[llvm-commits] [llvm] r159687 - in /llvm/trunk/lib: Analysis/ValueTracking.cpp VMCore/Instructions.cpp

[Nuno Lopes]

Author: nlopes
Date: Tue Jul  3 16:15:40 2012
New Revision: 159687

URL: http://llvm.org/viewvc/llvm-project?rev=159687&view=rev
Log:
PHINode::hasConstantValue(): return undef if the PHI is fully recursive.
Thanks Duncan for the idea

Modified:
    llvm/trunk/lib/Analysis/ValueTracking.cpp
    llvm/trunk/lib/VMCore/Instructions.cpp

Modified: llvm/trunk/lib/Analysis/ValueTracking.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ValueTracking.cpp?rev=159687&r1=159686&r2=159687&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ValueTracking.cpp (original)
+++ llvm/trunk/lib/Analysis/ValueTracking.cpp Tue Jul  3 16:15:40 2012
@@ -694,7 +694,7 @@
     // taking conservative care to avoid excessive recursion.
     if (Depth < MaxDepth - 1 && !KnownZero && !KnownOne) {
       // Skip if every incoming value references to ourself.
-      if (P->hasConstantValue() == P)
+      if (dyn_cast_or_null<UndefValue>(P->hasConstantValue()))
         break;
 
       KnownZero = APInt::getAllOnesValue(BitWidth);

Modified: llvm/trunk/lib/VMCore/Instructions.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/VMCore/Instructions.cpp?rev=159687&r1=159686&r2=159687&view=diff
==============================================================================
--- llvm/trunk/lib/VMCore/Instructions.cpp (original)
+++ llvm/trunk/lib/VMCore/Instructions.cpp Tue Jul  3 16:15:40 2012
@@ -167,6 +167,8 @@
        // The case where the first value is this PHI.
       ConstantValue = getIncomingValue(i);
     }
+  if (ConstantValue == this)
+    return UndefValue::get(getType());
   return ConstantValue;
 }