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87 lines
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<!--
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This file documents the GNU linker LD
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(GNU Toolchain for the A-profile Architecture 9.2-2019.12 (arm-9.10))
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version 2.33.1.
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Copyright (C) 1991-2019 Free Software Foundation, Inc.
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<a name="M68HC11_002f68HC12"></a>
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Next: <a rel="next" accesskey="n" href="ARM.html#ARM">ARM</a>,
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<h3 class="section">4.2 <samp><span class="command">ld</span></samp> and the Motorola 68HC11 and 68HC12 families</h3>
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<p><a name="index-M68HC11-and-68HC12-support-625"></a>
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<h4 class="subsection">4.2.1 Linker Relaxation</h4>
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<p>For the Motorola 68HC11, <samp><span class="command">ld</span></samp> can perform these global
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optimizations when you specify the ‘<samp><span class="samp">--relax</span></samp>’ command-line option.
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<a name="index-relaxing-on-M68HC11-626"></a>
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<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
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targets are within eight bits, and turns them into eight-bit
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program-counter relative <code>bsr</code> and <code>bra</code> instructions,
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respectively.
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<p><samp><span class="command">ld</span></samp> also looks at all 16-bit extended addressing modes and
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transforms them in a direct addressing mode when the address is in
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page 0 (between 0 and 0x0ff).
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<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
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of instructions that the linker can optimize to use a 68HC11 direct
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addressing mode. These instructions consists of <code>bclr</code> or
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<code>bset</code> instructions.
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</dl>
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<h4 class="subsection">4.2.2 Trampoline Generation</h4>
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<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
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call a far function using a normal <code>jsr</code> instruction. The linker
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will also change the relocation to some far function to use the
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trampoline address instead of the function address. This is typically the
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case when a pointer to a function is taken. The pointer will in fact
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point to the function trampoline.
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