Revert "[vm/aot] Remove object wrapping of bare instructions for AOT snapshots."

This reverts commit 7475c637c3.

Reason for revert: Breakage on simarm_x64 (and thus arm_x64)

Original change's description:
> [vm/aot] Remove object wrapping of bare instructions for AOT snapshots.
> 
> Now, when writing an AOT snapshot in bare instructions mode, only
> the actual instructions in the RawInstructions payload are serialized
> instead of the entire RawInstructions object.
> 
> Since there are no longer RawInstructions objects in these AOT
> snapshots, we also change how Code objects are serialized. Instead
> of just containing a reference to the RawInstructions object, we
> serialize two pieces of information: where the instructions
> payload for this Code object begins and whether there was a single
> entry for the instructions payload. (To save space, the single
> entry bit is serialized as the low order bit of the unchecked
> offset, which was already being serialized).
> 
> While we also need the length of the instructions payload, we
> approximate it for all but the last Code object by subtracting
> the next Code object's payload start from this Code object's
> payload start. For the last Code object, we assume it extends
> to the end of the instructions image.
> 
> Changes on flutter gallery in release mode:
> armv7: instructions size -2.66%, total size -1.68%
> armv8: instructions size -5.81%, total size -3.49%
> 
> Fixes https://github.com/dart-lang/sdk/issues/38451.
> 
> Change-Id: Ia458e8d99bae18f5c3b6e849df2519027f06f574
> Cq-Include-Trybots: luci.dart.try:vm-kernel-precomp-linux-release-x64-try,vm-kernel-precomp-linux-release-simarm-try,vm-kernel-precomp-linux-release-simarm64-try,vm-kernel-precomp-linux-release-simarm_x64-try,vm-kernel-precomp-android-release-arm64-try,vm-kernel-precomp-android-release-arm_x64-try,vm-kernel-precomp-mac-release-simarm64-try,vm-kernel-precomp-win-release-x64-try
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/131067
> Commit-Queue: Teagan Strickland <sstrickl@google.com>
> Reviewed-by: Martin Kustermann <kustermann@google.com>

TBR=kustermann@google.com,rmacnak@google.com,sstrickl@google.com

Change-Id: If2c8ca6b0993211b2509b275af7ff11a8fa2baa3
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Cq-Include-Trybots: luci.dart.try:vm-kernel-precomp-linux-release-x64-try, vm-kernel-precomp-linux-release-simarm-try, vm-kernel-precomp-linux-release-simarm64-try, vm-kernel-precomp-linux-release-simarm_x64-try, vm-kernel-precomp-android-release-arm64-try, vm-kernel-precomp-android-release-arm_x64-try, vm-kernel-precomp-mac-release-simarm64-try, vm-kernel-precomp-win-release-x64-try
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/134322
Reviewed-by: Teagan Strickland <sstrickl@google.com>
Commit-Queue: Teagan Strickland <sstrickl@google.com>

runtime/tests/vm/dart/v8_snapshot_profile_writer_test.dart

@@ -11,12 +11,7 @@ import "package:vm/v8_snapshot_profile.dart";
 
 import 'use_flag_test_helper.dart';
 
-test(
+test({String dillPath, bool useAsm, bool stripFlag, bool stripUtil}) async {
-    {String dillPath,
-    bool useAsm,
-    bool useBare,
-    bool stripFlag,
-    bool stripUtil}) async {
   // The assembler may add extra unnecessary information to the compiled
   // snapshot whether or not we generate DWARF information in the assembly, so
   // we force the use of a utility when generating assembly.
@@ -28,7 +23,6 @@ test(
 
   final tempDirPrefix = 'v8-snapshot-profile' +
       (useAsm ? '-assembly' : '-elf') +
-      (useBare ? '-bare' : '-nonbare') +
       (stripFlag ? '-intstrip' : '') +
       (stripUtil ? '-extstrip' : '');
 
@@ -38,7 +32,6 @@ test(
     final snapshotPath = path.join(tempDir, 'test.snap');
     final commonSnapshotArgs = [
       if (stripFlag) '--strip',
-      useBare ? '--use-bare-instructions' : '--no-use-bare-instructions',
       "--write-v8-snapshot-profile-to=$profilePath",
       dillPath,
     ];
@@ -78,7 +71,7 @@ test(
     // graph (in some cases the shallow size can legitimately be 0, e.g. for
     // "base objects").
     for (final int node in profile.nodes) {
-      Expect.notEquals("Unknown", profile[node].type,
+      Expect.notEquals(profile[node].type, "Unknown",
           "unknown node at ID ${profile[node].id}");
     }
 
@@ -96,7 +89,6 @@ test(
     final actual = await File(strippedPath).length();
     final expected = profile.accountedBytes;
 
-    final bareUsed = useBare ? "bare" : "non-bare";
     final fileType = useAsm ? "assembly" : "ELF";
     String stripPrefix = "";
     if (stripFlag && stripUtil) {
@@ -108,7 +100,7 @@ test(
     }
 
     Expect.approxEquals(expected, actual, 0.03 * actual,
-        "failed on $bareUsed $stripPrefix$fileType snapshot type.");
+        "failed on $stripPrefix$fileType snapshot type.");
   });
 }
 
@@ -222,17 +214,7 @@ main() async {
 
     // Test stripped ELF generation directly.
     await test(
-        dillPath: dillPath,
+        dillPath: dillPath, stripFlag: true, stripUtil: false, useAsm: false);
-        stripFlag: true,
-        stripUtil: false,
-        useAsm: false,
-        useBare: false);
-    await test(
-        dillPath: dillPath,
-        stripFlag: true,
-        stripUtil: false,
-        useAsm: false,
-        useBare: true);
 
     // We neither generate assembly nor have a stripping utility on Windows.
     if (Platform.isWindows) {
@@ -246,17 +228,7 @@ main() async {
     } else {
       // Test unstripped ELF generation that is then stripped externally.
       await test(
-          dillPath: dillPath,
+          dillPath: dillPath, stripFlag: false, stripUtil: true, useAsm: false);
-          stripFlag: false,
-          stripUtil: true,
-          useAsm: false,
-          useBare: false);
-      await test(
-          dillPath: dillPath,
-          stripFlag: false,
-          stripUtil: true,
-          useAsm: false,
-          useBare: true);
     }
 
     // TODO(sstrickl): Currently we can't assemble for SIMARM64 on MacOSX.
@@ -269,29 +241,9 @@ main() async {
 
     // Test stripped assembly generation that is then compiled and stripped.
     await test(
-        dillPath: dillPath,
+        dillPath: dillPath, stripFlag: true, stripUtil: true, useAsm: true);
-        stripFlag: true,
-        stripUtil: true,
-        useAsm: true,
-        useBare: false);
-    await test(
-        dillPath: dillPath,
-        stripFlag: true,
-        stripUtil: true,
-        useAsm: true,
-        useBare: true);
     // Test unstripped assembly generation that is then compiled and stripped.
     await test(
-        dillPath: dillPath,
+        dillPath: dillPath, stripFlag: false, stripUtil: true, useAsm: true);
-        stripFlag: false,
-        stripUtil: true,
-        useAsm: true,
-        useBare: false);
-    await test(
-        dillPath: dillPath,
-        stripFlag: false,
-        stripUtil: true,
-        useAsm: true,
-        useBare: true);
   });
 }

runtime/vm/class_id.h

@@ -28,7 +28,6 @@ namespace dart {
   V(Code)                                                                      \
   V(Bytecode)                                                                  \
   V(Instructions)                                                              \
-  V(InstructionsSection)                                                       \
   V(ObjectPool)                                                                \
   V(PcDescriptors)                                                             \
   V(CodeSourceMap)                                                             \

runtime/vm/clustered_snapshot.cc

@@ -1509,16 +1509,15 @@ class CodeSerializationCluster : public SerializationCluster {
         s->UnexpectedObject(code, "Disabled code");
       }
 
-      s->WriteInstructions(code->ptr()->instructions_,
+      s->WriteInstructions(code->ptr()->instructions_, code);
-                           code->ptr()->unchecked_offset_, code);
+      s->WriteUnsigned(code->ptr()->unchecked_offset_);
       if (kind == Snapshot::kFullJIT) {
         // TODO(rmacnak): Fix references to disabled code before serializing.
         // For now, we may write the FixCallersTarget or equivalent stub. This
         // will cause a fixup if this code is called.
-        const uint32_t active_unchecked_offset =
+        s->WriteInstructions(code->ptr()->active_instructions_, code);
-            code->ptr()->unchecked_entry_point_ - code->ptr()->entry_point_;
+        s->WriteUnsigned(code->ptr()->unchecked_entry_point_ -
-        s->WriteInstructions(code->ptr()->active_instructions_,
+                         code->ptr()->entry_point_);
-                             active_unchecked_offset, code);
       }
 
       WriteField(code, object_pool_);
@@ -1599,10 +1598,24 @@ class CodeDeserializationCluster : public DeserializationCluster {
 
   void ReadFill(Deserializer* d) {
     for (intptr_t id = start_index_; id < stop_index_; id++) {
-      auto const code = reinterpret_cast<RawCode*>(d->Ref(id));
+      RawCode* code = reinterpret_cast<RawCode*>(d->Ref(id));
       Deserializer::InitializeHeader(code, kCodeCid, Code::InstanceSize(0));
 
-      d->ReadInstructions(code);
+      RawInstructions* instr = d->ReadInstructions();
+      uint32_t unchecked_offset = d->ReadUnsigned();
+
+      code->ptr()->instructions_ = instr;
+
+#if !defined(DART_PRECOMPILED_RUNTIME)
+      code->ptr()->unchecked_offset_ = unchecked_offset;
+      if (d->kind() == Snapshot::kFullJIT) {
+        instr = d->ReadInstructions();
+        unchecked_offset = d->ReadUnsigned();
+      }
+      code->ptr()->active_instructions_ = instr;
+#endif  // !DART_PRECOMPILED_RUNTIME
+
+      Code::InitializeCachedEntryPointsFrom(code, instr, unchecked_offset);
 
       code->ptr()->object_pool_ =
           reinterpret_cast<RawObjectPool*>(d->ReadRef());
@@ -1638,32 +1651,7 @@ class CodeDeserializationCluster : public DeserializationCluster {
 #endif
 
       code->ptr()->state_bits_ = d->Read<int32_t>();
-#if defined(DART_PRECOMPILED_RUNTIME)
-      if (FLAG_use_bare_instructions && id != start_index_) {
-        // The following assumes that ReadInstructions put the offset of the
-        // entry point from the payload start into instructions_length_. We
-        // use this to calculate the length of the previous payload.
-        RawCode* prev = reinterpret_cast<RawCode*>(d->Ref(id - 1));
-        const uword prev_payload_start =
-            prev->ptr()->entry_point_ - prev->ptr()->instructions_length_;
-        const uword curr_payload_start =
-            code->ptr()->entry_point_ - code->ptr()->instructions_length_;
-        prev->ptr()->instructions_length_ =
-            curr_payload_start - prev_payload_start;
-      }
-#endif
     }
-#if defined(DART_PRECOMPILED_RUNTIME)
-    if (FLAG_use_bare_instructions) {
-      // Since there is no following Code object, we assume that the last Code
-      // object ends at the end of the instructions snapshot.
-      auto const code = reinterpret_cast<RawCode*>(d->Ref(stop_index_ - 1));
-      const uword curr_payload_start =
-          code->ptr()->entry_point_ - code->ptr()->instructions_length_;
-      code->ptr()->instructions_length_ =
-          d->GetBareInstructionsEnd() - curr_payload_start;
-    }
-#endif
   }
 
 #if !defined(PRODUCT) || defined(FORCE_INCLUDE_DISASSEMBLER)
@@ -4687,9 +4675,7 @@ SerializationCluster* Serializer::NewClusterForClass(intptr_t cid) {
 }
 
 #if !defined(DART_PRECOMPILED_RUNTIME)
-void Serializer::WriteInstructions(RawInstructions* instr,
+void Serializer::WriteInstructions(RawInstructions* instr, RawCode* code) {
-                                   uint32_t unchecked_offset,
-                                   RawCode* code) {
   ASSERT(code != Code::null());
 
   const intptr_t offset = image_writer_->GetTextOffsetFor(instr, code);
@@ -4698,17 +4684,6 @@ void Serializer::WriteInstructions(RawInstructions* instr,
     UnexpectedObject(code, "Expected instructions to reuse");
   }
   Write<uint32_t>(offset);
-  if (FLAG_precompiled_mode && FLAG_use_bare_instructions) {
-    // When writing only instruction payloads, we also need to serialize
-    // whether there was a single entry. We add this as the low order bit
-    // in the unchecked_offset.
-    ASSERT(unchecked_offset <= kMaxInt32);
-    const uint32_t payload_info =
-        (unchecked_offset << 1) | (Code::HasMonomorphicEntry(code) ? 0x1 : 0x0);
-    WriteUnsigned(payload_info);
-  } else {
-    WriteUnsigned(unchecked_offset);
-  }
 
   // If offset < 0, it's pointing to a shared instruction. We don't profile
   // references to shared text/data (since they don't consume any space). Of
@@ -5448,74 +5423,11 @@ RawApiError* FullSnapshotReader::ConvertToApiError(char* message) {
   return ApiError::New(msg, Heap::kOld);
 }
 
-void Deserializer::ReadInstructions(RawCode* code) {
+RawInstructions* Deserializer::ReadInstructions() {
-#if defined(DART_PRECOMPILED_RUNTIME)
+  uint32_t offset = Read<uint32_t>();
-  if (FLAG_use_bare_instructions) {
+  return image_reader_->GetInstructionsAt(offset);
-    const uint32_t bare_offset = Read<uint32_t>();
-    const uword payload_start =
-        image_reader_->GetBareInstructionsAt(bare_offset);
-    const uint32_t payload_info = ReadUnsigned();
-    const uint32_t unchecked_offset = payload_info >> 1;
-    const bool has_monomorphic_entrypoint = (payload_info & 0x1) == 0x1;
-
-    const uword entry_offset = has_monomorphic_entrypoint
-                                   ? Instructions::kPolymorphicEntryOffsetAOT
-                                   : 0;
-    const uword monomorphic_entry_offset =
-        has_monomorphic_entrypoint ? Instructions::kMonomorphicEntryOffsetAOT
-                                   : 0;
-
-    const uword entry_point = payload_start + entry_offset;
-    const uword monomorphic_entry_point =
-        payload_start + monomorphic_entry_offset;
-
-    code->ptr()->instructions_ = Instructions::null();
-    code->ptr()->entry_point_ = entry_point;
-    code->ptr()->unchecked_entry_point_ = entry_point + unchecked_offset;
-    code->ptr()->monomorphic_entry_point_ = monomorphic_entry_point;
-    code->ptr()->monomorphic_unchecked_entry_point_ =
-        monomorphic_entry_point + unchecked_offset;
-    // We don't serialize the length of the instructions payload. Instead, the
-    // deserializer calculates an approximate length (may include padding)
-    // by subtracting the payload offset of the next Code object (if any)
-    // from this one. (For the last Code object, we assume its serialization
-    // extends to the end of the instructions image.)
-    //
-    // Since the Code object doesn't include a field for the payload start,
-    // we store the entry_offset (calculated above) in instructions_length_
-    // for now, and subtract it from entry_point_ later after reading the
-    // next Code object.
-    ASSERT(entry_offset <= kMaxUint32);
-    code->ptr()->instructions_length_ = entry_offset;
-    return;
-  }
-#endif
-
-  const uint32_t offset = Read<uint32_t>();
-  RawInstructions* instr = image_reader_->GetInstructionsAt(offset);
-  uint32_t unchecked_offset = ReadUnsigned();
-
-  code->ptr()->instructions_ = instr;
-#if defined(DART_PRECOMPILED_RUNTIME)
-  code->ptr()->instructions_length_ = Instructions::Size(instr);
-#else
-  code->ptr()->unchecked_offset_ = unchecked_offset;
-  if (kind() == Snapshot::kFullJIT) {
-    const uint32_t active_offset = Read<uint32_t>();
-    instr = image_reader_->GetInstructionsAt(active_offset);
-    unchecked_offset = ReadUnsigned();
-  }
-  code->ptr()->active_instructions_ = instr;
-#endif
-  Code::InitializeCachedEntryPointsFrom(code, instr, unchecked_offset);
 }
 
-#if defined(DART_PRECOMPILED_RUNTIME)
-uword Deserializer::GetBareInstructionsEnd() {
-  return image_reader_->GetBareInstructionsEnd();
-}
-#endif
-
 RawObject* Deserializer::GetObjectAt(uint32_t offset) const {
   return image_reader_->GetObjectAt(offset);
 }

runtime/vm/clustered_snapshot.h

@@ -358,9 +358,7 @@ class Serializer : public ThreadStackResource {
     Write<int32_t>(cid);
   }
 
-  void WriteInstructions(RawInstructions* instr,
+  void WriteInstructions(RawInstructions* instr, RawCode* code);
-                         uint32_t unchecked_offset,
-                         RawCode* code);
   uint32_t GetDataOffset(RawObject* object) const;
   void TraceDataOffset(uint32_t offset);
   intptr_t GetDataSize() const;
@@ -561,8 +559,7 @@ class Deserializer : public ThreadStackResource {
     return Read<int32_t>();
   }
 
-  ONLY_IN_PRECOMPILED(uword GetBareInstructionsEnd());
+  RawInstructions* ReadInstructions();
-  void ReadInstructions(RawCode* code);
   RawObject* GetObjectAt(uint32_t offset) const;
 
   void SkipHeader() { stream_.SetPosition(Snapshot::kHeaderSize); }

runtime/vm/compiler/assembler/assembler.h

@@ -303,7 +303,7 @@ class AssemblerBase : public StackResource {
   explicit AssemblerBase(ObjectPoolBuilder* object_pool_builder)
       : StackResource(ThreadState::Current()),
         prologue_offset_(-1),
-        has_monomorphic_entry_(false),
+        has_single_entry_point_(true),
         object_pool_builder_(object_pool_builder) {}
   virtual ~AssemblerBase();
 
@@ -315,7 +315,7 @@ class AssemblerBase : public StackResource {
   ObjectPoolBuilder& object_pool_builder() { return *object_pool_builder_; }
 
   intptr_t prologue_offset() const { return prologue_offset_; }
-  bool has_monomorphic_entry() const { return has_monomorphic_entry_; }
+  bool has_single_entry_point() const { return has_single_entry_point_; }
 
   void Comment(const char* format, ...) PRINTF_ATTRIBUTE(2, 3);
   static bool EmittingComments();
@@ -370,7 +370,7 @@ class AssemblerBase : public StackResource {
  protected:
   AssemblerBuffer buffer_;  // Contains position independent code.
   int32_t prologue_offset_;
-  bool has_monomorphic_entry_;
+  bool has_single_entry_point_;
 
   intptr_t unchecked_entry_offset_ = 0;
 

runtime/vm/compiler/assembler/assembler_arm.cc

@@ -3437,7 +3437,7 @@ void Assembler::LeaveStubFrame() {
 // R0 receiver, R9 ICData entries array
 // Preserve R4 (ARGS_DESC_REG), not required today, but maybe later.
 void Assembler::MonomorphicCheckedEntryJIT() {
-  has_monomorphic_entry_ = true;
+  has_single_entry_point_ = false;
 #if defined(TESTING) || defined(DEBUG)
   bool saved_use_far_branches = use_far_branches();
   set_use_far_branches(false);
@@ -3473,7 +3473,7 @@ void Assembler::MonomorphicCheckedEntryJIT() {
 // R0 receiver, R9 guarded cid as Smi.
 // Preserve R4 (ARGS_DESC_REG), not required today, but maybe later.
 void Assembler::MonomorphicCheckedEntryAOT() {
-  has_monomorphic_entry_ = true;
+  has_single_entry_point_ = false;
 #if defined(TESTING) || defined(DEBUG)
   bool saved_use_far_branches = use_far_branches();
   set_use_far_branches(false);
@@ -3498,7 +3498,7 @@ void Assembler::MonomorphicCheckedEntryAOT() {
 }
 
 void Assembler::BranchOnMonomorphicCheckedEntryJIT(Label* label) {
-  has_monomorphic_entry_ = true;
+  has_single_entry_point_ = false;
   while (CodeSize() < target::Instructions::kMonomorphicEntryOffsetJIT) {
     bkpt(0);
   }

runtime/vm/compiler/assembler/assembler_arm64.cc

@@ -1532,7 +1532,7 @@ void Assembler::LeaveStubFrame() {
 // R0 receiver, R5 ICData entries array
 // Preserve R4 (ARGS_DESC_REG), not required today, but maybe later.
 void Assembler::MonomorphicCheckedEntryJIT() {
-  has_monomorphic_entry_ = true;
+  has_single_entry_point_ = false;
   const bool saved_use_far_branches = use_far_branches();
   set_use_far_branches(false);
   const intptr_t start = CodeSize();
@@ -1569,7 +1569,7 @@ void Assembler::MonomorphicCheckedEntryJIT() {
 // R0 receiver, R5 guarded cid as Smi.
 // Preserve R4 (ARGS_DESC_REG), not required today, but maybe later.
 void Assembler::MonomorphicCheckedEntryAOT() {
-  has_monomorphic_entry_ = true;
+  has_single_entry_point_ = false;
   bool saved_use_far_branches = use_far_branches();
   set_use_far_branches(false);
 
@@ -1595,7 +1595,7 @@ void Assembler::MonomorphicCheckedEntryAOT() {
 }
 
 void Assembler::BranchOnMonomorphicCheckedEntryJIT(Label* label) {
-  has_monomorphic_entry_ = true;
+  has_single_entry_point_ = false;
   while (CodeSize() < target::Instructions::kMonomorphicEntryOffsetJIT) {
     brk(0);
   }

runtime/vm/compiler/assembler/assembler_ia32.cc

@@ -2117,7 +2117,7 @@ void Assembler::EmitEntryFrameVerification() {
 // EBX receiver, ECX ICData entries array
 // Preserve EDX (ARGS_DESC_REG), not required today, but maybe later.
 void Assembler::MonomorphicCheckedEntryJIT() {
-  has_monomorphic_entry_ = true;
+  has_single_entry_point_ = false;
   intptr_t start = CodeSize();
   Label have_cid, miss;
   Bind(&miss);
@@ -2156,7 +2156,7 @@ void Assembler::MonomorphicCheckedEntryAOT() {
 }
 
 void Assembler::BranchOnMonomorphicCheckedEntryJIT(Label* label) {
-  has_monomorphic_entry_ = true;
+  has_single_entry_point_ = false;
   while (CodeSize() < target::Instructions::kMonomorphicEntryOffsetJIT) {
     int3();
   }

runtime/vm/compiler/assembler/assembler_x64.cc

@@ -1798,7 +1798,7 @@ void Assembler::LeaveStubFrame() {
 // RDX receiver, RBX ICData entries array
 // Preserve R10 (ARGS_DESC_REG), not required today, but maybe later.
 void Assembler::MonomorphicCheckedEntryJIT() {
-  has_monomorphic_entry_ = true;
+  has_single_entry_point_ = false;
   intptr_t start = CodeSize();
   Label have_cid, miss;
   Bind(&miss);
@@ -1831,7 +1831,7 @@ void Assembler::MonomorphicCheckedEntryJIT() {
 }
 
 void Assembler::MonomorphicCheckedEntryAOT() {
-  has_monomorphic_entry_ = true;
+  has_single_entry_point_ = false;
   intptr_t start = CodeSize();
   Label have_cid, miss;
   Bind(&miss);
@@ -1862,7 +1862,7 @@ void Assembler::MonomorphicCheckedEntryAOT() {
 }
 
 void Assembler::BranchOnMonomorphicCheckedEntryJIT(Label* label) {
-  has_monomorphic_entry_ = true;
+  has_single_entry_point_ = false;
   while (CodeSize() < target::Instructions::kMonomorphicEntryOffsetJIT) {
     int3();
   }

runtime/vm/compiler/assembler/disassembler.cc

@@ -258,7 +258,8 @@ void Disassembler::DisassembleCodeHelper(const char* function_fullname,
       PcDescriptors::Handle(zone, code.pc_descriptors());
   THR_Print("%s}\n", descriptors.ToCString());
 
-  const uword start = code.PayloadStart();
+  const auto& instructions = Instructions::Handle(code.instructions());
+  const uword start = instructions.PayloadStart();
   const uword base = FLAG_disassemble_relative ? 0 : start;
 
 #if !defined(DART_PRECOMPILED_RUNTIME)

runtime/vm/compiler/relocation.cc

@@ -157,7 +157,8 @@ void CodeRelocator::FindInstructionAndCallLimits() {
           offset_into_target = call.distance();
         }
 
-        const uword destination_payload = destination_.PayloadStart();
+        const uword destination_payload =
+            Instructions::PayloadStart(destination_.instructions());
         const uword entry_point = call_entry_point == Code::kUncheckedEntry
                                       ? destination_.UncheckedEntryPoint()
                                       : destination_.EntryPoint();
@@ -271,16 +272,17 @@ void CodeRelocator::ScanCallTargets(const Code& code,
       offset_into_target = call.distance();
     }
 
-    const uword destination_payload = destination_.PayloadStart();
+    const uword destination_payload =
+        Instructions::PayloadStart(destination_.instructions());
     const uword entry_point = call_entry_point == Code::kUncheckedEntry
                                   ? destination_.UncheckedEntryPoint()
                                   : destination_.EntryPoint();
 
     offset_into_target += (entry_point - destination_payload);
 
-    const intptr_t text_offset =
+    const intptr_t text_offset = code_text_offset +
-        code_text_offset + AdjustPayloadOffset(call_instruction_offset);
+                                 compiler::target::Instructions::HeaderSize() +
-
+                                 call_instruction_offset;
     UnresolvedCall unresolved_call(code.raw(), call_instruction_offset,
                                    text_offset, destination_.raw(),
                                    offset_into_target);
@@ -366,12 +368,12 @@ void CodeRelocator::ResolveCallToDestination(UnresolvedCall* unresolved_call,
   const intptr_t call_text_offset = unresolved_call->text_offset;
   const intptr_t call_offset = unresolved_call->call_offset;
 
+  auto caller = Code::InstructionsOf(unresolved_call->caller);
   const int32_t distance = destination_text - call_text_offset;
   {
-    auto const caller = unresolved_call->caller;
+    uword addr = Instructions::PayloadStart(caller) + call_offset;
-    uword addr = Code::PayloadStartOf(caller) + call_offset;
     if (FLAG_write_protect_code) {
-      addr -= HeapPage::Of(Code::InstructionsOf(caller))->AliasOffset();
+      addr -= HeapPage::Of(caller)->AliasOffset();
     }
     PcRelativeCallPattern call(addr);
     ASSERT(call.IsValid());
@@ -508,15 +510,9 @@ void CodeRelocator::BuildTrampolinesForAlmostOutOfRangeCalls() {
 intptr_t CodeRelocator::FindDestinationInText(
     const RawInstructions* destination,
     intptr_t offset_into_target) {
-  auto const destination_offset = text_offsets_.LookupValue(destination);
+  auto destination_offset = text_offsets_.LookupValue(destination);
-  return destination_offset + AdjustPayloadOffset(offset_into_target);
+  return destination_offset + compiler::target::Instructions::HeaderSize() +
-}
+         offset_into_target;
-
-intptr_t CodeRelocator::AdjustPayloadOffset(intptr_t payload_offset) {
-  if (FLAG_precompiled_mode && FLAG_use_bare_instructions) {
-    return payload_offset;
-  }
-  return compiler::target::Instructions::HeaderSize() + payload_offset;
 }
 
 #endif  // defined(DART_PRECOMPILER) && !defined(TARGET_ARCH_IA32)

runtime/vm/compiler/relocation.h

@@ -178,8 +178,6 @@ class CodeRelocator : public StackResource {
   intptr_t FindDestinationInText(const RawInstructions* destination,
                                  intptr_t offset_into_target);
 
-  static intptr_t AdjustPayloadOffset(intptr_t payload_offset);
-
   bool IsTargetInRangeFor(UnresolvedCall* unresolved_call,
                           intptr_t target_text_offset);
 

runtime/vm/compiler/runtime_api.cc

@@ -513,11 +513,6 @@ const word StoreBufferBlock::kSize = dart::StoreBufferBlock::kSize;
 
 const word MarkingStackBlock::kSize = dart::MarkingStackBlock::kSize;
 
-word InstructionsSection::HeaderSize() {
-  return Utils::RoundUp(InstructionsSection::UnalignedHeaderSize(),
-                        target::kWordSize);
-}
-
 word Instructions::HeaderSize() {
   return Utils::RoundUp(Instructions::UnalignedHeaderSize(), target::kWordSize);
 }
@@ -916,10 +911,6 @@ word MonomorphicSmiableCall::NextFieldOffset() {
   return -kWordSize;
 }
 
-word InstructionsSection::NextFieldOffset() {
-  return -kWordSize;
-}
-
 word Instructions::NextFieldOffset() {
   return -kWordSize;
 }

runtime/vm/compiler/runtime_api.h

@@ -1063,14 +1063,6 @@ class ClassTable : public AllStatic {
   static const word kSizeOfClassPairLog2;
 };
 
-class InstructionsSection : public AllStatic {
- public:
-  static word HeaderSize();
-  static word UnalignedHeaderSize();
-  static word InstanceSize();
-  static word NextFieldOffset();
-};
-
 class Instructions : public AllStatic {
  public:
   static const word kMonomorphicEntryOffsetJIT;

runtime/vm/compiler/runtime_offsets_extracted.h

@@ -415,10 +415,6 @@ static constexpr dart::compiler::target::word Instance_InstanceSize = 4;
 static constexpr dart::compiler::target::word Instructions_InstanceSize = 8;
 static constexpr dart::compiler::target::word Instructions_UnalignedHeaderSize =
     8;
-static constexpr dart::compiler::target::word InstructionsSection_InstanceSize =
-    8;
-static constexpr dart::compiler::target::word
-    InstructionsSection_UnalignedHeaderSize = 8;
 static constexpr dart::compiler::target::word Int32x4_InstanceSize = 24;
 static constexpr dart::compiler::target::word Integer_InstanceSize = 4;
 static constexpr dart::compiler::target::word KernelProgramInfo_InstanceSize =
@@ -878,10 +874,6 @@ static constexpr dart::compiler::target::word Instance_InstanceSize = 8;
 static constexpr dart::compiler::target::word Instructions_InstanceSize = 12;
 static constexpr dart::compiler::target::word Instructions_UnalignedHeaderSize =
     12;
-static constexpr dart::compiler::target::word InstructionsSection_InstanceSize =
-    12;
-static constexpr dart::compiler::target::word
-    InstructionsSection_UnalignedHeaderSize = 12;
 static constexpr dart::compiler::target::word Int32x4_InstanceSize = 24;
 static constexpr dart::compiler::target::word Integer_InstanceSize = 8;
 static constexpr dart::compiler::target::word KernelProgramInfo_InstanceSize =
@@ -1334,10 +1326,6 @@ static constexpr dart::compiler::target::word Instance_InstanceSize = 4;
 static constexpr dart::compiler::target::word Instructions_InstanceSize = 8;
 static constexpr dart::compiler::target::word Instructions_UnalignedHeaderSize =
     8;
-static constexpr dart::compiler::target::word InstructionsSection_InstanceSize =
-    8;
-static constexpr dart::compiler::target::word
-    InstructionsSection_UnalignedHeaderSize = 8;
 static constexpr dart::compiler::target::word Int32x4_InstanceSize = 24;
 static constexpr dart::compiler::target::word Integer_InstanceSize = 4;
 static constexpr dart::compiler::target::word KernelProgramInfo_InstanceSize =
@@ -1798,10 +1786,6 @@ static constexpr dart::compiler::target::word Instance_InstanceSize = 8;
 static constexpr dart::compiler::target::word Instructions_InstanceSize = 12;
 static constexpr dart::compiler::target::word Instructions_UnalignedHeaderSize =
     12;
-static constexpr dart::compiler::target::word InstructionsSection_InstanceSize =
-    12;
-static constexpr dart::compiler::target::word
-    InstructionsSection_UnalignedHeaderSize = 12;
 static constexpr dart::compiler::target::word Int32x4_InstanceSize = 24;
 static constexpr dart::compiler::target::word Integer_InstanceSize = 8;
 static constexpr dart::compiler::target::word KernelProgramInfo_InstanceSize =
@@ -2254,10 +2238,6 @@ static constexpr dart::compiler::target::word Instance_InstanceSize = 4;
 static constexpr dart::compiler::target::word Instructions_InstanceSize = 8;
 static constexpr dart::compiler::target::word Instructions_UnalignedHeaderSize =
     8;
-static constexpr dart::compiler::target::word InstructionsSection_InstanceSize =
-    8;
-static constexpr dart::compiler::target::word
-    InstructionsSection_UnalignedHeaderSize = 8;
 static constexpr dart::compiler::target::word Int32x4_InstanceSize = 24;
 static constexpr dart::compiler::target::word Integer_InstanceSize = 4;
 static constexpr dart::compiler::target::word KernelProgramInfo_InstanceSize =
@@ -2711,10 +2691,6 @@ static constexpr dart::compiler::target::word Instance_InstanceSize = 8;
 static constexpr dart::compiler::target::word Instructions_InstanceSize = 12;
 static constexpr dart::compiler::target::word Instructions_UnalignedHeaderSize =
     12;
-static constexpr dart::compiler::target::word InstructionsSection_InstanceSize =
-    12;
-static constexpr dart::compiler::target::word
-    InstructionsSection_UnalignedHeaderSize = 12;
 static constexpr dart::compiler::target::word Int32x4_InstanceSize = 24;
 static constexpr dart::compiler::target::word Integer_InstanceSize = 8;
 static constexpr dart::compiler::target::word KernelProgramInfo_InstanceSize =
@@ -3161,10 +3137,6 @@ static constexpr dart::compiler::target::word Instance_InstanceSize = 4;
 static constexpr dart::compiler::target::word Instructions_InstanceSize = 8;
 static constexpr dart::compiler::target::word Instructions_UnalignedHeaderSize =
     8;
-static constexpr dart::compiler::target::word InstructionsSection_InstanceSize =
-    8;
-static constexpr dart::compiler::target::word
-    InstructionsSection_UnalignedHeaderSize = 8;
 static constexpr dart::compiler::target::word Int32x4_InstanceSize = 24;
 static constexpr dart::compiler::target::word Integer_InstanceSize = 4;
 static constexpr dart::compiler::target::word KernelProgramInfo_InstanceSize =
@@ -3619,10 +3591,6 @@ static constexpr dart::compiler::target::word Instance_InstanceSize = 8;
 static constexpr dart::compiler::target::word Instructions_InstanceSize = 12;
 static constexpr dart::compiler::target::word Instructions_UnalignedHeaderSize =
     12;
-static constexpr dart::compiler::target::word InstructionsSection_InstanceSize =
-    12;
-static constexpr dart::compiler::target::word
-    InstructionsSection_UnalignedHeaderSize = 12;
 static constexpr dart::compiler::target::word Int32x4_InstanceSize = 24;
 static constexpr dart::compiler::target::word Integer_InstanceSize = 8;
 static constexpr dart::compiler::target::word KernelProgramInfo_InstanceSize =
@@ -4111,10 +4079,6 @@ static constexpr dart::compiler::target::word AOT_Instance_InstanceSize = 4;
 static constexpr dart::compiler::target::word AOT_Instructions_InstanceSize = 8;
 static constexpr dart::compiler::target::word
     AOT_Instructions_UnalignedHeaderSize = 8;
-static constexpr dart::compiler::target::word
-    AOT_InstructionsSection_InstanceSize = 8;
-static constexpr dart::compiler::target::word
-    AOT_InstructionsSection_UnalignedHeaderSize = 8;
 static constexpr dart::compiler::target::word AOT_Int32x4_InstanceSize = 24;
 static constexpr dart::compiler::target::word AOT_Integer_InstanceSize = 4;
 static constexpr dart::compiler::target::word
@@ -4617,10 +4581,6 @@ static constexpr dart::compiler::target::word AOT_Instructions_InstanceSize =
     12;
 static constexpr dart::compiler::target::word
     AOT_Instructions_UnalignedHeaderSize = 12;
-static constexpr dart::compiler::target::word
-    AOT_InstructionsSection_InstanceSize = 12;
-static constexpr dart::compiler::target::word
-    AOT_InstructionsSection_UnalignedHeaderSize = 12;
 static constexpr dart::compiler::target::word AOT_Int32x4_InstanceSize = 24;
 static constexpr dart::compiler::target::word AOT_Integer_InstanceSize = 8;
 static constexpr dart::compiler::target::word
@@ -5127,10 +5087,6 @@ static constexpr dart::compiler::target::word AOT_Instructions_InstanceSize =
     12;
 static constexpr dart::compiler::target::word
     AOT_Instructions_UnalignedHeaderSize = 12;
-static constexpr dart::compiler::target::word
-    AOT_InstructionsSection_InstanceSize = 12;
-static constexpr dart::compiler::target::word
-    AOT_InstructionsSection_UnalignedHeaderSize = 12;
 static constexpr dart::compiler::target::word AOT_Int32x4_InstanceSize = 24;
 static constexpr dart::compiler::target::word AOT_Integer_InstanceSize = 8;
 static constexpr dart::compiler::target::word
@@ -5593,7 +5549,7 @@ static constexpr dart::compiler::target::word AOT_Capability_InstanceSize = 16;
 static constexpr dart::compiler::target::word AOT_Class_InstanceSize = 112;
 static constexpr dart::compiler::target::word AOT_Closure_InstanceSize = 28;
 static constexpr dart::compiler::target::word AOT_ClosureData_InstanceSize = 20;
-static constexpr dart::compiler::target::word AOT_Code_InstanceSize = 64;
+static constexpr dart::compiler::target::word AOT_Code_InstanceSize = 60;
 static constexpr dart::compiler::target::word AOT_CodeSourceMap_InstanceSize =
     8;
 static constexpr dart::compiler::target::word
@@ -5626,10 +5582,6 @@ static constexpr dart::compiler::target::word AOT_Instance_InstanceSize = 4;
 static constexpr dart::compiler::target::word AOT_Instructions_InstanceSize = 8;
 static constexpr dart::compiler::target::word
     AOT_Instructions_UnalignedHeaderSize = 8;
-static constexpr dart::compiler::target::word
-    AOT_InstructionsSection_InstanceSize = 8;
-static constexpr dart::compiler::target::word
-    AOT_InstructionsSection_UnalignedHeaderSize = 8;
 static constexpr dart::compiler::target::word AOT_Int32x4_InstanceSize = 24;
 static constexpr dart::compiler::target::word AOT_Integer_InstanceSize = 4;
 static constexpr dart::compiler::target::word
@@ -6125,10 +6077,6 @@ static constexpr dart::compiler::target::word AOT_Instructions_InstanceSize =
     12;
 static constexpr dart::compiler::target::word
     AOT_Instructions_UnalignedHeaderSize = 12;
-static constexpr dart::compiler::target::word
-    AOT_InstructionsSection_InstanceSize = 12;
-static constexpr dart::compiler::target::word
-    AOT_InstructionsSection_UnalignedHeaderSize = 12;
 static constexpr dart::compiler::target::word AOT_Int32x4_InstanceSize = 24;
 static constexpr dart::compiler::target::word AOT_Integer_InstanceSize = 8;
 static constexpr dart::compiler::target::word
@@ -6628,10 +6576,6 @@ static constexpr dart::compiler::target::word AOT_Instructions_InstanceSize =
     12;
 static constexpr dart::compiler::target::word
     AOT_Instructions_UnalignedHeaderSize = 12;
-static constexpr dart::compiler::target::word
-    AOT_InstructionsSection_InstanceSize = 12;
-static constexpr dart::compiler::target::word
-    AOT_InstructionsSection_UnalignedHeaderSize = 12;
 static constexpr dart::compiler::target::word AOT_Int32x4_InstanceSize = 24;
 static constexpr dart::compiler::target::word AOT_Integer_InstanceSize = 8;
 static constexpr dart::compiler::target::word

runtime/vm/compiler/runtime_offsets_list.h

@@ -286,8 +286,6 @@
   SIZEOF(Instance, InstanceSize, RawInstance)                                  \
   SIZEOF(Instructions, InstanceSize, RawInstructions)                          \
   SIZEOF(Instructions, UnalignedHeaderSize, RawInstructions)                   \
-  SIZEOF(InstructionsSection, InstanceSize, RawInstructionsSection)            \
-  SIZEOF(InstructionsSection, UnalignedHeaderSize, RawInstructionsSection)     \
   SIZEOF(Int32x4, InstanceSize, RawInt32x4)                                    \
   SIZEOF(Integer, InstanceSize, RawInteger)                                    \
   SIZEOF(KernelProgramInfo, InstanceSize, RawKernelProgramInfo)                \

runtime/vm/globals.h

@@ -78,12 +78,6 @@ const intptr_t kDefaultMaxOldGenHeapSize = (kWordSize <= 4) ? 1536 : 30720;
 #define NOT_IN_PRECOMPILED(code) code
 #endif  // defined(DART_PRECOMPILED_RUNTIME)
 
-#if defined(DART_PRECOMPILED_RUNTIME)
-#define ONLY_IN_PRECOMPILED(code) code
-#else
-#define ONLY_IN_PRECOMPILED(code)
-#endif  // defined(DART_PRECOMPILED_RUNTIME)
-
 #if defined(TARGET_ARCH_ARM) || defined(TARGET_ARCH_ARM64) ||                  \
     defined(TARGET_ARCH_X64)
 #define ONLY_IN_ARM_ARM64_X64(code) code

runtime/vm/image_snapshot.cc

@@ -5,7 +5,6 @@
 #include "vm/image_snapshot.h"
 
 #include "platform/assert.h"
-#include "vm/class_id.h"
 #include "vm/compiler/backend/code_statistics.h"
 #include "vm/compiler/runtime_api.h"
 #include "vm/dwarf.h"
@@ -136,25 +135,6 @@ int32_t ImageWriter::GetTextOffsetFor(RawInstructions* instructions,
   return offset;
 }
 
-static intptr_t InstructionsSizeInSnapshot(RawInstructions* raw) {
-  if (FLAG_precompiled_mode && FLAG_use_bare_instructions) {
-    // Currently, we align bare instruction payloads on 4 byte boundaries.
-    //
-    // If we later decide to align on larger boundaries to put entries at the
-    // start of cache lines, make sure to account for entry points that are
-    // _not_ at the start of the payload.
-    return Utils::RoundUp(Instructions::Size(raw),
-                          ImageWriter::kBareInstructionsAlignment);
-  }
-#if defined(IS_SIMARM_X64)
-  return Utils::RoundUp(
-      compiler::target::Instructions::HeaderSize() + Instructions::Size(raw),
-      compiler::target::ObjectAlignment::kObjectAlignment);
-#else
-  return raw->HeapSize();
-#endif
-}
-
 #if defined(IS_SIMARM_X64)
 static intptr_t CompressedStackMapsSizeInSnapshot(intptr_t payload_size) {
   // We do not need to round the non-payload size up to a word boundary because
@@ -191,6 +171,11 @@ static intptr_t PcDescriptorsSizeInSnapshot(intptr_t len) {
                         compiler::target::ObjectAlignment::kObjectAlignment);
 }
 
+static intptr_t InstructionsSizeInSnapshot(intptr_t len) {
+  return Utils::RoundUp(compiler::target::Instructions::HeaderSize() + len,
+                        compiler::target::ObjectAlignment::kObjectAlignment);
+}
+
 intptr_t ImageWriter::SizeInSnapshot(RawObject* raw_object) {
   const classid_t cid = raw_object->GetClassId();
 
@@ -216,7 +201,7 @@ intptr_t ImageWriter::SizeInSnapshot(RawObject* raw_object) {
     }
     case kInstructionsCid: {
       RawInstructions* raw_insns = static_cast<RawInstructions*>(raw_object);
-      return InstructionsSizeInSnapshot(raw_insns);
+      return InstructionsSizeInSnapshot(Instructions::Size(raw_insns));
     }
     default: {
       const Class& clazz = Class::Handle(Object::Handle(raw_object).clazz());
@@ -226,13 +211,8 @@ intptr_t ImageWriter::SizeInSnapshot(RawObject* raw_object) {
   }
 }
 #else   // defined(IS_SIMARM_X64)
-intptr_t ImageWriter::SizeInSnapshot(RawObject* raw) {
+intptr_t ImageWriter::SizeInSnapshot(RawObject* raw_object) {
-  switch (raw->GetClassId()) {
+  return raw_object->HeapSize();
-    case kInstructionsCid:
-      return InstructionsSizeInSnapshot(static_cast<RawInstructions*>(raw));
-    default:
-      return raw->HeapSize();
-  }
 }
 #endif  // defined(IS_SIMARM_X64)
 
@@ -576,9 +556,6 @@ void AssemblyImageWriter::WriteText(WriteStream* clustered_stream, bool vm) {
 #else
   Zone* zone = Thread::Current()->zone();
 
-  const bool bare_instruction_payloads =
-      FLAG_precompiled_mode && FLAG_use_bare_instructions;
-
 #if defined(DART_PRECOMPILER)
   const char* bss_symbol =
       vm ? "_kDartVmSnapshotBss" : "_kDartIsolateSnapshotBss";
@@ -595,14 +572,13 @@ void AssemblyImageWriter::WriteText(WriteStream* clustered_stream, bool vm) {
 
   // Start snapshot at page boundary.
   ASSERT(VirtualMemory::PageSize() >= kMaxObjectAlignment);
-  Align(VirtualMemory::PageSize());
+  assembly_stream_.Print(".balign %" Pd ", 0\n", VirtualMemory::PageSize());
   assembly_stream_.Print("%s:\n", instructions_symbol);
 
   // This head also provides the gap to make the instructions snapshot
   // look like a HeapPage.
-  const intptr_t image_size = Utils::RoundUp(
+  intptr_t instructions_length = next_text_offset_;
-      next_text_offset_, compiler::target::ObjectAlignment::kObjectAlignment);
+  WriteWordLiteralText(instructions_length);
-  WriteWordLiteralText(image_size);
 
 #if defined(DART_PRECOMPILER)
   assembly_stream_.Print("%s %s - %s\n", kLiteralPrefix, bss_symbol,
@@ -616,43 +592,6 @@ void AssemblyImageWriter::WriteText(WriteStream* clustered_stream, bool vm) {
     WriteWordLiteralText(0);
   }
 
-  if (bare_instruction_payloads) {
-    const intptr_t image_payload_length = image_size - Image::kHeaderSize;
-    // Add the RawInstructionsSection header.
-    uword marked_tags = 0;
-    marked_tags = RawObject::OldBit::update(true, marked_tags);
-    marked_tags = RawObject::OldAndNotRememberedBit::update(true, marked_tags);
-    marked_tags = RawObject::SizeTag::update(image_payload_length, marked_tags);
-    marked_tags =
-        RawObject::ClassIdTag::update(kInstructionsSectionCid, marked_tags);
-
-    WriteWordLiteralText(marked_tags);
-    // Calculated using next_text_offset_, which doesn't include post-payload
-    // padding to object alignment.
-    const intptr_t instructions_length =
-        next_text_offset_ - Image::kHeaderSize -
-        compiler::target::InstructionsSection::HeaderSize();
-    WriteWordLiteralText(instructions_length);
-
-    if (profile_writer_ != nullptr) {
-      const intptr_t offset = Image::kHeaderSize;
-      const intptr_t non_instruction_bytes =
-          compiler::target::InstructionsSection::HeaderSize();
-      profile_writer_->SetObjectTypeAndName({offset_space_, offset},
-                                            "InstructionsSection",
-                                            /*name=*/nullptr);
-      profile_writer_->AttributeBytesTo({offset_space_, offset},
-                                        non_instruction_bytes);
-      profile_writer_->AddRoot({offset_space_, offset});
-    }
-  }
-
-  const intptr_t section_headers_size =
-      Image::kHeaderSize +
-      (bare_instruction_payloads
-           ? compiler::target::InstructionsSection::HeaderSize()
-           : 0);
-
   FrameUnwindPrologue();
 
   PcDescriptors& descriptors = PcDescriptors::Handle(zone);
@@ -665,19 +604,9 @@ void AssemblyImageWriter::WriteText(WriteStream* clustered_stream, bool vm) {
     const bool is_trampoline = data.trampoline_bytes != nullptr;
     ASSERT((data.text_offset_ - instructions_[0].text_offset_) == text_offset);
 
-    if (bare_instruction_payloads && profile_writer_ != nullptr) {
-      const intptr_t instructions_sections_offset = Image::kHeaderSize;
-      const intptr_t offset = section_headers_size + text_offset;
-      profile_writer_->AttributeReferenceTo(
-          {offset_space_, instructions_sections_offset},
-          {{offset_space_, offset},
-           V8SnapshotProfileWriter::Reference::kElement,
-           text_offset});
-    }
-
     if (is_trampoline) {
       if (profile_writer_ != nullptr) {
-        const intptr_t offset = section_headers_size + text_offset;
+        const intptr_t offset = Image::kHeaderSize + text_offset;
         profile_writer_->SetObjectTypeAndName({offset_space_, offset},
                                               "Trampolines",
                                               /*name=*/nullptr);
@@ -700,7 +629,7 @@ void AssemblyImageWriter::WriteText(WriteStream* clustered_stream, bool vm) {
     descriptors = data.code_->pc_descriptors();
 
     if (profile_writer_ != nullptr) {
-      const intptr_t offset = section_headers_size + text_offset;
+      const intptr_t offset = Image::kHeaderSize + text_offset;
       profile_writer_->SetObjectTypeAndName({offset_space_, offset},
                                             "Instructions",
                                             /*name=*/nullptr);
@@ -708,12 +637,9 @@ void AssemblyImageWriter::WriteText(WriteStream* clustered_stream, bool vm) {
                                         SizeInSnapshot(insns.raw()));
     }
 
-    const uword payload_start = insns.PayloadStart();
-
     // 1. Write from the object start to the payload start. This includes the
-    // object header and the fixed fields.  Not written for AOT snapshots using
+    // object header and the fixed fields.
-    // bare instructions.
+    {
-    if (!bare_instruction_payloads) {
       NoSafepointScope no_safepoint;
 
       // Write Instructions with the mark and read-only bits set.
@@ -730,7 +656,7 @@ void AssemblyImageWriter::WriteText(WriteStream* clustered_stream, bool vm) {
 #endif
 
 #if defined(IS_SIMARM_X64)
-      const intptr_t size_in_bytes = InstructionsSizeInSnapshot(insns.raw());
+      const intptr_t size_in_bytes = InstructionsSizeInSnapshot(insns.Size());
       marked_tags = RawObject::SizeTag::update(size_in_bytes * 2, marked_tags);
       WriteWordLiteralText(marked_tags);
       text_offset += sizeof(compiler::target::uword);
@@ -738,6 +664,7 @@ void AssemblyImageWriter::WriteText(WriteStream* clustered_stream, bool vm) {
       text_offset += sizeof(compiler::target::uword);
 #else   // defined(IS_SIMARM_X64)
       uword object_start = reinterpret_cast<uword>(insns.raw_ptr());
+      uword payload_start = insns.PayloadStart();
       WriteWordLiteralText(marked_tags);
       object_start += sizeof(uword);
       text_offset += sizeof(uword);
@@ -756,7 +683,7 @@ void AssemblyImageWriter::WriteText(WriteStream* clustered_stream, bool vm) {
     }
     if (debug_dwarf_ != nullptr) {
       auto const virtual_address =
-          debug_segment_base + section_headers_size + text_offset;
+          debug_segment_base + Image::kHeaderSize + text_offset;
       debug_dwarf_->AddCode(code, virtual_address);
     }
 #endif
@@ -765,29 +692,19 @@ void AssemblyImageWriter::WriteText(WriteStream* clustered_stream, bool vm) {
     assembly_stream_.Print("%s:\n", namer.AssemblyNameFor(dwarf_index, code));
 
     {
-      // 3. Write from the payload start to payload end. For AOT snapshots
+      // 3. Write from the payload start to payload end.
-      // with bare instructions, this is the only part serialized.
       NoSafepointScope no_safepoint;
-      assert(kBareInstructionsAlignment <=
+      const uword payload_start = insns.PayloadStart();
-             compiler::target::ObjectAlignment::kObjectAlignment);
+      const uword payload_size =
-      const auto payload_align = bare_instruction_payloads
+          Utils::RoundUp(insns.Size(), sizeof(compiler::target::uword));
-                                     ? kBareInstructionsAlignment
-                                     : sizeof(compiler::target::uword);
-      const uword payload_size = Utils::RoundUp(insns.Size(), payload_align);
       const uword payload_end = payload_start + payload_size;
 
-      ASSERT(Utils::IsAligned(text_offset, payload_align));
-
 #if defined(DART_PRECOMPILER)
       PcDescriptors::Iterator iterator(descriptors,
                                        RawPcDescriptors::kBSSRelocation);
       uword next_reloc_offset = iterator.MoveNext() ? iterator.PcOffset() : -1;
 
-      // We only generate BSS relocations that are word-sized and at
+      for (uword cursor = payload_start; cursor < payload_end;
-      // word-aligned offsets in the payload.
-      auto const possible_relocations_end =
-          Utils::RoundDown(payload_end, sizeof(compiler::target::uword));
-      for (uword cursor = payload_start; cursor < possible_relocations_end;
            cursor += sizeof(compiler::target::uword)) {
         compiler::target::uword data =
             *reinterpret_cast<compiler::target::uword*>(cursor);
@@ -799,8 +716,6 @@ void AssemblyImageWriter::WriteText(WriteStream* clustered_stream, bool vm) {
           WriteWordLiteralText(data);
         }
       }
-      assert(next_reloc_offset != (possible_relocations_end - payload_start));
-      WriteByteSequence(possible_relocations_end, payload_end);
       text_offset += payload_size;
 #else
       text_offset += WriteByteSequence(payload_start, payload_end);
@@ -808,43 +723,26 @@ void AssemblyImageWriter::WriteText(WriteStream* clustered_stream, bool vm) {
 
       // 4. Write from the payload end to object end. Note we can't simply copy
       // from the object because the host object may have less alignment filler
-      // than the target object in the cross-word case. Not written for AOT
+      // than the target object in the cross-word case.
-      // snapshots using bare instructions.
+      uword unaligned_size =
-      if (!bare_instruction_payloads) {
+          compiler::target::Instructions::HeaderSize() + payload_size;
-        uword unaligned_size =
+      uword alignment_size =
-            compiler::target::Instructions::HeaderSize() + payload_size;
+          Utils::RoundUp(unaligned_size,
-        uword alignment_size =
+                         compiler::target::ObjectAlignment::kObjectAlignment) -
-            Utils::RoundUp(
+          unaligned_size;
-                unaligned_size,
+      while (alignment_size > 0) {
-                compiler::target::ObjectAlignment::kObjectAlignment) -
+        WriteWordLiteralText(compiler::Assembler::GetBreakInstructionFiller());
-            unaligned_size;
+        alignment_size -= sizeof(compiler::target::uword);
-        while (alignment_size > 0) {
+        text_offset += sizeof(compiler::target::uword);
-          WriteWordLiteralText(
-              compiler::Assembler::GetBreakInstructionFiller());
-          alignment_size -= sizeof(compiler::target::uword);
-          text_offset += sizeof(compiler::target::uword);
-        }
-
-        ASSERT(kWordSize != compiler::target::kWordSize ||
-               (text_offset - instr_start) == insns.raw()->HeapSize());
       }
+
+      ASSERT(kWordSize != compiler::target::kWordSize ||
+             (text_offset - instr_start) == insns.raw()->HeapSize());
     }
 
     ASSERT((text_offset - instr_start) == SizeInSnapshot(insns.raw()));
   }
 
-  // Should be a no-op unless writing bare instruction payloads, in which case
-  // we need to add post-payload padding to the object alignment.
-  text_offset +=
-      Align(compiler::target::ObjectAlignment::kObjectAlignment, text_offset);
-
-  ASSERT(Image::kHeaderSize +
-             (bare_instruction_payloads
-                  ? compiler::target::InstructionsSection::HeaderSize()
-                  : 0) +
-             text_offset ==
-         image_size);
-
   FrameUnwindEpilogue();
 
 #if defined(DART_PRECOMPILER)
@@ -865,7 +763,7 @@ void AssemblyImageWriter::WriteText(WriteStream* clustered_stream, bool vm) {
     // we can pass nullptr for the bytes of the section/segment.
     auto const debug_segment_base2 =
         debug_dwarf_->elf()->AddText(instructions_symbol, /*bytes=*/nullptr,
-                                     section_headers_size + text_offset);
+                                     Image::kHeaderSize + text_offset);
     ASSERT(debug_segment_base2 == debug_segment_base);
   }
 
@@ -890,7 +788,7 @@ void AssemblyImageWriter::WriteText(WriteStream* clustered_stream, bool vm) {
   const char* data_symbol =
       vm ? "_kDartVmSnapshotData" : "_kDartIsolateSnapshotData";
   assembly_stream_.Print(".globl %s\n", data_symbol);
-  Align(kMaxObjectAlignment);
+  assembly_stream_.Print(".balign %" Pd ", 0\n", kMaxObjectAlignment);
   assembly_stream_.Print("%s:\n", data_symbol);
   uword buffer = reinterpret_cast<uword>(clustered_stream->buffer());
   intptr_t length = clustered_stream->bytes_written();
@@ -976,33 +874,13 @@ void AssemblyImageWriter::FrameUnwindEpilogue() {
 }
 
 intptr_t AssemblyImageWriter::WriteByteSequence(uword start, uword end) {
-  assert(end >= start);
+  for (auto* cursor = reinterpret_cast<compiler::target::uword*>(start);
-  auto const end_of_words =
+       cursor < reinterpret_cast<compiler::target::uword*>(end); cursor++) {
-      Utils::RoundDown(end, sizeof(compiler::target::uword));
-  for (auto cursor = reinterpret_cast<compiler::target::uword*>(start);
-       cursor < reinterpret_cast<compiler::target::uword*>(end_of_words);
-       cursor++) {
     WriteWordLiteralText(*cursor);
   }
-  if (end != end_of_words) {
-    auto start_of_rest = reinterpret_cast<const uint8_t*>(end_of_words);
-    assembly_stream_.Print(".byte ");
-    for (auto cursor = start_of_rest;
-         cursor < reinterpret_cast<const uint8_t*>(end); cursor++) {
-      if (cursor != start_of_rest) assembly_stream_.Print(", ");
-      assembly_stream_.Print("0x%0.2" Px "", *cursor);
-    }
-    assembly_stream_.Print("\n");
-  }
   return end - start;
 }
 
-intptr_t AssemblyImageWriter::Align(intptr_t alignment, uword position) {
-  const uword next_position = Utils::RoundUp(position, alignment);
-  assembly_stream_.Print(".balign %" Pd ", 0\n", alignment);
-  return next_position - position;
-}
-
 BlobImageWriter::BlobImageWriter(Thread* thread,
                                  uint8_t** instructions_blob_buffer,
                                  ReAlloc alloc,
@@ -1034,9 +912,7 @@ intptr_t BlobImageWriter::WriteByteSequence(uword start, uword end) {
 }
 
 void BlobImageWriter::WriteText(WriteStream* clustered_stream, bool vm) {
-  const bool bare_instruction_payloads =
+  const intptr_t instructions_length = next_text_offset_;
-      FLAG_precompiled_mode && FLAG_use_bare_instructions;
-
 #ifdef DART_PRECOMPILER
   intptr_t segment_base = 0;
   if (elf_ != nullptr) {
@@ -1050,9 +926,7 @@ void BlobImageWriter::WriteText(WriteStream* clustered_stream, bool vm) {
 
   // This header provides the gap to make the instructions snapshot look like a
   // HeapPage.
-  const intptr_t image_size = Utils::RoundUp(
+  instructions_blob_stream_.WriteTargetWord(instructions_length);
-      next_text_offset_, compiler::target::ObjectAlignment::kObjectAlignment);
-  instructions_blob_stream_.WriteTargetWord(image_size);
 #if defined(DART_PRECOMPILER)
   instructions_blob_stream_.WriteTargetWord(
       elf_ != nullptr ? bss_base_ - segment_base : 0);
@@ -1065,36 +939,6 @@ void BlobImageWriter::WriteText(WriteStream* clustered_stream, bool vm) {
     instructions_blob_stream_.WriteTargetWord(0);
   }
 
-  if (bare_instruction_payloads) {
-    const intptr_t image_payload_length = image_size - Image::kHeaderSize;
-    // Add the RawInstructionsSection header.
-    uword marked_tags = 0;
-    marked_tags = RawObject::OldBit::update(true, marked_tags);
-    marked_tags = RawObject::OldAndNotRememberedBit::update(true, marked_tags);
-    marked_tags = RawObject::SizeTag::update(image_payload_length, marked_tags);
-    marked_tags =
-        RawObject::ClassIdTag::update(kInstructionsSectionCid, marked_tags);
-
-    instructions_blob_stream_.WriteTargetWord(marked_tags);
-    // Uses next_text_offset_ to avoid any post-payload padding.
-    const intptr_t instructions_length =
-        next_text_offset_ - Image::kHeaderSize -
-        compiler::target::InstructionsSection::HeaderSize();
-    instructions_blob_stream_.WriteTargetWord(instructions_length);
-
-    if (profile_writer_ != nullptr) {
-      const intptr_t offset = Image::kHeaderSize;
-      const intptr_t non_instruction_bytes =
-          compiler::target::InstructionsSection::HeaderSize();
-      profile_writer_->SetObjectTypeAndName({offset_space_, offset},
-                                            "InstructionsSection",
-                                            /*name=*/nullptr);
-      profile_writer_->AttributeBytesTo({offset_space_, offset},
-                                        non_instruction_bytes);
-      profile_writer_->AddRoot({offset_space_, offset});
-    }
-  }
-
   intptr_t text_offset = 0;
 
 #if defined(DART_PRECOMPILER)
@@ -1108,15 +952,6 @@ void BlobImageWriter::WriteText(WriteStream* clustered_stream, bool vm) {
     const bool is_trampoline = data.trampoline_bytes != nullptr;
     ASSERT((data.text_offset_ - instructions_[0].text_offset_) == text_offset);
 
-    if (bare_instruction_payloads && profile_writer_ != nullptr) {
-      const intptr_t instructions_sections_offset = Image::kHeaderSize;
-      profile_writer_->AttributeReferenceTo(
-          {offset_space_, instructions_sections_offset},
-          {{offset_space_, instructions_blob_stream_.Position()},
-           V8SnapshotProfileWriter::Reference::kElement,
-           text_offset});
-    }
-
     if (is_trampoline) {
       const auto start = reinterpret_cast<uword>(data.trampoline_bytes);
       const auto end = start + data.trampline_length;
@@ -1130,9 +965,17 @@ void BlobImageWriter::WriteText(WriteStream* clustered_stream, bool vm) {
 
     const Instructions& insns = *instructions_[i].insns_;
     AutoTraceImage(insns, 0, &this->instructions_blob_stream_);
-    const uword payload_start = insns.PayloadStart();
 
-    ASSERT(Utils::IsAligned(payload_start, sizeof(compiler::target::uword)));
+    uword object_start = reinterpret_cast<uword>(insns.raw_ptr());
+    uword payload_start = insns.PayloadStart();
+    uword payload_size =
+        Utils::RoundUp(
+            compiler::target::Instructions::HeaderSize() + insns.Size(),
+            compiler::target::ObjectAlignment::kObjectAlignment) -
+        compiler::target::Instructions::HeaderSize();
+    uword object_end = payload_start + payload_size;
+
+    ASSERT(Utils::IsAligned(payload_start, sizeof(uword)));
 
     // Write Instructions with the mark and read-only bits set.
     uword marked_tags = insns.raw_ptr()->tags_;
@@ -1146,49 +989,32 @@ void BlobImageWriter::WriteText(WriteStream* clustered_stream, bool vm) {
     marked_tags |= static_cast<uword>(insns.raw_ptr()->hash_) << 32;
 #endif
 
+    intptr_t payload_stream_start = 0;
+
 #if defined(IS_SIMARM_X64)
     const intptr_t start_offset = instructions_blob_stream_.bytes_written();
-    const intptr_t size_in_bytes = InstructionsSizeInSnapshot(insns.raw());
+    const intptr_t size_in_bytes = InstructionsSizeInSnapshot(insns.Size());
     marked_tags = RawObject::SizeTag::update(size_in_bytes * 2, marked_tags);
-
+    instructions_blob_stream_.WriteTargetWord(marked_tags);
-    if (!bare_instruction_payloads) {
+    instructions_blob_stream_.WriteFixed<uint32_t>(
-      instructions_blob_stream_.WriteTargetWord(marked_tags);
+        insns.raw_ptr()->size_and_flags_);
-      instructions_blob_stream_.WriteFixed<uint32_t>(
+    payload_stream_start = instructions_blob_stream_.Position();
-          insns.raw_ptr()->size_and_flags_);
-    } else {
-      ASSERT(Utils::IsAligned(instructions_blob_stream_.Position(),
-                              kBareInstructionsAlignment));
-    }
-    const intptr_t payload_stream_start = instructions_blob_stream_.Position();
     instructions_blob_stream_.WriteBytes(
         reinterpret_cast<const void*>(insns.PayloadStart()), insns.Size());
-    const intptr_t alignment =
+    instructions_blob_stream_.Align(
-        bare_instruction_payloads
+        compiler::target::ObjectAlignment::kObjectAlignment);
-            ? kBareInstructionsAlignment
-            : compiler::target::ObjectAlignment::kObjectAlignment;
-    instructions_blob_stream_.Align(alignment);
     const intptr_t end_offset = instructions_blob_stream_.bytes_written();
     text_offset += (end_offset - start_offset);
+    USE(object_start);
+    USE(object_end);
 #else   // defined(IS_SIMARM_X64)
-    // Only payload is output in AOT snapshots.
+    payload_stream_start = instructions_blob_stream_.Position() +
-    const uword header_size =
+                           (insns.PayloadStart() - object_start);
-        bare_instruction_payloads
+
-            ? 0
+    instructions_blob_stream_.WriteWord(marked_tags);
-            : compiler::target::Instructions::HeaderSize();
+    text_offset += sizeof(uword);
-    const uword payload_size = SizeInSnapshot(insns.raw()) - header_size;
+    object_start += sizeof(uword);
-    const uword object_end = payload_start + payload_size;
+    text_offset += WriteByteSequence(object_start, object_end);
-    if (!bare_instruction_payloads) {
-      uword object_start = reinterpret_cast<uword>(insns.raw_ptr());
-      instructions_blob_stream_.WriteWord(marked_tags);
-      text_offset += sizeof(uword);
-      object_start += sizeof(uword);
-      text_offset += WriteByteSequence(object_start, payload_start);
-    } else {
-      ASSERT(Utils::IsAligned(instructions_blob_stream_.Position(),
-                              kBareInstructionsAlignment));
-    }
-    const intptr_t payload_stream_start = instructions_blob_stream_.Position();
-    text_offset += WriteByteSequence(payload_start, object_end);
 #endif
 
 #if defined(DART_PRECOMPILER)
@@ -1250,12 +1076,7 @@ void BlobImageWriter::WriteText(WriteStream* clustered_stream, bool vm) {
            ImageWriter::SizeInSnapshot(insns.raw()));
   }
 
-  // Should be a no-op unless writing bare instruction payloads, in which case
+  ASSERT(instructions_blob_stream_.bytes_written() == instructions_length);
-  // we need to add post-payload padding to the object alignment.
-  instructions_blob_stream_.Align(
-      compiler::target::ObjectAlignment::kObjectAlignment);
-
-  ASSERT(instructions_blob_stream_.bytes_written() == image_size);
 
 #ifdef DART_PRECOMPILER
   const char* instructions_symbol =
@@ -1293,18 +1114,6 @@ RawApiError* ImageReader::VerifyAlignment() const {
   return ApiError::null();
 }
 
-#if defined(DART_PRECOMPILED_RUNTIME)
-uword ImageReader::GetBareInstructionsAt(uint32_t offset) const {
-  ASSERT(Utils::IsAligned(offset, ImageWriter::kBareInstructionsAlignment));
-  return reinterpret_cast<uword>(instructions_image_) + offset;
-}
-
-uword ImageReader::GetBareInstructionsEnd() const {
-  Image image(instructions_image_);
-  return reinterpret_cast<uword>(image.object_start()) + image.object_size();
-}
-#endif
-
 RawInstructions* ImageReader::GetInstructionsAt(uint32_t offset) const {
   ASSERT(Utils::IsAligned(offset, kObjectAlignment));
 

runtime/vm/image_snapshot.h

@@ -69,8 +69,6 @@ class ImageReader : public ZoneAllocated {
 
   RawApiError* VerifyAlignment() const;
 
-  ONLY_IN_PRECOMPILED(uword GetBareInstructionsAt(uint32_t offset) const);
-  ONLY_IN_PRECOMPILED(uword GetBareInstructionsEnd() const);
   RawInstructions* GetInstructionsAt(uint32_t offset) const;
   RawObject* GetObjectAt(uint32_t offset) const;
 
@@ -155,9 +153,6 @@ class ImageWriter : public ValueObject {
   void ResetOffsets() {
     next_data_offset_ = Image::kHeaderSize;
     next_text_offset_ = Image::kHeaderSize;
-    if (FLAG_use_bare_instructions && FLAG_precompiled_mode) {
-      next_text_offset_ += compiler::target::InstructionsSection::HeaderSize();
-    }
     objects_.Clear();
     instructions_.Clear();
   }
@@ -184,7 +179,6 @@ class ImageWriter : public ValueObject {
   void TraceInstructions(const Instructions& instructions);
 
   static intptr_t SizeInSnapshot(RawObject* object);
-  static const intptr_t kBareInstructionsAlignment = 4;
 
  protected:
   void WriteROData(WriteStream* stream);
@@ -335,7 +329,6 @@ class AssemblyImageWriter : public ImageWriter {
   void FrameUnwindPrologue();
   void FrameUnwindEpilogue();
   intptr_t WriteByteSequence(uword start, uword end);
-  intptr_t Align(intptr_t alignment, uword position = 0);
 
 #if defined(TARGET_ARCH_IS_64_BIT)
   const char* kLiteralPrefix = ".quad";

runtime/vm/object.cc

@@ -150,8 +150,6 @@ RawClass* Object::kernel_program_info_class_ =
 RawClass* Object::code_class_ = reinterpret_cast<RawClass*>(RAW_NULL);
 RawClass* Object::bytecode_class_ = reinterpret_cast<RawClass*>(RAW_NULL);
 RawClass* Object::instructions_class_ = reinterpret_cast<RawClass*>(RAW_NULL);
-RawClass* Object::instructions_section_class_ =
-    reinterpret_cast<RawClass*>(RAW_NULL);
 RawClass* Object::object_pool_class_ = reinterpret_cast<RawClass*>(RAW_NULL);
 RawClass* Object::pc_descriptors_class_ = reinterpret_cast<RawClass*>(RAW_NULL);
 RawClass* Object::code_source_map_class_ =
@@ -795,9 +793,6 @@ void Object::Init(Isolate* isolate) {
   cls = Class::New<Instructions, RTN::Instructions>(isolate);
   instructions_class_ = cls.raw();
 
-  cls = Class::New<InstructionsSection, RTN::InstructionsSection>(isolate);
-  instructions_section_class_ = cls.raw();
-
   cls = Class::New<ObjectPool, RTN::ObjectPool>(isolate);
   object_pool_class_ = cls.raw();
 
@@ -1226,7 +1221,6 @@ void Object::Cleanup() {
   code_class_ = reinterpret_cast<RawClass*>(RAW_NULL);
   bytecode_class_ = reinterpret_cast<RawClass*>(RAW_NULL);
   instructions_class_ = reinterpret_cast<RawClass*>(RAW_NULL);
-  instructions_section_class_ = reinterpret_cast<RawClass*>(RAW_NULL);
   object_pool_class_ = reinterpret_cast<RawClass*>(RAW_NULL);
   pc_descriptors_class_ = reinterpret_cast<RawClass*>(RAW_NULL);
   code_source_map_class_ = reinterpret_cast<RawClass*>(RAW_NULL);
@@ -1329,7 +1323,6 @@ void Object::FinalizeVMIsolate(Isolate* isolate) {
   SET_CLASS_NAME(code, Code);
   SET_CLASS_NAME(bytecode, Bytecode);
   SET_CLASS_NAME(instructions, Instructions);
-  SET_CLASS_NAME(instructions_section, InstructionsSection);
   SET_CLASS_NAME(object_pool, ObjectPool);
   SET_CLASS_NAME(code_source_map, CodeSourceMap);
   SET_CLASS_NAME(pc_descriptors, PcDescriptors);
@@ -4543,8 +4536,6 @@ const char* Class::GenerateUserVisibleName() const {
       return Symbols::Bytecode().ToCString();
     case kInstructionsCid:
       return Symbols::Instructions().ToCString();
-    case kInstructionsSectionCid:
-      return Symbols::InstructionsSection().ToCString();
     case kObjectPoolCid:
       return Symbols::ObjectPool().ToCString();
     case kCodeSourceMapCid:
@@ -13117,7 +13108,7 @@ void Library::CheckFunctionFingerprints() {
 }
 #endif  // defined(DEBUG) && !defined(DART_PRECOMPILED_RUNTIME).
 
-RawInstructions* Instructions::New(intptr_t size, bool has_monomorphic_entry) {
+RawInstructions* Instructions::New(intptr_t size, bool has_single_entry_point) {
   ASSERT(size >= 0);
   ASSERT(Object::instructions_class() != Class::null());
   if (size < 0 || size > kMaxElements) {
@@ -13132,7 +13123,7 @@ RawInstructions* Instructions::New(intptr_t size, bool has_monomorphic_entry) {
     NoSafepointScope no_safepoint;
     result ^= raw;
     result.SetSize(size);
-    result.SetHasMonomorphicEntry(has_monomorphic_entry);
+    result.SetHasSingleEntryPoint(has_single_entry_point);
     result.set_stats(nullptr);
   }
   return result.raw();
@@ -13157,10 +13148,6 @@ void Instructions::set_stats(CodeStatistics* stats) const {
 #endif
 }
 
-const char* InstructionsSection::ToCString() const {
-  return "InstructionsSection";
-}
-
 // Encode integer |value| in SLEB128 format and store into |data|.
 static void EncodeSLEB128(GrowableArray<uint8_t>* data, intptr_t value) {
   bool is_last_part = false;
@@ -15338,11 +15325,12 @@ void Code::Disassemble(DisassemblyFormatter* formatter) const {
   if (!FLAG_support_disassembler) {
     return;
   }
-  const uword start = PayloadStart();
+  const Instructions& instr = Instructions::Handle(instructions());
+  uword start = instr.PayloadStart();
   if (formatter == NULL) {
-    Disassembler::Disassemble(start, start + Size(), *this);
+    Disassembler::Disassemble(start, start + instr.Size(), *this);
   } else {
-    Disassembler::Disassemble(start, start + Size(), formatter, *this);
+    Disassembler::Disassemble(start, start + instr.Size(), formatter, *this);
   }
 #endif  // !defined(PRODUCT) || defined(FORCE_INCLUDE_DISASSEMBLER)
 }
@@ -15482,7 +15470,7 @@ RawCode* Code::FinalizeCode(FlowGraphCompiler* compiler,
   assembler->GetSelfHandle() = code.raw();
 #endif
   Instructions& instrs = Instructions::ZoneHandle(Instructions::New(
-      assembler->CodeSize(), assembler->has_monomorphic_entry()));
+      assembler->CodeSize(), assembler->has_single_entry_point()));
 
   {
     // Important: if GC is triggerred at any point between Instructions::New
@@ -15883,10 +15871,11 @@ void Code::DumpSourcePositions(bool relative_addresses) const {
 
 bool Code::VerifyBSSRelocations() const {
   const auto& descriptors = PcDescriptors::Handle(pc_descriptors());
+  const auto& insns = Instructions::Handle(instructions());
   PcDescriptors::Iterator iterator(descriptors,
                                    RawPcDescriptors::kBSSRelocation);
   while (iterator.MoveNext()) {
-    const uword reloc = PayloadStart() + iterator.PcOffset();
+    const uword reloc = insns.PayloadStart() + iterator.PcOffset();
     const word target = *reinterpret_cast<word*>(reloc);
     // The relocation is in its original unpatched form -- the addend
     // representing the target symbol itself.

runtime/vm/object.h

@@ -482,9 +482,6 @@ class Object {
   static RawClass* code_class() { return code_class_; }
   static RawClass* bytecode_class() { return bytecode_class_; }
   static RawClass* instructions_class() { return instructions_class_; }
-  static RawClass* instructions_section_class() {
-    return instructions_section_class_;
-  }
   static RawClass* object_pool_class() { return object_pool_class_; }
   static RawClass* pc_descriptors_class() { return pc_descriptors_class_; }
   static RawClass* code_source_map_class() { return code_source_map_class_; }
@@ -769,8 +766,6 @@ class Object {
   static RawClass* code_class_;                 // Class of the Code vm object.
   static RawClass* bytecode_class_;      // Class of the Bytecode vm object.
   static RawClass* instructions_class_;  // Class of the Instructions vm object.
-  static RawClass*
-      instructions_section_class_;       // Class of InstructionsSection.
   static RawClass* object_pool_class_;   // Class of the ObjectPool vm object.
   static RawClass* pc_descriptors_class_;   // Class of PcDescriptors vm object.
   static RawClass* code_source_map_class_;  // Class of CodeSourceMap vm object.
@@ -5057,13 +5052,21 @@ class Instructions : public Object {
     return SizeBits::decode(instr->ptr()->size_and_flags_);
   }
 
-  bool HasMonomorphicEntry() const {
+  bool HasSingleEntryPoint() const {
     return FlagsBits::decode(raw_ptr()->size_and_flags_);
   }
-  static bool HasMonomorphicEntry(const RawInstructions* instr) {
+  static bool HasSingleEntryPoint(const RawInstructions* instr) {
     return FlagsBits::decode(instr->ptr()->size_and_flags_);
   }
 
+  static bool ContainsPc(RawInstructions* instruction, uword pc) {
+    const uword offset = pc - PayloadStart(instruction);
+    // We use <= instead of < here because the saved-pc can be outside the
+    // instruction stream if the last instruction is a call we don't expect to
+    // return (e.g. because it throws an exception).
+    return offset <= static_cast<uword>(Size(instruction));
+  }
+
   uword PayloadStart() const { return PayloadStart(raw()); }
   uword MonomorphicEntryPoint() const { return MonomorphicEntryPoint(raw()); }
   uword EntryPoint() const { return EntryPoint(raw()); }
@@ -5099,7 +5102,7 @@ class Instructions : public Object {
 
   static uword MonomorphicEntryPoint(const RawInstructions* instr) {
     uword entry = PayloadStart(instr);
-    if (HasMonomorphicEntry(instr)) {
+    if (!HasSingleEntryPoint(instr)) {
       entry += !FLAG_precompiled_mode ? kMonomorphicEntryOffsetJIT
                                       : kMonomorphicEntryOffsetAOT;
     }
@@ -5108,7 +5111,7 @@ class Instructions : public Object {
 
   static uword EntryPoint(const RawInstructions* instr) {
     uword entry = PayloadStart(instr);
-    if (HasMonomorphicEntry(instr)) {
+    if (!HasSingleEntryPoint(instr)) {
       entry += !FLAG_precompiled_mode ? kPolymorphicEntryOffsetJIT
                                       : kPolymorphicEntryOffsetAOT;
     }
@@ -5158,7 +5161,7 @@ class Instructions : public Object {
                     SizeBits::update(value, raw_ptr()->size_and_flags_));
   }
 
-  void SetHasMonomorphicEntry(bool value) const {
+  void SetHasSingleEntryPoint(bool value) const {
     StoreNonPointer(&raw_ptr()->size_and_flags_,
                     FlagsBits::update(value, raw_ptr()->size_and_flags_));
   }
@@ -5167,7 +5170,7 @@ class Instructions : public Object {
   // only be created using the Code::FinalizeCode method. This method creates
   // the RawInstruction and RawCode objects, sets up the pointer offsets
   // and links the two in a GC safe manner.
-  static RawInstructions* New(intptr_t size, bool has_monomorphic_entry);
+  static RawInstructions* New(intptr_t size, bool has_single_entry_point);
 
   FINAL_HEAP_OBJECT_IMPLEMENTATION(Instructions, Object);
   friend class Class;
@@ -5177,34 +5180,6 @@ class Instructions : public Object {
   friend class ImageWriter;
 };
 
-// Used only to provide memory accounting for the bare instruction payloads
-// we serialize, since they are no longer part of RawInstructions objects.
-class InstructionsSection : public Object {
- public:
-  // Excludes HeaderSize().
-  intptr_t Size() const { return raw_ptr()->payload_length_; }
-  static intptr_t Size(const RawInstructionsSection* instr) {
-    return instr->ptr()->payload_length_;
-  }
-  static intptr_t InstanceSize() {
-    ASSERT(sizeof(RawInstructionsSection) ==
-           OFFSET_OF_RETURNED_VALUE(RawInstructionsSection, data));
-    return 0;
-  }
-
-  static intptr_t InstanceSize(intptr_t size) {
-    return Utils::RoundUp(HeaderSize() + size, kObjectAlignment);
-  }
-
-  static intptr_t HeaderSize() {
-    return Utils::RoundUp(sizeof(RawInstructionsSection), kWordSize);
-  }
-
- private:
-  FINAL_HEAP_OBJECT_IMPLEMENTATION(InstructionsSection, Object);
-  friend class Class;
-};
-
 class LocalVarDescriptors : public Object {
  public:
   intptr_t Length() const;
@@ -5580,6 +5555,11 @@ class Code : public Object {
     return code->ptr()->instructions_;
   }
 
+  // Returns the entry point of [InstructionsOf(code)].
+  static uword EntryPointOf(const RawCode* code) {
+    return Instructions::EntryPoint(InstructionsOf(code));
+  }
+
   static intptr_t saved_instructions_offset() {
     return OFFSET_OF(RawCode, instructions_);
   }
@@ -5629,38 +5609,12 @@ class Code : public Object {
   bool is_alive() const { return AliveBit::decode(raw_ptr()->state_bits_); }
   void set_is_alive(bool value) const;
 
-  bool HasMonomorphicEntry() const { return HasMonomorphicEntry(raw()); }
-  static bool HasMonomorphicEntry(const RawCode* code) {
-#if defined(DART_PRECOMPILED_RUNTIME)
-    return code->ptr()->entry_point_ != code->ptr()->monomorphic_entry_point_;
-#else
-    return Instructions::HasMonomorphicEntry(InstructionsOf(code));
-#endif
-  }
-
   // Returns the payload start of [instructions()].
-  uword PayloadStart() const { return PayloadStartOf(raw()); }
+  uword PayloadStart() const {
-  static uword PayloadStartOf(const RawCode* code) {
+    return Instructions::PayloadStart(instructions());
-#if defined(DART_PRECOMPILED_RUNTIME)
-    const uword entry_offset = HasMonomorphicEntry(code)
-                                   ? Instructions::kPolymorphicEntryOffsetAOT
-                                   : 0;
-    return EntryPointOf(code) - entry_offset;
-#else
-    return Instructions::PayloadStart(InstructionsOf(code));
-#endif
   }
-
   // Returns the entry point of [instructions()].
-  uword EntryPoint() const { return EntryPointOf(raw()); }
+  uword EntryPoint() const { return Instructions::EntryPoint(instructions()); }
-  static uword EntryPointOf(const RawCode* code) {
-#if defined(DART_PRECOMPILED_RUNTIME)
-    return code->ptr()->entry_point_;
-#else
-    return Instructions::EntryPoint(InstructionsOf(code));
-#endif
-  }
-
   // Returns the unchecked entry point of [instructions()].
   uword UncheckedEntryPoint() const {
 #if defined(DART_PRECOMPILED_RUNTIME)
@@ -5671,11 +5625,7 @@ class Code : public Object {
   }
   // Returns the monomorphic entry point of [instructions()].
   uword MonomorphicEntryPoint() const {
-#if defined(DART_PRECOMPILED_RUNTIME)
-    return raw_ptr()->monomorphic_entry_point_;
-#else
     return Instructions::MonomorphicEntryPoint(instructions());
-#endif
   }
   // Returns the unchecked monomorphic entry point of [instructions()].
   uword MonomorphicUncheckedEntryPoint() const {
@@ -5685,16 +5635,8 @@ class Code : public Object {
     return MonomorphicEntryPoint() + raw_ptr()->unchecked_offset_;
 #endif
   }
-
   // Returns the size of [instructions()].
-  intptr_t Size() const { return PayloadSizeOf(raw()); }
+  intptr_t Size() const { return Instructions::Size(instructions()); }
-  static intptr_t PayloadSizeOf(const RawCode* code) {
-#if defined(DART_PRECOMPILED_RUNTIME)
-    return code->ptr()->instructions_length_;
-#else
-    return Instructions::Size(InstructionsOf(code));
-#endif
-  }
 
   RawObjectPool* GetObjectPool() const;
   // Returns whether the given PC address is in [instructions()].
@@ -5703,8 +5645,8 @@ class Code : public Object {
   }
 
   // Returns whether the given PC address is in [InstructionsOf(code)].
-  static bool ContainsInstructionAt(const RawCode* code, uword pc) {
+  static bool ContainsInstructionAt(const RawCode* code, uword addr) {
-    return RawCode::ContainsPC(code, pc);
+    return Instructions::ContainsPc(InstructionsOf(code), addr);
   }
 
   // Returns true if there is a debugger breakpoint set in this code object.
@@ -6108,13 +6050,11 @@ class Code : public Object {
 
   // Returns the unchecked entry point offset for [instructions_].
   uint32_t UncheckedEntryPointOffset() const {
-    return UncheckedEntryPointOffsetOf(raw());
-  }
-  static uint32_t UncheckedEntryPointOffsetOf(RawCode* code) {
 #if defined(DART_PRECOMPILED_RUNTIME)
     UNREACHABLE();
+    return raw_ptr()->unchecked_entry_point_ - raw_ptr()->entry_point_;
 #else
-    return code->ptr()->unchecked_offset_;
+    return raw_ptr()->unchecked_offset_;
 #endif
   }
 
@@ -6152,7 +6092,6 @@ class Code : public Object {
   friend class FunctionSerializationCluster;
   friend class CodeSerializationCluster;
   friend class CodeDeserializationCluster;
-  friend class Deserializer;           // for InitializeCachedEntryPointsFrom
   friend class StubCode;               // for set_object_pool
   friend class MegamorphicCacheTable;  // for set_object_pool
   friend class CodePatcher;            // for set_instructions

runtime/vm/object_service.cc

@@ -667,10 +667,6 @@ void Instructions::PrintJSONImpl(JSONStream* stream, bool ref) const {
   }
 }
 
-void InstructionsSection::PrintJSONImpl(JSONStream* stream, bool ref) const {
-  Object::PrintJSONImpl(stream, ref);
-}
-
 void ObjectPool::PrintJSONImpl(JSONStream* stream, bool ref) const {
   JSONObject jsobj(stream);
   AddCommonObjectProperties(&jsobj, "Object", ref);

runtime/vm/raw_object.cc

@@ -100,13 +100,6 @@ intptr_t RawObject::HeapSizeFromClass() const {
       instance_size = Instructions::InstanceSize(instructions_size);
       break;
     }
-    case kInstructionsSectionCid: {
-      const RawInstructionsSection* raw_section =
-          reinterpret_cast<const RawInstructionsSection*>(this);
-      intptr_t section_size = InstructionsSection::Size(raw_section);
-      instance_size = InstructionsSection::InstanceSize(section_size);
-      break;
-    }
     case kContextCid: {
       const RawContext* raw_context = reinterpret_cast<const RawContext*>(this);
       intptr_t num_variables = raw_context->ptr()->num_variables_;
@@ -556,7 +549,6 @@ NULL_VISITOR(TransferableTypedData)
 REGULAR_VISITOR(Pointer)
 NULL_VISITOR(DynamicLibrary)
 VARIABLE_NULL_VISITOR(Instructions, Instructions::Size(raw_obj))
-VARIABLE_NULL_VISITOR(InstructionsSection, InstructionsSection::Size(raw_obj))
 VARIABLE_NULL_VISITOR(PcDescriptors, raw_obj->ptr()->length_)
 VARIABLE_NULL_VISITOR(CodeSourceMap, raw_obj->ptr()->length_)
 VARIABLE_NULL_VISITOR(CompressedStackMaps, raw_obj->ptr()->payload_size())
@@ -572,12 +564,12 @@ UNREACHABLE_VISITOR(String)
 // Smi has no heap representation.
 UNREACHABLE_VISITOR(Smi)
 
-bool RawCode::ContainsPC(const RawObject* raw_obj, uword pc) {
+bool RawCode::ContainsPC(RawObject* raw_obj, uword pc) {
-  if (!raw_obj->IsCode()) return false;
+  if (raw_obj->IsCode()) {
-  auto const raw_code = static_cast<const RawCode*>(raw_obj);
+    RawCode* raw_code = static_cast<RawCode*>(raw_obj);
-  const uword start = Code::PayloadStartOf(raw_code);
+    return RawInstructions::ContainsPC(raw_code->ptr()->instructions_, pc);
-  const uword size = Code::PayloadSizeOf(raw_code);
+  }
-  return (pc - start) <= size;  // pc may point just past last instruction.
+  return false;
 }
 
 intptr_t RawCode::VisitCodePointers(RawCode* raw_obj,
@@ -591,7 +583,8 @@ intptr_t RawCode::VisitCodePointers(RawCode* raw_obj,
   // instructions. The variable portion of a Code object describes where to
   // find those pointers for tracing.
   if (Code::AliveBit::decode(obj->state_bits_)) {
-    uword entry_point = Code::PayloadStartOf(raw_obj);
+    uword entry_point = reinterpret_cast<uword>(obj->instructions_->ptr()) +
+                        Instructions::HeaderSize();
     for (intptr_t i = 0; i < length; i++) {
       int32_t offset = obj->data()[i];
       visitor->VisitPointer(
@@ -633,13 +626,12 @@ intptr_t RawObjectPool::VisitObjectPoolPointers(RawObjectPool* raw_obj,
   return ObjectPool::InstanceSize(length);
 }
 
-bool RawInstructions::ContainsPC(const RawInstructions* raw_instr, uword pc) {
+bool RawInstructions::ContainsPC(RawInstructions* raw_instr, uword pc) {
-  const uword start = Instructions::PayloadStart(raw_instr);
+  uword start_pc =
-  const uword size = Instructions::Size(raw_instr);
+      reinterpret_cast<uword>(raw_instr->ptr()) + Instructions::HeaderSize();
-  // We use <= instead of < here because the saved-pc can be outside the
+  uword end_pc = start_pc + Instructions::Size(raw_instr);
-  // instruction stream if the last instruction is a call we don't expect to
+  ASSERT(end_pc > start_pc);
-  // return (e.g. because it throws an exception).
+  return (pc >= start_pc) && (pc < end_pc);
-  return (pc - start) <= size;
 }
 
 intptr_t RawInstance::VisitInstancePointers(RawInstance* raw_obj,

runtime/vm/raw_object.h

@@ -1408,11 +1408,8 @@ class RawKernelProgramInfo : public RawObject {
 class RawCode : public RawObject {
   RAW_HEAP_OBJECT_IMPLEMENTATION(Code);
 
-  // When in the precompiled runtime, there is no disabling of Code objects
+  // When in the precompiled runtime, there is no active_instructions_ field
-  // and thus no active_instructions_ field. Thus, the entry point caches are
+  // and the entry point caches should contain entry points for instructions_.
-  // only set once during deserialization. If not using bare instructions,
-  // the caches should match the entry points for instructions_.
-  //
   // Otherwise, they should contain entry points for active_instructions_.
 
   uword entry_point_;  // Accessed from generated code.
@@ -1500,14 +1497,12 @@ class RawCode : public RawObject {
   // Caches the unchecked entry point offset for instructions_, in case we need
   // to reset the active_instructions_ to instructions_.
   NOT_IN_PRECOMPILED(uint32_t unchecked_offset_);
-  // Stores the instructions length when not using RawInstructions objects.
-  ONLY_IN_PRECOMPILED(uint32_t instructions_length_);
 
   // Variable length data follows here.
   int32_t* data() { OPEN_ARRAY_START(int32_t, int32_t); }
   const int32_t* data() const { OPEN_ARRAY_START(int32_t, int32_t); }
 
-  static bool ContainsPC(const RawObject* raw_obj, uword pc);
+  static bool ContainsPC(RawObject* raw_obj, uword pc);
 
   friend class Function;
   template <bool>
@@ -1589,7 +1584,7 @@ class RawInstructions : public RawObject {
   // Private helper function used while visiting stack frames. The
   // code which iterates over dart frames is also called during GC and
   // is not allowed to create handles.
-  static bool ContainsPC(const RawInstructions* raw_instr, uword pc);
+  static bool ContainsPC(RawInstructions* raw_instr, uword pc);
 
   friend class RawCode;
   friend class RawFunction;
@@ -1604,19 +1599,6 @@ class RawInstructions : public RawObject {
   friend class BlobImageWriter;
 };
 
-// Used only to provide memory accounting for the bare instruction payloads
-// we serialize, since they are no longer part of RawInstructions objects.
-class RawInstructionsSection : public RawObject {
-  RAW_HEAP_OBJECT_IMPLEMENTATION(InstructionsSection);
-  VISIT_NOTHING();
-
-  // Instructions section payload length in bytes.
-  uint32_t payload_length_;
-
-  // Variable length data follows here.
-  uint8_t* data() { OPEN_ARRAY_START(uint8_t, uint8_t); }
-};
-
 class RawPcDescriptors : public RawObject {
  public:
 // The macro argument V is passed two arguments, the raw name of the enum value
@@ -2993,9 +2975,8 @@ inline bool RawObject::IsVariableSizeClassId(intptr_t index) {
          RawObject::IsTwoByteStringClassId(index) ||
          RawObject::IsTypedDataClassId(index) || (index == kContextCid) ||
          (index == kTypeArgumentsCid) || (index == kInstructionsCid) ||
-         (index == kInstructionsSectionCid) || (index == kObjectPoolCid) ||
+         (index == kObjectPoolCid) || (index == kPcDescriptorsCid) ||
-         (index == kPcDescriptorsCid) || (index == kCodeSourceMapCid) ||
+         (index == kCodeSourceMapCid) || (index == kCompressedStackMapsCid) ||
-         (index == kCompressedStackMapsCid) ||
          (index == kLocalVarDescriptorsCid) ||
          (index == kExceptionHandlersCid) || (index == kCodeCid) ||
          (index == kContextScopeCid) || (index == kInstanceCid) ||

runtime/vm/raw_object_snapshot.cc

@@ -541,7 +541,6 @@ MESSAGE_SNAPSHOT_UNREACHABLE(Field);
 MESSAGE_SNAPSHOT_UNREACHABLE(Function);
 MESSAGE_SNAPSHOT_UNREACHABLE(ICData);
 MESSAGE_SNAPSHOT_UNREACHABLE(Instructions);
-MESSAGE_SNAPSHOT_UNREACHABLE(InstructionsSection);
 MESSAGE_SNAPSHOT_UNREACHABLE(KernelProgramInfo);
 MESSAGE_SNAPSHOT_UNREACHABLE(Library);
 MESSAGE_SNAPSHOT_UNREACHABLE(LibraryPrefix);

runtime/vm/reverse_pc_lookup_cache.cc

@@ -11,11 +11,13 @@ namespace dart {
 #if defined(DART_PRECOMPILED_RUNTIME)
 
 static uword BeginPcFromCode(const RawCode* code) {
-  return Code::PayloadStartOf(code);
+  auto instr = Code::InstructionsOf(code);
+  return Instructions::PayloadStart(instr);
 }
 
 static uword EndPcFromCode(const RawCode* code) {
-  return Code::PayloadStartOf(code) + Code::PayloadSizeOf(code);
+  auto instr = Code::InstructionsOf(code);
+  return Instructions::PayloadStart(instr) + Instructions::Size(instr);
 }
 
 void ReversePcLookupCache::BuildAndAttachToIsolate(Isolate* isolate) {

runtime/vm/reverse_pc_lookup_cache.h

@@ -66,11 +66,7 @@ class ReversePcLookupCache {
   }
 
   // Looks up the [Code] object from a given [pc].
-  //
+  inline RawCode* Lookup(uword pc) {
-  // If [is_return_address] is true, then the PC may be immediately after the
-  // payload, if the last instruction is a call that is guaranteed not to
-  // return. Otherwise, the PC must be within the payload.
-  inline RawCode* Lookup(uword pc, bool is_return_address = false) {
     NoSafepointScope no_safepoint_scope;
 
     intptr_t left = 0;
@@ -85,14 +81,6 @@ class ReversePcLookupCache {
       uword middle_pc = pc_array_[middle];
       if (middle_pc < pc_offset) {
         left = middle + 1;
-      } else if (!is_return_address && middle_pc == pc_offset) {
-        // This case should only happen if we have bare instruction payloads.
-        // Otherwise, the instruction payloads of two RawInstructions objects
-        // will never be immediately adjacent in memory due to the header of
-        // the second object.
-        ASSERT(FLAG_use_bare_instructions);
-        left = middle + 1;
-        break;
       } else {
         right = middle;
       }
@@ -128,9 +116,7 @@ class ReversePcLookupCache {
 
   inline bool Contains(uword pc) { return false; }
 
-  inline RawCode* Lookup(uword pc, bool is_return_address = false) {
+  inline RawCode* Lookup(uword pc) { UNREACHABLE(); }
-    UNREACHABLE();
-  }
 };
 
 #endif  // defined(DART_PRECOMPILED_RUNTIME

runtime/vm/stack_frame.cc

@@ -126,7 +126,7 @@ bool StackFrame::IsBareInstructionsDartFrame() const {
   if (auto isolate = IsolateOfBareInstructionsFrame()) {
     Code code;
     auto rct = isolate->reverse_pc_lookup_cache();
-    code = rct->Lookup(pc(), /*is_return_address=*/true);
+    code = rct->Lookup(pc());
 
     const intptr_t cid = code.owner()->GetClassId();
     ASSERT(cid == kNullCid || cid == kClassCid || cid == kFunctionCid);
@@ -141,7 +141,7 @@ bool StackFrame::IsBareInstructionsStubFrame() const {
   if (auto isolate = IsolateOfBareInstructionsFrame()) {
     Code code;
     auto rct = isolate->reverse_pc_lookup_cache();
-    code = rct->Lookup(pc(), /*is_return_address=*/true);
+    code = rct->Lookup(pc());
 
     const intptr_t cid = code.owner()->GetClassId();
     ASSERT(cid == kNullCid || cid == kClassCid || cid == kFunctionCid);
@@ -253,8 +253,7 @@ void StackFrame::VisitObjectPointers(ObjectPointerVisitor* visitor) {
   Code code;
 
   if (auto isolate = IsolateOfBareInstructionsFrame()) {
-    auto const rct = isolate->reverse_pc_lookup_cache();
+    code = isolate->reverse_pc_lookup_cache()->Lookup(pc());
-    code = rct->Lookup(pc(), /*is_return_address=*/true);
   } else {
     RawObject* pc_marker = *(reinterpret_cast<RawObject**>(
         fp() + ((is_interpreted() ? kKBCPcMarkerSlotFromFp
@@ -388,8 +387,7 @@ RawCode* StackFrame::LookupDartCode() const {
   NoSafepointScope no_safepoint;
 #endif
   if (auto isolate = IsolateOfBareInstructionsFrame()) {
-    auto const rct = isolate->reverse_pc_lookup_cache();
+    return isolate->reverse_pc_lookup_cache()->Lookup(pc());
-    return rct->Lookup(pc(), /*is_return_address=*/true);
   }
 
   RawCode* code = GetCodeObject();
@@ -403,8 +401,7 @@ RawCode* StackFrame::LookupDartCode() const {
 RawCode* StackFrame::GetCodeObject() const {
   ASSERT(!is_interpreted());
   if (auto isolate = IsolateOfBareInstructionsFrame()) {
-    auto const rct = isolate->reverse_pc_lookup_cache();
+    return isolate->reverse_pc_lookup_cache()->Lookup(pc());
-    return rct->Lookup(pc(), /*is_return_address=*/true);
   } else {
     RawObject* pc_marker = *(reinterpret_cast<RawObject**>(
         fp() + runtime_frame_layout.code_from_fp * kWordSize));

runtime/vm/symbols.h

@@ -178,7 +178,6 @@ class ObjectPointerVisitor;
   V(IndexToken, "[]")                                                          \
   V(InitPrefix, "init:")                                                       \
   V(Instructions, "Instructions")                                              \
-  V(InstructionsSection, "InstructionsSection")                                \
   V(Int, "int")                                                                \
   V(Int16List, "Int16List")                                                    \
   V(Int32List, "Int32List")                                                    \