Revert of Revert of [strong] Implement strong mode restrictions on property access

src/ic/mips64/ic-mips64.cc

Index: src/ic/mips64/ic-mips64.cc
diff --git a/src/ic/mips64/ic-mips64.cc b/src/ic/mips64/ic-mips64.cc
index 770fa77808dd5ef7631d3aeefd2d3e051f914d54..cbe9c0db786275fab12e4cdb950bb7f05bb75829 100644
--- a/src/ic/mips64/ic-mips64.cc
+++ b/src/ic/mips64/ic-mips64.cc
@@ -162,7 +162,8 @@
 static void GenerateFastArrayLoad(MacroAssembler* masm, Register receiver,
                                   Register key, Register elements,
                                   Register scratch1, Register scratch2,
-                                  Register result, Label* slow) {
+                                  Register result, Label* slow,
+                                  LanguageMode language_mode) {
   // Register use:
   //
   // receiver - holds the receiver on entry.
@@ -184,7 +185,7 @@
   //
   // scratch2 - used to hold maps, prototypes, and the loaded value.
   Label check_prototypes, check_next_prototype;
-  Label done, in_bounds, return_undefined;
+  Label done, in_bounds, absent;
 
   __ ld(elements, FieldMemOperand(receiver, JSObject::kElementsOffset));
   __ AssertFastElements(elements);
@@ -202,7 +203,7 @@
   __ ld(scratch2, FieldMemOperand(scratch2, Map::kPrototypeOffset));
   // scratch2: current prototype
   __ LoadRoot(at, Heap::kNullValueRootIndex);
-  __ Branch(&return_undefined, eq, scratch2, Operand(at));
+  __ Branch(&absent, eq, scratch2, Operand(at));
   __ ld(elements, FieldMemOperand(scratch2, JSObject::kElementsOffset));
   __ ld(scratch2, FieldMemOperand(scratch2, HeapObject::kMapOffset));
   // elements: elements of current prototype
@@ -217,9 +218,13 @@
   __ Branch(slow, ne, elements, Operand(at));
   __ Branch(&check_next_prototype);
 
-  __ bind(&return_undefined);
-  __ LoadRoot(result, Heap::kUndefinedValueRootIndex);
-  __ Branch(&done);
+  __ bind(&absent);
+  if (is_strong(language_mode)) {
+    __ Branch(slow);
+  } else {
+    __ LoadRoot(result, Heap::kUndefinedValueRootIndex);
+    __ Branch(&done);
+  }
 
   __ bind(&in_bounds);
   // Fast case: Do the load.
@@ -283,7 +288,7 @@
 
   // Dictionary load failed, go slow (but don't miss).
   __ bind(&slow);
-  GenerateRuntimeGetProperty(masm);
+  GenerateSlow(masm);
 }
 
 
@@ -318,7 +323,7 @@
 }
 
 
-void LoadIC::GenerateRuntimeGetProperty(MacroAssembler* masm) {
+void LoadIC::GenerateSlow(MacroAssembler* masm) {
   // The return address is in ra.
 
   __ mov(LoadIC_TempRegister(), LoadDescriptor::ReceiverRegister());
@@ -347,7 +352,7 @@
 }
 
 
-void KeyedLoadIC::GenerateRuntimeGetProperty(MacroAssembler* masm) {
+void KeyedLoadIC::GenerateSlow(MacroAssembler* masm) {
   // The return address is in ra.
 
   __ Push(LoadDescriptor::ReceiverRegister(), LoadDescriptor::NameRegister());
@@ -356,7 +361,8 @@
 }
 
 
-void KeyedLoadIC::GenerateMegamorphic(MacroAssembler* masm) {
+void KeyedLoadIC::GenerateMegamorphic(MacroAssembler* masm,
+                                      LanguageMode language_mode) {
   // The return address is in ra.
   Label slow, check_name, index_smi, index_name, property_array_property;
   Label probe_dictionary, check_number_dictionary;
@@ -380,7 +386,8 @@
   // Check the receiver's map to see if it has fast elements.
   __ CheckFastElements(a0, a3, &check_number_dictionary);
 
-  GenerateFastArrayLoad(masm, receiver, key, a0, a3, a4, v0, &slow);
+  GenerateFastArrayLoad(masm, receiver, key, a0, a3, a4, v0, &slow,
+                        language_mode);
   __ IncrementCounter(isolate->counters()->keyed_load_generic_smi(), 1, a4, a3);
   __ Ret();
 
@@ -401,7 +408,7 @@
   __ bind(&slow);
   __ IncrementCounter(isolate->counters()->keyed_load_generic_slow(), 1, a4,
                       a3);
-  GenerateRuntimeGetProperty(masm);
+  GenerateSlow(masm);
 
   __ bind(&check_name);
   GenerateKeyNameCheck(masm, key, a0, a3, &index_name, &slow);