$ git clone https://sourceware.org/git/glibc.git $ cd glibc $ patch -p1 -i cbrtf-as.patch $ mkdir build $ cd build $ ../configure --prefix=/usr CC="gcc -march=native" $ make -j4 $ make benchthen you can look in the file benchtests/bench.out the entry "cbrtf". Alternatively once you have done make bench you can do ./testrun.sh benchtests/bench-cbrtf.
The license of the files modified by the patch is the common denominator of the license of the CORE-MATH file and the license of the corresponding GNU libc file.