[LLVMbugs] [Bug 17781] 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=17781

            Bug ID: 17781
           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 on
x86_64-linux-gnu at -Os and above in both 32-bit and 64-bit modes. 

This is a regression from clang 3.3. 

$ clang-trunk -v
clang version 3.4 (trunk 193897)
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
1
$ gcc-4.8.2 -Os small.c; a.out
1
$ icc -Os small.c; a.out
1
$ 


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


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

struct S0
{
  int f0;
  int f1;
  int f2;
  int f3;
  int f4;
} b = {0, 0, 1, 0, 0};

int a;

void
foo (struct S0 p)
{
  b.f2 = 0;
  if (p.f2)
    a = 1;
}

int
main ()
{
  foo (b);
  printf ("%d\n", a);
  return 0;
}

-- 
You are receiving this mail because:
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-bugs/attachments/20131102/0f0b5cb4/attachment.html>