Support StringLength in hydrogen (similar to ArrayLength).

src/arm/stub-cache-arm.cc

Index: src/arm/stub-cache-arm.cc
diff --git a/src/arm/stub-cache-arm.cc b/src/arm/stub-cache-arm.cc
index ce1d85448158d8b6d70728bcb633d5dbaa6b8d80..ee98d126158cdce64cd7e445897311f98b239ea2 100644
--- a/src/arm/stub-cache-arm.cc
+++ b/src/arm/stub-cache-arm.cc
@@ -370,27 +370,31 @@ void StubCompiler::GenerateLoadStringLength(MacroAssembler* masm,
                                             Register receiver,
                                             Register scratch1,
                                             Register scratch2,
-                                            Label* miss) {
+                                            Label* miss,
+                                            bool support_wrappers) {
   Label check_wrapper;
 
   // Check if the object is a string leaving the instance type in the
   // scratch1 register.
-  GenerateStringCheck(masm, receiver, scratch1, scratch2, miss, &check_wrapper);
+  GenerateStringCheck(masm, receiver, scratch1, scratch2, miss,
+                      support_wrappers ? &check_wrapper : miss);
 
   // Load length directly from the string.
   __ ldr(r0, FieldMemOperand(receiver, String::kLengthOffset));
   __ Ret();
 
-  // Check if the object is a JSValue wrapper.
-  __ bind(&check_wrapper);
-  __ cmp(scratch1, Operand(JS_VALUE_TYPE));
-  __ b(ne, miss);
+  if (support_wrappers) {
+    // Check if the object is a JSValue wrapper.
+    __ bind(&check_wrapper);
+    __ cmp(scratch1, Operand(JS_VALUE_TYPE));
+    __ b(ne, miss);
 
-  // Unwrap the value and check if the wrapped value is a string.
-  __ ldr(scratch1, FieldMemOperand(receiver, JSValue::kValueOffset));
-  GenerateStringCheck(masm, scratch1, scratch2, scratch2, miss, miss);
-  __ ldr(r0, FieldMemOperand(scratch1, String::kLengthOffset));
-  __ Ret();
+    // Unwrap the value and check if the wrapped value is a string.
+    __ ldr(scratch1, FieldMemOperand(receiver, JSValue::kValueOffset));
+    GenerateStringCheck(masm, scratch1, scratch2, scratch2, miss, miss);
+    __ ldr(r0, FieldMemOperand(scratch1, String::kLengthOffset));
+    __ Ret();
+  }
 }
 
 
@@ -2995,7 +2999,7 @@ MaybeObject* KeyedLoadStubCompiler::CompileLoadStringLength(String* name) {
   __ cmp(r0, Operand(Handle<String>(name)));
   __ b(ne, &miss);
 
-  GenerateLoadStringLength(masm(), r1, r2, r3, &miss);
+  GenerateLoadStringLength(masm(), r1, r2, r3, &miss, true);
   __ bind(&miss);
   __ DecrementCounter(&Counters::keyed_load_string_length, 1, r2, r3);