[llvm] MC: Store MCRelaxableFragment MCInst out-of-line (PR #147229)

[Alexis Engelke via llvm-commits]

aengelke wrote:

> This will allow re-encoding of Data+Relax+Data+Relax sequences as Frag+Frag.

Yes, this will significantly reduce the number of fragments on x86 due to relaxable jumps. For several other architectures, e.g. AArch64, it will probably have a slightly negative impact.

https://github.com/llvm/llvm-project/pull/147229