<html lang="en">
<head>
<title>M32R-Directives - 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="M32R_002dDependent.html#M32R_002dDependent" title="M32R-Dependent">
<link rel="prev" href="M32R_002dOpts.html#M32R_002dOpts" title="M32R-Opts">
<link rel="next" href="M32R_002dWarnings.html#M32R_002dWarnings" title="M32R-Warnings">
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
<!--
This file documents the GNU Assembler "as".

Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
2000, 2001, 2002, 2006, 2007, 2008, 2009, 2010 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>
<link rel="stylesheet" type="text/css" href="../cs.css">
</head>
<body>
<div class="node">
<a name="M32R-Directives"></a>
<a name="M32R_002dDirectives"></a>
<p>
Next:&nbsp;<a rel="next" accesskey="n" href="M32R_002dWarnings.html#M32R_002dWarnings">M32R-Warnings</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="M32R_002dOpts.html#M32R_002dOpts">M32R-Opts</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="M32R_002dDependent.html#M32R_002dDependent">M32R-Dependent</a>
<hr>
</div>

<h4 class="subsection">9.20.2 M32R Directives</h4>

<p><a name="index-directives_002c-M32R-1127"></a><a name="index-M32R-directives-1128"></a>
The Renease M32R version of <code>as</code> has a few architecture
specific directives:

     
<a name="index-g_t_0040code_007blow_007d-directive_002c-M32R-1129"></a>
<dl><dt><code>low </code><var>expression</var><dd>The <code>low</code> directive computes the value of its expression and
places the lower 16-bits of the result into the immediate-field of the
instruction.  For example:

     <pre class="smallexample">             or3   r0, r0, #low(0x12345678) ; compute r0 = r0 | 0x5678
             add3, r0, r0, #low(fred)   ; compute r0 = r0 + low 16-bits of address of fred
</pre>
     <br><dt><code>high </code><var>expression</var><dd><a name="index-g_t_0040code_007bhigh_007d-directive_002c-M32R-1130"></a>The <code>high</code> directive computes the value of its expression and
places the upper 16-bits of the result into the immediate-field of the
instruction.  For example:

     <pre class="smallexample">             seth  r0, #high(0x12345678) ; compute r0 = 0x12340000
             seth, r0, #high(fred)       ; compute r0 = upper 16-bits of address of fred
</pre>
     <br><dt><code>shigh </code><var>expression</var><dd><a name="index-g_t_0040code_007bshigh_007d-directive_002c-M32R-1131"></a>The <code>shigh</code> directive is very similar to the <code>high</code>
directive.  It also computes the value of its expression and places
the upper 16-bits of the result into the immediate-field of the
instruction.  The difference is that <code>shigh</code> also checks to see
if the lower 16-bits could be interpreted as a signed number, and if
so it assumes that a borrow will occur from the upper-16 bits.  To
compensate for this the <code>shigh</code> directive pre-biases the upper
16 bit value by adding one to it.  For example:

     <p>For example:

     <pre class="smallexample">             seth  r0, #shigh(0x12345678) ; compute r0 = 0x12340000
             seth  r0, #shigh(0x00008000) ; compute r0 = 0x00010000
</pre>
     <p>In the second example the lower 16-bits are 0x8000.  If these are
treated as a signed value and sign extended to 32-bits then the value
becomes 0xffff8000.  If this value is then added to 0x00010000 then
the result is 0x00008000.

     <p>This behaviour is to allow for the different semantics of the
<code>or3</code> and <code>add3</code> instructions.  The <code>or3</code> instruction
treats its 16-bit immediate argument as unsigned whereas the
<code>add3</code> treats its 16-bit immediate as a signed value.  So for
example:

     <pre class="smallexample">             seth  r0, #shigh(0x00008000)
             add3  r0, r0, #low(0x00008000)
</pre>
     <p>Produces the correct result in r0, whereas:

     <pre class="smallexample">             seth  r0, #shigh(0x00008000)
             or3   r0, r0, #low(0x00008000)
</pre>
     <p>Stores 0xffff8000 into r0.

     <p>Note - the <code>shigh</code> directive does not know where in the assembly
source code the lower 16-bits of the value are going set, so it cannot
check to make sure that an <code>or3</code> instruction is being used rather
than an <code>add3</code> instruction.  It is up to the programmer to make
sure that correct directives are used.

     <p><a name="index-g_t_0040code_007b_002em32r_007d-directive_002c-M32R-1132"></a><br><dt><code>.m32r</code><dd>The directive performs a similar thing as the <em>-m32r</em> command
line option.  It tells the assembler to only accept M32R instructions
from now on.  An instructions from later M32R architectures are
refused.

     <p><a name="index-g_t_0040code_007b_002em32rx_007d-directive_002c-M32RX-1133"></a><br><dt><code>.m32rx</code><dd>The directive performs a similar thing as the <em>-m32rx</em> command
line option.  It tells the assembler to start accepting the extra
instructions in the M32RX ISA as well as the ordinary M32R ISA.

     <p><a name="index-g_t_0040code_007b_002em32r2_007d-directive_002c-M32R2-1134"></a><br><dt><code>.m32r2</code><dd>The directive performs a similar thing as the <em>-m32r2</em> command
line option.  It tells the assembler to start accepting the extra
instructions in the M32R2 ISA as well as the ordinary M32R ISA.

     <p><a name="index-g_t_0040code_007b_002elittle_007d-directive_002c-M32RX-1135"></a><br><dt><code>.little</code><dd>The directive performs a similar thing as the <em>-little</em> command
line option.  It tells the assembler to start producing little-endian
code and data.  This option should be used with care as producing
mixed-endian binary files is fraught with danger.

     <p><a name="index-g_t_0040code_007b_002ebig_007d-directive_002c-M32RX-1136"></a><br><dt><code>.big</code><dd>The directive performs a similar thing as the <em>-big</em> command
line option.  It tells the assembler to start producing big-endian
code and data.  This option should be used with care as producing
mixed-endian binary files is fraught with danger.

   </dl>

   </body></html>