[all-commits] [llvm/llvm-project] 95b27b: [llvm][ADT] Fix Any with msvc and lto

[Sebastian Neubauer via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 95b27b2a1e0e9fe0781ec76015b4016b9d04423d
      https://github.com/llvm/llvm-project/commit/95b27b2a1e0e9fe0781ec76015b4016b9d04423d
  Author: Sebastian Neubauer <Sebastian.Neubauer at amd.com>
  Date:   2022-12-19 (Mon, 19 Dec 2022)

  Changed paths:
    M llvm/include/llvm/ADT/Any.h

  Log Message:
  -----------
  [llvm][ADT] Fix Any with msvc and lto

llvm::Any had and has several bugs, so we eventually want to replace it
with std::any.

Unfortunately, we cannot do that right now because of bugs in the msvc
standard library that are only fixed in VS 2022 17.4.

When lto is enabled in msvc, constant symbols end up at the same
address, breaking the TypeId implementation of llvm::Any.
Make the TypeId<T>::Id non-const to fix this.

I was able to find an easy reproducer (tried in godbolt with
x64 msvc v19.32 and `/GL` as compiler flags to enable lto):

```c++

template <typename T> struct TypeId {
  // Remove the const here and below to make it work.
  static const char Id;
};

template <typename T> const char TypeId<T>::Id = 0;

template <typename A, typename B>
bool isSame() {
  return &TypeId<A>::Id == &TypeId<B>::Id;
}

class A {};
class B {};

int main() {
  // This should output "is same 0" because the addresses of A's and B's
  // TypeId::Id should be different.
  printf("is same %d\n", isSame<A, B>());
  return 0;
}
```

Differential Revision: https://reviews.llvm.org/D139974