Code cleanup in GenerateRecordCallTarget.

src/arm64/code-stubs-arm64.cc

 // Copyright 2013 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_ARM64
 
 #include "src/bootstrapper.h"
 #include "src/code-stubs.h"
@@ skipping 2718 matching lines @@
 #endif
 }
 
 
 static void CallStubInRecordCallTarget(MacroAssembler* masm, CodeStub* stub,
                                        Register argc, Register function,
                                        Register feedback_vector,
                                        Register index) {
   FrameScope scope(masm, StackFrame::INTERNAL);
 
-  // Arguments register must be smi-tagged to call out.
+  // Number-of-arguments register must be smi-tagged to call out.
   __ SmiTag(argc);
   __ Push(argc, function, feedback_vector, index);
 
   DCHECK(feedback_vector.Is(x2) && index.Is(x3));
   __ CallStub(stub);
 
   __ Pop(index, feedback_vector, function, argc);
   __ SmiUntag(argc);
 }
 
@@ skipping 22 matching lines @@
   // Load the cache state.
   Register feedback = scratch1;
   Register feedback_map = scratch2;
   Register feedback_value = scratch3;
   __ Add(feedback, feedback_vector,
          Operand::UntagSmiAndScale(index, kPointerSizeLog2));
   __ Ldr(feedback, FieldMemOperand(feedback, FixedArray::kHeaderSize));
 
   // A monomorphic cache hit or an already megamorphic state: invoke the
   // function without changing the state.
+  // We don't know if feedback value is a WeakCell or a Symbol, but it's
+  // harmless to read at this position in a symbol (see static asserts in
+  // type-feedback-vector.h).
   Label check_allocation_site;
   __ Ldr(feedback_value, FieldMemOperand(feedback, WeakCell::kValueOffset));
   __ Cmp(function, feedback_value);
   __ B(eq, &done);
   __ CompareRoot(feedback, Heap::kmegamorphic_symbolRootIndex);
   __ B(eq, &done);
-  __ Ldr(feedback_map, FieldMemOperand(feedback, 0));
+  __ Ldr(feedback_map, FieldMemOperand(feedback, HeapObject::kMapOffset));
   __ CompareRoot(feedback_map, Heap::kWeakCellMapRootIndex);
   __ B(ne, FLAG_pretenuring_call_new ? &miss : &check_allocation_site);
 
-  // If function is not equal to the weak cell value, and the weak cell value is
-  // cleared, we have a new chance to become monomorphic.
+  // If the weak cell is cleared, we have a new chance to become monomorphic.
   __ JumpIfSmi(feedback_value, &initialize);
   __ B(&megamorphic);
 
   if (!FLAG_pretenuring_call_new) {
     __ bind(&check_allocation_site);
     // If we came here, we need to see if we are the array function.
     // If we didn't have a matching function, and we didn't find the megamorph
     // sentinel, then we have in the slot either some other function or an
-    // AllocationSite. Do a map check on the object in scratch1 register.
+    // AllocationSite.
     __ JumpIfNotRoot(feedback_map, Heap::kAllocationSiteMapRootIndex, &miss);
 
     // Make sure the function is the Array() function
     __ LoadGlobalFunction(Context::ARRAY_FUNCTION_INDEX, scratch1);
     __ Cmp(function, scratch1);
     __ B(ne, &megamorphic);
     __ B(&done);
   }
 
   __ Bind(&miss);
@@ skipping 2940 matching lines @@
                            kStackUnwindSpace, NULL, spill_offset,
                            MemOperand(fp, 6 * kPointerSize), NULL);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM64