[llvm] [aarch64][win] Add support for import call optimization (equivalent to MSVC /d2ImportCallOptimization) (PR #121516)

[Eli Friedman via llvm-commits]

efriedma-quic wrote:

> The .impcall section can only be filled in when we are writing the COFF object as it requires the actual section numbers, which are only assigned at that point (i.e., they don't exist during asm printing).

You could possibly add a directive specifically to emit section numbers... that would allow you to move more of the logic into the AsmPrinter.  We already have `.secidx`; that's not quite what you want here, but maybe to give you some idea what it would look like.

Not sure if that's worth doing.

https://github.com/llvm/llvm-project/pull/121516