[compiler-rt] [tsan] Allow unloading of ignored libraries (PR #105660)

[Vitaly Buka via llvm-commits]

================
@@ -54,20 +54,26 @@ class LibIgnore {
     char *name;
     char *real_name;  // target of symlink
     bool loaded;
+    uptr ignored_code_range_id;
   };
 
   struct LibCodeRange {
----------------
vitalybuka wrote:


Let's hide all atomic stuff in the methods and use release-acquire
```
struct LibCodeRange {
    bool IsInRange(uptr pc) const {
      return (pc >= begin && pc < atomic_load(&end, memory_order_acquire));
    }

    void OnLoad(uptr b, uptr e) {
      begin = b;
      atomic_store(&end, e, memory_order_release);
    }

    void OnUnload() {
      atomic_store(&end, 0, memory_order_release);
    }

  private:
    uptr begin;
    // A value of 0 means the associated module was unloaded.
    atomic_uintptr_t end;
  };
```

https://github.com/llvm/llvm-project/pull/105660