[Bug middle-end/122610] [13/14/15/16 regression] Load after store incorrectly deleted with -O2 -fno-strict-aliasing while ipa-modref active

[gcc at alanwu dot email via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122610

--- Comment #6 from Alan Wu <gcc at alanwu dot email> ---
On 16, just -O1 is enough to show the issue with code from comment #5. Issue
goes away with -fno-ipa-pure-const. Looks like ipa-pure-const runs before
ipa-modref, and makes the first mistake:

 local analysis of RSTRING_PTR/4
   scanning: D.3009 = rbimpl_rstring_getmem (str_2(D)); [return slot
optimization]
  scanning: _4 = D.3009.as.heap.ptr;
  scanning: return _4;
Function is locally const.

Compiler Explorer: https://godbolt.org/z/YfEToPddh