$ gcc -### -march=native /usr/include/stdlib.h
Using built-in specs.
COLLECT_GCC=/usr/x86_64-pc-linux-gnu/gcc-bin/5.4.0/gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-pc-linux-gnu/5.4.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /var/tmp/portage/sys-devel/gcc-5.4.0/work/gcc-5.4.0/configure --host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu --prefix=/usr --bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/5.4.0 --includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/5.4.0/include --datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/5.4.0 --mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/5.4.0/man --infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/5.4.0/info --with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/5.4.0/include/g++-v5 --with-python-dir=/share/gcc-data/x86_64-pc-linux-gnu/5.4.0/python --enable-languages=c,c++,fortran --enable-obsolete --enable-secureplt --disable-werror --with-system-zlib --enable-nls --without-included-gettext --enable-checking=release --with-bugurl=https://bugs.gentoo.org/ --with-pkgversion='Gentoo 5.4.0 p1.0, pie-0.6.5' --enable-libstdcxx-time --enable-shared --enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu --enable-multilib --with-multilib-list=m32,m64 --disable-altivec --disable-fixed-point --enable-targets=all --disable-libgcj --enable-libgomp --disable-libmudflap --disable-libssp --disable-libcilkrts --disable-libmpx --enable-vtable-verify --enable-libvtv --enable-lto --without-isl --enable-libsanitizer
Thread model: posix
gcc version 5.4.0 (Gentoo 5.4.0 p1.0, pie-0.6.5) 
COLLECT_GCC_OPTIONS='-march=native'
 /usr/libexec/gcc/x86_64-pc-linux-gnu/5.4.0/cc1 -quiet /usr/include/stdlib.h "-march=core2" -mmmx -mno-3dnow -msse -msse2 -msse3 -mssse3 -mno-sse4a -mcx16 -msahf -mno-movbe -mno-aes -mno-sha -mno-pclmul -mno-popcnt -mno-abm -mno-lwp -mno-fma -mno-fma4 -mno-xop -mno-bmi -mno-bmi2 -mno-tbm -mno-avx -mno-avx2 -mno-sse4.2 -msse4.1 -mno-lzcnt -mno-rtm -mno-hle -mno-rdrnd -mno-f16c -mno-fsgsbase -mno-rdseed -mno-prfchw -mno-adx -mfxsr -mno-xsave -mno-xsaveopt -mno-avx512f -mno-avx512er -mno-avx512cd -mno-avx512pf -mno-prefetchwt1 -mno-clflushopt -mno-xsavec -mno-xsaves -mno-avx512dq -mno-avx512bw -mno-avx512vl -mno-avx512ifma -mno-avx512vbmi -mno-clwb -mno-pcommit -mno-mwaitx --param "l1-cache-size=32" --param "l1-cache-line-size=64" --param "l2-cache-size=6144" "-mtune=core2" -quiet -dumpbase stdlib.h -auxbase stdlib -o /tmp/ccZY9ZsX.s "--output-pch=/usr/include/stdlib.h.gch"