Bring r5483 "Fix direct loading of global function prototypes" to 2.2.

src/x64/stub-cache-x64.cc

Index: src/x64/stub-cache-x64.cc
===================================================================
--- src/x64/stub-cache-x64.cc	(revision 5484)
+++ src/x64/stub-cache-x64.cc	(working copy)
@@ -215,7 +215,12 @@
 
 
 void StubCompiler::GenerateDirectLoadGlobalFunctionPrototype(
-    MacroAssembler* masm, int index, Register prototype) {
+    MacroAssembler* masm, int index, Register prototype, Label* miss) {
+  // Check we're still in the same context.
+  __ Move(prototype, Top::global());
+  __ cmpq(Operand(rsi, Context::SlotOffset(Context::GLOBAL_INDEX)),
+          prototype);
+  __ j(not_equal, miss);
   // Get the global function with the given index.
   JSFunction* function = JSFunction::cast(Top::global_context()->get(index));
   // Load its initial map. The global functions all have initial maps.
@@ -910,7 +915,7 @@
         __ j(above_equal, &miss);
         // Check that the maps starting from the prototype haven't changed.
         GenerateDirectLoadGlobalFunctionPrototype(
-            masm(), Context::STRING_FUNCTION_INDEX, rax);
+            masm(), Context::STRING_FUNCTION_INDEX, rax, &miss);
         CheckPrototypes(JSObject::cast(object->GetPrototype()), rax, holder,
                         rbx, rdx, rdi, name, &miss);
       }
@@ -929,7 +934,7 @@
         __ bind(&fast);
         // Check that the maps starting from the prototype haven't changed.
         GenerateDirectLoadGlobalFunctionPrototype(
-            masm(), Context::NUMBER_FUNCTION_INDEX, rax);
+            masm(), Context::NUMBER_FUNCTION_INDEX, rax, &miss);
         CheckPrototypes(JSObject::cast(object->GetPrototype()), rax, holder,
                         rbx, rdx, rdi, name, &miss);
       }
@@ -950,7 +955,7 @@
         __ bind(&fast);
         // Check that the maps starting from the prototype haven't changed.
         GenerateDirectLoadGlobalFunctionPrototype(
-            masm(), Context::BOOLEAN_FUNCTION_INDEX, rax);
+            masm(), Context::BOOLEAN_FUNCTION_INDEX, rax, &miss);
         CheckPrototypes(JSObject::cast(object->GetPrototype()), rax, holder,
                         rbx, rdx, rdi, name, &miss);
       }