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<h4 class="subsection">9.21.2 M32R Directives</h4>

<p><a name="index-directives_002c-M32R-1385"></a><a name="index-M32R-directives-1386"></a>
The Renesas M32R version of <code>as</code> has a few architecture
specific directives:

     
<a name="index-g_t_0040code_007blow_007d-directive_002c-M32R-1387"></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-1388"></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-1389"></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-1390"></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-1391"></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-M32R2-1392"></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-1393"></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-1394"></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>

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