[turbofan] Properly deal with out-of-bounds fields in EscapeAnalysis.

src/compiler/escape-analysis.cc

Index: src/compiler/escape-analysis.cc
diff --git a/src/compiler/escape-analysis.cc b/src/compiler/escape-analysis.cc
index a190a5adc0ecb14cf0c0996765be9a16ee050990..f175bd5e81af93ae01cace9451f2c91a96c3943c 100644
--- a/src/compiler/escape-analysis.cc
+++ b/src/compiler/escape-analysis.cc
@@ -1399,7 +1399,20 @@ void EscapeAnalysis::ProcessLoadField(Node* node) {
   if (VirtualObject* object = GetVirtualObject(state, from)) {
     if (!object->IsTracked()) return;
     int offset = OffsetForFieldAccess(node);
-    if (static_cast<size_t>(offset) >= object->field_count()) return;
+    if (static_cast<size_t>(offset) >= object->field_count()) {
+      // We have a load from a field that is not inside the {object}. This
+      // can only happen with conflicting type feedback and for dead {node}s.
+      // For now, we just mark the {object} as escaping.
+      // TODO(turbofan): Consider introducing an Undefined or None operator
+      // that we can replace this load with, since we know it's dead code.
+      if (status_analysis_->SetEscaped(from)) {
+        TRACE(
+            "Setting #%d (%s) to escaped because load field #%d from "
+            "offset %d outside of object\n",
+            from->id(), from->op()->mnemonic(), node->id(), offset);
+      }
+      return;
+    }
     Node* value = object->GetField(offset);
     if (value) {
       value = ResolveReplacement(value);
@@ -1464,7 +1477,20 @@ void EscapeAnalysis::ProcessStoreField(Node* node) {
   if (VirtualObject* object = GetVirtualObject(state, to)) {
     if (!object->IsTracked()) return;
     int offset = OffsetForFieldAccess(node);
-    if (static_cast<size_t>(offset) >= object->field_count()) return;
+    if (static_cast<size_t>(offset) >= object->field_count()) {
+      // We have a store to a field that is not inside the {object}. This
+      // can only happen with conflicting type feedback and for dead {node}s.
+      // For now, we just mark the {object} as escaping.
+      // TODO(turbofan): Consider just eliminating the store in the reducer
+      // pass, as it's dead code anyways.
+      if (status_analysis_->SetEscaped(to)) {
+        TRACE(
+            "Setting #%d (%s) to escaped because store field #%d to "
+            "offset %d outside of object\n",
+            to->id(), to->op()->mnemonic(), node->id(), offset);
+      }
+      return;
+    }
     Node* val = ResolveReplacement(NodeProperties::GetValueInput(node, 1));
     // TODO(mstarzinger): The following is a workaround to not track some well
     // known raw fields. We only ever store default initial values into these