[lld] [Coverage][WebAssembly] Discard InstrProf sections if object not live (PR #172023)

[Sam Clegg via llvm-commits]

================
@@ -121,6 +121,8 @@ class ObjFile : public WasmFileBase {
   // Maps input type indices to output type indices
   std::vector<uint32_t> typeMap;
   std::vector<bool> typeIsUsed;
+  // Does object implicitly mark Live
+  bool markImplicitLive = false;
----------------
sbc100 wrote:

I'm already somewhat confused about the existing `markLive` / `isLive` for `InputFile`.  Adding yet another concept of liveness worries me a little.  

When I was investigating this I was struggling to understand the current `markLive` / `isLive` and thinking we need more documentation for them (or better names to avoid confusion with symbol liveness which seems conceptually different).

Can you explain the different between InputFile->isLive and ObjFile->markImplicitLive?   

https://github.com/llvm/llvm-project/pull/172023