<html lang="en"> <head> <title>M68HC11-Branch - Using as</title> <meta http-equiv="Content-Type" content="text/html"> <meta name="description" content="Using as"> <meta name="generator" content="makeinfo 4.7"> <link title="Top" rel="start" href="index.html#Top"> <link rel="up" href="M68HC11_002dopcodes.html#M68HC11_002dopcodes" title="M68HC11-opcodes"> <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> <!-- This file documents the GNU Assembler "as". Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002, 2006, 2007 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 1.1 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''. man end--> <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; } --></style> </head> <body> <div class="node"> <p> <a name="M68HC11_002dBranch"></a>Up: <a rel="up" accesskey="u" href="M68HC11_002dopcodes.html#M68HC11_002dopcodes">M68HC11-opcodes</a> <hr><br> </div> <h5 class="subsubsection">9.21.6.1 Branch Improvement</h5> <p><a name="index-pseudo_002dopcodes_002c-M68HC11-1189"></a><a name="index-M68HC11-pseudo_002dopcodes-1190"></a><a name="index-branch-improvement_002c-M68HC11-1191"></a><a name="index-M68HC11-branch-improvement-1192"></a> Certain pseudo opcodes are permitted for branch instructions. They expand to the shortest branch instruction that reach the target. Generally these mnemonics are made by prepending <span class="samp">j</span> to the start of Motorola mnemonic. These pseudo opcodes are not affected by the <span class="samp">--short-branches</span> or <span class="samp">--force-long-branches</span> options. <p>The following table summarizes the pseudo-operations. <pre class="smallexample"> Displacement Width +-------------------------------------------------------------+ | Options | | --short-branches --force-long-branches | +--------------------------+----------------------------------+ Op |BYTE WORD | BYTE WORD | +--------------------------+----------------------------------+ bsr | bsr <pc-rel> <error> | jsr <abs> | bra | bra <pc-rel> <error> | jmp <abs> | jbsr | bsr <pc-rel> jsr <abs> | bsr <pc-rel> jsr <abs> | jbra | bra <pc-rel> jmp <abs> | bra <pc-rel> jmp <abs> | bXX | bXX <pc-rel> <error> | bNX +3; jmp <abs> | jbXX | bXX <pc-rel> bNX +3; | bXX <pc-rel> bNX +3; jmp <abs> | | jmp <abs> | | +--------------------------+----------------------------------+ XX: condition NX: negative of condition XX </pre> <dl> <dt><code>jbsr</code><dt><code>jbra</code><dd>These are the simplest jump pseudo-operations; they always map to one particular machine instruction, depending on the displacement to the branch target. <br><dt><code>jb</code><var>XX</var><dd>Here, <span class="samp">jb</span><var>XX</var> stands for an entire family of pseudo-operations, where <var>XX</var> is a conditional branch or condition-code test. The full list of pseudo-ops in this family is: <pre class="smallexample"> jbcc jbeq jbge jbgt jbhi jbvs jbpl jblo jbcs jbne jblt jble jbls jbvc jbmi </pre> <p>For the cases of non-PC relative displacements and long displacements, <code>as</code> issues a longer code fragment in terms of <var>NX</var>, the opposite condition to <var>XX</var>. For example, for the non-PC relative case: <pre class="smallexample"> jb<var>XX</var> foo </pre> <p>gives <pre class="smallexample"> b<var>NX</var>s oof jmp foo oof: </pre> </dl> <!-- Copyright 1991, 1992, 1993, 1994, 1995, 1997, 1999, 2000, 2001, --> <!-- 2002, 2003, 2004 --> <!-- Free Software Foundation, Inc. --> <!-- This is part of the GAS manual. --> <!-- For copying conditions, see the file as.texinfo. --> </body></html>