BAT writeMaps encoded the assumption that functions are only split into two fragments (hot and cold). However, BOLT supports splitting into arbitrary number of fragments. Relax that assumption and look up primary (hot) fragment explicitly. Depends on: https://github.com/llvm/llvm-project/pull/86219 Test Plan: Updated bolt/test/X86/yaml-secondary-entry-discriminator.s Reviewers: ayermolo, rafaelauler, maksfb, dcci Reviewed By: maksfb, dcci Pull Request: https://github.com/llvm/llvm-project/pull/87123