https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116721

            Bug ID: 116721
           Summary: [15 Regression] ICE: in merge, at
                    ipa-modref-tree.cc:176
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: ipa
          Assignee: unassigned at gcc dot gnu.org
          Reporter: patrick at rivosinc dot com
  Target Milestone: ---

Testcase:
short a, c;
long b;
void d(unsigned short e[][5]) {
  for (long f = 0; f < 1; f += b ?: c ?: -667603842056244355)
    a = 0 == 0 ? e[f][f] : 0;
}


Command/backtrace:
> /scratch/tc-testing/tc-compiler-fuzz-trunk/build-gcv/bin/riscv64-unknown-linux-gnu-gcc
>  -O3  func.c -c -S -o /dev/null
func.c: In function 'd':
func.c:5:19: warning: iteration 3 invokes undefined behavior
[-Waggressive-loop-optimizations]
    5 |     a = 0 == 0 ? e[f][f] : 0;
      |                   ^
func.c:4:22: note: within this loop
    4 |   for (long f = 0; f < 1; f += b ?: c ?: -667603842056244355)
      |                    ~~^~~
during GIMPLE pass: modref
func.c:3:6: internal compiler error: in merge, at ipa-modref-tree.cc:176
    3 | void d(unsigned short e[][5]) {
      |      ^
0x2e376e5 internal_error(char const*, ...)
        ../../../gcc/gcc/diagnostic-global-context.cc:517
0xc52bb0 fancy_abort(char const*, int, char const*)
        ../../../gcc/gcc/diagnostic.cc:1657
0xaae6ad modref_access_node::merge(modref_access_node const&, bool)
        ../../../gcc/gcc/ipa-modref-tree.cc:176
0x10f32d4 modref_access_node::try_merge_with(vec<modref_access_node, va_gc,
vl_embed>*&, unsigned long)
        ../../../gcc/gcc/ipa-modref-tree.cc:457
0x10f513c modref_access_node::insert(vec<modref_access_node, va_gc,
vl_embed>*&, modref_access_node, unsigned long, bool)
        ../../../gcc/gcc/ipa-modref-tree.cc:562
0x10efd83 modref_ref_node<int>::insert_access(modref_access_node, unsigned
long, bool)
        ../../../gcc/gcc/ipa-modref-tree.h:194
0x10efd83 modref_tree<int>::insert(unsigned int, unsigned int, unsigned int,
int, int, modref_access_node, bool)
        ../../../gcc/gcc/ipa-modref-tree.h:444
0x10e2358 modref_tree<int>::insert(tree_node*, int, int, modref_access_node
const&, bool)
        ../../../gcc/gcc/ipa-modref-tree.h:471
0x10e2358 record_access
        ../../../gcc/gcc/ipa-modref.cc:1078
0x10e2ee8 analyze_load
        ../../../gcc/gcc/ipa-modref.cc:1715
0x1027c34 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*))
        ../../../gcc/gcc/gimple-walk.cc:824
0x10e9381 analyze_stmt
        ../../../gcc/gcc/ipa-modref.cc:1796
0x10eabe9 analyze
        ../../../gcc/gcc/ipa-modref.cc:1908
0x10eabe9 analyze_function
        ../../../gcc/gcc/ipa-modref.cc:3233
0x10ec63e execute
        ../../../gcc/gcc/ipa-modref.cc:4254
Please submit a full bug report, with preprocessed source (by using
-freport-bug).
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.

Godbolt: https://godbolt.org/z/coYf1PzEd

Tested with:
riscv64-unknown-linux-gnu-gcc (gb56bd542942) 15.0.0 20240914 (experimental)

Found via fuzzer.

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