Object allocation

TEST=tools/test.py -n vm-modaot-mac-debug-arm64 language
Issue: https://github.com/dart-lang/sdk/issues/61635
Change-Id: Ie569c19ef37e27f7f711dfc3d62db818691f28fd
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/476600
Commit-Queue: Alexander Markov <alexmarkov@google.com>
Reviewed-by: Slava Egorov <vegorov@google.com>

pkg/cfg/lib/ir/field.dart

@@ -12,4 +12,5 @@ extension type CField(ast.Field _raw) {
   bool get isFinal => _raw.isFinal;
   bool get hasInitializer => _raw.initializer != null;
   CType get type => CType.fromStaticType(_raw.type);
+  ast.Class get enclosingClass => _raw.enclosingClass!;
 }

pkg/cfg/lib/ir/instructions.dart

@@ -1644,7 +1644,9 @@ abstract base class MoveOp {}
 enum ParallelMoveStage {
   // Move fixed output of the instruction to its desired location.
   output,
-  // Split/spill live ranges.
+  // Spill output of the instruction.
+  spill,
+  // Split live ranges.
   split,
   // Moves at control flow edges (including phi moves).
   control,

pkg/cfg/lib/ir/ir_to_text.dart

@@ -181,6 +181,7 @@ final class IrToText extends VoidInstructionVisitor {
         DynamicCallKind.getter => 'get ',
         DynamicCallKind.setter => 'set ',
       }}${instr.selector}',
+    AllocateObject() => 'AllocateObject ${instr.type}',
     BinaryIntOp() => 'BinaryIntOp ${instr.op.token}',
     UnaryIntOp() => 'UnaryIntOp ${instr.op.token}',
     BinaryDoubleOp() => 'BinaryDoubleOp ${instr.op.token}',

pkg/cfg/testcases/calls.dart.expect

@@ -209,7 +209,7 @@ B0 = EntryBlock()
 B0 = EntryBlock()
   v13 = Constant(null)
   v1 = Parameter(a)
-  v2 = AllocateObject()
+  v2 = AllocateObject B()
   DirectCall B.(v2, v1)
   v8 = InterfaceCall getter C.y(v2)
   v10 = InterfaceCall getter C.x(v2)

pkg/cfg/testcases/types.dart.expect

@@ -53,7 +53,7 @@ B0 = EntryBlock()
 B0 = EntryBlock()
   v1 = TypeParameters()
   v2 = TypeArguments(v1, <A..T%>)
-  v3 = AllocateObject(v2)
+  v3 = AllocateObject A<A..T%>(v2)
   DirectCall A._(v3)
   Return(v3)
 

pkg/native_compiler/lib/back_end/arm64/assembler.dart

@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:native_compiler/back_end/assembler.dart';
+import 'package:native_compiler/back_end/code.dart';
 import 'package:native_compiler/back_end/locations.dart';
 import 'package:native_compiler/runtime/vm_defs.dart';
 import 'package:cfg/ir/constant_value.dart';
@@ -328,6 +329,49 @@ final class Arm64Assembler extends Assembler with Uint32OutputBuffer {
     }
   }
 
+  /// Create a [base + offset] address for arbitrary offset,
+  /// generating extra code if necessary.
+  /// The resulting address can be used in ldp/stp instructions.
+  Address pairAddress(
+    Register base,
+    int offset, [
+    OperandSize sz = OperandSize.s64,
+  ]) {
+    final scale = sz.log2sizeInBytes;
+    if (_isInt(7 + scale, offset) && ((offset & (sz.sizeInBytes - 1)) == 0)) {
+      return RegOffsetAddress(base, offset);
+    } else {
+      throw 'Large address offsets are not implemented yet: $offset';
+    }
+  }
+
+  @override
+  void enterDartFrame() {
+    pushPair(FP, LR);
+    mov(FP, stackPointerReg);
+
+    // Tag and save caller pool pointer.
+    add(poolPointerReg, poolPointerReg, Immediate(heapObjectTag));
+    pushPair(poolPointerReg, codeReg);
+
+    // Load and untag current pool pointer.
+    ldr(
+      poolPointerReg,
+      fieldAddress(codeReg, vmOffsets.Code_object_pool_offset),
+    );
+    sub(poolPointerReg, poolPointerReg, Immediate(heapObjectTag));
+  }
+
+  @override
+  void leaveDartFrame() {
+    // Restore and untag pool pointer.
+    ldr(poolPointerReg, RegOffsetAddress(FP, -2 * wordSize));
+    sub(poolPointerReg, poolPointerReg, Immediate(heapObjectTag));
+
+    mov(stackPointerReg, FP);
+    popPair(FP, LR);
+  }
+
   @override
   void push(Register reg) {
     str(
@@ -503,6 +547,56 @@ final class Arm64Assembler extends Assembler with Uint32OutputBuffer {
   bool canEncodeBitMasks(int value, [OperandSize sz = OperandSize.s64]) =>
       Immediate(value).tryEncodingBitMasks(sz) != null;
 
+  @override
+  void addImmediate(
+    Register dst,
+    Register src,
+    int value, [
+    OperandSize sz = OperandSize.s64,
+  ]) {
+    assert(sz.is32or64);
+    assert(_isInt(sz.bitWidth, value) || _isUint(sz.bitWidth, value));
+    if (value == 0) {
+      if (dst != src) {
+        mov(dst, src, sz);
+      }
+    } else if (canEncodeImm12(value)) {
+      add(dst, src, Immediate(value), sz);
+    } else if (canEncodeImm12(-value)) {
+      sub(dst, src, Immediate(-value), sz);
+    } else {
+      assert(src != tempReg);
+      loadImmediate(tempReg, value);
+      if (dst == SP || src == SP) {
+        add(dst, src, ExtRegOperand(tempReg, .UXTX, 0), sz);
+      } else {
+        add(dst, src, tempReg, sz);
+      }
+    }
+  }
+
+  @override
+  void andImmediate(
+    Register dst,
+    Register src,
+    int value, [
+    OperandSize sz = OperandSize.s64,
+  ]) {
+    assert(sz.is32or64);
+    assert(_isInt(sz.bitWidth, value) || _isUint(sz.bitWidth, value));
+    if (value == 0) {
+      movz(dst, 0);
+    } else if (value == -1) {
+      mov(dst, src, sz);
+    } else if (canEncodeBitMasks(value, sz)) {
+      and(dst, src, Immediate(value), sz);
+    } else {
+      assert(src != tempReg);
+      loadImmediate(tempReg, value);
+      and(dst, src, tempReg, sz);
+    }
+  }
+
   @override
   void callRuntime(RuntimeEntry entry, int argumentCount) {
     ldr(
@@ -520,6 +614,18 @@ final class Arm64Assembler extends Assembler with Uint32OutputBuffer {
     blr(LR);
   }
 
+  @override
+  void callLeafRuntime(LeafRuntimeEntry entry) {
+    unimplemented("callLeafRuntime $entry");
+  }
+
+  @override
+  void callStub(Code stub) {
+    loadFromPool(codeReg, stub);
+    ldr(LR, fieldAddress(codeReg, vmOffsets.Code_entry_point_offset.first));
+    blr(LR);
+  }
+
   @override
   void unimplemented(String message) {
     loadConstant(R0, ConstantValue.fromString(message));

pkg/native_compiler/lib/back_end/arm64/code_generator.dart

@@ -5,10 +5,14 @@
 import 'package:cfg/ir/constant_value.dart';
 import 'package:cfg/ir/instructions.dart';
 import 'package:cfg/utils/misc.dart';
+import 'package:kernel/ast.dart' as ast;
 import 'package:native_compiler/back_end/arm64/assembler.dart';
+import 'package:native_compiler/back_end/arm64/stub_code_generator.dart';
 import 'package:native_compiler/back_end/assembler.dart';
 import 'package:native_compiler/back_end/code_generator.dart';
 import 'package:native_compiler/back_end/locations.dart';
+import 'package:native_compiler/back_end/object_pool.dart';
+import 'package:native_compiler/runtime/type_utils.dart';
 import 'package:native_compiler/runtime/vm_defs.dart';
 
 final class Arm64CodeGenerator extends CodeGenerator {
@@ -21,19 +25,7 @@ final class Arm64CodeGenerator extends CodeGenerator {
 
   @override
   void enterFrame() {
-    _asm.pushPair(FP, LR);
-    _asm.mov(FP, stackPointerReg);
-
-    // Tag and save caller pool pointer.
-    _asm.add(poolPointerReg, poolPointerReg, Immediate(heapObjectTag));
-    _asm.pushPair(poolPointerReg, codeReg);
-
-    // Load and untag current pool pointer.
-    _asm.ldr(
-      poolPointerReg,
-      _asm.fieldAddress(codeReg, _asm.vmOffsets.Code_object_pool_offset),
-    );
-    _asm.sub(poolPointerReg, poolPointerReg, Immediate(heapObjectTag));
+    _asm.enterDartFrame();
 
     // TODO: calculate stack frame size.
     _asm.sub(stackPointerReg, stackPointerReg, Immediate(64));
@@ -185,12 +177,7 @@ final class Arm64CodeGenerator extends CodeGenerator {
   @override
   void visitReturn(Return instr) {
     assert(inputReg(instr, 0) == returnReg);
-    // Restore and untag pool pointer.
-    _asm.ldr(poolPointerReg, RegOffsetAddress(FP, -2 * wordSize));
-    _asm.sub(poolPointerReg, poolPointerReg, Immediate(heapObjectTag));
-
-    _asm.mov(stackPointerReg, FP);
-    _asm.popPair(FP, LR);
+    _asm.leaveDartFrame();
     _asm.ret();
   }
 
@@ -255,13 +242,13 @@ final class Arm64CodeGenerator extends CodeGenerator {
     // TODO: call directly through Code.
     _asm.ldr(
       codeReg,
-      _asm.fieldAddress(functionReg, _asm.vmOffsets.Function_code_offset),
+      _asm.fieldAddress(functionReg, vmOffsets.Function_code_offset),
     );
     _asm.ldr(
       tempReg,
       _asm.fieldAddress(
         functionReg,
-        _asm.vmOffsets.Function_entry_point_offset.first,
+        vmOffsets.Function_entry_point_offset.first,
       ),
     );
     _asm.blr(tempReg);
@@ -350,7 +337,107 @@ final class Arm64CodeGenerator extends CodeGenerator {
 
   @override
   void visitAllocateObject(AllocateObject instr) {
-    _asm.unimplemented('Unimplemented: code generation for AllocateObject');
+    final cls = (instr.type.dartType as ast.InterfaceType).classNode;
+    final instanceSize = objectLayout.getInstanceSize(cls);
+    final typeArgsField = objectLayout.getTypeArgumentsField(cls);
+    final typeArgumentsReg = AllocationStub.typeArgumentsReg;
+    final tagsReg = AllocationStub.tagsReg;
+    final resultReg = AllocationStub.resultReg;
+    assert(!instr.hasTypeArguments || inputReg(instr, 0) == typeArgumentsReg);
+    assert(outputReg(instr) == resultReg);
+
+    // TODO: support huge objects
+
+    final done = Label();
+    Label slowPath = addSlowPath(() {
+      _asm.callStub(backEndState.stubFactory.getAllocationStub(cls));
+      _asm.b(done);
+    });
+
+    final endReg = AllocationStub.scratch1Reg;
+    final newTopReg = AllocationStub.scratch2Reg;
+    // Load Thread.top_ and Thread.end_.
+    _asm.ldp(
+      resultReg,
+      endReg,
+      _asm.pairAddress(threadReg, vmOffsets.Thread_top_offset),
+    );
+    _asm.addImmediate(newTopReg, resultReg, instanceSize);
+    _asm.cmp(endReg, newTopReg);
+    _asm.b(slowPath, Condition.unsignedLessOrEqual);
+
+    // TLAB has enough space. Update top and initialize object.
+    _asm.loadFromPool(tagsReg, NewObjectTags(cls));
+    _asm.str(newTopReg, _asm.address(threadReg, vmOffsets.Thread_top_offset));
+    _asm.str(tagsReg, _asm.address(resultReg, vmOffsets.Object_tags_offset));
+    // TODO: figure out if we need store-store barrier here.
+
+    // TODO: support compressed pointers.
+    const maxUnrolledSize = 16 * wordSize;
+    if (instanceSize <= maxUnrolledSize) {
+      int offset = vmOffsets.Instance_first_field_offset;
+      for (; offset + 2 * wordSize <= instanceSize; offset += 2 * wordSize) {
+        _asm.stp(nullReg, nullReg, _asm.pairAddress(resultReg, offset));
+      }
+      if (offset < instanceSize) {
+        _asm.str(nullReg, _asm.address(resultReg, offset));
+        offset += wordSize;
+      }
+      assert(offset == instanceSize);
+    } else {
+      final fieldReg = AllocationStub.scratch1Reg;
+      _asm.addImmediate(
+        fieldReg,
+        resultReg,
+        vmOffsets.Instance_first_field_offset,
+      );
+
+      final loop = Label();
+      _asm.bind(loop);
+      _asm.stp(
+        nullReg,
+        nullReg,
+        WritebackRegOffsetAddress(fieldReg, 2 * wordSize, isPostIndexed: true),
+      );
+      // There is at least two word (kAllocationRedZoneSize) gap at the end of page
+      // which makes it possible to initialize objects by two words at once and
+      // write slightly beyond the end.
+      _asm.cmp(fieldReg, newTopReg);
+      _asm.b(loop, Condition.unsignedLess);
+    }
+
+    _asm.addImmediate(resultReg, resultReg, heapObjectTag);
+
+    if (typeArgsField != null) {
+      if (instr.hasTypeArguments) {
+        _asm.str(
+          typeArgumentsReg,
+          _asm.fieldAddress(
+            resultReg,
+            objectLayout.getFieldOffset(typeArgsField),
+          ),
+        );
+      } else {
+        final typeArgs = getInstantiatorTypeArguments(cls, []);
+        if (typeArgs != null) {
+          _asm.loadConstant(
+            typeArgumentsReg,
+            ConstantValue(TypeArgumentsConstant(typeArgs)),
+          );
+          _asm.str(
+            typeArgumentsReg,
+            _asm.fieldAddress(
+              resultReg,
+              objectLayout.getFieldOffset(typeArgsField),
+            ),
+          );
+        }
+      }
+    }
+
+    // TODO: allocation profile; allocation probe points.
+
+    _asm.bind(done);
   }
 
   @override
@@ -395,11 +482,32 @@ final class Arm64CodeGenerator extends CodeGenerator {
 
   @override
   void generateMove(Location from, Location to) {
-    if (from is Register && to is Register) {
-      _asm.mov(to, from);
-      return;
+    switch (from) {
+      case Register():
+        switch (to) {
+          case Register():
+            _asm.mov(to, from);
+            return;
+          case StackLocation():
+            _asm.str(from, _asm.address(FP, to.frameOffset));
+            return;
+          default:
+            break;
+        }
+      case StackLocation():
+        switch (to) {
+          case Register():
+            _asm.ldr(to, _asm.address(FP, from.frameOffset));
+            return;
+          default:
+            break;
+        }
+      default:
+        break;
     }
-    _asm.unimplemented('Unimplemented: code generation for generateMove');
+    _asm.unimplemented(
+      'Unimplemented: code generation for generateMove ${from.runtimeType} -> ${to.runtimeType}',
+    );
   }
 
   @override
@@ -445,3 +553,7 @@ extension on ComparisonOpcode {
     ComparisonOpcode.doubleGreaterOrEqual => Condition.greaterOrEqual,
   };
 }
+
+extension on StackLocation {
+  int get frameOffset => -(2 + index) * wordSize;
+}

pkg/native_compiler/lib/back_end/arm64/constraints.dart

@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:native_compiler/back_end/arm64/assembler.dart';
+import 'package:native_compiler/back_end/arm64/stub_code_generator.dart';
 import 'package:native_compiler/back_end/constraints.dart';
 import 'package:native_compiler/back_end/locations.dart';
 import 'package:cfg/ir/instructions.dart';
@@ -190,9 +191,16 @@ final class Arm64Constraints extends Constraints {
 
   @override
   InstructionConstraints? visitAllocateObject(AllocateObject instr) =>
-      InstructionConstraints(anyCpuRegister, [
-        if (instr.inputCount == 1) anyCpuRegister,
-      ]);
+      InstructionConstraints(
+        AllocationStub.resultReg,
+        [if (instr.hasTypeArguments) AllocationStub.typeArgumentsReg],
+        [
+          if (!instr.hasTypeArguments) AllocationStub.typeArgumentsReg,
+          AllocationStub.tagsReg,
+          AllocationStub.scratch1Reg,
+          AllocationStub.scratch2Reg,
+        ],
+      );
 
   @override
   InstructionConstraints? visitAllocateClosure(AllocateClosure instr) =>

pkg/native_compiler/lib/back_end/arm64/stub_code_generator.dart

@@ -0,0 +1,95 @@
+// Copyright (c) 2026 the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:cfg/ir/constant_value.dart';
+import 'package:kernel/ast.dart' as ast show Class;
+import 'package:native_compiler/back_end/arm64/assembler.dart';
+import 'package:native_compiler/back_end/assembler.dart';
+import 'package:native_compiler/back_end/locations.dart';
+import 'package:native_compiler/back_end/stub_code_generator.dart';
+import 'package:native_compiler/runtime/type_utils.dart';
+import 'package:native_compiler/runtime/vm_defs.dart';
+
+abstract base class Arm64StubCodeGenerator implements StubCodeGenerator {
+  final Arm64Assembler _asm;
+
+  Arm64StubCodeGenerator(VMOffsets vmOffsets)
+    : _asm = Arm64Assembler(vmOffsets);
+
+  void _generate();
+
+  void enterStubFrame() {
+    _asm.enterDartFrame();
+  }
+
+  void leaveStubFrame() {
+    _asm.leaveDartFrame();
+  }
+
+  @override
+  Assembler generate() {
+    _generate();
+    return _asm;
+  }
+}
+
+final class AllocationStub extends Arm64StubCodeGenerator {
+  static const Register resultReg = R0;
+  static const Register typeArgumentsReg = R1;
+  static const Register tagsReg = R2;
+
+  static const Register scratch1Reg = R3;
+  static const Register scratch2Reg = R4;
+
+  final ast.Class cls;
+
+  AllocationStub(super.vmOffsets, this.cls);
+
+  @override
+  void _generate() {
+    enterStubFrame();
+
+    if (cls.typeParameters.isEmpty) {
+      final typeArgs = hasInstantiatorTypeArguments(cls)
+          ? getInstantiatorTypeArguments(cls, [])
+          : null;
+      if (typeArgs == null) {
+        _asm.mov(typeArgumentsReg, nullReg);
+      } else {
+        _asm.loadConstant(
+          typeArgumentsReg,
+          ConstantValue(TypeArgumentsConstant(typeArgs)),
+        );
+      }
+    }
+
+    _generateRuntimeCall();
+
+    leaveStubFrame();
+    _asm.ret();
+  }
+
+  void _generateRuntimeCall() {
+    _asm.loadFromPool(scratch1Reg, cls);
+
+    // Space for result.
+    _asm.push(nullReg);
+    // Class and type arguments.
+    _asm.pushPair(typeArgumentsReg, scratch1Reg);
+    _asm.callRuntime(RuntimeEntry.AllocateObject, 2);
+
+    _asm.ldr(resultReg, _asm.address(stackPointerReg, 2 * wordSize));
+
+    // TODO: EnsureIsNewOrRemembered after write barrier elimination is implemented.
+  }
+}
+
+final class Arm64StubFactory extends StubFactory {
+  final VMOffsets vmOffsets;
+  Arm64StubFactory(this.vmOffsets, super.consumeGeneratedCode);
+
+  @override
+  StubCodeGenerator allocationStubGenerator(ast.Class cls) =>
+      AllocationStub(vmOffsets, cls);
+}

pkg/native_compiler/lib/back_end/assembler.dart

@@ -4,6 +4,7 @@
 
 import 'dart:typed_data';
 
+import 'package:native_compiler/back_end/code.dart';
 import 'package:native_compiler/back_end/locations.dart';
 import 'package:native_compiler/back_end/object_pool.dart';
 import 'package:native_compiler/runtime/vm_defs.dart';
@@ -132,6 +133,9 @@ abstract base class Assembler {
   Address fieldAddress(Register obj, int offset) =>
       address(obj, offset - heapObjectTag);
 
+  void enterDartFrame();
+  void leaveDartFrame();
+
   // Push and pop values using Dart stackPointerReg.
   void push(Register reg);
   void pop(Register reg);
@@ -149,7 +153,25 @@ abstract base class Assembler {
   /// Load arbitrary integer [value] into register.
   void loadImmediate(Register reg, int value);
 
+  /// [dst] = [src] + arbitrary integer [value].
+  void addImmediate(
+    Register dst,
+    Register src,
+    int value, [
+    OperandSize sz = OperandSize.s64,
+  ]);
+
+  /// [dst] = bitwise and ([src], arbitrary integer [value]).
+  void andImmediate(
+    Register dst,
+    Register src,
+    int value, [
+    OperandSize sz = OperandSize.s64,
+  ]);
+
   void callRuntime(RuntimeEntry entry, int argumentCount);
+  void callLeafRuntime(LeafRuntimeEntry entry);
+  void callStub(Code stub);
 
   void unimplemented(String message);
 }

pkg/native_compiler/lib/back_end/back_end_state.dart

@@ -3,15 +3,24 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:cfg/ir/instructions.dart';
-import 'package:native_compiler/back_end/code_generator.dart';
+import 'package:native_compiler/back_end/code.dart';
 import 'package:native_compiler/back_end/locations.dart';
+import 'package:native_compiler/back_end/stub_code_generator.dart';
+import 'package:native_compiler/runtime/object_layout.dart';
 import 'package:native_compiler/runtime/vm_defs.dart';
 
 /// Hold back-end state shared between code generation
 /// and register allocation.
 class BackEndState {
+  /// Runtime offsets and constants.
   late final VMOffsets vmOffsets;
 
+  /// Layout of Dart objects.
+  late final ObjectLayout objectLayout;
+
+  /// Reusable stubs.
+  late final StubFactory stubFactory;
+
   /// Block order for the code generation.
   late final List<Block> codeGenBlockOrder;
 

pkg/native_compiler/lib/back_end/code.dart

@@ -0,0 +1,23 @@
+// Copyright (c) 2026, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:typed_data';
+
+import 'package:cfg/ir/functions.dart';
+import 'package:native_compiler/back_end/object_pool.dart';
+
+/// Generated code for a function or a stub.
+class Code {
+  final CFunction? function;
+  final Uint8List instructions;
+  final ObjectPool objectPool;
+
+  /// Offset of instructions in the resulting image.
+  int? instructionsImageOffset;
+
+  Code(this.function, this.instructions, this.objectPool);
+}
+
+/// Comsumer of the generated code.
+typedef CodeConsumer = void Function(Code);

pkg/native_compiler/lib/back_end/code_generator.dart

@@ -5,29 +5,15 @@
 import 'dart:typed_data';
 
 import 'package:cfg/ir/constant_value.dart';
-import 'package:cfg/ir/functions.dart';
 import 'package:cfg/ir/instructions.dart';
 import 'package:cfg/ir/visitor.dart';
 import 'package:cfg/passes/pass.dart';
 import 'package:native_compiler/back_end/assembler.dart';
 import 'package:native_compiler/back_end/back_end_state.dart';
+import 'package:native_compiler/back_end/code.dart';
 import 'package:native_compiler/back_end/locations.dart';
-import 'package:native_compiler/back_end/object_pool.dart';
-
-/// Generated code for a function.
-class Code {
-  final CFunction function;
-  final Uint8List instructions;
-  final ObjectPool objectPool;
-
-  /// Offset of instructions in the resulting image.
-  int? instructionsImageOffset;
-
-  Code(this.function, this.instructions, this.objectPool);
-}
-
-/// Comsumer of the generated code.
-typedef CodeConsumer = void Function(Code);
+import 'package:native_compiler/runtime/object_layout.dart';
+import 'package:native_compiler/runtime/vm_defs.dart';
 
 /// Base class for architecture-specific code generator.
 ///
@@ -53,8 +39,13 @@ abstract base class CodeGenerator extends Pass
     (i) => Label(),
   );
 
+  /// Slow paths generated after all blocks.
+  final List<SlowPath> _slowPaths = [];
+
   CodeGenerator(this.backEndState) : super('CodeGen');
 
+  VMOffsets get vmOffsets => backEndState.vmOffsets;
+  ObjectLayout get objectLayout => backEndState.objectLayout;
   List<Block> get codeGenBlockOrder => backEndState.codeGenBlockOrder;
 
   Location loc(OperandId operandId) =>
@@ -108,6 +99,11 @@ abstract base class CodeGenerator extends Pass
     }
     _currentBlockIndex = -1;
 
+    for (final slowPath in _slowPaths) {
+      _asm.bind(slowPath.entry);
+      slowPath.generator();
+    }
+
     backEndState.consumeGeneratedCode(
       Code(graph.function, _asm.bytes, _asm.objectPool),
     );
@@ -164,6 +160,12 @@ abstract base class CodeGenerator extends Pass
     return firstNonEmpty;
   }
 
+  Label addSlowPath(void Function() generator) {
+    final entry = Label();
+    _slowPaths.add(SlowPath(entry, generator));
+    return entry;
+  }
+
   @override
   void visitEntryBlock(EntryBlock instr) {}
 
@@ -202,24 +204,33 @@ abstract base class CodeGenerator extends Pass
     // TODO: merge subsequent ParallelMove instructions.
     final map = <Location, Location>{};
     for (final move in instr.moves) {
-      if (move is Move && move.from != move.to) {
-        assert(!map.containsKey(move.from));
-        map[move.from] = move.to;
+      if (move is Move) {
+        final from = move.from.physicalLocation;
+        final to = move.to.physicalLocation;
+        if (from != to) {
+          assert(!map.containsKey(from));
+          map[from] = to;
+        }
       }
     }
     for (final move in instr.moves) {
-      if (move is Move && map.containsKey(move.from)) {
-        if (map.containsKey(move.to)) {
-          _generateDependentMoves(move.from, move.to, map);
-        } else {
-          generateMove(move.from, move.to);
-          map.remove(move.from);
+      if (move is Move) {
+        final from = move.from.physicalLocation;
+        final to = move.to.physicalLocation;
+
+        if (map.containsKey(from)) {
+          if (map.containsKey(to)) {
+            _generateDependentMoves(from, to, map);
+          } else {
+            generateMove(from, to);
+            map.remove(from);
+          }
         }
       }
     }
     for (final move in instr.moves) {
       if (move is LoadConstant) {
-        generateLoadConstant(move.value, move.to);
+        generateLoadConstant(move.value, move.to.physicalLocation);
       }
     }
   }
@@ -280,3 +291,9 @@ abstract base class CodeGenerator extends Pass
   void visitStringInterpolation(StringInterpolation instr) =>
       throw 'Unexpected StringInterpolation (should be lowered)';
 }
+
+class SlowPath {
+  final Label entry;
+  final void Function() generator;
+  SlowPath(this.entry, this.generator);
+}

pkg/native_compiler/lib/back_end/object_pool.dart

@@ -2,9 +2,9 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+import 'package:kernel/ast.dart' as ast;
+
 /// Helper class for building object pool accessible from generated code.
-///
-/// TODO: add tags, different kinds of entries.
 class ObjectPool {
   final List<Object> entries = [];
   final Map<Object, int> _objects = {};
@@ -17,3 +17,20 @@ class ObjectPool {
     return index;
   }
 }
+
+/// Base class for specialized object pool entries which are not just
+/// object references.
+sealed class SpecializedEntry {}
+
+/// Object pool entry representing tags for the new objects of the given class.
+final class NewObjectTags extends SpecializedEntry {
+  final ast.Class cls;
+  NewObjectTags(this.cls);
+
+  @override
+  int get hashCode => cls.hashCode + 19;
+
+  @override
+  bool operator ==(Object other) =>
+      other is NewObjectTags && this.cls == other.cls;
+}

pkg/native_compiler/lib/back_end/register_allocator.dart

@@ -42,7 +42,7 @@ final class LinearScanRegisterAllocator extends RegisterAllocator {
   // which can be inserted later between instructions.
   static const int step = 2;
 
-  static const bool trace = false;
+  static const bool trace = const bool.fromEnvironment('trace.regalloc');
 
   static const int maxPosition = 0x7fffffff;
 
@@ -818,7 +818,7 @@ final class LinearScanRegisterAllocator extends RegisterAllocator {
         if (liveRange.allocatedLocation is! StackLocation) {
           _insertMoveBefore(
             _nextInstruction(instr),
-            ParallelMoveStage.split,
+            ParallelMoveStage.spill,
             liveRange.allocatedLocation!,
             spillSlot,
           );

pkg/native_compiler/lib/back_end/stub_code_generator.dart

@@ -0,0 +1,34 @@
+// Copyright (c) 2026, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:kernel/ast.dart' as ast show Class;
+import 'package:native_compiler/back_end/assembler.dart';
+import 'package:native_compiler/back_end/code.dart';
+
+/// Interface class for architecture-specific stub code generator.
+abstract interface class StubCodeGenerator {
+  Assembler generate();
+}
+
+/// Base class for architecture-specific stub factory.
+///
+/// Generates and caches stubs on demand.
+abstract base class StubFactory {
+  final CodeConsumer consumeGeneratedCode;
+  Map<ast.Class, Code> _allocationStubs = {};
+
+  StubFactory(this.consumeGeneratedCode);
+
+  StubCodeGenerator allocationStubGenerator(ast.Class cls);
+
+  Code _generateCode(StubCodeGenerator generator) {
+    final asm = generator.generate();
+    final code = Code(null, asm.bytes, asm.objectPool);
+    consumeGeneratedCode(code);
+    return code;
+  }
+
+  Code getAllocationStub(ast.Class cls) =>
+      _allocationStubs[cls] ??= _generateCode(allocationStubGenerator(cls));
+}

pkg/native_compiler/lib/compilation_set.dart

@@ -7,7 +7,8 @@ import 'package:cfg/front_end/recognized_methods.dart';
 import 'package:cfg/ir/flow_graph.dart';
 import 'package:cfg/ir/functions.dart';
 import 'package:kernel/ast.dart' as ast;
-import 'package:native_compiler/back_end/code_generator.dart';
+import 'package:native_compiler/back_end/code.dart';
+import 'package:native_compiler/back_end/stub_code_generator.dart';
 import 'package:native_compiler/configuration.dart';
 import 'package:native_compiler/snapshot/image_writer.dart';
 import 'package:native_compiler/snapshot/snapshot.dart';
@@ -21,10 +22,12 @@ class CompilationSet {
   final List<CFunction> _pendingFunctions = [];
   final ImageWriter _imageWriter;
   late final SnapshotSerializer _snapshot;
+  late final StubFactory _stubFactory;
 
   CompilationSet(this.libraries, this.config)
     : _imageWriter = config.createImageWriter() {
     _snapshot = SnapshotSerializer(config.targetCPU, functionRegistry);
+    _stubFactory = config.createStubFactory(_consumeGeneratedCode);
   }
 
   /// Add [function] to be compiled.
@@ -111,7 +114,9 @@ class CompilationSet {
       rethrow;
     }
 
-    config.createPipeline(functionRegistry, _consumeGeneratedCode).run(graph);
+    config
+        .createPipeline(functionRegistry, _stubFactory, _consumeGeneratedCode)
+        .run(graph);
   }
 
   void _consumeGeneratedCode(Code code) {

pkg/native_compiler/lib/configuration.dart

@@ -11,13 +11,17 @@ import 'package:cfg/passes/simplification.dart';
 import 'package:cfg/passes/value_numbering.dart';
 import 'package:native_compiler/back_end/arm64/code_generator.dart';
 import 'package:native_compiler/back_end/arm64/constraints.dart';
+import 'package:native_compiler/back_end/arm64/stub_code_generator.dart';
 import 'package:native_compiler/back_end/back_end_state.dart';
+import 'package:native_compiler/back_end/code.dart';
 import 'package:native_compiler/back_end/code_generator.dart';
 import 'package:native_compiler/back_end/constraints.dart';
 import 'package:native_compiler/back_end/regalloc_checker.dart';
 import 'package:native_compiler/back_end/register_allocator.dart';
+import 'package:native_compiler/back_end/stub_code_generator.dart';
 import 'package:native_compiler/passes/lowering.dart';
 import 'package:native_compiler/passes/reorder_blocks.dart';
+import 'package:native_compiler/runtime/object_layout.dart';
 import 'package:native_compiler/runtime/vm_defs.dart';
 import 'package:native_compiler/snapshot/image_writer.dart';
 import 'package:native_compiler/snapshot/macho/macho_image_writer.dart';
@@ -51,8 +55,13 @@ abstract base class Configuration {
     required this.outputLibraryName,
   });
 
+  VMOffsets get vmOffsets;
+
+  ObjectLayout get objectLayout;
+
   Pipeline createPipeline(
     FunctionRegistry functionRegistry,
+    StubFactory stubFactory,
     CodeConsumer consumeGeneratedCode,
   );
 
@@ -65,6 +74,11 @@ abstract base class Configuration {
         TargetCPU.arm64 => Arm64CodeGenerator(backEndState),
       };
 
+  StubFactory createStubFactory(CodeConsumer consumeGeneratedCode) =>
+      switch (targetCPU) {
+        TargetCPU.arm64 => Arm64StubFactory(vmOffsets, consumeGeneratedCode),
+      };
+
   ImageWriter createImageWriter() => switch (imageFormat) {
     ImageFormat.macho => MachoImageWriter(targetCPU, outputLibraryName),
   };
@@ -78,17 +92,30 @@ final class DevelopmentCompilerConfiguration extends Configuration {
     required super.outputLibraryName,
   });
 
-  VMOffsets createVMOffsets() => switch (targetCPU) {
+  @override
+  late final VMOffsets vmOffsets = switch (targetCPU) {
     TargetCPU.arm64 => Arm64VMOffsets(),
   };
 
+  @override
+  late final ObjectLayout objectLayout = switch (targetCPU) {
+    TargetCPU.arm64 => ObjectLayout(
+      vmOffsets,
+      wordSize: 8,
+      compressedWordSize: 8,
+    ),
+  };
+
   @override
   Pipeline createPipeline(
     FunctionRegistry functionRegistry,
+    StubFactory stubFactory,
     CodeConsumer consumeGeneratedCode,
   ) {
     final backEndState = BackEndState();
-    backEndState.vmOffsets = createVMOffsets();
+    backEndState.vmOffsets = vmOffsets;
+    backEndState.objectLayout = objectLayout;
+    backEndState.stubFactory = stubFactory;
     backEndState.consumeGeneratedCode = consumeGeneratedCode;
     final constraints = createConstraints();
     return Pipeline([

pkg/native_compiler/lib/runtime/object_layout.dart

@@ -0,0 +1,159 @@
+// Copyright (c) 2026, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:cfg/ir/field.dart';
+import 'package:cfg/ir/global_context.dart';
+import 'package:cfg/utils/misc.dart';
+import 'package:kernel/ast.dart' as ast;
+import 'package:native_compiler/runtime/vm_defs.dart';
+
+/// Computes layout of Dart objects (field offsets and instance size).
+class ObjectLayout {
+  final VMOffsets vmOffsets;
+  final int wordSize;
+  final int compressedWordSize;
+
+  /// Instance size before rounding.
+  final Map<ast.Class, int> _instanceSize = {};
+
+  /// Name of the implicit type arguments field.
+  late final ast.Name _typeArgumentsFieldName = ast.Name('#typeArguments');
+
+  /// Implicit type arguments field for a class.
+  final Map<ast.Class, CField> _typeArgumentsField = {};
+
+  /// Field offsets.
+  final Map<CField, int> _fieldOffset = {};
+
+  ObjectLayout(
+    this.vmOffsets, {
+    required this.wordSize,
+    required this.compressedWordSize,
+  });
+
+  int getInstanceSize(ast.Class cls) {
+    _ensureComputed(cls);
+    return roundUp(_instanceSize[cls]!, objectAlignment(wordSize));
+  }
+
+  int getFieldOffset(CField field) {
+    assert(!field.isStatic);
+    _ensureComputed(field.enclosingClass);
+    return _fieldOffset[field]!;
+  }
+
+  bool isUnboxedField(CField field) {
+    // TODO: support unboxed fields.
+    return false;
+  }
+
+  CField? getTypeArgumentsField(ast.Class cls) {
+    _ensureComputed(cls);
+    return _typeArgumentsField[cls];
+  }
+
+  bool _isComputed(ast.Class cls) => _instanceSize.containsKey(cls);
+
+  void _ensureComputed(ast.Class cls) {
+    if (!_isComputed(cls)) {
+      _computeLayout(cls);
+    }
+  }
+
+  void _computeLayout(ast.Class cls) {
+    if (_computeLayoutOfBuiltInClass(cls)) {
+      return;
+    }
+
+    final superclass = cls.superclass;
+    if (superclass != null) {
+      _ensureComputed(superclass);
+    }
+
+    int nextOffset = _instanceSize[superclass]!;
+
+    final superTypeArgs = superclass != null
+        ? _typeArgumentsField[superclass]
+        : null;
+    if (superTypeArgs != null) {
+      // Inherit type arguments field from generic superclass.
+      _typeArgumentsField[cls] = superTypeArgs;
+    } else if (cls.typeParameters.isNotEmpty) {
+      // This class is generic but superclass is not, so
+      // introduce a new implicit type arguments field.
+      final typeArgs = CField(
+        ast.Field.immutable(
+          _typeArgumentsFieldName,
+          isFinal: true,
+          isStatic: false,
+          fileUri: ast.dummyUri,
+        )..parent = cls,
+      );
+      _typeArgumentsField[cls] = typeArgs;
+      _fieldOffset[typeArgs] = nextOffset;
+      nextOffset += compressedWordSize;
+    }
+
+    for (final field in cls.fields) {
+      if (!field.isStatic) {
+        _fieldOffset[CField(field)] = nextOffset;
+        nextOffset += compressedWordSize;
+      }
+    }
+
+    _instanceSize[cls] = nextOffset;
+  }
+
+  late final Map<String, int> _dartCoreInstanceSize = {
+    '_Double': vmOffsets.Double_InstanceSize,
+    '_GrowableList': vmOffsets.GrowableObjectArray_InstanceSize,
+    '_Mint': vmOffsets.Mint_InstanceSize,
+    '_WeakProperty': vmOffsets.WeakProperty_InstanceSize,
+    '_WeakReference': vmOffsets.WeakReference_InstanceSize,
+    'Object': vmOffsets.Instance_InstanceSize,
+  };
+
+  late final Map<String, int> _dartTypedDataInstanceSize = {
+    '_Int32x4': vmOffsets.Int32x4_InstanceSize,
+    '_Float32x4': vmOffsets.Float32x4_InstanceSize,
+    '_Float64x2': vmOffsets.Float64x2_InstanceSize,
+    // TODO: add other built-in classes from dart:typed_data
+  };
+
+  late final Map<String, int> _dartCompactHashInstanceSize = {
+    '_HashVMBase': vmOffsets.LinkedHashBase_InstanceSize,
+  };
+
+  late final ast.Library _typedDataLibrary = GlobalContext
+      .instance
+      .coreTypes
+      .index
+      .getLibrary('dart:typed_data');
+  late final ast.Library _compactHashLibrary = GlobalContext
+      .instance
+      .coreTypes
+      .index
+      .getLibrary('dart:_compact_hash');
+
+  bool _computeLayoutOfBuiltInClass(ast.Class cls) {
+    final library = cls.enclosingLibrary;
+    if (!library.importUri.isScheme('dart')) {
+      return false;
+    }
+    int? size;
+    if (library == GlobalContext.instance.coreTypes.coreLibrary) {
+      size = _dartCoreInstanceSize[cls.name];
+    } else if (library == _typedDataLibrary) {
+      size = _dartTypedDataInstanceSize[cls.name];
+    } else if (library == _compactHashLibrary) {
+      size = _dartCompactHashInstanceSize[cls.name];
+    }
+    // TODO: add built-in classes from dart:ffi
+    if (size != null) {
+      _instanceSize[cls] = size;
+      return true;
+    }
+    return false;
+  }
+}

pkg/native_compiler/lib/runtime/vm_offsets.g.dart

@@ -107,6 +107,7 @@ base class VMOffsets {
   int get ICData_entries_offset => throw 'Unknown';
   int get ICData_owner_offset => throw 'Unknown';
   int get ICData_state_bits_offset => throw 'Unknown';
+  int get Instance_first_field_offset => throw 'Unknown';
   int get Int32x4_value_offset => throw 'Unknown';
   int get Isolate_finalizers_offset => throw 'Unknown';
   int get Isolate_has_resumption_breakpoints_offset => throw 'Unknown';
@@ -130,6 +131,7 @@ base class VMOffsets {
   int get NativeArguments_argv_offset => throw 'Unknown';
   int get NativeArguments_retval_offset => throw 'Unknown';
   int get NativeArguments_thread_offset => throw 'Unknown';
+  int get Object_tags_offset => throw 'Unknown';
   int get ObjectStore_double_type_offset => throw 'Unknown';
   int get ObjectStore_int_type_offset => throw 'Unknown';
   int get ObjectStore_record_field_names_offset => throw 'Unknown';
@@ -752,6 +754,8 @@ final class Arm64VMOffsets extends VMOffsets {
   @override
   int get ICData_state_bits_offset => 0x34;
   @override
+  int get Instance_first_field_offset => 0x8;
+  @override
   int get Int32x4_value_offset => 0x8;
   @override
   int get Isolate_finalizers_offset => 0x18;
@@ -798,6 +802,8 @@ final class Arm64VMOffsets extends VMOffsets {
   @override
   int get NativeArguments_thread_offset => 0x0;
   @override
+  int get Object_tags_offset => 0x0;
+  @override
   int get ObjectStore_double_type_offset => 0x1b0;
   @override
   int get ObjectStore_int_type_offset => 0x160;
@@ -1661,6 +1667,8 @@ final class Arm64ProductVMOffsets extends VMOffsets {
   @override
   int get ICData_state_bits_offset => 0x34;
   @override
+  int get Instance_first_field_offset => 0x8;
+  @override
   int get Int32x4_value_offset => 0x8;
   @override
   int get Isolate_finalizers_offset => 0x18;
@@ -1705,6 +1713,8 @@ final class Arm64ProductVMOffsets extends VMOffsets {
   @override
   int get NativeArguments_thread_offset => 0x0;
   @override
+  int get Object_tags_offset => 0x0;
+  @override
   int get ObjectStore_double_type_offset => 0x1b0;
   @override
   int get ObjectStore_int_type_offset => 0x160;

pkg/native_compiler/lib/snapshot/snapshot.dart

@@ -8,7 +8,7 @@ import 'dart:typed_data';
 import 'package:cfg/ir/constant_value.dart';
 import 'package:cfg/ir/global_context.dart';
 import 'package:kernel/ast.dart' as ast;
-import 'package:native_compiler/back_end/code_generator.dart' show Code;
+import 'package:native_compiler/back_end/code.dart';
 import 'package:native_compiler/back_end/object_pool.dart';
 import 'package:native_compiler/configuration.dart';
 import 'package:cfg/ir/functions.dart';
@@ -81,6 +81,12 @@ enum FunctionKind {
   fieldInitializer,
 }
 
+/// Object pool entry kinds in the module snapshots.
+///
+/// This enum should match ModuleSnapshot::ObjectPoolEntryKind
+/// enum declared in runtime/vm/module_snapshot.cc.
+enum ObjectPoolEntryKind { objectRef, newObjectTags }
+
 abstract base class SerializationCluster {
   /// Add [object] to the cluster and push its outgoing references.
   void trace(SnapshotSerializer serializer, Object object);
@@ -717,7 +723,14 @@ final class ObjectPoolSerializationCluster extends SerializationCluster {
     final pool = object as ObjectPool;
     _objects.add(pool);
     for (final entry in pool.entries) {
-      serializer.push(entry);
+      if (entry is SpecializedEntry) {
+        switch (entry) {
+          case NewObjectTags():
+            serializer.push(entry.cls);
+        }
+      } else {
+        serializer.push(entry);
+      }
     }
   }
 
@@ -740,7 +753,16 @@ final class ObjectPoolSerializationCluster extends SerializationCluster {
     for (final pool in _objects) {
       serializer.writeUint(pool.entries.length);
       for (final entry in pool.entries) {
-        serializer.writeRefId(entry);
+        if (entry is SpecializedEntry) {
+          switch (entry) {
+            case NewObjectTags():
+              serializer.writeUint(ObjectPoolEntryKind.newObjectTags.index);
+              serializer.writeRefId(entry.cls);
+          }
+        } else {
+          serializer.writeUint(ObjectPoolEntryKind.objectRef.index);
+          serializer.writeRefId(entry);
+        }
       }
     }
   }

pkg/native_compiler/test/back_end/arm64/assembler_test.dart

@@ -7,6 +7,8 @@ import 'dart:typed_data';
 import 'package:cfg/ir/constant_value.dart';
 import 'package:native_compiler/back_end/arm64/assembler.dart';
 import 'package:native_compiler/back_end/assembler.dart';
+import 'package:native_compiler/back_end/code.dart';
+import 'package:native_compiler/back_end/object_pool.dart';
 import 'package:native_compiler/runtime/vm_defs.dart';
 import 'package:test/test.dart';
 import 'disassembler.dart' show Disassembler;
@@ -69,6 +71,47 @@ void main() {
         'str r1, [r0, #32760]\n',
       );
     });
+    test('pairAddress', () {
+      asm.ldp(R1, R2, asm.pairAddress(R0, -0x200));
+      asm.stp(R1, R2, asm.pairAddress(R0, 0x1f8));
+      // TODO: support large and unaligned offsets
+      expectThrows(() {
+        asm.pairAddress(R0, 3);
+      });
+      expectThrows(() {
+        asm.pairAddress(R0, -1);
+      });
+      expectThrows(() {
+        asm.pairAddress(R0, -0x208);
+      });
+      expectThrows(() {
+        asm.pairAddress(R0, 0x200);
+      });
+      expectDisassembly(
+        'ldp r1, r2, [r0, #-512]\n'
+        'stp r1, r2, [r0, #504]\n',
+      );
+    });
+    test('enterDartFrame', () {
+      asm.enterDartFrame();
+      expectDisassembly(
+        'stp fp, lr, [sp, #-16]!\n'
+        'mov fp, sp\n'
+        'add pp, pp, #0x1\n'
+        'stp pp, code, [sp, #-16]!\n'
+        'ldr pp, [code, #${vmOffsets.Code_object_pool_offset - heapObjectTag}]\n'
+        'sub pp, pp, #0x1\n',
+      );
+    });
+    test('leaveDartFrame', () {
+      asm.leaveDartFrame();
+      expectDisassembly(
+        'ldr pp, [fp, #-16]\n'
+        'sub pp, pp, #0x1\n'
+        'mov sp, fp\n'
+        'ldp fp, lr, [sp], #16 !\n',
+      );
+    });
     test('push', () {
       asm.push(R0);
       asm.push(ZR);
@@ -196,6 +239,55 @@ void main() {
         'mov r5, 0xff00ff00ff00ff00\n',
       );
     });
+    test('addImmediate', () {
+      asm.addImmediate(R0, R0, 0);
+      asm.addImmediate(R1, R2, 0);
+      asm.addImmediate(R1, R2, 0, .s32);
+      asm.addImmediate(R1, R2, 0xabc);
+      asm.addImmediate(R1, R2, -0xabc);
+      asm.addImmediate(R1, R2, 0xabc000);
+      asm.addImmediate(R1, R2, -0xabc000);
+      asm.addImmediate(R1, R2, 0x11223344_55667788);
+      asm.addImmediate(SP, FP, 0x11223344_55667788);
+      expectDisassembly(
+        'mov r1, r2\n'
+        'movw r1, r2\n'
+        'add r1, r2, #0xabc\n'
+        'sub r1, r2, #0xabc\n'
+        'add r1, r2, #0xabc000\n'
+        'sub r1, r2, #0xabc000\n'
+        'movz tmp, #0x7788\n'
+        'movk tmp, #0x5566 lsl 16\n'
+        'movk tmp, #0x3344 lsl 32\n'
+        'movk tmp, #0x1122 lsl 48\n'
+        'add r1, r2, tmp\n'
+        'movz tmp, #0x7788\n'
+        'movk tmp, #0x5566 lsl 16\n'
+        'movk tmp, #0x3344 lsl 32\n'
+        'movk tmp, #0x1122 lsl 48\n'
+        'add csp, fp, tmp uxtx 0\n',
+      );
+    });
+    test('andImmediate', () {
+      asm.andImmediate(R1, R2, 0);
+      asm.andImmediate(R1, R2, 0, .u32);
+      asm.andImmediate(R1, R2, -1);
+      asm.andImmediate(R1, R2, -1, .u32);
+      asm.andImmediate(R1, R2, 0xff);
+      asm.andImmediate(R1, R2, 0x11223344_55667788);
+      expectDisassembly(
+        'movz r1, #0x0\n'
+        'movz r1, #0x0\n'
+        'mov r1, r2\n'
+        'movw r1, r2\n'
+        'and r1, r2, 0xff\n'
+        'movz tmp, #0x7788\n'
+        'movk tmp, #0x5566 lsl 16\n'
+        'movk tmp, #0x3344 lsl 32\n'
+        'movk tmp, #0x1122 lsl 48\n'
+        'and r1, r2, tmp\n',
+      );
+    });
     test('callRuntime', () {
       asm.callRuntime(RuntimeEntry.AllocateObject, 2);
       expectDisassembly(
@@ -205,6 +297,15 @@ void main() {
         'blr lr\n',
       );
     });
+    test('callStub', () {
+      final stub = Code(null, Uint8List(0), ObjectPool());
+      asm.callStub(stub);
+      expectDisassembly(
+        'ldr code, [pp, #${objectPoolBase}]\n'
+        'ldr lr, [code, #${vmOffsets.Code_entry_point_offset.first - heapObjectTag}]\n'
+        'blr lr\n',
+      );
+    });
   });
 
   group('instruction', () {

pkg/native_compiler/test/back_end/arm64/disassembler.dart

@@ -1606,14 +1606,14 @@ class ARM64Decoder {
   void decodeAddSubShiftExt(Instr instr) {
     switch (instr.bit(30)) {
       case 0:
-        if (instr.rdField() == R31) {
+        if ((instr.rdField() == R31) && (instr.sField() == 1)) {
           format(instr, "cmn'sf 'rn, 'shift_op");
         } else {
           format(instr, "add'sf's 'rd, 'rn, 'shift_op");
         }
         break;
       case 1:
-        if (instr.rdField() == R31) {
+        if ((instr.rdField() == R31) && (instr.sField() == 1)) {
           format(instr, "cmp'sf 'rn, 'shift_op");
         } else {
           if (instr.rnField() == R31) {

pkg/native_compiler/testcases/lowering_test.dart.expect

@@ -16,7 +16,7 @@ B0 = EntryBlock() dominates:(B9, B11, B8)
   v1 = Parameter(a)   # RA: R0 <- ()
   v2 = Parameter(b)   # RA: R1 <- ()
   v7 = Comparison int & == 0(v1, v2)   # RA: R0 <- (R0, R1)
-  ParallelMove split(R0 -> stack[0])
+  ParallelMove spill(R0 -> stack[0])
   Branch(v7, true: B8, false: B9)   # RA: (R0)
 B8 = TargetBlock() idom:B0
   DirectCall print(v13)   # RA: R0 <- (-) temps: [R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R19, R20, R23, R25, V0, V1, V2, V3, V4, V5, V6, V7, V8, V9, V10, V11, V12, V13, V14, V15, V16, V17, V18, V19, V20, V21, V22, V23, V24, V25, V26, V27, V28, V29, V30]
@@ -42,7 +42,7 @@ B0 = EntryBlock() dominates:(B11, B13, B10)
   v1 = Parameter(a)   # RA: R0 <- ()
   v2 = Parameter(b)   # RA: R1 <- ()
   v7 = Comparison int & == 0(v1, v2)   # RA: R0 <- (R0, R1)
-  ParallelMove split(R0 -> stack[0])
+  ParallelMove spill(R0 -> stack[0])
   Branch(v7, true: B10, false: B11)   # RA: (R0)
 B10 = TargetBlock() idom:B0
   DirectCall print(v15)   # RA: R0 <- (-) temps: [R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R19, R20, R23, R25, V0, V1, V2, V3, V4, V5, V6, V7, V8, V9, V10, V11, V12, V13, V14, V15, V16, V17, V18, V19, V20, V21, V22, V23, V24, V25, V26, V27, V28, V29, V30]
@@ -63,7 +63,7 @@ B0 = EntryBlock() dominates:(B8, B14, B16, B7)
   v2 = Parameter(b)   # RA: R1 <- ()
   v3 = Parameter(c)   # RA: R2 <- ()
   v6 = Comparison int >(v1, v2)   # RA: R0 <- (R0, R1)
-  ParallelMove split(R0 -> stack[0])
+  ParallelMove spill(R0 -> stack[0])
   Branch(v6, true: B7, false: B8)   # RA: (R0)
 B7 = TargetBlock() idom:B0
   Goto(B16)
@@ -149,15 +149,15 @@ B0 = EntryBlock()
   v21 = Constant(9)
   v36 = Constant(null)
   v1 = Parameter(x)   # RA: R0 <- ()
-  ParallelMove split(R0 -> stack[0])
+  ParallelMove spill(R0 -> stack[0])
   v2 = TypeParameters()   # RA: R1 <- ()
-  ParallelMove split(R1 -> stack[1])
+  ParallelMove spill(R1 -> stack[1])
   v5 = DirectCall _GrowableList.(v3, v4)   # RA: R0 <- (-, -) temps: [R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R19, R20, R23, R25, V0, V1, V2, V3, V4, V5, V6, V7, V8, V9, V10, V11, V12, V13, V14, V15, V16, V17, V18, V19, V20, V21, V22, V23, V24, V25, V26, V27, V28, V29, V30]
   ParallelMove output(R0 -> vloc:R0)
   DirectCall print(v5)   # RA: R0 <- (R0) temps: [R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R19, R20, R23, R25, V0, V1, V2, V3, V4, V5, V6, V7, V8, V9, V10, V11, V12, V13, V14, V15, V16, V17, V18, V19, V20, V21, V22, V23, V24, V25, V26, V27, V28, V29, V30]
   ParallelMove split(stack[1] -> R1)
   v7 = TypeArguments(v2, <listLiterals.T%>)   # RA: R0 <- (R1)
-  ParallelMove split(R0 -> stack[2])
+  ParallelMove spill(R0 -> stack[2])
   v8 = DirectCall _GrowableList.(v7, v4)   # RA: R0 <- (R0, -) temps: [R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R19, R20, R23, R25, V0, V1, V2, V3, V4, V5, V6, V7, V8, V9, V10, V11, V12, V13, V14, V15, V16, V17, V18, V19, V20, V21, V22, V23, V24, V25, V26, V27, V28, V29, V30]
   ParallelMove output(R0 -> vloc:R0)
   DirectCall print(v8)   # RA: R0 <- (R0) temps: [R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R19, R20, R23, R25, V0, V1, V2, V3, V4, V5, V6, V7, V8, V9, V10, V11, V12, V13, V14, V15, V16, V17, V18, V19, V20, V21, V22, V23, V24, V25, V26, V27, V28, V29, V30]
@@ -231,21 +231,21 @@ B0 = EntryBlock()
   v38 = Constant(2)
   v40 = Constant(3)
   v1 = Parameter(key)   # RA: R0 <- ()
-  ParallelMove split(R0 -> stack[0])
+  ParallelMove spill(R0 -> stack[0])
   v2 = Parameter(value)   # RA: R1 <- ()
-  ParallelMove split(R1 -> stack[1])
+  ParallelMove spill(R1 -> stack[1])
   v3 = Parameter(key2)   # RA: R2 <- ()
-  ParallelMove split(R2 -> stack[2])
+  ParallelMove spill(R2 -> stack[2])
   v4 = Parameter(value2)   # RA: R3 <- ()
-  ParallelMove split(R3 -> stack[3])
+  ParallelMove spill(R3 -> stack[3])
   v5 = TypeParameters()   # RA: R4 <- ()
-  ParallelMove split(R4 -> stack[4])
+  ParallelMove spill(R4 -> stack[4])
   v30 = DirectCall Map._fromLiteral(v6, v29)   # RA: R0 <- (-, -) temps: [R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R19, R20, R23, R25, V0, V1, V2, V3, V4, V5, V6, V7, V8, V9, V10, V11, V12, V13, V14, V15, V16, V17, V18, V19, V20, V21, V22, V23, V24, V25, V26, V27, V28, V29, V30]
   ParallelMove output(R0 -> vloc:R0)
   DirectCall print(v30)   # RA: R0 <- (R0) temps: [R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R19, R20, R23, R25, V0, V1, V2, V3, V4, V5, V6, V7, V8, V9, V10, V11, V12, V13, V14, V15, V16, V17, V18, V19, V20, V21, V22, V23, V24, V25, V26, V27, V28, V29, V30]
   ParallelMove split(stack[4] -> R1)
   v9 = TypeArguments(v5, <mapLiterals.S%, mapLiterals.T%>)   # RA: R0 <- (R1)
-  ParallelMove split(R0 -> stack[5])
+  ParallelMove spill(R0 -> stack[5])
   v31 = DirectCall Map._fromLiteral(v9, v29)   # RA: R0 <- (R0, -) temps: [R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R19, R20, R23, R25, V0, V1, V2, V3, V4, V5, V6, V7, V8, V9, V10, V11, V12, V13, V14, V15, V16, V17, V18, V19, V20, V21, V22, V23, V24, V25, V26, V27, V28, V29, V30]
   ParallelMove output(R0 -> vloc:R0)
   DirectCall print(v31)   # RA: R0 <- (R0) temps: [R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R19, R20, R23, R25, V0, V1, V2, V3, V4, V5, V6, V7, V8, V9, V10, V11, V12, V13, V14, V15, V16, V17, V18, V19, V20, V21, V22, V23, V24, V25, V26, V27, V28, V29, V30]
@@ -299,11 +299,11 @@ B0 = EntryBlock()
   v28 = Constant(4)
   v30 = Constant(5)
   v1 = Parameter(x)   # RA: R0 <- ()
-  ParallelMove split(R0 -> stack[0])
+  ParallelMove spill(R0 -> stack[0])
   v2 = Parameter(s)   # RA: R1 <- ()
-  ParallelMove split(R1 -> stack[1])
+  ParallelMove spill(R1 -> stack[1])
   v3 = Parameter(o)   # RA: R2 <- ()
-  ParallelMove split(R2 -> stack[2])
+  ParallelMove spill(R2 -> stack[2])
   v17 = DirectCall _StringBase._interpolateSingle(v3)   # RA: R0 <- (R2) temps: [R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R19, R20, R23, R25, V0, V1, V2, V3, V4, V5, V6, V7, V8, V9, V10, V11, V12, V13, V14, V15, V16, V17, V18, V19, V20, V21, V22, V23, V24, V25, V26, V27, V28, V29, V30]
   ParallelMove output(R0 -> vloc:R0)
   DirectCall print(v17)   # RA: R0 <- (R0) temps: [R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R19, R20, R23, R25, V0, V1, V2, V3, V4, V5, V6, V7, V8, V9, V10, V11, V12, V13, V14, V15, V16, V17, V18, V19, V20, V21, V22, V23, V24, V25, V26, V27, V28, V29, V30]

pkg/native_compiler/testcases/reorder_blocks_test.dart.expect

@@ -7,7 +7,7 @@ B0 = EntryBlock() dominates:(B5, B7, B4)
   v24 = Constant(4)
   v1 = Parameter(c1)   # RA: R0 <- ()
   v2 = Parameter(c2)   # RA: R1 <- ()
-  ParallelMove split(R1 -> stack[0])
+  ParallelMove spill(R1 -> stack[0])
   Branch(v1, true: B4, false: B5)   # RA: (R0)
 B4 = TargetBlock() idom:B0
   DirectCall print(v9)   # RA: R0 <- (-) temps: [R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R19, R20, R23, R25, V0, V1, V2, V3, V4, V5, V6, V7, V8, V9, V10, V11, V12, V13, V14, V15, V16, V17, V18, V19, V20, V21, V22, V23, V24, V25, V26, V27, V28, V29, V30]
@@ -64,7 +64,7 @@ B0 = EntryBlock() dominates:(B3)
   Goto(B3)
 B3 = JoinBlock(B0, B30) idom:B0 dominates:(B9, B8) loop-header (depth:1 body:(B3, B8, B12, B17, B30, B16, B24, B23) back-edges:(B30))
   v44 = Phi(v1, v39)   # RA: R0 <- (-, R0)
-  ParallelMove split(R0 -> stack[0])
+  ParallelMove spill(R0 -> stack[0])
   CompareAndBranch int <(v44, v6, true: B8, false: B9)   # RA: (R0, -)
 B8 = TargetBlock() idom:B3 dominates:(B12) in-loop:B3
   ParallelMove control(IntConstant(0) -> R1)
@@ -86,7 +86,7 @@ B17 = TargetBlock() idom:B12 in-loop:B3
 B30 = JoinBlock(B17, B23) idom:B12 in-loop:B3
   ParallelMove split(stack[0] -> R0)
   v39 = BinaryIntOp +(v44, v33)   # RA: R0 <- (R0, -)
-  ParallelMove split(R0 -> stack[0])
+  ParallelMove spill(R0 -> stack[0])
   Goto(B3)
 B9 = TargetBlock() idom:B3
   ParallelMove input(NullConstant(null) -> R0)

runtime/vm/compiler/runtime_api.cc

@@ -370,10 +370,6 @@ uword MakeTagWordForNewSpaceObject(classid_t cid, uword instance_size) {
              dart::Object::ShouldHaveDeeplyImmutabilityBitSet(cid));
 }
 
-word Object::tags_offset() {
-  return 0;
-}
-
 const word UntaggedObject::kCardRememberedBit =
     dart::UntaggedObject::CardRememberedBit::shift();
 
@@ -557,10 +553,6 @@ bool Class::TraceAllocation(const dart::Class& klass) {
   return klass.TraceAllocation(dart::IsolateGroup::Current());
 }
 
-word Instance::first_field_offset() {
-  return TranslateOffsetInWords(dart::Instance::NextFieldOffset());
-}
-
 word Instance::native_fields_array_offset() {
   return TranslateOffsetInWords(dart::Instance::NativeFieldsOffset());
 }

runtime/vm/compiler/runtime_offsets_extracted.h

@@ -205,6 +205,7 @@ static constexpr dart::compiler::target::word ICData_NumArgsTestedShift = 0x0;
 static constexpr dart::compiler::target::word ICData_entries_offset = 0xc;
 static constexpr dart::compiler::target::word ICData_owner_offset = 0x14;
 static constexpr dart::compiler::target::word ICData_state_bits_offset = 0x1c;
+static constexpr dart::compiler::target::word Instance_first_field_offset = 0x4;
 static constexpr dart::compiler::target::word Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word Isolate_finalizers_offset = 0xc;
 static constexpr dart::compiler::target::word
@@ -245,6 +246,7 @@ static constexpr dart::compiler::target::word NativeArguments_retval_offset =
     0xc;
 static constexpr dart::compiler::target::word NativeArguments_thread_offset =
     0x0;
+static constexpr dart::compiler::target::word Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word ObjectStore_double_type_offset =
     0xd8;
 static constexpr dart::compiler::target::word ObjectStore_int_type_offset =
@@ -927,6 +929,7 @@ static constexpr dart::compiler::target::word ICData_NumArgsTestedShift = 0x0;
 static constexpr dart::compiler::target::word ICData_entries_offset = 0x18;
 static constexpr dart::compiler::target::word ICData_owner_offset = 0x28;
 static constexpr dart::compiler::target::word ICData_state_bits_offset = 0x34;
+static constexpr dart::compiler::target::word Instance_first_field_offset = 0x8;
 static constexpr dart::compiler::target::word Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word Isolate_finalizers_offset = 0x18;
 static constexpr dart::compiler::target::word
@@ -968,6 +971,7 @@ static constexpr dart::compiler::target::word NativeArguments_retval_offset =
     0x18;
 static constexpr dart::compiler::target::word NativeArguments_thread_offset =
     0x0;
+static constexpr dart::compiler::target::word Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word ObjectStore_double_type_offset =
     0x1b0;
 static constexpr dart::compiler::target::word ObjectStore_int_type_offset =
@@ -1651,6 +1655,7 @@ static constexpr dart::compiler::target::word ICData_NumArgsTestedShift = 0x0;
 static constexpr dart::compiler::target::word ICData_entries_offset = 0xc;
 static constexpr dart::compiler::target::word ICData_owner_offset = 0x14;
 static constexpr dart::compiler::target::word ICData_state_bits_offset = 0x1c;
+static constexpr dart::compiler::target::word Instance_first_field_offset = 0x4;
 static constexpr dart::compiler::target::word Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word Isolate_finalizers_offset = 0xc;
 static constexpr dart::compiler::target::word
@@ -1691,6 +1696,7 @@ static constexpr dart::compiler::target::word NativeArguments_retval_offset =
     0xc;
 static constexpr dart::compiler::target::word NativeArguments_thread_offset =
     0x0;
+static constexpr dart::compiler::target::word Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word ObjectStore_double_type_offset =
     0xd8;
 static constexpr dart::compiler::target::word ObjectStore_int_type_offset =
@@ -2372,6 +2378,7 @@ static constexpr dart::compiler::target::word ICData_NumArgsTestedShift = 0x0;
 static constexpr dart::compiler::target::word ICData_entries_offset = 0x18;
 static constexpr dart::compiler::target::word ICData_owner_offset = 0x28;
 static constexpr dart::compiler::target::word ICData_state_bits_offset = 0x34;
+static constexpr dart::compiler::target::word Instance_first_field_offset = 0x8;
 static constexpr dart::compiler::target::word Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word Isolate_finalizers_offset = 0x18;
 static constexpr dart::compiler::target::word
@@ -2413,6 +2420,7 @@ static constexpr dart::compiler::target::word NativeArguments_retval_offset =
     0x18;
 static constexpr dart::compiler::target::word NativeArguments_thread_offset =
     0x0;
+static constexpr dart::compiler::target::word Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word ObjectStore_double_type_offset =
     0x1b0;
 static constexpr dart::compiler::target::word ObjectStore_int_type_offset =
@@ -3099,6 +3107,7 @@ static constexpr dart::compiler::target::word ICData_NumArgsTestedShift = 0x0;
 static constexpr dart::compiler::target::word ICData_entries_offset = 0x18;
 static constexpr dart::compiler::target::word ICData_owner_offset = 0x28;
 static constexpr dart::compiler::target::word ICData_state_bits_offset = 0x34;
+static constexpr dart::compiler::target::word Instance_first_field_offset = 0x8;
 static constexpr dart::compiler::target::word Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word Isolate_finalizers_offset = 0x18;
 static constexpr dart::compiler::target::word
@@ -3140,6 +3149,7 @@ static constexpr dart::compiler::target::word NativeArguments_retval_offset =
     0x18;
 static constexpr dart::compiler::target::word NativeArguments_thread_offset =
     0x0;
+static constexpr dart::compiler::target::word Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word ObjectStore_double_type_offset =
     0x1b0;
 static constexpr dart::compiler::target::word ObjectStore_int_type_offset =
@@ -3823,6 +3833,7 @@ static constexpr dart::compiler::target::word ICData_NumArgsTestedShift = 0x0;
 static constexpr dart::compiler::target::word ICData_entries_offset = 0x18;
 static constexpr dart::compiler::target::word ICData_owner_offset = 0x28;
 static constexpr dart::compiler::target::word ICData_state_bits_offset = 0x34;
+static constexpr dart::compiler::target::word Instance_first_field_offset = 0x8;
 static constexpr dart::compiler::target::word Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word Isolate_finalizers_offset = 0x18;
 static constexpr dart::compiler::target::word
@@ -3864,6 +3875,7 @@ static constexpr dart::compiler::target::word NativeArguments_retval_offset =
     0x18;
 static constexpr dart::compiler::target::word NativeArguments_thread_offset =
     0x0;
+static constexpr dart::compiler::target::word Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word ObjectStore_double_type_offset =
     0x1b0;
 static constexpr dart::compiler::target::word ObjectStore_int_type_offset =
@@ -4548,6 +4560,7 @@ static constexpr dart::compiler::target::word ICData_NumArgsTestedShift = 0x0;
 static constexpr dart::compiler::target::word ICData_entries_offset = 0xc;
 static constexpr dart::compiler::target::word ICData_owner_offset = 0x14;
 static constexpr dart::compiler::target::word ICData_state_bits_offset = 0x1c;
+static constexpr dart::compiler::target::word Instance_first_field_offset = 0x4;
 static constexpr dart::compiler::target::word Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word Isolate_finalizers_offset = 0xc;
 static constexpr dart::compiler::target::word
@@ -4588,6 +4601,7 @@ static constexpr dart::compiler::target::word NativeArguments_retval_offset =
     0xc;
 static constexpr dart::compiler::target::word NativeArguments_thread_offset =
     0x0;
+static constexpr dart::compiler::target::word Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word ObjectStore_double_type_offset =
     0xd8;
 static constexpr dart::compiler::target::word ObjectStore_int_type_offset =
@@ -5271,6 +5285,7 @@ static constexpr dart::compiler::target::word ICData_NumArgsTestedShift = 0x0;
 static constexpr dart::compiler::target::word ICData_entries_offset = 0x18;
 static constexpr dart::compiler::target::word ICData_owner_offset = 0x28;
 static constexpr dart::compiler::target::word ICData_state_bits_offset = 0x34;
+static constexpr dart::compiler::target::word Instance_first_field_offset = 0x8;
 static constexpr dart::compiler::target::word Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word Isolate_finalizers_offset = 0x18;
 static constexpr dart::compiler::target::word
@@ -5312,6 +5327,7 @@ static constexpr dart::compiler::target::word NativeArguments_retval_offset =
     0x18;
 static constexpr dart::compiler::target::word NativeArguments_thread_offset =
     0x0;
+static constexpr dart::compiler::target::word Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word ObjectStore_double_type_offset =
     0x1b0;
 static constexpr dart::compiler::target::word ObjectStore_int_type_offset =
@@ -5991,6 +6007,7 @@ static constexpr dart::compiler::target::word ICData_NumArgsTestedShift = 0x0;
 static constexpr dart::compiler::target::word ICData_entries_offset = 0xc;
 static constexpr dart::compiler::target::word ICData_owner_offset = 0x14;
 static constexpr dart::compiler::target::word ICData_state_bits_offset = 0x1c;
+static constexpr dart::compiler::target::word Instance_first_field_offset = 0x4;
 static constexpr dart::compiler::target::word Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word Isolate_finalizers_offset = 0xc;
 static constexpr dart::compiler::target::word IsolateGroup_object_store_offset =
@@ -6029,6 +6046,7 @@ static constexpr dart::compiler::target::word NativeArguments_retval_offset =
     0xc;
 static constexpr dart::compiler::target::word NativeArguments_thread_offset =
     0x0;
+static constexpr dart::compiler::target::word Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word ObjectStore_double_type_offset =
     0xd8;
 static constexpr dart::compiler::target::word ObjectStore_int_type_offset =
@@ -6705,6 +6723,7 @@ static constexpr dart::compiler::target::word ICData_NumArgsTestedShift = 0x0;
 static constexpr dart::compiler::target::word ICData_entries_offset = 0x18;
 static constexpr dart::compiler::target::word ICData_owner_offset = 0x28;
 static constexpr dart::compiler::target::word ICData_state_bits_offset = 0x34;
+static constexpr dart::compiler::target::word Instance_first_field_offset = 0x8;
 static constexpr dart::compiler::target::word Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word Isolate_finalizers_offset = 0x18;
 static constexpr dart::compiler::target::word IsolateGroup_object_store_offset =
@@ -6744,6 +6763,7 @@ static constexpr dart::compiler::target::word NativeArguments_retval_offset =
     0x18;
 static constexpr dart::compiler::target::word NativeArguments_thread_offset =
     0x0;
+static constexpr dart::compiler::target::word Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word ObjectStore_double_type_offset =
     0x1b0;
 static constexpr dart::compiler::target::word ObjectStore_int_type_offset =
@@ -7421,6 +7441,7 @@ static constexpr dart::compiler::target::word ICData_NumArgsTestedShift = 0x0;
 static constexpr dart::compiler::target::word ICData_entries_offset = 0xc;
 static constexpr dart::compiler::target::word ICData_owner_offset = 0x14;
 static constexpr dart::compiler::target::word ICData_state_bits_offset = 0x1c;
+static constexpr dart::compiler::target::word Instance_first_field_offset = 0x4;
 static constexpr dart::compiler::target::word Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word Isolate_finalizers_offset = 0xc;
 static constexpr dart::compiler::target::word IsolateGroup_object_store_offset =
@@ -7459,6 +7480,7 @@ static constexpr dart::compiler::target::word NativeArguments_retval_offset =
     0xc;
 static constexpr dart::compiler::target::word NativeArguments_thread_offset =
     0x0;
+static constexpr dart::compiler::target::word Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word ObjectStore_double_type_offset =
     0xd8;
 static constexpr dart::compiler::target::word ObjectStore_int_type_offset =
@@ -8134,6 +8156,7 @@ static constexpr dart::compiler::target::word ICData_NumArgsTestedShift = 0x0;
 static constexpr dart::compiler::target::word ICData_entries_offset = 0x18;
 static constexpr dart::compiler::target::word ICData_owner_offset = 0x28;
 static constexpr dart::compiler::target::word ICData_state_bits_offset = 0x34;
+static constexpr dart::compiler::target::word Instance_first_field_offset = 0x8;
 static constexpr dart::compiler::target::word Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word Isolate_finalizers_offset = 0x18;
 static constexpr dart::compiler::target::word IsolateGroup_object_store_offset =
@@ -8173,6 +8196,7 @@ static constexpr dart::compiler::target::word NativeArguments_retval_offset =
     0x18;
 static constexpr dart::compiler::target::word NativeArguments_thread_offset =
     0x0;
+static constexpr dart::compiler::target::word Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word ObjectStore_double_type_offset =
     0x1b0;
 static constexpr dart::compiler::target::word ObjectStore_int_type_offset =
@@ -8853,6 +8877,7 @@ static constexpr dart::compiler::target::word ICData_NumArgsTestedShift = 0x0;
 static constexpr dart::compiler::target::word ICData_entries_offset = 0x18;
 static constexpr dart::compiler::target::word ICData_owner_offset = 0x28;
 static constexpr dart::compiler::target::word ICData_state_bits_offset = 0x34;
+static constexpr dart::compiler::target::word Instance_first_field_offset = 0x8;
 static constexpr dart::compiler::target::word Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word Isolate_finalizers_offset = 0x18;
 static constexpr dart::compiler::target::word IsolateGroup_object_store_offset =
@@ -8892,6 +8917,7 @@ static constexpr dart::compiler::target::word NativeArguments_retval_offset =
     0x18;
 static constexpr dart::compiler::target::word NativeArguments_thread_offset =
     0x0;
+static constexpr dart::compiler::target::word Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word ObjectStore_double_type_offset =
     0x1b0;
 static constexpr dart::compiler::target::word ObjectStore_int_type_offset =
@@ -9569,6 +9595,7 @@ static constexpr dart::compiler::target::word ICData_NumArgsTestedShift = 0x0;
 static constexpr dart::compiler::target::word ICData_entries_offset = 0x18;
 static constexpr dart::compiler::target::word ICData_owner_offset = 0x28;
 static constexpr dart::compiler::target::word ICData_state_bits_offset = 0x34;
+static constexpr dart::compiler::target::word Instance_first_field_offset = 0x8;
 static constexpr dart::compiler::target::word Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word Isolate_finalizers_offset = 0x18;
 static constexpr dart::compiler::target::word IsolateGroup_object_store_offset =
@@ -9608,6 +9635,7 @@ static constexpr dart::compiler::target::word NativeArguments_retval_offset =
     0x18;
 static constexpr dart::compiler::target::word NativeArguments_thread_offset =
     0x0;
+static constexpr dart::compiler::target::word Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word ObjectStore_double_type_offset =
     0x1b0;
 static constexpr dart::compiler::target::word ObjectStore_int_type_offset =
@@ -10286,6 +10314,7 @@ static constexpr dart::compiler::target::word ICData_NumArgsTestedShift = 0x0;
 static constexpr dart::compiler::target::word ICData_entries_offset = 0xc;
 static constexpr dart::compiler::target::word ICData_owner_offset = 0x14;
 static constexpr dart::compiler::target::word ICData_state_bits_offset = 0x1c;
+static constexpr dart::compiler::target::word Instance_first_field_offset = 0x4;
 static constexpr dart::compiler::target::word Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word Isolate_finalizers_offset = 0xc;
 static constexpr dart::compiler::target::word IsolateGroup_object_store_offset =
@@ -10324,6 +10353,7 @@ static constexpr dart::compiler::target::word NativeArguments_retval_offset =
     0xc;
 static constexpr dart::compiler::target::word NativeArguments_thread_offset =
     0x0;
+static constexpr dart::compiler::target::word Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word ObjectStore_double_type_offset =
     0xd8;
 static constexpr dart::compiler::target::word ObjectStore_int_type_offset =
@@ -11001,6 +11031,7 @@ static constexpr dart::compiler::target::word ICData_NumArgsTestedShift = 0x0;
 static constexpr dart::compiler::target::word ICData_entries_offset = 0x18;
 static constexpr dart::compiler::target::word ICData_owner_offset = 0x28;
 static constexpr dart::compiler::target::word ICData_state_bits_offset = 0x34;
+static constexpr dart::compiler::target::word Instance_first_field_offset = 0x8;
 static constexpr dart::compiler::target::word Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word Isolate_finalizers_offset = 0x18;
 static constexpr dart::compiler::target::word IsolateGroup_object_store_offset =
@@ -11040,6 +11071,7 @@ static constexpr dart::compiler::target::word NativeArguments_retval_offset =
     0x18;
 static constexpr dart::compiler::target::word NativeArguments_thread_offset =
     0x0;
+static constexpr dart::compiler::target::word Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word ObjectStore_double_type_offset =
     0x1b0;
 static constexpr dart::compiler::target::word ObjectStore_int_type_offset =
@@ -11743,6 +11775,8 @@ static constexpr dart::compiler::target::word AOT_ICData_entries_offset = 0xc;
 static constexpr dart::compiler::target::word AOT_ICData_owner_offset = 0x10;
 static constexpr dart::compiler::target::word AOT_ICData_state_bits_offset =
     0x14;
+static constexpr dart::compiler::target::word AOT_Instance_first_field_offset =
+    0x4;
 static constexpr dart::compiler::target::word AOT_Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word AOT_Isolate_finalizers_offset =
     0xc;
@@ -11786,6 +11820,7 @@ static constexpr dart::compiler::target::word
     AOT_NativeArguments_retval_offset = 0xc;
 static constexpr dart::compiler::target::word
     AOT_NativeArguments_thread_offset = 0x0;
+static constexpr dart::compiler::target::word AOT_Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word
     AOT_ObjectStore_double_type_offset = 0xd8;
 static constexpr dart::compiler::target::word AOT_ObjectStore_int_type_offset =
@@ -12544,6 +12579,8 @@ static constexpr dart::compiler::target::word AOT_ICData_entries_offset = 0x18;
 static constexpr dart::compiler::target::word AOT_ICData_owner_offset = 0x20;
 static constexpr dart::compiler::target::word AOT_ICData_state_bits_offset =
     0x28;
+static constexpr dart::compiler::target::word AOT_Instance_first_field_offset =
+    0x8;
 static constexpr dart::compiler::target::word AOT_Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word AOT_Isolate_finalizers_offset =
     0x18;
@@ -12587,6 +12624,7 @@ static constexpr dart::compiler::target::word
     AOT_NativeArguments_retval_offset = 0x18;
 static constexpr dart::compiler::target::word
     AOT_NativeArguments_thread_offset = 0x0;
+static constexpr dart::compiler::target::word AOT_Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word
     AOT_ObjectStore_double_type_offset = 0x1b0;
 static constexpr dart::compiler::target::word AOT_ObjectStore_int_type_offset =
@@ -13352,6 +13390,8 @@ static constexpr dart::compiler::target::word AOT_ICData_entries_offset = 0x18;
 static constexpr dart::compiler::target::word AOT_ICData_owner_offset = 0x20;
 static constexpr dart::compiler::target::word AOT_ICData_state_bits_offset =
     0x28;
+static constexpr dart::compiler::target::word AOT_Instance_first_field_offset =
+    0x8;
 static constexpr dart::compiler::target::word AOT_Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word AOT_Isolate_finalizers_offset =
     0x18;
@@ -13395,6 +13435,7 @@ static constexpr dart::compiler::target::word
     AOT_NativeArguments_retval_offset = 0x18;
 static constexpr dart::compiler::target::word
     AOT_NativeArguments_thread_offset = 0x0;
+static constexpr dart::compiler::target::word AOT_Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word
     AOT_ObjectStore_double_type_offset = 0x1b0;
 static constexpr dart::compiler::target::word AOT_ObjectStore_int_type_offset =
@@ -14156,6 +14197,8 @@ static constexpr dart::compiler::target::word AOT_ICData_entries_offset = 0x18;
 static constexpr dart::compiler::target::word AOT_ICData_owner_offset = 0x20;
 static constexpr dart::compiler::target::word AOT_ICData_state_bits_offset =
     0x28;
+static constexpr dart::compiler::target::word AOT_Instance_first_field_offset =
+    0x8;
 static constexpr dart::compiler::target::word AOT_Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word AOT_Isolate_finalizers_offset =
     0x18;
@@ -14199,6 +14242,7 @@ static constexpr dart::compiler::target::word
     AOT_NativeArguments_retval_offset = 0x18;
 static constexpr dart::compiler::target::word
     AOT_NativeArguments_thread_offset = 0x0;
+static constexpr dart::compiler::target::word AOT_Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word
     AOT_ObjectStore_double_type_offset = 0x1b0;
 static constexpr dart::compiler::target::word AOT_ObjectStore_int_type_offset =
@@ -14960,6 +15004,8 @@ static constexpr dart::compiler::target::word AOT_ICData_entries_offset = 0x18;
 static constexpr dart::compiler::target::word AOT_ICData_owner_offset = 0x20;
 static constexpr dart::compiler::target::word AOT_ICData_state_bits_offset =
     0x28;
+static constexpr dart::compiler::target::word AOT_Instance_first_field_offset =
+    0x8;
 static constexpr dart::compiler::target::word AOT_Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word AOT_Isolate_finalizers_offset =
     0x18;
@@ -15003,6 +15049,7 @@ static constexpr dart::compiler::target::word
     AOT_NativeArguments_retval_offset = 0x18;
 static constexpr dart::compiler::target::word
     AOT_NativeArguments_thread_offset = 0x0;
+static constexpr dart::compiler::target::word AOT_Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word
     AOT_ObjectStore_double_type_offset = 0x1b0;
 static constexpr dart::compiler::target::word AOT_ObjectStore_int_type_offset =
@@ -15766,6 +15813,8 @@ static constexpr dart::compiler::target::word AOT_ICData_entries_offset = 0xc;
 static constexpr dart::compiler::target::word AOT_ICData_owner_offset = 0x10;
 static constexpr dart::compiler::target::word AOT_ICData_state_bits_offset =
     0x14;
+static constexpr dart::compiler::target::word AOT_Instance_first_field_offset =
+    0x4;
 static constexpr dart::compiler::target::word AOT_Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word AOT_Isolate_finalizers_offset =
     0xc;
@@ -15809,6 +15858,7 @@ static constexpr dart::compiler::target::word
     AOT_NativeArguments_retval_offset = 0xc;
 static constexpr dart::compiler::target::word
     AOT_NativeArguments_thread_offset = 0x0;
+static constexpr dart::compiler::target::word AOT_Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word
     AOT_ObjectStore_double_type_offset = 0xd8;
 static constexpr dart::compiler::target::word AOT_ObjectStore_int_type_offset =
@@ -16568,6 +16618,8 @@ static constexpr dart::compiler::target::word AOT_ICData_entries_offset = 0x18;
 static constexpr dart::compiler::target::word AOT_ICData_owner_offset = 0x20;
 static constexpr dart::compiler::target::word AOT_ICData_state_bits_offset =
     0x28;
+static constexpr dart::compiler::target::word AOT_Instance_first_field_offset =
+    0x8;
 static constexpr dart::compiler::target::word AOT_Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word AOT_Isolate_finalizers_offset =
     0x18;
@@ -16611,6 +16663,7 @@ static constexpr dart::compiler::target::word
     AOT_NativeArguments_retval_offset = 0x18;
 static constexpr dart::compiler::target::word
     AOT_NativeArguments_thread_offset = 0x0;
+static constexpr dart::compiler::target::word AOT_Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word
     AOT_ObjectStore_double_type_offset = 0x1b0;
 static constexpr dart::compiler::target::word AOT_ObjectStore_int_type_offset =
@@ -17366,6 +17419,8 @@ static constexpr dart::compiler::target::word AOT_ICData_entries_offset = 0xc;
 static constexpr dart::compiler::target::word AOT_ICData_owner_offset = 0x10;
 static constexpr dart::compiler::target::word AOT_ICData_state_bits_offset =
     0x14;
+static constexpr dart::compiler::target::word AOT_Instance_first_field_offset =
+    0x4;
 static constexpr dart::compiler::target::word AOT_Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word AOT_Isolate_finalizers_offset =
     0xc;
@@ -17407,6 +17462,7 @@ static constexpr dart::compiler::target::word
     AOT_NativeArguments_retval_offset = 0xc;
 static constexpr dart::compiler::target::word
     AOT_NativeArguments_thread_offset = 0x0;
+static constexpr dart::compiler::target::word AOT_Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word
     AOT_ObjectStore_double_type_offset = 0xd8;
 static constexpr dart::compiler::target::word AOT_ObjectStore_int_type_offset =
@@ -18158,6 +18214,8 @@ static constexpr dart::compiler::target::word AOT_ICData_entries_offset = 0x18;
 static constexpr dart::compiler::target::word AOT_ICData_owner_offset = 0x20;
 static constexpr dart::compiler::target::word AOT_ICData_state_bits_offset =
     0x28;
+static constexpr dart::compiler::target::word AOT_Instance_first_field_offset =
+    0x8;
 static constexpr dart::compiler::target::word AOT_Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word AOT_Isolate_finalizers_offset =
     0x18;
@@ -18199,6 +18257,7 @@ static constexpr dart::compiler::target::word
     AOT_NativeArguments_retval_offset = 0x18;
 static constexpr dart::compiler::target::word
     AOT_NativeArguments_thread_offset = 0x0;
+static constexpr dart::compiler::target::word AOT_Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word
     AOT_ObjectStore_double_type_offset = 0x1b0;
 static constexpr dart::compiler::target::word AOT_ObjectStore_int_type_offset =
@@ -18957,6 +19016,8 @@ static constexpr dart::compiler::target::word AOT_ICData_entries_offset = 0x18;
 static constexpr dart::compiler::target::word AOT_ICData_owner_offset = 0x20;
 static constexpr dart::compiler::target::word AOT_ICData_state_bits_offset =
     0x28;
+static constexpr dart::compiler::target::word AOT_Instance_first_field_offset =
+    0x8;
 static constexpr dart::compiler::target::word AOT_Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word AOT_Isolate_finalizers_offset =
     0x18;
@@ -18998,6 +19059,7 @@ static constexpr dart::compiler::target::word
     AOT_NativeArguments_retval_offset = 0x18;
 static constexpr dart::compiler::target::word
     AOT_NativeArguments_thread_offset = 0x0;
+static constexpr dart::compiler::target::word AOT_Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word
     AOT_ObjectStore_double_type_offset = 0x1b0;
 static constexpr dart::compiler::target::word AOT_ObjectStore_int_type_offset =
@@ -19752,6 +19814,8 @@ static constexpr dart::compiler::target::word AOT_ICData_entries_offset = 0x18;
 static constexpr dart::compiler::target::word AOT_ICData_owner_offset = 0x20;
 static constexpr dart::compiler::target::word AOT_ICData_state_bits_offset =
     0x28;
+static constexpr dart::compiler::target::word AOT_Instance_first_field_offset =
+    0x8;
 static constexpr dart::compiler::target::word AOT_Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word AOT_Isolate_finalizers_offset =
     0x18;
@@ -19793,6 +19857,7 @@ static constexpr dart::compiler::target::word
     AOT_NativeArguments_retval_offset = 0x18;
 static constexpr dart::compiler::target::word
     AOT_NativeArguments_thread_offset = 0x0;
+static constexpr dart::compiler::target::word AOT_Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word
     AOT_ObjectStore_double_type_offset = 0x1b0;
 static constexpr dart::compiler::target::word AOT_ObjectStore_int_type_offset =
@@ -20547,6 +20612,8 @@ static constexpr dart::compiler::target::word AOT_ICData_entries_offset = 0x18;
 static constexpr dart::compiler::target::word AOT_ICData_owner_offset = 0x20;
 static constexpr dart::compiler::target::word AOT_ICData_state_bits_offset =
     0x28;
+static constexpr dart::compiler::target::word AOT_Instance_first_field_offset =
+    0x8;
 static constexpr dart::compiler::target::word AOT_Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word AOT_Isolate_finalizers_offset =
     0x18;
@@ -20588,6 +20655,7 @@ static constexpr dart::compiler::target::word
     AOT_NativeArguments_retval_offset = 0x18;
 static constexpr dart::compiler::target::word
     AOT_NativeArguments_thread_offset = 0x0;
+static constexpr dart::compiler::target::word AOT_Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word
     AOT_ObjectStore_double_type_offset = 0x1b0;
 static constexpr dart::compiler::target::word AOT_ObjectStore_int_type_offset =
@@ -21344,6 +21412,8 @@ static constexpr dart::compiler::target::word AOT_ICData_entries_offset = 0xc;
 static constexpr dart::compiler::target::word AOT_ICData_owner_offset = 0x10;
 static constexpr dart::compiler::target::word AOT_ICData_state_bits_offset =
     0x14;
+static constexpr dart::compiler::target::word AOT_Instance_first_field_offset =
+    0x4;
 static constexpr dart::compiler::target::word AOT_Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word AOT_Isolate_finalizers_offset =
     0xc;
@@ -21385,6 +21455,7 @@ static constexpr dart::compiler::target::word
     AOT_NativeArguments_retval_offset = 0xc;
 static constexpr dart::compiler::target::word
     AOT_NativeArguments_thread_offset = 0x0;
+static constexpr dart::compiler::target::word AOT_Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word
     AOT_ObjectStore_double_type_offset = 0xd8;
 static constexpr dart::compiler::target::word AOT_ObjectStore_int_type_offset =
@@ -22137,6 +22208,8 @@ static constexpr dart::compiler::target::word AOT_ICData_entries_offset = 0x18;
 static constexpr dart::compiler::target::word AOT_ICData_owner_offset = 0x20;
 static constexpr dart::compiler::target::word AOT_ICData_state_bits_offset =
     0x28;
+static constexpr dart::compiler::target::word AOT_Instance_first_field_offset =
+    0x8;
 static constexpr dart::compiler::target::word AOT_Int32x4_value_offset = 0x8;
 static constexpr dart::compiler::target::word AOT_Isolate_finalizers_offset =
     0x18;
@@ -22178,6 +22251,7 @@ static constexpr dart::compiler::target::word
     AOT_NativeArguments_retval_offset = 0x18;
 static constexpr dart::compiler::target::word
     AOT_NativeArguments_thread_offset = 0x0;
+static constexpr dart::compiler::target::word AOT_Object_tags_offset = 0x0;
 static constexpr dart::compiler::target::word
     AOT_ObjectStore_double_type_offset = 0x1b0;
 static constexpr dart::compiler::target::word AOT_ObjectStore_int_type_offset =

runtime/vm/compiler/runtime_offsets_list.h

@@ -168,6 +168,7 @@
   FIELD(ICData, entries_offset)                                                \
   FIELD(ICData, owner_offset)                                                  \
   FIELD(ICData, state_bits_offset)                                             \
+  FIELD(Instance, first_field_offset)                                          \
   FIELD(Int32x4, value_offset)                                                 \
   FIELD(Isolate, finalizers_offset)                                            \
   NOT_IN_PRODUCT(FIELD(Isolate, has_resumption_breakpoints_offset))            \
@@ -191,6 +192,7 @@
   FIELD(NativeArguments, argv_offset)                                          \
   FIELD(NativeArguments, retval_offset)                                        \
   FIELD(NativeArguments, thread_offset)                                        \
+  FIELD(Object, tags_offset)                                                   \
   FIELD(ObjectStore, double_type_offset)                                       \
   FIELD(ObjectStore, int_type_offset)                                          \
   FIELD(ObjectStore, record_field_names_offset)                                \

runtime/vm/module_snapshot.cc

@@ -82,6 +82,14 @@ class ModuleSnapshot : public AllStatic {
     kImplicitSetter,
     kFieldInitializer,
   };
+
+  // Object pool entry kinds in the module snapshots.
+  // Should match ObjectPoolEntryKind enum
+  // declared in pkg/native_compiler/lib/snapshot/snapshot.dart.
+  enum ObjectPoolEntryKind {
+    kObjectRef,
+    kNewObjectTags,
+  };
 };
 
 class Deserializer;
@@ -714,7 +722,11 @@ class CodeDeserializationCluster : public DeserializationCluster {
         }
 #endif  // !defined(PRODUCT) || defined(FORCE_INCLUDE_DISASSEMBLER)
       } else {
-        UNREACHABLE();
+#if !defined(PRODUCT) || defined(FORCE_INCLUDE_DISASSEMBLER)
+        if (FLAG_disassemble_stubs) {
+          Disassembler::DisassembleStub("", code);
+        }
+#endif  // !defined(PRODUCT) || defined(FORCE_INCLUDE_DISASSEMBLER)
       }
 
 #if !defined(PRODUCT)
@@ -744,10 +756,14 @@ class ObjectPoolDeserializationCluster : public DeserializationCluster {
   void ReadFill(Deserializer* d_) override {
     Deserializer::Local d(d_);
 
-    const uint8_t entry_bits =
+    const uint8_t tagged_entry_bits =
         ObjectPool::EncodeBits(ObjectPool::EntryType::kTaggedObject,
-                               ObjectPool::Patchability::kPatchable,
-                               ObjectPool::SnapshotBehavior::kSnapshotable);
+                               ObjectPool::Patchability::kNotPatchable,
+                               ObjectPool::SnapshotBehavior::kNotSnapshotable);
+    const uint8_t immediate_entry_bits =
+        ObjectPool::EncodeBits(ObjectPool::EntryType::kImmediate,
+                               ObjectPool::Patchability::kNotPatchable,
+                               ObjectPool::SnapshotBehavior::kNotSnapshotable);
 
     for (intptr_t id = start_index_, n = stop_index_; id < n; id++) {
       const intptr_t length = d.ReadUnsigned();
@@ -756,9 +772,26 @@ class ObjectPoolDeserializationCluster : public DeserializationCluster {
                                      ObjectPool::InstanceSize(length));
       pool->untag()->length_ = length;
       for (intptr_t j = 0; j < length; j++) {
-        pool->untag()->entry_bits()[j] = entry_bits;
-        UntaggedObjectPool::Entry& entry = pool->untag()->data()[j];
-        entry.raw_obj_ = d.ReadRef();
+        const auto kind =
+            static_cast<ModuleSnapshot::ObjectPoolEntryKind>(d.ReadUnsigned());
+        switch (kind) {
+          case ModuleSnapshot::kObjectRef: {
+            pool->untag()->entry_bits()[j] = tagged_entry_bits;
+            UntaggedObjectPool::Entry& entry = pool->untag()->data()[j];
+            entry.raw_obj_ = d.ReadRef();
+            break;
+          }
+          case ModuleSnapshot::kNewObjectTags: {
+            ClassPtr cls = static_cast<ClassPtr>(d.ReadRef());
+            pool->untag()->entry_bits()[j] = immediate_entry_bits;
+            UntaggedObjectPool::Entry& entry = pool->untag()->data()[j];
+            entry.raw_value_ = compiler::target::MakeTagWordForNewSpaceObject(
+                cls->untag()->id_,
+                Object::RoundedAllocationSize(Class::host_instance_size(cls) *
+                                              kCompressedWordSize));
+            break;
+          }
+        }
       }
     }
   }
@@ -771,6 +804,9 @@ class ObjectPoolDeserializationCluster : public DeserializationCluster {
       pool ^= refs.At(id);
 
       for (intptr_t i = 0, length = pool.Length(); i < length; ++i) {
+        if (pool.TypeAt(i) != ObjectPool::EntryType::kTaggedObject) {
+          continue;
+        }
         obj = pool.ObjectAt(i);
         if (obj.IsAbstractType() || obj.IsTypeArguments()) {
           obj = Instance::Cast(obj).Canonicalize(d->thread());

runtime/vm/object.h

@@ -1140,6 +1140,7 @@ class Object {
   friend class OneByteString;
   friend class TwoByteString;
   friend class Thread;
+  friend class module_snapshot::ObjectPoolDeserializationCluster;
 
 #define REUSABLE_FRIEND_DECLARATION(name)                                      \
   friend class Reusable##name##HandleScope;
@@ -8690,6 +8691,8 @@ class Instance : public Object {
 
   static intptr_t NativeFieldsOffset() { return sizeof(UntaggedObject); }
 
+  static intptr_t first_field_offset() { return NextFieldOffset(); }
+
  protected:
 #ifndef PRODUCT
   virtual void PrintSharedInstanceJSON(JSONObject* jsobj,

runtime/vm/raw_object.h

@@ -1325,6 +1325,7 @@ class UntaggedClass : public UntaggedObject {
   friend class CidRewriteVisitor;
   friend class FinalizeVMIsolateVisitor;
   friend class Api;
+  friend class module_snapshot::ObjectPoolDeserializationCluster;
 };
 
 class UntaggedPatchClass : public UntaggedObject {