8348411: C2: Remove the control input of LoadKlassNode and LoadNKlassNode

Reviewed-by: vlivanov, epeter

Author: Quan Anh Mai

src/hotspot/share/opto/doCall.cpp

@@ -947,7 +947,7 @@ void Parse::catch_inline_exceptions(SafePointNode* ex_map) {
   Node* ex_klass_node = nullptr;
   if (has_exception_handler() && !ex_type->klass_is_exact()) {
     Node* p = basic_plus_adr( ex_node, ex_node, oopDesc::klass_offset_in_bytes());
-    ex_klass_node = _gvn.transform(LoadKlassNode::make(_gvn, nullptr, immutable_memory(), p, TypeInstPtr::KLASS, TypeInstKlassPtr::OBJECT));
+    ex_klass_node = _gvn.transform(LoadKlassNode::make(_gvn, immutable_memory(), p, TypeInstPtr::KLASS, TypeInstKlassPtr::OBJECT));
 
     // Compute the exception klass a little more cleverly.
     // Obvious solution is to simple do a LoadKlass from the 'ex_node'.
@@ -965,7 +965,7 @@ void Parse::catch_inline_exceptions(SafePointNode* ex_map) {
           continue;
         }
         Node* p = basic_plus_adr(ex_in, ex_in, oopDesc::klass_offset_in_bytes());
-        Node* k = _gvn.transform( LoadKlassNode::make(_gvn, nullptr, immutable_memory(), p, TypeInstPtr::KLASS, TypeInstKlassPtr::OBJECT));
+        Node* k = _gvn.transform(LoadKlassNode::make(_gvn, immutable_memory(), p, TypeInstPtr::KLASS, TypeInstKlassPtr::OBJECT));
         ex_klass_node->init_req( i, k );
       }
       ex_klass_node = _gvn.transform(ex_klass_node);

src/hotspot/share/opto/graphKit.cpp

@@ -1200,7 +1200,7 @@ Node* GraphKit::load_object_klass(Node* obj) {
   Node* akls = AllocateNode::Ideal_klass(obj, &_gvn);
   if (akls != nullptr)  return akls;
   Node* k_adr = basic_plus_adr(obj, oopDesc::klass_offset_in_bytes());
-  return _gvn.transform(LoadKlassNode::make(_gvn, nullptr, immutable_memory(), k_adr, TypeInstPtr::KLASS));
+  return _gvn.transform(LoadKlassNode::make(_gvn, immutable_memory(), k_adr, TypeInstPtr::KLASS));
 }
 
 //-------------------------load_array_length-----------------------------------
@@ -2779,7 +2779,7 @@ Node* Phase::gen_subtype_check(Node* subklass, Node* superklass, Node** ctrl, No
   if (might_be_cache && mem != nullptr) {
     kmem = mem->is_MergeMem() ? mem->as_MergeMem()->memory_at(C->get_alias_index(gvn.type(p2)->is_ptr())) : mem;
   }
-  Node *nkls = gvn.transform(LoadKlassNode::make(gvn, nullptr, kmem, p2, gvn.type(p2)->is_ptr(), TypeInstKlassPtr::OBJECT_OR_NULL));
+  Node* nkls = gvn.transform(LoadKlassNode::make(gvn, kmem, p2, gvn.type(p2)->is_ptr(), TypeInstKlassPtr::OBJECT_OR_NULL));
 
   // Compile speed common case: ARE a subtype and we canNOT fail
   if (superklass == nkls) {

src/hotspot/share/opto/library_call.cpp

@@ -3006,7 +3006,7 @@ bool LibraryCallKit::inline_native_classID() {
   IdealKit ideal(this);
 #define __ ideal.
   IdealVariable result(ideal); __ declarations_done();
-  Node* kls = _gvn.transform(LoadKlassNode::make(_gvn, nullptr, immutable_memory(),
+  Node* kls = _gvn.transform(LoadKlassNode::make(_gvn, immutable_memory(),
                                                  basic_plus_adr(cls, java_lang_Class::klass_offset()),
                                                  TypeRawPtr::BOTTOM, TypeInstKlassPtr::OBJECT_OR_NULL));
 
@@ -3036,7 +3036,7 @@ bool LibraryCallKit::inline_native_classID() {
 
     ideal.set(result,  _gvn.transform(new URShiftLNode(kls_trace_id_raw, ideal.ConI(TRACE_ID_SHIFT))));
   } __ else_(); {
-    Node* array_kls = _gvn.transform(LoadKlassNode::make(_gvn, nullptr, immutable_memory(),
+    Node* array_kls = _gvn.transform(LoadKlassNode::make(_gvn, immutable_memory(),
                                                    basic_plus_adr(cls, java_lang_Class::array_klass_offset()),
                                                    TypeRawPtr::BOTTOM, TypeInstKlassPtr::OBJECT_OR_NULL));
     __ if_then(array_kls, BoolTest::ne, null()); {
@@ -3830,7 +3830,7 @@ Node* LibraryCallKit::load_klass_from_mirror_common(Node* mirror,
   if (region == nullptr)  never_see_null = true;
   Node* p = basic_plus_adr(mirror, offset);
   const TypeKlassPtr*  kls_type = TypeInstKlassPtr::OBJECT_OR_NULL;
-  Node* kls = _gvn.transform(LoadKlassNode::make(_gvn, nullptr, immutable_memory(), p, TypeRawPtr::BOTTOM, kls_type));
+  Node* kls = _gvn.transform(LoadKlassNode::make(_gvn, immutable_memory(), p, TypeRawPtr::BOTTOM, kls_type));
   Node* null_ctl = top();
   kls = null_check_oop(kls, &null_ctl, never_see_null);
   if (region != nullptr) {
@@ -4026,7 +4026,7 @@ bool LibraryCallKit::inline_native_Class_query(vmIntrinsics::ID id) {
       phi->add_req(makecon(TypeInstPtr::make(env()->Object_klass()->java_mirror())));
     // If we fall through, it's a plain class.  Get its _super.
     p = basic_plus_adr(kls, in_bytes(Klass::super_offset()));
-    kls = _gvn.transform(LoadKlassNode::make(_gvn, nullptr, immutable_memory(), p, TypeRawPtr::BOTTOM, TypeInstKlassPtr::OBJECT_OR_NULL));
+    kls = _gvn.transform(LoadKlassNode::make(_gvn, immutable_memory(), p, TypeRawPtr::BOTTOM, TypeInstKlassPtr::OBJECT_OR_NULL));
     null_ctl = top();
     kls = null_check_oop(kls, &null_ctl);
     if (null_ctl != top()) {
@@ -4180,7 +4180,7 @@ bool LibraryCallKit::inline_native_subtype_check() {
     args[which_arg] = arg;
 
     Node* p = basic_plus_adr(arg, class_klass_offset);
-    Node* kls = LoadKlassNode::make(_gvn, nullptr, immutable_memory(), p, adr_type, kls_type);
+    Node* kls = LoadKlassNode::make(_gvn, immutable_memory(), p, adr_type, kls_type);
     klasses[which_arg] = _gvn.transform(kls);
   }
 

src/hotspot/share/opto/macro.cpp

@@ -2338,7 +2338,7 @@ void PhaseMacroExpand::expand_subtypecheck_node(SubTypeCheckNode *check) {
       subklass = obj_or_subklass;
     } else {
       Node* k_adr = basic_plus_adr(obj_or_subklass, oopDesc::klass_offset_in_bytes());
-      subklass = _igvn.transform(LoadKlassNode::make(_igvn, nullptr, C->immutable_memory(), k_adr, TypeInstPtr::KLASS));
+      subklass = _igvn.transform(LoadKlassNode::make(_igvn, C->immutable_memory(), k_adr, TypeInstPtr::KLASS));
     }
 
     Node* not_subtype_ctrl = Phase::gen_subtype_check(subklass, superklass, &ctrl, nullptr, _igvn, check->method(), check->bci());

src/hotspot/share/opto/macroArrayCopy.cpp

@@ -642,7 +642,7 @@ Node* PhaseMacroExpand::generate_arraycopy(ArrayCopyNode *ac, AllocateArrayNode*
         // (At this point we can assume disjoint_bases, since types differ.)
         int ek_offset = in_bytes(ObjArrayKlass::element_klass_offset());
         Node* p1 = basic_plus_adr(dest_klass, ek_offset);
-        Node* n1 = LoadKlassNode::make(_igvn, nullptr, C->immutable_memory(), p1, TypeRawPtr::BOTTOM);
+        Node* n1 = LoadKlassNode::make(_igvn, C->immutable_memory(), p1, TypeRawPtr::BOTTOM);
         Node* dest_elem_klass = transform_later(n1);
         Node* cv = generate_checkcast_arraycopy(&local_ctrl, &local_mem,
                                                 adr_type,

src/hotspot/share/opto/memnode.cpp

@@ -2398,32 +2398,26 @@ const Type* LoadSNode::Value(PhaseGVN* phase) const {
 //=============================================================================
 //----------------------------LoadKlassNode::make------------------------------
 // Polymorphic factory method:
-Node* LoadKlassNode::make(PhaseGVN& gvn, Node* ctl, Node* mem, Node* adr, const TypePtr* at, const TypeKlassPtr* tk) {
+Node* LoadKlassNode::make(PhaseGVN& gvn, Node* mem, Node* adr, const TypePtr* at, const TypeKlassPtr* tk) {
   // sanity check the alias category against the created node type
-  const TypePtr *adr_type = adr->bottom_type()->isa_ptr();
+  const TypePtr* adr_type = adr->bottom_type()->isa_ptr();
   assert(adr_type != nullptr, "expecting TypeKlassPtr");
 #ifdef _LP64
   if (adr_type->is_ptr_to_narrowklass()) {
     assert(UseCompressedClassPointers, "no compressed klasses");
-    Node* load_klass = gvn.transform(new LoadNKlassNode(ctl, mem, adr, at, tk->make_narrowklass(), MemNode::unordered));
+    Node* load_klass = gvn.transform(new LoadNKlassNode(mem, adr, at, tk->make_narrowklass(), MemNode::unordered));
     return new DecodeNKlassNode(load_klass, load_klass->bottom_type()->make_ptr());
   }
 #endif
   assert(!adr_type->is_ptr_to_narrowklass() && !adr_type->is_ptr_to_narrowoop(), "should have got back a narrow oop");
-  return new LoadKlassNode(ctl, mem, adr, at, tk, MemNode::unordered);
+  return new LoadKlassNode(mem, adr, at, tk, MemNode::unordered);
 }
 
 //------------------------------Value------------------------------------------
 const Type* LoadKlassNode::Value(PhaseGVN* phase) const {
   return klass_value_common(phase);
 }
 
-// In most cases, LoadKlassNode does not have the control input set. If the control
-// input is set, it must not be removed (by LoadNode::Ideal()).
-bool LoadKlassNode::can_remove_control() const {
-  return false;
-}
-
 const Type* LoadNode::klass_value_common(PhaseGVN* phase) const {
   // Either input is TOP ==> the result is TOP
   const Type *t1 = phase->type( in(MemNode::Memory) );

src/hotspot/share/opto/memnode.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2025, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2024, Alibaba Group Holding Limited. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -522,20 +522,18 @@ class LoadNNode : public LoadNode {
 //------------------------------LoadKlassNode----------------------------------
 // Load a Klass from an object
 class LoadKlassNode : public LoadPNode {
-protected:
-  // In most cases, LoadKlassNode does not have the control input set. If the control
-  // input is set, it must not be removed (by LoadNode::Ideal()).
-  virtual bool can_remove_control() const;
+private:
+  LoadKlassNode(Node* mem, Node* adr, const TypePtr* at, const TypeKlassPtr* tk, MemOrd mo)
+    : LoadPNode(nullptr, mem, adr, at, tk, mo) {}
+
 public:
-  LoadKlassNode(Node *c, Node *mem, Node *adr, const TypePtr *at, const TypeKlassPtr *tk, MemOrd mo)
-    : LoadPNode(c, mem, adr, at, tk, mo) {}
   virtual int Opcode() const;
   virtual const Type* Value(PhaseGVN* phase) const;
   virtual Node* Identity(PhaseGVN* phase);
   virtual bool depends_only_on_test() const { return true; }
 
   // Polymorphic factory method:
-  static Node* make(PhaseGVN& gvn, Node* ctl, Node* mem, Node* adr, const TypePtr* at,
+  static Node* make(PhaseGVN& gvn, Node* mem, Node* adr, const TypePtr* at,
                     const TypeKlassPtr* tk = TypeInstKlassPtr::OBJECT);
 };
 
@@ -548,9 +546,12 @@ class LoadKlassNode : public LoadPNode {
 // extract the actual class pointer. C2's type system is agnostic on whether the
 // input address directly points into the class pointer.
 class LoadNKlassNode : public LoadNNode {
+private:
+  friend Node* LoadKlassNode::make(PhaseGVN&, Node*, Node*, const TypePtr*, const TypeKlassPtr*);
+  LoadNKlassNode(Node* mem, Node* adr, const TypePtr* at, const TypeNarrowKlass* tk, MemOrd mo)
+    : LoadNNode(nullptr, mem, adr, at, tk, mo) {}
+
 public:
-  LoadNKlassNode(Node *c, Node *mem, Node *adr, const TypePtr *at, const TypeNarrowKlass *tk, MemOrd mo)
-    : LoadNNode(c, mem, adr, at, tk, mo) {}
   virtual int Opcode() const;
   virtual uint ideal_reg() const { return Op_RegN; }
   virtual int store_Opcode() const { return Op_StoreNKlass; }

src/hotspot/share/opto/parse1.cpp

@@ -2120,7 +2120,7 @@ void Parse::call_register_finalizer() {
   // finalization.  In general this will fold up since the concrete
   // class is often visible so the access flags are constant.
   Node* klass_addr = basic_plus_adr( receiver, receiver, oopDesc::klass_offset_in_bytes() );
-  Node* klass = _gvn.transform(LoadKlassNode::make(_gvn, nullptr, immutable_memory(), klass_addr, TypeInstPtr::KLASS));
+  Node* klass = _gvn.transform(LoadKlassNode::make(_gvn, immutable_memory(), klass_addr, TypeInstPtr::KLASS));
 
   Node* access_flags_addr = basic_plus_adr(klass, klass, in_bytes(Klass::misc_flags_offset()));
   Node* access_flags = make_load(nullptr, access_flags_addr, TypeInt::UBYTE, T_BOOLEAN, MemNode::unordered);

src/hotspot/share/opto/parseHelper.cpp

@@ -156,19 +156,18 @@ void Parse::array_store_check() {
   int klass_offset = oopDesc::klass_offset_in_bytes();
   Node* p = basic_plus_adr( ary, ary, klass_offset );
   // p's type is array-of-OOPS plus klass_offset
-  Node* array_klass = _gvn.transform(LoadKlassNode::make(_gvn, nullptr, immutable_memory(), p, TypeInstPtr::KLASS));
+  Node* array_klass = _gvn.transform(LoadKlassNode::make(_gvn, immutable_memory(), p, TypeInstPtr::KLASS));
   // Get the array klass
   const TypeKlassPtr *tak = _gvn.type(array_klass)->is_klassptr();
 
   // The type of array_klass is usually INexact array-of-oop.  Heroically
   // cast array_klass to EXACT array and uncommon-trap if the cast fails.
   // Make constant out of the inexact array klass, but use it only if the cast
   // succeeds.
-  bool always_see_exact_class = false;
-  if (MonomorphicArrayCheck
-      && !too_many_traps(Deoptimization::Reason_array_check)
-      && !tak->klass_is_exact()
-      && tak != TypeInstKlassPtr::OBJECT) {
+  if (MonomorphicArrayCheck &&
+      !too_many_traps(Deoptimization::Reason_array_check) &&
+      !tak->klass_is_exact() &&
+      tak->isa_aryklassptr()) {
       // Regarding the fourth condition in the if-statement from above:
       //
       // If the compiler has determined that the type of array 'ary' (represented
@@ -190,16 +189,12 @@ void Parse::array_store_check() {
       //
       // See issue JDK-8057622 for details.
 
-    always_see_exact_class = true;
-    // (If no MDO at all, hope for the best, until a trap actually occurs.)
-
-    // Make a constant out of the inexact array klass
-    const TypeKlassPtr *extak = tak->cast_to_exactness(true);
-
+    // Make a constant out of the exact array klass
+    const TypeAryKlassPtr* extak = tak->cast_to_exactness(true)->is_aryklassptr();
     if (extak->exact_klass(true) != nullptr) {
       Node* con = makecon(extak);
-      Node* cmp = _gvn.transform(new CmpPNode( array_klass, con ));
-      Node* bol = _gvn.transform(new BoolNode( cmp, BoolTest::eq ));
+      Node* cmp = _gvn.transform(new CmpPNode(array_klass, con));
+      Node* bol = _gvn.transform(new BoolNode(cmp, BoolTest::eq));
       Node* ctrl= control();
       { BuildCutout unless(this, bol, PROB_MAX);
         uncommon_trap(Deoptimization::Reason_array_check,
@@ -210,7 +205,7 @@ void Parse::array_store_check() {
         set_control(ctrl);      // Then Don't Do It, just fall into the normal checking
       } else {                  // Cast array klass to exactness:
         // Use the exact constant value we know it is.
-        replace_in_map(array_klass,con);
+        replace_in_map(array_klass, con);
         CompileLog* log = C->log();
         if (log != nullptr) {
           log->elem("cast_up reason='monomorphic_array' from='%d' to='(exact)'",
@@ -225,12 +220,9 @@ void Parse::array_store_check() {
 
   // Extract the array element class
   int element_klass_offset = in_bytes(ObjArrayKlass::element_klass_offset());
-  Node *p2 = basic_plus_adr(array_klass, array_klass, element_klass_offset);
-  // We are allowed to use the constant type only if cast succeeded. If always_see_exact_class is true,
-  // we must set a control edge from the IfTrue node created by the uncommon_trap above to the
-  // LoadKlassNode.
-  Node* a_e_klass = _gvn.transform(LoadKlassNode::make(_gvn, always_see_exact_class ? control() : nullptr,
-                                                       immutable_memory(), p2, tak));
+  Node* p2 = basic_plus_adr(array_klass, array_klass, element_klass_offset);
+  Node* a_e_klass = _gvn.transform(LoadKlassNode::make(_gvn, immutable_memory(), p2, tak));
+  assert(array_klass->is_Con() == a_e_klass->is_Con() || StressReflectiveCode, "a constant array type must come with a constant element type");
 
   // Check (the hard way) and throw if not a subklass.
   // Result is ignored, we just need the CFG effects.

src/hotspot/share/opto/subtypenode.cpp

@@ -195,7 +195,7 @@ bool SubTypeCheckNode::verify(PhaseGVN* phase) {
           chk_off_X = phase->transform(new ConvI2LNode(chk_off_X));
 #endif
           Node* p2 = phase->transform(new AddPNode(subklass, subklass, chk_off_X));
-          Node* nkls = phase->transform(LoadKlassNode::make(*phase, nullptr, C->immutable_memory(), p2, phase->type(p2)->is_ptr(), TypeInstKlassPtr::OBJECT_OR_NULL));
+          Node* nkls = phase->transform(LoadKlassNode::make(*phase, C->immutable_memory(), p2, phase->type(p2)->is_ptr(), TypeInstKlassPtr::OBJECT_OR_NULL));
 
           return verify_helper(phase, nkls, cached_t);
         }
@@ -218,7 +218,7 @@ Node* SubTypeCheckNode::load_klass(PhaseGVN* phase) const {
   Node* subklass = nullptr;
   if (sub_t->isa_oopptr()) {
     Node* adr = phase->transform(new AddPNode(obj_or_subklass, obj_or_subklass, phase->MakeConX(oopDesc::klass_offset_in_bytes())));
-    subklass  = phase->transform(LoadKlassNode::make(*phase, nullptr, phase->C->immutable_memory(), adr, TypeInstPtr::KLASS));
+    subklass  = phase->transform(LoadKlassNode::make(*phase, phase->C->immutable_memory(), adr, TypeInstPtr::KLASS));
     record_for_cleanup(subklass, phase);
   } else {
     subklass = obj_or_subklass;