[llvm-commits] [llvm] r52021 - /llvm/trunk/docs/ReleaseNotes.html

[Devang Patel]

Author: dpatel
Date: Thu Jun  5 16:44:00 2008
New Revision: 52021

URL: http://llvm.org/viewvc/llvm-project?rev=52021&view=rev
Log:
Describe loop index split.

Modified:
    llvm/trunk/docs/ReleaseNotes.html

Modified: llvm/trunk/docs/ReleaseNotes.html
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/docs/ReleaseNotes.html?rev=52021&r1=52020&r2=52021&view=diff

==============================================================================
--- llvm/trunk/docs/ReleaseNotes.html (original)
+++ llvm/trunk/docs/ReleaseNotes.html Thu Jun  5 16:44:00 2008
@@ -219,7 +219,21 @@
 
 <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