Revert "Changing string length field type from int to SMI."

src/x64/stub-cache-x64.cc

Index: src/x64/stub-cache-x64.cc
diff --git a/src/x64/stub-cache-x64.cc b/src/x64/stub-cache-x64.cc
index 8b36f9ee5c417e78fcb148ceef755b6cd24e78c8..a78f8b11b424bd2da551354c58aae1a61367116a 100644
--- a/src/x64/stub-cache-x64.cc
+++ b/src/x64/stub-cache-x64.cc
@@ -327,7 +327,8 @@ void StubCompiler::GenerateLoadStringLength(MacroAssembler* masm,
   GenerateStringCheck(masm, receiver, scratch1, miss, &check_wrapper);
 
   // Load length directly from the string.
-  __ movq(rax, FieldOperand(receiver, String::kLengthOffset));
+  __ movl(rax, FieldOperand(receiver, String::kLengthOffset));
+  __ Integer32ToSmi(rax, rax);
   __ ret(0);
 
   // Check if the object is a JSValue wrapper.
@@ -339,7 +340,8 @@ void StubCompiler::GenerateLoadStringLength(MacroAssembler* masm,
   // directly if it is.
   __ movq(scratch2, FieldOperand(receiver, JSValue::kValueOffset));
   GenerateStringCheck(masm, scratch2, scratch1, miss, miss);
-  __ movq(rax, FieldOperand(scratch2, String::kLengthOffset));
+  __ movl(rax, FieldOperand(scratch2, String::kLengthOffset));
+  __ Integer32ToSmi(rax, rax);
   __ ret(0);
 }