[llvm-commits] [llvm] r75632 - /llvm/trunk/lib/Analysis/ScalarEvolution.cpp

[Dan Gohman]

Author: djg
Date: Tue Jul 14 09:06:25 2009
New Revision: 75632

URL: http://llvm.org/viewvc/llvm-project?rev=75632&view=rev
Log:
Add a comment about why ScalarEvolution doesn't recognize non-loop PHIs
even when they're obvious.

Modified:
    llvm/trunk/lib/Analysis/ScalarEvolution.cpp

Modified: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ScalarEvolution.cpp?rev=75632&r1=75631&r2=75632&view=diff

==============================================================================
--- llvm/trunk/lib/Analysis/ScalarEvolution.cpp (original)
+++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp Tue Jul 14 09:06:25 2009
@@ -2402,6 +2402,10 @@
         return SymbolicName;
       }
 
+  // It's tempting to recognize PHIs with a unique incoming value, however
+  // this leads passes like indvars to break LCSSA form. Fortunately, such
+  // PHIs are rare, as instcombine zaps them.
+
   // If it's not a loop phi, we can't handle it yet.
   return getUnknown(PN);
 }