[regexp] Remove remainder of native RegExpExecStub

src/regexp/regexp-macro-assembler.cc

Index: src/regexp/regexp-macro-assembler.cc
diff --git a/src/regexp/regexp-macro-assembler.cc b/src/regexp/regexp-macro-assembler.cc
index 2e3a8a2f76877eb90bac9dd699ae03ba1e86a505..755b604f8c02fd52b2b43bd529f94d1fd451b13f 100644
--- a/src/regexp/regexp-macro-assembler.cc
+++ b/src/regexp/regexp-macro-assembler.cc
@@ -170,15 +170,18 @@ int NativeRegExpMacroAssembler::CheckStackGuardState(
   bool is_one_byte = subject_handle->IsOneByteRepresentationUnderneath();
 
   StackLimitCheck check(isolate);
-  if (check.JsHasOverflowed()) {
+  bool js_has_overflowed = check.JsHasOverflowed();
+
+  if (is_direct_call) {
+    // Direct calls from JavaScript can be interrupted in two ways:
+    // 1. A real stack overflow, in which case we let the caller throw the
+    //    exception.
+    // 2. The stack guard was used to interrupt execution for another purpose,
+    //    forcing the call through the runtime system.
+    return_value = js_has_overflowed ? EXCEPTION : RETRY;
+  } else if (js_has_overflowed) {
     isolate->StackOverflow();
     return_value = EXCEPTION;
-  } else if (is_direct_call) {
-    // If not real stack overflow the stack guard was used to interrupt
-    // execution for another purpose.  If this is a direct call from JavaScript
-    // retry the RegExp forcing the call through the runtime system.
-    // Currently the direct call cannot handle a GC.
-    return_value = RETRY;
   } else {
     Object* result = isolate->stack_guard()->HandleInterrupts();
     if (result->IsException(isolate)) return_value = EXCEPTION;