[LLVMbugs] [Bug 17398] New: wrong code at -Os and above on x86_64-linux-gnu (both 32-bit and 64-bit modes)

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=17398

            Bug ID: 17398
           Summary: wrong code at -Os and above on x86_64-linux-gnu (both
                    32-bit and 64-bit modes)
           Product: clang
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: LLVM Codegen
          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 above in both 32-bit and 64-bit modes. 

This is a regression from clang 3.2. 

$ clang-trunk -v
clang version 3.4 (trunk 191609)
Target: x86_64-pc-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
1
$ clang-trunk -Os small.c; a.out
0
$ clang-3.3 -Os small.c; a.out
0
$ clang-3.2 -Os small.c; a.out
1
$


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


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

int a, b, c, h;
volatile int d;
short e; 
char f = 1, *i = &f;

short *
foo (int p)
{
  short *g = &e;
  for (; c < 1; c++)
    {
      d;
      if (p)
    return g;
    }
  return 0;
}

int
main ()
{
  unsigned short j;
  j = -(&h == (int *) foo (1)); 
  if (a - j)
    *i = 0;
  printf ("%d\n", f);
  return 0;
}

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