[llvm] [DAGCombiner] Use SmallDenseMap (NFC) (PR #79681)

[Kazu Hirata via llvm-commits]

kazutakahirata wrote:

Thanks.  I've reverted the patch for now: faf555f93f3628b7b2b64162c02dd1474540532e

I guess if we are to use an inline buffer for `SmallDenseMap`, the size of the inline buffer must accommodate the vast majority (90%+?) of the use cases.


https://github.com/llvm/llvm-project/pull/79681