[turbofan] Introduce new Select operator to improve bounds checking.

src/compiler/js-typed-lowering.cc

 // Copyright 2014 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/compiler/access-builder.h"
 #include "src/compiler/graph-inl.h"
 #include "src/compiler/js-builtin-reducer.h"
 #include "src/compiler/js-typed-lowering.h"
 #include "src/compiler/node-aux-data-inl.h"
 #include "src/compiler/node-properties-inl.h"
@@ skipping 594 matching lines @@
     Handle<JSTypedArray> array =
         Handle<JSTypedArray>::cast(base_type->AsConstant()->Value());
     if (IsExternalArrayElementsKind(array->map()->elements_kind())) {
       ExternalArrayType type = array->type();
       double byte_length = array->byte_length()->Number();
       if (byte_length <= kMaxInt) {
         Handle<ExternalArray> elements =
             Handle<ExternalArray>::cast(handle(array->elements()));
         Node* pointer = jsgraph()->IntPtrConstant(
             bit_cast<intptr_t>(elements->external_pointer()));
-        Node* length = jsgraph()->Constant(byte_length / array->element_size());
+        Node* length = jsgraph()->Constant(array->length()->Number());
         Node* effect = NodeProperties::GetEffectInput(node);
         Node* load = graph()->NewNode(
             simplified()->LoadElement(
                 AccessBuilder::ForTypedArrayElement(type, true)),
             pointer, key, length, effect);
         return ReplaceEagerly(node, load);
       }
     }
   }
   return NoChange();
@@ skipping 14 matching lines @@
     Handle<JSTypedArray> array =
         Handle<JSTypedArray>::cast(base_type->AsConstant()->Value());
     if (IsExternalArrayElementsKind(array->map()->elements_kind())) {
       ExternalArrayType type = array->type();
       double byte_length = array->byte_length()->Number();
       if (byte_length <= kMaxInt) {
         Handle<ExternalArray> elements =
             Handle<ExternalArray>::cast(handle(array->elements()));
         Node* pointer = jsgraph()->IntPtrConstant(
             bit_cast<intptr_t>(elements->external_pointer()));
-        Node* length = jsgraph()->Constant(byte_length / array->element_size());
+        Node* length = jsgraph()->Constant(array->length()->Number());
         Node* effect = NodeProperties::GetEffectInput(node);
         Node* control = NodeProperties::GetControlInput(node);
         Node* store = graph()->NewNode(
             simplified()->StoreElement(
                 AccessBuilder::ForTypedArrayElement(type, true)),
             pointer, key, length, value, effect, control);
         return ReplaceEagerly(node, store);
       }
     }
   }
@@ skipping 93 matching lines @@
       return JSBuiltinReducer(jsgraph()).Reduce(node);
     default:
       break;
   }
   return NoChange();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8