[llvm] r225952 - DAG Combiner: Fold SelectCC When Cond is UNDEF

[Mehdi Amini]

Author: mehdi_amini
Date: Tue Jan 13 23:45:24 2015
New Revision: 225952

URL: http://llvm.org/viewvc/llvm-project?rev=225952&view=rev
Log:
DAG Combiner: Fold SelectCC When Cond is UNDEF

In case folding a node end up with a NaN as operand for the select, 
the folding of the condition of the selectcc node returns "UNDEF".

Differential Revision: http://reviews.llvm.org/D6889


Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=225952&r1=225951&r2=225952&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Tue Jan 13 23:45:24 2015
@@ -5100,13 +5100,16 @@ SDValue DAGCombiner::visitSELECT_CC(SDNo
         return N2;    // cond always true -> true val
       else
         return N3;    // cond always false -> false val
-    }
-
-    // Fold to a simpler select_cc
-    if (SCC.getOpcode() == ISD::SETCC)
+    } else if (SCC->getOpcode() == ISD::UNDEF) {
+      // When the condition is UNDEF, just return the first operand. This is
+      // coherent the DAG creation, no setcc node is created in this case
+      return N2;
+    } else if (SCC.getOpcode() == ISD::SETCC) {
+      // Fold to a simpler select_cc
       return DAG.getNode(ISD::SELECT_CC, SDLoc(N), N2.getValueType(),
                          SCC.getOperand(0), SCC.getOperand(1), N2, N3,
                          SCC.getOperand(2));
+    }
   }
 
   // If we can fold this based on the true/false value, do so.