[compiler-rt] [llvm] [ctxprof] Handle instrumenting functions with `musttail` calls (PR #135121)

[Paul Kirth via llvm-commits]

================
@@ -272,6 +272,8 @@ void setupContext(ContextRoot *Root, GUID Guid, uint32_t NumCounters,
 
 ContextRoot *FunctionData::getOrAllocateContextRoot() {
   auto *Root = CtxRoot;
+  if (mustNotBeRoot(Root))
----------------
ilovepi wrote:

```suggestion
  if (isLegalRoot(Root))
```
Then below you won't need a double negative (`!mustNotBeRoot()`).  Feel free to ignore, just seems easier to parse.

https://github.com/llvm/llvm-project/pull/135121