8265587: IGV: track nodes across matching

Preserve the IGV node identifier of Ideal nodes in their corresponding machine
nodes after matching, to allow IGV users to track nodes across this phase.

Reviewed-by: thartmann, vlivanov

src/hotspot/share/opto/idealGraphPrinter.cpp

@@ -450,13 +450,10 @@ void IdealGraphPrinter::visit_node(Node *n, bool edges, VectorSet* temp_set) {
       } else {
         print_prop("is_dontcare", "false");
       }
-
-#ifdef ASSERT
       Node* old = C->matcher()->find_old_node(node);
       if (old != NULL) {
         print_prop("old_node_idx", old->_idx);
       }
-#endif
     }
 
     if (node->is_Proj()) {

src/hotspot/share/opto/matcher.cpp

@@ -71,10 +71,11 @@ Matcher::Matcher()
   _end_inst_chain_rule(_END_INST_CHAIN_RULE),
   _must_clone(must_clone),
   _shared_nodes(C->comp_arena()),
-#ifdef ASSERT
+#ifndef PRODUCT
   _old2new_map(C->comp_arena()),
   _new2old_map(C->comp_arena()),
-#endif
+  _reused(C->comp_arena()),
+#endif // !PRODUCT
   _allocation_started(false),
   _ruleName(ruleName),
   _register_save_policy(register_save_policy),
@@ -1098,16 +1099,12 @@ Node *Matcher::xform( Node *n, int max_stack ) {
             if (n->is_Proj() && n->in(0) != NULL && n->in(0)->is_Multi()) {       // Projections?
               // Convert to machine-dependent projection
               m = n->in(0)->as_Multi()->match( n->as_Proj(), this );
-#ifdef ASSERT
-              _new2old_map.map(m->_idx, n);
-#endif
+              NOT_PRODUCT(record_new2old(m, n);)
               if (m->in(0) != NULL) // m might be top
                 collect_null_checks(m, n);
             } else {                // Else just a regular 'ol guy
               m = n->clone();       // So just clone into new-space
-#ifdef ASSERT
-              _new2old_map.map(m->_idx, n);
-#endif
+              NOT_PRODUCT(record_new2old(m, n);)
               // Def-Use edges will be added incrementally as Uses
               // of this node are matched.
               assert(m->outcnt() == 0, "no Uses of this clone yet");
@@ -1165,9 +1162,7 @@ Node *Matcher::xform( Node *n, int max_stack ) {
             // || op == Op_BoxLock  // %%%% enable this and remove (+++) in chaitin.cpp
             ) {
           m = m->clone();
-#ifdef ASSERT
-          _new2old_map.map(m->_idx, n);
-#endif
+          NOT_PRODUCT(record_new2old(m, n));
           mstack.push(m, Post_Visit, n, i); // Don't need to visit
           mstack.push(m->in(0), Visit, m, 0);
         } else {
@@ -1499,10 +1494,8 @@ MachNode *Matcher::match_tree( const Node *n ) {
   }
   // Reduce input tree based upon the state labels to machine Nodes
   MachNode *m = ReduceInst(s, s->rule(mincost), mem);
-#ifdef ASSERT
-  _old2new_map.map(n->_idx, m);
-  _new2old_map.map(m->_idx, (Node*)n);
-#endif
+  // New-to-old mapping is done in ReduceInst, to cover complex instructions.
+  NOT_PRODUCT(_old2new_map.map(n->_idx, m);)
 
   // Add any Matcher-ignored edges
   uint cnt = n->req();
@@ -1759,6 +1752,7 @@ MachNode *Matcher::ReduceInst( State *s, int rule, Node *&mem ) {
   mach->_opnds[0] = s->MachOperGenerator(_reduceOp[rule]);
   assert( mach->_opnds[0] != NULL, "Missing result operand" );
   Node *leaf = s->_leaf;
+  NOT_PRODUCT(record_new2old(mach, leaf);)
   // Check for instruction or instruction chain rule
   if( rule >= _END_INST_CHAIN_RULE || rule < _BEGIN_INST_CHAIN_RULE ) {
     assert(C->node_arena()->contains(s->_leaf) || !has_new_node(s->_leaf),
@@ -1827,9 +1821,7 @@ MachNode *Matcher::ReduceInst( State *s, int rule, Node *&mem ) {
     for( uint i=0; i<mach->req(); i++ ) {
       mach->set_req(i,NULL);
     }
-#ifdef ASSERT
-    _new2old_map.map(ex->_idx, s->_leaf);
-#endif
+    NOT_PRODUCT(record_new2old(ex, s->_leaf);)
   }
 
   // PhaseChaitin::fixup_spills will sometimes generate spill code
@@ -2427,12 +2419,22 @@ void Matcher::find_shared_post_visit(Node* n, uint opcode) {
   }
 }
 
-#ifdef ASSERT
+#ifndef PRODUCT
+void Matcher::record_new2old(Node* newn, Node* old) {
+  _new2old_map.map(newn->_idx, old);
+  if (!_reused.test_set(old->_igv_idx)) {
+    // Reuse the Ideal-level IGV identifier so that the node can be tracked
+    // across matching. If there are multiple machine nodes expanded from the
+    // same Ideal node, only one will reuse its IGV identifier.
+    newn->_igv_idx = old->_igv_idx;
+  }
+}
+
 // machine-independent root to machine-dependent root
 void Matcher::dump_old2new_map() {
   _old2new_map.dump();
 }
-#endif
+#endif // !PRODUCT
 
 //---------------------------collect_null_checks-------------------------------
 // Find null checks in the ideal graph; write a machine-specific node for

src/hotspot/share/opto/matcher.hpp

@@ -135,8 +135,11 @@ private:
 
   Node_Array _shared_nodes;
 
-  debug_only(Node_Array _old2new_map;)   // Map roots of ideal-trees to machine-roots
-  debug_only(Node_Array _new2old_map;)   // Maps machine nodes back to ideal
+#ifndef PRODUCT
+  Node_Array _old2new_map;    // Map roots of ideal-trees to machine-roots
+  Node_Array _new2old_map;    // Maps machine nodes back to ideal
+  VectorSet _reused;          // Ideal IGV identifiers reused by machine nodes
+#endif // !PRODUCT
 
   // Accessors for the inherited field PhaseTransform::_nodes:
   void   grow_new_node_array(uint idx_limit) {
@@ -556,13 +559,16 @@ public:
   // Does n lead to an uncommon trap that can cause deoptimization?
   static bool branches_to_uncommon_trap(const Node *n);
 
-#ifdef ASSERT
+#ifndef PRODUCT
+  // Record mach-to-Ideal mapping, reusing the Ideal IGV identifier if possible.
+  void record_new2old(Node* newn, Node* old);
+
   void dump_old2new_map();      // machine-independent to machine-dependent
 
   Node* find_old_node(Node* new_node) {
     return _new2old_map[new_node->_idx];
   }
-#endif
+#endif // !PRODUCT
 };
 
 #endif // SHARE_OPTO_MATCHER_HPP

src/hotspot/share/opto/node.hpp

@@ -322,9 +322,11 @@ protected:
   // preserved in _parse_idx.
   const node_idx_t _idx;
   DEBUG_ONLY(const node_idx_t _parse_idx;)
-  // IGV node identifier. It is similar to Node::_debug_idx in that it is unique
-  // across all compilation phases, but different in that it is initialized in
-  // each compilation, for stability.
+  // IGV node identifier. Two nodes, possibly in different compilation phases,
+  // have the same IGV identifier if (and only if) they are the very same node
+  // (same memory address) or one is "derived" from the other (by e.g.
+  // renumbering or matching). This identifier makes it possible to follow the
+  // entire lifetime of a node in IGV even if its C2 identifier (_idx) changes.
   NOT_PRODUCT(node_idx_t _igv_idx;)
 
   // Get the (read-only) number of input edges