8289043: C2: Vector constant materialization attempt

Reviewed-by: goetz

src/hotspot/share/opto/memnode.cpp

@@ -1139,11 +1139,16 @@ Node* MemNode::can_see_stored_value(Node* st, PhaseTransform* phase) const {
       // (This is one of the few places where a generic PhaseTransform
       // can create new nodes.  Think of it as lazily manifesting
       // virtually pre-existing constants.)
-      if (ReduceBulkZeroing || find_array_copy_clone(phase, ld_alloc, in(MemNode::Memory)) == NULL) {
-        // If ReduceBulkZeroing is disabled, we need to check if the allocation does not belong to an
-        // ArrayCopyNode clone. If it does, then we cannot assume zero since the initialization is done
-        // by the ArrayCopyNode.
-        return phase->zerocon(memory_type());
+      if (memory_type() != T_VOID) {
+        if (ReduceBulkZeroing || find_array_copy_clone(phase, ld_alloc, in(MemNode::Memory)) == NULL) {
+          // If ReduceBulkZeroing is disabled, we need to check if the allocation does not belong to an
+          // ArrayCopyNode clone. If it does, then we cannot assume zero since the initialization is done
+          // by the ArrayCopyNode.
+          return phase->zerocon(memory_type());
+        }
+      } else {
+        // TODO: materialize all-zero vector constant
+        assert(!isa_Load() || as_Load()->type()->isa_vect(), "");
       }
     }