[ia32,root] Remove root register verification

Verification has served its purpose now that kRootRegister is fully
supported on ia32.

Bug: v8:6666
Change-Id: I037617bf900f161c221228107c9f1352d4815d87
Reviewed-on: https://chromium-review.googlesource.com/c/1296130Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57666}

src/builtins/ia32/builtins-ia32.cc

@@ -820,8 +820,6 @@ static void AdvanceBytecodeOffsetOrReturn(MacroAssembler* masm,
 void Builtins::Generate_InterpreterEntryTrampoline(MacroAssembler* masm) {
   ProfileEntryHookStub::MaybeCallEntryHook(masm);
 
-  __ VerifyRootRegister();
-
   Register closure = edi;
 
   Register feedback_vector = ecx;
@@ -941,7 +939,6 @@ void Builtins::Generate_InterpreterEntryTrampoline(MacroAssembler* masm) {
   __ mov(
       kJavaScriptCallCodeStartRegister,
       Operand(kInterpreterDispatchTableRegister, ecx, times_pointer_size, 0));
-  __ VerifyRootRegister();
   __ call(kJavaScriptCallCodeStartRegister);
   masm->isolate()->heap()->SetInterpreterEntryReturnPCOffset(masm->pc_offset());
 
@@ -965,7 +962,6 @@ void Builtins::Generate_InterpreterEntryTrampoline(MacroAssembler* masm) {
   __ bind(&do_return);
   // The return value is in eax.
   LeaveInterpreterFrame(masm, edx, ecx);
-  __ VerifyRootRegister();
   __ ret(0);
 }
 

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

@@ -3623,7 +3623,6 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
       break;
     }
     case kIA32StackCheck: {
-      __ VerifyRootRegister();
       __ CompareStackLimit(esp);
       break;
     }

src/flag-definitions.h

@@ -1068,10 +1068,6 @@ DEFINE_VALUE_IMPLICATION(runtime_call_stats, runtime_stats, 1)
 #endif
 DEFINE_BOOL_READONLY(embedded_builtins, V8_EMBEDDED_BUILTINS_BOOL,
                      "Embed builtin code into the binary.")
-// TODO(jgruber,v8:6666): Remove once ia32 has full embedded builtin support.
-DEFINE_BOOL_READONLY(
-    ia32_verify_root_register, false,
-    "Check that the value of the root register was not clobbered.")
 DEFINE_BOOL(profile_deserialization, false,
             "Print the time it takes to deserialize the snapshot.")
 DEFINE_BOOL(serialization_statistics, false,

src/ia32/code-stubs-ia32.cc

@@ -98,8 +98,6 @@ void JSEntryStub::Generate(MacroAssembler* masm) {
 
   __ bind(&exit);
 
-  __ VerifyRootRegister();
-
   // Check if the current stack frame is marked as the outermost JS frame.
   __ pop(edi);
   __ cmp(edi, Immediate(StackFrame::OUTERMOST_JSENTRY_FRAME));

src/ia32/macro-assembler-ia32.cc

@@ -54,19 +54,6 @@ void TurboAssembler::InitializeRootRegister() {
   Move(kRootRegister, Immediate(isolate_root));
 }
 
-void TurboAssembler::VerifyRootRegister() {
-  if (!FLAG_ia32_verify_root_register) return;
-
-  DCHECK(FLAG_embedded_builtins);
-
-  Label root_register_ok;
-  cmp(Operand(kRootRegister, IsolateData::magic_number_offset()),
-      Immediate(IsolateData::kRootRegisterSentinel));
-  j(equal, &root_register_ok);
-  int3();
-  bind(&root_register_ok);
-}
-
 void TurboAssembler::LoadRoot(Register destination, RootIndex index) {
   if (root_array_available()) {
     mov(destination,

src/ia32/macro-assembler-ia32.h

@@ -231,7 +231,6 @@ class V8_EXPORT_PRIVATE TurboAssembler : public TurboAssemblerBase {
   // Root register utility functions.
 
   void InitializeRootRegister();
-  void VerifyRootRegister();
 
   void LoadRoot(Register destination, RootIndex index) override;
 

src/isolate-data.h

@@ -66,11 +66,6 @@ class IsolateData final {
     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;
@@ -94,10 +89,6 @@ class IsolateData final {
 
   Address* builtins() { return builtins_; }
 
-  // For root register verification.
-  // TODO(v8:6666): Remove once the root register is fully supported on ia32.
-  static constexpr intptr_t kRootRegisterSentinel = 0xcafeca11;
-
  private:
 // Static layout definition.
 #define FIELDS(V)                                                         \
@@ -108,7 +99,6 @@ class IsolateData final {
   V(kRootsTableOffset, RootsTable::kEntriesCount* kPointerSize)           \
   V(kExternalReferenceTableOffset, ExternalReferenceTable::SizeInBytes()) \
   V(kBuiltinsTableOffset, Builtins::builtin_count* kPointerSize)          \
-  V(kMagicNumberOffset, kIntptrSize)                                      \
   V(kVirtualCallTargetRegisterOffset, kPointerSize)                       \
   /* This padding aligns IsolateData size by 8 bytes. */                  \
   V(kPaddingOffset,                                                       \
@@ -143,10 +133,6 @@ class IsolateData final {
   // The entries in this array are tagged pointers to Code objects.
   Address builtins_[Builtins::builtin_count] = {};
 
-  // For root register verification.
-  // TODO(v8:6666): Remove once the root register is fully supported on ia32.
-  const intptr_t magic_number_ = kRootRegisterSentinel;
-
   // For isolate-independent calls on ia32.
   // TODO(v8:6666): Remove once wasm supports pc-relative jumps to builtins on
   // ia32 (otherwise the arguments adaptor call runs out of registers).
@@ -183,7 +169,6 @@ void IsolateData::AssertPredictableLayout() {
   STATIC_ASSERT(offsetof(IsolateData, external_reference_table_) ==
                 kExternalReferenceTableOffset);
   STATIC_ASSERT(offsetof(IsolateData, builtins_) == kBuiltinsTableOffset);
-  STATIC_ASSERT(offsetof(IsolateData, magic_number_) == kMagicNumberOffset);
   STATIC_ASSERT(offsetof(IsolateData, virtual_call_target_register_) ==
                 kVirtualCallTargetRegisterOffset);
   STATIC_ASSERT(offsetof(IsolateData, external_memory_) ==