src/cpu/x86/vm/x86.ad

rev 10271 : 8147844: new method j.l.Runtime.onSpinWait() and the corresponding x86 hotspot instrinsic
Summary: adds c1 & c2 x86 intrinsics for j.l.Runtime.onSpinWait() that utilize the PAUSE instruction
Reviewed-by: iveresov, kvn, vlivanov
Contributed-by: Ivan Krylov <ivan@azul.com>, Yuri Gaevsky <ygaevsky@azul.com>

*** 1717,1726 ****
--- 1717,1730 ----
        break;
      case Op_StrIndexOfChar:
        if (!(UseSSE > 4))
          ret_value = false;
        break;
+     case Op_OnSpinWait:
+       if (VM_Version::supports_on_spin_wait() == false)
+         ret_value = false;
+       break;
    }
  
    return ret_value;  // Per default match rules are supported.
  }
  
*** 2994,3003 ****
--- 2998,3025 ----
      __ sqrtsd($dst$$XMMRegister, $constantaddress($con));
    %}
    ins_pipe(pipe_slow);
  %}
  
+ instruct onspinwait() %{
+   match(OnSpinWait);
+   ins_cost(200);
+ 
+   format %{
+     $$template
+     if (os::is_MP()) {
+       $$emit$$"pause\t! membar_onspinwait"
+     } else {
+       $$emit$$"MEMBAR-onspinwait ! (empty encoding)"
+     }
+   %}
+   ins_encode %{
+     __ pause();
+   %}
+   ins_pipe(pipe_slow);
+ %}
+ 
  // ====================VECTOR INSTRUCTIONS=====================================
  
  // Load vectors (4 bytes long)
  instruct loadV4(vecS dst, memory mem) %{
    predicate(n->as_LoadVector()->memory_size() == 4);