+/* See gdbtypes.h. */
+
+bool
+variant::matches (ULONGEST value, bool is_unsigned) const
+{
+ for (const discriminant_range &range : discriminants)
+ if (range.contains (value, is_unsigned))
+ return true;
+ return false;
+}
+
+static void
+compute_variant_fields_inner (struct type *type,
+ struct property_addr_info *addr_stack,
+ const variant_part &part,
+ std::vector<bool> &flags);
+
+/* A helper function to determine which variant fields will be active.
+ This handles both the variant's direct fields, and any variant
+ parts embedded in this variant. TYPE is the type we're examining.
+ ADDR_STACK holds information about the concrete object. VARIANT is
+ the current variant to be handled. FLAGS is where the results are
+ stored -- this function sets the Nth element in FLAGS if the
+ corresponding field is enabled. ENABLED is whether this variant is
+ enabled or not. */
+
+static void
+compute_variant_fields_recurse (struct type *type,
+ struct property_addr_info *addr_stack,
+ const variant &variant,
+ std::vector<bool> &flags,
+ bool enabled)
+{
+ for (int field = variant.first_field; field < variant.last_field; ++field)
+ flags[field] = enabled;
+
+ for (const variant_part &new_part : variant.parts)
+ {
+ if (enabled)
+ compute_variant_fields_inner (type, addr_stack, new_part, flags);
+ else
+ {
+ for (const auto &sub_variant : new_part.variants)
+ compute_variant_fields_recurse (type, addr_stack, sub_variant,
+ flags, enabled);
+ }
+ }
+}
+
+/* A helper function to determine which variant fields will be active.
+ This evaluates the discriminant, decides which variant (if any) is
+ active, and then updates FLAGS to reflect which fields should be
+ available. TYPE is the type we're examining. ADDR_STACK holds
+ information about the concrete object. VARIANT is the current
+ variant to be handled. FLAGS is where the results are stored --
+ this function sets the Nth element in FLAGS if the corresponding
+ field is enabled. */
+
+static void
+compute_variant_fields_inner (struct type *type,
+ struct property_addr_info *addr_stack,
+ const variant_part &part,
+ std::vector<bool> &flags)
+{
+ /* Evaluate the discriminant. */
+ gdb::optional<ULONGEST> discr_value;
+ if (part.discriminant_index != -1)
+ {
+ int idx = part.discriminant_index;
+
+ if (TYPE_FIELD_LOC_KIND (type, idx) != FIELD_LOC_KIND_BITPOS)
+ error (_("Cannot determine struct field location"
+ " (invalid location kind)"));
+
+ if (addr_stack->valaddr.data () != NULL)
+ discr_value = unpack_field_as_long (type, addr_stack->valaddr.data (),
+ idx);
+ else
+ {
+ CORE_ADDR addr = (addr_stack->addr
+ + (TYPE_FIELD_BITPOS (type, idx)
+ / TARGET_CHAR_BIT));
+
+ LONGEST bitsize = TYPE_FIELD_BITSIZE (type, idx);
+ LONGEST size = bitsize / 8;
+ if (size == 0)
+ size = TYPE_LENGTH (type->field (idx).type ());
+
+ gdb_byte bits[sizeof (ULONGEST)];
+ read_memory (addr, bits, size);
+
+ LONGEST bitpos = (TYPE_FIELD_BITPOS (type, idx)
+ % TARGET_CHAR_BIT);
+
+ discr_value = unpack_bits_as_long (type->field (idx).type (),
+ bits, bitpos, bitsize);
+ }
+ }
+
+ /* Go through each variant and see which applies. */
+ const variant *default_variant = nullptr;
+ const variant *applied_variant = nullptr;
+ for (const auto &variant : part.variants)
+ {
+ if (variant.is_default ())
+ default_variant = &variant;
+ else if (discr_value.has_value ()
+ && variant.matches (*discr_value, part.is_unsigned))
+ {
+ applied_variant = &variant;
+ break;
+ }
+ }
+ if (applied_variant == nullptr)
+ applied_variant = default_variant;
+
+ for (const auto &variant : part.variants)
+ compute_variant_fields_recurse (type, addr_stack, variant,
+ flags, applied_variant == &variant);
+}
+
+/* Determine which variant fields are available in TYPE. The enabled
+ fields are stored in RESOLVED_TYPE. ADDR_STACK holds information
+ about the concrete object. PARTS describes the top-level variant
+ parts for this type. */
+
+static void
+compute_variant_fields (struct type *type,
+ struct type *resolved_type,
+ struct property_addr_info *addr_stack,
+ const gdb::array_view<variant_part> &parts)
+{
+ /* Assume all fields are included by default. */
+ std::vector<bool> flags (resolved_type->num_fields (), true);
+
+ /* Now disable fields based on the variants that control them. */
+ for (const auto &part : parts)
+ compute_variant_fields_inner (type, addr_stack, part, flags);
+
+ resolved_type->set_num_fields
+ (std::count (flags.begin (), flags.end (), true));
+ resolved_type->set_fields
+ ((struct field *)
+ TYPE_ALLOC (resolved_type,
+ resolved_type->num_fields () * sizeof (struct field)));
+
+ int out = 0;
+ for (int i = 0; i < type->num_fields (); ++i)
+ {
+ if (!flags[i])
+ continue;
+
+ resolved_type->field (out) = type->field (i);
+ ++out;
+ }
+}
+