[SelectionDAG] Add an assert in getNode() for EXTRACT_VECTOR_ELT.

When getNode() is called to create an EXTRACT_VECTOR_ELT, assert that
the result VT is at least as wide as the vector element type.

Review: Eli Friedman
llvm-svn: 324061

llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

@@ -4450,6 +4450,10 @@ SDValue SelectionDAG::getNode(unsigned Opcode, const SDLoc &DL, EVT VT,
     break;
   }
   case ISD::EXTRACT_VECTOR_ELT:
+    assert(VT.getSizeInBits() >= N1.getValueType().getScalarSizeInBits() &&
+           "The result of EXTRACT_VECTOR_ELT must be at least as wide as the \
+             element type of the vector.");
+
     // EXTRACT_VECTOR_ELT of an UNDEF is an UNDEF.
     if (N1.isUndef())
       return getUNDEF(VT);