Index: lib/CodeGen/SelectionDAG/SelectionDAG.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -2345,6 +2345,19 @@
     }
     break;
   }
+  case ISD::SCALAR_TO_VECTOR: {
+    // We know about scalar_to_vector as much as we know about it source,
+    // which becomes the first element of otherwise unknown vector.
+    if (DemandedElts != 1)
+      break;
+
+    SDValue N0 = Op.getOperand(0);
+    Known = computeKnownBits(N0, DemandedElts, Depth + 1);
+    if (N0.getValueSizeInBits() != BitWidth)
+      Known = Known.trunc(BitWidth);
+
+    break;
+  }
   case ISD::BITCAST: {
     SDValue N0 = Op.getOperand(0);
     EVT SubVT = N0.getValueType();
Index: test/CodeGen/AMDGPU/load-lo16.ll
===================================================================
--- test/CodeGen/AMDGPU/load-lo16.ll
+++ test/CodeGen/AMDGPU/load-lo16.ll
@@ -305,8 +305,11 @@
 ; GFX9-NEXT: s_waitcnt
 ; GFX9-NEXT: s_setpc_b64
 
-; VI: flat_load_ubyte v{{[0-9]+}}
-; VI: v_or_b32_e32
+; VI: flat_load_ubyte [[LO:v[0-9]+]]
+; VI: v_lshrrev_b32_e32 [[HI:v[0-9]+]], 16, v2
+; VI: s_mov_b32 [[MASK:s[0-9]+]], 0x5040c00
+; VI: v_perm_b32 [[RES:v[0-9]+]], [[HI]], [[LO]], [[MASK]]
+; VI: flat_store_dword v[0:1], [[RES]]
 define void @load_flat_lo_v2i16_reglo_vreg_zexti8(i8* %in, i32 %reg) #0 {
 entry:
   %reg.bc = bitcast i32 %reg to <2 x i16>