[llvm] [DLCov 1/5] Add CMake option to enable enhanced line number coverage tracking (PR #107278)

[Stephen Tozer via llvm-commits]

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@@ -475,6 +475,17 @@ enabled sub-projects. Nearly all of these variable names begin with
 **LLVM_ENABLE_BINDINGS**:BOOL
   If disabled, do not try to build the OCaml bindings.
 
+**LLVM_ENABLE_DEBUGLOC_COVERAGE_TRACKING**:STRING
+  Enhances Debugify's ability to detect line number errors by storing extra
+  information inside Instructions, removing false positives from Debugify's
+  results at the cost of performance. Allowed values are `DISABLED` (default),
+  `COVERAGE`, and `COVERAGE_AND_ORIGIN`. `COVERAGE` tracks whether and why a
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SLTozer wrote:

Makes sense - compile time tracker reckons that [currently](http://llvm-compile-time-tracker.com/compare.php?from=9e65dcac660723a06039c7e9b30f305b9b8ca652&to=f3f169f94a0c5e9cf2711438a5d932a8d8520f60&stat=instructions:u) this sits at a slowdown of about 0.05-0.1%, depending on configuration, so I'll put something to that effect in here.

https://github.com/llvm/llvm-project/pull/107278