[LLVMbugs] [Bug 19184] New: LTO crashes with linker error on invalid code at -O1 on x86_64-linux-gnu

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=19184

            Bug ID: 19184
           Summary: LTO crashes with linker error on invalid code at -O1
                    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 following (invalid) code causes a linker error when it is compiled on
x86_64-linux-gnu by the current clang trunk using LTO at -O1 in both 32-bit and
64-bit modes.  

This is a regression from clang 3.4 

Perhaps related to 19079, but it only triggers in 64-bit mode.  

$ clang-trunk -v
clang version 3.5.0 (trunk 204149)
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
$ clang-3.4 -flto -O1 small.c
$ clang-trunk -flto -O0 small.c
$ 
$ clang-trunk -flto -O1 small.c
ld: /tmp/llvm/include/llvm/Support/Casting.h:237: typename cast_retty<X, Y
*>::ret_type llvm::cast(Y *) [X = llvm::PHINode, Y = llvm::Instruction]:
Assertion `isa<X>(Val) && "cast<Ty>() argument of incompatible type!"' failed.
clang: error: unable to execute command: Aborted (core dumped)
clang: error: linker command failed due to signal (use -v to see invocation)
$ 


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


int a, e;

struct
{
  int f1;
  volatile int f2;
  int f3;
} b, c;

int d[1];

int
fn1 (int p)
{
  return p;
}

int
fn2 (int p)
{
  return p ? p : a % p;
}

void fn3 ();

void
fn4 ()
{
  fn3 (d);
}

void
fn3 (int p)
{
  int j, f;
  if (fn1 (p))
    p = 1;
  for (; c.f1; c.f1++)
    {
      if (p)
    f = e > 0;
      e |= 1;
      if (p > 1)
    for (; j; j++)
      b.f3 = fn2 (f);
      b.f2;
    }
}

int
main ()
{
  fn4 ();
  return 0;
}

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