link href="MMIX_002dSyntax.html#MMIX_002dSyntax" rel="up" title="MMIX-Syntax"> |
| <link href="MMIX_002dmmixal.html#MMIX_002dmmixal" rel="next" title="MMIX-mmixal"> |
| <link href="MMIX_002dRegs.html#MMIX_002dRegs" rel="prev" title="MMIX-Regs"> |
| <style type="text/css"> |
| <!-- |
| a.summary-letter {text-decoration: none} |
| blockquote.smallquotation {font-size: smaller} |
| div.display {margin-left: 3.2em} |
| div.example {margin-left: 3.2em} |
| div.indentedblock {margin-left: 3.2em} |
| div.lisp {margin-left: 3.2em} |
| div.smalldisplay {margin-left: 3.2em} |
| div.smallexample {margin-left: 3.2em} |
| div.smallindentedblock {margin-left: 3.2em; font-size: smaller} |
| div.smalllisp {margin-left: 3.2em} |
| kbd {font-style:oblique} |
| pre.display {font-family: inherit} |
| pre.format {font-family: inherit} |
| pre.menu-comment {font-family: serif} |
| pre.menu-preformatted {font-family: serif} |
| pre.smalldisplay {font-family: inherit; font-size: smaller} |
| pre.smallexample {font-size: smaller} |
| pre.smallformat {font-family: inherit; font-size: smaller} |
| pre.smalllisp {font-size: smaller} |
| span.nocodebreak {white-space:nowrap} |
| span.nolinebreak {white-space:nowrap} |
| span.roman {font-family:serif; font-weight:normal} |
| span.sansserif {font-family:sans-serif; font-weight:normal} |
| ul.no-bullet {list-style: none} |
| --> |
| </style> |
| |
| |
| </head> |
| |
| <body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> |
| <a name="MMIX_002dPseudos"></a> |
| <div class="header"> |
| <p> |
| 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> [<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> |
| </div> |
| <hr> |
| <a name="Assembler-Directives-3"></a> |
| <h4 class="subsubsection">9.28.3.4 Assembler Directives</h4> |
| <a name="index-assembler-directives_002c-MMIX"></a> |
| <a name="index-pseudo_002dops_002c-MMIX"></a> |
| <a name="index-MMIX-assembler-directives"></a> |
| <a name="index-MMIX-pseudo_002dops"></a> |
| |
| <dl compact="compact"> |
| <dt><code>LOC</code></dt> |
| <dd><a name="index-assembler-directive-LOC_002c-MMIX"></a> |
| <a name="index-pseudo_002dop-LOC_002c-MMIX"></a> |
| <a name="index-MMIX-assembler-directive-LOC"></a> |
| <a name="index-MMIX-pseudo_002dop-LOC"></a> |
| |
| <a name="MMIX_002dloc"></a><p>The <code>LOC</code> directive sets the current location to the value of the |
| operand field, which may include changing sections. If the operand is a |
| constant, the section is set to either <code>.data</code> if the value is |
| <code>0x2000000000000000</code> or larger, else it is set to <code>.text</code>. |
| Within a section, the current location may only be changed to |
| monotonically higher addresses. A LOC expression must be a previously |
| defined symbol or a “pure” constant. |
| </p> |
| <p>An example, which sets the label <var>prev</var> to the current location, and |
| updates the current location to eight bytes forward: |
| </p><div class="smallexample"> |
| <pre class="smallexample">prev LOC @+8 |
| </pre></div> |
| |
| <p>When a LOC has a constant as its operand, a symbol |
| <code>__.MMIX.start..text</code> or <code>__.MMIX.start..data</code> is defined |
| depending on the address as mentioned above. Each such symbol is |
| interpreted as special by the linker, locating the section at that |
| address. Note that if multiple files are linked, the first object file |
| with that section will be mapped to that address (not necessarily the file |
| with the LOC definition). |
| </p> |
| </dd> |
| <dt><code>LOCAL</code></dt> |
| <dd><a name="index-assembler-directive-LOCAL_002c-MMIX"></a> |
| <a name="index-pseudo_002dop-LOCAL_002c-MMIX"></a> |
| <a name="index-MMIX-assembler-directive-LOCAL"></a> |
| <a name="index-MMIX-pseudo_002dop-LOCAL"></a> |
| |
| <a name="MMIX_002dlocal"></a><p>Example: |
| </p><div class="smallexample"> |
| <pre class="smallexample"> LOCAL external_symbol |
| LOCAL 42 |
| .local asymbol |
| </pre></div> |
| |
| <p>This directive-operation generates a link-time assertion that the operand |
| does not correspond to a global register. The operand is an expression |
| that at link-time resolves to a register symbol or a number. A number is |
| treated as the register having that number. There is one restriction on |
| the use of this directive: the pseudo-directive must be placed in a |
| section with contents, code or data. |
| </p> |
| </dd> |
| <dt><code>IS</code></dt> |
| <dd><a name="index-assembler-directive-IS_002c-MMIX"></a> |
| <a name="index-pseudo_002dop-IS_002c-MMIX"></a> |
| <a name="index-MMIX-assembler-directive-IS"></a> |
| <a name="index-MMIX-pseudo_002dop-IS"></a> |
| |
| <a name="MMIX_002dis"></a><p>The <code>IS</code> directive: |
| </p><div class="smallexample"> |
| <pre class="smallexample">asymbol IS an_expression |
| </pre></div> |
| <p>sets the symbol ‘<samp>asymbol</samp>’ to ‘<samp>an_expression</samp>’. A symbol may not |
| be set more than once using this directive. Local labels may be set using |
| this directive, for example: |
| </p><div class="smallexample"> |
| <pre class="smallexample">5H IS @+4 |
| </pre></div> |
| |
| </dd> |
| <dt><code>GREG</code></dt> |
| <dd><a name="index-assembler-directive-GREG_002c-MMIX"></a> |
| <a name="index-pseudo_002dop-GREG_002c-MMIX"></a> |
| <a name="index-MMIX-assembler-directive-GREG"></a> |
| <a name="index-MMIX-pseudo_002dop-GREG"></a> |
| |
| <a name="MMIX_002dgreg"></a><p>This directive reserves a global register, gives it an initial value and |
| optionally gives it a symbolic name. Some examples: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">areg GREG |
| breg GREG data_value |
| GREG data_buffer |
| .greg creg, another_data_value |
| </pre></div> |
| |
| <p>The symbolic register name can be used in place of a (non-special) |
| register. If a value isn’t provided, it defaults to zero. Unless the |
| option ‘<samp>--no-merge-gregs</samp>’ is specified, non-zero registers allocated |
| with this directive may be eliminated by <code>as</code>; another |
| register with the same value used in its place. |
| Any of the instructions |
| ‘<samp>CSWAP</samp>’, |
| ‘<samp>GO</samp>’, |
| ‘<samp>LDA</samp>’, |
| ‘<samp>LDBU</samp>’, |
| ‘<samp>LDB</samp>’, |
| ‘<samp>LDHT</samp>’, |
| ‘<samp>LDOU</samp>’, |
| ‘<samp>LDO</samp>’, |
| ‘<samp>LDSF</samp>’, |
| ‘<samp>LDTU</samp>’, |
| ‘<samp>LDT</samp>’, |
| ‘<samp>LDUNC</samp>’, |
| ‘<samp>LDVTS</samp>’, |
| ‘<samp>LDWU</samp>’, |
| ‘<samp>LDW</samp>’, |
| ‘<samp>PREGO</samp>’, |
| ‘<samp>PRELD</samp>’, |
| ‘<samp>PREST</samp>’, |
| ‘<samp>PUSHGO</samp>’, |
| ‘<samp>STBU</samp>’, |
| ‘<samp>STB</samp>’, |
| ‘<samp>STCO</samp>’, |
| ‘<samp>STHT</samp>’, |
| ‘<samp>STOU</samp>’, |
| ‘<samp>STSF</samp>’, |
| ‘<samp>STTU</samp>’, |
| ‘<samp>STT</samp>’, |
| ‘<samp>STUNC</samp>’, |
| ‘<samp>SYNCD</samp>’, |
| ‘<samp>SYNCID</samp>’, |
| can have a value nearby <a name="GREG_002dbase"></a>an initial value in place of its |
| second and third operands. Here, “nearby” is defined as within the |
| range 0…255 from the initial value of such an allocated register. |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">buffer1 BYTE 0,0,0,0,0 |
| buffer2 BYTE 0,0,0,0,0 |
| … |
| GREG buffer1 |
| LDOU $42,buffer2 |
| </pre></div> |
| <p>In the example above, the ‘<samp>Y</samp>’ field of the <code>LDOUI</code> instruction |
| (LDOU with a constant Z) will be replaced with the global register |
| allocated for ‘<samp>buffer1</samp>’, and the ‘<samp>Z</samp>’ field will have the value |
| 5, the offset from ‘<samp>buffer1</samp>’ to ‘<samp>buffer2</samp>’. The result is |
| equivalent to this code: |
| </p><div class="smallexample"> |
| <pre class="smallexample">buffer1 BYTE 0,0,0,0,0 |
| buffer2 BYTE 0,0,0,0,0 |
| … |
| tmpreg GREG buffer1 |
| LDOU $42,tmpreg,(buffer2-buffer1) |
| </pre></div> |
| |
| <p>Global registers allocated with this directive are allocated in order |
| higher-to-lower within a file. Other than that, the exact order of |
| register allocation and elimination is undefined. For example, the order |
| is undefined when more than one file with such directives are linked |
| together. With the options ‘<samp>-x</samp>’ and ‘<samp>--linker-allocated-gregs</samp>’, |
| ‘<samp>GREG</samp>’ directives for two-operand cases like the one mentioned above |
| can be omitted. Sufficient global registers will then be allocated by the |
| linker. |
| </p> |
| </dd> |
| <dt><code>BYTE</code></dt> |
| <dd><a name="index-assembler-directive-BYTE_002c-MMIX"></a> |
| <a name="index-pseudo_002dop-BYTE_002c-MMIX"></a> |
| <a name="index-MMIX-assembler-directive-BYTE"></a> |
| <a name="index-MMIX-pseudo_002dop-BYTE"></a> |
| |
| <a name="MMIX_002dbyte"></a><p>The ‘<samp>BYTE</samp>’ directive takes a series of operands separated by a comma. |
| If an operand is a string (see <a href="Strings.html#Strings">Strings</a>), each character of that string |
| is emitted as a byte. Other operands must be constant expressions without |
| forward references, in the range 0…255. If you need operands having |
| expressions with forward references, use ‘<samp>.byte</samp>’ (see <a href="Byte.html#Byte">Byte</a>). An |
| operand can be omitted, defaulting to a zero value. |
| </p> |
| </dd> |
| <dt><code>WYDE</code></dt> |
| <dt><code>TETRA</code></dt> |
| <dt><code>OCTA</code></dt> |
| <dd><a name="index-assembler-directive-WYDE_002c-MMIX"></a> |
| <a name="index-pseudo_002dop-WYDE_002c-MMIX"></a> |
| <a name="index-MMIX-assembler-directive-WYDE"></a> |
| <a name="index-MMIX-pseudo_002dop-WYDE"></a> |
| <a name="index-assembler-directive-TETRA_002c-MMIX"></a> |
| <a name="index-pseudo_002dop-TETRA_002c-MMIX"></a> |
| <a name="index-MMIX-assembler-directive-TETRA"></a> |
| <a name="index-MMIX-pseudo_002dop-TETRA"></a> |
| <a name="index-assembler-directive-OCTA_002c-MMIX"></a> |
| <a name="index-pseudo_002dop-OCTA_002c-MMIX"></a> |
| <a name="index-MMIX-assembler-directive-OCTA"></a> |
| <a name="index-MMIX-pseudo_002dop-OCTA"></a> |
| |
| <a name="MMIX_002dconstants"></a><p>The directives ‘<samp>WYDE</samp>’, ‘<samp>TETRA</samp>’ and ‘<samp>OCTA</samp>’ emit constants of |
| two, four and eight bytes size respectively. Before anything else happens |
| for the directive, the current location is aligned to the respective |
| constant-size boundary. If a label is defined at the beginning of the |
| line, its value will be that after the alignment. A single operand can be |
| omitted, defaulting to a zero value emitted for the directive. Operands |
| can be expressed as strings (see <a href="Strings.html#Strings">Strings</a>), in which case each |
| character in the string is emitted as a separate constant of the size |
| indicated by the directive. |
| </p> |
| </dd> |
| <dt><code>PREFIX</code></dt> |
| <dd><a name="index-assembler-directive-PREFIX_002c-MMIX"></a> |
| <a name="index-pseudo_002dop-PREFIX_002c-MMIX"></a> |
| <a name="index-MMIX-assembler-directive-PREFIX"></a> |
| <a name="index-MMIX-pseudo_002dop-PREFIX"></a> |
| |
| <a name="MMIX_002dprefix"></a><p>The ‘<samp>PREFIX</samp>’ directive sets a symbol name prefix to be prepended to |
| all symbols (except local symbols, see <a href="MMIX_002dSymbols.html#MMIX_002dSymbols">MMIX-Symbols</a>), that are not |
| prefixed with ‘<samp>:</samp>’, until the next ‘<samp>PREFIX</samp>’ directive. Such |
| prefixes accumulate. For example, |
| </p><div class="smallexample"> |
| <pre class="smallexample"> PREFIX a |
| PREFIX b |
| c IS 0 |
| </pre></div> |
| <p>defines a symbol ‘<samp>abc</samp>’ with the value 0. |
| </p> |
| </dd> |
| <dt><code>BSPEC</code></dt> |
| <dt><code>ESPEC</code></dt> |
| <dd><a name="index-assembler-directive-BSPEC_002c-MMIX"></a> |
| <a name="index-pseudo_002dop-BSPEC_002c-MMIX"></a> |
| <a name="index-MMIX-assembler-directive-BSPEC"></a> |
| <a name="index-MMIX-pseudo_002dop-BSPEC"></a> |
| <a name="index-assembler-directive-ESPEC_002c-MMIX"></a> |
| <a name="index-pseudo_002dop-ESPEC_002c-MMIX"></a> |
| <a name="index-MMIX-assembler-directive-ESPEC"></a> |
| <a name="index-MMIX-pseudo_002dop-ESPEC"></a> |
| |
| <a name="MMIX_002dspec"></a><p>A pair of ‘<samp>BSPEC</samp>’ and ‘<samp>ESPEC</samp>’ directives delimit a section of |
| special contents (without specified semantics). Example: |
| </p><div class="smallexample"> |
| <pre class="smallexample"> BSPEC 42 |
| TETRA 1,2,3 |
| ESPEC |
| </pre></div> |
| <p>The single operand to ‘<samp>BSPEC</samp>’ must be number in the range |
| 0…255. The ‘<samp>BSPEC</samp>’ number 80 is used by the GNU binutils |
| implementation. |
| </p></dd> |
| </dl> |
| |
| <hr> |
| <div class="header"> |
| <p> |
| 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> [<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> |
| </div> |
| |
| |
| |
| </body> |
| </html> |
