[Bug tree-optimization/111916] New: wrong code at -O1 and above on x86_64-linux-gnu (the generated code hangs)

[zhendong.su at inf dot ethz.ch via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111916

            Bug ID: 111916
           Summary: wrong code at -O1 and above on x86_64-linux-gnu (the
                    generated code hangs)
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zhendong.su at inf dot ethz.ch
  Target Milestone: ---

This appears to be a recent regression.

Compiler Explorer: https://godbolt.org/z/aEEKbdY6E

[563] % gcctk -v
Using built-in specs.
COLLECT_GCC=gcctk
COLLECT_LTO_WRAPPER=/local/suz-local/software/local/gcc-trunk/libexec/gcc/x86_64-pc-linux-gnu/14.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-trunk/configure --disable-bootstrap
--enable-checking=yes --prefix=/local/suz-local/software/local/gcc-trunk
--enable-sanitizers --enable-languages=c,c++ --disable-werror --enable-multilib
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 14.0.0 20231022 (experimental) (GCC) 
[564] % 
[564] % gcctk -O0 small.c; ./a.out
[565] % 
[565] % gcctk -O1 small.c
[566] % timeout -s 9 5 ./a.out
Killed
[567] % 
[567] % cat small.c
#pragma pack(1)
struct A {
  int b : 4;
  int c : 11;
  int d : 2;
  int e : 5;
} f;
int main() {
  struct A g = {1, 1, 1, 1};
  while (!g.b)
    f = g;
  return 0;
}