[llvm-bugs] [Bug 26046] New: wrong code at -O1 and above on x86_64-linux-gnu

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=26046

            Bug ID: 26046
           Summary: wrong code at -O1 and above on x86_64-linux-gnu
           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

The following code is miscompiled by the current clang trunk at -O1 and above
in both the 32-bit and 64-bit modes on x86_64-linux-gnu.

This is a regression from 3.7.x. 


$ clang-trunk -v
clang version 3.8.0 (trunk 256854)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/tools/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
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 -O0 small.c; ./a.out
6
$ clang-3.7.0 -O1 small.c; ./a.out
6
$ 
$ clang-trunk -O1 small.c; ./a.out
0
$ 


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


int printf (const char *, ...); 

char a, b, g, l, m;
int c, d, e, h, k, p;
static int f;
unsigned char i, *j = &i;

void
fn1 (int *p1)
{
  int *o;
  char n;
  if (d)
    h = p == 1;
  o = &f;
  n = a - 5;
  for (; g > -1; g = n)
    {
      *j = m;
      i = -k | 4;
      e ^= d && *o;
      l = b || (b > (7 >> b)) < c;
      d = *o ^= l;
      *p1 = 6;
      *p1 = *o;
    }
}

int
main ()
{
  fn1 (&f);
  printf ("%d\n", f);
  return 0;
}

-- 
You are receiving this mail because:
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-bugs/attachments/20160106/4247d4a9/attachment.html>