Use a WeakCell in the CallIC type vector.

src/arm/code-stubs-arm.cc

Index: src/arm/code-stubs-arm.cc
diff --git a/src/arm/code-stubs-arm.cc b/src/arm/code-stubs-arm.cc
index 2e585ba53ab94f692a237556918eb67d4ee1b243..0fba239a9f984ef0d74696e41a19064268cfb205 100644
--- a/src/arm/code-stubs-arm.cc
+++ b/src/arm/code-stubs-arm.cc
@@ -916,6 +916,7 @@ void CodeStub::GenerateStubsAheadOfTime(Isolate* isolate) {
   StubFailureTrampolineStub::GenerateAheadOfTime(isolate);
   ArrayConstructorStubBase::GenerateStubsAheadOfTime(isolate);
   CreateAllocationSiteStub::GenerateAheadOfTime(isolate);
+  CreateWeakCellStub::GenerateAheadOfTime(isolate);
   BinaryOpICStub::GenerateAheadOfTime(isolate);
   BinaryOpICWithAllocationSiteStub::GenerateAheadOfTime(isolate);
 }
@@ -2657,9 +2658,29 @@ void CallICStub::Generate(MacroAssembler* masm) {
   // The checks. First, does r1 match the recorded monomorphic target?
   __ add(r4, r2, Operand::PointerOffsetFromSmiKey(r3));
   __ ldr(r4, FieldMemOperand(r4, FixedArray::kHeaderSize));
-  __ cmp(r1, r4);
+
+  // We don't know that we have a weak cell. We might have a private symbol
+  // 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);
+
+  __ ldr(r5, FieldMemOperand(r4, WeakCell::kValueOffset));
+  __ cmp(r1, r5);
   __ b(ne, &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(r1, &extra_checks_or_miss);
+
   __ bind(&have_js_function);
   if (CallAsMethod()) {
     EmitContinueIfStrictOrNative(masm, &cont);
@@ -2735,15 +2756,18 @@ void CallICStub::Generate(MacroAssembler* masm) {
   __ add(r4, r4, Operand(Smi::FromInt(1)));
   __ str(r4, FieldMemOperand(r2, with_types_offset));
 
-  // Store the function.
-  __ add(r4, r2, Operand::PointerOffsetFromSmiKey(r3));
-  __ add(r4, r4, Operand(FixedArray::kHeaderSize - kHeapObjectTag));
-  __ str(r1, MemOperand(r4, 0));
+  // Store the function. Use a stub since we need a frame for allocation.
+  // r2 - vector
+  // r3 - slot
+  // r1 - function
+  {
+    FrameScope scope(masm, StackFrame::INTERNAL);
+    CreateWeakCellStub create_stub(masm->isolate());
+    __ Push(r1);
+    __ CallStub(&create_stub);
+    __ Pop(r1);
+  }
 
-  // Update the write barrier.
-  __ mov(r5, r1);
-  __ RecordWrite(r2, r4, r5, kLRHasNotBeenSaved, kDontSaveFPRegs,
-                 EMIT_REMEMBERED_SET, OMIT_SMI_CHECK);
   __ jmp(&have_js_function);
 
   // We are here because tracing is on or we encountered a MISS case we can't