compiler: fix computation of Offsetof.

The implied offsets must be taken into account
when the selector involves anonymous fields.

From-SVN: r200098

gcc/go/gofrontend/expressions.cc

@@ -7279,19 +7279,31 @@ Builtin_call_expression::do_numeric_constant_value(Numeric_constant* nc) const
       Field_reference_expression* farg = arg->field_reference_expression();
       if (farg == NULL)
 	return false;
-      Expression* struct_expr = farg->expr();
-      Type* st = struct_expr->type();
-      if (st->struct_type() == NULL)
-	return false;
-      if (st->named_type() != NULL)
-	st->named_type()->convert(this->gogo_);
-      unsigned int offset;
-      if (!st->struct_type()->backend_field_offset(this->gogo_,
-						   farg->field_index(),
-						   &offset))
-	return false;
+      unsigned int total_offset = 0;
+      while (true)
+        {
+          Expression* struct_expr = farg->expr();
+          Type* st = struct_expr->type();
+          if (st->struct_type() == NULL)
+            return false;
+          if (st->named_type() != NULL)
+            st->named_type()->convert(this->gogo_);
+          unsigned int offset;
+          if (!st->struct_type()->backend_field_offset(this->gogo_,
+						       farg->field_index(),
+						       &offset))
+            return false;
+          total_offset += offset;
+          if (farg->implicit() && struct_expr->field_reference_expression() != NULL)
+            {
+              // Go up until we reach the original base.
+              farg = struct_expr->field_reference_expression();
+              continue;
+            }
+          break;
+        }
       nc->set_unsigned_long(Type::lookup_integer_type("uintptr"),
-			    static_cast<unsigned long>(offset));
+			    static_cast<unsigned long>(total_offset));
       return true;
     }
   else if (this->code_ == BUILTIN_REAL || this->code_ == BUILTIN_IMAG)

gcc/go/gofrontend/expressions.h

@@ -1860,6 +1860,15 @@ class Field_reference_expression : public Expression
   field_index() const
   { return this->field_index_; }
 
+  // Return whether this node was implied by an anonymous field.
+  bool
+  implicit() const
+  { return this->implicit_; }
+
+  void
+  set_implicit(bool implicit)
+  { this->implicit_ = implicit; }
+
   // Set the struct expression.  This is used when parsing.
   void
   set_struct_expression(Expression* expr)
@@ -1914,6 +1923,9 @@ class Field_reference_expression : public Expression
   Expression* expr_;
   // The zero-based index of the field we are retrieving.
   unsigned int field_index_;
+  // Whether this node was emitted implicitly for an embedded field,
+  // that is, expr_ is not the expr_ of the original user node.
+  bool implicit_;
   // Whether we have already emitted a fieldtrack call.
   bool called_fieldtrack_;
 };

gcc/go/gofrontend/types.cc

@@ -4532,6 +4532,7 @@ Struct_type::field_reference_depth(Expression* struct_expr,
 	      go_assert(sub != NULL);
 	    }
 	  sub->set_struct_expression(here);
+          sub->set_implicit(true);
 	}
       else if (subdepth > found_depth)
 	delete sub;