<!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) 1991-2021 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 5.1, 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="previous" 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="previous">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="previous">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>
|
