[llvm] [InstrProf] Disambiguate zero bitmaps in text profiles (PR #213906)

[Karim Alweheshy via llvm-commits]

karim-alweheshy wrote:

@ellishg Could you please review this instrumentation proftext grammar fix?

The writer now emits an explicit `$0` for an empty bitmap, while the legacy reader treats only numeric-looking `$...` lines as bitmap metadata so a following Swift `$s...` symbol remains a function name. The reduced regression reproduces the omitted-bitmap boundary, checks the canonical output, and verifies a second import/export is byte-identical. The current head is green across Linux, Linux AArch64, Windows, macOS arm64, formatter, ABI, and libc++ checks.


https://github.com/llvm/llvm-project/pull/213906