Array constructor expects AllocationSite or undefined as feedback.

src/a64/code-stubs-a64.cc

Index: src/a64/code-stubs-a64.cc
diff --git a/src/a64/code-stubs-a64.cc b/src/a64/code-stubs-a64.cc
index 2996df9b82d6863bb54e67739a22c9ba7415f4c8..fa8d22a873d3edf46deab080fa2e01af566748d5 100644
--- a/src/a64/code-stubs-a64.cc
+++ b/src/a64/code-stubs-a64.cc
@@ -3306,6 +3306,10 @@ void CallFunctionStub::Generate(MacroAssembler* masm) {
 
     if (RecordCallTarget()) {
       GenerateRecordCallTarget(masm, x0, function, cache_cell, slot, x4, x5);
+      // Type information was updated. Because we may call Array, which
+      // expects either undefined or an AllocationSite in ebx we need
+      // to set ebx to undefined.
+      __ LoadRoot(cache_cell, Heap::kUndefinedValueRootIndex);
     }
   }
 
@@ -3410,7 +3414,18 @@ void CallConstructStub::Generate(MacroAssembler* masm) {
                          &slow);
 
   if (RecordCallTarget()) {
+    Label feedback_register_initialized;
     GenerateRecordCallTarget(masm, x0, function, x2, x3, x4, x5);
+
+    // Put the AllocationSite from the feedback vector into x2, or undefined.
+    __ Add(x5, x2, Operand::UntagSmiAndScale(x3, kPointerSizeLog2));
+    __ Ldr(x2, FieldMemOperand(x5, FixedArray::kHeaderSize));
+    __ Ldr(x5, FieldMemOperand(x2, AllocationSite::kMapOffset));
+    __ JumpIfRoot(x5, Heap::kAllocationSiteMapRootIndex,
+                  &feedback_register_initialized);
+    __ LoadRoot(x2, Heap::kUndefinedValueRootIndex);
+    __ bind(&feedback_register_initialized);
+    __ AssertUndefinedOrAllocationSite(x2, x5);
   }
 
   // Jump to the function-specific construct stub.
@@ -5405,17 +5420,12 @@ void ArrayConstructorStub::Generate(MacroAssembler* masm) {
   // ----------- S t a t e -------------
   //  -- x0 : argc (only if argument_count_ == ANY)
   //  -- x1 : constructor
-  //  -- x2 : feedback vector (fixed array or the megamorphic symbol)
-  //  -- x3 : slot index (if x2 is fixed array)
+  //  -- x2 : AllocationSite or undefined
   //  -- sp[0] : return address
   //  -- sp[4] : last argument
   // -----------------------------------
   Register constructor = x1;
-  Register feedback_vector = x2;
-  Register slot_index = x3;
-
-  ASSERT_EQ(*TypeFeedbackInfo::MegamorphicSentinel(masm->isolate()),
-            masm->isolate()->heap()->megamorphic_symbol());
+  Register allocation_site = x2;
 
   if (FLAG_debug_code) {
     // The array construct code is only set for the global and natives
@@ -5432,37 +5442,15 @@ void ArrayConstructorStub::Generate(MacroAssembler* masm) {
     __ Abort(kUnexpectedInitialMapForArrayFunction);
     __ Bind(&map_ok);
 
-    // In feedback_vector, we expect either the megamorphic symbol or a valid
-    // fixed array.
-    Label okay_here;
-    Handle<Map> fixed_array_map = masm->isolate()->factory()->fixed_array_map();
-    __ JumpIfRoot(feedback_vector, Heap::kMegamorphicSymbolRootIndex,
-                  &okay_here);
-    __ Ldr(x10, FieldMemOperand(feedback_vector, FixedArray::kMapOffset));
-    __ Cmp(x10, Operand(fixed_array_map));
-    __ Assert(eq, kExpectedFixedArrayInFeedbackVector);
-
-    // slot_index should be a smi if we don't have undefined in feedback_vector.
-    __ AssertSmi(slot_index);
-
-    __ Bind(&okay_here);
+    // We should either have undefined in the allocation_site register or a
+    // valid AllocationSite.
+    __ AssertUndefinedOrAllocationSite(allocation_site, x10);
   }
 
-  Register allocation_site = x2;  // Overwrites feedback_vector.
   Register kind = x3;
   Label no_info;
   // Get the elements kind and case on that.
-  __ JumpIfRoot(feedback_vector, Heap::kMegamorphicSymbolRootIndex, &no_info);
-  __ Add(feedback_vector, feedback_vector,
-         Operand::UntagSmiAndScale(slot_index, kPointerSizeLog2));
-  __ Ldr(allocation_site, FieldMemOperand(feedback_vector,
-                                          FixedArray::kHeaderSize));
-
-  // If the feedback vector is the megamorphic symbol, or contains anything
-  // other than an AllocationSite, call an array constructor that doesn't
-  // use AllocationSites.
-  __ Ldr(x10, FieldMemOperand(allocation_site, AllocationSite::kMapOffset));
-  __ JumpIfNotRoot(x10, Heap::kAllocationSiteMapRootIndex, &no_info);
+  __ JumpIfRoot(allocation_site, Heap::kUndefinedValueRootIndex, &no_info);
 
   __ Ldrsw(kind,
            UntagSmiFieldMemOperand(allocation_site,