[llvm] [CodeGen] Allow larger number of operands to be compiled by SelectionDAG (PR #122737)

[Nikolay Panchenko via llvm-commits]

npanchen wrote:

> Why not just temporarily add static_assert(sizeof()) checks to keep track of the class sizes?

I thought getting memory usage increase during real compilation is more interesting.
But with your suggestion I see SDNode's size increases by 8 bytes: 88 bytes (w/o changes) vs 96 bytes (w/ changes). That is, right what Craig calculated. 

https://github.com/llvm/llvm-project/pull/122737