Fabric: Using small_vector instead of regular vector in some hot code paths

Summary: The hope is that it will remove many unnececery allocations improving overal perfromance.

Reviewed By: mdvacca

Differential Revision: D14249198

fbshipit-source-id: f0442b3919ccead0582a3190dea0e33d517d85f6

ReactCommon/fabric/attributedstring/AttributedString.cpp

@@ -70,7 +70,7 @@ void AttributedString::prependAttributedString(
       attributedString.fragments_.end());
 }
 
-const std::vector<Fragment> &AttributedString::getFragments() const {
+const Fragments &AttributedString::getFragments() const {
   return fragments_;
 }
 

ReactCommon/fabric/attributedstring/AttributedString.h

@@ -44,7 +44,7 @@ class AttributedString : public Sealable, public DebugStringConvertible {
     bool operator!=(const Fragment &rhs) const;
   };
 
-  using Fragments = std::vector<Fragment>;
+  using Fragments = better::small_vector<Fragment, 1>;
 
   /*
    * Appends and prepends a `fragment` to the string.

ReactCommon/fabric/components/view/yoga/YogaLayoutableShadowNode.cpp

@@ -90,7 +90,7 @@ void YogaLayoutableShadowNode::appendChild(YogaLayoutableShadowNode *child) {
 }
 
 void YogaLayoutableShadowNode::setChildren(
-    std::vector<YogaLayoutableShadowNode *> children) {
+    YogaLayoutableShadowNode::UnsharedList children) {
   yogaNode_.setChildren({});
   for (const auto &child : children) {
     appendChild(child);
@@ -139,9 +139,9 @@ void YogaLayoutableShadowNode::layoutChildren(LayoutContext layoutContext) {
   }
 }
 
-std::vector<LayoutableShadowNode *>
+LayoutableShadowNode::UnsharedList
 YogaLayoutableShadowNode::getLayoutableChildNodes() const {
-  std::vector<LayoutableShadowNode *> yogaLayoutableChildNodes;
+  LayoutableShadowNode::UnsharedList yogaLayoutableChildNodes;
   yogaLayoutableChildNodes.reserve(yogaNode_.getChildren().size());
 
   for (const auto &childYogaNode : yogaNode_.getChildren()) {

ReactCommon/fabric/components/view/yoga/YogaLayoutableShadowNode.h

@@ -15,6 +15,7 @@
 #include <react/components/view/YogaStylableProps.h>
 #include <react/core/LayoutableShadowNode.h>
 #include <react/core/Sealable.h>
+#include <react/core/ShadowNode.h>
 #include <react/debug/DebugStringConvertible.h>
 
 namespace facebook {
@@ -24,6 +25,10 @@ class YogaLayoutableShadowNode : public LayoutableShadowNode,
                                  public virtual DebugStringConvertible,
                                  public virtual Sealable {
  public:
+  using UnsharedList = better::small_vector<
+      YogaLayoutableShadowNode *,
+      kShadowNodeChildrenSmallVectorSize>;
+
 #pragma mark - Constructors
 
   YogaLayoutableShadowNode();
@@ -51,7 +56,7 @@ class YogaLayoutableShadowNode : public LayoutableShadowNode,
    * instances. Complements `ShadowNode::setChildren(...)` functionality from
    * Yoga perspective.
    */
-  void setChildren(std::vector<YogaLayoutableShadowNode *> children);
+  void setChildren(YogaLayoutableShadowNode::UnsharedList children);
 
   /*
    * Sets Yoga styles based on given `YogaStylableProps`.
@@ -75,7 +80,7 @@ class YogaLayoutableShadowNode : public LayoutableShadowNode,
 
   void layoutChildren(LayoutContext layoutContext) override;
 
-  std::vector<LayoutableShadowNode *> getLayoutableChildNodes() const override;
+  LayoutableShadowNode::UnsharedList getLayoutableChildNodes() const override;
 
  protected:
   /*

ReactCommon/fabric/core/layout/LayoutableShadowNode.h

@@ -12,8 +12,10 @@
 #include <memory>
 #include <vector>
 
+#include <better/small_vector.h>
 #include <react/core/LayoutMetrics.h>
 #include <react/core/Sealable.h>
+#include <react/core/ShadowNode.h>
 #include <react/debug/DebugStringConvertible.h>
 
 namespace facebook {
@@ -28,6 +30,9 @@ struct LayoutContext;
  */
 class LayoutableShadowNode : public virtual Sealable {
  public:
+  using UnsharedList = better::
+      small_vector<LayoutableShadowNode *, kShadowNodeChildrenSmallVectorSize>;
+
   virtual ~LayoutableShadowNode() noexcept = default;
 
   /*
@@ -97,7 +102,7 @@ class LayoutableShadowNode : public virtual Sealable {
   /*
    * Returns layoutable children to interate on.
    */
-  virtual std::vector<LayoutableShadowNode *> getLayoutableChildNodes()
+  virtual LayoutableShadowNode::UnsharedList getLayoutableChildNodes()
       const = 0;
 
   /*

ReactCommon/fabric/core/shadownode/ConcreteShadowNode.h

@@ -90,8 +90,12 @@ class ConcreteShadowNode : public ShadowNode {
    * Returns subset of children that are inherited from `SpecificShadowNodeT`.
    */
   template <typename SpecificShadowNodeT>
-  std::vector<SpecificShadowNodeT *> getChildrenSlice() const {
-    std::vector<SpecificShadowNodeT *> children;
+  better::
+      small_vector<SpecificShadowNodeT *, kShadowNodeChildrenSmallVectorSize>
+      getChildrenSlice() const {
+    better::
+        small_vector<SpecificShadowNodeT *, kShadowNodeChildrenSmallVectorSize>
+            children;
     for (const auto &childShadowNode : getChildren()) {
       auto specificChildShadowNode =
           dynamic_cast<const SpecificShadowNodeT *>(childShadowNode.get());

ReactCommon/fabric/mounting/ShadowView.h

@@ -5,6 +5,7 @@
 
 #pragma once
 
+#include <better/small_vector.h>
 #include <folly/Hash.h>
 #include <react/core/EventEmitter.h>
 #include <react/core/LayoutMetrics.h>
@@ -59,7 +60,8 @@ struct ShadowViewNodePair final {
   bool operator!=(const ShadowViewNodePair &rhs) const;
 };
 
-using ShadowViewNodePairList = std::vector<ShadowViewNodePair>;
+using ShadowViewNodePairList = better::
+    small_vector<ShadowViewNodePair, kShadowNodeChildrenSmallVectorSize>;
 
 } // namespace react
 } // namespace facebook