Clang can only be used if you set gcc as fallback. I would be suyprised if more than 25% of all arch packages fully compile with clang. I would personally only look into it once the main compiler…
And even if it where the case, i don't think most of the packages should fail to build, and if it fail to build if there no patch available, try to build it with simple lto.
That has also been…
Its probably the best recource for performace focused compiling without placebo out there. GentooLTO has lists for a lot of workarounds too when it comes to LTO, O3, Graphite, and even Ofast. It…
-falign-functions=32 is also used in the offical Intle ClearLinux repos and is recommended on Gentoo to be used alongside LTO. Should boost performance mainly Intel with no regressions on AMD.