Handle string + number in hydrogen.

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index 45fbbc09821824998595b84291389a3bf214bfd0..4bfb91c1108245716adbbb6f19c1f32b49ead887 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -1283,8 +1283,7 @@ void HGraphBuilder::BuildTransitionElementsKind(HValue* object,
 
 
 HValue* HGraphBuilder::BuildLookupNumberStringCache(
-    HValue* object,
-    HIfContinuation* continuation) {
+    HValue* object, ToStringMode mode, HIfContinuation* continuation) {
   // Create a joinable continuation.
   HIfContinuation found(graph()->CreateBasicBlock(),
                         graph()->CreateBasicBlock());
@@ -1366,6 +1365,10 @@ HValue* HGraphBuilder::BuildLookupNumberStringCache(
         }
         if_keyeqobject.JoinContinuation(&found);
       }
+      if (mode == CHECK_NUMBER) {
+        if_objectisnumber.Else();
+        if_objectisnumber.Deopt("Expected Argument to be Numeric");
+      }
       if_keyisnumber.JoinContinuation(&found);
     }
     if_objectisnumber.JoinContinuation(&found);
@@ -1391,12 +1394,12 @@ HValue* HGraphBuilder::BuildLookupNumberStringCache(
 }
 
 
-HValue* HGraphBuilder::BuildNumberToString(HValue* number) {
+HValue* HGraphBuilder::BuildNumberToString(HValue* number, ToStringMode mode) {
   NoObservableSideEffectsScope scope(this);
 
   // Lookup the number in the number string cache.
   HIfContinuation continuation;
-  HValue* value = BuildLookupNumberStringCache(number, &continuation);
+  HValue* value = BuildLookupNumberStringCache(number, mode, &continuation);
   IfBuilder if_found(this, &continuation);
   if_found.Then();
 
@@ -7909,17 +7912,25 @@ HInstruction* HGraphBuilder::BuildBinaryOperation(
     switch (op) {
       case Token::ADD:
         if (is_string_add) {
-          StringAddFlags flags = STRING_ADD_CHECK_BOTH;
+          StringAddFlags flags = STRING_ADD_CHECK_NONE;
           if (left_type->Is(Type::String())) {
             BuildCheckHeapObject(left);
             AddInstruction(HCheckInstanceType::NewIsString(left, zone()));
-            flags = STRING_ADD_CHECK_RIGHT;
+            if (right_type->Is(Type::Number())) {
+              right = BuildNumberToString(right, CHECK_NUMBER);
+            } else {
+              flags = STRING_ADD_CHECK_RIGHT;
+            }
           }
           if (right_type->Is(Type::String())) {
+            if (left_type->Is(Type::Number())) {
+              left = BuildNumberToString(left, CHECK_NUMBER);
+            } else {
+              flags = (flags == STRING_ADD_CHECK_RIGHT)
+                  ? STRING_ADD_CHECK_NONE : STRING_ADD_CHECK_LEFT;
+            }
             BuildCheckHeapObject(right);
             AddInstruction(HCheckInstanceType::NewIsString(right, zone()));
-            flags = (flags == STRING_ADD_CHECK_BOTH)
-                ? STRING_ADD_CHECK_LEFT : STRING_ADD_CHECK_NONE;
           }
           instr = NewUncasted<HStringAdd>(left, right, flags);
         } else {
@@ -9124,7 +9135,7 @@ void HOptimizedGraphBuilder::GenerateNumberToString(CallRuntime* call) {
   ASSERT_EQ(1, call->arguments()->length());
   CHECK_ALIVE(VisitForValue(call->arguments()->at(0)));
   HValue* number = Pop();
-  HValue* result = BuildNumberToString(number);
+  HValue* result = BuildNumberToString(number, ALLOW_SIDE_EFFECTS);
   return ast_context()->ReturnValue(result);
 }