[clang] [llvm] [InstrPGO] Instrument sampling profile based cold function (PR #109837)

[Ellis Hoag via cfe-commits]

================
@@ -0,0 +1,24 @@
+; RUN: opt < %s  --passes=pgo-instr-gen -instrument-cold-function-coverage -S  | FileCheck --check-prefixes=COLD %s
+; RUN: opt < %s  --passes=pgo-instr-gen -instrument-cold-function-coverage -cold-function-coverage-max-entry-count=1 -S  | FileCheck --check-prefixes=ENTRY-COUNT %s
+
+; COLD: call void @llvm.instrprof.increment(ptr @__profn_foo, i64  [[#]], i32 1, i32 0)
----------------
ellishg wrote:

Do you plan to support `-instrument-cold-function-coverage` without `-pgo-function-entry-coverage`? If not, I think we should add the flag here so we get the `llvm.instrprof.cover` intrinsic to more closely align with expected behavior.

https://github.com/llvm/llvm-project/pull/109837