Drop unused accumulated first time changes/depends.

src/hydrogen-gvn.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 517 matching lines @@
   TRACE_GVN_1("Using optimistic loop invariant code motion: %s\n",
               graph()->use_optimistic_licm() ? "yes" : "no");
   for (int i = graph()->blocks()->length() - 1; i >= 0; --i) {
     HBasicBlock* block = graph()->blocks()->at(i);
     if (block->IsLoopHeader()) {
       GVNFlagSet side_effects = loop_side_effects_[block->block_id()];
       TRACE_GVN_2("Try loop invariant motion for block B%d %s\n",
                   block->block_id(),
                   GetGVNFlagsString(side_effects).get());
 
-      GVNFlagSet accumulated_first_time_depends;
-      GVNFlagSet accumulated_first_time_changes;
       HBasicBlock* last = block->loop_information()->GetLastBackEdge();
       for (int j = block->block_id(); j <= last->block_id(); ++j) {
-        ProcessLoopBlock(graph()->blocks()->at(j), block, side_effects,
-                         &accumulated_first_time_depends,
-                         &accumulated_first_time_changes);
+        ProcessLoopBlock(graph()->blocks()->at(j), block, side_effects);
       }
     }
   }
 }
 
 
 void HGlobalValueNumberingPhase::ProcessLoopBlock(
     HBasicBlock* block,
     HBasicBlock* loop_header,
-    GVNFlagSet loop_kills,
-    GVNFlagSet* first_time_depends,
-    GVNFlagSet* first_time_changes) {
+    GVNFlagSet loop_kills) {
   HBasicBlock* pre_header = loop_header->predecessors()->at(0);
   GVNFlagSet depends_flags = HValue::ConvertChangesToDependsFlags(loop_kills);
   TRACE_GVN_2("Loop invariant motion for B%d %s\n",
               block->block_id(),
               GetGVNFlagsString(depends_flags).get());
   HInstruction* instr = block->first();
   while (instr != NULL) {
     HInstruction* next = instr->next();
-    bool hoisted = false;
     if (instr->CheckFlag(HValue::kUseGVN)) {
       TRACE_GVN_4("Checking instruction %d (%s) %s. Loop %s\n",
                   instr->id(),
                   instr->Mnemonic(),
                   GetGVNFlagsString(instr->gvn_flags()).get(),
                   GetGVNFlagsString(loop_kills).get());
       bool can_hoist = !instr->gvn_flags().ContainsAnyOf(depends_flags);
       if (can_hoist && !graph()->use_optimistic_licm()) {
         can_hoist = block->IsLoopSuccessorDominator();
       }
 
       if (can_hoist) {
         bool inputs_loop_invariant = true;
         for (int i = 0; i < instr->OperandCount(); ++i) {
           if (instr->OperandAt(i)->IsDefinedAfter(pre_header)) {
             inputs_loop_invariant = false;
           }
         }
 
         if (inputs_loop_invariant && ShouldMove(instr, loop_header)) {
           TRACE_GVN_2("Hoisting loop invariant instruction i%d to block B%d\n",
                       instr->id(), pre_header->block_id());
           // Move the instruction out of the loop.
           instr->Unlink();
           instr->InsertBefore(pre_header->end());
           if (instr->HasSideEffects()) removed_side_effects_ = true;
-          hoisted = true;
         }
       }
     }
-    if (!hoisted) {
-      // If an instruction is not hoisted, we have to account for its side
-      // effects when hoisting later HTransitionElementsKind instructions.
-      GVNFlagSet previous_depends = *first_time_depends;
-      GVNFlagSet previous_changes = *first_time_changes;
-      first_time_depends->Add(instr->DependsOnFlags());
-      first_time_changes->Add(instr->ChangesFlags());
-      if (!(previous_depends == *first_time_depends)) {
-        TRACE_GVN_1("Updated first-time accumulated %s\n",
-                    GetGVNFlagsString(*first_time_depends).get());
-      }
-      if (!(previous_changes == *first_time_changes)) {
-        TRACE_GVN_1("Updated first-time accumulated %s\n",
-                    GetGVNFlagsString(*first_time_changes).get());
-      }
-    }
     instr = next;
   }
 }
 
 
 bool HGlobalValueNumberingPhase::AllowCodeMotion() {
   return info()->IsStub() || info()->opt_count() + 1 < FLAG_max_opt_count;
 }
 
 
@@ skipping 241 matching lines @@
                                                       dominated);
         successor_map->Kill(side_effects_on_all_paths);
         successor_dominators->Kill(side_effects_on_all_paths);
       }
     }
     current = next;
   }
 }
 
 } }  // namespace v8::internal