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Describe loop index split.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52021 91177308-0d34-0410-b5e6-96231b3b80d8
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Devang Patel 2008-06-05 21:44:00 +00:00
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docs/ReleaseNotes.html
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@ -219,7 +219,21 @@ LLVM 2.3 optimizers support a few major enhancements:</p>
<ul>
<li>Loop index set splitting on by default: describe me.</li>
<li>Loop index set splitting on by default.<p>
This transformation hoists conditions from loop bodies and reduces loop's
iteration space to improve performance. For example, <p>
<pre>
for (i = LB; i < UB; ++i)
if (i <= NV)
LOOP_BODY
</pre>
is transformed into
<pre>
NUB = min(NV+1, UB)
for (i = LB; i < NUB; ++i)
LOOP_BODY
</pre>
</li>
<li>LLVM includes a new <tt>memcpy</tt> optimization pass which optimizes out dead
<tt>memcpy</tt> calls, unneeded copies of aggregates, and handles the return slot
optimization. The LLVM optimizer now notices long sequences of consequtive