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103 lines
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103 lines
4.3 KiB
HTML
15 years ago
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<title>M32C-Modifiers - Using as</title>
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<meta name="description" content="Using as">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="M32C_002dDependent.html#M32C_002dDependent" title="M32C-Dependent">
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<link rel="prev" href="M32C_002dOpts.html#M32C_002dOpts" title="M32C-Opts">
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<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
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<!--
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This file documents the GNU Assembler "as".
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Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002,
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2006, 2007 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.1
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or any later version published by the Free Software Foundation;
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with no Invariant Sections, with no Front-Cover Texts, and with no
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Back-Cover Texts. A copy of the license is included in the
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section entitled ``GNU Free Documentation License''.
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<body>
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<div class="node">
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<p>
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<a name="M32C_002dModifiers"></a>Previous: <a rel="previous" accesskey="p" href="M32C_002dOpts.html#M32C_002dOpts">M32C-Opts</a>,
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Up: <a rel="up" accesskey="u" href="M32C_002dDependent.html#M32C_002dDependent">M32C-Dependent</a>
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<hr><br>
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</div>
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<h4 class="subsection">9.18.2 Symbolic Operand Modifiers</h4>
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<p><a name="index-M32C-modifiers-1035"></a><a name="index-syntax_002c-M32C-1036"></a>
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The assembler supports several modifiers when using symbol addresses
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in M32C instruction operands. The general syntax is the following:
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<pre class="smallexample"> %modifier(symbol)
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</pre>
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<a name="index-symbol-modifiers-1037"></a>
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<dl>
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<dt><code>%dsp8</code><dt><code>%dsp16</code><dd>
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These modifiers override the assembler's assumptions about how big a
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symbol's address is. Normally, when it sees an operand like
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<span class="samp">sym[a0]</span> it assumes <span class="samp">sym</span> may require the widest
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displacement field (16 bits for <span class="samp">-m16c</span>, 24 bits for
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<span class="samp">-m32c</span>). These modifiers tell it to assume the address will fit
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in an 8 or 16 bit (respectively) unsigned displacement. Note that, of
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course, if it doesn't actually fit you will get linker errors. Example:
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<pre class="smallexample"> mov.w %dsp8(sym)[a0],r1
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mov.b #0,%dsp8(sym)[a0]
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</pre>
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<br><dt><code>%hi8</code><dd>
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This modifier allows you to load bits 16 through 23 of a 24 bit
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address into an 8 bit register. This is useful with, for example, the
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M16C <span class="samp">smovf</span> instruction, which expects a 20 bit address in
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<span class="samp">r1h</span> and <span class="samp">a0</span>. Example:
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<pre class="smallexample"> mov.b #%hi8(sym),r1h
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mov.w #%lo16(sym),a0
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smovf.b
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</pre>
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<br><dt><code>%lo16</code><dd>
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Likewise, this modifier allows you to load bits 0 through 15 of a 24
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bit address into a 16 bit register.
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<br><dt><code>%hi16</code><dd>
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This modifier allows you to load bits 16 through 31 of a 32 bit
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address into a 16 bit register. While the M32C family only has 24
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bits of address space, it does support addresses in pairs of 16 bit
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registers (like <span class="samp">a1a0</span> for the <span class="samp">lde</span> instruction). This
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modifier is for loading the upper half in such cases. Example:
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<pre class="smallexample"> mov.w #%hi16(sym),a1
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mov.w #%lo16(sym),a0
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...
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lde.w [a1a0],r1
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</pre>
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</dl>
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<!-- Copyright 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, -->
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<!-- 2000, 2003, 2004 -->
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<!-- Free Software Foundation, Inc. -->
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<!-- This is part of the GAS manual. -->
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<!-- For copying conditions, see the file as.texinfo. -->
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</body></html>
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