You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
103 lines
5.0 KiB
HTML
103 lines
5.0 KiB
HTML
4 years ago
|
<html lang="en">
|
||
|
|
<head>
|
||
|
|
<title>Xtensa Syntax - Using as</title>
|
||
|
|
<meta http-equiv="Content-Type" content="text/html">
|
||
|
|
<meta name="description" content="Using as">
|
||
|
|
<meta name="generator" content="makeinfo 4.13">
|
||
|
|
<link title="Top" rel="start" href="index.html#Top">
|
||
|
|
<link rel="up" href="Xtensa_002dDependent.html#Xtensa_002dDependent" title="Xtensa-Dependent">
|
||
|
|
<link rel="prev" href="Xtensa-Options.html#Xtensa-Options" title="Xtensa Options">
|
||
|
|
<link rel="next" href="Xtensa-Optimizations.html#Xtensa-Optimizations" title="Xtensa Optimizations">
|
||
|
|
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
|
||
|
|
<!--
|
||
|
|
This file documents the GNU Assembler "as".
|
||
|
|
|
||
|
|
Copyright (C) 1991-2015 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''.
|
||
|
|
|
||
|
|
-->
|
||
|
|
<meta http-equiv="Content-Style-Type" content="text/css">
|
||
|
|
<style type="text/css"><!--
|
||
|
|
pre.display { font-family:inherit }
|
||
|
|
pre.format { font-family:inherit }
|
||
|
|
pre.smalldisplay { font-family:inherit; font-size:smaller }
|
||
|
|
pre.smallformat { font-family:inherit; font-size:smaller }
|
||
|
|
pre.smallexample { font-size:smaller }
|
||
|
|
pre.smalllisp { font-size:smaller }
|
||
|
|
span.sc { font-variant:small-caps }
|
||
|
|
span.roman { font-family:serif; font-weight:normal; }
|
||
|
|
span.sansserif { font-family:sans-serif; font-weight:normal; }
|
||
|
|
--></style>
|
||
|
|
</head>
|
||
|
|
<body>
|
||
|
|
<div class="node">
|
||
|
|
<a name="Xtensa-Syntax"></a>
|
||
|
|
<p>
|
||
|
|
Next: <a rel="next" accesskey="n" href="Xtensa-Optimizations.html#Xtensa-Optimizations">Xtensa Optimizations</a>,
|
||
|
|
Previous: <a rel="previous" accesskey="p" href="Xtensa-Options.html#Xtensa-Options">Xtensa Options</a>,
|
||
|
|
Up: <a rel="up" accesskey="u" href="Xtensa_002dDependent.html#Xtensa_002dDependent">Xtensa-Dependent</a>
|
||
|
|
<hr>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<h4 class="subsection">9.52.2 Assembler Syntax</h4>
|
||
|
|
|
||
|
|
<p><a name="index-syntax_002c-Xtensa-assembler-2450"></a><a name="index-Xtensa-assembler-syntax-2451"></a><a name="index-FLIX-syntax-2452"></a>
|
||
|
|
Block comments are delimited by ‘<samp><span class="samp">/*</span></samp>’ and ‘<samp><span class="samp">*/</span></samp>’. End of line
|
||
|
|
comments may be introduced with either ‘<samp><span class="samp">#</span></samp>’ or ‘<samp><span class="samp">//</span></samp>’.
|
||
|
|
|
||
|
|
<p>If a ‘<samp><span class="samp">#</span></samp>’ appears as the first character of a line then the whole
|
||
|
|
line is treated as a comment, but in this case the line could also be
|
||
|
|
a logical line number directive (see <a href="Comments.html#Comments">Comments</a>) or a preprocessor
|
||
|
|
control command (see <a href="Preprocessing.html#Preprocessing">Preprocessing</a>).
|
||
|
|
|
||
|
|
<p>Instructions consist of a leading opcode or macro name followed by
|
||
|
|
whitespace and an optional comma-separated list of operands:
|
||
|
|
|
||
|
|
<pre class="smallexample"> <var>opcode</var> [<var>operand</var>, ...]
|
||
|
|
</pre>
|
||
|
|
<p>Instructions must be separated by a newline or semicolon (‘<samp><span class="samp">;</span></samp>’).
|
||
|
|
|
||
|
|
<p>FLIX instructions, which bundle multiple opcodes together in a single
|
||
|
|
instruction, are specified by enclosing the bundled opcodes inside
|
||
|
|
braces:
|
||
|
|
|
||
|
|
<pre class="smallexample"> {
|
||
|
|
[<var>format</var>]
|
||
|
|
<var>opcode0</var> [<var>operands</var>]
|
||
|
|
<var>opcode1</var> [<var>operands</var>]
|
||
|
|
<var>opcode2</var> [<var>operands</var>]
|
||
|
|
...
|
||
|
|
}
|
||
|
|
</pre>
|
||
|
|
<p>The opcodes in a FLIX instruction are listed in the same order as the
|
||
|
|
corresponding instruction slots in the TIE format declaration.
|
||
|
|
Directives and labels are not allowed inside the braces of a FLIX
|
||
|
|
instruction. A particular TIE format name can optionally be specified
|
||
|
|
immediately after the opening brace, but this is usually unnecessary.
|
||
|
|
The assembler will automatically search for a format that can encode the
|
||
|
|
specified opcodes, so the format name need only be specified in rare
|
||
|
|
cases where there is more than one applicable format and where it
|
||
|
|
matters which of those formats is used. A FLIX instruction can also be
|
||
|
|
specified on a single line by separating the opcodes with semicolons:
|
||
|
|
|
||
|
|
<pre class="smallexample"> { [<var>format</var>;] <var>opcode0</var> [<var>operands</var>]; <var>opcode1</var> [<var>operands</var>]; <var>opcode2</var> [<var>operands</var>]; ... }
|
||
|
|
</pre>
|
||
|
|
<p>If an opcode can only be encoded in a FLIX instruction but is not
|
||
|
|
specified as part of a FLIX bundle, the assembler will choose the
|
||
|
|
smallest format where the opcode can be encoded and
|
||
|
|
will fill unused instruction slots with no-ops.
|
||
|
|
|
||
|
|
<ul class="menu">
|
||
|
|
<li><a accesskey="1" href="Xtensa-Opcodes.html#Xtensa-Opcodes">Xtensa Opcodes</a>: Opcode Naming Conventions.
|
||
|
|
<li><a accesskey="2" href="Xtensa-Registers.html#Xtensa-Registers">Xtensa Registers</a>: Register Naming.
|
||
|
|
</ul>
|
||
|
|
|
||
|
|
</body></html>
|
||
|
|
|