Revert of Experimental CL to stop using subdata

src/gpu/gl/GrGLGpu.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "GrGLGpu.h"
 #include "GrGLGLSL.h"
@@ skipping 1578 matching lines @@
 void* GrGLGpu::mapBuffer(GrGLuint id, GrGLenum type, bool dynamic, size_t currentSize,
                          size_t requestedSize) {
     void* mapPtr = nullptr;
     // Handling dirty context is done in the bindBuffer call
     switch (this->glCaps().mapBufferType()) {
         case GrGLCaps::kNone_MapBufferType:
             break;
         case GrGLCaps::kMapBuffer_MapBufferType:
             this->bindBuffer(id, type);
             // Let driver know it can discard the old data
-            if (currentSize != requestedSize) {
+            if (GR_GL_USE_BUFFER_DATA_NULL_HINT || currentSize != requestedSize) {
                 GL_CALL(BufferData(type, requestedSize, nullptr,
                                    dynamic ? DYNAMIC_USAGE_PARAM : GR_GL_STATIC_DRAW));
             }
             GL_CALL_RET(mapPtr, MapBuffer(type, GR_GL_WRITE_ONLY));
             break;
         case GrGLCaps::kMapBufferRange_MapBufferType: {
             this->bindBuffer(id, type);
             // Make sure the GL buffer size agrees with fDesc before mapping.
             if (currentSize != requestedSize) {
                 GL_CALL(BufferData(type, requestedSize, nullptr,
@@ skipping 17 matching lines @@
     return mapPtr;
 }
 
 void GrGLGpu::bufferData(GrGLuint id, GrGLenum type, bool dynamic, size_t currentSize,
                          const void* src, size_t srcSizeInBytes) {
     SkASSERT(srcSizeInBytes <= currentSize);
     // bindbuffer handles dirty context
     this->bindBuffer(id, type);
     GrGLenum usage = dynamic ? DYNAMIC_USAGE_PARAM : GR_GL_STATIC_DRAW;
 
+#if GR_GL_USE_BUFFER_DATA_NULL_HINT
+    if (currentSize == srcSizeInBytes) {
+        GL_CALL(BufferData(type, (GrGLsizeiptr) srcSizeInBytes, src, usage));
+    } else {
+        // Before we call glBufferSubData we give the driver a hint using
+        // glBufferData with nullptr. This makes the old buffer contents
+        // inaccessible to future draws. The GPU may still be processing
+        // draws that reference the old contents. With this hint it can
+        // assign a different allocation for the new contents to avoid
+        // flushing the gpu past draws consuming the old contents.
+        // TODO I think we actually want to try calling bufferData here
+        GL_CALL(BufferData(type, currentSize, nullptr, usage));
+        GL_CALL(BufferSubData(type, 0, (GrGLsizeiptr) srcSizeInBytes, src));
+    }
+#else
     // Note that we're cheating on the size here. Currently no methods
     // allow a partial update that preserves contents of non-updated
     // portions of the buffer (map() does a glBufferData(..size, nullptr..))
     GL_CALL(BufferData(type, srcSizeInBytes, src, usage));
+#endif
 }
 
 void GrGLGpu::unmapBuffer(GrGLuint id, GrGLenum type, void* mapPtr) {
     // bind buffer handles the dirty context
     switch (this->glCaps().mapBufferType()) {
         case GrGLCaps::kNone_MapBufferType:
             SkDEBUGFAIL("Shouldn't get here.");
             return;
         case GrGLCaps::kMapBuffer_MapBufferType: // fall through
         case GrGLCaps::kMapBufferRange_MapBufferType:
@@ skipping 1628 matching lines @@
             this->setVertexArrayID(gpu, 0);
         }
         int attrCount = gpu->glCaps().maxVertexAttributes();
         if (fDefaultVertexArrayAttribState.count() != attrCount) {
             fDefaultVertexArrayAttribState.resize(attrCount);
         }
         attribState = &fDefaultVertexArrayAttribState;
     }
     return attribState;
 }