https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99708
--- Comment #19 from Jakub Jelinek <jakub at gcc dot gnu.org> --- builddir/gcc/rs6000-builtins.cc: ibm128_float_type_node, builddir/gcc/rs6000-builtins.cc: = build_function_type_list (ibm128_float_type_node, rs6000-builtin.cc: else if (type_node == ibm128_float_type_node) rs6000-builtin.cc: ibm128_float_type_node = long_double_type_node; rs6000-builtin.cc: ibm128_float_type_node = make_node (REAL_TYPE); rs6000-builtin.cc: TYPE_PRECISION (ibm128_float_type_node) = 128; rs6000-builtin.cc: SET_TYPE_MODE (ibm128_float_type_node, IFmode); rs6000-builtin.cc: layout_type (ibm128_float_type_node); rs6000-builtin.cc: t = build_qualified_type (ibm128_float_type_node, TYPE_QUAL_CONST); rs6000-builtin.cc: ptr_ibm128_float_type_node = build_pointer_type (t); rs6000-builtin.cc: lang_hooks.types.register_builtin_type (ibm128_float_type_node, rs6000-builtin.cc: ieee128_float_type_node = long_double_type_node; rs6000-builtin.cc: ieee128_float_type_node = float128_type_node; rs6000-builtin.cc: t = build_qualified_type (ieee128_float_type_node, TYPE_QUAL_CONST); rs6000-builtin.cc: ptr_ieee128_float_type_node = build_pointer_type (t); rs6000-builtin.cc: lang_hooks.types.register_builtin_type (ieee128_float_type_node, rs6000-builtin.cc: ieee128_float_type_node = ibm128_float_type_node = long_double_type_node; rs6000.cc: && ieee128_float_type_node == long_double_type_node) rs6000.cc: && ibm128_float_type_node == long_double_type_node)) rs6000-c.cc: if (ibm128_float_type_node) rs6000-c.cc: if (ieee128_float_type_node) rs6000.h:#define ieee128_float_type_node (rs6000_builtin_types[RS6000_BTI_ieee128_float]) rs6000.h:#define ibm128_float_type_node (rs6000_builtin_types[RS6000_BTI_ibm128_float]) rs6000.h:#define ptr_ieee128_float_type_node (rs6000_builtin_types[RS6000_BTI_ptr_ieee128_float]) rs6000.h:#define ptr_ibm128_float_type_node (rs6000_builtin_types[RS6000_BTI_ptr_ibm128_float]) I'd guess that else ieee128_float_type_node = ibm128_float_type_node = long_double_type_node; is there so that we don't ICE during the builtins creation (we need just ibm128_float_type_node for it though). Looking at other uses: rs6000_type_string does: else if (type_node == ibm128_float_type_node) return "__ibm128"; could add type_node && to it. And it also makes me wonder why there is no ieee128_float_type_node case. Rest of rs6000-builtin.cc is just the setup and could live without else ieee128_float_type_node = ibm128_float_type_node = long_double_type_node; Also, why do we have ptr_*_float_type_node at all when nothing uses those? rs6000.cc will be fine even with *128_float_type_node NULL, long_double_type_node is presumably always non-NULL. rs6000-c.cc is what this PR talks about, so actually needs those to be NULL if not supported (but, we still want to move the __SIZEOF_FLOAT128__ handling next to __float128 macro IMNSHO, if we add also __SIZEOF_IEEE128__ it could stay where __SIZEOF_FLOAT128__ is defined now). And finally the generated rs6000-builtins.cc, it does: tree df_ftype_if_ci = build_function_type_list (double_type_node, ibm128_float_type_node, integer_type_node, NULL_TREE); tree if_ftype_df_df = build_function_type_list (ibm128_float_type_node, double_type_node, double_type_node, NULL_TREE); rs6000_builtin_info[RS6000_BIF_PACK_IF].fntype = if_ftype_df_df; rs6000_builtin_decls[(int)RS6000_BIF_PACK_IF] = t = add_builtin_function ("__builtin_pack_ibm128", if_ftype_df_df, (int)RS6000_BIF_PACK_IF, BUILT_IN_MD, NULL, NULL_TREE); TREE_READONLY (t) = 1; TREE_NOTHROW (t) = 1; rs6000_builtin_info[RS6000_BIF_UNPACK_IF].fntype = df_ftype_if_ci; rs6000_builtin_decls[(int)RS6000_BIF_UNPACK_IF] = t = add_builtin_function ("__builtin_unpack_ibm128", df_ftype_if_ci, (int)RS6000_BIF_UNPACK_IF, BUILT_IN_MD, NULL, NULL_TREE); TREE_READONLY (t) = 1; TREE_NOTHROW (t) = 1; Unfortunately it is a generated file. Dunno what is best for that, not registering the builtins at all if ibm128_float_type_node is NULL, or keep doing what it used to, register those with some other type.