[llvm] [GlobalMergeFunctions] Add profile-based function filtering (PR #213943)

[Karim Alweheshy via llvm-commits]

karim-alweheshy wrote:

@kyulee Could you please review this profile-policy change for Global Function Merging and CGData?

The policy is hidden and opt-in, `none` preserves the current behavior and CGData format, and the producer and consumer apply the policy independently so stale/unfiltered CGData cannot bypass the current consumer policy. The regression covers local mode, ThinLTO production and consumption, fresh and stale CGData, explicit-hot/profile-hot/executed/zero-count/unprofiled cases, and the same-module mixed hot/cold profitability control. The current head is green across Linux, Linux AArch64, Windows, macOS arm64, formatter, ABI, and libc++ checks.


https://github.com/llvm/llvm-project/pull/213943