[llvm-bugs] [Bug 30710] New: wrong code at -O1 and above on x86_64-linux-gnu in both 32-bit and 64-bit modes

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=30710

            Bug ID: 30710
           Summary: wrong code at -O1 and above on x86_64-linux-gnu in
                    both 32-bit and 64-bit modes
           Product: clang
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: su at cs.ucdavis.edu
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

$ clang -v
clang version 4.0.0 (trunk 284302)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/clang-trunk/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7.3
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9.3
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.3.0
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64
$
$ clang -O0 -w small.c; ./a.out
$ clang-3.8 -O1 -w small.c; ./a.out
$
$ clang -O1 -w small.c
$ ./a.out
Illegal instruction (core dumped)
$


-------------------------------------------


static int *b;
int a, **c = &b, **e = &b, *f[2], g = 1;
char d;

void fn1 ()
{ 
  int *i = 0;
  (&b == &f[1]) > a;
  for (; d < 1; d++)
    { 
      *c = &g;
      if (*b)
        return;
    }
  *i = 0;
}

void fn2 ()
{ 
  int k = 0;
  *e = &k;
  fn1 ();
}

int main ()
{ 
  fn2 ();
  return 0;
}

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