diff --git a/llvm/include/llvm/CodeGen/SelectionDAG.h b/llvm/include/llvm/CodeGen/SelectionDAG.h
--- a/llvm/include/llvm/CodeGen/SelectionDAG.h
+++ b/llvm/include/llvm/CodeGen/SelectionDAG.h
@@ -2027,9 +2027,9 @@
   ///     X|Cst == X+Cst iff X&Cst = 0.
   bool isBaseWithConstantOffset(SDValue Op) const;
 
-  /// Test whether the given SDValue is known to never be NaN. If \p SNaN is
-  /// true, returns if \p Op is known to never be a signaling NaN (it may still
-  /// be a qNaN).
+  /// Test whether the given SDValue (or all elements of it, if it is a
+  /// vector) is known to never be NaN. If \p SNaN is true, returns if \p Op is
+  /// known to never be a signaling NaN (it may still be a qNaN).
   bool isKnownNeverNaN(SDValue Op, bool SNaN = false, unsigned Depth = 0) const;
 
   /// \returns true if \p Op is known to never be a signaling NaN.
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -4683,7 +4683,6 @@
   if (Depth >= MaxRecursionDepth)
     return false; // Limit search depth.
 
-  // TODO: Handle vectors.
   // If the value is a constant, we can obviously see if it is a NaN or not.
   if (const ConstantFPSDNode *C = dyn_cast<ConstantFPSDNode>(Op)) {
     return !C->getValueAPF().isNaN() ||
@@ -4781,6 +4780,12 @@
   case ISD::EXTRACT_VECTOR_ELT: {
     return isKnownNeverNaN(Op.getOperand(0), SNaN, Depth + 1);
   }
+  case ISD::BUILD_VECTOR: {
+    for (const SDValue &Opnd : Op->ops())
+      if (!isKnownNeverNaN(Opnd, SNaN, Depth + 1))
+        return false;
+    return true;
+  }
   default:
     if (Opcode >= ISD::BUILTIN_OP_END ||
         Opcode == ISD::INTRINSIC_WO_CHAIN ||