[LLVMbugs] [Bug 18884] New: wrong code at -Os and above on x86_64-linux-gnu in 32-bit mode

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=18884

            Bug ID: 18884
           Summary: wrong code at -Os and above on x86_64-linux-gnu in
                    32-bit mode
           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 at -Os and above
in 32-bit mode (but not 64-bit) on x86_64-linux-gnu. 

This is a regression from 3.4. 

$ clang-trunk -v
clang version 3.5 (trunk 201540)
Target: x86_64-unknown-linux-gnu
Thread model: posix
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.8.1
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.6
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/4.6.4
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/4.8.1
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Candidate multiilb: .;@m64
Candidate multiilb: 32;@m32
Selected multilib: .;@m64
$ 
$ clang-trunk -m32 -O1 small.c; a.out
0
$ clang-trunk -m64 -Os small.c; a.out
0
$ clang-3.4 -m32 -Os small.c; a.out
0
$ 
$ clang-trunk -m32 -Os small.c; a.out
1
$ 


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


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

int a, b, c, h, i, j;

#pragma pack(1)
struct
{
  int:4;
  int f2:23;
  int f3:6;
  int f4:31;
  int f6:11;
} d[5] = {{0, 0, 0, 0}, 
      {0, 0, 0, 0},
      {0, 0, 0, 0}, 
      {0, 0, 0, 0},
      {0, 0, 0, 1}}, 
  e, f, g;

static int
fn1 (int p)
{
  int k;
  for (;;)
    {
      k = e.f2 + d[4].f2;
      f.f3 = k;
      for (; h >= 0; h--)
    for (;;)
      {
        for (; i; i++)
          d[0] = d[4];
        if (c)
          {
        j = a || 1 >> a ? 0 : b;
        g.f3 = j ^ p;
        break;
          }
        return 0;
      }
    }
}

int
main ()
{
  fn1 (0);
  fn1 (1);
  printf ("%d\n", f.f3);
  return 0;
}

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