Turn dead code elimination into a proper HPhase.

src/hydrogen.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 15 matching lines @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #include "hydrogen.h"
 
 #include <algorithm>
 
 #include "v8.h"
 #include "codegen.h"
 #include "full-codegen.h"
 #include "hashmap.h"
+#include "hydrogen-dce.h"
 #include "hydrogen-environment-liveness.h"
 #include "hydrogen-escape-analysis.h"
 #include "hydrogen-infer-representation.h"
 #include "hydrogen-gvn.h"
 #include "hydrogen-osr.h"
 #include "hydrogen-range-analysis.h"
 #include "hydrogen-uint32-analysis.h"
 #include "lithium-allocator.h"
 #include "parser.h"
 #include "scopeinfo.h"
@@ skipping 3411 matching lines @@
     return false;
   }
   EliminateRedundantPhis();
   if (!CheckArgumentsPhiUses()) {
     *bailout_reason = SmartArrayPointer<char>(StrDup(
         "Unsupported phi use of arguments"));
     return false;
   }
 
   // Remove dead code and phis
-  if (FLAG_dead_code_elimination) {
-    DeadCodeElimination("H_Eliminate early dead code");
-  }
+  if (FLAG_dead_code_elimination) Run<HDeadCodeEliminationPhase>();
   CollectPhis();
 
   if (has_osr()) osr()->FinishOsrValues();
 
   Run<HInferRepresentationPhase>();
 
   // Remove HSimulate instructions that have turned out not to be needed
   // after all by folding them into the following HSimulate.
   // This must happen after inferring representations.
   MergeRemovableSimulates();
@@ skipping 20 matching lines @@
 
   // Eliminate redundant stack checks on backwards branches.
   HStackCheckEliminator sce(this);
   sce.Process();
 
   if (FLAG_idefs) SetupInformativeDefinitions();
   if (FLAG_array_bounds_checks_elimination && !FLAG_idefs) {
     EliminateRedundantBoundsChecks();
   }
   if (FLAG_array_index_dehoisting) DehoistSimpleArrayIndexComputations();
-  if (FLAG_dead_code_elimination) {
-    DeadCodeElimination("H_Eliminate late dead code");
-  }
+  if (FLAG_dead_code_elimination) Run<HDeadCodeEliminationPhase>();
 
   RestoreActualValues();
 
   return true;
 }
 
 
 void HGraph::SetupInformativeDefinitionsInBlock(HBasicBlock* block) {
   for (int phi_index = 0; phi_index < block->phis()->length(); phi_index++) {
     HPhi* phi = block->phis()->at(phi_index);
@@ skipping 460 matching lines @@
         array_instruction = static_cast<ArrayInstructionInterface*>(op);
       } else {
         continue;
       }
       DehoistArrayIndex(array_instruction);
     }
   }
 }
 
 
-void HGraph::DeadCodeElimination(const char* phase_name) {
-  HPhase phase(phase_name, this);
-  MarkLiveInstructions();
-  RemoveDeadInstructions();
-}
-
-
-void HGraph::MarkLiveInstructions() {
-  ZoneList<HValue*> worklist(blocks_.length(), zone());
-
-  // Mark initial root instructions for dead code elimination.
-  for (int i = 0; i < blocks()->length(); ++i) {
-    HBasicBlock* block = blocks()->at(i);
-    for (HInstructionIterator it(block); !it.Done(); it.Advance()) {
-      HInstruction* instr = it.Current();
-      if (instr->CannotBeEliminated()) MarkLive(NULL, instr, &worklist);
-    }
-    for (int j = 0; j < block->phis()->length(); j++) {
-      HPhi* phi = block->phis()->at(j);
-      if (phi->CannotBeEliminated()) MarkLive(NULL, phi, &worklist);
-    }
-  }
-
-  // Transitively mark all inputs of live instructions live.
-  while (!worklist.is_empty()) {
-    HValue* instr = worklist.RemoveLast();
-    for (int i = 0; i < instr->OperandCount(); ++i) {
-      MarkLive(instr, instr->OperandAt(i), &worklist);
-    }
-  }
-}
-
-
-void HGraph::MarkLive(HValue* ref, HValue* instr, ZoneList<HValue*>* worklist) {
-  if (!instr->CheckFlag(HValue::kIsLive)) {
-    instr->SetFlag(HValue::kIsLive);
-    worklist->Add(instr, zone());
-
-    if (FLAG_trace_dead_code_elimination) {
-      HeapStringAllocator allocator;
-      StringStream stream(&allocator);
-      if (ref != NULL) {
-        ref->PrintTo(&stream);
-      } else {
-        stream.Add("root ");
-      }
-      stream.Add(" -> ");
-      instr->PrintTo(&stream);
-      PrintF("[MarkLive %s]\n", *stream.ToCString());
-    }
-  }
-}
-
-
-void HGraph::RemoveDeadInstructions() {
-  ZoneList<HPhi*> dead_phis(blocks_.length(), zone());
-
-  // Remove any instruction not marked kIsLive.
-  for (int i = 0; i < blocks()->length(); ++i) {
-    HBasicBlock* block = blocks()->at(i);
-    for (HInstructionIterator it(block); !it.Done(); it.Advance()) {
-      HInstruction* instr = it.Current();
-      if (!instr->CheckFlag(HValue::kIsLive)) {
-        // Instruction has not been marked live; assume it is dead and remove.
-        // TODO(titzer): we don't remove constants because some special ones
-        // might be used by later phases and are assumed to be in the graph
-        if (!instr->IsConstant()) instr->DeleteAndReplaceWith(NULL);
-      } else {
-        // Clear the liveness flag to leave the graph clean for the next DCE.
-        instr->ClearFlag(HValue::kIsLive);
-      }
-    }
-    // Collect phis that are dead and remove them in the next pass.
-    for (int j = 0; j < block->phis()->length(); j++) {
-      HPhi* phi = block->phis()->at(j);
-      if (!phi->CheckFlag(HValue::kIsLive)) {
-        dead_phis.Add(phi, zone());
-      } else {
-        phi->ClearFlag(HValue::kIsLive);
-      }
-    }
-  }
-
-  // Process phis separately to avoid simultaneously mutating the phi list.
-  while (!dead_phis.is_empty()) {
-    HPhi* phi = dead_phis.RemoveLast();
-    HBasicBlock* block = phi->block();
-    phi->DeleteAndReplaceWith(NULL);
-    block->RecordDeletedPhi(phi->merged_index());
-  }
-}
-
-
 void HGraph::RestoreActualValues() {
   HPhase phase("H_Restore actual values", this);
 
   for (int block_index = 0; block_index < blocks()->length(); block_index++) {
     HBasicBlock* block = blocks()->at(block_index);
 
 #ifdef DEBUG
     for (int i = 0; i < block->phis()->length(); i++) {
       HPhi* phi = block->phis()->at(i);
       ASSERT(phi->ActualValue() == phi);
@@ skipping 6741 matching lines @@
   if (ShouldProduceTraceOutput()) {
     isolate()->GetHTracer()->TraceHydrogen(name(), graph_);
   }
 
 #ifdef DEBUG
   graph_->Verify(false);  // No full verify.
 #endif
 }
 
 } }  // namespace v8::internal