| <?xml version="1.0" encoding="UTF-8"?> |
| <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN" |
| "http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">[ |
| <!ENTITY addressSpaceQualifiersInc SYSTEM "addressSpaceQualifiersInc.xml"> |
| <!ENTITY qualifierExampleInc SYSTEM "qualifierExampleInc.xml"> |
| ]> |
| |
| <refentry> |
| <refentryinfo> |
| <keywordset> |
| <keyword>__global</keyword> |
| </keywordset> |
| </refentryinfo> |
| |
| <refmeta> |
| <refentrytitle>__global</refentrytitle> |
| |
| <refmiscinfo> |
| <copyright> |
| <year>2007-2013</year> |
| <holder>The Khronos Group Inc. |
| Permission is hereby granted, free of charge, to any person obtaining a |
| copy of this software and/or associated documentation files (the |
| "Materials"), to deal in the Materials without restriction, including |
| without limitation the rights to use, copy, modify, merge, publish, |
| distribute, sublicense, and/or sell copies of the Materials, and to |
| permit persons to whom the Materials are furnished to do so, subject to |
| the condition that this copyright notice and permission notice shall be included |
| in all copies or substantial portions of the Materials.</holder> |
| </copyright> |
| </refmiscinfo> |
| <manvolnum>3</manvolnum> |
| </refmeta> |
| |
| <!-- ================================ SYNOPSIS --> |
| |
| <refnamediv id="__global"> |
| <refname>__global</refname> |
| |
| <refpurpose> |
| Address space qualifier. |
| </refpurpose> |
| </refnamediv> |
| |
| <!-- ALTERNATIVE SYNTAX SYNOPSIS (NON-FUNCTION) --> |
| |
| <refsect2 id="synopsis"> |
| <title> |
| </title> |
| |
| <informaltable frame="none"> |
| <tgroup cols="1" align="left" colsep="0" rowsep="0"> |
| <colspec colname="col1" colnum="1" /> |
| <tbody> |
| <row> |
| <entry> |
| __global |
| global |
| </entry> |
| </row> |
| </tbody> |
| </tgroup> |
| </informaltable> |
| </refsect2> |
| |
| <!-- ================================ DESCRIPTION --> |
| |
| <refsect1 id="description"><title>Description</title> |
| |
| <para> |
| The <function>__global</function> or <function>global</function> address |
| space name is used to refer to memory objects (buffer or image objects) |
| allocated from the global memory pool. |
| </para> |
| |
| <para> |
| A buffer memory object can be declared as a pointer to a scalar, vector |
| or user-defined struct. This allows the kernel to read and/or write any |
| location in the buffer. |
| </para> |
| |
| <para> |
| The actual size of the array memory object is determined when the memory |
| object is allocated via appropriate API calls in the host code. |
| </para> |
| |
| <para> |
| As image objects are always allocated from the global |
| address space, the <function>__global</function> or |
| <function>global</function> qualifier should not be |
| specified for image types. The elements of an image object |
| cannot be directly accessed. Built-in functions to |
| read from and write to an image object are |
| provided. |
| </para> |
| |
| <para> |
| Variables defined at program scope and static |
| variables inside a function can also be declared |
| in the <function>global</function> address space. |
| They can be defined with any valid OpenCL C data type except |
| for those in table 6.3. In particular, such |
| program scope variables may be of any user-defined |
| type, or a pointer to a user-defined type. In |
| the presence of shared virtual memory, these pointers |
| or pointer members should work as expected as |
| long as they are shared virtual memory pointers |
| and the referenced storage has been mapped appropriately. |
| These variables in the <function>global</function> |
| address space have the same lifetime as the program, |
| and their values persist between calls to |
| any of the kernels in the program. These variables |
| are not shared across devices. They have |
| distinct storage. |
| </para> |
| |
| <para> |
| Program scope and static variables in the |
| <function>global</function> address space may be initialized, but only |
| with constant expressions. |
| </para> |
| |
| <para> |
| The <code>const</code> qualifier can also be used |
| with the <function>__global</function> qualifier to |
| specify a read-only buffer memory object. |
| </para> |
| |
| </refsect1> |
| |
| <!-- ================================ NOTES --> |
| |
| <refsect1 id="notes"><title>Notes</title> |
| |
| &addressSpaceQualifiersInc; |
| |
| </refsect1> |
| |
| <!-- ================================ EXAMPLE --> |
| |
| <refsect2 id="example1"> |
| <title> |
| Examples |
| </title> |
| |
| &qualifierExampleInc; |
| |
| <informaltable frame="none"> |
| <tgroup cols="1" align="left" colsep="0" rowsep="0"> |
| <colspec colname="col1" colnum="1" /> |
| <tbody> |
| <row> |
| <entry> |
| global float4 *color; // An array of float4 elements |
| typedef struct { |
| float a[3]; |
| int b[2]; |
| } foo_t; |
| global foo_t *my_info; // An array of foo_t elements. |
| </entry> |
| </row> |
| </tbody> |
| </tgroup> |
| </informaltable> |
| |
| <para> |
| </para> |
| |
| <informaltable frame="none"> |
| <tgroup cols="1" align="left" colsep="0" rowsep="0"> |
| <colspec colname="col1" colnum="1" /> |
| <tbody> |
| <row> |
| <entry> |
| global int foo; // OK. |
| int foo; // OK. Declared in the global address space |
| global uchar buf[512]; // OK. |
| global int baz = 12; // OK. Initialization is allowed |
| static global int bat; // OK. Internal linkage |
| |
| global uchar bigbuf[CL_DEVICE_MAX_GLOBAL_VARIABLE_SIZE]; // OK. |
| |
| static int foo; // OK. Declared in the global address space |
| static global int foo; // OK. |
| |
| int *foo; // OK. foo is allocated in global address space. |
| // pointer to foo in generic address space |
| |
| void func(...) |
| { |
| int *foo; // OK. foo is allocated in private address space. |
| // foo points to a location in generic address space. |
| ... |
| } |
| |
| global int * global ptr; // OK. |
| int * global ptr; // OK. |
| constant int *global ptr=&baz; // error since baz is in global address |
| // space. |
| global int * constant ptr = &baz; // OK |
| |
| // Pointers work. Also, initialization to a constant known at |
| // program load time |
| global int *global baz_ptr = &baz; |
| |
| global image2d_t im; // Error. Invalid type for program scope |
| // variables |
| |
| global event_t ev; // Error. Invalid type for program scope variables |
| |
| global int *bad_ptr; // Error. No implicit address space |
| </entry> |
| </row> |
| </tbody> |
| </tgroup> |
| </informaltable> |
| </refsect2> |
| |
| <!-- ================================ SPECIFICATION --> |
| <!-- Set the "uri" attribute in the <olink /> element to the "named destination" for the PDF page |
| --> |
| <refsect1 id="specification"><title>Specification</title> |
| <para> |
| <imageobject> |
| <imagedata fileref="pdficon_small1.gif" format="gif" /> |
| </imageobject> |
| |
| <olink uri="addressSpaceQualifiers">OpenCL Specification</olink> |
| </para> |
| </refsect1> |
| |
| <!-- ================================ ALSO SEE --> |
| |
| <refsect1 id="seealso"><title>Also see</title> |
| <para> |
| <citerefentry href="local"><refentrytitle>__local</refentrytitle></citerefentry>, |
| <citerefentry href="constant"><refentrytitle>__constant</refentrytitle></citerefentry>, |
| <citerefentry href="private"><refentrytitle>__private</refentrytitle></citerefentry>, |
| <citerefentry><refentrytitle>qualifiers</refentrytitle></citerefentry> |
| </para> |
| </refsect1> |
| |
| <!-- ============================== COPYRIGHT --> |
| <!-- Content included from copyright.inc.xsl --> |
| |
| <refsect3 id="Copyright"><title></title> |
| <imageobject> |
| <imagedata fileref="KhronosLogo.jpg" format="jpg" /> |
| </imageobject> |
| <para /> |
| </refsect3> |
| |
| <!-- 29-Oct-2015, C lang 2.0 rev 30 --> |
| </refentry> |
| |