Polymorphic calls in precompilation invoke megamorphic calls when tests fail (instead of deoptimizi…

runtime/vm/flow_graph_compiler_arm64.cc

Index: runtime/vm/flow_graph_compiler_arm64.cc
diff --git a/runtime/vm/flow_graph_compiler_arm64.cc b/runtime/vm/flow_graph_compiler_arm64.cc
index 53429c8bda2bc2b539b327a3997b8030ee407e35..09800a9ec68719f99f45a8cdb2f097ac18763f69 100644
--- a/runtime/vm/flow_graph_compiler_arm64.cc
+++ b/runtime/vm/flow_graph_compiler_arm64.cc
@@ -28,6 +28,18 @@ DECLARE_FLAG(bool, enable_simd_inline);
 DECLARE_FLAG(bool, use_megamorphic_stub);
 
 
+void MegamorphicSlowPath::EmitNativeCode(FlowGraphCompiler* compiler) {
+  Assembler* assem = compiler->assembler();
+#define __ assem->
+  __ Bind(entry_label());
+  __ Comment("MegamorphicSlowPath");
+  compiler->EmitMegamorphicInstanceCall(ic_data_, argument_count_, deopt_id_,
+                                        token_pos_, locs_, try_index_);
+  __ b(exit_label());
+#undef __
+}
+
+
 FlowGraphCompiler::~FlowGraphCompiler() {
   // BlockInfos are zone-allocated, so their destructors are not called.
   // Verify the labels explicitly here.
@@ -1248,7 +1260,8 @@ void FlowGraphCompiler::EmitMegamorphicInstanceCall(
     intptr_t argument_count,
     intptr_t deopt_id,
     intptr_t token_pos,
-    LocationSummary* locs) {
+    LocationSummary* locs,
+    intptr_t try_index) {
   const String& name = String::Handle(zone(), ic_data.target_name());
   const Array& arguments_descriptor =
       Array::ZoneHandle(zone(), ic_data.arguments_descriptor());
@@ -1270,7 +1283,18 @@ void FlowGraphCompiler::EmitMegamorphicInstanceCall(
       Thread::kNoDeoptId, token_pos);
   RecordSafepoint(locs);
   const intptr_t deopt_id_after = Thread::ToDeoptAfter(deopt_id);
-  if (is_optimizing()) {
+  if (Compiler::always_optimize()) {
+    // Megamorphic calls may occur in slow path stubs.
+    // If valid use try_index argument.
+    if (try_index == CatchClauseNode::kInvalidTryIndex) {
+      try_index = CurrentTryIndex();
+    }
+    pc_descriptors_list()->AddDescriptor(RawPcDescriptors::kOther,
+                                         assembler()->CodeSize(),
+                                         Thread::kNoDeoptId,
+                                         token_pos,
+                                         try_index);
+  } else if (is_optimizing()) {
     AddDeoptIndexAtCall(deopt_id_after, token_pos);
   } else {
     // Add deoptimization continuation point after the call and before the