Implement control reducer, which reduces branches and phis together in a single fixpoint.

R=bmeurer@chromium.org
BUG=

Review URL: https://codereview.chromium.org/665223006

Cr-Commit-Position: refs/heads/master@{#24891}
git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24891 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/compiler/control-reducer.h

@@ -11,6 +11,7 @@ namespace compiler {
 
 class JSGraph;
 class CommonOperatorBuilder;
+class Node;
 
 class ControlReducer {
  public:
@@ -20,6 +21,16 @@ class ControlReducer {
 
   // Trim nodes in the graph that are not reachable from end.
   static void TrimGraph(Zone* zone, JSGraph* graph);
+
+  // Testing interface.
+  static Node* ReducePhiForTesting(JSGraph* graph,
+                                   CommonOperatorBuilder* builder, Node* node);
+  static Node* ReduceBranchForTesting(JSGraph* graph,
+                                      CommonOperatorBuilder* builder,
+                                      Node* node);
+  static Node* ReduceMergeForTesting(JSGraph* graph,
+                                     CommonOperatorBuilder* builder,
+                                     Node* node);
 };
 }
 }

src/compiler/operator-properties-inl.h

@@ -117,6 +117,7 @@ inline int OperatorProperties::GetEffectInputCount(const Operator* op) {
 }
 
 inline int OperatorProperties::GetControlInputCount(const Operator* op) {
+  // TODO(titzer): fix this mess; just make them a count on the operator.
   switch (op->opcode()) {
     case IrOpcode::kPhi:
     case IrOpcode::kEffectPhi:
@@ -127,8 +128,8 @@ inline int OperatorProperties::GetControlInputCount(const Operator* op) {
 #define OPCODE_CASE(x) case IrOpcode::k##x:
       CONTROL_OP_LIST(OPCODE_CASE)
 #undef OPCODE_CASE
-      // Branch operator is special
       if (op->opcode() == IrOpcode::kBranch) return 1;
+      if (op->opcode() == IrOpcode::kTerminate) return 1;
       // Control operators are Operator1<int>.
       return OpParameter<int>(op);
     default:

src/compiler/scheduler.cc

@@ -382,7 +382,8 @@ class CFGBuilder {
   }
 
   bool IsFinalMerge(Node* node) {
-    return (node == scheduler_->graph_->end()->InputAt(0));
+    return (node->opcode() == IrOpcode::kMerge &&
+            node == scheduler_->graph_->end()->InputAt(0));
   }
 };