[LLVMbugs] [Bug 17077] New: wrong code at -Os and above on x86_64-linux-gnu (affecting trunk and 3.3)

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=17077

            Bug ID: 17077
           Summary: wrong code at -Os and above on x86_64-linux-gnu
                    (affecting trunk and 3.3)
           Product: clang
           Version: unspecified
          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 189735)
$ clang-trunk -O1 small.c
$ a.out
0
$ clang-trunk -Os small.c
$ a.out
1
$ clang-3.3 -Os small.c
$ a.out
1
$ clang-3.2 -Os small.c
$ a.out
0
$ 


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


int printf (const char *, ...);
int a[1], b, c;

int foo (int p)
{
    return p == 0 ? 0 : 1 / p;
}

int main ()
{
  int *d = &b;
  if (foo (d != &a[0]))
    {
      int *e = &c;
      int **f = &d;
      *f = e;
    }
  *d = 1;
  printf ("%d\n", b);
  return 0;
}

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