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<h4 class="subsection">21.3.7 PowerPC Embedded</h4>

<p><a name="index-DVC-register-1589"></a><span class="sc">gdb</span> supports using the DVC (Data Value Compare) register to
implement in hardware simple hardware watchpoint conditions of the form:

<pre class="smallexample">     (gdb) watch <var>ADDRESS|VARIABLE</var> \
       if  <var>ADDRESS|VARIABLE</var> == <var>CONSTANT EXPRESSION</var>
</pre>
   <p>The DVC register will be automatically used when <span class="sc">gdb</span> detects
such pattern in a condition expression, and the created watchpoint uses one
debug register (either the <code>exact-watchpoints</code> option is on and the
variable is scalar, or the variable has a length of one byte).  This feature
is available in native <span class="sc">gdb</span> running on a Linux kernel version 2.6.34
or newer.

   <p>When running on PowerPC embedded processors, <span class="sc">gdb</span> automatically uses
ranged hardware watchpoints, unless the <code>exact-watchpoints</code> option is on,
in which case watchpoints using only one debug register are created when
watching variables of scalar types.

   <p>You can create an artificial array to watch an arbitrary memory
region using one of the following commands (see <a href="Expressions.html#Expressions">Expressions</a>):

<pre class="smallexample">     (gdb) watch *((char *) <var>address</var>)@<var>length</var>
     (gdb) watch {char[<var>length</var>]} <var>address</var>
</pre>
   <p>PowerPC embedded processors support masked watchpoints.  See the discussion
about the <code>mask</code> argument in <a href="Set-Watchpoints.html#Set-Watchpoints">Set Watchpoints</a>.

   <p><a name="index-ranged-breakpoint-1590"></a>PowerPC embedded processors support hardware accelerated
<dfn>ranged breakpoints</dfn>.  A ranged breakpoint stops execution of
the inferior whenever it executes an instruction at any address within
the range it specifies.  To set a ranged breakpoint in <span class="sc">gdb</span>,
use the <code>break-range</code> command.

   <p><span class="sc">gdb</span> provides the following PowerPC-specific commands:

     
<a name="index-break_002drange-1591"></a>
<dl><dt><code>break-range </code><var>start-location</var><code>, </code><var>end-location</var><dd>Set a breakpoint for an address range given by
<var>start-location</var> and <var>end-location</var>, which can specify a function name,
a line number, an offset of lines from the current line or from the start
location, or an address of an instruction (see <a href="Specify-Location.html#Specify-Location">Specify Location</a>,
for a list of all the possible ways to specify a <var>location</var>.) 
The breakpoint will stop execution of the inferior whenever it
executes an instruction at any address within the specified range,
(including <var>start-location</var> and <var>end-location</var>.)

     <p><a name="index-set-powerpc-1592"></a><br><dt><code>set powerpc soft-float</code><dt><code>show powerpc soft-float</code><dd>Force <span class="sc">gdb</span> to use (or not use) a software floating point calling
convention.  By default, <span class="sc">gdb</span> selects the calling convention based
on the selected architecture and the provided executable file.

     <br><dt><code>set powerpc vector-abi</code><dt><code>show powerpc vector-abi</code><dd>Force <span class="sc">gdb</span> to use the specified calling convention for vector
arguments and return values.  The valid options are &lsquo;<samp><span class="samp">auto</span></samp>&rsquo;;
&lsquo;<samp><span class="samp">generic</span></samp>&rsquo;, to avoid vector registers even if they are present;
&lsquo;<samp><span class="samp">altivec</span></samp>&rsquo;, to use AltiVec registers; and &lsquo;<samp><span class="samp">spe</span></samp>&rsquo; to use SPE
registers.  By default, <span class="sc">gdb</span> selects the calling convention
based on the selected architecture and the provided executable file.

     <br><dt><code>set powerpc exact-watchpoints</code><dt><code>show powerpc exact-watchpoints</code><dd>Allow <span class="sc">gdb</span> to use only one debug register when watching a variable
of scalar type, thus assuming that the variable is accessed through the
address of its first byte.

   </dl>

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