[Bug tree-optimization/114799] New: [14 Regression] ICE: tree check: expected class 'type', have 'exceptional' (error_mark) in useless_type_conversion_p, at gimple-expr.cc:85 with -O2 -fno-tree-forwprop -fvect-cost-model=unlimited

["zsojka at seznam dot cz" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114799

            Bug ID: 114799
           Summary: [14 Regression] ICE: tree check: expected class
                    'type', have 'exceptional' (error_mark) in
                    useless_type_conversion_p, at gimple-expr.cc:85 with
                    -O2 -fno-tree-forwprop -fvect-cost-model=unlimited
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zsojka at seznam dot cz
  Target Milestone: ---
              Host: x86_64-pc-linux-gnu
            Target: x86_64-pc-linux-gnu

Created attachment 58004
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=58004&action=edit
reduced testcase

Compiler output:
$ x86_64-pc-linux-gnu-gcc -O2 -fno-tree-forwprop -fvect-cost-model=unlimited
testcase.c -Wno-psabi
during GIMPLE pass: slp
testcase.c: In function 'foo':
testcase.c:17:1: internal compiler error: tree check: expected class 'type',
have 'exceptional' (error_mark) in useless_type_conversion_p, at
gimple-expr.cc:85
   17 | foo (void)
      | ^~~
0x894e6f tree_class_check_failed(tree_node const*, tree_code_class, char
const*, int, char const*)
        /repo/gcc-trunk/gcc/tree.cc:9006
0x77ef52 tree_class_check(tree_node*, tree_code_class, char const*, int, char
const*)
        /repo/gcc-trunk/gcc/tree.h:3779
0x77ef52 useless_type_conversion_p(tree_node*, tree_node*)
        /repo/gcc-trunk/gcc/gimple-expr.cc:85
0x155c516 verify_gimple_assign_single
        /repo/gcc-trunk/gcc/tree-cfg.cc:4791
0x155c516 verify_gimple_assign
        /repo/gcc-trunk/gcc/tree-cfg.cc:4843
0x155c516 verify_gimple_stmt
        /repo/gcc-trunk/gcc/tree-cfg.cc:5108
0x155fd01 verify_gimple_in_cfg(function*, bool, bool)
        /repo/gcc-trunk/gcc/tree-cfg.cc:5603
0x13ced14 execute_function_todo
        /repo/gcc-trunk/gcc/passes.cc:2089
0x13cf26e execute_todo
        /repo/gcc-trunk/gcc/passes.cc:2143
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.

$ x86_64-pc-linux-gnu-gcc -v
Using built-in specs.
COLLECT_GCC=/repo/gcc-trunk/binary-latest-amd64/bin/x86_64-pc-linux-gnu-gcc
COLLECT_LTO_WRAPPER=/repo/gcc-trunk/binary-trunk-r14-10062-20240422092604-gec78916bb37-checking-yes-rtl-df-extra-nobootstrap-amd64/bin/../libexec/gcc/x86_64-pc-linux-gnu/14.0.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /repo/gcc-trunk//configure --enable-languages=c,c++
--enable-valgrind-annotations --disable-nls --enable-checking=yes,rtl,df,extra
--disable-bootstrap --with-cloog --with-ppl --with-isl
--build=x86_64-pc-linux-gnu --host=x86_64-pc-linux-gnu
--target=x86_64-pc-linux-gnu --with-ld=/usr/bin/x86_64-pc-linux-gnu-ld
--with-as=/usr/bin/x86_64-pc-linux-gnu-as --enable-libsanitizer
--disable-libstdcxx-pch
--prefix=/repo/gcc-trunk//binary-trunk-r14-10062-20240422092604-gec78916bb37-checking-yes-rtl-df-extra-nobootstrap-amd64
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 14.0.1 20240422 (experimental) (GCC)