Implement support for mixed sampled render targets

src/gpu/GrPipeline.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 "GrPipeline.h"
 
 #include "GrBatch.h"
@@ skipping 11 matching lines @@
                        const GrDeviceCoordTexture* dstCopy) {
     // Create XferProcessor from DS's XPFactory
     SkAutoTUnref<GrXferProcessor> xferProcessor(
         pipelineBuilder.getXPFactory()->createXferProcessor(colorPOI, coveragePOI, dstCopy, caps));
 
     GrColor overrideColor = GrColor_ILLEGAL;
     if (colorPOI.firstEffectiveStageIndex() != 0) {
         overrideColor = colorPOI.inputColorToEffectiveStage();
     }
 
+    fRenderTarget.reset(pipelineBuilder.fRenderTarget.get());
+    SkASSERT(fRenderTarget);
+
+    fFlags = 0;
+    if (pipelineBuilder.isHWAntialias()) {
+        fFlags |= kHWAA_Flag;
+    }
+    if (pipelineBuilder.isDither()) {
+        fFlags |= kDither_Flag;
+    }
+
     GrXferProcessor::OptFlags optFlags;
     if (xferProcessor) {
         fXferProcessor.reset(xferProcessor.get());
 
-        optFlags = xferProcessor->getOptimizations(colorPOI,
+        GrProcOptInfo localColorPOI = colorPOI;
+        // Optimizations will try to turn off blending which is required by mixed
+        // sampled modes.
+        bool isMixedSampledTarget =
+            (this->getRenderTarget()->sampleConfig() == kStencil_GrSampleConfig);
+        localColorPOI.setNeedsCoverageModulation(this->isHWAntialiasState() &&
+                                                 isMixedSampledTarget);
+
+        optFlags = xferProcessor->getOptimizations(localColorPOI,

[Mark Kilgard, 2015/03/24 14:05:08]

For Google:  enabling/disabling GL_BLEND when using
GL_ONE,GL_ONE_MINUS_SRC_ALPHA or GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA blending is
probably just costing you CPU drivers doing driver validation if the alpha from
shader is guaranteed 1.0

NVIDIA GPUs for the last 5+ years should be able to render "just as fast" for
these blend modes when source alpha==1.0 as having blending disabled.  The GPU
recognizes the blend optimization automatically and avoids read-modify-writes
during alpha==1.0 blending.  But calling glEnable(GL_BLEND)/glDisable(GL_BLEND)
is going to cause driver validations.

Please consider having a mode so K1 and other GPUs can simply not excessively
enable/disable blending.

                                                    coveragePOI,
                                                    pipelineBuilder.getStencil().doesWrite(),
                                                    &overrideColor,
                                                    caps);
     }
 
     // When path rendering the stencil settings are not always set on the GrPipelineBuilder
     // so we must check the draw type. In cases where we will skip drawing we simply return a
     // null GrPipeline.
     if (!xferProcessor || (GrXferProcessor::kSkipDraw_OptFlag & optFlags)) {
         // Set the fields that don't default init and return. The lack of a render target will
         // indicate that this can be skipped.
         fFlags = 0;
         fDrawFace = GrPipelineBuilder::kInvalid_DrawFace;
         return;
     }
 
-    fRenderTarget.reset(pipelineBuilder.fRenderTarget.get());
-    SkASSERT(fRenderTarget);
     fScissorState = scissorState;
     fStencilSettings = pipelineBuilder.getStencil();
     fDrawFace = pipelineBuilder.getDrawFace();
 
-    fFlags = 0;
-    if (pipelineBuilder.isHWAntialias()) {
-        fFlags |= kHWAA_Flag;
-    }
-    if (pipelineBuilder.isDither()) {
-        fFlags |= kDither_Flag;
-    }
-
     int firstColorStageIdx = colorPOI.firstEffectiveStageIndex();
 
     // TODO: Once we can handle single or four channel input into coverage stages then we can use
     // GrPipelineBuilder's coverageProcInfo (like color above) to set this initial information.
     int firstCoverageStageIdx = 0;
 
     GrXferProcessor::BlendInfo blendInfo;
     fXferProcessor->getBlendInfo(&blendInfo);
 
     this->adjustProgramFromOptimizations(pipelineBuilder, optFlags, colorPOI, coveragePOI,
@@ skipping 73 matching lines @@
     SkASSERT(this->numFragmentStages() == that.numFragmentStages());
     for (int i = 0; i < this->numFragmentStages(); i++) {
 
         if (this->getFragmentStage(i) != that.getFragmentStage(i)) {
             return false;
         }
     }
     return true;
 }