8366971: C2: Remove unused nop_list from PhaseOutput::init_buffer

Reviewed-by: epeter, dlong

src/hotspot/cpu/aarch64/aarch64.ad

@@ -5965,9 +5965,6 @@ attributes %{
   instruction_unit_size = 4;         // An instruction is 4 bytes long
   instruction_fetch_unit_size = 64;  // The processor fetches one line
   instruction_fetch_units = 1;       // of 64 bytes
-
-  // List of nop instructions
-  nops( MachNop );
 %}
 
 // We don't use an actual pipeline model so don't care about resources

src/hotspot/cpu/arm/arm.ad

@@ -2638,9 +2638,6 @@ attributes %{
   instruction_unit_size = 4;         // An instruction is 4 bytes long
   instruction_fetch_unit_size = 16;  // The processor fetches one line
   instruction_fetch_units = 1;       // of 16 bytes
-
-  // List of nop instructions
-  nops( Nop_A0, Nop_A1, Nop_MS, Nop_FA, Nop_BR );
 %}
 
 //----------RESOURCES----------------------------------------------------------

src/hotspot/cpu/ppc/ppc.ad

@@ -4920,10 +4920,6 @@ attributes %{
 
   // ...in one line
   instruction_fetch_units = 1
-
-  // Unused, list one so that array generated by adlc is not empty.
-  // Aix compiler chokes if _nop_count = 0.
-  nops(fxNop);
 %}
 
 //----------RESOURCES----------------------------------------------------------

src/hotspot/cpu/riscv/riscv.ad

@@ -3845,9 +3845,6 @@ attributes %{
 
   // ...in one line.
   instruction_fetch_units = 1;
-
-  // List of nop instructions
-  nops( MachNop );
 %}
 
 // We don't use an actual pipeline model so don't care about resources

src/hotspot/cpu/x86/x86_64.ad

@@ -3429,9 +3429,6 @@ attributes %{
   instruction_unit_size = 1;         // An instruction is 1 bytes long
   instruction_fetch_unit_size = 16;  // The processor fetches one line
   instruction_fetch_units = 1;       // of 16 bytes
-
-  // List of nop instructions
-  nops( MachNop );
 %}
 
 //----------RESOURCES----------------------------------------------------------

src/hotspot/share/adlc/adlparse.cpp

@@ -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.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -1507,36 +1507,8 @@ void ADLParser::pipe_parse(void) {
         }
 
         if (!strcmp(ident, "nops")) {
+          parse_err(WARN, "Using obsolete token, nops");
           skipws();
-          if (_curchar != '(') {
-            parse_err(SYNERR, "expected `(`, found '%c'\n", _curchar);
-            break;
-            }
-
-          next_char(); skipws();
-
-          while (_curchar != ')') {
-            ident = get_ident();
-            if (ident == nullptr) {
-              parse_err(SYNERR, "expected identifier for nop instruction, found '%c'\n", _curchar);
-              break;
-            }
-
-            pipeline->_noplist.addName(ident);
-            pipeline->_nopcnt++;
-            skipws();
-
-            if (_curchar == ',') {
-              next_char(); skipws();
-            }
-          }
-
-          next_char(); skipws();
-
-          if (_curchar == ';') {
-            next_char(); skipws();
-          }
-
           continue;
         }
 

src/hotspot/share/adlc/formsopt.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1998, 2025, 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
@@ -511,8 +511,6 @@ PipelineForm::PipelineForm()
   ,  _stagecnt              (0)
   ,  _classlist             ()
   ,  _classcnt              (0)
-  ,  _noplist               ()
-  ,  _nopcnt                (0)
   ,  _variableSizeInstrs    (false)
   ,  _branchHasDelaySlot    (false)
   ,  _maxInstrsPerBundle    (0)
@@ -533,7 +531,6 @@ void PipelineForm::output(FILE *fp) {           // Write info to output files
   const char *res;
   const char *stage;
   const char *cls;
-  const char *nop;
   int count = 0;
 
   fprintf(fp,"\nPipeline:");
@@ -574,9 +571,6 @@ void PipelineForm::output(FILE *fp) {           // Write info to output files
   for ( _classlist.reset(); (cls = _classlist.iter()) != nullptr; )
     _classdict[cls]->is_pipeclass()->output(fp);
 
-  fprintf(fp,"\nNop Instructions:");
-  for ( _noplist.reset(); (nop = _noplist.iter()) != nullptr; )
-    fprintf(fp, " \"%s\"", nop);
   fprintf(fp,"\n");
 }
 

src/hotspot/share/adlc/formsopt.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1998, 2025, 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
@@ -386,9 +386,6 @@ public:
   FormDict   _classdict;          // Class Name -> PipeClassForm mapping
   int        _classcnt;           // Number of classes
 
-  NameList   _noplist;            // List of NOP instructions
-  int        _nopcnt;             // Number of nop instructions
-
   bool       _variableSizeInstrs; // Indicates if this architecture has variable sized instructions
   bool       _branchHasDelaySlot; // Indicates that branches have delay slot instructions
   int        _maxInstrsPerBundle; // Indicates the maximum number of instructions for ILP

src/hotspot/share/adlc/output_c.cpp

@@ -977,18 +977,6 @@ void ArchDesc::build_pipe_classes(FILE *fp_cpp) {
   }
   fprintf(fp_cpp, "}\n\n");
 
-  // Output the list of nop nodes
-  fprintf(fp_cpp, "// Descriptions for emitting different functional unit nops\n");
-  const char *nop;
-  int nopcnt = 0;
-  for ( _pipeline->_noplist.reset(); (nop = _pipeline->_noplist.iter()) != nullptr; nopcnt++ );
-
-  fprintf(fp_cpp, "void Bundle::initialize_nops(MachNode * nop_list[%d]) {\n", nopcnt);
-  int i = 0;
-  for ( _pipeline->_noplist.reset(); (nop = _pipeline->_noplist.iter()) != nullptr; i++ ) {
-    fprintf(fp_cpp, "  nop_list[%d] = (MachNode *) new %sNode();\n", i, nop);
-  }
-  fprintf(fp_cpp, "};\n\n");
   fprintf(fp_cpp, "#ifndef PRODUCT\n");
   fprintf(fp_cpp, "void Bundle::dump(outputStream *st) const {\n");
   fprintf(fp_cpp, "  static const char * bundle_flags[] = {\n");
@@ -1004,7 +992,7 @@ void ArchDesc::build_pipe_classes(FILE *fp_cpp) {
   fprintf(fp_cpp, "  static const char *resource_names[%d] = {", _pipeline->_rescount);
   // Don't add compound resources to the list of resource names
   const char* resource;
-  i = 0;
+  int i = 0;
   for (_pipeline->_reslist.reset(); (resource = _pipeline->_reslist.iter()) != nullptr;) {
     if (_pipeline->_resdict[resource]->is_resource()->is_discrete()) {
       fprintf(fp_cpp, " \"%s\"%c", resource, i < _pipeline->_rescount - 1 ? ',' : ' ');

src/hotspot/share/adlc/output_h.cpp

@@ -1115,12 +1115,6 @@ void ArchDesc::declare_pipe_classes(FILE *fp_hpp) {
   fprintf(fp_hpp, "  bool use_delay() { return ((_flags & _use_delay) != 0); }\n");
   fprintf(fp_hpp, "  bool used_in_delay() { return ((_flags & _used_in_delay) != 0); }\n\n");
 
-  fprintf(fp_hpp, "  enum {\n");
-  fprintf(fp_hpp, "    _nop_count = %d\n",
-    _pipeline->_nopcnt);
-  fprintf(fp_hpp, "  };\n\n");
-  fprintf(fp_hpp, "  static void initialize_nops(MachNode *nop_list[%d]);\n\n",
-    _pipeline->_nopcnt);
   fprintf(fp_hpp, "#ifndef PRODUCT\n");
   fprintf(fp_hpp, "  void dump(outputStream *st = tty) const;\n");
   fprintf(fp_hpp, "#endif\n");

src/hotspot/share/opto/output.cpp

@@ -1399,10 +1399,6 @@ CodeBuffer* PhaseOutput::init_buffer() {
   cb->initialize_stubs_size(stub_req);
   cb->initialize_oop_recorder(C->env()->oop_recorder());
 
-  // fill in the nop array for bundling computations
-  MachNode *_nop_list[Bundle::_nop_count];
-  Bundle::initialize_nops(_nop_list);
-
   return cb;
 }
 
@@ -2062,8 +2058,7 @@ Scheduling::Scheduling(Arena *arena, Compile &compile)
   // Create a MachNopNode
   _nop = new MachNopNode();
 
-  // Now that the nops are in the array, save the count
+  // Save the count
-  // (but allow entries for the nops)
   _node_bundling_limit = compile.unique();
   uint node_max = _regalloc->node_regs_max_index();