[Bug tree-optimization/109341] New: [13 Regression] ICE in merge, at ipa-modref-tree.cc:176

["vsevolod.livinskiy at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109341

            Bug ID: 109341
           Summary: [13 Regression] ICE in merge, at
                    ipa-modref-tree.cc:176
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vsevolod.livinskiy at gmail dot com
  Target Milestone: ---

Link to the Compiler Explorer: https://godbolt.org/z/9zY57K3Yh

GCC also warns about UB, but I think it is incorrect. The code is well-defined
if "h" is equal to "1".

Reproducer:
unsigned c;
int e, f;
void g(long h, long j[][9]) {
  for (long d = 1; d; d += -(h ?: 600000000000000000)) {
    {
      int a = j[d][d];
      f = h ?: a;
    }
    int i = f;
    {
      int a = c, b = i;
      e = b ?: a;
    }
    c = e;
  }
}

Error:
>$ g++ -O3 -c func.cpp
func.cpp: In function 'void g(long int, long int (*)[9])':
func.cpp:6:18: warning: iteration 7 invokes undefined behavior
[-Waggressive-loop-optimizations]
    6 |       int a = j[d][d];
      |                  ^
func.cpp:4:20: note: within this loop
    4 |   for (long d = 1; d; d += -(h ?: 600000000000000000)) {
      |                    ^
during GIMPLE pass: modref
func.cpp:3:6: internal compiler error: in merge, at ipa-modref-tree.cc:176
    3 | void g(long h, long j[][9]) {
      |      ^
0x84f1a9 modref_access_node::merge(modref_access_node const&, bool)
        /testing/gcc/gcc_src_master/gcc/ipa-modref-tree.cc:176
0x10147cc modref_access_node::try_merge_with(vec<modref_access_node, va_gc,
vl_embed>*&, unsigned long)
        /testing/gcc/gcc_src_master/gcc/ipa-modref-tree.cc:457
0x1016562 modref_access_node::insert(vec<modref_access_node, va_gc,
vl_embed>*&, modref_access_node, unsigned long, bool)
        /testing/gcc/gcc_src_master/gcc/ipa-modref-tree.cc:562
0x101220b modref_ref_node<int>::insert_access(modref_access_node, unsigned
long, bool)
        /testing/gcc/gcc_src_master/gcc/ipa-modref-tree.h:194
0x101220b modref_tree<int>::insert(unsigned int, unsigned int, unsigned int,
int, int, modref_access_node, bool)
        /testing/gcc/gcc_src_master/gcc/ipa-modref-tree.h:444
0x1004eac modref_tree<int>::insert(tree_node*, int, int, modref_access_node
const&, bool)
        /testing/gcc/gcc_src_master/gcc/ipa-modref-tree.h:471
0x1004eac record_access
        /testing/gcc/gcc_src_master/gcc/ipa-modref.cc:1076
0x1005958 analyze_load
        /testing/gcc/gcc_src_master/gcc/ipa-modref.cc:1707
0xf57cb4 walk_stmt_load_store_addr_ops(gimple*, void*, bool (*)(gimple*,
tree_node*, tree_node*, void*), bool (*)(gimple*, tree_node*, tree_node*,
void*), bool (*)(gimple*, tree_node*, tree_node*, void*))
        /testing/gcc/gcc_src_master/gcc/gimple-walk.cc:813
0x100ba01 analyze_stmt
        /testing/gcc/gcc_src_master/gcc/ipa-modref.cc:1788
0x100d1e9 analyze
        /testing/gcc/gcc_src_master/gcc/ipa-modref.cc:1900
0x100d1e9 analyze_function
        /testing/gcc/gcc_src_master/gcc/ipa-modref.cc:3220
0x100ecae execute
        /testing/gcc/gcc_src_master/gcc/ipa-modref.cc:4187

gcc version 13.0.1 20230329 (3be4e43a6a0f429648ea188c8e110b74268fed27)