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<h4 class="section">MIPS ECOFF object code</h4>



   <p>Assembling for a <small>MIPS</small> <small>ECOFF</small> target supports some additional sections

besides the usual <code>.text</code>, <code>.data</code> and <code>.bss</code>.  The

additional sections are <code>.rdata</code>, used for read-only data,

<code>.sdata</code>, used for small data, and <code>.sbss</code>, used for small

common objects.



   <p>When assembling for <small>ECOFF</small>, the assembler uses the <code>$gp</code> (<code>$28</code>)

register to form the address of a "small object".  Any object in the

<code>.sdata</code> or <code>.sbss</code> sections is considered "small" in this sense. 

For external objects, or for objects in the <code>.bss</code> section, you can use

the <code>gcc</code> <code>-G</code> option to control the size of objects addressed via

<code>$gp</code>; the default value is 8, meaning that a reference to any object

eight bytes or smaller uses <code>$gp</code>.  Passing <code>-G 0</code> to

<code>as</code> prevents it from using the <code>$gp</code> register on the basis

of object size (but the assembler uses <code>$gp</code> for objects in <code>.sdata</code>

or <code>sbss</code> in any case).  The size of an object in the <code>.bss</code> section

is set by the <code>.comm</code> or <code>.lcomm</code> directive that defines it.  The

size of an external object may be set with the <code>.extern</code> directive.  For

example, <code>.extern sym,4</code> declares that the object at <code>sym</code> is 4 bytes

in length, whie leaving <code>sym</code> otherwise undefined.



   <p>Using small <small>ECOFF</small> objects requires linker support, and assumes that the

<code>$gp</code> register is correctly initialized (normally done automatically by

the startup code).  <small>MIPS</small> <small>ECOFF</small> assembly code must not modify the

<code>$gp</code> register.



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