[PATCH] D19760: [AArch64] Turn on "aarch64-ssa-load-store-opt" by default

[Renato Golin via llvm-commits]

This is not just for SPEC. 10% build time regression in an important
benchmark with no performance improvement is a bad thing. The
improvements on the test-suite also show too small a margin to justify
such a big compiler-time regression.

If this was 2012, when Clang was 40~60% faster than GCC, I'd be ok
with the change once you can prove there's a relevant benchmark out
there that benefits immensely. So far, I haven't seen any evidence.

But right now, our compile time for most workloads have gone worse
than GCC, and 10% is a very big deal, especially now that James wants
to see the validity of this pass to other AArch64 cores.

Finally, such a big hit on compile time for a small back-end pass may
be an indication that you're doing something wrong. There may be a
much easier and faster way to do what you want, and I suggest you work
with James to make sure that situation improves.

cheers,
--renato