[Bug target/112567] New: [14 regression] ICE in RTL pass: split2: Segmentation fault

[slyfox at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112567

            Bug ID: 112567
           Summary: [14 regression] ICE in  RTL pass: split2: Segmentation
                    fault
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: slyfox at gcc dot gnu.org
  Target Milestone: ---

Noticed ICE when was building linux-6.6.1 with gcc-master at
r14-5529-g7a496b7ce10518

cvise came up with the following trigger:

// $ cat ast_mode.c.c
union { char b[4]; void (*ul)(void); } gu;
int gv;

void writew(...);

void bug(void) {
  struct { char b[2]; } s;

  gu.ul = bug;
  s.b[0] = gu.b[1] | gv;
  writew(s);
}

Crashes as:

$ gcc -O1  -c ast_mode.c.c -o a.o
during RTL pass: split2
ast_mode.c.c: In function 'bug':
ast_mode.c.c:12:1: internal compiler error: Segmentation fault
   12 | }
      | ^
0x103e83f crash_signal
        ../../source/gcc/toplev.cc:316
0xbd5d7b mark_label_nuses
        ../../source/gcc/emit-rtl.cc:3755
0xbd5dcc mark_label_nuses
        ../../source/gcc/emit-rtl.cc:3763
0xbd5dcc mark_label_nuses
        ../../source/gcc/emit-rtl.cc:3763
0xbd5ded mark_label_nuses
        ../../source/gcc/emit-rtl.cc:3766
0xbda6e6 try_split(rtx_def*, rtx_insn*, int)
        ../../source/gcc/emit-rtl.cc:3952
0xf929d7 split_insn
        ../../source/gcc/recog.cc:3383
0xf981c7 split_all_insns()
        ../../source/gcc/recog.cc:3487
0xf98278 execute
        ../../source/gcc/recog.cc:4411

$ gcc/xgcc -Bgcc -v
Reading specs from gcc/specs
COLLECT_GCC=gcc/xgcc
COLLECT_LTO_WRAPPER=gcc/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /home/slyfox/dev/git/gcc/configure --disable-multilib
--disable-bootstrap --disable-lto --disable-libsanitizer --enable-languages=c
CFLAGS='-O1 -g0' CXXFLAGS='-O1 -g0' LDFLAGS='-O1 -g0' : (reconfigured)
/home/slyfox/dev/git/gcc/configure --disable-multilib --disable-bootstrap
--disable-lto --disable-libsanitizer --enable-languages=c CFLAGS='-O1 -g0'
CXXFLAGS='-O1 -g0' LDFLAGS='-O1 -g0'
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 14.0.0 20231116 (experimental) (GCC)