More check elimination improvements including partial learning on false branches of CompareMap and b

src/hydrogen-load-elimination.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 114 matching lines @@
       // Improvements possible:
       // - learn from HCheckMaps for field 0
       // - remove unobservable stores (write-after-write)
       // - track cells
       // - track globals
       // - track roots
     }
     return this;
   }
 
-  // Support for global analysis with HFlowEngine: Copy state to successor
-  // block.
+  // Support for global analysis with HFlowEngine: Merge given state with
+  // the other incoming state.
+  static HLoadEliminationTable* Merge(HLoadEliminationTable* succ_state,
+                                      HBasicBlock* succ_block,
+                                      HLoadEliminationTable* pred_state,
+                                      HBasicBlock* pred_block,
+                                      Zone* zone) {
+    ASSERT(pred_state != NULL);
+    if (succ_state == NULL) {
+      return pred_state->Copy(succ_block, pred_block, zone);
+    } else {
+      return succ_state->Merge(succ_block, pred_state, pred_block, zone);
+    }
+  }
+
+  // Support for global analysis with HFlowEngine: Given state merged with all
+  // the other incoming states, prepare it for use.
+  static HLoadEliminationTable* Finish(HLoadEliminationTable* state,
+                                       HBasicBlock* block,
+                                       Zone* zone) {
+    ASSERT(state != NULL);
+    return state;
+  }
+
+ private:
+  // Copy state to successor block.
   HLoadEliminationTable* Copy(HBasicBlock* succ, HBasicBlock* from_block,
                               Zone* zone) {
     HLoadEliminationTable* copy =
         new(zone) HLoadEliminationTable(zone, aliasing_);
     copy->EnsureFields(fields_.length());
     for (int i = 0; i < fields_.length(); i++) {
       copy->fields_[i] = fields_[i]->Copy(zone);
     }
     if (FLAG_trace_load_elimination) {
       TRACE((" copy-to B%d\n", succ->block_id()));
       copy->Print();
     }
     return copy;
   }
 
-  // Support for global analysis with HFlowEngine: Merge this state with
-  // the other incoming state.
+  // Merge this state with the other incoming state.
   HLoadEliminationTable* Merge(HBasicBlock* succ, HLoadEliminationTable* that,
                                HBasicBlock* that_block, Zone* zone) {
     if (that->fields_.length() < fields_.length()) {
       // Drop fields not in the other table.
       fields_.Rewind(that->fields_.length());
     }
     for (int i = 0; i < fields_.length(); i++) {
       // Merge the field approximations for like fields.
       HFieldApproximation* approx = fields_[i];
       HFieldApproximation* prev = NULL;
@@ skipping 352 matching lines @@
   } else {
     // Perform only local analysis.
     for (int i = 0; i < graph()->blocks()->length(); i++) {
       table->Kill();
       engine.AnalyzeOneBlock(graph()->blocks()->at(i), table);
     }
   }
 }
 
 } }  // namespace v8::internal