It appears that an old version of fmaq() is supplied in this package.
Compiling and linking the version from https://fossies.org/linux/gcc/libquadmath/math/fmaq.c which describes itself as Member "gcc-9.3.0/libquadmath/math/fmaq.c" (12 Mar 2020, 9888 Bytes) of package /linux/misc/gcc-9.3.0.tar.xz: resolved the issue for me.
Without doing this some results from fmaq() were 1 bit in error.
It appears that an old version of fmaq() is supplied in this package. Compiling and linking the version from https://fossies.org/linux/gcc/libquadmath/math/fmaq.c which describes itself as Member "gcc-9.3.0/libquadmath/math/fmaq.c" (12 Mar 2020, 9888 Bytes) of package /linux/misc/gcc-9.3.0.tar.xz: resolved the issue for me. Without doing this some results from fmaq() were 1 bit in error.