[builtins] Add --print-embedded-builtin-candidates

When enabled, this will print all builtins that could, in theory, be
marked as isolate-independent (because their reloc info only contains
viable entries), but are not. This is only intended for use while
implementing embedded builtins on ia32 and can be removed afterwards.

Bug: v8:6666
Change-Id: I2cb54c851391480824f15f6e5ddb7919e179da4a
Reviewed-on: https://chromium-review.googlesource.com/1183222Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55264}

src/flag-definitions.h

@@ -1081,6 +1081,9 @@ DEFINE_VALUE_IMPLICATION(runtime_call_stats, runtime_stats, 1)
 #endif
 DEFINE_BOOL_READONLY(embedded_builtins, V8_EMBEDDED_BUILTINS_BOOL,
                      "Embed builtin code into the binary.")
+// TODO(jgruber,v8:6666): Remove once ia32 has full embedded builtin support.
+DEFINE_BOOL(print_embedded_builtin_candidates, false,
+            "Prints builtins that are not yet embedded but could be.")
 DEFINE_BOOL(lazy_deserialization, true,
             "Deserialize code lazily from the snapshot.")
 DEFINE_BOOL(lazy_handler_deserialization, true,

src/isolate.cc

@@ -2884,6 +2884,19 @@ void CreateOffHeapTrampolines(Isolate* isolate) {
     }
   }
 }
+
+void PrintEmbeddedBuiltinCandidates(Isolate* isolate) {
+  CHECK(FLAG_print_embedded_builtin_candidates);
+  bool found_a_candidate = false;
+  for (int i = 0; i < Builtins::builtin_count; i++) {
+    if (Builtins::IsIsolateIndependent(i)) continue;
+    Code* builtin = isolate->heap()->builtin(i);
+    if (!builtin->IsIsolateIndependent(isolate)) continue;
+    if (!found_a_candidate) PrintF("Found embedded builtin candidates:\n");
+    found_a_candidate = true;
+    PrintF("  %s\n", Builtins::name(i));
+  }
+}
 }  // namespace
 
 void Isolate::PrepareEmbeddedBlobForSerialization() {
@@ -3045,6 +3058,9 @@ bool Isolate::Init(StartupDeserializer* des) {
   setup_delegate_ = nullptr;
 
   if (FLAG_print_builtin_size) PrintBuiltinSizes(this);
+  if (FLAG_print_embedded_builtin_candidates) {
+    PrintEmbeddedBuiltinCandidates(this);
+  }
 
   // Finish initialization of ThreadLocal after deserialization is done.
   clear_pending_exception();