Stop discarding in frag shader when coverage is zero and stencil writes are enabled

src/gpu/gl/GrGLProgram.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 "GrGLProgram.h"
 
 #include "GrAllocator.h"
@@ skipping 102 matching lines @@
     ///////////////////////////////////////////////////////////////////////////
     // compute the partial coverage
     GrGLSLExpr4 inCoverage = builder->getInputCoverage();
 
     fCoverageEffects.reset(
         builder->createAndEmitEffects(coverageStages,
                                       fDesc.getEffectKeys() + fDesc.numColorEffects(),
                                       fDesc.numCoverageEffects(),
                                       &inCoverage));
 
-    // discard if coverage is zero
-    if (header.fDiscardIfZeroCoverage && !inCoverage.isOnes()) {
-        if (inCoverage.isZeros()) {
-            // This is unfortunate.
-            builder->fsCodeAppend("\tdiscard;\n");
-        } else {
-            builder->fsCodeAppendf("\tif (all(lessThanEqual(%s, vec4(0.0)))) {\n\t\tdiscard;\n\t}\n",
-                                   inCoverage.c_str());
-        }
-    }
-
     if (GrGLProgramDesc::CoverageOutputUsesSecondaryOutput(header.fCoverageOutput)) {
         const char* secondaryOutputName = builder->enableSecondaryOutput();
 
         // default coeff to ones for kCoverage_DualSrcOutput
         GrGLSLExpr4 coeff(1);
         if (GrGLProgramDesc::kSecondaryCoverageISA_CoverageOutput == header.fCoverageOutput) {
             // Get (1-A) into coeff
             coeff = GrGLSLExpr4::VectorCast(GrGLSLExpr1(1) - inColor.a());
         } else if (GrGLProgramDesc::kSecondaryCoverageISC_CoverageOutput == header.fCoverageOutput) {
             // Get (1-RGBA) into coeff
@@ skipping 203 matching lines @@
 
         fMatrixState.fViewMatrix = drawState.getViewMatrix();
         fMatrixState.fRenderTargetSize = size;
         fMatrixState.fRenderTargetOrigin = rt->origin();
 
         GrGLfloat viewMatrix[3 * 3];
         fMatrixState.getGLMatrix<3>(viewMatrix);
         fUniformManager.setMatrix3f(fUniformHandles.fViewMatrixUni, viewMatrix);
     }
 }