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

[Paul Kirth via llvm-commits]

ilovepi wrote:

Thanks for looking into reducing binary size. This is something we should probably devote more effort into investigating. 

Overall I think the code changes look reasonable and it’s a nice size improvement. 

I’d make sure at least one other reviewer agrees before landing as I think the approach you’re taking in this stack is a pretty significant departure from the current design. 

It may also be with posting something on discourse to both advertise the contributions as well as to generate interest from other contributors in reducing binary size. 

On a different note if you’re interested in reducing the overall toolchain size e.g. for a distribution you may want to investigate the multi-call library approach used in Fuchsia, as it has greatly reduced the total size of our toolchain distribution. I don’t recall the total savings but @petrhosek may have concrete numbers. 

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