[vm] Remove _HashFieldBase

This class is structurally equivalent to _HashVMBase and the only reason
for it to exist for inability of normal Dart classes to extend
_HashVMBase - but this can worked around by properly configuring
_HashVMBase class in bootstrapping.

TEST=ci

Change-Id: I5ca401e274920d2b4739424c6b6595306a6a6964
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/494140
Commit-Queue: Slava Egorov <vegorov@google.com>
Reviewed-by: Alexander Markov <alexmarkov@google.com>

pkg/native_compiler/lib/runtime/object_layout.dart

@@ -132,7 +132,7 @@ class ObjectLayout {
   };
 
   late final Map<String, int> _dartCompactHashInstanceSize = {
-    '_HashVMBase': vmOffsets.LinkedHashBase_InstanceSize,
+    '_LinkedHashBase': vmOffsets.LinkedHashBase_InstanceSize,
   };
 
   late final ast.Library _typedDataLibrary = GlobalContext

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

@@ -144,6 +144,7 @@ base class VMOffsets {
   int get LinkedHashBase_index_offset => throw 'Unknown';
   int get LinkedHashBase_type_arguments_offset => throw 'Unknown';
   int get LinkedHashBase_used_data_offset => throw 'Unknown';
+  int get LinkedHashBase_NextFieldOffset => throw 'Unknown';
   int get LocalHandle_ptr_offset => throw 'Unknown';
   int get MarkingStackBlock_pointers_offset => throw 'Unknown';
   int get MarkingStackBlock_top_offset => throw 'Unknown';
@@ -856,6 +857,8 @@ final class Arm64VMOffsets extends VMOffsets {
   @override
   int get LinkedHashBase_used_data_offset => 0x20;
   @override
+  int get LinkedHashBase_NextFieldOffset => 0x38;
+  @override
   int get LocalHandle_ptr_offset => 0x0;
   @override
   int get MarkingStackBlock_pointers_offset => 0x10;
@@ -1813,6 +1816,8 @@ final class Arm64ProductVMOffsets extends VMOffsets {
   @override
   int get LinkedHashBase_used_data_offset => 0x20;
   @override
+  int get LinkedHashBase_NextFieldOffset => 0x38;
+  @override
   int get LocalHandle_ptr_offset => 0x0;
   @override
   int get MarkingStackBlock_pointers_offset => 0x10;
@@ -2868,6 +2873,7 @@ enum ClassId {
   StringCid,
   OneByteStringCid,
   TwoByteStringCid,
+  LinkedHashBaseCid,
   FfiNativeFunctionCid,
   FfiInt8Cid,
   FfiInt16Cid,

pkg/vm/testcases/transformations/type_flow/transformer/class_generics_case1.dart.expect

@@ -21,7 +21,7 @@ class InheritedElement extends self::Element {
   [@vm.inferred-return-type.metadata=dart.core::Null? (value: null)]
   [@vm.procedure-attributes.metadata=methodOrSetterCalledDynamically:false,getterCalledDynamically:false,hasThisUses:false,hasTearOffUses:false,methodOrSetterSelectorId:2,getterSelectorId:3]
   method setDependencies([@vm.inferred-arg-type.metadata=!] self::Element dependent, [@vm.inferred-arg-type.metadata=dart.core::_Smi?] core::Object? value) → void {
-    [@vm.call-site-attributes.metadata=receiverType:dart.core::Map<#lib::Element, dart.core::Object?>] [@vm.direct-call.metadata=dart._compact_hash::__Map&_HashVMBase&MapMixin&_HashBase&_OperatorEqualsAndHashCode&_LinkedHashMapMixin.[]=] [@vm.inferred-type.metadata=? (skip check)] [@vm.direct-call.metadata=#lib::InheritedElement._dependents] [@vm.inferred-type.metadata=dart._compact_hash::_Map<#lib::Element, dart.core::Object?>] this.{self::InheritedElement::_dependents}{core::Map<self::Element, core::Object?>}.{core::Map::[]=}(dependent, value){(self::Element, core::Object?) → void};
+    [@vm.call-site-attributes.metadata=receiverType:dart.core::Map<#lib::Element, dart.core::Object?>] [@vm.direct-call.metadata=dart._compact_hash::__Map&_LinkedHashBase&MapMixin&_HashBase&_OperatorEqualsAndHashCode&_LinkedHashMapMixin.[]=] [@vm.inferred-type.metadata=? (skip check)] [@vm.direct-call.metadata=#lib::InheritedElement._dependents] [@vm.inferred-type.metadata=dart._compact_hash::_Map<#lib::Element, dart.core::Object?>] this.{self::InheritedElement::_dependents}{core::Map<self::Element, core::Object?>}.{core::Map::[]=}(dependent, value){(self::Element, core::Object?) → void};
   }
 }
 

pkg/vm/testcases/transformations/type_flow/transformer/const_map.dart.expect

@@ -16,7 +16,7 @@ class _Attribute extends core::Object {
 
   [@vm.inferred-return-type.metadata=#lib::_Attribute]
   static method fromReader() → self::_Attribute {
-    final self::_AttributeName name = [@vm.direct-call.metadata=dart._compact_hash::__ConstMap&_HashVMImmutableBase&MapMixin&_HashBase&_OperatorEqualsAndCanonicalHashCode&_LinkedHashMapMixin&_UnmodifiableMapMixin&_ImmutableLinkedHashMapMixin.[]] [@vm.inferred-type.metadata=#lib::_AttributeName? (skip check)] #C8.{core::Map::[]}(#C1){(core::Object?) → self::_AttributeName?}!;
+    final self::_AttributeName name = [@vm.direct-call.metadata=dart._compact_hash::__ConstMap&_LinkedHashImmutableBase&MapMixin&_HashBase&_OperatorEqualsAndCanonicalHashCode&_LinkedHashMapMixin&_UnmodifiableMapMixin&_ImmutableLinkedHashMapMixin.[]] [@vm.inferred-type.metadata=#lib::_AttributeName? (skip check)] #C8.{core::Map::[]}(#C1){(core::Object?) → self::_AttributeName?}!;
     return new self::_Attribute::_();
   }
 }

pkg/vm/testcases/transformations/type_flow/transformer/const_set.dart.expect

@@ -16,7 +16,7 @@ class _Attribute extends core::Object {
 
   [@vm.inferred-return-type.metadata=#lib::_Attribute]
   static method fromReader() → self::_Attribute {
-    final core::bool name = [@vm.direct-call.metadata=dart._compact_hash::__ConstSet&_HashVMImmutableBase&SetMixin&_HashBase&_OperatorEqualsAndCanonicalHashCode&_LinkedHashSetMixin&_UnmodifiableSetMixin&_ImmutableLinkedHashSetMixin.contains] [@vm.inferred-type.metadata=? (skip check)] #C3.{core::Set::contains}(#C2){(core::Object?) → core::bool};
+    final core::bool name = [@vm.direct-call.metadata=dart._compact_hash::__ConstSet&_LinkedHashImmutableBase&SetMixin&_HashBase&_OperatorEqualsAndCanonicalHashCode&_LinkedHashSetMixin&_UnmodifiableSetMixin&_ImmutableLinkedHashSetMixin.contains] [@vm.inferred-type.metadata=? (skip check)] #C3.{core::Set::contains}(#C2){(core::Object?) → core::bool};
     return let final self::_AttributeName #t1 = #C8.{core::List::[]}(#C2){(core::int) → self::_AttributeName} in new self::_Attribute::_();
   }
 }

runtime/vm/class_id.h

@@ -312,6 +312,7 @@ static constexpr intptr_t kClassIdTagMax = (1 << 20) - 1;
   CID(FreeListElement)                                                         \
   CID(ForwardingCorpse)                                                        \
   CLASS_LIST(DEFINE_CLASS_ID)                                                  \
+  CID(LinkedHashBaseCid)                                                       \
   CLASS_LIST_FFI(DEFINE_FFI_CLASS_ID)                                          \
   CLASS_LIST_TYPED_DATA(DEFINE_TYPED_DATA_CLASS_ID)                            \
   CID(ByteDataViewCid)                                                         \

runtime/vm/compiler/recognized_methods_list.h

@@ -78,31 +78,31 @@ namespace dart {
   V(CoreLibrary, _Smi, get:hashCode, Smi_hashCode, 0x75c3b512)                 \
   V(CoreLibrary, _Mint, get:hashCode, Mint_hashCode, 0x75c3b512)               \
   V(CoreLibrary, _Double, get:hashCode, Double_hashCode, 0x75c3b8d3)           \
-  V(CompactHashLibrary, _HashVMBase, get:_index, LinkedHashBase_getIndex,      \
+  V(CompactHashLibrary, _LinkedHashBase, get:_index, LinkedHashBase_getIndex,  \
     0xb49e7210)                                                                \
-  V(CompactHashLibrary, _HashVMBase, set:_index, LinkedHashBase_setIndex,      \
+  V(CompactHashLibrary, _LinkedHashBase, set:_index, LinkedHashBase_setIndex,  \
     0xcf36944c)                                                                \
-  V(CompactHashLibrary, _HashVMBase, get:_data, LinkedHashBase_getData,        \
+  V(CompactHashLibrary, _LinkedHashBase, get:_data, LinkedHashBase_getData,    \
     0x82aeadd7)                                                                \
-  V(CompactHashLibrary, _HashVMBase, set:_data, LinkedHashBase_setData,        \
+  V(CompactHashLibrary, _LinkedHashBase, set:_data, LinkedHashBase_setData,    \
     0xc1465c93)                                                                \
-  V(CompactHashLibrary, _HashVMBase, get:_usedData,                            \
+  V(CompactHashLibrary, _LinkedHashBase, get:_usedData,                        \
     LinkedHashBase_getUsedData, 0x74808f38)                                    \
-  V(CompactHashLibrary, _HashVMBase, set:_usedData,                            \
+  V(CompactHashLibrary, _LinkedHashBase, set:_usedData,                        \
     LinkedHashBase_setUsedData, 0xe14082f4)                                    \
-  V(CompactHashLibrary, _HashVMBase, get:_hashMask,                            \
+  V(CompactHashLibrary, _LinkedHashBase, get:_hashMask,                        \
     LinkedHashBase_getHashMask, 0x53cd6dce)                                    \
-  V(CompactHashLibrary, _HashVMBase, set:_hashMask,                            \
+  V(CompactHashLibrary, _LinkedHashBase, set:_hashMask,                        \
     LinkedHashBase_setHashMask, 0xc08d618a)                                    \
-  V(CompactHashLibrary, _HashVMBase, get:_deletedKeys,                         \
+  V(CompactHashLibrary, _LinkedHashBase, get:_deletedKeys,                     \
     LinkedHashBase_getDeletedKeys, 0x75eeb895)                                 \
-  V(CompactHashLibrary, _HashVMBase, set:_deletedKeys,                         \
+  V(CompactHashLibrary, _LinkedHashBase, set:_deletedKeys,                     \
     LinkedHashBase_setDeletedKeys, 0xe2aeac51)                                 \
-  V(CompactHashLibrary, _HashVMImmutableBase, get:_data,                       \
+  V(CompactHashLibrary, _LinkedHashImmutableBase, get:_data,                   \
     ImmutableLinkedHashBase_getData, 0x82aeadd7)                               \
-  V(CompactHashLibrary, _HashVMImmutableBase, get:_indexNullable,              \
+  V(CompactHashLibrary, _LinkedHashImmutableBase, get:_indexNullable,          \
     ImmutableLinkedHashBase_getIndex, 0xfe7649ae)                              \
-  V(CompactHashLibrary, _HashVMImmutableBase, set:_index,                      \
+  V(CompactHashLibrary, _LinkedHashImmutableBase, set:_index,                  \
     ImmutableLinkedHashBase_setIndexStoreRelease, 0xcf36944c)                  \
   V(CompactHashLibrary, ::, get:_uninitializedIndex,                           \
     CompactHash_uninitializedIndex, 0xa25a79e6)                                \

runtime/vm/compiler/runtime_api.h

@@ -671,6 +671,7 @@ class LinkedHashBase : public AllStatic {
   static word deleted_keys_offset();
   static word type_arguments_offset();
   static word InstanceSize();
+  static word NextFieldOffset();
 };
 
 class ImmutableLinkedHashBase : public LinkedHashBase {

runtime/vm/compiler/runtime_offsets_extracted.h

@@ -271,6 +271,8 @@ static constexpr dart::compiler::target::word
     LinkedHashBase_type_arguments_offset = 0x4;
 static constexpr dart::compiler::target::word LinkedHashBase_used_data_offset =
     0x10;
+static constexpr dart::compiler::target::word LinkedHashBase_NextFieldOffset =
+    0x1c;
 static constexpr dart::compiler::target::word LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     MarkingStackBlock_pointers_offset = 0x8;
@@ -1039,6 +1041,8 @@ static constexpr dart::compiler::target::word
     LinkedHashBase_type_arguments_offset = 0x8;
 static constexpr dart::compiler::target::word LinkedHashBase_used_data_offset =
     0x20;
+static constexpr dart::compiler::target::word LinkedHashBase_NextFieldOffset =
+    0x38;
 static constexpr dart::compiler::target::word LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     MarkingStackBlock_pointers_offset = 0x10;
@@ -1806,6 +1810,8 @@ static constexpr dart::compiler::target::word
     LinkedHashBase_type_arguments_offset = 0x4;
 static constexpr dart::compiler::target::word LinkedHashBase_used_data_offset =
     0x10;
+static constexpr dart::compiler::target::word LinkedHashBase_NextFieldOffset =
+    0x1c;
 static constexpr dart::compiler::target::word LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     MarkingStackBlock_pointers_offset = 0x8;
@@ -2573,6 +2579,8 @@ static constexpr dart::compiler::target::word
     LinkedHashBase_type_arguments_offset = 0x8;
 static constexpr dart::compiler::target::word LinkedHashBase_used_data_offset =
     0x20;
+static constexpr dart::compiler::target::word LinkedHashBase_NextFieldOffset =
+    0x38;
 static constexpr dart::compiler::target::word LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     MarkingStackBlock_pointers_offset = 0x10;
@@ -3346,6 +3354,8 @@ static constexpr dart::compiler::target::word
     LinkedHashBase_type_arguments_offset = 0x8;
 static constexpr dart::compiler::target::word LinkedHashBase_used_data_offset =
     0x14;
+static constexpr dart::compiler::target::word LinkedHashBase_NextFieldOffset =
+    0x20;
 static constexpr dart::compiler::target::word LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     MarkingStackBlock_pointers_offset = 0x10;
@@ -4116,6 +4126,8 @@ static constexpr dart::compiler::target::word
     LinkedHashBase_type_arguments_offset = 0x8;
 static constexpr dart::compiler::target::word LinkedHashBase_used_data_offset =
     0x14;
+static constexpr dart::compiler::target::word LinkedHashBase_NextFieldOffset =
+    0x20;
 static constexpr dart::compiler::target::word LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     MarkingStackBlock_pointers_offset = 0x10;
@@ -4884,6 +4896,8 @@ static constexpr dart::compiler::target::word
     LinkedHashBase_type_arguments_offset = 0x4;
 static constexpr dart::compiler::target::word LinkedHashBase_used_data_offset =
     0x10;
+static constexpr dart::compiler::target::word LinkedHashBase_NextFieldOffset =
+    0x1c;
 static constexpr dart::compiler::target::word LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     MarkingStackBlock_pointers_offset = 0x8;
@@ -5653,6 +5667,8 @@ static constexpr dart::compiler::target::word
     LinkedHashBase_type_arguments_offset = 0x8;
 static constexpr dart::compiler::target::word LinkedHashBase_used_data_offset =
     0x20;
+static constexpr dart::compiler::target::word LinkedHashBase_NextFieldOffset =
+    0x38;
 static constexpr dart::compiler::target::word LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     MarkingStackBlock_pointers_offset = 0x10;
@@ -6414,6 +6430,8 @@ static constexpr dart::compiler::target::word
     LinkedHashBase_type_arguments_offset = 0x4;
 static constexpr dart::compiler::target::word LinkedHashBase_used_data_offset =
     0x10;
+static constexpr dart::compiler::target::word LinkedHashBase_NextFieldOffset =
+    0x1c;
 static constexpr dart::compiler::target::word LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     MarkingStackBlock_pointers_offset = 0x8;
@@ -7174,6 +7192,8 @@ static constexpr dart::compiler::target::word
     LinkedHashBase_type_arguments_offset = 0x8;
 static constexpr dart::compiler::target::word LinkedHashBase_used_data_offset =
     0x20;
+static constexpr dart::compiler::target::word LinkedHashBase_NextFieldOffset =
+    0x38;
 static constexpr dart::compiler::target::word LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     MarkingStackBlock_pointers_offset = 0x10;
@@ -7933,6 +7953,8 @@ static constexpr dart::compiler::target::word
     LinkedHashBase_type_arguments_offset = 0x4;
 static constexpr dart::compiler::target::word LinkedHashBase_used_data_offset =
     0x10;
+static constexpr dart::compiler::target::word LinkedHashBase_NextFieldOffset =
+    0x1c;
 static constexpr dart::compiler::target::word LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     MarkingStackBlock_pointers_offset = 0x8;
@@ -8692,6 +8714,8 @@ static constexpr dart::compiler::target::word
     LinkedHashBase_type_arguments_offset = 0x8;
 static constexpr dart::compiler::target::word LinkedHashBase_used_data_offset =
     0x20;
+static constexpr dart::compiler::target::word LinkedHashBase_NextFieldOffset =
+    0x38;
 static constexpr dart::compiler::target::word LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     MarkingStackBlock_pointers_offset = 0x10;
@@ -9457,6 +9481,8 @@ static constexpr dart::compiler::target::word
     LinkedHashBase_type_arguments_offset = 0x8;
 static constexpr dart::compiler::target::word LinkedHashBase_used_data_offset =
     0x14;
+static constexpr dart::compiler::target::word LinkedHashBase_NextFieldOffset =
+    0x20;
 static constexpr dart::compiler::target::word LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     MarkingStackBlock_pointers_offset = 0x10;
@@ -10219,6 +10245,8 @@ static constexpr dart::compiler::target::word
     LinkedHashBase_type_arguments_offset = 0x8;
 static constexpr dart::compiler::target::word LinkedHashBase_used_data_offset =
     0x14;
+static constexpr dart::compiler::target::word LinkedHashBase_NextFieldOffset =
+    0x20;
 static constexpr dart::compiler::target::word LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     MarkingStackBlock_pointers_offset = 0x10;
@@ -10979,6 +11007,8 @@ static constexpr dart::compiler::target::word
     LinkedHashBase_type_arguments_offset = 0x4;
 static constexpr dart::compiler::target::word LinkedHashBase_used_data_offset =
     0x10;
+static constexpr dart::compiler::target::word LinkedHashBase_NextFieldOffset =
+    0x1c;
 static constexpr dart::compiler::target::word LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     MarkingStackBlock_pointers_offset = 0x8;
@@ -11740,6 +11770,8 @@ static constexpr dart::compiler::target::word
     LinkedHashBase_type_arguments_offset = 0x8;
 static constexpr dart::compiler::target::word LinkedHashBase_used_data_offset =
     0x20;
+static constexpr dart::compiler::target::word LinkedHashBase_NextFieldOffset =
+    0x38;
 static constexpr dart::compiler::target::word LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     MarkingStackBlock_pointers_offset = 0x10;
@@ -12532,6 +12564,8 @@ static constexpr dart::compiler::target::word
     AOT_LinkedHashBase_type_arguments_offset = 0x4;
 static constexpr dart::compiler::target::word
     AOT_LinkedHashBase_used_data_offset = 0x10;
+static constexpr dart::compiler::target::word
+    AOT_LinkedHashBase_NextFieldOffset = 0x1c;
 static constexpr dart::compiler::target::word AOT_LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     AOT_MarkingStackBlock_pointers_offset = 0x8;
@@ -13383,6 +13417,8 @@ static constexpr dart::compiler::target::word
     AOT_LinkedHashBase_type_arguments_offset = 0x8;
 static constexpr dart::compiler::target::word
     AOT_LinkedHashBase_used_data_offset = 0x20;
+static constexpr dart::compiler::target::word
+    AOT_LinkedHashBase_NextFieldOffset = 0x38;
 static constexpr dart::compiler::target::word AOT_LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     AOT_MarkingStackBlock_pointers_offset = 0x10;
@@ -14241,6 +14277,8 @@ static constexpr dart::compiler::target::word
     AOT_LinkedHashBase_type_arguments_offset = 0x8;
 static constexpr dart::compiler::target::word
     AOT_LinkedHashBase_used_data_offset = 0x20;
+static constexpr dart::compiler::target::word
+    AOT_LinkedHashBase_NextFieldOffset = 0x38;
 static constexpr dart::compiler::target::word AOT_LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     AOT_MarkingStackBlock_pointers_offset = 0x10;
@@ -15095,6 +15133,8 @@ static constexpr dart::compiler::target::word
     AOT_LinkedHashBase_type_arguments_offset = 0x8;
 static constexpr dart::compiler::target::word
     AOT_LinkedHashBase_used_data_offset = 0x14;
+static constexpr dart::compiler::target::word
+    AOT_LinkedHashBase_NextFieldOffset = 0x20;
 static constexpr dart::compiler::target::word AOT_LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     AOT_MarkingStackBlock_pointers_offset = 0x10;
@@ -15949,6 +15989,8 @@ static constexpr dart::compiler::target::word
     AOT_LinkedHashBase_type_arguments_offset = 0x8;
 static constexpr dart::compiler::target::word
     AOT_LinkedHashBase_used_data_offset = 0x14;
+static constexpr dart::compiler::target::word
+    AOT_LinkedHashBase_NextFieldOffset = 0x20;
 static constexpr dart::compiler::target::word AOT_LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     AOT_MarkingStackBlock_pointers_offset = 0x10;
@@ -16801,6 +16843,8 @@ static constexpr dart::compiler::target::word
     AOT_LinkedHashBase_type_arguments_offset = 0x4;
 static constexpr dart::compiler::target::word
     AOT_LinkedHashBase_used_data_offset = 0x10;
+static constexpr dart::compiler::target::word
+    AOT_LinkedHashBase_NextFieldOffset = 0x1c;
 static constexpr dart::compiler::target::word AOT_LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     AOT_MarkingStackBlock_pointers_offset = 0x8;
@@ -17653,6 +17697,8 @@ static constexpr dart::compiler::target::word
     AOT_LinkedHashBase_type_arguments_offset = 0x8;
 static constexpr dart::compiler::target::word
     AOT_LinkedHashBase_used_data_offset = 0x20;
+static constexpr dart::compiler::target::word
+    AOT_LinkedHashBase_NextFieldOffset = 0x38;
 static constexpr dart::compiler::target::word AOT_LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     AOT_MarkingStackBlock_pointers_offset = 0x10;
@@ -18495,6 +18541,8 @@ static constexpr dart::compiler::target::word
     AOT_LinkedHashBase_type_arguments_offset = 0x4;
 static constexpr dart::compiler::target::word
     AOT_LinkedHashBase_used_data_offset = 0x10;
+static constexpr dart::compiler::target::word
+    AOT_LinkedHashBase_NextFieldOffset = 0x1c;
 static constexpr dart::compiler::target::word AOT_LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     AOT_MarkingStackBlock_pointers_offset = 0x8;
@@ -19337,6 +19385,8 @@ static constexpr dart::compiler::target::word
     AOT_LinkedHashBase_type_arguments_offset = 0x8;
 static constexpr dart::compiler::target::word
     AOT_LinkedHashBase_used_data_offset = 0x20;
+static constexpr dart::compiler::target::word
+    AOT_LinkedHashBase_NextFieldOffset = 0x38;
 static constexpr dart::compiler::target::word AOT_LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     AOT_MarkingStackBlock_pointers_offset = 0x10;
@@ -20186,6 +20236,8 @@ static constexpr dart::compiler::target::word
     AOT_LinkedHashBase_type_arguments_offset = 0x8;
 static constexpr dart::compiler::target::word
     AOT_LinkedHashBase_used_data_offset = 0x20;
+static constexpr dart::compiler::target::word
+    AOT_LinkedHashBase_NextFieldOffset = 0x38;
 static constexpr dart::compiler::target::word AOT_LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     AOT_MarkingStackBlock_pointers_offset = 0x10;
@@ -21031,6 +21083,8 @@ static constexpr dart::compiler::target::word
     AOT_LinkedHashBase_type_arguments_offset = 0x8;
 static constexpr dart::compiler::target::word
     AOT_LinkedHashBase_used_data_offset = 0x14;
+static constexpr dart::compiler::target::word
+    AOT_LinkedHashBase_NextFieldOffset = 0x20;
 static constexpr dart::compiler::target::word AOT_LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     AOT_MarkingStackBlock_pointers_offset = 0x10;
@@ -21876,6 +21930,8 @@ static constexpr dart::compiler::target::word
     AOT_LinkedHashBase_type_arguments_offset = 0x8;
 static constexpr dart::compiler::target::word
     AOT_LinkedHashBase_used_data_offset = 0x14;
+static constexpr dart::compiler::target::word
+    AOT_LinkedHashBase_NextFieldOffset = 0x20;
 static constexpr dart::compiler::target::word AOT_LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     AOT_MarkingStackBlock_pointers_offset = 0x10;
@@ -22719,6 +22775,8 @@ static constexpr dart::compiler::target::word
     AOT_LinkedHashBase_type_arguments_offset = 0x4;
 static constexpr dart::compiler::target::word
     AOT_LinkedHashBase_used_data_offset = 0x10;
+static constexpr dart::compiler::target::word
+    AOT_LinkedHashBase_NextFieldOffset = 0x1c;
 static constexpr dart::compiler::target::word AOT_LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     AOT_MarkingStackBlock_pointers_offset = 0x8;
@@ -23562,6 +23620,8 @@ static constexpr dart::compiler::target::word
     AOT_LinkedHashBase_type_arguments_offset = 0x8;
 static constexpr dart::compiler::target::word
     AOT_LinkedHashBase_used_data_offset = 0x20;
+static constexpr dart::compiler::target::word
+    AOT_LinkedHashBase_NextFieldOffset = 0x38;
 static constexpr dart::compiler::target::word AOT_LocalHandle_ptr_offset = 0x0;
 static constexpr dart::compiler::target::word
     AOT_MarkingStackBlock_pointers_offset = 0x10;

runtime/vm/compiler/runtime_offsets_list.h

@@ -212,6 +212,7 @@
   FIELD(LinkedHashBase, index_offset)                                          \
   FIELD(LinkedHashBase, type_arguments_offset)                                 \
   FIELD(LinkedHashBase, used_data_offset)                                      \
+  FIELD(LinkedHashBase, NextFieldOffset)                                       \
   FIELD(LocalHandle, ptr_offset)                                               \
   FIELD(MarkingStackBlock, pointers_offset)                                    \
   FIELD(MarkingStackBlock, top_offset)                                         \

runtime/vm/object.cc

@@ -646,6 +646,11 @@ void Object::InitVtables() {
     builtin_vtables_[kUnmodifiableByteDataViewCid] = fake_handle.vtable();
   }
 
+  {
+    LinkedHashBase fake_handle;
+    builtin_vtables_[kLinkedHashBaseCid] = fake_handle.vtable();
+  }
+
   {
     Instance fake_handle;
     builtin_vtables_[kByteBufferCid] = fake_handle.vtable();
@@ -2143,6 +2148,18 @@ ErrorPtr Object::Init(IsolateGroup* isolate_group,
 
     ASSERT(!lib.IsNull());
     ASSERT(lib.ptr() == Library::CompactHashLibrary());
+
+    cls = Class::New<LinkedHashBase, RTN::LinkedHashBase>(
+        kLinkedHashBaseCid, isolate_group, /*register_class=*/true,
+        /*is_abstract=*/true);
+    cls.set_type_arguments_field_offset(
+        LinkedHashBase::type_arguments_offset(),
+        RTN::LinkedHashBase::type_arguments_offset());
+    cls.set_is_prefinalized();
+    isolate_group->class_table()->Register(cls);
+    RegisterPrivateClass(cls, Symbols::_LinkedHashBase(), lib);
+    pending_classes.Add(cls);
+
     cls = Class::New<Map, RTN::Map>(isolate_group);
     object_store->set_map_impl_class(cls);
     cls.set_type_arguments_field_offset(Map::type_arguments_offset(),
@@ -2624,6 +2641,10 @@ ErrorPtr Object::Init(IsolateGroup* isolate_group,
         isolate_group);
     object_store->set_growable_object_array_class(cls);
 
+    cls = Class::New<LinkedHashBase, RTN::LinkedHashBase>(
+        kLinkedHashBaseCid, isolate_group, /*register_class=*/true,
+        /*is_abstract=*/true);
+
     cls = Class::New<Map, RTN::Map>(isolate_group);
     object_store->set_map_impl_class(cls);
 

runtime/vm/object.h

@@ -12318,6 +12318,7 @@ class LinkedHashBase : public Instance {
   static intptr_t InstanceSize() {
     return RoundedAllocationSize(sizeof(UntaggedLinkedHashBase));
   }
+  static intptr_t NextFieldOffset() { return sizeof(UntaggedLinkedHashBase); }
 
   static intptr_t type_arguments_offset() {
     return OFFSET_OF(UntaggedLinkedHashBase, type_arguments_);

runtime/vm/symbol_list.h

@@ -349,6 +349,7 @@ namespace dart {
   V(_GrowableListGenerateFactory, "_GrowableList.generate")                    \
   V(_GrowableListLiteralFactory, "_GrowableList._literal")                     \
   V(_GrowableListWithData, "_GrowableList._withData")                          \
+  V(_LinkedHashBase, "_LinkedHashBase")                                        \
   V(_ImmutableList, "_ImmutableList")                                          \
   V(_Int16ArrayFactory, "Int16List.")                                          \
   V(_Int16ArrayView, "_Int16ArrayView")                                        \

sdk/lib/_internal/vm_shared/lib/compact_hash.dart

@@ -109,64 +109,8 @@ void _rehashObjects(List objects) {
   }
 }
 
-// Common interface for [_HashFieldBase] and [_HashVMBase].
+// Corresponds to `UntaggedLinkedHashBase` VM class.
-abstract class _HashAbstractBase {
+abstract class _LinkedHashBase {
-  abstract Uint32List _index;
-
-  abstract int _hashMask;
-
-  abstract List _data;
-
-  abstract int _usedData;
-
-  abstract int _deletedKeys;
-}
-
-abstract class _HashAbstractImmutableBase extends _HashAbstractBase {
-  Uint32List? get _indexNullable;
-}
-
-abstract class _HashFieldBase implements _HashAbstractImmutableBase {
-  // Each occupied entry in _index is a fixed-size integer that encodes a pair:
-  //   [ hash pattern for key | index of entry in _data ]
-  // The hash pattern is based on hashCode, but is guaranteed to be non-zero.
-  // The length of _index is always a power of two, and there is always at
-  // least one unoccupied entry.
-  // NOTE: When maps are deserialized, their _index and _hashMask is regenerated
-  // eagerly by _regenerateIndex.
-  Uint32List? _indexNullable = _uninitializedIndex;
-
-  @pragma("vm:exact-result-type", "dart:typed_data#_Uint32List")
-  @pragma("vm:prefer-inline")
-  @pragma("wasm:prefer-inline")
-  Uint32List get _index => _indexNullable!;
-
-  @pragma("vm:prefer-inline")
-  @pragma("wasm:prefer-inline")
-  void set _index(Uint32List value) => _indexNullable = value;
-
-  // Cached in-place mask for the hash pattern component.
-  int _hashMask = _HashBase._UNINITIALIZED_HASH_MASK;
-
-  // Fixed-length list of keys (set) or key/value at even/odd indices (map).
-  //
-  // Can be either a mutable or immutable list.
-  List _data = _uninitializedData;
-
-  // Length of _data that is used (i.e., keys + values for a map).
-  int _usedData = 0;
-
-  // Number of deleted keys.
-  int _deletedKeys = 0;
-
-  // Note: All fields are initialized in a single constructor so that the VM
-  // recognizes they cannot hold null values. This makes a big (20%) performance
-  // difference on some operations.
-  _HashFieldBase();
-}
-
-// Base class for VM-internal classes; keep in sync with _HashFieldBase.
-abstract class _HashVMBase implements _HashAbstractBase {
   @pragma("vm:recognized", "other")
   @pragma("vm:exact-result-type", "dart:typed_data#_Uint32List")
   @pragma("vm:prefer-inline")
@@ -206,11 +150,18 @@ abstract class _HashVMBase implements _HashAbstractBase {
   @pragma("vm:recognized", "other")
   @pragma("vm:prefer-inline")
   external void set _deletedKeys(int value);
+
+  _LinkedHashBase() {
+    _index = _uninitializedIndex;
+    _hashMask = _HashBase._UNINITIALIZED_HASH_MASK;
+    _data = _uninitializedData;
+    _usedData = 0;
+    _deletedKeys = 0;
+  }
 }
 
-// Base class for immutable VM-internal classes.
+// Base class for immutable sets and maps.
-abstract class _HashVMImmutableBase extends _HashVMBase
+abstract class _LinkedHashImmutableBase extends _LinkedHashBase {
-    implements _HashAbstractImmutableBase {
   // The data is an immutable list rather than a mutable list.
   @pragma("vm:recognized", "other")
   @pragma("vm:exact-result-type", "dart:core#_ImmutableList")
@@ -229,10 +180,13 @@ abstract class _HashVMImmutableBase extends _HashVMBase
   external void set _index(Uint32List value);
 }
 
-// This mixin can be applied to _HashFieldBase or _HashVMBase (for
+// This mixin can be applied to _LinkedHashBase or _LinkedHashImmutableBase.
-// normal and VM-internalized classes, respectively), which provide the
+//
-// actual fields/accessors that this mixin assumes.
+// Note that _LinkedHashImmutableBase overrides certain accessors on
-mixin _HashBase on _HashAbstractBase {
+// _LinkedHashBase to provide behaviors specific to constant maps and sets.
+// We use mixins to copy implementation methods that depend on these accessors
+// and avoid polymorphism in the code.
+mixin _HashBase on _LinkedHashBase {
   // The number of bits used for each component is determined by table size.
   // If initialized, the length of _index is (at least) twice the number of
   // entries in _data, and both are doubled when _data is full. Thus, _index
@@ -378,7 +332,7 @@ external List get _uninitializedData;
 // literals also create instances of this class.
 @pragma("vm:entry-point")
 @pragma('dyn-module:language-impl:callable')
-base class _Map<K, V> extends _HashVMBase
+base class _Map<K, V> extends _LinkedHashBase
     with
         MapMixin<K, V>,
         _HashBase,
@@ -386,13 +340,7 @@ base class _Map<K, V> extends _HashVMBase
         _LinkedHashMapMixin<K, V>
     implements LinkedHashMap<K, V> {
   @pragma('dyn-module:language-impl:callable')
-  _Map() {
+  _Map();
-    _index = _uninitializedIndex;
-    _hashMask = _HashBase._UNINITIALIZED_HASH_MASK;
-    _data = _uninitializedData;
-    _usedData = 0;
-    _deletedKeys = 0;
-  }
 
   void addAll(Map<K, V> other) {
     if (other case final _Map otherBase) {
@@ -409,7 +357,7 @@ base class _Map<K, V> extends _HashVMBase
 // this class for maps constructed from Dart constant maps.
 @pragma("vm:deeply-immutable")
 @pragma("vm:entry-point")
-final class _ConstMap<K, V> extends _HashVMImmutableBase
+final class _ConstMap<K, V> extends _LinkedHashImmutableBase
     with
         MapMixin<K, V>,
         _HashBase,
@@ -430,7 +378,7 @@ external _ConstMap<K, V> createConstMapFromMapOfDeeplyImmutables<K, V>(
 );
 
 mixin _ImmutableLinkedHashMapMixin<K, V>
-    on _LinkedHashMapMixin<K, V>, _HashAbstractImmutableBase {
+    on _LinkedHashMapMixin<K, V>, _LinkedHashImmutableBase {
   bool containsKey(Object? key) {
     if (_indexNullable == null) {
       _createIndex();
@@ -781,7 +729,7 @@ mixin _LinkedHashMapMixin<K, V> on _HashBase, _EqualsAndHashCode {
   Iterable<MapEntry<K, V>> get entries => _CompactEntriesIterable<K, V>(this);
 }
 
-base class CompactLinkedIdentityHashMap<K, V> extends _HashFieldBase
+base class CompactLinkedIdentityHashMap<K, V> extends _LinkedHashBase
     with
         MapMixin<K, V>,
         _HashBase,
@@ -798,7 +746,7 @@ base class CompactLinkedIdentityHashMap<K, V> extends _HashFieldBase
   }
 }
 
-base class CompactLinkedCustomHashMap<K, V> extends _HashFieldBase
+base class CompactLinkedCustomHashMap<K, V> extends _LinkedHashBase
     with
         MapMixin<K, V>,
         _HashBase,
@@ -941,7 +889,7 @@ class _CompactEntriesIterator<K, V> implements Iterator<MapEntry<K, V>> {
 // Does not check for concurrent modification since the table
 // is known to be immutable.
 class _CompactIterableImmutable<E> extends Iterable<E> {
-  // _HashBase with _HashVMImmutableBase.
+  // _HashBase with _LinkedHashImmutableBase.
   final _HashBase _table;
   // dart:core#_ImmutableList (sdk/lib/_internal/vm/lib/array.dart).
   final List _data;
@@ -966,7 +914,7 @@ class _CompactIterableImmutable<E> extends Iterable<E> {
 }
 
 class _CompactIteratorImmutable<E> implements Iterator<E> {
-  // _HashBase with _HashVMImmutableBase.
+  // _HashBase with _LinkedHashImmutableBase.
   final _HashBase _table;
   // dart:core#_ImmutableList (sdk/lib/_internal/vm/lib/array.dart).
   final List _data;
@@ -1172,7 +1120,7 @@ mixin _LinkedHashSetMixin<E> on _HashBase, _EqualsAndHashCode {
 // class.
 @pragma("vm:entry-point")
 @pragma('dyn-module:language-impl:callable')
-base class _Set<E> extends _HashVMBase
+base class _Set<E> extends _LinkedHashBase
     with
         SetMixin<E>,
         _HashBase,
@@ -1180,13 +1128,7 @@ base class _Set<E> extends _HashVMBase
         _LinkedHashSetMixin<E>
     implements LinkedHashSet<E> {
   @pragma('dyn-module:language-impl:callable')
-  _Set() {
+  _Set();
-    _index = _uninitializedIndex;
-    _hashMask = _HashBase._UNINITIALIZED_HASH_MASK;
-    _data = _uninitializedData;
-    _usedData = 0;
-    _deletedKeys = 0;
-  }
 
   void addAll(Iterable<E> other) {
     if (other case final _Set otherBase) {
@@ -1205,7 +1147,7 @@ base class _Set<E> extends _HashVMBase
 }
 
 @pragma("vm:entry-point")
-base class _ConstSet<E> extends _HashVMImmutableBase
+base class _ConstSet<E> extends _LinkedHashImmutableBase
     with
         SetMixin<E>,
         _HashBase,
@@ -1227,7 +1169,7 @@ base class _ConstSet<E> extends _HashVMImmutableBase
 }
 
 mixin _ImmutableLinkedHashSetMixin<E>
-    on Set<E>, _LinkedHashSetMixin<E>, _HashAbstractImmutableBase {
+    on Set<E>, _LinkedHashSetMixin<E>, _LinkedHashImmutableBase {
   E? lookup(Object? key) {
     if (_indexNullable == null) {
       _createIndex();
@@ -1288,7 +1230,7 @@ mixin _ImmutableLinkedHashSetMixin<E>
       _CompactIteratorImmutable<E>(this, _data, _usedData, -1, 1);
 }
 
-base class CompactLinkedIdentityHashSet<E> extends _HashFieldBase
+base class CompactLinkedIdentityHashSet<E> extends _LinkedHashBase
     with
         SetMixin<E>,
         _HashBase,
@@ -1311,7 +1253,7 @@ base class CompactLinkedIdentityHashSet<E> extends _HashFieldBase
   Set<R> cast<R>() => Set.castFrom<E, R>(this, newSet: _newEmpty);
 }
 
-base class CompactLinkedCustomHashSet<E> extends _HashFieldBase
+base class CompactLinkedCustomHashSet<E> extends _LinkedHashBase
     with
         SetMixin<E>,
         _HashBase,