From: Mehdi Amini <mehdi.amini@apple.com>
Date: Wed, 14 Jan 2015 05:45:24 +0000 (+0000)
Subject: DAG Combiner: Fold SelectCC When Cond is UNDEF
X-Git-Url: http://plrg.eecs.uci.edu/git/?p=oota-llvm.git;a=commitdiff_plain;h=cfe92407cd9dfb72bef82f1c16e4b11723e13193

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



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225952 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 3a909b5db31..ee6223b0a3d 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -5100,13 +5100,16 @@ SDValue DAGCombiner::visitSELECT_CC(SDNode *N) {
         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.