[WIP] Initial CallFunctionCallback builtin.

src/mips/code-stubs-mips.cc

Index: src/mips/code-stubs-mips.cc
diff --git a/src/mips/code-stubs-mips.cc b/src/mips/code-stubs-mips.cc
index 0fcdafca21d8321b86f5dd248382c71c63b31fa4..232e3605697758108c6f089edd616b19efc52ca1 100644
--- a/src/mips/code-stubs-mips.cc
+++ b/src/mips/code-stubs-mips.cc
@@ -2795,11 +2795,6 @@ void InternalArrayConstructorStub::Generate(MacroAssembler* masm) {
   GenerateCase(masm, FAST_ELEMENTS);
 }
 
-static int AddressOffset(ExternalReference ref0, ExternalReference ref1) {
-  return ref0.address() - ref1.address();
-}
-
-
 // Calls an API function.  Allocates HandleScope, extracts returned value
 // from handle and propagates exceptions.  Restores context.  stack_space
 // - space to be unwound on exit (includes the call JS arguments space and
@@ -2911,6 +2906,9 @@ static void CallApiFunctionAndReturn(
   __ lw(t1, MemOperand(at));
   __ Branch(&promote_scheduled_exception, ne, t0, Operand(t1));
 
+  // Check if the function returned a valid JavaScript value.
+  __ AssertApiCallResult(v0);
+
   __ Ret();
 
   // Re-throw by promoting a scheduled exception.
@@ -2980,6 +2978,12 @@ void CallApiCallbackStub::Generate(MacroAssembler* masm) {
   // Push isolate and holder.
   __ Push(scratch, holder);
 
+  if (!is_store()) {
+    __ li(a0, Operand(argc()));
+    __ Jump(masm->isolate()->builtins()->CallFunctionCallback(),
+            RelocInfo::CODE_TARGET);
+  }
+
   // Prepare arguments.
   __ mov(scratch, sp);