diff options
Diffstat (limited to 'gcc/doc/install.texi')
| -rw-r--r-- | gcc/doc/install.texi | 29 |
1 files changed, 26 insertions, 3 deletions
diff --git a/gcc/doc/install.texi b/gcc/doc/install.texi index 3dee2bb..9001217 100644 --- a/gcc/doc/install.texi +++ b/gcc/doc/install.texi @@ -2309,9 +2309,10 @@ as a multilib option. If @option{--with-long-double=double} is specified, @samp{double} and @samp{long double} will have the same layout. @item -If the configure option is not set, it defaults to @samp{32} which -is compatible with older versions of the compiler that use non-standard -32-bit types for @samp{double} and @samp{long double}. +The defaults are @option{--with-long-double=64,32} and +@option{--with-double=32,64}. The default @samp{double} layout imposed by +the latter is compatible with older versions of the compiler that implement +@samp{double} as a 32-bit type, which does not comply to the language standard. @end itemize Not all combinations of @option{--with-double=} and @option{--with-long-double=} are valid. For example, the combination @@ -2321,6 +2322,28 @@ multilibs for @samp{double}, whereas the second option implies that @samp{long double} --- and hence also @samp{double} --- is always 32@tie{}bits wide. +@item --with-double-comparison=@{tristate|3|bool|2|libf7@} +Only supported for the AVR target since version@tie{}10. +Specify what result format is returned by library functions that +compare 64-bit floating point values (@code{DFmode}). +The GCC default is @samp{tristate}. If the floating point +implementation returns a boolean instead, set it to @samp{bool}. + +@item --with-libf7=@{libgcc|math|math-symbols|no@} +Only supported for the AVR target since version@tie{}10. +Specify to which degree code from LibF7 is included in libgcc. +LibF7 is an ad-hoc, AVR-specific, 64-bit floating point emulation +written in C and (inline) assembly. @samp{libgcc} adds support +for functions that one would usually expect in libgcc like double addition, +double comparisons and double conversions. @samp{math} also adds routines +that one would expect in @file{libm.a}, but with @code{__} (two underscores) +prepended to the symbol names as specified by @file{math.h}. +@samp{math-symbols} also defines weak aliases for the functions +declared in @file{math.h}. However, @code{--with-libf7} won't +install no @file{math.h} header file whatsoever, this file must come +from elsewhere. This option sets @option{--with-double-comparison} +to @samp{bool}. + @item --with-nds32-lib=@var{library} Specifies that @var{library} setting is used for building @file{libgcc.a}. Currently, the valid @var{library} is @samp{newlib} or @samp{mculib}. |