87 lines
4.0 KiB
HTML
87 lines
4.0 KiB
HTML
|
<html lang="en">
|
||
|
|
<head>
|
||
|
|
<title>M68HC11/68HC12 - Untitled</title>
|
||
|
|
<meta http-equiv="Content-Type" content="text/html">
|
||
|
|
<meta name="description" content="Untitled">
|
||
|
|
<meta name="generator" content="makeinfo 4.13">
|
||
|
|
<link title="Top" rel="start" href="index.html#Top">
|
||
|
|
<link rel="up" href="Machine-Dependent.html#Machine-Dependent" title="Machine Dependent">
|
||
|
|
<link rel="prev" href="H8_002f300.html#H8_002f300" title="H8/300">
|
||
|
|
<link rel="next" href="ARM.html#ARM" title="ARM">
|
||
|
|
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
|
||
|
|
<!--
|
||
|
|
This file documents the GNU linker LD
|
||
|
|
(GNU Toolchain for the A-profile Architecture 9.2-2019.12 (arm-9.10))
|
||
|
|
version 2.33.1.
|
||
|
|
|
||
|
|
Copyright (C) 1991-2019 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="M68HC11%2f68HC12"></a>
|
||
|
|
<a name="M68HC11_002f68HC12"></a>
|
||
|
|
<p>
|
||
|
|
Next: <a rel="next" accesskey="n" href="ARM.html#ARM">ARM</a>,
|
||
|
|
Previous: <a rel="previous" accesskey="p" href="H8_002f300.html#H8_002f300">H8/300</a>,
|
||
|
|
Up: <a rel="up" accesskey="u" href="Machine-Dependent.html#Machine-Dependent">Machine Dependent</a>
|
||
|
|
<hr>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<h3 class="section">4.2 <samp><span class="command">ld</span></samp> and the Motorola 68HC11 and 68HC12 families</h3>
|
||
|
|
|
||
|
|
<p><a name="index-M68HC11-and-68HC12-support-625"></a>
|
||
|
|
|
||
|
|
<h4 class="subsection">4.2.1 Linker Relaxation</h4>
|
||
|
|
|
||
|
|
<p>For the Motorola 68HC11, <samp><span class="command">ld</span></samp> can perform these global
|
||
|
|
optimizations when you specify the ‘<samp><span class="samp">--relax</span></samp>’ command-line option.
|
||
|
|
|
||
|
|
|
||
|
|
<a name="index-relaxing-on-M68HC11-626"></a>
|
||
|
|
<dl><dt><em>relaxing address modes</em><dd><samp><span class="command">ld</span></samp> finds all <code>jsr</code> and <code>jmp</code> instructions whose
|
||
|
|
targets are within eight bits, and turns them into eight-bit
|
||
|
|
program-counter relative <code>bsr</code> and <code>bra</code> instructions,
|
||
|
|
respectively.
|
||
|
|
|
||
|
|
<p><samp><span class="command">ld</span></samp> also looks at all 16-bit extended addressing modes and
|
||
|
|
transforms them in a direct addressing mode when the address is in
|
||
|
|
page 0 (between 0 and 0x0ff).
|
||
|
|
|
||
|
|
<br><dt><em>relaxing gcc instruction group</em><dd>When <samp><span class="command">gcc</span></samp> is called with <samp><span class="option">-mrelax</span></samp>, it can emit group
|
||
|
|
of instructions that the linker can optimize to use a 68HC11 direct
|
||
|
|
addressing mode. These instructions consists of <code>bclr</code> or
|
||
|
|
<code>bset</code> instructions.
|
||
|
|
|
||
|
|
</dl>
|
||
|
|
|
||
|
|
<h4 class="subsection">4.2.2 Trampoline Generation</h4>
|
||
|
|
|
||
|
|
<p><a name="index-trampoline-generation-on-M68HC11-627"></a><a name="index-trampoline-generation-on-M68HC12-628"></a>For 68HC11 and 68HC12, <samp><span class="command">ld</span></samp> can generate trampoline code to
|
||
|
|
call a far function using a normal <code>jsr</code> instruction. The linker
|
||
|
|
will also change the relocation to some far function to use the
|
||
|
|
trampoline address instead of the function address. This is typically the
|
||
|
|
case when a pointer to a function is taken. The pointer will in fact
|
||
|
|
point to the function trampoline.
|
||
|
|
|
||
|
|
</body></html>
|
||
|
|
|