[all-commits] [llvm/llvm-project] e6f763: EntryExitInstrumenter: skip available_externally l...

[Fangrui Song via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: e6f76378c20bebec85f66c1574bb6bb928a79025
      https://github.com/llvm/llvm-project/commit/e6f76378c20bebec85f66c1574bb6bb928a79025
  Author: Fangrui Song <i at maskray.me>
  Date:   2025-01-03 (Fri, 03 Jan 2025)

  Changed paths:
    M llvm/lib/Transforms/Utils/EntryExitInstrumenter.cpp
    M llvm/test/Transforms/EntryExitInstrumenter/mcount.ll

  Log Message:
  -----------
  EntryExitInstrumenter: skip available_externally linkage

gnu::always_inline functions, which lower to available_externally, may
not have definitions external to the module. -finstrument-function
family options instrumentating the function (which takes the function
address) may lead to a linker error if the function is not optimized
out, e.g.

```
// -std=c++17 or above with libstdc++
 #include <string>
std::string str;
int main() {}
```

Simplified reproduce:
```
template <typename T>
struct A {
  [[gnu::always_inline]] T bar(T a) { return a * 2; }
};
extern template class A<int>;
int main(int argc, char **argv) {
  return A<int>().bar(argc);
}
```

GCC's -finstrument-function instrumentation skips such functions
(https://gcc.gnu.org/PR78333). Let's skip such functions
(available_externally) as well.

Fix #50742

Pull Request: https://github.com/llvm/llvm-project/pull/121452



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