Use texture barriers to read directly from the RT

src/gpu/GrPipelineBuilder.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 "GrPipelineBuilder.h"
 
 #include "GrBatch.h"
@@ skipping 105 matching lines @@
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 
 // Some blend modes allow folding a fractional coverage value into the color's alpha channel, while
 // others will blend incorrectly.
 bool GrPipelineBuilder::canTweakAlphaForCoverage() const {
     return this->getXPFactory()->canTweakAlphaForCoverage();
 }
 
+// Some blending extensions require the use of a barrier to ensure coherent results.
+bool GrPipelineBuilder::willBlendCoherently(const GrDrawTargetCaps& caps) const {
+    return this->getXPFactory()->willBlendCoherently(caps);

[Mark Kilgard, 2015/04/02 23:02:38]

this seems a lot of indirection to just return a boolean that hopefully will be
false most of the time

could the knowledge be cached within the GrPipelineBuilder?

+}
+
 ////////////////////////////////////////////////////////////////////////////////
 
 GrPipelineBuilder::~GrPipelineBuilder() {
     SkASSERT(0 == fBlockEffectRemovalCnt);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 
 bool GrPipelineBuilder::willBlendWithDst(const GrPrimitiveProcessor* pp) const {
     this->calcColorInvariantOutput(pp);
@@ skipping 41 matching lines @@
 void GrPipelineBuilder::calcCoverageInvariantOutput(GrColor coverage) const {
     if (!fCoverageProcInfoValid || coverage != fCoverageCache) {
         GrColorComponentFlags flags = kRGBA_GrColorComponentFlags;
         fCoverageProcInfo.calcWithInitialValues(fCoverageStages.begin(),
                                                 this->numCoverageFragmentStages(), coverage, flags,
                                                 true);
         fCoverageProcInfoValid = true;
         fCoverageCache = coverage;
     }
 }