[llvm-bugs] [Bug 24356] New: wrong code at -O1 and above on x86_64-linux-gnu

[bugzilla-daemon at llvm.org]

https://llvm.org/bugs/show_bug.cgi?id=24356

            Bug ID: 24356
           Summary: wrong code at -O1 and above on x86_64-linux-gnu
           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: llvm-bugs at lists.llvm.org
    Classification: Unclassified

The following code is miscompiled by the current clang trunk on
x86_64-linux-gnu at -O1 and above in both 32-bit and 64-bit modes.

This is a regression from 3.6.x. 

$ clang-trunk -v
clang version 3.8.0 (trunk 243961)
Target: x86_64-unknown-linux-gnu
Thread model: posix
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.9.2
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/5.1.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.7
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/4.8.2
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9.2
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.1.0
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64
$
$ clang-trunk -O0 small.c; ./a.out
$ clang-3.6 -O1 small.c; ./a.out
$
$ clang-trunk -O1 small.c
$ ./a.out
Aborted (core dumped)
$


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


int a;

void
fn1 ()
{ 
  char b = 0;
  for (; b != -2; b--)
    for (a = 0 ; a < 1; a++)
      if ((unsigned int) b > 1)
        return;
}

int
main ()
{ 
  fn1 ();

  if (a != 0)
    __builtin_abort ();

  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/20150805/5cdb06a3/attachment-0001.html>