8336349: Fix more simple -Wzero-as-null-pointer-constant warnings in C2 code

Reviewed-by: kvn, shade

Author: Kim Barrett

src/hotspot/share/opto/buildOopMap.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -489,7 +489,7 @@ static void do_liveness(PhaseRegAlloc* regalloc, PhaseCFG* cfg, Block_List* work
         // GEN use'd bits
         for( uint l=1; l<n->req(); l++ ) {
           Node *def = n->in(l);
-          assert(def != 0, "input edge required");
+          assert(def != nullptr, "input edge required");
           int first = regalloc->get_reg_first(def);
           int second = regalloc->get_reg_second(def);
           //If peephole had removed the node,do not set live bit for it.

src/hotspot/share/opto/callnode.cpp

@@ -985,7 +985,7 @@ Node* CallNode::Ideal(PhaseGVN* phase, bool can_reshape) {
 }
 
 bool CallNode::is_call_to_arraycopystub() const {
-  if (_name != nullptr && strstr(_name, "arraycopy") != 0) {
+  if (_name != nullptr && strstr(_name, "arraycopy") != nullptr) {
     return true;
   }
   return false;

src/hotspot/share/opto/chaitin.cpp

@@ -69,7 +69,7 @@ void LRG::dump() const {
       tty->print(") ");
     }
   }
-  else if( _def == 0 ) tty->print("Dead ");
+  else if( _def == nullptr ) tty->print("Dead ");
   else tty->print("Def: N%d ",_def->_idx);
 
   tty->print("Cost:%4.2g Area:%4.2g Score:%4.2g ",_cost,_area, score());
@@ -203,7 +203,7 @@ PhaseChaitin::PhaseChaitin(uint unique, PhaseCFG &cfg, Matcher &matcher, bool sc
        nullptr
 #endif
        )
-  , _live(0)
+  , _live(nullptr)
   , _lo_degree(0), _lo_stk_degree(0), _hi_degree(0), _simplified(0)
   , _oldphi(unique)
 #ifndef PRODUCT

src/hotspot/share/opto/compile.cpp

@@ -1066,7 +1066,7 @@ void Compile::Init(bool aliasing) {
     if (has_method() && _directive->VectorizeOption) {
       set_do_vector_loop(true);
       NOT_PRODUCT(if (do_vector_loop() && Verbose) {tty->print("Compile::Init: do vectorized loops (SIMD like) for method %s\n",  method()->name()->as_quoted_ascii());})
-    } else if (has_method() && method()->name() != 0 &&
+    } else if (has_method() && method()->name() != nullptr &&
                method()->intrinsic_id() == vmIntrinsics::_forEachRemaining) {
       set_do_vector_loop(true);
     }

src/hotspot/share/opto/domgraph.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2024, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -62,7 +62,7 @@ struct Tarjan {
 // constructed.  This is the Lengauer & Tarjan O(E-alpha(E,V)) algorithm.
 void PhaseCFG::build_dominator_tree() {
   // Pre-grow the blocks array, prior to the ResourceMark kicking in
-  _blocks.map(number_of_blocks(), 0);
+  _blocks.map(number_of_blocks(), nullptr);
 
   ResourceMark rm;
   // Setup mappings from my Graph to Tarjan's stuff and back
@@ -286,8 +286,8 @@ uint PhaseCFG::do_DFS(Tarjan *tarjan, uint rpo_counter) {
 
 void Tarjan::COMPRESS()
 {
-  assert( _ancestor != 0, "" );
-  if( _ancestor->_ancestor != 0 ) {
+  assert( _ancestor != nullptr, "" );
+  if( _ancestor->_ancestor != nullptr ) {
     _ancestor->COMPRESS( );
     if( _ancestor->_label->_semi < _label->_semi )
       _label = _ancestor->_label;
@@ -575,8 +575,8 @@ int NTarjan::DFS( NTarjan *ntarjan, VectorSet &visited, PhaseIdealLoop *pil, uin
 
 void NTarjan::COMPRESS()
 {
-  assert( _ancestor != 0, "" );
-  if( _ancestor->_ancestor != 0 ) {
+  assert( _ancestor != nullptr, "" );
+  if( _ancestor->_ancestor != nullptr ) {
     _ancestor->COMPRESS( );
     if( _ancestor->_label->_semi < _label->_semi )
       _label = _ancestor->_label;

src/hotspot/share/opto/idealKit.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2005, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2005, 2024, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -50,7 +50,7 @@ IdealKit::IdealKit(GraphKit* gkit, bool delay_all_transforms, bool has_declarati
   assert(_initial_memory == nullptr || _initial_memory->Opcode() == Op_MergeMem, "memory must be pre-split");
   assert(!_gvn.is_IterGVN(), "IdealKit can't be used during Optimize phase");
   int init_size = 5;
-  _pending_cvstates = new (C->node_arena()) GrowableArray<Node*>(C->node_arena(), init_size, 0, 0);
+  _pending_cvstates = new (C->node_arena()) GrowableArray<Node*>(C->node_arena(), init_size, 0, nullptr);
   DEBUG_ONLY(_state = new (C->node_arena()) GrowableArray<int>(C->node_arena(), init_size, 0, 0));
   if (!has_declarations) {
      declarations_done();

src/hotspot/share/opto/ifg.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1998, 2024, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -622,7 +622,7 @@ bool PhaseChaitin::remove_node_if_not_used(Block* b, uint location, Node* n, uin
     b->remove_node(location);
     LRG& lrg = lrgs(lid);
     if (lrg._def == n) {
-      lrg._def = 0;
+      lrg._def = nullptr;
     }
     n->disconnect_inputs(C);
     _cfg.unmap_node_from_block(n);

src/hotspot/share/opto/live.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2024, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -44,8 +44,8 @@
 // live-out sets.  This separate compilation is done in the outer loop below.
 PhaseLive::PhaseLive(const PhaseCFG &cfg, const LRG_List &names, Arena *arena, bool keep_deltas)
   : Phase(LIVE),
-  _live(0),
-  _livein(0),
+  _live(nullptr),
+  _livein(nullptr),
   _cfg(cfg),
   _names(names),
   _arena(arena),

src/hotspot/share/opto/loopnode.cpp

@@ -6338,7 +6338,7 @@ void PhaseIdealLoop::build_loop_late_post_work(Node *n, bool pinned) {
     }
   } else {                      // No slot zero
     if( n->is_CFG() ) {         // CFG with no slot 0 is dead
-      _loop_or_ctrl.map(n->_idx,0);    // No block setting, it's globally dead
+      _loop_or_ctrl.map(n->_idx,nullptr); // No block setting, it's globally dead
       return;
     }
     assert(!n->is_CFG() || n->outcnt() == 0, "");
@@ -6356,7 +6356,7 @@ void PhaseIdealLoop::build_loop_late_post_work(Node *n, bool pinned) {
       assert(_loop_or_ctrl[n->out(i1)->_idx] == nullptr, "all uses must also be dead");
     }
 #endif
-    _loop_or_ctrl.map(n->_idx, 0);     // This node is useless
+    _loop_or_ctrl.map(n->_idx, nullptr); // This node is useless
     _deadlist.push(n);
     return;
   }

src/hotspot/share/opto/matcher.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2024, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -1812,7 +1812,7 @@ MachNode *Matcher::ReduceInst( State *s, int rule, Node *&mem ) {
     ReduceInst_Interior( s, rule, mem, mach, 1 );
   } else {
     // Instruction chain rules are data-dependent on their inputs
-    mach->add_req(0);             // Set initial control to none
+    mach->add_req(nullptr);     // Set initial control to none
     ReduceInst_Chain_Rule( s, rule, mem, mach );
   }
 

src/hotspot/share/opto/memnode.cpp

@@ -2862,7 +2862,7 @@ class ArrayPointer {
                _pointer->_idx, _pointer->Name(),
                _base->_idx, _base->Name(),
                (long long)_constant_offset);
-    if (_int_offset != 0) {
+    if (_int_offset != nullptr) {
       tty->print(" + I2L[%d %s] << %d",
                  _int_offset->_idx, _int_offset->Name(), _int_offset_shift);
     }

src/hotspot/share/opto/node.cpp

@@ -1101,7 +1101,7 @@ uint Node::size(PhaseRegAlloc *ra_) const { return 0; }
 //------------------------------CFG Construction-------------------------------
 // Nodes that end basic blocks, e.g. IfTrue/IfFalse, JumpProjNode, Root,
 // Goto and Return.
-const Node *Node::is_block_proj() const { return 0; }
+const Node *Node::is_block_proj() const { return nullptr; }
 
 // Minimum guaranteed type
 const Type *Node::bottom_type() const { return Type::BOTTOM; }

src/hotspot/share/opto/output.cpp

@@ -2900,7 +2900,7 @@ void Scheduling::verify_good_schedule( Block *b, const char *msg ) {
     // Now make all USEs live
     for( uint i=1; i<n->req(); i++ ) {
       Node *def = n->in(i);
-      assert(def != 0, "input edge required");
+      assert(def != nullptr, "input edge required");
       OptoReg::Name reg_lo = _regalloc->get_reg_first(def);
       OptoReg::Name reg_hi = _regalloc->get_reg_second(def);
       if( OptoReg::is_valid(reg_lo) ) {
@@ -2923,7 +2923,7 @@ void Scheduling::verify_good_schedule( Block *b, const char *msg ) {
 // Conditionally add precedence edges.  Avoid putting edges on Projs.
 static void add_prec_edge_from_to( Node *from, Node *to ) {
   if( from->is_Proj() ) {       // Put precedence edge on Proj's input
-    assert( from->req() == 1 && (from->len() == 1 || from->in(1)==0), "no precedence edges on projections" );
+    assert( from->req() == 1 && (from->len() == 1 || from->in(1) == nullptr), "no precedence edges on projections" );
     from = from->in(0);
   }
   if( from != to &&             // No cycles (for things like LD L0,[L0+4] )

src/hotspot/share/opto/phaseX.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2024, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -780,7 +780,7 @@ void PhaseGVN::dead_loop_check( Node *n ) {
         }
       }
     }
-    if (!no_dead_loop) n->dump_bfs(100,0,"#");
+    if (!no_dead_loop) n->dump_bfs(100,nullptr,"#");
     assert(no_dead_loop, "dead loop detected");
   }
 }
@@ -1135,7 +1135,7 @@ bool PhaseIterGVN::verify_node_value(Node* n) {
   }
   tty->cr();
   tty->print_cr("Missed Value optimization:");
-  n->dump_bfs(1, 0, "");
+  n->dump_bfs(1, nullptr, "");
   tty->print_cr("Current type:");
   told->dump_on(tty);
   tty->cr();

src/hotspot/share/opto/reg_split.cpp

@@ -309,7 +309,7 @@ static Node* clone_node(Node* def, Block *b, Compile* C) {
       assert(false, "RA Split failed: attempt to clone node with anti_dependence");
       C->record_method_not_compilable("RA Split failed: attempt to clone node with anti_dependence");
     }
-    return 0;
+    return nullptr;
   }
   return def->clone();
 }
@@ -341,7 +341,7 @@ Node *PhaseChaitin::split_Rematerialize(Node *def, Block *b, uint insidx, uint &
       Node *in_spill;
       if (in->ideal_reg() != Op_RegFlags) {
         in_spill = get_spillcopy_wide(MachSpillCopyNode::InputToRematerialization, in, def, i);
-        if (!in_spill) { return 0; } // Bailed out
+        if (!in_spill) { return nullptr; } // Bailed out
         insert_proj(b_def, idx_def, in_spill, maxlrg++);
         if (b_def == b) {
           insidx++;
@@ -357,7 +357,7 @@ Node *PhaseChaitin::split_Rematerialize(Node *def, Block *b, uint insidx, uint &
                  " range and defining node %d: %s may not be rematerialized.",
                  def->_idx, def->Name(), in->_idx, in->Name());
           C->record_method_not_compilable("attempted to spill a non-spillable item with RegFlags input");
-          return 0; // Bailed out
+          return nullptr; // Bailed out
         }
       }
     }
@@ -366,7 +366,7 @@ Node *PhaseChaitin::split_Rematerialize(Node *def, Block *b, uint insidx, uint &
   Node *spill = clone_node(def, b, C);
   if (spill == nullptr || C->check_node_count(NodeLimitFudgeFactor, out_of_nodes)) {
     // Check when generating nodes
-    return 0;
+    return nullptr;
   }
 
   // See if any inputs are currently being spilled, and take the

src/hotspot/share/opto/regalloc.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2024, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -38,7 +38,7 @@ PhaseRegAlloc::PhaseRegAlloc( uint unique, PhaseCFG &cfg,
                               Matcher &matcher,
                               void (*pr_stats)() ):
                Phase(Register_Allocation),
-               _node_regs(0),
+               _node_regs(nullptr),
                _node_regs_max_index(0),
                _cfg(cfg),
                _framesize(0xdeadbeef),

src/hotspot/share/opto/type.cpp

@@ -554,9 +554,9 @@ void Type::Initialize_shared(Compile* current) {
   TypeInstPtr::BOTTOM  = TypeInstPtr::make(TypePtr::BotPTR,  current->env()->Object_klass());
   TypeInstPtr::MIRROR  = TypeInstPtr::make(TypePtr::NotNull, current->env()->Class_klass());
   TypeInstPtr::MARK    = TypeInstPtr::make(TypePtr::BotPTR,  current->env()->Object_klass(),
-                                           false, 0, oopDesc::mark_offset_in_bytes());
+                                           false, nullptr, oopDesc::mark_offset_in_bytes());
   TypeInstPtr::KLASS   = TypeInstPtr::make(TypePtr::BotPTR,  current->env()->Object_klass(),
-                                           false, 0, oopDesc::klass_offset_in_bytes());
+                                           false, nullptr, oopDesc::klass_offset_in_bytes());
   TypeOopPtr::BOTTOM  = TypeOopPtr::make(TypePtr::BotPTR, OffsetBot, TypeOopPtr::InstanceBot);
 
   TypeMetadataPtr::BOTTOM = TypeMetadataPtr::make(TypePtr::BotPTR, nullptr, OffsetBot);
@@ -567,7 +567,7 @@ void Type::Initialize_shared(Compile* current) {
   TypeNarrowKlass::NULL_PTR = TypeNarrowKlass::make( TypePtr::NULL_PTR );
 
   mreg2type[Op_Node] = Type::BOTTOM;
-  mreg2type[Op_Set ] = 0;
+  mreg2type[Op_Set ] = nullptr;
   mreg2type[Op_RegN] = TypeNarrowOop::BOTTOM;
   mreg2type[Op_RegI] = TypeInt::INT;
   mreg2type[Op_RegP] = TypePtr::BOTTOM;
@@ -3129,7 +3129,7 @@ const TypeRawPtr *TypeRawPtr::NOTNULL;
 const TypeRawPtr *TypeRawPtr::make( enum PTR ptr ) {
   assert( ptr != Constant, "what is the constant?" );
   assert( ptr != Null, "Use TypePtr for null" );
-  return (TypeRawPtr*)(new TypeRawPtr(ptr,0))->hashcons();
+  return (TypeRawPtr*)(new TypeRawPtr(ptr,nullptr))->hashcons();
 }
 
 const TypeRawPtr *TypeRawPtr::make( address bits ) {
@@ -3141,7 +3141,7 @@ const TypeRawPtr *TypeRawPtr::make( address bits ) {
 const TypeRawPtr* TypeRawPtr::cast_to_ptr_type(PTR ptr) const {
   assert( ptr != Constant, "what is the constant?" );
   assert( ptr != Null, "Use TypePtr for null" );
-  assert( _bits==0, "Why cast a constant address?");
+  assert( _bits == nullptr, "Why cast a constant address?");
   if( ptr == _ptr ) return this;
   return make(ptr);
 }
@@ -3525,7 +3525,7 @@ TypeOopPtr::TypeOopPtr(TYPES t, PTR ptr, ciKlass* k, const TypeInterfaces* inter
   }
 #endif
   if (Compile::current()->eliminate_boxing() && (t == InstPtr) &&
-      (offset > 0) && xk && (k != 0) && k->is_instance_klass()) {
+      (offset > 0) && xk && (k != nullptr) && k->is_instance_klass()) {
     _is_ptr_to_boxed_value = k->as_instance_klass()->is_boxed_value_offset(offset);
   }
 #ifdef _LP64