[PATCH] D147177: [FunctionAttrs] allow weak functions to propagate noreturn

[Johannes Doerfert via Phabricator via llvm-commits]

jdoerfert added a comment.

I don't think this is sound. Refinement again:

  static I = 0;
  __attribute__((weak)) void weak() {
    unspecified_order(++I, UB_if_I_is_non_zero());
  }

Order 1:

  static I = 0;
  __attribute__((weak)) void weak() {
    auto _T1 = ++I;
    auto _T2 = UB_if_I_is_non_zero();
    unspecified_order(_T1, _T2);
    // weak is now noreturn because we hit UB computing _T2.
  }

Order 2:

  static I = 0;
  __attribute__((weak)) void weak() {
    auto _T1 = UB_if_I_is_non_zero();
    auto _T2 = ++I;
    unspecified_order(_T2, _T1);
    // weak is not noreturn and optimizing call sites with it will cause problems if we pick this version.
  }


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D147177/new/

https://reviews.llvm.org/D147177