[llvm-bugs] [Bug 25988] New: wrong code at -O2 and -O3 in both 32-bit and 64-bit modes on x86_64-linux-gnu

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=25988

            Bug ID: 25988
           Summary: wrong code at -O2 and -O3 in both 32-bit and 64-bit
                    modes on x86_64-linux-gnu
           Product: new-bugs
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: normal
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: chengniansun at gmail.com
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

The following code is miscompiled by the trunk at -O2 and -O3 in both 32-bit
and 64-bit modes on x86_64-linux-gnu. 

$: clang-trunk -v
clang version 3.8.0 (trunk 256676)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/bin
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.9.3
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/5.2.1
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/5.2.1
Found candidate GCC installation:
/usr/local/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.6.3
Found candidate GCC installation:
/usr/local/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.7.4
Found candidate GCC installation:
/usr/local/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.8.2
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-trunk -w small.c -O3 ; ./a.out
Segmentation fault (core dumped)
$: clang-trunk -w small.c -O2 ; ./a.out
Segmentation fault (core dumped)
$: clang-trunk -w small.c -Os ; ./a.out
$: clang-trunk -w small.c -O3 -m32 ; ./a.out
Segmentation fault (core dumped)
$: clang-trunk -w small.c -O2 -m32 ; ./a.out
Segmentation fault (core dumped)
$: clang-trunk -w small.c -O0 ; ./a.out
$: gcc-4.8 -w small.c ; ./a.out
$: 
$: cat small.c
int a, b, c, d, e;
char f;
void fn1(int);
void fn2() { fn1(a); }

void fn1(p1) {
  char g;
  for (; f;)
    ;
  if (b)
    for (; d;)
      printf("index = [%d][%d][%d]\n", p1, e, d);
  p1 = 0;
  for (; p1 <= 6; p1++) {
    g = 2;
    for (; g <= 6; g++) {
      while (b)
        ;
      if (c)
        fn2();
    }
  }
}

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

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