[turbofan] Add initial support for growing stores.

src/compiler/simplified-operator.h

Index: src/compiler/simplified-operator.h
diff --git a/src/compiler/simplified-operator.h b/src/compiler/simplified-operator.h
index 37b64125a8fade7149a6d5af543ec19d83efbdc4..eb630b90c7979ad2f3c70e7dfc88f798b7d1528c 100644
--- a/src/compiler/simplified-operator.h
+++ b/src/compiler/simplified-operator.h
@@ -141,6 +141,22 @@ std::ostream& operator<<(std::ostream&, CheckForMinusZeroMode);
 
 CheckForMinusZeroMode CheckMinusZeroModeOf(const Operator*) WARN_UNUSED_RESULT;
 
+// A descriptor for growing elements backing stores.
+enum class GrowFastElementsFlag : uint8_t {
+  kNone = 0u,
+  kArrayObject = 1u << 0,     // Update JSArray::length field.
+  kHoleyElements = 1u << 1,   // Backing store is holey.
+  kDoubleElements = 1u << 2,  // Backing store contains doubles.
+};
+typedef base::Flags<GrowFastElementsFlag> GrowFastElementsFlags;
+
+DEFINE_OPERATORS_FOR_FLAGS(GrowFastElementsFlags)
+
+std::ostream& operator<<(std::ostream&, GrowFastElementsFlags);
+
+GrowFastElementsFlags GrowFastElementsFlagsOf(const Operator*)
+    WARN_UNUSED_RESULT;
+
 // A descriptor for elements kind transitions.
 enum class ElementsTransition : uint8_t {
   kFastTransition,  // simple transition, just updating the map.
@@ -323,6 +339,9 @@ class SimplifiedOperatorBuilder final : public ZoneObject {
   // ensure-writable-fast-elements object, elements
   const Operator* EnsureWritableFastElements();
 
+  // maybe-grow-fast-elements object, elements, index, length
+  const Operator* MaybeGrowFastElements(GrowFastElementsFlags flags);
+
   // transition-elements-kind object, from-map, to-map
   const Operator* TransitionElementsKind(ElementsTransition transition);