Refactor Hydrogen environment liveness analysis into an HPhase.

src/hydrogen.cc

 // Copyright 2012 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 3944 matching lines @@
   // zero-valued constant in the graph together.
   // The constant is needed to make idef-based bounds check work: the pass
   // evaluates relations with "zero" and that zero cannot be created after GVN.
   GetConstant0();
 
 #ifdef DEBUG
   // Do a full verify after building the graph and computing dominators.
   Verify(true);
 #endif
 
-  if (FLAG_analyze_environment_liveness) {
-    EnvironmentSlotLivenessAnalyzer esla(this);
-    esla.AnalyzeAndTrim();
+  if (FLAG_analyze_environment_liveness && maximum_environment_size() != 0) {
+    Run<HEnvironmentLivenessAnalysisPhase>();
   }
 
   PropagateDeoptimizingMark();
   if (!CheckConstPhiUses()) {
     *bailout_reason = SmartArrayPointer<char>(StrDup(
         "Unsupported phi use of const variable"));
     return false;
   }
   EliminateRedundantPhis();
   if (!CheckArgumentsPhiUses()) {
@@ skipping 7561 matching lines @@
   if (ShouldProduceTraceOutput()) {
     isolate()->GetHTracer()->TraceHydrogen(name(), graph_);
   }
 
 #ifdef DEBUG
   graph_->Verify(false);  // No full verify.
 #endif
 }
 
 } }  // namespace v8::internal