[llvm] [SelectionDAG] Add space-optimized forms of OPC_EmitNode/OPC_MorphNodeTo (PR #73502)

[Nikita Popov via llvm-commits]

nikic wrote:

Compile-time results: https://llvm-compile-time-tracker.com/compare.php?from=272085f10bfaa33349682a9e4d08c990c159355d&to=552529fe5cfb5f91b29098879b643c1c2c5f0629&stat=instructions:u Basically no impact (the difference in stage2-O0 is probably noise). Though this is a case where instruction:u may not be an accurate metric (e.g. if there is better cache utilization due to decreased table size).

I'm only building X86, so there is not a lot of size difference anyway: https://llvm-compile-time-tracker.com/compare_clang.php?from=272085f10bfaa33349682a9e4d08c990c159355d&to=552529fe5cfb5f91b29098879b643c1c2c5f0629&stat=size-file&sortBy=absolute-difference

https://github.com/llvm/llvm-project/pull/73502