JDK-8374582: add opaque node

src/hotspot/share/opto/classes.hpp

@@ -282,6 +282,7 @@ macro(OpaqueLoopStride)
 macro(OpaqueMultiversioning)
 macro(OpaqueZeroTripGuard)
 macro(OpaqueNotNull)
+macro(OpaqueGuard)
 macro(OpaqueInitializedAssertionPredicate)
 macro(OpaqueTemplateAssertionPredicate)
 macro(ProfileBoolean)

src/hotspot/share/opto/loopTransform.cpp

@@ -1235,6 +1235,7 @@ bool IdealLoopTree::policy_range_check(PhaseIdealLoop* phase, bool provisional,
       }
       if (!bol->is_Bool()) {
         assert(bol->is_OpaqueNotNull() ||
+               bol->is_OpaqueGuard() ||
                bol->is_OpaqueTemplateAssertionPredicate() ||
                bol->is_OpaqueInitializedAssertionPredicate() ||
                bol->is_OpaqueMultiversioning(),

src/hotspot/share/opto/loopopts.cpp

@@ -1705,6 +1705,7 @@ void PhaseIdealLoop::try_sink_out_of_loop(Node* n) {
       !n->is_MergeMem() &&
       !n->is_CMove() &&
       !n->is_OpaqueNotNull() &&
+      !n->is_OpaqueGuard() &&
       !n->is_OpaqueInitializedAssertionPredicate() &&
       !n->is_OpaqueTemplateAssertionPredicate() &&
       !is_raw_to_oop_cast && // don't extend live ranges of raw oops
@@ -2228,7 +2229,7 @@ void PhaseIdealLoop::clone_loop_handle_data_uses(Node* old, Node_List &old_new,
       // split if to break.
       assert(!use->is_OpaqueTemplateAssertionPredicate(),
              "should not clone a Template Assertion Predicate which should be removed once it's useless");
-      if (use->is_If() || use->is_CMove() || use->is_OpaqueNotNull() || use->is_OpaqueInitializedAssertionPredicate() ||
+      if (use->is_If() || use->is_CMove() || use->is_OpaqueGuard() || use->is_OpaqueNotNull() || use->is_OpaqueInitializedAssertionPredicate() ||
           (use->Opcode() == Op_AllocateArray && use->in(AllocateNode::ValidLengthTest) == old)) {
         // Since this code is highly unlikely, we lazily build the worklist
         // of such Nodes to go split.

src/hotspot/share/opto/macro.cpp

@@ -2501,6 +2501,7 @@ void PhaseMacroExpand::eliminate_macro_nodes() {
                n->Opcode() == Op_ModD ||
                n->Opcode() == Op_ModF ||
                n->is_OpaqueNotNull()       ||
+               n->is_OpaqueGuard()         ||
                n->is_OpaqueInitializedAssertionPredicate() ||
                n->Opcode() == Op_MaxL      ||
                n->Opcode() == Op_MinL      ||
@@ -2556,6 +2557,17 @@ void PhaseMacroExpand::eliminate_opaque_looplimit_macro_nodes() {
         _igvn.replace_node(n, n->in(1));
 #else
         _igvn.replace_node(n, _igvn.intcon(1));
+#endif
+        success = true;
+      } else if (n->is_OpaqueGuard()) {
+        // Tests with OpaqueGuard nodes are implicitly known to be true or false. Replace the node with appropriate value. In debug builds,
+        // we leave the test in the graph to have an additional sanity check at runtime. If the test fails (i.e. a bug),
+        // we will execute a Halt node.
+#ifdef ASSERT
+        _igvn.replace_node(n, n->in(1));
+#else
+        bool is_positive = n->as_OpaqueGuard()->is_positive();
+        _igvn.replace_node(n, _igvn.intcon(is_positive?1:0));
 #endif
         success = true;
       } else if (n->is_OpaqueInitializedAssertionPredicate()) {

src/hotspot/share/opto/node.hpp

@@ -143,6 +143,7 @@ class OpaqueLoopInitNode;
 class OpaqueLoopStrideNode;
 class OpaqueMultiversioningNode;
 class OpaqueNotNullNode;
+class OpaqueGuardNode;
 class OpaqueInitializedAssertionPredicateNode;
 class OpaqueTemplateAssertionPredicateNode;
 class OuterStripMinedLoopNode;
@@ -822,6 +823,7 @@ public:
     DEFINE_CLASS_ID(Move,     Node, 20)
     DEFINE_CLASS_ID(LShift,   Node, 21)
     DEFINE_CLASS_ID(Neg,      Node, 22)
+    DEFINE_CLASS_ID(OpaqueGuard,  Node, 23)
 
     _max_classes  = ClassMask_Neg
   };
@@ -997,6 +999,7 @@ public:
   DEFINE_CLASS_QUERY(NeverBranch)
   DEFINE_CLASS_QUERY(Opaque1)
   DEFINE_CLASS_QUERY(OpaqueNotNull)
+  DEFINE_CLASS_QUERY(OpaqueGuard)
   DEFINE_CLASS_QUERY(OpaqueInitializedAssertionPredicate)
   DEFINE_CLASS_QUERY(OpaqueTemplateAssertionPredicate)
   DEFINE_CLASS_QUERY(OpaqueLoopInit)

src/hotspot/share/opto/opaquenode.cpp

@@ -112,6 +112,10 @@ const Type* OpaqueNotNullNode::Value(PhaseGVN* phase) const {
   return phase->type(in(1));
 }
 
+const Type* OpaqueGuardNode::Value(PhaseGVN* phase) const {
+  return phase->type(in(1));
+}
+
 OpaqueTemplateAssertionPredicateNode::OpaqueTemplateAssertionPredicateNode(BoolNode* bol,  CountedLoopNode* loop_node)
     : Node(nullptr, bol),
       _loop_node(loop_node),

src/hotspot/share/opto/opaquenode.hpp

@@ -148,6 +148,31 @@ class OpaqueNotNullNode : public Node {
   virtual const Type* bottom_type() const { return TypeInt::BOOL; }
 };
 
+// Similar to OpaqueNotNullNode but for guards. Sometimes we know that a size or limit guard is checked
+// (e.g. there is already a guard in the caller) but the compiler cannot prove it. We could in principle avoid
+// adding a guard in the intrinsic but in some cases (e.g. when the input is a constant that breaks the guard
+// and the caller guard is not inlined) the input of the intrinsic can become top and the data path is folded.
+// Similar to OpaqueNotNullNode to ensure that the control path is also properly folded, we insert a
+// OpaqueGuardNode before the If node in the guard. During macro expansion, we replace the OpaqueGuardNode with
+// the corresponding constant (true/false) in product builds such that the actually unneeded guards
+// are folded and do not end up in the emitted code. In debug builds, we keep the actual checks as additional
+// verification code (i.e. removing OpaqueGuardNode and use the BoolNode inputs instead).
+class OpaqueGuardNode : public Node {
+ private:
+    bool _is_positive;
+ public:
+  OpaqueGuardNode(Compile* C, Node* tst, bool is_positive) : Node(nullptr, tst), _is_positive(is_positive) {
+    init_class_id(Class_OpaqueGuard);
+    init_flags(Flag_is_macro);
+    C->add_macro_node(this);
+  }
+
+  virtual int Opcode() const;
+  virtual const Type* Value(PhaseGVN* phase) const;
+  virtual const Type* bottom_type() const { return TypeInt::BOOL; }
+  bool is_positive() const { return _is_positive; }
+};
+
 // This node is used for Template Assertion Predicate BoolNodes. A Template Assertion Predicate is always removed
 // after loop opts and thus is never converted to actual code. In the post loop opts IGVN phase, the
 // OpaqueTemplateAssertionPredicateNode is replaced by true in order to fold the Template Assertion Predicate away.

src/hotspot/share/opto/split_if.cpp

@@ -307,7 +307,7 @@ bool PhaseIdealLoop::clone_cmp_down(Node* n, const Node* blk1, const Node* blk2)
           assert( bol->is_Bool(), "" );
           if (bol->outcnt() == 1) {
             Node* use = bol->unique_out();
-            if (use->is_OpaqueNotNull() || use->is_OpaqueTemplateAssertionPredicate() ||
+            if (use->is_OpaqueNotNull() || use->is_OpaqueGuard() || use->is_OpaqueTemplateAssertionPredicate() ||
                 use->is_OpaqueInitializedAssertionPredicate()) {
               if (use->outcnt() == 1) {
                 Node* iff = use->unique_out();
@@ -331,8 +331,8 @@ bool PhaseIdealLoop::clone_cmp_down(Node* n, const Node* blk1, const Node* blk2)
             // Recursively sink any BoolNode
             for (DUIterator j = bol->outs(); bol->has_out(j); j++) {
               Node* u = bol->out(j);
-              // Uses are either IfNodes, CMoves, OpaqueNotNull, or Opaque*AssertionPredicate
-              if (u->is_OpaqueNotNull() || u->is_OpaqueTemplateAssertionPredicate() ||
+              // Uses are either IfNodes, CMoves, OpaqueNotNull, OpaqueGuard or Opaque*AssertionPredicate
+              if (u->is_OpaqueNotNull() || u->is_OpaqueGuard() || u->is_OpaqueTemplateAssertionPredicate() ||
                   u->is_OpaqueInitializedAssertionPredicate()) {
                 assert(u->in(1) == bol, "bad input");
                 for (DUIterator_Last kmin, k = u->last_outs(kmin); k >= kmin; --k) {