[Bug c/109934] New: Wrong code at -O3 on x86_64-linux-gnu

["shaohua.li at inf dot ethz.ch" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109934

            Bug ID: 109934
           Summary: Wrong code at -O3 on x86_64-linux-gnu
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: shaohua.li at inf dot ethz.ch
  Target Milestone: ---

For the following code, gcc trunk at -O3 emits wrong code.

Compiler explorer: https://godbolt.org/z/3E8xf69rP

$ cat a.c
int printf(const char *, ...);
short a;
long b = 3, c;
int d(int e) {
  switch (e)
  case 111:
  case 222:
  case 44:
    return 0;
  return e;
}
int main() {
  for (; a >= 0; --a)
    if (d(c + 23) - 23)
      b = 0;
  printf("%d\n", (int)b);
}
$
$ gcc-tk -O0 a.c && ./a.out
3
$ gcc-tk -O3 a.c && ./a.out
0
$
$ gcc-tk -v
Using built-in specs.
COLLECT_GCC=gcc-tk
COLLECT_LTO_WRAPPER=/zdata/shaoli/compilers/ccbuilder-compilers/gcc-c09471fbc7588db2480f036aa56a2403d3c03ae5/libexec/gcc/x86_64-pc-linux-gnu/14.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../configure --disable-multilib --disable-bootstrap
--enable-languages=c,c++
--prefix=/zdata/shaoli/compilers/ccbuilder-compilers/gcc-c09471fbc7588db2480f036aa56a2403d3c03ae5
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 14.0.0 20230521 (experimental) (GCC)
$