1 /*
  2  * Copyright (c) 2020, 2023, Oracle and/or its affiliates. All rights reserved.
  3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  4  *
  5  * This code is free software; you can redistribute it and/or modify it
  6  * under the terms of the GNU General Public License version 2 only, as
  7  * published by the Free Software Foundation.
  8  *
  9  * This code is distributed in the hope that it will be useful, but WITHOUT
 10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 12  * version 2 for more details (a copy is included in the LICENSE file that
 13  * accompanied this code).
 14  *
 15  * You should have received a copy of the GNU General Public License version
 16  * 2 along with this work; if not, write to the Free Software Foundation,
 17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 18  *
 19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 20  * or visit www.oracle.com if you need additional information or have any
 21  * questions.
 22  *
 23  */
 24 
 25 #include "precompiled.hpp"
 26 #include "opto/addnode.hpp"
 27 #include "opto/callnode.hpp"
 28 #include "opto/connode.hpp"
 29 #include "opto/convertnode.hpp"
 30 #include "opto/phaseX.hpp"
 31 #include "opto/rootnode.hpp"
 32 #include "opto/subnode.hpp"
 33 #include "opto/subtypenode.hpp"
 34 
 35 const Type* SubTypeCheckNode::sub(const Type* sub_t, const Type* super_t) const {
 36   const TypeKlassPtr* superk = super_t->isa_klassptr();
 37   assert(sub_t != Type::TOP && !TypePtr::NULL_PTR->higher_equal(sub_t), "should be not null");
 38   const TypeKlassPtr* subk = sub_t->isa_klassptr() ? sub_t->is_klassptr() : sub_t->is_oopptr()->as_klass_type();
 39 
 40   // Oop can't be a subtype of abstract type that has no subclass.
 41   if (sub_t->isa_oopptr() && superk->isa_instklassptr() && superk->klass_is_exact()) {
 42     ciKlass* superklass = superk->exact_klass();
 43     if (!superklass->is_interface() && superklass->is_abstract() &&
 44         !superklass->as_instance_klass()->has_subklass()) {
 45       Compile::current()->dependencies()->assert_leaf_type(superklass);
 46       if (subk->is_same_java_type_as(superk) && !sub_t->maybe_null()) {
 47         // The super_t has no subclasses, and sub_t has the same type and is not null,
 48         // hence the check should always evaluate to EQ. However, this is an impossible
 49         // situation since super_t is also abstract, and hence sub_t cannot have the
 50         // same type and be non-null.
 51         // Still, if the non-static method of an abstract class without subclasses is
 52         // force-compiled, the Param0 has the self/this pointer with NotNull. This
 53         // method would now never be called, because of the leaf-type dependency. Hence,
 54         // just for consistency with verification, we return EQ.
 55         return TypeInt::CC_EQ;
 56       }
 57       // subk is either a supertype of superk, or null. In either case, superk is a subtype.
 58       return TypeInt::CC_GT;
 59     }
 60   }
 61 
 62   if (subk != nullptr) {
 63     switch (Compile::current()->static_subtype_check(superk, subk, false)) {
 64       case Compile::SSC_always_false:
 65         return TypeInt::CC_GT;
 66       case Compile::SSC_always_true:
 67         return TypeInt::CC_EQ;
 68       case Compile::SSC_easy_test:
 69       case Compile::SSC_full_test:
 70         break;
 71       default:
 72         ShouldNotReachHere();
 73     }
 74   }
 75 
 76   return bottom_type();
 77 }
 78 
 79 Node *SubTypeCheckNode::Ideal(PhaseGVN* phase, bool can_reshape) {
 80   Node* obj_or_subklass = in(ObjOrSubKlass);
 81   Node* superklass = in(SuperKlass);
 82 
 83   if (obj_or_subklass == nullptr ||
 84       superklass == nullptr) {
 85     return nullptr;
 86   }
 87 
 88   const Type* sub_t = phase->type(obj_or_subklass);
 89   const Type* super_t = phase->type(superklass);
 90 
 91   if (!super_t->isa_klassptr() ||
 92       (!sub_t->isa_klassptr() && !sub_t->isa_oopptr())) {
 93     return nullptr;
 94   }
 95 
 96   Node* addr = nullptr;
 97   if (obj_or_subklass->is_DecodeNKlass()) {
 98     if (obj_or_subklass->in(1) != nullptr &&
 99         obj_or_subklass->in(1)->Opcode() == Op_LoadNKlass) {
100       addr = obj_or_subklass->in(1)->in(MemNode::Address);
101     }
102   } else if (obj_or_subklass->Opcode() == Op_LoadKlass) {
103     addr = obj_or_subklass->in(MemNode::Address);
104   }
105 
106   if (addr != nullptr) {
107     intptr_t con = 0;
108     Node* obj = AddPNode::Ideal_base_and_offset(addr, phase, con);
109     if (con == oopDesc::klass_offset_in_bytes() && obj != nullptr) {
110       assert(is_oop(phase, obj), "only for oop input");
111       set_req_X(ObjOrSubKlass, obj, phase);
112       return this;
113     }
114   }
115 
116   // AllocateNode might have more accurate klass input
117   Node* allocated_klass = AllocateNode::Ideal_klass(obj_or_subklass, phase);
118   if (allocated_klass != nullptr) {
119     assert(is_oop(phase, obj_or_subklass), "only for oop input");
120     set_req_X(ObjOrSubKlass, allocated_klass, phase);
121     return this;
122   }
123 
124   // Verify that optimizing the subtype check to a simple code pattern
125   // when possible would not constant fold better
126   assert(verify(phase), "missing Value() optimization");
127 
128   return nullptr;
129 }
130 
131 #ifdef ASSERT
132 bool SubTypeCheckNode::is_oop(PhaseGVN* phase, Node* n) {
133     const Type* t = phase->type(n);
134     if (!t->isa_oopptr() && t != Type::TOP) {
135       n->dump();
136       t->dump(); tty->cr();
137       return false;
138     }
139     return true;
140 }
141 
142 static Node* record_for_cleanup(Node* n, PhaseGVN* phase) {
143   if (phase->is_IterGVN()) {
144     phase->is_IterGVN()->_worklist.push(n); // record for cleanup
145   }
146   return n;
147 }
148 bool SubTypeCheckNode::verify_helper(PhaseGVN* phase, Node* subklass, const Type* cached_t) {
149   Node* cmp = phase->transform(new CmpPNode(subklass, in(SuperKlass)));
150   record_for_cleanup(cmp, phase);
151 
152   const Type* cmp_t = phase->type(cmp);
153   const Type* t = Value(phase);
154 
155   if (t == cmp_t ||
156       t != cached_t || // previous observations don't hold anymore
157       (cmp_t != TypeInt::CC_GT && cmp_t != TypeInt::CC_EQ)) {
158     return true;
159   } else {
160     t->dump(); tty->cr();
161     this->dump(2); tty->cr();
162     cmp_t->dump(); tty->cr();
163     subklass->dump(2); tty->cr();
164     tty->print_cr("==============================");
165     phase->C->root()->dump(9999);
166     return false;
167   }
168 }
169 
170 // Verify that optimizing the subtype check to a simple code pattern when possible would not constant fold better.
171 bool SubTypeCheckNode::verify(PhaseGVN* phase) {
172   Compile* C = phase->C;
173   Node* obj_or_subklass = in(ObjOrSubKlass);
174   Node* superklass = in(SuperKlass);
175 
176   const Type* sub_t = phase->type(obj_or_subklass);
177   const Type* super_t = phase->type(superklass);
178 
179   const TypeKlassPtr* superk = super_t->isa_klassptr();
180   const TypeKlassPtr* subk = sub_t->isa_klassptr() ? sub_t->is_klassptr() : sub_t->is_oopptr()->as_klass_type();
181 
182   if (super_t->singleton() && subk != nullptr) {
183     if (obj_or_subklass->bottom_type() == Type::TOP) {
184       // The bottom type of obj_or_subklass is TOP, despite its recorded type
185       // being an OOP or a klass pointer. This can happen for example in
186       // transient scenarios where obj_or_subklass is a projection of the TOP
187       // node. In such cases, skip verification to avoid violating the contract
188       // of LoadKlassNode::make(). This does not weaken the effect of verify(),
189       // as SubTypeCheck nodes with TOP obj_or_subklass inputs are dead anyway.
190       return true;
191     }
192     const Type* cached_t = Value(phase); // cache the type to validate consistency
193     switch (C->static_subtype_check(superk, subk)) {
194       case Compile::SSC_easy_test: {
195         return verify_helper(phase, load_klass(phase), cached_t);
196       }
197       case Compile::SSC_full_test: {
198         Node* p1 = phase->transform(new AddPNode(superklass, superklass, phase->MakeConX(in_bytes(Klass::super_check_offset_offset()))));
199         Node* chk_off = phase->transform(new LoadINode(nullptr, C->immutable_memory(), p1, phase->type(p1)->is_ptr(), TypeInt::INT, MemNode::unordered));
200         record_for_cleanup(chk_off, phase);
201 
202         int cacheoff_con = in_bytes(Klass::secondary_super_cache_offset());
203         bool might_be_cache = (phase->find_int_con(chk_off, cacheoff_con) == cacheoff_con);
204         if (!might_be_cache) {
205           Node* subklass = load_klass(phase);
206           Node* chk_off_X = chk_off;
207 #ifdef _LP64
208           chk_off_X = phase->transform(new ConvI2LNode(chk_off_X));
209 #endif
210           Node* p2 = phase->transform(new AddPNode(subklass, subklass, chk_off_X));
211           Node* nkls = phase->transform(LoadKlassNode::make(*phase, nullptr, C->immutable_memory(), p2, phase->type(p2)->is_ptr(), TypeInstKlassPtr::OBJECT_OR_NULL));
212 
213           return verify_helper(phase, nkls, cached_t);
214         }
215         break;
216       }
217       case Compile::SSC_always_false:
218       case Compile::SSC_always_true:
219       default: {
220         break; // nothing to do
221       }
222     }
223   }
224 
225   return true;
226 }
227 
228 Node* SubTypeCheckNode::load_klass(PhaseGVN* phase) const {
229   Node* obj_or_subklass = in(ObjOrSubKlass);
230   const Type* sub_t = phase->type(obj_or_subklass);
231   Node* subklass = nullptr;
232   if (sub_t->isa_oopptr()) {
233     Node* adr = phase->transform(new AddPNode(obj_or_subklass, obj_or_subklass, phase->MakeConX(oopDesc::klass_offset_in_bytes())));
234     subklass  = phase->transform(LoadKlassNode::make(*phase, nullptr, phase->C->immutable_memory(), adr, TypeInstPtr::KLASS));
235     record_for_cleanup(subklass, phase);
236   } else {
237     subklass = obj_or_subklass;
238   }
239   return subklass;
240 }
241 #endif
242 
243 uint SubTypeCheckNode::size_of() const {
244   return sizeof(*this);
245 }
246 
247 uint SubTypeCheckNode::hash() const {
248   return NO_HASH;
249 }
250 
251 #ifndef PRODUCT
252 void SubTypeCheckNode::dump_spec(outputStream* st) const {
253   if (_method != nullptr) {
254     st->print(" profiled at: ");
255     _method->print_short_name(st);
256     st->print(":%d", _bci);
257   }
258 }
259 #endif