[Bug rtl-optimization/103404] ICE: SIGSEGV in insert_with_costs (cse.c:1569) with custom flags

["rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103404

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Program received signal SIGSEGV, Segmentation fault.
0x00000000028071dc in insert_with_costs (x=0x7ffff6739090, classp=0x0, 
    hash=13, mode=E_SImode, cost=0, reg_cost=1)
    at /home/rguenther/src/gcc3/gcc/cse.c:1569
1569          if (CHEAPER (elt, classp))

where classp is NULL.  The passed in class is

#2  0x00000000028079e7 in merge_equiv_classes (class1=0x40b8700, 
    class2=0x3f0a950) at /home/rguenther/src/gcc3/gcc/cse.c:1756
1756              new_elt = insert (exp, class1, hash, mode);
(gdb) p *class1 
$4 = {exp = 0x7ffff6739090, canon_exp = 0x0, next_same_hash = 0x40b85e0, 
  prev_same_hash = 0x0, next_same_value = 0x0, prev_same_value = 0x0, 
  first_same_value = 0x0, related_value = 0x0, cost = 0, regcost = 1, 
  mode = E_SImode, in_memory = 0 '\000', is_const = 0 '\000', flag = 0 '\000'}

It seems we remove class1 from the table while processing the merge:

#0  remove_from_table (elt=0x40b8700, hash=11)
    at /home/rguenther/src/gcc3/gcc/cse.c:1354
#1  0x0000000002806cc5 in remove_pseudo_from_table (x=0x7ffff6739090, hash=11)
    at /home/rguenther/src/gcc3/gcc/cse.c:1426
#2  0x000000000280792d in merge_equiv_classes (class1=0x40b8700, 
    class2=0x3f0a950) at /home/rguenther/src/gcc3/gcc/cse.c:1747

and note it may even get re-used via the free_element_chain so it might
stay in the table but have a different purpose.  Somebody more familiar
with the equivalence code needs to look at this.  I'd try postponing
remove_pseudo_from_table until after the merge for example.