Potentially optimize some GrGLEffects for known input color values

src/gpu/gl/GrGLShaderBuilder.cpp

Index: src/gpu/gl/GrGLShaderBuilder.cpp
diff --git a/src/gpu/gl/GrGLShaderBuilder.cpp b/src/gpu/gl/GrGLShaderBuilder.cpp
index 40ca0f2567fadddc842ec34376005104e83c66bc..40a0888362cc900c42ef15840e6447755a8ca749 100644
--- a/src/gpu/gl/GrGLShaderBuilder.cpp
+++ b/src/gpu/gl/GrGLShaderBuilder.cpp
@@ -289,13 +289,13 @@ void GrGLShaderBuilder::fsAppendTextureLookup(const GrGLShaderBuilder::TextureSa
 }
 
 void GrGLShaderBuilder::fsAppendTextureLookupAndModulate(
-                                            const char* modulation,
+                                            const GrGLSLExpr4& modulation,
                                             const GrGLShaderBuilder::TextureSampler& sampler,
                                             const char* coordName,
                                             GrSLType varyingType) {
     SkString lookup;
     this->appendTextureLookup(&lookup, sampler, coordName, varyingType);
-    fFSCode.append((GrGLSLExpr4(modulation) * GrGLSLExpr4(lookup)).c_str());
+    fFSCode.append((modulation * GrGLSLExpr4(lookup)).c_str());
 }
 
 GrGLShaderBuilder::DstReadKey GrGLShaderBuilder::KeyForDstRead(const GrTexture* dstCopy,
@@ -516,45 +516,24 @@ void GrGLShaderBuilder::createAndEmitEffects(GrGLProgramEffectsBuilder* programE
                                              const EffectKey effectKeys[],
                                              int effectCnt,
                                              GrGLSLExpr4* fsInOutColor) {
-    bool effectEmitted = false;
-
-    GrGLSLExpr4 inColor = *fsInOutColor;
-    GrGLSLExpr4 outColor;
-
     for (int e = 0; e < effectCnt; ++e) {
         SkASSERT(NULL != effectStages[e] && NULL != effectStages[e]->getEffect());
         const GrEffectStage& stage = *effectStages[e];
 
         CodeStage::AutoStageRestore csar(&fCodeStage, &stage);
 
-        if (inColor.isZeros()) {
-            SkString inColorName;
-
-            // Effects have no way to communicate zeros, they treat an empty string as ones.
-            this->nameVariable(&inColorName, '\0', "input");
-            this->fsCodeAppendf("\tvec4 %s = %s;\n", inColorName.c_str(), inColor.c_str());
-            inColor = inColorName;
-        }
-
         // create var to hold stage result
         SkString outColorName;
         this->nameVariable(&outColorName, '\0', "output");
         this->fsCodeAppendf("\tvec4 %s;\n", outColorName.c_str());
-        outColor = outColorName;
-
 
         programEffectsBuilder->emitEffect(stage,
                                           effectKeys[e],
-                                          outColor.c_str(),
-                                          inColor.isOnes() ? NULL : inColor.c_str(),
+                                          outColorName.c_str(),
+                                          *fsInOutColor,
                                           fCodeStage.stageIndex());
 
-        inColor = outColor;
-        effectEmitted = true;
-    }
-
-    if (effectEmitted) {
-        *fsInOutColor = outColor;
+        *fsInOutColor = GrGLSLExpr4(outColorName);
     }
 }
 
@@ -747,7 +726,7 @@ GrGLFullShaderBuilder::GrGLFullShaderBuilder(GrGpuGL* gpu,
         const char *vsName, *fsName;
         this->addVarying(kVec4f_GrSLType, "Color", &vsName, &fsName);
         this->vsCodeAppendf("\t%s = %s;\n", vsName, color_attribute_name());
-        this->setInputColor(fsName);
+        this->setInputColor(GrGLSLExpr4(fsName));
     }
 
     if (GrGLProgramDesc::kAttribute_ColorInput == header.fCoverageInput) {
@@ -755,7 +734,7 @@ GrGLFullShaderBuilder::GrGLFullShaderBuilder(GrGpuGL* gpu,
         const char *vsName, *fsName;
         this->addVarying(kVec4f_GrSLType, "Coverage", &vsName, &fsName);
         this->vsCodeAppendf("\t%s = %s;\n", vsName, coverage_attribute_name());
-        this->setInputCoverage(fsName);
+        this->setInputCoverage(GrGLSLExpr4(fsName));
     }
 }