[compiler] Make root detection thread-safe.

... by only looking at the handle.

This is in preparation for running code generation off the main thread.

Bug: v8:6048
Change-Id: I19b105c13278a2821a0b2395033e54abf5552a43
Reviewed-on: https://chromium-review.googlesource.com/506190Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45333}

src/compiler/code-generator.cc

@@ -299,12 +299,9 @@ bool CodeGenerator::IsMaterializableFromRoot(
   const CallDescriptor* incoming_descriptor =
       linkage()->GetIncomingDescriptor();
   if (incoming_descriptor->flags() & CallDescriptor::kCanUseRoots) {
-    RootIndexMap map(isolate());
-    int root_index = map.Lookup(*object);
-    if (root_index != RootIndexMap::kInvalidRootIndex) {
-      *index_return = static_cast<Heap::RootListIndex>(root_index);
-      return true;
-    }
+    Heap* heap = isolate()->heap();
+    return heap->IsRootHandle(object, index_return) &&
+           heap->RootCanBeTreatedAsConstant(*index_return);
   }
   return false;
 }

tools/v8heapconst.py

@@ -237,14 +237,14 @@ KNOWN_MAPS = {
   0x03e31: (188, "ExternalMap"),
   0x03e89: (106, "NativeSourceStringMap"),
   0x03ee1: (152, "InterceptorInfoMap"),
-  0x03f39: (204, "JSPromiseCapabilityMap"),
-  0x03f91: (149, "AccessorInfoMap"),
-  0x03fe9: (150, "AccessorPairMap"),
-  0x04041: (151, "AccessCheckInfoMap"),
-  0x04099: (153, "FunctionTemplateInfoMap"),
-  0x040f1: (154, "ObjectTemplateInfoMap"),
-  0x04149: (155, "AllocationSiteMap"),
-  0x041a1: (156, "AllocationMementoMap"),
+  0x03f39: (156, "AllocationMementoMap"),
+  0x03f91: (204, "JSPromiseCapabilityMap"),
+  0x03fe9: (149, "AccessorInfoMap"),
+  0x04041: (150, "AccessorPairMap"),
+  0x04099: (151, "AccessCheckInfoMap"),
+  0x040f1: (153, "FunctionTemplateInfoMap"),
+  0x04149: (154, "ObjectTemplateInfoMap"),
+  0x041a1: (155, "AllocationSiteMap"),
   0x041f9: (158, "AliasedArgumentsEntryMap"),
   0x04251: (159, "PromiseResolveThenableJobInfoMap"),
   0x042a9: (160, "PromiseReactionJobInfoMap"),