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    <title>genericAddressSpace</title>
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    <div class="refentry">
      <a id="id-1"></a>
      <div class="titlepage"></div>
      <div xmlns="" class="refnamediv">
        <a xmlns="http://www.w3.org/1999/xhtml" id="genericAddressSpace"></a>
        <h1>generic</h1>
        <p>
            Generic Address Space.
        </p>
      </div>
      <div class="refsect2">
        <a id="synopsis"></a>
        <h3>
        </h3>
        <div class="informaltable">
          <table class="informaltable" border="0">
            <colgroup>
              <col align="left" class="col1" />
            </colgroup>
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                <td align="left">
__generic (unnamed address space)
                        </td>
              </tr>
            </tbody>
          </table>
        </div>
      </div>
      <div class="refsect1">
        <a id="description"></a>
        <h2>Description</h2>
        <p>
            Generic address space (glossary): An address space that include the private, local, and global address
            spaces available to a device. The generic address space supports conversion of pointers to and
            from private, local and global address spaces, and hence lets a programmer write a single
            function that at compile time can take arguments from any of the three named address spaces.
        </p>
      </div>
      <div class="refsect1">
        <a id="notes"></a>
        <h2>Notes</h2>
        <p>
            Programmers often need functions callable from kernels where the pointers manipulated by those
            functions can point to multiple named address spaces. This saves a programmer from the error-
            prone and wasteful practice of creating multiple copies of functions; one for each named address
            space. Therefore the global, local and private address spaces belong to a single 
            <span class="emphasis"><em>generic address space</em></span>. 
            This is closely modeled after the concept of a generic address space used in the embedded
            C standard (ISO/IEC 9899:1999). Since they all belong to a single generic address space, the
            following properties are supported for pointers to named address spaces in device memory:
        </p>
        <p>
            The following rules apply when using pointers that point to the generic address space:
        </p>
        <div class="itemizedlist">
          <ul class="itemizedlist" style="list-style-type: disc; ">
            <li class="listitem">
              <p>
                    A pointer that points to the <code class="function">global</code>, 
                    <code class="function">local</code> or <code class="function">private</code> address space can be 
                    implicitly converted to a pointer to the unnamed 
                    generic address space but not vice-versa.
                </p>
            </li>
            <li class="listitem">
              <p>
                    Pointer casts can be used to cast a pointer that points to the 
                    <code class="function">global</code>, <code class="function">local</code> 
                    or <code class="function">private</code> space to 
                    the unnamed generic addresss space and vice-versa.
                </p>
            </li>
            <li class="listitem">
              <p>
                    A pointer that points to the <code class="function">constant</code> 
                    address space cannot be cast or implicitly 
                    converted to the generic address space.
                </p>
            </li>
          </ul>
        </div>
      </div>
      <div class="refsect2">
        <a id="example1"></a>
        <h3>
            Example
        </h3>
        <p>
            This is the canonical example. In this example, function 
            <code class="function">foo</code>() is declared with an argument that 
            is a pointer with no address space qualifier. 
        </p>
        <div class="informaltable">
          <table class="informaltable" border="0">
            <colgroup>
              <col align="left" class="col1" />
            </colgroup>
            <tbody>
              <tr>
                <td align="left">
void foo(int *a)
{
    *a = *a + 2;
}

kernel void k1(local int *a)
{
    …
    foo(a);
    …
}
kernel void k2(global int *a)
{
    …
    foo(a);
    …
}
                        </td>
              </tr>
            </tbody>
          </table>
        </div>
        <p>
            In the example below, <code class="varname">var</code> is in the unnamed 
            generic address space which gets mapped to the 
            <code class="function">global</code> or <code class="function">local</code> 
            address space depending on the result of the conditional expression.
        </p>
        <div class="informaltable">
          <table class="informaltable" border="0">
            <colgroup>
              <col align="left" class="col1" />
            </colgroup>
            <tbody>
              <tr>
                <td align="left">
kernel void bar(global int *g, local int *l)
{
    int *var;
    if (is_even(get_global_id(0))
        var = g;
    else
        var = l;
    *var = 42;
    …
}
                        </td>
              </tr>
            </tbody>
          </table>
        </div>
        <p>
            The example below is an example with one unnamed 
            generic address space pointer with multiple 
            named address space assignments.
        </p>
        <div class="informaltable">
          <table class="informaltable" border="0">
            <colgroup>
              <col align="left" class="col1" />
            </colgroup>
            <tbody>
              <tr>
                <td align="left">
int *ptr;
global int g;
ptr = &amp;g; // legal

local int l;
ptr = &amp;l; // legal

private int p;
ptr = &amp;p; // legal

constant int c;
ptr = &amp;c; // illegal
                        </td>
              </tr>
            </tbody>
          </table>
        </div>
        <p>
            The example below is an example with one unnamed 
            generic address space pointer being 
            assigned to point to several named address spaces.
        </p>
        <div class="informaltable">
          <table class="informaltable" border="0">
            <colgroup>
              <col align="left" class="col1" />
            </colgroup>
            <tbody>
              <tr>
                <td align="left">
global int * gp;
local int *lp;
private int *pp;

int *p;
p = gp; // legal
p = lp; // legal
p = pp; // legal

// it is illegal to convert from a generic pointer
// to an explicit address space pointer without a cast:
gp = p; // compile-time error
lp = p; // compile-time error
pp = p; // compile-time error
                        </td>
              </tr>
            </tbody>
          </table>
        </div>
      </div>
      <div class="refsect1">
        <a id="specification"></a>
        <h2>Specification</h2>
        <p>
            <img src="pdficon_small1.gif" />

            <a href="https://www.khronos.org/registry/cl/specs/opencl-2.1-openclc.pdf#page=38" target="OpenCL Spec">OpenCL Specification</a>
        </p>
      </div>
      <div class="refsect1">
        <a id="seealso"></a>
        <h2>Also see</h2>
        <p>
            <a class="citerefentry" href="global.html"><span class="citerefentry"><span class="refentrytitle">__global</span></span></a>,
            <a class="citerefentry" href="constant.html"><span class="citerefentry"><span class="refentrytitle">__constant</span></span></a>,
            <a class="citerefentry" href="private.html"><span class="citerefentry"><span class="refentrytitle">__private</span></span></a>,
            <a class="citerefentry" href="qualifiers.html"><span class="citerefentry"><span class="refentrytitle">qualifiers</span></span></a>
        </p>
      </div>
      <div xmlns="" class="refsect3" lang="en" xml:lang="en"><a xmlns="http://www.w3.org/1999/xhtml" id="Copyright"></a><h4 xmlns="http://www.w3.org/1999/xhtml"></h4><img xmlns="http://www.w3.org/1999/xhtml" src="KhronosLogo.jpg" /><p xmlns="http://www.w3.org/1999/xhtml"></p>Copyright © 2007-2015 The Khronos Group Inc.
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"Materials"), to deal in the Materials without restriction, including
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