diff options
Diffstat (limited to 'gcc/doc/extend.texi')
| -rw-r--r-- | gcc/doc/extend.texi | 31 |
1 files changed, 26 insertions, 5 deletions
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi index fdb1547ccc8..9f8785eb145 100644 --- a/gcc/doc/extend.texi +++ b/gcc/doc/extend.texi @@ -929,6 +929,7 @@ examine and set these two fictitious variables with your debugger. @cindex additional floating types @cindex @code{__float80} data type @cindex @code{__float128} data type +@cindex @code{__ibm128} data type @cindex @code{w} floating point suffix @cindex @code{q} floating point suffix @cindex @code{W} floating point suffix @@ -941,19 +942,39 @@ 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 @samp{w} or @samp{W} -in a literal constant of type @code{__float80} and @samp{q} or @samp{Q} -for @code{_float128}. You can declare complex types using the -corresponding internal complex type, @code{XCmode} for @code{__float80} -type and @code{TCmode} for @code{__float128} type: +in a literal constant of type @code{__float80} or type +@code{__ibm128}. Use a suffix @samp{q} or @samp{Q} for @code{_float128}. + +On the i386, x86_64, IA-64, and HP-UX targets, you can declare complex +types using the corresponding internal complex type, @code{XCmode} for +@code{__float80} type and @code{TCmode} for @code{__float128} type: @smallexample typedef _Complex float __attribute__((mode(TC))) _Complex128; typedef _Complex float __attribute__((mode(XC))) _Complex80; @end smallexample +On PowerPC Linux, Freebsd and Darwin systems, the default for +@code{long double} is to use the IBM extended floating point format +that uses a pair of @code{double} values to extend the precision. +This means that the mode @code{TCmode} was already used by the +traditional IBM long double format, and you would need to use the mode +@code{KCmode}: + +@smallexample +typedef _Complex float __attribute__((mode(KC))) _Complex128; +@end smallexample + Not all targets support additional floating-point types. @code{__float80} and @code{__float128} types are supported on x86 and IA-64 targets. -The @code{__float128} type is supported on hppa HP-UX targets. +The @code{__float128} type is supported on hppa HP-UX. +The @code{__float128} type is supported on PowerPC systems by default +if the vector scalar instruction set (VSX) is enabled. + +On the PowerPC, @code{__ibm128} provides access to the IBM extended +double format, and it is intended to be used by the library functions +that handle conversions if/when long double is changed to be IEEE +128-bit floating point. @node Half-Precision @section Half-Precision Floating Point |