Set the current context to the function's context when entering to LAP.

src/s390/code-stubs-s390.cc

Index: src/s390/code-stubs-s390.cc
diff --git a/src/s390/code-stubs-s390.cc b/src/s390/code-stubs-s390.cc
index 9893b12f80ebaed11d467e71003cda92f2978bc1..dc4f901c1581c8e7cbe044e64614cedb3e4f0e20 100644
--- a/src/s390/code-stubs-s390.cc
+++ b/src/s390/code-stubs-s390.cc
@@ -2838,8 +2838,9 @@ void CallApiCallbackStub::Generate(MacroAssembler* masm) {
   //  --
   //  -- sp[0]               : last argument
   //  -- ...
-  //  -- sp[(argc - 1)* 4]   : first argument
+  //  -- sp[(argc - 1) * 4]  : first argument
   //  -- sp[argc * 4]        : receiver
+  //  -- sp[(argc + 1) * 4]  : accessor_holder
   // -----------------------------------
 
   Register callee = r2;
@@ -2865,10 +2866,6 @@ void CallApiCallbackStub::Generate(MacroAssembler* masm) {
 
   // context save
   __ push(context);
-  if (!is_lazy()) {
-    // load context from callee
-    __ LoadP(context, FieldMemOperand(callee, JSFunction::kContextOffset));
-  }
 
   // callee
   __ push(callee);
@@ -2876,7 +2873,20 @@ void CallApiCallbackStub::Generate(MacroAssembler* masm) {
   // call data
   __ push(call_data);
 
+  // Enter a new context
   Register scratch = call_data;
+  if (is_lazy()) {
+    // Load context from accessor_holder
+    Register accessor_holder = context;
+    __ LoadP(accessor_holder, MemOperand(sp, (argc() + 1 + 4) * kPointerSize));
+    __ LoadP(scratch, FieldMemOperand(accessor_holder, HeapObject::kMapOffset));
+    __ GetMapConstructor(scratch, scratch, context, callee);
+    __ LoadP(context, FieldMemOperand(scratch, JSFunction::kContextOffset));
+  } else {
+    // Load context from callee
+    __ LoadP(context, FieldMemOperand(callee, JSFunction::kContextOffset));
+  }
+
   __ LoadRoot(scratch, Heap::kUndefinedValueRootIndex);
   // return value
   __ push(scratch);