8327963: C2: fix construction of memory graph around Initialize node to prevent incorrect execution if allocation is removed

src/hotspot/share/opto/escape.hpp

@@ -565,6 +565,8 @@ class ConnectionGraph: public ArenaObj {
                         // MemNode       - new memory input for this node
                         // CheckCastPP   - allocation that this is a cast of
                         // allocation    - CheckCastPP of the allocation
+                        // NarrowMem     - newly created projection (type includes instance_id) from projection created
+                        //                 before EA
 
   // manage entries in _node_map
 

src/hotspot/share/opto/idealGraphPrinter.cpp

@@ -584,7 +584,7 @@ void IdealGraphPrinter::visit_node(Node* n, bool edges) {
       t->dump_on(&s2);
     } else if( t == Type::MEMORY ) {
       s2.print("  Memory:");
-      MemNode::dump_adr_type(node, node->adr_type(), &s2);
+      MemNode::dump_adr_type(node->adr_type(), &s2);
     }
 
     assert(s2.size() < sizeof(buffer), "size in range");

src/hotspot/share/opto/macro.cpp

@@ -1603,6 +1603,7 @@ void PhaseMacroExpand::expand_initialize_membar(AllocateNode* alloc, InitializeN
       // No InitializeNode or no stores captured by zeroing
       // elimination. Simply add the MemBarStoreStore after object
       // initialization.
+      // See comment below in this if's other branch that explains why a raw memory MemBar is good enough.
       MemBarNode* mb = MemBarNode::make(C, Op_MemBarStoreStore, Compile::AliasIdxRaw);
       transform_later(mb);
 

src/hotspot/share/opto/memnode.cpp

@@ -91,7 +91,7 @@ void MemNode::dump_spec(outputStream *st) const {
   if (in(Address) != nullptr)
     _adr_type = in(Address)->bottom_type()->isa_ptr();
 #endif
-  dump_adr_type(this, _adr_type, st);
+  dump_adr_type(_adr_type, st);
 
   Compile* C = Compile::current();
   if (C->alias_type(_adr_type)->is_volatile()) {
@@ -108,7 +108,7 @@ void MemNode::dump_spec(outputStream *st) const {
   }
 }
 
-void MemNode::dump_adr_type(const Node* mem, const TypePtr* adr_type, outputStream *st) {
+void MemNode::dump_adr_type(const TypePtr* adr_type, outputStream* st) {
   st->print(" @");
   if (adr_type == nullptr) {
     st->print("null");

src/hotspot/share/opto/memnode.hpp

@@ -167,7 +167,7 @@ class MemNode : public Node {
   bool is_unsafe_access() const { return _unsafe_access; }
 
 #ifndef PRODUCT
-  static void dump_adr_type(const Node* mem, const TypePtr* adr_type, outputStream *st);
+  static void dump_adr_type(const TypePtr* adr_type, outputStream* st);
   virtual void dump_spec(outputStream *st) const;
 #endif
 };
@@ -1380,6 +1380,8 @@ class InitializeNode: public MemBarNode {
   // Does a NarrowMemProj with this adr_type and this node as input already exist?
   bool already_has_narrow_mem_proj_with_adr_type(const TypePtr* adr_type) const;
 
+  // Used during matching: find the MachProj memory projection if there's one. Expectation is that there should be at
+  // most one.
   MachProjNode* mem_mach_proj() const;
 
 private:

src/hotspot/share/opto/multnode.cpp

@@ -262,25 +262,13 @@ ProjNode* ProjNode::other_if_proj() const {
 }
 
 #ifndef PRODUCT
-void NarrowMemProjNode::dump_adr_type(outputStream* st) const {
-  st->print(" @"); _adr_type->dump_on(st);
-  Compile* C = Compile::current();
-  Compile::AliasType* atp = C->alias_type(_adr_type);
-  ciField* field = atp->field();
-  if (field != nullptr) {
-    st->print(", name=");
-    field->print_name_on(st);
-  }
-  st->print(", idx=%d;", atp->index());
-}
-
 void NarrowMemProjNode::dump_spec(outputStream *st) const {
   ProjNode::dump_spec(st);
-  dump_adr_type(st);
+  MemNode::dump_adr_type(_adr_type, st);
 }
 
 void NarrowMemProjNode::dump_compact_spec(outputStream *st) const {
   ProjNode::dump_compact_spec(st);
-  dump_adr_type(st);
+  MemNode::dump_adr_type(_adr_type, st);
 }
 #endif

src/hotspot/share/opto/multnode.hpp

@@ -224,7 +224,6 @@ class NarrowMemProjNode : public ProjNode {
   virtual int Opcode() const;
 
 #ifndef PRODUCT
-  void dump_adr_type(outputStream* st) const;
   virtual void dump_spec(outputStream *st) const;
   virtual void dump_compact_spec(outputStream *st) const;
 #endif

src/hotspot/share/opto/node.cpp

@@ -2591,7 +2591,7 @@ void Node::dump(const char* suffix, bool mark, outputStream* st, DumpConfig* dc)
     t->dump_on(st);
   } else if (t == Type::MEMORY) {
     st->print("  Memory:");
-    MemNode::dump_adr_type(this, adr_type(), st);
+    MemNode::dump_adr_type(adr_type(), st);
   } else if (Verbose || WizardMode) {
     st->print("  Type:");
     if (t) {

src/hotspot/share/opto/phaseX.cpp

@@ -2592,15 +2592,15 @@ void PhaseIterGVN::add_users_of_use_to_worklist(Node* n, Node* use, Unique_Node_
       }
     }
   }
+  auto enqueue_init_mem_projs = [&](ProjNode* proj) {
+    add_users_to_worklist0(proj, worklist);
+    return MultiNode::CONTINUE;
+  };
   // If changed initialization activity, check dependent Stores
   if (use_op == Op_Allocate || use_op == Op_AllocateArray) {
     InitializeNode* init = use->as_Allocate()->initialization();
     if (init != nullptr) {
-      auto enqueue = [&](ProjNode* proj) {
-        add_users_to_worklist0(proj, worklist);
-        return MultiNode::CONTINUE;
-      };
-      init->apply_to_projs(enqueue, TypeFunc::Memory);
+      init->apply_to_projs(enqueue_init_mem_projs, TypeFunc::Memory);
     }
   }
   // If the ValidLengthTest input changes then the fallthrough path out of the AllocateArray may have become dead.
@@ -2615,11 +2615,7 @@ void PhaseIterGVN::add_users_of_use_to_worklist(Node* n, Node* use, Unique_Node_
 
   if (use_op == Op_Initialize) {
     InitializeNode* init = use->as_Initialize();
-    auto enqueue = [&](ProjNode* proj) {
-      add_users_to_worklist0(proj, worklist);
-      return MultiNode::CONTINUE;
-    };
-    init->apply_to_projs(enqueue, TypeFunc::Memory);
+    init->apply_to_projs(enqueue_init_mem_projs, TypeFunc::Memory);
   }
   // Loading the java mirror from a Klass requires two loads and the type
   // of the mirror load depends on the type of 'n'. See LoadNode::Value().

test/hotspot/jtreg/compiler/macronodes/TestEarlyEliminationOfAllocationWithoutUse.java

@@ -25,10 +25,11 @@
  * @test
  * @bug 8327963
  * @summary C2: fix construction of memory graph around Initialize node to prevent incorrect execution if allocation is removed
- * @run main/othervm -XX:-BackgroundCompilation TestEarlyEliminationOfAllocationWithoutUse
- * @run main/othervm TestEarlyEliminationOfAllocationWithoutUse
+ * @run main/othervm -XX:-BackgroundCompilation compiler.macronodes.TestEarlyEliminationOfAllocationWithoutUse
+ * @run main/othervm compiler.macronodes.TestEarlyEliminationOfAllocationWithoutUse
  */
 
+package compiler.macronodes;
 import java.util.Arrays;
 
 public class TestEarlyEliminationOfAllocationWithoutUse {