[Bug tree-optimization/89546] [8/9 Regression] Suspected arm flint miscompilation starting with r255510

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89546

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
When get_tail is esra optimized the old way, main is:
  int n1$tail$head$payload;
  struct type D.9885;
  struct tuple D.9880;
  struct type D.9879;
  struct type D.9878;
  struct type D.9875;

  <bb 2> [local count: 1073741825]:
  MEM[(struct tuple *)&D.9885] = 3;
  MEM[(struct tuple *)&D.9885 + 4B] = 2;
  MEM[(struct tuple *)&D.9885 + 8B] = 4;
  D.9875.tail = D.9885;
  D.9885 ={v} {CLOBBER};
  D.9878 = MEM[(const struct tuple &)&D.9875 + 8];
  D.9879.tail = D.9878;
  D.9878 ={v} {CLOBBER};
  D.9880.head = MEM[(const struct type_n &)&D.9879 + 4];
  n1$tail$head$payload_32 = MEM[(struct tuple *)&D.9880];
  D.9880 ={v} {CLOBBER};
  D.9879 ={v} {CLOBBER};
  D.9875 ={v} {CLOBBER};
  if (n1$tail$head$payload_32 != 2)
    goto <bb 3>; [0.00%]
  else
    goto <bb 4>; [99.96%]

  <bb 3> [count: 0]:
  __builtin_abort ();

  <bb 4> [local count: 1072883002]:
  return 0;
and the testcase works.  If it is esra optimized the new way, I get:
  int n1$tail$head$payload;
  struct type n1;

  <bb 2> [local count: 1073741825]:
  MEM[(struct  &)&n1] ={v} {CLOBBER};
  n1$tail$head$payload_90 = MEM[(struct tuple *)&n1 + 4B];
  if (n1$tail$head$payload_90 != 2)
    goto <bb 3>; [0.00%]
  else
    goto <bb 4>; [99.96%]

  <bb 3> [count: 0]:
  __builtin_abort ();

  <bb 4> [local count: 1072883002]:
  n1 ={v} {CLOBBER};
  return 0;
which is undefined, so unless the testcase is UB (but passes e.g. on
x86_64-linux too, valgrind is quiet on it, -fsanitize=address,undefined too),
something went wrong during GIMPLE optimizations.