[ptr-compr] Make IsolateData be the bottleneck for root-relative accesses

Bug: v8:8182
Change-Id: I4dadd9cab071ecd4314c370be5f444e36acb708e
Reviewed-on: https://chromium-review.googlesource.com/c/1297317
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56973}

BUILD.gn

@@ -1905,6 +1905,7 @@ v8_source_set("v8_base") {
     "src/compiler/zone-stats.h",
     "src/constant-pool.cc",
     "src/constant-pool.h",
+    "src/constants-arch.h",
     "src/contexts-inl.h",
     "src/contexts.cc",
     "src/contexts.h",

src/arm/macro-assembler-arm.cc

@@ -1912,10 +1912,8 @@ void MacroAssembler::LoadNativeContextSlot(int index, Register dst) {
 
 
 void TurboAssembler::InitializeRootRegister() {
-  ExternalReference roots_array_start =
+  ExternalReference isolate_root = ExternalReference::isolate_root(isolate());
-      ExternalReference::roots_array_start(isolate());
+  mov(kRootRegister, Operand(isolate_root));
-  mov(kRootRegister, Operand(roots_array_start));
-  add(kRootRegister, kRootRegister, Operand(kRootRegisterBias));
 }
 
 void MacroAssembler::SmiTag(Register reg, SBit s) {

src/arm64/macro-assembler-arm64-inl.h

@@ -1021,10 +1021,8 @@ void TurboAssembler::Uxtw(const Register& rd, const Register& rn) {
 }
 
 void TurboAssembler::InitializeRootRegister() {
-  ExternalReference roots_array_start =
+  ExternalReference isolate_root = ExternalReference::isolate_root(isolate());
-      ExternalReference::roots_array_start(isolate());
+  Mov(kRootRegister, Operand(isolate_root));
-  Mov(kRootRegister, Operand(roots_array_start));
-  Add(kRootRegister, kRootRegister, kRootRegisterBias);
 }
 
 

src/builtins/builtins-wasm-gen.cc

@@ -23,13 +23,13 @@ class WasmBuiltinsAssembler : public CodeStubAssembler {
 
   TNode<Code> LoadBuiltinFromFrame(Builtins::Name id) {
     TNode<Object> instance = LoadInstanceFromFrame();
-    TNode<IntPtrT> roots = UncheckedCast<IntPtrT>(
+    TNode<IntPtrT> isolate_root = UncheckedCast<IntPtrT>(
         Load(MachineType::Pointer(), instance,
-             IntPtrConstant(WasmInstanceObject::kRootsArrayAddressOffset -
+             IntPtrConstant(WasmInstanceObject::kIsolateRootOffset -
                             kHeapObjectTag)));
-    TNode<Code> target = UncheckedCast<Code>(Load(
+    TNode<Code> target = UncheckedCast<Code>(
-        MachineType::TaggedPointer(), roots,
+        Load(MachineType::TaggedPointer(), isolate_root,
-        IntPtrConstant(IsolateData::kBuiltinsTableOffset + id * kPointerSize)));
+             IntPtrConstant(IsolateData::builtin_slot_offset(id))));
     return target;
   }
 

src/code-stub-assembler.cc

@@ -1459,18 +1459,18 @@ TNode<IntPtrT> CodeStubAssembler::LoadAndUntagSmi(Node* base, int index) {
 
 TNode<Int32T> CodeStubAssembler::LoadAndUntagToWord32Root(
     RootIndex root_index) {
-  Node* roots_array_start =
+  Node* isolate_root =
-      ExternalConstant(ExternalReference::roots_array_start(isolate()));
+      ExternalConstant(ExternalReference::isolate_root(isolate()));
-  int offset = static_cast<int>(root_index) * kPointerSize;
+  int offset = IsolateData::root_slot_offset(root_index);
   if (SmiValuesAre32Bits()) {
 #if V8_TARGET_LITTLE_ENDIAN
     offset += kPointerSize / 2;
 #endif
     return UncheckedCast<Int32T>(
-        Load(MachineType::Int32(), roots_array_start, IntPtrConstant(offset)));
+        Load(MachineType::Int32(), isolate_root, IntPtrConstant(offset)));
   } else {
-    return SmiToInt32(Load(MachineType::AnyTagged(), roots_array_start,
+    return SmiToInt32(
-                           IntPtrConstant(offset)));
+        Load(MachineType::AnyTagged(), isolate_root, IntPtrConstant(offset)));
   }
 }
 

src/compiler/code-assembler.cc

@@ -994,11 +994,11 @@ TNode<Object> CodeAssembler::LoadRoot(RootIndex root_index) {
   // TODO(jgruber): In theory we could generate better code for this by
   // letting the macro assembler decide how to load from the roots list. In most
   // cases, it would boil down to loading from a fixed kRootRegister offset.
-  Node* roots_array_start =
+  Node* isolate_root =
-      ExternalConstant(ExternalReference::roots_array_start(isolate()));
+      ExternalConstant(ExternalReference::isolate_root(isolate()));
-  size_t offset = static_cast<size_t>(root_index) * kPointerSize;
+  int offset = IsolateData::root_slot_offset(root_index);
-  return UncheckedCast<Object>(Load(MachineType::AnyTagged(), roots_array_start,
+  return UncheckedCast<Object>(
-                                    IntPtrConstant(offset)));
+      Load(MachineType::AnyTagged(), isolate_root, IntPtrConstant(offset)));
 }
 
 Node* CodeAssembler::Store(Node* base, Node* value) {
@@ -1058,10 +1058,10 @@ Node* CodeAssembler::AtomicCompareExchange(MachineType type, Node* base,
 
 Node* CodeAssembler::StoreRoot(RootIndex root_index, Node* value) {
   DCHECK(!RootsTable::IsImmortalImmovable(root_index));
-  Node* roots_array_start =
+  Node* isolate_root =
-      ExternalConstant(ExternalReference::roots_array_start(isolate()));
+      ExternalConstant(ExternalReference::isolate_root(isolate()));
-  size_t offset = static_cast<size_t>(root_index) * kPointerSize;
+  int offset = IsolateData::root_slot_offset(root_index);
-  return StoreNoWriteBarrier(MachineRepresentation::kTagged, roots_array_start,
+  return StoreNoWriteBarrier(MachineRepresentation::kTagged, isolate_root,
                              IntPtrConstant(offset), value);
 }
 

src/compiler/ia32/code-generator-ia32.cc

@@ -682,8 +682,7 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
         __ push(eax);
         frame_access_state()->IncreaseSPDelta(1);
         Operand virtual_call_target_register(
-            kRootRegister,
+            kRootRegister, IsolateData::virtual_call_target_register_offset());
-            IsolateData::kVirtualCallTargetRegisterOffset - kRootRegisterBias);
         __ mov(eax, i.InputOperand(0));
         __ add(eax, Immediate(Code::kHeaderSize - kHeapObjectTag));
         __ mov(virtual_call_target_register, eax);

src/compiler/wasm-compiler.cc

@@ -2998,10 +2998,10 @@ Node* WasmGraphBuilder::CurrentMemoryPages() {
 
 Node* WasmGraphBuilder::BuildLoadBuiltinFromInstance(int builtin_index) {
   DCHECK(Builtins::IsBuiltinId(builtin_index));
-  Node* roots =
+  Node* isolate_root =
-      LOAD_INSTANCE_FIELD(RootsArrayAddress, MachineType::TaggedPointer());
+      LOAD_INSTANCE_FIELD(IsolateRoot, MachineType::TaggedPointer());
-  return LOAD_TAGGED_POINTER(
+  return LOAD_TAGGED_POINTER(isolate_root,
-      roots, IsolateData::kBuiltinsTableOffset + builtin_index * kPointerSize);
+                             IsolateData::builtin_slot_offset(builtin_index));
 }
 
 // Only call this function for code which is not reused across instantiations,

src/constants-arch.h

@@ -0,0 +1,28 @@
+// Copyright 2018 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef V8_CONSTANTS_ARCH_H_
+#define V8_CONSTANTS_ARCH_H_
+
+#if V8_TARGET_ARCH_ARM
+#include "src/arm/constants-arm.h"  // NOLINT
+#elif V8_TARGET_ARCH_ARM64
+#include "src/arm64/constants-arm64.h"  // NOLINT
+#elif V8_TARGET_ARCH_IA32
+#include "src/ia32/constants-ia32.h"  // NOLINT
+#elif V8_TARGET_ARCH_MIPS
+#include "src/mips/constants-mips.h"  // NOLINT
+#elif V8_TARGET_ARCH_MIPS64
+#include "src/mips64/constants-mips64.h"  // NOLINT
+#elif V8_TARGET_ARCH_PPC
+#include "src/ppc/constants-ppc.h"  // NOLINT
+#elif V8_TARGET_ARCH_S390
+#include "src/s390/constants-s390.h"  // NOLINT
+#elif V8_TARGET_ARCH_X64
+#include "src/x64/constants-x64.h"  // NOLINT
+#else
+#error Unsupported target architecture.
+#endif
+
+#endif  // V8_CONSTANTS_ARCH_H_

src/deoptimizer.cc

@@ -815,12 +815,9 @@ void Deoptimizer::DoComputeOutputFrames() {
   constexpr bool kShouldInitializeRootRegister = true;
 #endif
   if (kShouldInitializeRootRegister) {
-    Address root_pointer =
-        reinterpret_cast<Address>(isolate()->roots_array_start()) +
-        kRootRegisterBias;
     FrameDescription* topmost = output_[count - 1];
     topmost->GetRegisterValues()->SetRegister(kRootRegister.code(),
-                                              root_pointer);
+                                              isolate()->isolate_root());
   }
 
   // Print some helpful diagnostic information.

src/disasm.h

@@ -24,8 +24,8 @@ class NameConverter {
   virtual const char* NameOfConstant(byte* addr) const;
   virtual const char* NameInCode(byte* addr) const;
 
-  // Given a root-relative offset, returns either a name or nullptr if none is
+  // Given a root-register-relative offset, returns either a name or nullptr if
-  // found.
+  // none is found.
   // TODO(jgruber,v8:7989): This is a temporary solution until we can preserve
   // code comments through snapshotting.
   virtual const char* RootRelativeName(int offset) const { UNREACHABLE(); }

src/disassembler.cc

@@ -61,13 +61,12 @@ void V8NameConverter::InitExternalRefsCache() const {
 
   base::AddressRegion addressable_region =
       isolate_->root_register_addressable_region();
-  Address roots_start =
+  Address isolate_root = isolate_->isolate_root();
-      reinterpret_cast<Address>(isolate_->roots_array_start());
 
   for (uint32_t i = 0; i < external_reference_table->size(); i++) {
     Address address = external_reference_table->address(i);
     if (addressable_region.contains(address)) {
-      int offset = static_cast<int>(address - roots_start);
+      int offset = static_cast<int>(address - isolate_root);
       const char* name = external_reference_table->name(i);
       directly_accessed_external_refs_.insert({offset, name});
     }
@@ -117,15 +116,15 @@ const char* V8NameConverter::NameInCode(byte* addr) const {
 const char* V8NameConverter::RootRelativeName(int offset) const {
   if (isolate_ == nullptr) return nullptr;
 
-  const int kRootsStart = IsolateData::kRootsTableOffset;
+  const int kRootsTableStart = IsolateData::roots_table_offset();
-  const int kRootsEnd = IsolateData::kRootsTableEndOffset;
+  const unsigned kRootsTableSize = sizeof(RootsTable);
-  const int kExtRefsStart = IsolateData::kExternalReferenceTableOffset;
+  const int kExtRefsTableStart = IsolateData::external_reference_table_offset();
-  const int kExtRefsEnd = IsolateData::kExternalReferenceTableEndOffset;
+  const unsigned kExtRefsTableSize = ExternalReferenceTable::SizeInBytes();
-  const int kBuiltinsStart = IsolateData::kBuiltinsTableOffset;
+  const int kBuiltinsTableStart = IsolateData::builtins_table_offset();
-  const int kBuiltinsEnd = IsolateData::kBuiltinsTableEndOffset;
+  const unsigned kBuiltinsTableSize = Builtins::builtin_count * kPointerSize;
 
-  if (kRootsStart <= offset && offset < kRootsEnd) {
+  if (static_cast<unsigned>(offset - kRootsTableStart) < kRootsTableSize) {
-    uint32_t offset_in_roots_table = offset - kRootsStart;
+    uint32_t offset_in_roots_table = offset - kRootsTableStart;
 
     // Fail safe in the unlikely case of an arbitrary root-relative offset.
     if (offset_in_roots_table % kPointerSize != 0) return nullptr;
@@ -141,8 +140,9 @@ const char* V8NameConverter::RootRelativeName(int offset) const {
     SNPrintF(v8_buffer_, "root (%s)", obj_name.get());
     return v8_buffer_.start();
 
-  } else if (kExtRefsStart <= offset && offset < kExtRefsEnd) {
+  } else if (static_cast<unsigned>(offset - kExtRefsTableStart) <
-    uint32_t offset_in_extref_table = offset - kExtRefsStart;
+             kExtRefsTableSize) {
+    uint32_t offset_in_extref_table = offset - kExtRefsTableStart;
 
     // Fail safe in the unlikely case of an arbitrary root-relative offset.
     if (offset_in_extref_table % ExternalReferenceTable::EntrySize() != 0) {
@@ -159,8 +159,9 @@ const char* V8NameConverter::RootRelativeName(int offset) const {
                  offset_in_extref_table));
     return v8_buffer_.start();
 
-  } else if (kBuiltinsStart <= offset && offset < kBuiltinsEnd) {
+  } else if (static_cast<unsigned>(offset - kBuiltinsTableStart) <
-    uint32_t offset_in_builtins_table = (offset - kBuiltinsStart);
+             kBuiltinsTableSize) {
+    uint32_t offset_in_builtins_table = (offset - kBuiltinsTableStart);
 
     Builtins::Name builtin_id =
         static_cast<Builtins::Name>(offset_in_builtins_table / kPointerSize);

src/external-reference.cc

@@ -383,8 +383,8 @@ ExternalReference ExternalReference::log_leave_external_function() {
   return ExternalReference(Redirect(FUNCTION_ADDR(Logger::LeaveExternal)));
 }
 
-ExternalReference ExternalReference::roots_array_start(Isolate* isolate) {
+ExternalReference ExternalReference::isolate_root(Isolate* isolate) {
-  return ExternalReference(isolate->roots_array_start());
+  return ExternalReference(isolate->isolate_root());
 }
 
 ExternalReference ExternalReference::allocation_sites_list_address(

src/external-reference.h

@@ -32,7 +32,7 @@ class StatsCounter;
   V(date_cache_stamp, "date_cache_stamp")                                      \
   V(stress_deopt_count, "Isolate::stress_deopt_count_address()")               \
   V(force_slow_path, "Isolate::force_slow_path_address()")                     \
-  V(roots_array_start, "Heap::roots_array_start()")                            \
+  V(isolate_root, "Isolate::isolate_root()")                                   \
   V(allocation_sites_list_address, "Heap::allocation_sites_list_address()")    \
   V(address_of_stack_limit, "StackGuard::address_of_jslimit()")                \
   V(address_of_real_stack_limit, "StackGuard::address_of_real_jslimit()")      \

src/ia32/macro-assembler-ia32.cc

@@ -50,10 +50,8 @@ void TurboAssembler::InitializeRootRegister() {
   // removed.
   if (!FLAG_embedded_builtins) return;
 
-  ExternalReference roots_array_start =
+  ExternalReference isolate_root = ExternalReference::isolate_root(isolate());
-      ExternalReference::roots_array_start(isolate());
+  Move(kRootRegister, Immediate(isolate_root));
-  Move(kRootRegister, Immediate(roots_array_start));
-  add(kRootRegister, Immediate(kRootRegisterBias));
 }
 
 void TurboAssembler::VerifyRootRegister() {
@@ -62,8 +60,7 @@ void TurboAssembler::VerifyRootRegister() {
   DCHECK(FLAG_embedded_builtins);
 
   Label root_register_ok;
-  cmp(Operand(kRootRegister,
+  cmp(Operand(kRootRegister, IsolateData::magic_number_offset()),
-              IsolateData::kMagicNumberOffset - kRootRegisterBias),
       Immediate(IsolateData::kRootRegisterSentinel));
   j(equal, &root_register_ok);
   int3();
@@ -89,12 +86,10 @@ void TurboAssembler::LoadRoot(Register destination, RootIndex index) {
       return;
     }
   }
-  ExternalReference roots_array_start =
+  ExternalReference isolate_root = ExternalReference::isolate_root(isolate());
-      ExternalReference::roots_array_start(isolate());
-  mov(destination, Immediate(static_cast<int>(index)));
   lea(destination,
-      Operand(destination, times_pointer_size, roots_array_start.address(),
+      Operand(isolate_root.address(), RelocInfo::EXTERNAL_REFERENCE));
-              RelocInfo::EXTERNAL_REFERENCE));
+  mov(destination, Operand(destination, RootRegisterOffsetForRootIndex(index)));
 }
 
 void TurboAssembler::CompareRoot(Register with, Register scratch,
@@ -105,11 +100,9 @@ void TurboAssembler::CompareRoot(Register with, Register scratch,
     return;
   }
 #endif  // V8_EMBEDDED_BUILTINS
-  ExternalReference roots_array_start =
+  ExternalReference isolate_root = ExternalReference::isolate_root(isolate());
-      ExternalReference::roots_array_start(isolate());
+  lea(scratch, Operand(isolate_root.address(), RelocInfo::EXTERNAL_REFERENCE));
-  mov(scratch, Immediate(static_cast<int>(index)));
+  cmp(with, Operand(scratch, RootRegisterOffsetForRootIndex(index)));
-  cmp(with, Operand(scratch, times_pointer_size, roots_array_start.address(),
-                    RelocInfo::EXTERNAL_REFERENCE));
 }
 
 void TurboAssembler::CompareRoot(Register with, RootIndex index) {

src/isolate-data.h

@@ -6,6 +6,7 @@
 #define V8_ISOLATE_DATA_H_
 
 #include "src/builtins/builtins.h"
+#include "src/constants-arch.h"
 #include "src/external-reference-table.h"
 #include "src/roots.h"
 #include "src/utils.h"
@@ -26,26 +27,52 @@ class IsolateData final {
  public:
   IsolateData() = default;
 
-// Layout description.
+  // The value of the kRootRegister.
-#define FIELDS(V)                                                         \
+  Address isolate_root() const {
-  /* roots_ */                                                            \
+    return reinterpret_cast<Address>(this) + kIsolateRootBias;
-  V(kRootsTableOffset, RootsTable::kEntriesCount* kPointerSize)           \
+  }
-  V(kRootsTableEndOffset, 0)                                              \
-  /* external_reference_table_ */                                         \
-  V(kExternalReferenceTableOffset, ExternalReferenceTable::SizeInBytes()) \
-  V(kExternalReferenceTableEndOffset, 0)                                  \
-  /* builtins_ */                                                         \
-  V(kBuiltinsTableOffset, Builtins::builtin_count* kPointerSize)          \
-  V(kBuiltinsTableEndOffset, 0)                                           \
-  /* magic_number_ */                                                     \
-  V(kMagicNumberOffset, kIntptrSize)                                      \
-  /* virtual_call_target_register_ */                                     \
-  V(kVirtualCallTargetRegisterOffset, kPointerSize)                       \
-  /* Total size. */                                                       \
-  V(kSize, 0)
 
-  DEFINE_FIELD_OFFSET_CONSTANTS(0, FIELDS)
+  // Root-register-relative offset of the roots table.
-#undef FIELDS
+  static constexpr int roots_table_offset() {
+    return kRootsTableOffset - kIsolateRootBias;
+  }
+
+  // Root-register-relative offset of the given root table entry.
+  static constexpr int root_slot_offset(RootIndex root_index) {
+    return roots_table_offset() + RootsTable::offset_of(root_index);
+  }
+
+  // Root-register-relative offset of the external reference table.
+  static constexpr int external_reference_table_offset() {
+    return kExternalReferenceTableOffset - kIsolateRootBias;
+  }
+
+  // Root-register-relative offset of the builtins table.
+  static constexpr int builtins_table_offset() {
+    return kBuiltinsTableOffset - kIsolateRootBias;
+  }
+
+  // Root-register-relative offset of the given builtin table entry.
+  // TODO(ishell): remove in favour of typified id version.
+  static int builtin_slot_offset(int builtin_index) {
+    DCHECK(Builtins::IsBuiltinId(builtin_index));
+    return builtins_table_offset() + builtin_index * kPointerSize;
+  }
+
+  // Root-register-relative offset of the builtin table entry.
+  static int builtin_slot_offset(Builtins::Name id) {
+    return builtins_table_offset() + id * kPointerSize;
+  }
+
+  // Root-register-relative offset of the magic number value.
+  static constexpr int magic_number_offset() {
+    return kMagicNumberOffset - kIsolateRootBias;
+  }
+
+  // Root-register-relative offset of the virtual call target register value.
+  static constexpr int virtual_call_target_register_offset() {
+    return kVirtualCallTargetRegisterOffset - kIsolateRootBias;
+  }
 
   // Returns true if this address points to data stored in this instance.
   // If it's the case then the value can be accessed indirectly through the
@@ -70,6 +97,21 @@ class IsolateData final {
   static constexpr intptr_t kRootRegisterSentinel = 0xcafeca11;
 
  private:
+  static constexpr intptr_t kIsolateRootBias = kRootRegisterBias;
+
+// Static layout definition.
+#define FIELDS(V)                                                         \
+  V(kRootsTableOffset, RootsTable::kEntriesCount* kPointerSize)           \
+  V(kExternalReferenceTableOffset, ExternalReferenceTable::SizeInBytes()) \
+  V(kBuiltinsTableOffset, Builtins::builtin_count* kPointerSize)          \
+  V(kMagicNumberOffset, kIntptrSize)                                      \
+  V(kVirtualCallTargetRegisterOffset, kPointerSize)                       \
+  /* Total size. */                                                       \
+  V(kSize, 0)
+
+  DEFINE_FIELD_OFFSET_CONSTANTS(0, FIELDS)
+#undef FIELDS
+
   RootsTable roots_;
 
   ExternalReferenceTable external_reference_table_;

src/isolate.h

@@ -1002,10 +1002,12 @@ class Isolate : private HiddenFactory {
   const IsolateData* isolate_data() const { return heap_.isolate_data(); }
   IsolateData* isolate_data() { return heap_.isolate_data(); }
 
-  RootsTable& roots_table() { return isolate_data()->roots(); }
+  // Generated code can embed this address to get access to the isolate-specific
+  // data (for example, roots, external references, builtins, etc.).
+  // The kRootRegister is set to this value.
+  Address isolate_root() const { return isolate_data()->isolate_root(); }
 
-  // Generated code can embed this address to get access to the roots.
+  RootsTable& roots_table() { return isolate_data()->roots(); }
-  Object** roots_array_start() { return roots_table().roots_; }
 
   // kRootRegister may be used to address any location that falls into this
   // region. Fields outside this region are not guaranteed to live at a static

src/mips/macro-assembler-mips.h

@@ -136,10 +136,8 @@ class V8_EXPORT_PRIVATE TurboAssembler : public TurboAssemblerBase {
   void Prologue();
 
   void InitializeRootRegister() {
-    ExternalReference roots_array_start =
+    ExternalReference isolate_root = ExternalReference::isolate_root(isolate());
-        ExternalReference::roots_array_start(isolate());
+    li(kRootRegister, Operand(isolate_root));
-    li(kRootRegister, Operand(roots_array_start));
-    Addu(kRootRegister, kRootRegister, kRootRegisterBias);
   }
 
   // Jump unconditionally to given label.

src/mips64/macro-assembler-mips64.h

@@ -158,10 +158,8 @@ class V8_EXPORT_PRIVATE TurboAssembler : public TurboAssemblerBase {
   void Prologue();
 
   void InitializeRootRegister() {
-    ExternalReference roots_array_start =
+    ExternalReference isolate_root = ExternalReference::isolate_root(isolate());
-        ExternalReference::roots_array_start(isolate());
+    li(kRootRegister, Operand(isolate_root));
-    li(kRootRegister, Operand(roots_array_start));
-    daddiu(kRootRegister, kRootRegister, kRootRegisterBias);
   }
 
   // Jump unconditionally to given label.

src/objects.h

@@ -17,6 +17,7 @@
 #include "src/base/flags.h"
 #include "src/base/logging.h"
 #include "src/checks.h"
+#include "src/constants-arch.h"
 #include "src/elements-kind.h"
 #include "src/field-index.h"
 #include "src/flags.h"
@@ -26,19 +27,6 @@
 #include "src/roots.h"
 #include "src/utils.h"
 
-#if V8_TARGET_ARCH_ARM
-#include "src/arm/constants-arm.h"  // NOLINT
-#elif V8_TARGET_ARCH_ARM64
-#include "src/arm64/constants-arm64.h"  // NOLINT
-#elif V8_TARGET_ARCH_MIPS
-#include "src/mips/constants-mips.h"  // NOLINT
-#elif V8_TARGET_ARCH_MIPS64
-#include "src/mips64/constants-mips64.h"  // NOLINT
-#elif V8_TARGET_ARCH_PPC
-#include "src/ppc/constants-ppc.h"  // NOLINT
-#elif V8_TARGET_ARCH_S390
-#include "src/s390/constants-s390.h"  // NOLINT
-#endif
 
 // Has to be the last include (doesn't have include guards):
 #include "src/objects/object-macros.h"

src/ppc/macro-assembler-ppc.h

@@ -168,10 +168,8 @@ class V8_EXPORT_PRIVATE TurboAssembler : public TurboAssemblerBase {
   static int ActivationFrameAlignment();
 
   void InitializeRootRegister() {
-    ExternalReference roots_array_start =
+    ExternalReference isolate_root = ExternalReference::isolate_root(isolate());
-        ExternalReference::roots_array_start(isolate());
+    mov(kRootRegister, Operand(isolate_root));
-    mov(kRootRegister, Operand(roots_array_start));
-    addi(kRootRegister, kRootRegister, Operand(kRootRegisterBias));
   }
 
   // These exist to provide portability between 32 and 64bit

src/roots.h

@@ -420,6 +420,10 @@ class RootsTable {
     return root_names_[index];
   }
 
+  static constexpr int offset_of(RootIndex root_index) {
+    return static_cast<int>(root_index) * kPointerSize;
+  }
+
   static RootIndex RootIndexForFixedTypedArray(ExternalArrayType array_type);
   static RootIndex RootIndexForFixedTypedArray(ElementsKind elements_kind);
   static RootIndex RootIndexForEmptyFixedTypedArray(ElementsKind elements_kind);

src/s390/macro-assembler-s390.h

@@ -648,10 +648,8 @@ class V8_EXPORT_PRIVATE TurboAssembler : public TurboAssemblerBase {
   void RestoreFrameStateForTailCall();
 
   void InitializeRootRegister() {
-    ExternalReference roots_array_start =
+    ExternalReference isolate_root = ExternalReference::isolate_root(isolate());
-        ExternalReference::roots_array_start(isolate());
+    mov(kRootRegister, Operand(isolate_root));
-    mov(kRootRegister, Operand(roots_array_start));
-    AddP(kRootRegister, kRootRegister, Operand(kRootRegisterBias));
   }
 
   // If the value is a NaN, canonicalize the value else, do nothing.

src/turbo-assembler.cc

@@ -81,22 +81,19 @@ void TurboAssemblerBase::IndirectLoadExternalReference(
 // static
 int32_t TurboAssemblerBase::RootRegisterOffsetForRootIndex(
     RootIndex root_index) {
-  return (static_cast<int32_t>(root_index) << kPointerSizeLog2) -
+  return IsolateData::root_slot_offset(root_index);
-         kRootRegisterBias;
 }
 
 // static
 int32_t TurboAssemblerBase::RootRegisterOffsetForBuiltinIndex(
     int builtin_index) {
-  return IsolateData::kBuiltinsTableOffset - kRootRegisterBias +
+  return IsolateData::builtin_slot_offset(builtin_index);
-         builtin_index * kPointerSize;
 }
 
 // static
 intptr_t TurboAssemblerBase::RootRegisterOffsetForExternalReference(
     Isolate* isolate, const ExternalReference& reference) {
-  return static_cast<intptr_t>(reference.address()) - kRootRegisterBias -
+  return static_cast<intptr_t>(reference.address() - isolate->isolate_root());
-         reinterpret_cast<intptr_t>(isolate->roots_array_start());
 }
 
 // static
@@ -108,7 +105,7 @@ int32_t TurboAssemblerBase::RootRegisterOffsetForExternalReferenceTableEntry(
   ExternalReferenceEncoder::Value v = encoder.Encode(reference.address());
   CHECK(!v.is_from_api());
 
-  return IsolateData::kExternalReferenceTableOffset - kRootRegisterBias +
+  return IsolateData::external_reference_table_offset() +
          ExternalReferenceTable::OffsetOfEntry(v.index());
 }
 

src/wasm/wasm-objects-inl.h

@@ -142,8 +142,8 @@ void WasmGlobalObject::SetF64(double value) {
 PRIMITIVE_ACCESSORS(WasmInstanceObject, memory_start, byte*, kMemoryStartOffset)
 PRIMITIVE_ACCESSORS(WasmInstanceObject, memory_size, size_t, kMemorySizeOffset)
 PRIMITIVE_ACCESSORS(WasmInstanceObject, memory_mask, size_t, kMemoryMaskOffset)
-PRIMITIVE_ACCESSORS(WasmInstanceObject, roots_array_address, Address,
+PRIMITIVE_ACCESSORS(WasmInstanceObject, isolate_root, Address,
-                    kRootsArrayAddressOffset)
+                    kIsolateRootOffset)
 PRIMITIVE_ACCESSORS(WasmInstanceObject, stack_limit_address, Address,
                     kStackLimitAddressOffset)
 PRIMITIVE_ACCESSORS(WasmInstanceObject, real_stack_limit_address, Address,

src/wasm/wasm-objects.cc

@@ -1282,8 +1282,7 @@ Handle<WasmInstanceObject> WasmInstanceObject::New(
   instance->set_centry_stub(*centry_stub);
 
   instance->SetRawMemory(nullptr, 0);
-  instance->set_roots_array_address(
+  instance->set_isolate_root(isolate->isolate_root());
-      reinterpret_cast<Address>(isolate->roots_array_start()));
   instance->set_stack_limit_address(
       isolate->stack_guard()->address_of_jslimit());
   instance->set_real_stack_limit_address(

src/wasm/wasm-objects.h

@@ -395,7 +395,7 @@ class WasmInstanceObject : public JSObject {
   DECL_PRIMITIVE_ACCESSORS(memory_start, byte*)
   DECL_PRIMITIVE_ACCESSORS(memory_size, size_t)
   DECL_PRIMITIVE_ACCESSORS(memory_mask, size_t)
-  DECL_PRIMITIVE_ACCESSORS(roots_array_address, Address)
+  DECL_PRIMITIVE_ACCESSORS(isolate_root, Address)
   DECL_PRIMITIVE_ACCESSORS(stack_limit_address, Address)
   DECL_PRIMITIVE_ACCESSORS(real_stack_limit_address, Address)
   DECL_PRIMITIVE_ACCESSORS(imported_function_targets, Address*)
@@ -431,7 +431,7 @@ class WasmInstanceObject : public JSObject {
   V(kMemoryStartOffset, kPointerSize)                    /* untagged */ \
   V(kMemorySizeOffset, kSizetSize)                       /* untagged */ \
   V(kMemoryMaskOffset, kSizetSize)                       /* untagged */ \
-  V(kRootsArrayAddressOffset, kPointerSize)              /* untagged */ \
+  V(kIsolateRootOffset, kPointerSize)                    /* untagged */ \
   V(kStackLimitAddressOffset, kPointerSize)              /* untagged */ \
   V(kRealStackLimitAddressOffset, kPointerSize)          /* untagged */ \
   V(kImportedFunctionTargetsOffset, kPointerSize)        /* untagged */ \

src/x64/disasm-x64.cc

@@ -580,7 +580,7 @@ int DisassemblerX64::PrintRightOperandHelper(
                        disp < 0 ? -disp : disp);
         if (rm == i::kRootRegister.code()) {
           // For root-relative accesses, try to append a description.
-          TryAppendRootRelativeName(i::kRootRegisterBias + disp);
+          TryAppendRootRelativeName(disp);
         }
         return (mod == 2) ? 5 : 2;
       }

src/x64/macro-assembler-x64.h

@@ -466,10 +466,8 @@ class V8_EXPORT_PRIVATE TurboAssembler : public TurboAssemblerBase {
   void CallRuntimeWithCEntry(Runtime::FunctionId fid, Register centry);
 
   void InitializeRootRegister() {
-    ExternalReference roots_array_start =
+    ExternalReference isolate_root = ExternalReference::isolate_root(isolate());
-        ExternalReference::roots_array_start(isolate());
+    Move(kRootRegister, isolate_root);
-    Move(kRootRegister, roots_array_start);
-    addp(kRootRegister, Immediate(kRootRegisterBias));
   }
 
   void SaveRegisters(RegList registers);

test/unittests/compiler/arm64/instruction-selector-arm64-unittest.cc

@@ -4542,9 +4542,8 @@ TEST_F(InstructionSelectorTest, ExternalReferenceLoad1) {
   const int64_t kOffsets[] = {0, 1, 4, INT32_MIN, INT32_MAX};
   TRACED_FOREACH(int64_t, offset, kOffsets) {
     StreamBuilder m(this, MachineType::Int64());
-    ExternalReference reference = bit_cast<ExternalReference>(
+    ExternalReference reference =
-        reinterpret_cast<intptr_t>(isolate()->roots_array_start()) + offset +
+        bit_cast<ExternalReference>(isolate()->isolate_root() + offset);
-        kRootRegisterBias);
     Node* const value =
         m.Load(MachineType::Int64(), m.ExternalConstant(reference));
     m.Return(value);
@@ -4564,9 +4563,8 @@ TEST_F(InstructionSelectorTest, ExternalReferenceLoad2) {
   // Offset too large, we cannot use kMode_Root.
   StreamBuilder m(this, MachineType::Int64());
   int64_t offset = 0x100000000;
-  ExternalReference reference = bit_cast<ExternalReference>(
+  ExternalReference reference =
-      reinterpret_cast<intptr_t>(isolate()->roots_array_start()) + offset +
+      bit_cast<ExternalReference>(isolate()->isolate_root() + offset);
-      kRootRegisterBias);
   Node* const value =
       m.Load(MachineType::Int64(), m.ExternalConstant(reference));
   m.Return(value);