Fix comment and unnecessary check for FP build_vectors.

This was copy-paste from the integer version, but
FP build_vectors don't truncate.

llvm-svn: 216928
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 1186683..e556e74 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -711,11 +711,7 @@
     BitVector UndefElements;
     ConstantFPSDNode *CN = BV->getConstantFPSplatNode(&UndefElements);
 
-    // BuildVectors can truncate their operands. Ignore that case here.
-    // FIXME: We blindly ignore splats which include undef which is overly
-    // pessimistic.
-    if (CN && UndefElements.none() &&
-        CN->getValueType(0) == N.getValueType().getScalarType())
+    if (CN && UndefElements.none())
       return CN;
   }