https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111956
--- Comment #9 from Maciej W. Rozycki <macro at orcam dot me.uk> --- Hmm, the host check for `__frexpieee128' in gcc/ will surely not do what's intended: even if the host is `powerpc*-*-linux*', the target will often be something else and vice versa (libgm2's host is GCC's target). I think there is no way to verify target C library features in gcc/ at `configure' time, because at this point we may not yet have a target compiler. I haven't dealt with such a situation before, but AFAICS people have used GCC_GLIBC_VERSION_GTE_IFELSE to explicitly check for the glibc version required instead. There's a relevant case for TARGET_DEFAULT_LONG_DOUBLE_128 you can use as an example. I'm not sure if such a check is needed though, unless perhaps for sanity, as you only define TARGET_LIBM_PROVIDES_LONG_DOUBLE_IEEE128 if --with-long-double-format=ieee has been explicitly given. Also ISTM you can omit the target check for `powerpc64le-*-linux*' here keeping $with_long_double_format=ieee check only and get support for the relevant `powerpc64-*-linux*' targets too, as -with-long-double-format= will already have verified correct usage. Finally you may or may not have to check for $gcc_cv_target_ldbl128 equal to "yes" too, in case someone has used --without-long-double-128 (I'm not sure what the consequences would be, but it has caught my attention, so please double-check). Overall please refer to someone more familiar with POWER GCC targets as I can only comment based on what I can see in the scripts and my general experience. The best course of action might be submitting the patch to gcc-patches for review, cc-ing RS6000 port maintainers, as the most relevant people may not be reading this bug report.
