[llvm-bugs] [Bug 50324] New: wrong code at -Os and above on x86_64-linux-gnu

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=50324

            Bug ID: 50324
           Summary: wrong code at -Os and above 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

It seems to be a recent regression.

[579] % clangtk -v
clang version 13.0.0 (https://github.com/llvm/llvm-project.git
60da33c2d4b2cd744c70259088b2ab89eb858f33)
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
[580] % 
[580] % clangtk -O1 small.c; ./a.out
-1354
[581] % clangtk -Os small.c; ./a.out
32091
[582] % 
[582] % cat small.c
int printf (const char *, ...);
short a(short b, int c) { return b << c; }
int d, e, f, g;
int main() {
  int i = -1476297381;
  for (; d == 0; d = g = -1)
    while (e)
      i = 0;
  f = a(i, g < 0);
  printf("%d\n", f);
  return 0;
}

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