[llvm-bugs] [Bug 50458] New: wrong code at -O1, -O2 and -O3 on x86_64-linux-gnu

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=50458

            Bug ID: 50458
           Summary: wrong code at -O1, -O2 and -O3 on x86_64-linux-gnu
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: zhendong.su at inf.ethz.ch
                CC: llvm-bugs at lists.llvm.org

[577] % clangtk -v
clang version 13.0.0 (https://github.com/llvm/llvm-project.git
db8af0f21dc9aad4d336754c857c24470afe53e3)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /local/suz-local/opfuzz/bin
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.5.0
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64
[578] % 
[578] % clangtk -O0 small.c; ./a.out
1
1
[579] % clangtk -O1 small.c; ./a.out
1
[580] % 
[580] % cat small.c
int printf (const char *, ...);
int a, b = 1;
void c(int e) {
  for (; a < 2; a++) {
    if (b) {
      printf("%d\n", b);
      goto L;
    }
    for (; e < 1; e++)
    L:;
  }
}
int main() {
  c(0);
  return 0;
}

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