[llvm-bugs] [Bug 50341] New: wrong code at -Os and above on x86_64-linux-gnu

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=50341

            Bug ID: 50341
           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 and might be related to
https://bugs.llvm.org/show_bug.cgi?id=50324.

[618] % clangtk -v
clang version 13.0.0 (https://github.com/llvm/llvm-project.git
4789fc75d3501f14cfbd5b102f173721d498ff58)
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
[619] % 
[619] % clangtk -O1 small.c; ./a.out
-4
[620] % clangtk -Os small.c
[621] % ./a.out
-2
[622] % 
[622] % cat small.c
int printf (const char *, ...);
char a, f;
int b, d;
static int *c = &b;
unsigned char g(unsigned char h, int i) { return h << i; }
void j(int **h) { j(&c); }
int main() {
  *c = 0;
  d = b | -2;
  f = g(d, a == 0);
  printf("%d\n", f);
  return 0;
}

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