Flow engine fixes: unreachable block processing, state merging.

src/hydrogen-flow-engine.h

 // 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 106 matching lines @@
     SetStateAt(root, initial);
 
     // Iterate all dominated blocks starting from the given start block.
     for (int i = root->block_id(); i < graph_->blocks()->length(); i++) {
       HBasicBlock* block = graph_->blocks()->at(i);
 
       // Skip blocks not dominated by the root node.
       if (SkipNonDominatedBlock(root, block)) continue;
       State* state = StateAt(block);
 
-      if (block->IsLoopHeader()) {
-        // Apply loop effects before analyzing loop body.
-        ComputeLoopEffects(block)->Apply(state);
-      } else {
-        // Must have visited all predecessors before this block.
-        CheckPredecessorCount(block);
-      }
+      if (block->IsReachable()) {
+        if (block->IsLoopHeader()) {
+          // Apply loop effects before analyzing loop body.
+          ComputeLoopEffects(block)->Apply(state);
+        } else {
+          // Must have visited all predecessors before this block.
+          CheckPredecessorCount(block);
+        }
 
-      // Go through all instructions of the current block, updating the state.
-      for (HInstructionIterator it(block); !it.Done(); it.Advance()) {
-        state = state->Process(it.Current(), zone_);
+        // Go through all instructions of the current block, updating the state.
+        for (HInstructionIterator it(block); !it.Done(); it.Advance()) {
+          state = state->Process(it.Current(), zone_);
+        }
       }
 
       // Propagate the block state forward to all successor blocks.
       int max = block->end()->SuccessorCount();
       for (int i = 0; i < max; i++) {
         HBasicBlock* succ = block->end()->SuccessorAt(i);
         IncrementPredecessorCount(succ);
         if (StateAt(succ) == NULL) {
           // This is the first state to reach the successor.
           if (max == 1 && succ->predecessors()->length() == 1) {
             // Optimization: successor can inherit this state.
             SetStateAt(succ, state);
           } else {
             // Successor needs a copy of the state.
-            SetStateAt(succ, state->Copy(succ, zone_));
+            SetStateAt(succ, state->Copy(succ, block, zone_));
           }
         } else {
           // Merge the current state with the state already at the successor.
-          SetStateAt(succ, state->Merge(succ, StateAt(succ), zone_));
+          SetStateAt(succ, StateAt(succ)->Merge(succ, state, block, zone_));
         }
       }
     }
   }
 
  private:
   // Computes and caches the loop effects for the loop which has the given
   // block as its loop header.
   Effects* ComputeLoopEffects(HBasicBlock* block) {
     ASSERT(block->IsLoopHeader());
@@ skipping 11 matching lines @@
       HBasicBlock* member = graph_->blocks()->at(i);
       if (i != block->block_id() && member->IsLoopHeader()) {
         // Recursively compute and cache the effects of the nested loop.
         ASSERT(member->loop_information()->parent_loop() == loop);
         Effects* nested = ComputeLoopEffects(member);
         effects->Union(nested, zone_);
         // Skip the nested loop's blocks.
         i = member->loop_information()->GetLastBackEdge()->block_id();
       } else {
         // Process all the effects of the block.
+        if (member->IsUnreachable()) continue;
         ASSERT(member->current_loop() == loop);
         for (HInstructionIterator it(member); !it.Done(); it.Advance()) {
           effects->Process(it.Current(), zone_);
         }
       }
     }
     return effects;
   }
 
   inline bool SkipNonDominatedBlock(HBasicBlock* root, HBasicBlock* other) {
@@ skipping 35 matching lines @@
   ZoneList<int> pred_counts_;        // Finished predecessors (by block id).
 #endif
   ZoneList<State*> block_states_;    // Block states (by block id).
   ZoneList<Effects*> loop_effects_;  // Loop effects (by block id).
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_FLOW_ENGINE_H_