Multiplications by constant Integer.MIN_VALUE or Long.MIN_VALUE cause C2 to hang in MulLNode::Ideal()/MulINode::Ideal() when hotspot is compiled with gcc 8.2.1.

The hang itself happens in inlined function:

// Returns largest i such that 2^i <= x.
// If x < 0, the function returns 31 on a 32-bit machine and 63 on a 64-bit machine.
// If x == 0, the function returns -1.
inline int log2_intptr(intptr_t x) {
  int i = -1;
  uintptr_t p = 1;
  while (p != 0 && p <= (uintptr_t)x) {
    // p = 2^(i+1) && p <= x (i.e., 2^(i+1) <= x)
    i++; p *= 2;
  }
  // p = 2^(i+1) && x < p (i.e., 2^i <= x < 2^(i+1))
  // If p = 0, overflow has occurred and i = 31 or i = 63 (depending on the machine word size).
  return i;
}

Looking at the assembly code p != 0 is optimized out.

   0x00007f6494aae685 <+1157>: mov $0xffffffff,%ecx
   0x00007f6494aae68a <+1162>: mov (%rax),%rdi
   0x00007f6494aae68d <+1165>: mov $0x1,%eax
   0x00007f6494aae692 <+1170>: nopw 0x0(%rax,%rax,1)
   0x00007f6494aae698 <+1176>: add %rax,%rax
   0x00007f6494aae69b <+1179>: add $0x1,%ecx
   0x00007f6494aae69e <+1182>: cmp %r14,%rax
   0x00007f6494aae6a1 <+1185>: jbe 0x7f6494aae698 <MulINode::Ideal(PhaseGVN*, bool)+1176>

That call is preceded by:

if( con < 0 ) {
  con = -con;
}

which is undefined behavior for INT_MIN so the compiler is free to assume con != INT_MIN and then optimizing the p != 0 test is legal.