Lower the select instruction when the operands are of vector type.

src/IceInst.cpp

Index: src/IceInst.cpp
diff --git a/src/IceInst.cpp b/src/IceInst.cpp
index 004b5550baab037ed52cfab41cad584766990a34..6893856e9e8846d33cb0f3951127fc6b6b7f1a29 100644
--- a/src/IceInst.cpp
+++ b/src/IceInst.cpp
@@ -376,7 +376,7 @@ InstRet::InstRet(Cfg *Func, Operand *RetValue)
 InstSelect::InstSelect(Cfg *Func, Variable *Dest, Operand *Condition,
                        Operand *SourceTrue, Operand *SourceFalse)
     : Inst(Func, Inst::Select, 3, Dest) {
-  assert(Condition->getType() == IceType_i1);
+  assert(typeElementType(Condition->getType()) == IceType_i1);
   addSource(Condition);
   addSource(SourceTrue);
   addSource(SourceFalse);