[clang][Interp][NFC] Refactor VisitImplicitValueInitExpr

The FIXME comment here is not really correct. Also, handle the case of
non-primitive array element types differently, to reduce indentation.

Author: tbaederr

clang/lib/AST/Interp/ByteCodeExprGen.cpp

@@ -504,19 +504,13 @@ bool ByteCodeExprGen<Emitter>::VisitImplicitValueInitExpr(const ImplicitValueIni
     assert(AT);
     const auto *CAT = cast<ConstantArrayType>(AT);
     size_t NumElems = CAT->getSize().getZExtValue();
+    PrimType ElemT = classifyPrim(CAT->getElementType());
 
-    if (std::optional<PrimType> ElemT = classify(CAT->getElementType())) {
-      // TODO(perf): For int and bool types, we can probably just skip this
-      //   since we memset our Block*s to 0 and so we have the desired value
-      //   without this.
-      for (size_t I = 0; I != NumElems; ++I) {
-        if (!this->visitZeroInitializer(*ElemT, CAT->getElementType(), E))
-          return false;
-        if (!this->emitInitElem(*ElemT, I, E))
-          return false;
-      }
-    } else {
-      assert(false && "default initializer for non-primitive type");
+    for (size_t I = 0; I != NumElems; ++I) {
+      if (!this->visitZeroInitializer(ElemT, CAT->getElementType(), E))
+        return false;
+      if (!this->emitInitElem(ElemT, I, E))
+        return false;
     }
 
     return true;