Use texture barriers to read directly from the RT

src/gpu/GrTargetCommands.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrTargetCommands.h"
 
 #include "GrColor.h"
@@ skipping 384 matching lines @@
 }
 
 void GrTargetCommands::ClearStencilClip::execute(GrGpu* gpu, const SetState*) {
     gpu->clearStencilClip(fRect, fInsideClip, this->renderTarget());
 }
 
 void GrTargetCommands::CopySurface::execute(GrGpu* gpu, const SetState*) {
     gpu->copySurface(this->dst(), this->src(), fSrcRect, fDstPoint);
 }
 
+void GrTargetCommands::XferBarrier::execute(GrGpu* gpu, const SetState* state) {
+    gpu->setXferBarrier(fBarrierType);
+}
+
 GrTargetCommands::Cmd* GrTargetCommands::recordCopySurface(GrInOrderDrawBuffer* iodb,
                                                            GrSurface* dst,
                                                            GrSurface* src,
                                                            const SkIRect& srcRect,
                                                            const SkIPoint& dstPoint) {
     if (iodb->getGpu()->canCopySurface(dst, src, srcRect, dstPoint)) {
         this->closeBatch();
         CopySurface* cs = GrNEW_APPEND_TO_RECORDER(fCmdBuffer, CopySurface, (dst, src));
         cs->fSrcRect = srcRect;
         cs->fDstPoint = dstPoint;
@@ skipping 19 matching lines @@
     if (fPrevState && fPrevState->fPrimitiveProcessor.get() &&
         fPrevState->fPrimitiveProcessor->canMakeEqual(fPrevState->fBatchTracker,
                                                       *ss->fPrimitiveProcessor,
                                                       ss->fBatchTracker) &&
         fPrevState->getPipeline()->isEqual(*ss->getPipeline())) {
         fCmdBuffer.pop_back();
     } else {
         fPrevState = ss;
         iodb->recordTraceMarkersIfNecessary(ss);
     }
+
+    this->recordXferBarrierIfNecessary(iodb, pipelineInfo);
     return true;
 }
 
 bool GrTargetCommands::setupPipelineAndShouldDraw(GrInOrderDrawBuffer* iodb,
                                                   GrBatch* batch,
                                                   const GrDrawTarget::PipelineInfo& pipelineInfo) {
     SetState* ss = GrNEW_APPEND_TO_RECORDER(fCmdBuffer, SetState, ());
     iodb->setupPipeline(pipelineInfo, ss->pipelineLocation()); 
 
     if (ss->getPipeline()->mustSkip()) {
         fCmdBuffer.pop_back();
         return false;
     }
 
     batch->initBatchTracker(ss->getPipeline()->getInitBatchTracker());
 
     if (fPrevState && !fPrevState->fPrimitiveProcessor.get() &&
         fPrevState->getPipeline()->isEqual(*ss->getPipeline())) {
         fCmdBuffer.pop_back();
     } else {
         this->closeBatch();
         fPrevState = ss;
         iodb->recordTraceMarkersIfNecessary(ss);
     }
+
+    this->recordXferBarrierIfNecessary(iodb, pipelineInfo);
     return true;
 }
 
+void GrTargetCommands::recordXferBarrierIfNecessary(GrInOrderDrawBuffer* iodb,
+                                                    const GrDrawTarget::PipelineInfo& info) {
+    SkASSERT(fPrevState);
+    const GrXferProcessor& xp = *fPrevState->getXferProcessor();
+    GrRenderTarget* rt = fPrevState->getRenderTarget();
+
+    GrXferBarrierType barrierType;
+    if (!xp.willNeedXferBarrier(rt, *iodb->caps(), &barrierType)) {
+        return;
+    }
+
+    this->closeBatch();
+
+    XferBarrier* xb = GrNEW_APPEND_TO_RECORDER(fCmdBuffer, XferBarrier, ());
+    xb->fBarrierType = barrierType;
+
+    iodb->recordTraceMarkersIfNecessary(xb);
+}
+