[llvm] RuntimeLibcalls: Add methods to recognize libcall names (PR #149001)

[Nikita Popov via llvm-commits]

nikic wrote:

I've reverted this, as it causes a significant compile-time regression for LTO builds: https://llvm-compile-time-tracker.com/compare.php?from=cf36f49c042f93e4e204ee434173f1c6a6ad4cac&to=45477add8dfe9851605697bd908b49f0ec244625&stat=instructions:u

The libcall check is hot, and the new implementation is much more expensive than the old hash table lookup. You probably need to keep the hash table in some form, even if it's not stored as a static variable.

https://github.com/llvm/llvm-project/pull/149001