[llvm] r212570 - DominanceInfo is strongly preferred over RegionInfo
Tobias Grosser
tobias at grosser.es
Tue Jul 8 15:51:03 PDT 2014
Author: grosser
Date: Tue Jul 8 17:51:03 2014
New Revision: 212570
URL: http://llvm.org/viewvc/llvm-project?rev=212570&view=rev
Log:
DominanceInfo is strongly preferred over RegionInfo
This is and always was strong community consensus. Make this clear in the header
in case newcomers may not be aware.
Modified:
llvm/trunk/include/llvm/Analysis/RegionInfo.h
Modified: llvm/trunk/include/llvm/Analysis/RegionInfo.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/RegionInfo.h?rev=212570&r1=212569&r2=212570&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Analysis/RegionInfo.h (original)
+++ llvm/trunk/include/llvm/Analysis/RegionInfo.h Tue Jul 8 17:51:03 2014
@@ -22,6 +22,16 @@
// itself is not, but in practice runtime seems to be in the order of magnitude
// of dominance tree calculation.
//
+// WARNING: LLVM is generally very concerned about compile time such that
+// the use of additional analysis passes in the default
+// optimization sequence is avoided as much as possible.
+// Specifically, if you do not need the RegionInfo, but dominance
+// information could be sufficient please base your work only on
+// the dominator tree. Most passes maintain it, such that using
+// it has often near zero cost. In contrast RegionInfo is by
+// default not available, is not maintained by existing
+// transformations and there is no intention to do so.
+//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_REGIONINFO_H
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