Reduce size of LinearBitmapPipeline

src/core/SkLinearBitmapPipeline.h

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkLinearBitmapPipeline_DEFINED
 #define SkLinearBitmapPipeline_DEFINED
 
@@ skipping 73 matching lines @@
 
     private:
         std::function<void (Next*, void*)> fStageCloner;
         struct SK_STRUCT_ALIGN(16) Space {
             char space[kSize];
         };
         bool fIsInitialized;
         mutable Space fSpace;
     };
 
+///////////////////////////////////////////////////////////////////////////////////////////////////
+// PolyMemory
+    template <typename Base, size_t kSize>
+    class PolyMemory {
+    public:
+        PolyMemory() : fIsInitialized{false} { }
+        ~PolyMemory() {
+            if (fIsInitialized) {
+                this->get()->~Base();
+            }
+        }
+        template<typename Variant, typename... Args>
+        void init(Args&& ... args) {
+            SkASSERTF(sizeof(Variant) <= sizeof(fSpace),
+                      "Size Variant: %d, Space: %d", sizeof(Variant), sizeof(fSpace));
+
+            new (&fSpace) Variant(std::forward<Args>(args)...);
+            fIsInitialized = true;
+        }
+
+        Base* get() const { return reinterpret_cast<Base*>(&fSpace); }
+        Base* operator->() const { return this->get(); }
+        Base& operator*() const { return *(this->get()); }
+
+    private:
+        struct SK_STRUCT_ALIGN(16) Space {
+            char space[kSize];
+        };
+        mutable Space fSpace;
+        bool          fIsInitialized;
+
+    };
+
     class PointProcessorInterface;
     class SampleProcessorInterface;
     class BlendProcessorInterface;
     class DestinationInterface;
+    class PixelAccessorInterface;
 
     // These values were generated by the assert above in Stage::init{Sink|Stage}.
-    using MatrixStage  = Stage<PointProcessorInterface,  160, PointProcessorInterface>;
-    using TileStage    = Stage<PointProcessorInterface,  160, SampleProcessorInterface>;
-    using SampleStage  = Stage<SampleProcessorInterface, 100, BlendProcessorInterface>;
-    using BlenderStage = Stage<BlendProcessorInterface,   40>;
+    using MatrixStage  = Stage<PointProcessorInterface,    160, PointProcessorInterface>;
+    using TileStage    = Stage<PointProcessorInterface,    160, SampleProcessorInterface>;
+    using SampleStage  = Stage<SampleProcessorInterface,   100, BlendProcessorInterface>;
+    using BlenderStage = Stage<BlendProcessorInterface,     40>;
+    using Accessor     = PolyMemory<PixelAccessorInterface, 48>;
 
 private:
     PointProcessorInterface* fFirstStage;
     MatrixStage              fMatrixStage;
     TileStage                fTileStage;
     SampleStage              fSampleStage;
     BlenderStage             fBlenderStage;
     DestinationInterface*    fLastStage;
+    Accessor                 fAccessor;
 };
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 // SkEmbeddableLinearPipeline - manage stricter alignment needs for SkLinearBitmapPipeline.
 class SkEmbeddableLinearPipeline {
 public:
     SkEmbeddableLinearPipeline() { }
     ~SkEmbeddableLinearPipeline() {
         if (get() != nullptr) {
             get()->~SkLinearBitmapPipeline();
@@ skipping 14 matching lines @@
 private:
     enum {
         kActualSize = sizeof(SkLinearBitmapPipeline),
         kPaddedSize = SkAlignPtr(kActualSize + 12),
     };
     void* fPipelineStorage[kPaddedSize / sizeof(void*)];
     SkLinearBitmapPipeline* fPipeline{nullptr};
 };
 
 #endif  // SkLinearBitmapPipeline_DEFINED