[all-commits] [llvm/llvm-project] a73baf: [coroutine] Suppress unreachable-code warning on c...

[Haojian Wu via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: a73baf620b8374805b7e927cc79cc157a30e0ac8
      https://github.com/llvm/llvm-project/commit/a73baf620b8374805b7e927cc79cc157a30e0ac8
  Author: Haojian Wu <hokein.wu at gmail.com>
  Date:   2024-02-05 (Mon, 05 Feb 2024)

  Changed paths:
    M clang/lib/Analysis/ReachableCode.cpp
    A clang/test/SemaCXX/coroutine-unreachable-warning.cpp

  Log Message:
  -----------
  [coroutine] Suppress unreachable-code warning on coroutine statements. (#77454)

This fixes #69219.

Consider an example:

```
CoTask my_coroutine() {
    std::abort();
    co_return 1; // unreachable code warning.
}
```

Clang emits a CFG-based unreachable warning on the `co_return` statement
(precisely the `1` subexpr). If we remove this statement, the program
semantic is changed (my_coroutine is not a coroutine anymore).

This patch fixes this issue by never considering coroutine statements as
dead statements.