[hydrogen] optimize switch with string clauses

src/x64/lithium-x64.h

Index: src/x64/lithium-x64.h
diff --git a/src/x64/lithium-x64.h b/src/x64/lithium-x64.h
index b542071b7ed1c6a95f1daf9a3db6a5c90cc1007d..101000227736727e25bbf11fcc57b32484f22c58 100644
--- a/src/x64/lithium-x64.h
+++ b/src/x64/lithium-x64.h
@@ -109,8 +109,10 @@ class LCodeGen;
   V(IsConstructCallAndBranch)                   \
   V(IsNilAndBranch)                             \
   V(IsObjectAndBranch)                          \
+  V(IsStringAndBranch)                          \
   V(IsSmiAndBranch)                             \
   V(IsUndetectableAndBranch)                    \
+  V(StringCompareAndBranch)                    \
   V(JSArrayLength)                              \
   V(Label)                                      \
   V(LazyBailout)                                \
@@ -640,6 +642,19 @@ class LIsObjectAndBranch: public LControlInstruction<1, 0> {
 };
 
 
+class LIsStringAndBranch: public LControlInstruction<1, 0> {
+ public:
+  explicit LIsStringAndBranch(LOperand* value) {
+    inputs_[0] = value;
+  }
+
+  DECLARE_CONCRETE_INSTRUCTION(IsStringAndBranch, "is-string-and-branch")
+  DECLARE_HYDROGEN_ACCESSOR(IsStringAndBranch)
+
+  virtual void PrintDataTo(StringStream* stream);
+};
+
+
 class LIsSmiAndBranch: public LControlInstruction<1, 0> {
  public:
   explicit LIsSmiAndBranch(LOperand* value) {
@@ -668,6 +683,23 @@ class LIsUndetectableAndBranch: public LControlInstruction<1, 1> {
 };
 
 
+class LStringCompareAndBranch: public LControlInstruction<2, 0> {
+ public:
+  explicit LStringCompareAndBranch(LOperand* left, LOperand* right) {
+    inputs_[0] = left;
+    inputs_[1] = right;
+  }
+
+  DECLARE_CONCRETE_INSTRUCTION(StringCompareAndBranch,
+                               "compare-generic-and-branch")
+  DECLARE_HYDROGEN_ACCESSOR(StringCompareAndBranch)
+
+  virtual void PrintDataTo(StringStream* stream);
+
+  Token::Value op() const { return hydrogen()->token(); }
+};
+
+
 class LHasInstanceTypeAndBranch: public LControlInstruction<1, 0> {
  public:
   explicit LHasInstanceTypeAndBranch(LOperand* value) {