8003135: HotSpot inlines and hoists the Thread.currentThread().isInterrupted() out of the loop

Summary: Make the load of TLS._osthread._interrupted flag in Thread.isInterrupted(Z)Z intrinsic effectively volatile.
Reviewed-by: kvn, jrose

src/share/vm/opto/library_call.cpp

@@ -2952,14 +2952,23 @@ bool LibraryCallKit::inline_native_isInterrupted() {
 
   // We only go to the fast case code if we pass two guards.
   // Paths which do not pass are accumulated in the slow_region.
+
+  enum {
+    no_int_result_path   = 1, // t == Thread.current() && !TLS._osthread._interrupted
+    no_clear_result_path = 2, // t == Thread.current() &&  TLS._osthread._interrupted && !clear_int
+    slow_result_path     = 3, // slow path: t.isInterrupted(clear_int)
+    PATH_LIMIT
+  };
+
+  // Ensure that it's not possible to move the load of TLS._osthread._interrupted flag
+  // out of the function.
+  insert_mem_bar(Op_MemBarCPUOrder);
+
+  RegionNode* result_rgn = new (C) RegionNode(PATH_LIMIT);
+  PhiNode*    result_val = new (C) PhiNode(result_rgn, TypeInt::BOOL);
+
   RegionNode* slow_region = new (C) RegionNode(1);
   record_for_igvn(slow_region);
-  RegionNode* result_rgn = new (C) RegionNode(1+3); // fast1, fast2, slow
-  PhiNode*    result_val = new (C) PhiNode(result_rgn, TypeInt::BOOL);
-  enum { no_int_result_path   = 1,
-         no_clear_result_path = 2,
-         slow_result_path     = 3
-  };
 
   // (a) Receiving thread must be the current thread.
   Node* rec_thr = argument(0);
@@ -2968,14 +2977,13 @@ bool LibraryCallKit::inline_native_isInterrupted() {
   Node* cmp_thr = _gvn.transform( new (C) CmpPNode(cur_thr, rec_thr) );
   Node* bol_thr = _gvn.transform( new (C) BoolNode(cmp_thr, BoolTest::ne) );
 
-  bool known_current_thread = (_gvn.type(bol_thr) == TypeInt::ZERO);
-  if (!known_current_thread)
-    generate_slow_guard(bol_thr, slow_region);
+  generate_slow_guard(bol_thr, slow_region);
 
   // (b) Interrupt bit on TLS must be false.
   Node* p = basic_plus_adr(top()/*!oop*/, tls_ptr, in_bytes(JavaThread::osthread_offset()));
   Node* osthread = make_load(NULL, p, TypeRawPtr::NOTNULL, T_ADDRESS);
   p = basic_plus_adr(top()/*!oop*/, osthread, in_bytes(OSThread::interrupted_offset()));
+
   // Set the control input on the field _interrupted read to prevent it floating up.
   Node* int_bit = make_load(control(), p, TypeInt::BOOL, T_INT);
   Node* cmp_bit = _gvn.transform( new (C) CmpINode(int_bit, intcon(0)) );
@@ -3020,22 +3028,20 @@ bool LibraryCallKit::inline_native_isInterrupted() {
     Node* slow_val = set_results_for_java_call(slow_call);
     // this->control() comes from set_results_for_java_call
 
-    // If we know that the result of the slow call will be true, tell the optimizer!
-    if (known_current_thread)  slow_val = intcon(1);
-
     Node* fast_io  = slow_call->in(TypeFunc::I_O);
     Node* fast_mem = slow_call->in(TypeFunc::Memory);
+
     // These two phis are pre-filled with copies of of the fast IO and Memory
-    Node* io_phi   = PhiNode::make(result_rgn, fast_io,  Type::ABIO);
-    Node* mem_phi  = PhiNode::make(result_rgn, fast_mem, Type::MEMORY, TypePtr::BOTTOM);
+    PhiNode* result_mem  = PhiNode::make(result_rgn, fast_mem, Type::MEMORY, TypePtr::BOTTOM);
+    PhiNode* result_io   = PhiNode::make(result_rgn, fast_io,  Type::ABIO);
 
     result_rgn->init_req(slow_result_path, control());
-    io_phi    ->init_req(slow_result_path, i_o());
-    mem_phi   ->init_req(slow_result_path, reset_memory());
+    result_io ->init_req(slow_result_path, i_o());
+    result_mem->init_req(slow_result_path, reset_memory());
     result_val->init_req(slow_result_path, slow_val);
 
-    set_all_memory( _gvn.transform(mem_phi) );
-    set_i_o(        _gvn.transform(io_phi) );
+    set_all_memory(_gvn.transform(result_mem));
+    set_i_o(       _gvn.transform(result_io));
   }
 
   C->set_has_split_ifs(true); // Has chance for split-if optimization