Add map-based read barrier to WeakCell

src/ia32/code-stubs-ia32.cc

 // Copyright 2012 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.
 
 #include "src/v8.h"
 
 #if V8_TARGET_ARCH_IA32
 
 #include "src/base/bits.h"
 #include "src/bootstrapper.h"
@@ skipping 2241 matching lines @@
   // or an AllocationSite, but the memory is safe to examine.
   // AllocationSite::kTransitionInfoOffset - contains a Smi or pointer to
   // FixedArray.
   // WeakCell::kValueOffset - contains a JSFunction or Smi(0)
   // Symbol::kHashFieldSlot - if the low bit is 1, then the hash is not
   // computed, meaning that it can't appear to be a pointer. If the low bit is
   // 0, then hash is computed, but the 0 bit prevents the field from appearing
   // to be a pointer.
   STATIC_ASSERT(WeakCell::kSize >= kPointerSize);
   STATIC_ASSERT(AllocationSite::kTransitionInfoOffset ==
-                    WeakCell::kValueOffset &&
-                WeakCell::kValueOffset == Symbol::kHashFieldSlot);
+                    WeakCell::kValueOffsetDontForgetTheReadBarrier &&
+                AllocationSite::kTransitionInfoOffset ==
+                    Symbol::kHashFieldSlot);
 
-  __ cmp(edi, FieldOperand(ecx, WeakCell::kValueOffset));
+  __ cmp(edi,
+         FieldOperand(ecx, WeakCell::kValueOffsetDontForgetTheReadBarrier));
   __ j(not_equal, &extra_checks_or_miss);
 
   // The compare above could have been a SMI/SMI comparison. Guard against this
   // convincing us that we have a monomorphic JSFunction.
   __ JumpIfSmi(edi, &extra_checks_or_miss);
 
   __ bind(&have_js_function);
   if (CallAsMethod()) {
     EmitContinueIfStrictOrNative(masm, &cont);
 
@@ skipping 1509 matching lines @@
   __ ret(0);
 
   __ bind(&miss);
   GenerateMiss(masm);
 }
 
 
 void CompareICStub::GenerateKnownObjects(MacroAssembler* masm) {
   Label miss;
   Handle<WeakCell> cell = Map::WeakCellForMap(known_map_);
+  // Combine two Smi tests into one with bitwise and.
   __ mov(ecx, edx);
   __ and_(ecx, eax);
   __ JumpIfSmi(ecx, &miss, Label::kNear);
 
-  __ GetWeakValue(edi, cell);
+  __ GetWeakValueNoReadBarrier(edi, cell);
   __ mov(ecx, FieldOperand(eax, HeapObject::kMapOffset));
   __ mov(ebx, FieldOperand(edx, HeapObject::kMapOffset));
   __ cmp(ecx, edi);
   __ j(not_equal, &miss, Label::kNear);
   __ cmp(ebx, edi);
   __ j(not_equal, &miss, Label::kNear);
 
   __ sub(eax, edx);
   __ ret(0);
 
@@ skipping 1288 matching lines @@
                            ApiParameterOperand(2), kStackSpace, nullptr,
                            Operand(ebp, 7 * kPointerSize), NULL);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32