[llvm] [TableGen] Avoid repeated hash lookups (NFC) (PR #122586)

[Kazu Hirata via llvm-commits]

kazutakahirata wrote:

@mikaelholmen I've reverted one of the two hunks to fix the failure.  Honestly, I don't know how things break here.

@s-barannikov Ack on the flakiness.  Thanks!


https://github.com/llvm/llvm-project/pull/122586