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Signed-off-by: Bill Schmidt <wschmidt@linux.ibm.com>
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Bill Schmidt 4 years ago
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  1. 64
      Intrinsics_Reference/ch_intro.xml

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Intrinsics_Reference/ch_intro.xml

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xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="section_intro">
<!-- Chapter Title goes here. -->
<title>Introduction to Vector Programming on Power</title>
<title>Introduction to Vector Programming on POWER</title>

<section>
<title>A Brief History</title>
<para>filler</para>
<para>
The history of vector programming on POWER processors begins
with the AIM (Apple, IBM, Motorola) alliance in the 1990s. The
AIM partners developed the Power Vector Media Extension (VMX) to
accelerate multimedia applications, particularly image
processing. VMX is the name still used by IBM for this
instruction set. Freescale (formerly Motorola) used the
trademark "AltiVec," while Apple at one time called it "Velocity
Engine." While VMX remains the most official name, the term
AltiVec is still in common use today. Freescale's AltiVec
Technology Programming Interface Manual (the "AltiVec PIM") is
still available online for reference (see <xref
linkend="VIPR.intro.links" />).
</para>
<para>
The original VMX specification provided for thirty-two 128-bit
vector registers (VRs). Each register can be treated as
containing sixteen 8-bit character values, eight 16-bit short
integer values, four 32-bit integer values, or four 32-bit
single-precision floating-point values (the "VMX data types").
Furthermore, the integer data types have signed, unsigned, and
boolean variants. An extensive set of arithmetic, logical,
comparison, conversion, memory access, and permute class
operations were specified to operate on these registers.
</para>
<para>
The AltiVec PIM documents intrinsic functions to be used by
programmers to access the VMX instruction set. Because similar
operations are provided for all the VMX data types, the PIM
provides for overloaded intrinsics that can operate on different
data types. However, such function overloading is not normally
acceptable in the C programming language, so compilers compliant
with the AltiVec PIM (such as <code>gcc</code> and
<code>clang</code>) were required to add special handling to
their parsers to permit this. The PIM suggested (but did not
mandate) the use of a header file,
<code>&lt;altivec.h&gt;</code>, for implementations that provide
AltiVec intrinsics. This is common practice for all compliant
compilers today.
</para>
<para>
The first chips incorporating the VMX instruction set were
introduced by Freescale in 1999, and used primarly in Apple
desktop computers. IBM's last desktop CPU (the PowerPC 970)
also included AltiVec support, and was used in the Apple
PowerMac G5. IBM initially omitted support for VMX from its
server-class computers, but added support for it in the POWER6
server family.
</para>
<para>
Next talk about VSX introduced for P7. Changes in registers and
types.
</para>
<section>
<title>Little-Endian Linux</title>
<para>
Yes, it caused a lot of problems. See chapter on this.
</para>
</section>
</section>

<section>
@ -30,7 +88,7 @@ xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="section_intro"> @@ -30,7 +88,7 @@ xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="section_intro">
<para>filler</para>
</section>

<section>
<section xml:id="VIPR.intro.links">
<title>Useful Links</title>
<para>filler</para>
</section>

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