http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58625
--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Some builtins are type generic, meaning that you can use just the non-{l,f}
suffixed variant always, but __builtin_signbit isn't among them.
Grep shows that these builtins have "type generic" attribute:
DEF_GCC_BUILTIN (BUILT_IN_FPCLASSIFY, "fpclassify",
BT_FN_INT_INT_INT_INT_INT_INT_VAR, ATTR_CONST_NOTHROW_TYPEGENERIC_LEAF)
DEF_GCC_BUILTIN (BUILT_IN_ISFINITE, "isfinite", BT_FN_INT_VAR,
ATTR_CONST_NOTHROW_TYPEGENERIC_LEAF)
DEF_GCC_BUILTIN (BUILT_IN_ISINF_SIGN, "isinf_sign", BT_FN_INT_VAR,
ATTR_CONST_NOTHROW_TYPEGENERIC_LEAF)
DEF_C99_C90RES_BUILTIN (BUILT_IN_ISINF, "isinf", BT_FN_INT_VAR,
ATTR_CONST_NOTHROW_TYPEGENERIC)
DEF_C99_C90RES_BUILTIN (BUILT_IN_ISNAN, "isnan", BT_FN_INT_VAR,
ATTR_CONST_NOTHROW_TYPEGENERIC_LEAF)
DEF_GCC_BUILTIN (BUILT_IN_ISNORMAL, "isnormal", BT_FN_INT_VAR,
ATTR_CONST_NOTHROW_TYPEGENERIC_LEAF)
DEF_GCC_BUILTIN (BUILT_IN_ISGREATER, "isgreater", BT_FN_INT_VAR,
ATTR_CONST_NOTHROW_TYPEGENERIC_LEAF)
DEF_GCC_BUILTIN (BUILT_IN_ISGREATEREQUAL, "isgreaterequal",
BT_FN_INT_VAR, ATTR_CONST_NOTHROW_TYPEGENERIC_LEAF)
DEF_GCC_BUILTIN (BUILT_IN_ISLESS, "isless", BT_FN_INT_VAR,
ATTR_CONST_NOTHROW_TYPEGENERIC_LEAF)
DEF_GCC_BUILTIN (BUILT_IN_ISLESSEQUAL, "islessequal", BT_FN_INT_VAR,
ATTR_CONST_NOTHROW_TYPEGENERIC_LEAF)
DEF_GCC_BUILTIN (BUILT_IN_ISLESSGREATER, "islessgreater", BT_FN_INT_VAR,
ATTR_CONST_NOTHROW_TYPEGENERIC_LEAF)
DEF_GCC_BUILTIN (BUILT_IN_ISUNORDERED, "isunordered", BT_FN_INT_VAR,
ATTR_CONST_NOTHROW_TYPEGENERIC_LEAF)
