[LLVMbugs] [Bug 18102] New: wrong code on x86_64-linux-gnu (affecting trunk and 3.3)

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=18102

            Bug ID: 18102
           Summary: wrong code on x86_64-linux-gnu (affecting trunk and
                    3.3)
           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: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

The following code is miscompiled by the current clang trunk and clang 3.3 on
x86_64-linux-gnu at -Os and -O3 in 64-bit mode (but not 32-bit mode). 

This is a regression from clang 3.2. 

$ clang-trunk -v
clang version 3.5 (trunk 195973)
Target: x86_64-unknown-linux-gnu
Thread model: posix
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.6
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/4.6.3
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6
$ 
$ clang-trunk -O1 small.c; a.out
0
$ clang-trunk -O2 small.c; a.out
0
$ clang-3.2 -Os small.c; a.out
0
$ 
$ clang-trunk -Os small.c; a.out
1
$ clang-3.3 -Os small.c; a.out
1
$ 


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


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

int a, b, c, d, f, g;

struct S0
{
  char f0;
  int f1;
  int f2;
} e, u;

int
fn1 ()
{
  return b;
}

int
fn2 ()
{
  struct S0 j = { 0, 0, 1 };
  e = j;
  if (fn1 () >= 0)
    {
      e.f2 = 0;
      j = u;
    }
  else
    for (;;)
      for (e.f2 = 0; e.f2 < 1;)
    if (d)
      return 0;
  for (; j.f0; j.f0++)
    {
      if (g)
    e.f1 = j.f1;
      f = a || 1 >> c ? 0 >> c : 1;
    }
  return 0;
}

int
main ()
{
  fn2 ();
  printf ("%d\n", e.f2);
  return 0;
}

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