[stubs] Ensure generated CalculateNewElementsCapacity is identical to runtime version

src/code-stub-assembler.cc

 // Copyright 2016 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/code-stub-assembler.h"
 #include "src/code-factory.h"
 #include "src/frames-inl.h"
 #include "src/frames.h"
 
 namespace v8 {
 namespace internal {
@@ skipping 1474 matching lines @@
   Node* capacity =
       TaggedToParameter(LoadFixedArrayBaseLength(var_elements.value()), mode);
 
   // Resize the capacity of the fixed array if it doesn't fit.
   Label fits(this, &var_elements);
   Node* first = arg_index.value();
   Node* growth = IntPtrSub(args.GetLength(), first);
   Node* new_length =
       IntPtrOrSmiAdd(WordToParameter(growth, mode), var_length.value(), mode);
   GotoUnless(IntPtrOrSmiGreaterThan(new_length, capacity, mode), &fits);
-  Node* new_capacity = CalculateNewElementsCapacity(
-      IntPtrOrSmiAdd(new_length, IntPtrOrSmiConstant(1, mode), mode), mode);
+  Node* new_capacity = CalculateNewElementsCapacity(new_length, mode);
   var_elements.Bind(GrowElementsCapacity(array, var_elements.value(), kind,
                                          kind, capacity, new_capacity, mode,
                                          &pre_bailout));
   Goto(&fits);
   Bind(&fits);
   Node* elements = var_elements.value();
 
   // Push each argument onto the end of the array now that there is enough
   // capacity.
   CodeStubAssembler::VariableList push_vars({&var_length}, zone());
@@ skipping 832 matching lines @@
       } else {
         value = LoadHeapNumberValue(value);
       }
     }
     return value;
   }
 }
 
 Node* CodeStubAssembler::CalculateNewElementsCapacity(Node* old_capacity,
                                                       ParameterMode mode) {
-  if (mode == SMI_PARAMETERS) {
-    old_capacity = BitcastTaggedToWord(old_capacity);
-  }
-  Node* half_old_capacity = WordShr(old_capacity, IntPtrConstant(1));
-  Node* new_capacity = IntPtrAdd(half_old_capacity, old_capacity);
-  Node* unconditioned_result = IntPtrAdd(new_capacity, IntPtrConstant(16));
-  if (mode == SMI_PARAMETERS) {
-    return SmiAnd(BitcastWordToTaggedSigned(unconditioned_result),
-                  SmiConstant(-1));
-  } else {
-    return unconditioned_result;
-  }
+  Node* half_old_capacity = WordOrSmiShr(old_capacity, 1, mode);
+  Node* new_capacity = IntPtrOrSmiAdd(half_old_capacity, old_capacity, mode);
+  Node* padding = IntPtrOrSmiConstant(16, mode);
+  return IntPtrOrSmiAdd(new_capacity, padding, mode);
 }
 
 Node* CodeStubAssembler::TryGrowElementsCapacity(Node* object, Node* elements,
                                                  ElementsKind kind, Node* key,
                                                  Label* bailout) {
   Node* capacity = LoadFixedArrayBaseLength(elements);
 
   ParameterMode mode = OptimalParameterMode();
   capacity = TaggedToParameter(capacity, mode);
   key = TaggedToParameter(key, mode);
@@ skipping 5973 matching lines @@
   StoreObjectFieldNoWriteBarrier(result,
                                  PromiseReactionJobInfo::kDebugNameOffset,
                                  SmiConstant(kDebugNotActive));
   StoreObjectFieldNoWriteBarrier(result, PromiseReactionJobInfo::kContextOffset,
                                  context);
   return result;
 }
 
 }  // namespace internal
 }  // namespace v8