6.11 Additional Floating Types

As an extension, GNU C supports additional floating types, __float80 and __float128 to support 80-bit (XFmode) and 128-bit (TFmode) floating types. Support for additional types includes the arithmetic operators: add, subtract, multiply, divide; unary arithmetic operators; relational operators; equality operators; and conversions to and from integer and other floating types. Use a suffix ‘w’ or ‘W’ in a literal constant of type __float80 and ‘q’ or ‘Q’ for _float128. You can declare complex types using the corresponding internal complex type, XCmode for __float80 type and TCmode for __float128 type:

typedef _Complex float __attribute__((mode(TC))) _Complex128;
typedef _Complex float __attribute__((mode(XC))) _Complex80;

Not all targets support additional floating-point types. __float80 and __float128 types are supported on x86 and IA-64 targets. The __float128 type is supported on hppa HP-UX targets.