8279956: Useless method Scheduling::ComputeLocalLatenciesForward()

Reviewed-by: jiefu, neliasso

src/hotspot/share/opto/output.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1998, 2022, 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
@@ -96,10 +96,6 @@ private:
   // Free list for pinch nodes.
   Node_List _pinch_free_list;
 
-  // Latency from the beginning of the containing basic block (base 1)
-  // for each node.
-  unsigned short *_node_latency;
-
   // Number of uses of this node within the containing basic block.
   short *_uses;
 
@@ -162,10 +158,6 @@ public:
   // Do the scheduling
   void DoScheduling();
 
-  // Compute the local latencies walking forward over the list of
-  // nodes for a basic block
-  void ComputeLocalLatenciesForward(const Block *bb);
-
   // Compute the register antidependencies within a basic block
   void ComputeRegisterAntidependencies(Block *bb);
   void verify_do_def( Node *n, OptoReg::Name def, const char *msg );
@@ -2027,7 +2019,6 @@ Scheduling::Scheduling(Arena *arena, Compile &compile)
   _node_bundling_base = NEW_ARENA_ARRAY(compile.comp_arena(), Bundle, node_max);
 
   // Allocate space for fixed-size arrays
-  _node_latency    = NEW_ARENA_ARRAY(arena, unsigned short, node_max);
   _uses            = NEW_ARENA_ARRAY(arena, short,          node_max);
   _current_latency = NEW_ARENA_ARRAY(arena, unsigned short, node_max);
 
@@ -2035,7 +2026,6 @@ Scheduling::Scheduling(Arena *arena, Compile &compile)
   for (uint i = 0; i < node_max; i++) {
     ::new (&_node_bundling_base[i]) Bundle();
   }
-  memset(_node_latency,       0, node_max * sizeof(unsigned short));
   memset(_uses,               0, node_max * sizeof(short));
   memset(_current_latency,    0, node_max * sizeof(unsigned short));
 
@@ -2141,54 +2131,6 @@ void PhaseOutput::ScheduleAndBundle() {
 #endif
 }
 
-// Compute the latency of all the instructions.  This is fairly simple,
-// because we already have a legal ordering.  Walk over the instructions
-// from first to last, and compute the latency of the instruction based
-// on the latency of the preceding instruction(s).
-void Scheduling::ComputeLocalLatenciesForward(const Block *bb) {
-#ifndef PRODUCT
-  if (_cfg->C->trace_opto_output())
-    tty->print("# -> ComputeLocalLatenciesForward\n");
-#endif
-
-  // Walk over all the schedulable instructions
-  for( uint j=_bb_start; j < _bb_end; j++ ) {
-
-    // This is a kludge, forcing all latency calculations to start at 1.
-    // Used to allow latency 0 to force an instruction to the beginning
-    // of the bb
-    uint latency = 1;
-    Node *use = bb->get_node(j);
-    uint nlen = use->len();
-
-    // Walk over all the inputs
-    for ( uint k=0; k < nlen; k++ ) {
-      Node *def = use->in(k);
-      if (!def)
-        continue;
-
-      uint l = _node_latency[def->_idx] + use->latency(k);
-      if (latency < l)
-        latency = l;
-    }
-
-    _node_latency[use->_idx] = latency;
-
-#ifndef PRODUCT
-    if (_cfg->C->trace_opto_output()) {
-      tty->print("# latency %4d: ", latency);
-      use->dump();
-    }
-#endif
-  }
-
-#ifndef PRODUCT
-  if (_cfg->C->trace_opto_output())
-    tty->print("# <- ComputeLocalLatenciesForward\n");
-#endif
-
-} // end ComputeLocalLatenciesForward
-
 // See if this node fits into the present instruction bundle
 bool Scheduling::NodeFitsInBundle(Node *n) {
   uint n_idx = n->_idx;
@@ -2764,9 +2706,6 @@ void Scheduling::DoScheduling() {
     ComputeRegisterAntidependencies(bb);
     if (C->failing())  return;  // too many D-U pinch points
 
-    // Compute intra-bb latencies for the nodes
-    ComputeLocalLatenciesForward(bb);
-
     // Compute the usage within the block, and set the list of all nodes
     // in the block that have no uses within the block.
     ComputeUseCount(bb);