[LLVMbugs] [Bug 17503] 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=17503

            Bug ID: 17503
           Summary: wrong code at -Os and above 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: 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 and should be different from 17077 and
17398. 

$ clang-trunk -v
clang version 3.4 (trunk 192089)
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 *, ...);

struct S
{
  int f0:1;
  int:0;
  int f1:1;
} a; 

int b;

void
bar ()
{
  struct S d = { 0, 1 };
  a = d;
  b = d.f0;
}

int
main ()
{
  bar ();
  printf ("%d\n", a.f1);
  return 0;
}

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