GMP is a performance-sensitive piece of code for many users. To cater to that, it contains a large number of alternative implementations of its core routines, tuned for various processors and taking advantage not only of instructions available, but also pipeline lengths, specific durations of various instructions and prefetching behavior. (See for example /mpn/x86_64 in the tarball.)

Unfortunately, if you just go "./configure --build=${CHOST}" it will run config.guess, which detects the cpu on the machine it is being built on, and compile only the code tuned for the detected machine.

But fortunately, if you further add "--enable-fat" (see [1]) to the configure line, it adds a cpu dispatcher and all of the chip variations into the binary.

I easily get 15% improvements with a fat binary on my i7 Sandy Bridge, and I assume the cpu is similar to the build machine. People with more significantly different chips should see larger benefits. The cost is bumping the library size by about 100K.

Could you please add this to the PKGBUILD?

[1] - https://gmplib.org/manual/Build-Options.html