[LLVMbugs] [Bug 20377] New: wrong code at -Os and above on x86_64-linux-gnu

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=20377

            Bug ID: 20377
           Summary: wrong code at -Os 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: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

The current clang trunk miscompiles the following code at -Os and above on
x86_64-linux-gnu in both 32-bit and 64-bit modes.

This is a regression from 3.4.x. 

$ clang-trunk -v
clang version 3.5.0 (trunk 213464)
Target: x86_64-unknown-linux-gnu
Thread model: posix
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.8.1
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/4.6.4
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/4.8.1
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Selected multilib: .;@m64
$ 
$ clang-trunk -O1 small.c; a.out
$ clang-3.4 -Os small.c; a.out
$ 
$ clang-trunk -Os small.c
$ a.out
Aborted (core dumped)
$ 

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

int a, b, c;

int
fn1 (char p)
{
  return p < 0 ? p : p >> 1;
}

int
main ()
{
  char d;
  int e;
  c = (b < 0) + 2;
  d = c - 1;
  e = d * 2;
  a = fn1 (e);

  if (a != 1) 
    __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/20140721/bad6c243/attachment.html>