Add ability to do "else-if" clauses in IfBuilder

src/hydrogen.h

Index: src/hydrogen.h
diff --git a/src/hydrogen.h b/src/hydrogen.h
index 8f4878d93e9c065bad1b36579099cd64d08fa8c9..89274a5991fefe92bef6b600f6f85e4ec61a4832 100644
--- a/src/hydrogen.h
+++ b/src/hydrogen.h
@@ -1463,6 +1463,10 @@ class HGraphBuilder {
     void JoinContinuation(HIfContinuation* continuation);
 
     void Then();
+    void ThenDeopt(const char* reason) {

[Michael Starzinger, 2013/11/12 09:50:00]

nit: Let's move that down to line 1474 into the block with the other deopts.

[danno, 2013/11/14 14:46:40]

Done.

+      Then();
+      Deopt(reason);
+    }
     void Else();
     void End();
 
@@ -1479,21 +1483,58 @@ class HGraphBuilder {
 
     HGraphBuilder* builder() const { return builder_; }
 
+    void AddMergeAtJoinBlock(bool deopt) {
+      if (!pending_merge_block_) return;
+      HBasicBlock* block = builder_->current_block();
+      ASSERT(block == NULL || !block->IsFinished());
+      MergeAtJoinBlock* record =
+        new(builder_->zone()) MergeAtJoinBlock(block, deopt,
+                                               merge_at_join_blocks_);
+      merge_at_join_blocks_ = record;
+      if (block != NULL) {
+        if (deopt) {
+          normal_merge_at_join_block_count_++;
+        } else {
+          deopt_merge_at_join_block_count_++;
+        }
+      }
+      builder_->set_current_block(NULL);
+      pending_merge_block_ = false;
+    }
+
+    void Finish();
+    void Finish(HBasicBlock** then_continuation,
+                HBasicBlock** else_continuation);
+
+    class MergeAtJoinBlock : public ZoneObject {
+     public:
+      MergeAtJoinBlock(HBasicBlock* block,
+                       bool deopt,
+                       MergeAtJoinBlock* next)
+        : block_(block),
+          deopt_(deopt),
+          next_(next) {}
+      HBasicBlock* block_;
+      bool deopt_;
+      MergeAtJoinBlock* next_;
+    };
+
     HGraphBuilder* builder_;
     bool finished_ : 1;
-    bool deopt_then_ : 1;
-    bool deopt_else_ : 1;
     bool did_then_ : 1;
     bool did_else_ : 1;
+    bool did_else_if_ : 1;
     bool did_and_ : 1;
     bool did_or_ : 1;
     bool captured_ : 1;
     bool needs_compare_ : 1;
+    bool pending_merge_block_ : 1;
     HBasicBlock* first_true_block_;
-    HBasicBlock* last_true_block_;
     HBasicBlock* first_false_block_;
     HBasicBlock* split_edge_merge_block_;
-    HBasicBlock* merge_block_;
+    MergeAtJoinBlock* merge_at_join_blocks_;
+    int normal_merge_at_join_block_count_;
+    int deopt_merge_at_join_block_count_;
   };
 
   class LoopBuilder V8_FINAL {