[vm] Fix --no-retain-function-objects when there are calls through Code.

With --no-use-bare-instructions or with splitting, not all calls are pc-relative. We must replace the Function with its Code in the static call table before detaching the Function's code as part of removing Function objects.

Also handle WeakSerializationReferences in AssignLoadingUnitsCodeVisitor.

Bug: https://github.com/dart-lang/sdk/issues/41974
Change-Id: I29f9258c240f5a2b1b8dca52f74146dfe44d6401
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/158165
Reviewed-by: Tess Strickland <sstrickl@google.com>
Commit-Queue: Ryan Macnak <rmacnak@google.com>

runtime/tests/vm/dart/deferred_loading_and_weak_serialization_references_test.dart

@@ -0,0 +1,16 @@
+// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// These flags can cause WeakSerializationReferences to replace the owner of
+// some Code, which must be accounted for in AssignLoadingUnitsCodeVisitor.
+
+// VMOptions=--no_retain_function_objects
+// VMOptions=--dwarf_stack_traces
+
+import "splay_test.dart" deferred as splay; // Some non-trivial code.
+
+main() async {
+  await splay.loadLibrary();
+  splay.main();
+}

runtime/tests/vm/dart_2/deferred_loading_and_weak_serialization_references_test.dart

@@ -0,0 +1,16 @@
+// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// These flags can cause WeakSerializationReferences to replace the owner of
+// some Code, which must be accounted for in AssignLoadingUnitsCodeVisitor.
+
+// VMOptions=--no_retain_function_objects
+// VMOptions=--dwarf_stack_traces
+
+import "splay_test.dart" deferred as splay; // Some non-trivial code.
+
+main() async {
+  await splay.loadLibrary();
+  splay.main();
+}

runtime/vm/compiler/aot/precompiler.cc

@@ -391,7 +391,7 @@ void Precompiler::DoCompileAll() {
 
       TraceForRetainedFunctions();
       FinalizeDispatchTable();
-      ReplaceFunctionPCRelativeCallEntries();
+      ReplaceFunctionStaticCallEntries();
 
       DropFunctions();
       DropFields();
@@ -1644,7 +1644,7 @@ void Precompiler::FinalizeDispatchTable() {
   printed.Release();
 }
 
-void Precompiler::ReplaceFunctionPCRelativeCallEntries() {
+void Precompiler::ReplaceFunctionStaticCallEntries() {
   class StaticCallTableEntryFixer : public CodeVisitor {
    public:
     explicit StaticCallTableEntryFixer(Zone* zone)
@@ -1660,7 +1660,9 @@ void Precompiler::ReplaceFunctionPCRelativeCallEntries() {
       for (auto& view : static_calls) {
         kind_and_offset_ = view.Get<Code::kSCallTableKindAndOffset>();
         auto const kind = Code::KindField::decode(kind_and_offset_.Value());
-        if (kind != Code::kPcRelativeCall) continue;
+
+        if ((kind != Code::kCallViaCode) && (kind != Code::kPcRelativeCall))
+          continue;
 
         target_function_ = view.Get<Code::kSCallTableFunctionTarget>();
         if (target_function_.IsNull()) continue;
@@ -1671,6 +1673,12 @@ void Precompiler::ReplaceFunctionPCRelativeCallEntries() {
         ASSERT(!target_code_.IsStubCode());
         view.Set<Code::kSCallTableCodeOrTypeTarget>(target_code_);
         view.Set<Code::kSCallTableFunctionTarget>(Object::null_function());
+        if (kind == Code::kCallViaCode) {
+          auto const pc_offset =
+              Code::OffsetField::decode(kind_and_offset_.Value());
+          const uword pc = pc_offset + code.PayloadStart();
+          CodePatcher::PatchStaticCallAt(pc, code, target_code_);
+        }
         if (FLAG_trace_precompiler) {
           THR_Print("Updated static call entry to %s in \"%s\"\n",
                     target_function_.ToFullyQualifiedCString(),

runtime/vm/compiler/aot/precompiler.h

@@ -301,7 +301,7 @@ class Precompiler : public ValueObject {
 
   void TraceForRetainedFunctions();
   void FinalizeDispatchTable();
-  void ReplaceFunctionPCRelativeCallEntries();
+  void ReplaceFunctionStaticCallEntries();
   void DropFunctions();
   void DropFields();
   void TraceTypesFromRetainedClasses();

runtime/vm/program_visitor.cc

@@ -368,8 +368,7 @@ void ProgramVisitor::BindStaticCalls(Zone* zone, Isolate* isolate) {
         if (target_.IsNull()) {
           target_ =
               Code::RawCast(view.Get<Code::kSCallTableCodeOrTypeTarget>());
-          ASSERT(!Code::Cast(target_).IsFunctionCode());
-          // Allocation stub or AllocateContext or AllocateArray or ...
+          ASSERT(!target_.IsNull());  // Already bound.
           continue;
         }
 
@@ -1314,7 +1313,7 @@ class AssignLoadingUnitsCodeVisitor : public CodeVisitor {
   void VisitCode(const Code& code) {
     intptr_t id;
     if (code.IsFunctionCode()) {
-      func_ ^= code.owner();
+      func_ ^= code.function();
       cls_ = func_.Owner();
       lib_ = cls_.library();
       unit_ = lib_.loading_unit();