[stubs] Optimize LoadGlobalViaContextStub and StoreGlobalViaContextStub.

src/arm64/code-stubs-arm64.cc

Index: src/arm64/code-stubs-arm64.cc
diff --git a/src/arm64/code-stubs-arm64.cc b/src/arm64/code-stubs-arm64.cc
index 01189f21212cf18f9694698e0171bb510fca3a49..d0ee80e68c47e1dccd750f7e35c1614e8a5a30e6 100644
--- a/src/arm64/code-stubs-arm64.cc
+++ b/src/arm64/code-stubs-arm64.cc
@@ -5494,6 +5494,153 @@ void InternalArrayConstructorStub::Generate(MacroAssembler* masm) {
 }
 
 
+void LoadGlobalViaContextStub::Generate(MacroAssembler* masm) {
+  Register context = cp;
+  Register result = x0;
+  Register slot = x2;
+  Register name = x3;
+  Label slow_case;
+
+  // Go up the context chain to the script context.
+  for (int i = 0; i < depth(); ++i) {
+    __ Ldr(result, ContextMemOperand(context, Context::PREVIOUS_INDEX));
+    context = result;
+  }
+
+  // Load the PropertyCell value at the specified slot.
+  __ Add(result, context, Operand(slot, LSL, kPointerSizeLog2));
+  __ Ldr(result, ContextMemOperand(result));
+  __ Ldr(result, FieldMemOperand(result, PropertyCell::kValueOffset));
+
+  // If the result is not the_hole, return. Otherwise, handle in the runtime.
+  __ JumpIfRoot(result, Heap::kTheHoleValueRootIndex, &slow_case);
+  __ Ret();
+
+  // Fallback to runtime.
+  __ Bind(&slow_case);
+  __ SmiTag(slot);
+  __ Push(slot, name);
+  __ TailCallRuntime(Runtime::kLoadGlobalViaContext, 2, 1);
+}
+
+
+void StoreGlobalViaContextStub::Generate(MacroAssembler* masm) {
+  Register context = cp;
+  Register value = x0;
+  Register slot = x2;
+  Register name = x3;
+  Register context_temp = x10;
+  Register cell = x10;
+  Register cell_details = x11;
+  Register cell_value = x12;
+  Register cell_value_map = x13;
+  Register value_map = x14;
+  Label fast_heapobject_case, fast_smi_case, slow_case;
+
+  if (FLAG_debug_code) {
+    __ CompareRoot(value, Heap::kTheHoleValueRootIndex);
+    __ Check(ne, kUnexpectedValue);
+    __ AssertName(name);
+  }
+
+  // Go up the context chain to the script context.
+  for (int i = 0; i < depth(); i++) {
+    __ Ldr(context_temp, ContextMemOperand(context, Context::PREVIOUS_INDEX));
+    context = context_temp;
+  }
+
+  // Load the PropertyCell at the specified slot.
+  __ Add(cell, context, Operand(slot, LSL, kPointerSizeLog2));
+  __ Ldr(cell, ContextMemOperand(cell));
+
+  // Load PropertyDetails for the cell (actually only the cell_type and kind).
+  __ Ldr(cell_details,
+         UntagSmiFieldMemOperand(cell, PropertyCell::kDetailsOffset));
+  __ And(cell_details, cell_details,
+         PropertyDetails::PropertyCellTypeField::kMask |
+             PropertyDetails::KindField::kMask);
+
+  // Check if PropertyCell holds mutable data.
+  Label not_mutable_data;
+  __ Cmp(cell_details, PropertyDetails::PropertyCellTypeField::encode(
+                           PropertyCellType::kMutable) |
+                           PropertyDetails::KindField::encode(kData));
+  __ B(ne, &not_mutable_data);
+  __ JumpIfSmi(value, &fast_smi_case);
+  __ Bind(&fast_heapobject_case);
+  __ Str(value, FieldMemOperand(cell, PropertyCell::kValueOffset));
+  // RecordWriteField clobbers the value register, so we copy it before the
+  // call.
+  __ Mov(x11, value);
+  __ RecordWriteField(cell, PropertyCell::kValueOffset, x11, x12,
+                      kLRHasNotBeenSaved, kDontSaveFPRegs, EMIT_REMEMBERED_SET,
+                      OMIT_SMI_CHECK);
+  __ Ret();
+
+  __ Bind(&not_mutable_data);
+  // Check if PropertyCell value matches the new value (relevant for Constant,
+  // ConstantType and Undefined cells).
+  Label not_same_value;
+  __ Ldr(cell_value, FieldMemOperand(cell, PropertyCell::kValueOffset));
+  __ Cmp(cell_value, value);
+  __ B(ne, &not_same_value);
+
+  if (FLAG_debug_code) {
+    Label done;
+    // This can only be true for Constant, ConstantType and Undefined cells,
+    // because we never store the_hole via this stub.
+    __ Cmp(cell_details, PropertyDetails::PropertyCellTypeField::encode(
+                             PropertyCellType::kConstant) |
+                             PropertyDetails::KindField::encode(kData));
+    __ B(eq, &done);
+    __ Cmp(cell_details, PropertyDetails::PropertyCellTypeField::encode(
+                             PropertyCellType::kConstantType) |
+                             PropertyDetails::KindField::encode(kData));
+    __ B(eq, &done);
+    __ Cmp(cell_details, PropertyDetails::PropertyCellTypeField::encode(
+                             PropertyCellType::kUndefined) |
+                             PropertyDetails::KindField::encode(kData));
+    __ Check(eq, kUnexpectedValue);
+    __ Bind(&done);
+  }
+  __ Ret();
+  __ Bind(&not_same_value);
+
+  // Check if PropertyCell contains data with constant type.
+  __ Cmp(cell_details, PropertyDetails::PropertyCellTypeField::encode(
+                           PropertyCellType::kConstantType) |
+                           PropertyDetails::KindField::encode(kData));
+  __ B(ne, &slow_case);
+
+  // Now either both old and new values must be smis or both must be heap
+  // objects with same map.
+  Label value_is_heap_object;
+  __ JumpIfNotSmi(value, &value_is_heap_object);
+  __ JumpIfNotSmi(cell_value, &slow_case);
+  // Old and new values are smis, no need for a write barrier here.
+  __ Bind(&fast_smi_case);
+  __ Str(value, FieldMemOperand(cell, PropertyCell::kValueOffset));
+  __ Ret();
+
+  __ Bind(&value_is_heap_object);
+  __ JumpIfSmi(cell_value, &slow_case);
+
+  __ Ldr(cell_value_map, FieldMemOperand(cell_value, HeapObject::kMapOffset));
+  __ Ldr(value_map, FieldMemOperand(value, HeapObject::kMapOffset));
+  __ Cmp(cell_value_map, value_map);
+  __ B(eq, &fast_heapobject_case);
+
+  // Fall back to the runtime.
+  __ Bind(&slow_case);
+  __ SmiTag(slot);
+  __ Push(slot, name, value);
+  __ TailCallRuntime(is_strict(language_mode())
+                         ? Runtime::kStoreGlobalViaContext_Strict
+                         : Runtime::kStoreGlobalViaContext_Sloppy,
+                     3, 1);
+}
+
+
 // The number of register that CallApiFunctionAndReturn will need to save on
 // the stack. The space for these registers need to be allocated in the
 // ExitFrame before calling CallApiFunctionAndReturn.