Re-land of "eliminated GrGLSLExpr".

This change is exactly the same as the last time it was landed; I believe the
underlying optimizer bug that was causing this to cause problems has been
fixed by a prior CL.
Bug: skia:
Change-Id: I5436422f094ea758caa3cd69e9338db31b1f93fa
Reviewed-on: https://skia-review.googlesource.com/15768
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>

25 files changed, 88 insertions, 116 deletions

diff --git a/src/core/SkLightingShader.cpp b/src/core/SkLightingShader.cpp
index 600134ded3..0442913025 100644
--- a/src/core/SkLightingShader.cpp
+++ b/src/core/SkLightingShader.cpp
@@ -168,7 +168,7 @@ public:
             fragBuilder->codeAppendf("vec4 diffuseColor = %s;", args.fInputColor);
 
             SkString dstNormalName("dstNormal");
-            this->emitChild(0, nullptr, &dstNormalName, args);
+            this->emitChild(0, &dstNormalName, args);
 
             fragBuilder->codeAppendf("vec3 normal = %s.xyz;", dstNormalName.c_str());
 
diff --git a/src/core/SkNormalMapSource.cpp b/src/core/SkNormalMapSource.cpp
index 65c5c89268..fb133da1b7 100644
--- a/src/core/SkNormalMapSource.cpp
+++ b/src/core/SkNormalMapSource.cpp
@@ -47,7 +47,7 @@ public:
                                                    kDefault_GrSLPrecision, "Xform", &xformUniName);
 
             SkString dstNormalColorName("dstNormalColor");
-            this->emitChild(0, nullptr, &dstNormalColorName, args);
+            this->emitChild(0, &dstNormalColorName, args);
             fragBuilder->codeAppendf("vec3 normal = normalize(%s.rgb - vec3(0.5));",
                                      dstNormalColorName.c_str());
 
diff --git a/src/effects/GrAlphaThresholdFragmentProcessor.cpp b/src/effects/GrAlphaThresholdFragmentProcessor.cpp
index 6c355c1fee..de1b74e4ce 100644
--- a/src/effects/GrAlphaThresholdFragmentProcessor.cpp
+++ b/src/effects/GrAlphaThresholdFragmentProcessor.cpp
@@ -127,8 +127,7 @@ void GrGLAlphaThresholdFragmentProcessor::emitCode(EmitArgs& args) {
                             "color.a = inner_thresh;"
                             "}");
 
-    fragBuilder->codeAppendf("%s = %s;", args.fOutputColor,
-                             (GrGLSLExpr4(args.fInputColor) * GrGLSLExpr4("color")).c_str());
+    fragBuilder->codeAppendf("%s = %s * color;", args.fOutputColor, args.fInputColor);
 }
 
 void GrGLAlphaThresholdFragmentProcessor::onSetData(const GrGLSLProgramDataManager& pdman,
diff --git a/src/effects/SkArithmeticImageFilter.cpp b/src/effects/SkArithmeticImageFilter.cpp
index a80ce19c78..d9c2b60b1a 100644
--- a/src/effects/SkArithmeticImageFilter.cpp
+++ b/src/effects/SkArithmeticImageFilter.cpp
@@ -238,7 +238,7 @@ private:
 
                 GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
                 SkString dstColor("dstColor");
-                this->emitChild(0, nullptr, &dstColor, args);
+                this->emitChild(0, &dstColor, args);
 
                 fKUni = args.fUniformHandler->addUniform(kFragment_GrShaderFlag, kVec4f_GrSLType,
                                                          kDefault_GrSLPrecision, "k");
diff --git a/src/effects/SkLightingImageFilter.cpp b/src/effects/SkLightingImageFilter.cpp
index cd2a36e7d7..e6c4661e02 100644
--- a/src/effects/SkLightingImageFilter.cpp
+++ b/src/effects/SkLightingImageFilter.cpp
@@ -1915,9 +1915,7 @@ void GrGLLightingEffect::emitCode(EmitArgs& args) {
                              args.fOutputColor, lightFunc.c_str(), normalName.c_str(), surfScale);
     fLight->emitLightColor(uniformHandler, fragBuilder, "surfaceToLight");
     fragBuilder->codeAppend(");\n");
-    SkString modulate;
-    GrGLSLMulVarBy4f(&modulate, args.fOutputColor, args.fInputColor);
-    fragBuilder->codeAppend(modulate.c_str());
+    fragBuilder->codeAppendf("%s *= %s;\n", args.fOutputColor, args.fInputColor);
 }
 
 void GrGLLightingEffect::GenKey(const GrProcessor& proc,
diff --git a/src/effects/SkMagnifierImageFilter.cpp b/src/effects/SkMagnifierImageFilter.cpp
index 8552c8113e..8e289e5c4c 100644
--- a/src/effects/SkMagnifierImageFilter.cpp
+++ b/src/effects/SkMagnifierImageFilter.cpp
@@ -196,10 +196,8 @@ void GrGLMagnifierEffect::emitCode(EmitArgs& args) {
                                      &fColorSpaceHelper);
     fragBuilder->codeAppend(";\n");
 
-    fragBuilder->codeAppendf("\t\t%s = output_color;", args.fOutputColor);
-    SkString modulate;
-    GrGLSLMulVarBy4f(&modulate, args.fOutputColor, args.fInputColor);
-    fragBuilder->codeAppend(modulate.c_str());
+    fragBuilder->codeAppendf("\t\t%s = output_color;\n", args.fOutputColor);
+    fragBuilder->codeAppendf("%s *= %s;\n", args.fOutputColor, args.fInputColor);
 }
 
 void GrGLMagnifierEffect::onSetData(const GrGLSLProgramDataManager& pdman,
diff --git a/src/effects/SkMorphologyImageFilter.cpp b/src/effects/SkMorphologyImageFilter.cpp
index d11b4da60e..e783488e7b 100644
--- a/src/effects/SkMorphologyImageFilter.cpp
+++ b/src/effects/SkMorphologyImageFilter.cpp
@@ -276,9 +276,7 @@ void GrGLMorphologyEffect::emitCode(EmitArgs& args) {
         fragBuilder->codeAppendf("\t\t\tcoord.%s = min(highBound, coord.%s);", dir, dir);
     }
     fragBuilder->codeAppend("\t\t}\n");
-    SkString modulate;
-    GrGLSLMulVarBy4f(&modulate, args.fOutputColor, args.fInputColor);
-    fragBuilder->codeAppend(modulate.c_str());
+    fragBuilder->codeAppendf("%s *= %s;\n", args.fOutputColor, args.fInputColor);
 }
 
 void GrGLMorphologyEffect::GenKey(const GrProcessor& proc,
diff --git a/src/effects/gradients/SkGradientShader.cpp b/src/effects/gradients/SkGradientShader.cpp
index 3be6c1ba9e..9ecc84ec65 100644
--- a/src/effects/gradients/SkGradientShader.cpp
+++ b/src/effects/gradients/SkGradientShader.cpp
@@ -1583,8 +1583,7 @@ void GrGradientEffect::GLSLProcessor::emitColor(GrGLSLFPFragmentBuilder* fragBui
             if (ge.fColorSpaceXform) {
                 fragBuilder->codeAppend("colorTemp.rgb = clamp(colorTemp.rgb, 0, colorTemp.a);");
             }
-            fragBuilder->codeAppendf("%s = %s;", outputColor,
-                                     (GrGLSLExpr4(inputColor) * GrGLSLExpr4("colorTemp")).c_str());
+            fragBuilder->codeAppendf("%s = %s * colorTemp;", outputColor, inputColor);
 
             break;
         }
@@ -1622,8 +1621,7 @@ void GrGradientEffect::GLSLProcessor::emitColor(GrGLSLFPFragmentBuilder* fragBui
             if (ge.fColorSpaceXform) {
                 fragBuilder->codeAppend("colorTemp.rgb = clamp(colorTemp.rgb, 0, colorTemp.a);");
             }
-            fragBuilder->codeAppendf("%s = %s;", outputColor,
-                                     (GrGLSLExpr4(inputColor) * GrGLSLExpr4("colorTemp")).c_str());
+            fragBuilder->codeAppendf("%s = %s * colorTemp;", outputColor, inputColor);
 
             break;
         }
@@ -1661,8 +1659,7 @@ void GrGradientEffect::GLSLProcessor::emitColor(GrGLSLFPFragmentBuilder* fragBui
             if (ge.fColorSpaceXform) {
                 fragBuilder->codeAppend("colorTemp.rgb = clamp(colorTemp.rgb, 0, colorTemp.a);");
             }
-            fragBuilder->codeAppendf("%s = %s;", outputColor,
-                                     (GrGLSLExpr4(inputColor) * GrGLSLExpr4("colorTemp")).c_str());
+            fragBuilder->codeAppendf("%s = %s * colorTemp;", outputColor, inputColor);
 
             break;
         }
@@ -1688,8 +1685,7 @@ void GrGradientEffect::GLSLProcessor::emitColor(GrGLSLFPFragmentBuilder* fragBui
                 fragBuilder->codeAppend("colorTemp.rgb = clamp(colorTemp.rgb, 0, colorTemp.a);");
             }
 
-            fragBuilder->codeAppendf("%s = %s;", outputColor,
-                                     (GrGLSLExpr4(inputColor) * GrGLSLExpr4("colorTemp")).c_str());
+            fragBuilder->codeAppendf("%s = %s * colorTemp;", outputColor, inputColor);
 
             break;
         }
@@ -1720,8 +1716,7 @@ void GrGradientEffect::GLSLProcessor::emitColor(GrGLSLFPFragmentBuilder* fragBui
                 fragBuilder->codeAppend("colorTemp.rgb = clamp(colorTemp.rgb, 0, colorTemp.a);");
             }
 
-            fragBuilder->codeAppendf("%s = %s;", outputColor,
-                                     (GrGLSLExpr4(inputColor) * GrGLSLExpr4("colorTemp")).c_str());
+            fragBuilder->codeAppendf("%s = %s * colorTemp;", outputColor, inputColor);
 
             break;
         }
diff --git a/src/gpu/GrFragmentProcessor.cpp b/src/gpu/GrFragmentProcessor.cpp
index c22316d011..b0a36fce6d 100644
--- a/src/gpu/GrFragmentProcessor.cpp
+++ b/src/gpu/GrFragmentProcessor.cpp
@@ -287,7 +287,7 @@ sk_sp<GrFragmentProcessor> GrFragmentProcessor::MakeInputPremulAndMulByOutput(
             public:
                 void emitCode(EmitArgs& args) override {
                     GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
-                    this->emitChild(0, nullptr, args);
+                    this->emitChild(0, args);
                     fragBuilder->codeAppendf("%s.rgb *= %s.rgb;", args.fOutputColor,
                                                                 args.fInputColor);
                     fragBuilder->codeAppendf("%s *= %s.a;", args.fOutputColor, args.fInputColor);
diff --git a/src/gpu/effects/GrBicubicEffect.cpp b/src/gpu/effects/GrBicubicEffect.cpp
index c60400e383..70a00965af 100644
--- a/src/gpu/effects/GrBicubicEffect.cpp
+++ b/src/gpu/effects/GrBicubicEffect.cpp
@@ -112,9 +112,8 @@ void GrGLBicubicEffect::emitCode(EmitArgs& args) {
         fragBuilder->appendColorGamutXform(&xformedColor, bicubicColor.c_str(), &fColorSpaceHelper);
         bicubicColor.swap(xformedColor);
     }
-    fragBuilder->codeAppendf("%s = %s;",
-                             args.fOutputColor, (GrGLSLExpr4(bicubicColor.c_str()) *
-                                                 GrGLSLExpr4(args.fInputColor)).c_str());
+    fragBuilder->codeAppendf("%s = %s * %s;", args.fOutputColor, bicubicColor.c_str(),
+                             args.fInputColor);
 }
 
 void GrGLBicubicEffect::onSetData(const GrGLSLProgramDataManager& pdman,
diff --git a/src/gpu/effects/GrConvexPolyEffect.cpp b/src/gpu/effects/GrConvexPolyEffect.cpp
index 312c038201..4b9599ef32 100644
--- a/src/gpu/effects/GrConvexPolyEffect.cpp
+++ b/src/gpu/effects/GrConvexPolyEffect.cpp
@@ -132,8 +132,7 @@ void GLAARectEffect::emitCode(EmitArgs& args) {
     if (GrProcessorEdgeTypeIsInverseFill(aare.getEdgeType())) {
         fragBuilder->codeAppend("\t\talpha = 1.0 - alpha;\n");
     }
-    fragBuilder->codeAppendf("\t\t%s = %s;\n", args.fOutputColor,
-                             (GrGLSLExpr4(args.fInputColor) * GrGLSLExpr1("alpha")).c_str());
+    fragBuilder->codeAppendf("\t\t%s = %s * alpha;\n", args.fOutputColor, args.fInputColor);
 }
 
 void GLAARectEffect::onSetData(const GrGLSLProgramDataManager& pdman,
@@ -212,8 +211,7 @@ void GrGLConvexPolyEffect::emitCode(EmitArgs& args) {
     if (GrProcessorEdgeTypeIsInverseFill(cpe.getEdgeType())) {
         fragBuilder->codeAppend("\talpha = 1.0 - alpha;\n");
     }
-    fragBuilder->codeAppendf("\t%s = %s;\n", args.fOutputColor,
-                             (GrGLSLExpr4(args.fInputColor) * GrGLSLExpr1("alpha")).c_str());
+    fragBuilder->codeAppendf("\t%s = %s * alpha;\n", args.fOutputColor, args.fInputColor);
 }
 
 void GrGLConvexPolyEffect::onSetData(const GrGLSLProgramDataManager& pdman,
diff --git a/src/gpu/effects/GrDitherEffect.cpp b/src/gpu/effects/GrDitherEffect.cpp
index 864a5d2d81..0686750196 100644
--- a/src/gpu/effects/GrDitherEffect.cpp
+++ b/src/gpu/effects/GrDitherEffect.cpp
@@ -74,7 +74,7 @@ void GLDitherEffect::emitCode(EmitArgs& args) {
                              "fract(sin(dot(sk_FragCoord.xy, vec2(12.9898,78.233))) * "
                                                             "43758.5453);\n");
     fragBuilder->codeAppendf("\t\t%s = clamp((1.0/255.0) * vec4(r, r, r, r) + %s, 0, 1);\n",
-                             args.fOutputColor, GrGLSLExpr4(args.fInputColor).c_str());
+                             args.fOutputColor, args.fInputColor);
 }
 
 //////////////////////////////////////////////////////////////////////////////
diff --git a/src/gpu/effects/GrGaussianConvolutionFragmentProcessor.cpp b/src/gpu/effects/GrGaussianConvolutionFragmentProcessor.cpp
index b4f13143d8..324c61efeb 100644
--- a/src/gpu/effects/GrGaussianConvolutionFragmentProcessor.cpp
+++ b/src/gpu/effects/GrGaussianConvolutionFragmentProcessor.cpp
@@ -91,10 +91,7 @@ void GrGLConvolutionEffect::emitCode(EmitArgs& args) {
         }
         fragBuilder->codeAppendf("coord += %s;\n", imgInc);
     }
-
-    SkString modulate;
-    GrGLSLMulVarBy4f(&modulate, args.fOutputColor, args.fInputColor);
-    fragBuilder->codeAppend(modulate.c_str());
+    fragBuilder->codeAppendf("%s *= %s;\n", args.fOutputColor, args.fInputColor);
 }
 
 void GrGLConvolutionEffect::onSetData(const GrGLSLProgramDataManager& pdman,
diff --git a/src/gpu/effects/GrMatrixConvolutionEffect.cpp b/src/gpu/effects/GrMatrixConvolutionEffect.cpp
index 03d90ea675..b3ea81a643 100644
--- a/src/gpu/effects/GrMatrixConvolutionEffect.cpp
+++ b/src/gpu/effects/GrMatrixConvolutionEffect.cpp
@@ -114,10 +114,7 @@ void GrGLMatrixConvolutionEffect::emitCode(EmitArgs& args) {
         fragBuilder->codeAppendf("%s.rgb = clamp(sum.rgb * %s + %s, 0, 1);", args.fOutputColor, gain, bias);
         fragBuilder->codeAppendf("%s.rgb *= %s.a;", args.fOutputColor, args.fOutputColor);
     }
-
-    SkString modulate;
-    GrGLSLMulVarBy4f(&modulate, args.fOutputColor, args.fInputColor);
-    fragBuilder->codeAppend(modulate.c_str());
+    fragBuilder->codeAppendf("%s *= %s;\n", args.fOutputColor, args.fInputColor);
 }
 
 void GrGLMatrixConvolutionEffect::GenKey(const GrProcessor& processor,
diff --git a/src/gpu/effects/GrOvalEffect.cpp b/src/gpu/effects/GrOvalEffect.cpp
index 672f5d873c..2eb1d85b1e 100644
--- a/src/gpu/effects/GrOvalEffect.cpp
+++ b/src/gpu/effects/GrOvalEffect.cpp
@@ -140,8 +140,7 @@ void GLCircleEffect::emitCode(EmitArgs& args) {
         fragBuilder->codeAppend("d = d > 0.5 ? 1.0 : 0.0;");
     }
 
-    fragBuilder->codeAppendf("%s = %s;", args.fOutputColor,
-                             (GrGLSLExpr4(args.fInputColor) * GrGLSLExpr1("d")).c_str());
+    fragBuilder->codeAppendf("%s = %s * d;", args.fOutputColor, args.fInputColor);
 }
 
 void GLCircleEffect::GenKey(const GrProcessor& processor, const GrShaderCaps&,
@@ -333,8 +332,7 @@ void GLEllipseEffect::emitCode(EmitArgs& args) {
             SkFAIL("Hairline not expected here.");
     }
 
-    fragBuilder->codeAppendf("%s = %s;", args.fOutputColor,
-                             (GrGLSLExpr4(args.fInputColor) * GrGLSLExpr1("alpha")).c_str());
+    fragBuilder->codeAppendf("%s = %s * alpha;", args.fOutputColor, args.fInputColor);
 }
 
 void GLEllipseEffect::GenKey(const GrProcessor& effect, const GrShaderCaps&,
diff --git a/src/gpu/effects/GrRRectEffect.cpp b/src/gpu/effects/GrRRectEffect.cpp
index 887bc00bda..8d18150a46 100644
--- a/src/gpu/effects/GrRRectEffect.cpp
+++ b/src/gpu/effects/GrRRectEffect.cpp
@@ -279,8 +279,7 @@ void GLCircularRRectEffect::emitCode(EmitArgs& args) {
         fragBuilder->codeAppend("alpha = 1.0 - alpha;");
     }
 
-    fragBuilder->codeAppendf("%s = %s;", args.fOutputColor,
-                             (GrGLSLExpr4(args.fInputColor) * GrGLSLExpr1("alpha")).c_str());
+    fragBuilder->codeAppendf("%s = %s * alpha;", args.fOutputColor, args.fInputColor);
 }
 
 void GLCircularRRectEffect::GenKey(const GrProcessor& processor, const GrShaderCaps&,
@@ -590,8 +589,7 @@ void GLEllipticalRRectEffect::emitCode(EmitArgs& args) {
         fragBuilder->codeAppend("float alpha = clamp(0.5 + approx_dist, 0.0, 1.0);");
     }
 
-    fragBuilder->codeAppendf("%s = %s;", args.fOutputColor,
-                             (GrGLSLExpr4(args.fInputColor) * GrGLSLExpr1("alpha")).c_str());
+    fragBuilder->codeAppendf("%s = %s * alpha;", args.fOutputColor, args.fInputColor);
 }
 
 void GLEllipticalRRectEffect::GenKey(const GrProcessor& effect, const GrShaderCaps&,
diff --git a/src/gpu/effects/GrXfermodeFragmentProcessor.cpp b/src/gpu/effects/GrXfermodeFragmentProcessor.cpp
index 30a9faaf08..aa799370a3 100644
--- a/src/gpu/effects/GrXfermodeFragmentProcessor.cpp
+++ b/src/gpu/effects/GrXfermodeFragmentProcessor.cpp
@@ -415,7 +415,7 @@ public:
         ComposeOneFragmentProcessor::Child child =
             args.fFp.cast<ComposeOneFragmentProcessor>().child();
         SkString childColor("child");
-        this->emitChild(0, nullptr, &childColor, args);
+        this->emitChild(0, &childColor, args);
 
         const char* inputColor = args.fInputColor;
         // We don't try to optimize for this case at all
diff --git a/src/gpu/gl/builders/GrGLProgramBuilder.cpp b/src/gpu/gl/builders/GrGLProgramBuilder.cpp
index 8e662b971c..79cb2cab83 100644
--- a/src/gpu/gl/builders/GrGLProgramBuilder.cpp
+++ b/src/gpu/gl/builders/GrGLProgramBuilder.cpp
@@ -42,12 +42,7 @@ GrGLProgram* GrGLProgramBuilder::CreateProgram(const GrPipeline& pipeline,
     // uniforms, varyings, textures, etc
     GrGLProgramBuilder builder(gpu, pipeline, primProc, desc);
 
-    // TODO: Once all stages can handle taking a float or vec4 and correctly handling them we can
-    // seed correctly here
-    GrGLSLExpr4 inputColor;
-    GrGLSLExpr4 inputCoverage;
-
-    if (!builder.emitAndInstallProcs(&inputColor, &inputCoverage)) {
+    if (!builder.emitAndInstallProcs()) {
         builder.cleanupFragmentProcessors();
         return nullptr;
     }
diff --git a/src/gpu/glsl/GrGLSL.cpp b/src/gpu/glsl/GrGLSL.cpp
index d54ddee0d6..76ffb826a7 100644
--- a/src/gpu/glsl/GrGLSL.cpp
+++ b/src/gpu/glsl/GrGLSL.cpp
@@ -45,15 +45,3 @@ void GrGLSLAppendDefaultFloatPrecisionDeclaration(GrSLPrecision p,
         }
     }
 }
-
-void GrGLSLMulVarBy4f(SkString* outAppend, const char* vec4VarName, const GrGLSLExpr4& mulFactor) {
-    if (mulFactor.isOnes()) {
-        *outAppend = SkString();
-    }
-
-    if (mulFactor.isZeros()) {
-        outAppend->appendf("%s = vec4(0);", vec4VarName);
-    } else {
-        outAppend->appendf("%s *= %s;", vec4VarName, mulFactor.c_str());
-    }
-}
diff --git a/src/gpu/glsl/GrGLSLFragmentProcessor.cpp b/src/gpu/glsl/GrGLSLFragmentProcessor.cpp
index a4459d23f6..28e5a211a8 100644
--- a/src/gpu/glsl/GrGLSLFragmentProcessor.cpp
+++ b/src/gpu/glsl/GrGLSLFragmentProcessor.cpp
@@ -26,7 +26,6 @@ void GrGLSLFragmentProcessor::emitChild(int childIndex, const char* inputColor,
 
 void GrGLSLFragmentProcessor::emitChild(int childIndex, const char* inputColor,
                                         SkString* outputColor, EmitArgs& args) {
-
     SkASSERT(outputColor);
     GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
     outputColor->append(fragBuilder->getMangleString());
@@ -36,6 +35,7 @@ void GrGLSLFragmentProcessor::emitChild(int childIndex, const char* inputColor,
 
 void GrGLSLFragmentProcessor::internalEmitChild(int childIndex, const char* inputColor,
                                                 const char* outputColor, EmitArgs& args) {
+    SkASSERT(inputColor);
     GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
 
     fragBuilder->onBeforeChildProcEmitCode();  // call first so mangleString is updated
diff --git a/src/gpu/glsl/GrGLSLFragmentProcessor.h b/src/gpu/glsl/GrGLSLFragmentProcessor.h
index 0d53196da8..fe7775a9c4 100644
--- a/src/gpu/glsl/GrGLSLFragmentProcessor.h
+++ b/src/gpu/glsl/GrGLSLFragmentProcessor.h
@@ -157,6 +157,10 @@ public:
         return fChildProcessors[index];
     }
 
+    inline void emitChild(int childIndex, SkString* outputColor, EmitArgs& parentArgs) {
+        this->emitChild(childIndex, "vec4(1.0)", outputColor, parentArgs);
+    }
+
     /** Will emit the code of a child proc in its own scope. Pass in the parent's EmitArgs and
      *  emitChild will automatically extract the coords and samplers of that child and pass them
      *  on to the child's emitCode(). Also, any uniforms or functions emitted by the child will
@@ -168,6 +172,10 @@ public:
     void emitChild(int childIndex, const char* inputColor, SkString* outputColor,
                    EmitArgs& parentArgs);
 
+    inline void emitChild(int childIndex, EmitArgs& args) {
+        this->emitChild(childIndex, "vec4(1.0)", args);
+    }
+
     /** Variation that uses the parent's output color variable to hold the child's output.*/
     void emitChild(int childIndex, const char* inputColor, EmitArgs& parentArgs);
 
diff --git a/src/gpu/glsl/GrGLSLProgramBuilder.cpp b/src/gpu/glsl/GrGLSLProgramBuilder.cpp
index 7a8cbad3a0..5c3bee1b4e 100644
--- a/src/gpu/glsl/GrGLSLProgramBuilder.cpp
+++ b/src/gpu/glsl/GrGLSLProgramBuilder.cpp
@@ -53,24 +53,24 @@ void GrGLSLProgramBuilder::addFeature(GrShaderFlags shaders,
     }
 }
 
-bool GrGLSLProgramBuilder::emitAndInstallProcs(GrGLSLExpr4* inputColor,
-                                               GrGLSLExpr4* inputCoverage) {
+bool GrGLSLProgramBuilder::emitAndInstallProcs() {
     // First we loop over all of the installed processors and collect coord transforms.  These will
     // be sent to the GrGLSLPrimitiveProcessor in its emitCode function
     const GrPrimitiveProcessor& primProc = this->primitiveProcessor();
 
-    this->emitAndInstallPrimProc(primProc, inputColor, inputCoverage);
-
-    this->emitAndInstallFragProcs(inputColor, inputCoverage);
-    this->emitAndInstallXferProc(*inputColor, *inputCoverage);
+    SkString inputColor;
+    SkString inputCoverage;
+    this->emitAndInstallPrimProc(primProc, &inputColor, &inputCoverage);
+    this->emitAndInstallFragProcs(&inputColor, &inputCoverage);
+    this->emitAndInstallXferProc(inputColor, inputCoverage);
     this->emitFSOutputSwizzle(this->pipeline().getXferProcessor().hasSecondaryOutput());
 
     return this->checkSamplerCounts() && this->checkImageStorageCounts();
 }
 
 void GrGLSLProgramBuilder::emitAndInstallPrimProc(const GrPrimitiveProcessor& proc,
-                                                  GrGLSLExpr4* outputColor,
-                                                  GrGLSLExpr4* outputCoverage) {
+                                                  SkString* outputColor,
+                                                  SkString* outputCoverage) {
     // Program builders have a bit of state we need to clear with each effect
     AutoStageAdvance adv(this);
     this->nameExpression(outputColor, "outputColor");
@@ -139,16 +139,16 @@ void GrGLSLProgramBuilder::emitAndInstallPrimProc(const GrPrimitiveProcessor& pr
     fFS.codeAppend("}");
 }
 
-void GrGLSLProgramBuilder::emitAndInstallFragProcs(GrGLSLExpr4* color, GrGLSLExpr4* coverage) {
+void GrGLSLProgramBuilder::emitAndInstallFragProcs(SkString* color, SkString* coverage) {
     int transformedCoordVarsIdx = 0;
-    GrGLSLExpr4** inOut = &color;
+    SkString** inOut = &color;
     for (int i = 0; i < this->pipeline().numFragmentProcessors(); ++i) {
         if (i == this->pipeline().numColorFragmentProcessors()) {
             inOut = &coverage;
         }
-        GrGLSLExpr4 output;
+        SkString output;
         const GrFragmentProcessor& fp = this->pipeline().getFragmentProcessor(i);
-        this->emitAndInstallFragProc(fp, i, transformedCoordVarsIdx, **inOut, &output);
+        output = this->emitAndInstallFragProc(fp, i, transformedCoordVarsIdx, **inOut, output);
         GrFragmentProcessor::Iter iter(&fp);
         while (const GrFragmentProcessor* fp = iter.next()) {
             transformedCoordVarsIdx += fp->numCoordTransforms();
@@ -158,15 +158,16 @@ void GrGLSLProgramBuilder::emitAndInstallFragProcs(GrGLSLExpr4* color, GrGLSLExp
 }
 
 // TODO Processors cannot output zeros because an empty string is all 1s
-// the fix is to allow effects to take the GrGLSLExpr4 directly
-void GrGLSLProgramBuilder::emitAndInstallFragProc(const GrFragmentProcessor& fp,
-                                                  int index,
-                                                  int transformedCoordVarsIdx,
-                                                  const GrGLSLExpr4& input,
-                                                  GrGLSLExpr4* output) {
+// the fix is to allow effects to take the SkString directly
+SkString GrGLSLProgramBuilder::emitAndInstallFragProc(const GrFragmentProcessor& fp,
+                                                      int index,
+                                                      int transformedCoordVarsIdx,
+                                                      const SkString& input,
+                                                      SkString output) {
+    SkASSERT(input.size());
     // Program builders have a bit of state we need to clear with each effect
     AutoStageAdvance adv(this);
-    this->nameExpression(output, "output");
+    this->nameExpression(&output, "output");
 
     // Enclose custom code in a block to avoid namespace conflicts
     SkString openBrace;
@@ -193,8 +194,8 @@ void GrGLSLProgramBuilder::emitAndInstallFragProc(const GrFragmentProcessor& fp,
                                            this->uniformHandler(),
                                            this->shaderCaps(),
                                            fp,
-                                           output->c_str(),
-                                           input.isOnes() ? nullptr : input.c_str(),
+                                           output.c_str(),
+                                           input.c_str(),
                                            coords,
                                            textureSamplers,
                                            texelBuffers,
@@ -209,10 +210,11 @@ void GrGLSLProgramBuilder::emitAndInstallFragProc(const GrFragmentProcessor& fp,
     fFragmentProcessors.push_back(fragProc);
 
     fFS.codeAppend("}");
+    return output;
 }
 
-void GrGLSLProgramBuilder::emitAndInstallXferProc(const GrGLSLExpr4& colorIn,
-                                                  const GrGLSLExpr4& coverageIn) {
+void GrGLSLProgramBuilder::emitAndInstallXferProc(const SkString& colorIn,
+                                                  const SkString& coverageIn) {
     // Program builders have a bit of state we need to clear with each effect
     AutoStageAdvance adv(this);
 
@@ -249,8 +251,8 @@ void GrGLSLProgramBuilder::emitAndInstallXferProc(const GrGLSLExpr4& colorIn,
                                        this->uniformHandler(),
                                        this->shaderCaps(),
                                        xp,
-                                       colorIn.c_str(),
-                                       coverageIn.c_str(),
+                                       colorIn.size() ? colorIn.c_str() : "vec4(1)",
+                                       coverageIn.size() ? coverageIn.c_str() : "vec4(1)",
                                        fFS.getPrimaryColorOutputName(),
                                        fFS.getSecondaryColorOutputName(),
                                        dstTextureSamplerHandle,
@@ -455,12 +457,12 @@ void GrGLSLProgramBuilder::nameVariable(SkString* out, char prefix, const char*
     }
 }
 
-void GrGLSLProgramBuilder::nameExpression(GrGLSLExpr4* output, const char* baseName) {
+void GrGLSLProgramBuilder::nameExpression(SkString* output, const char* baseName) {
     // create var to hold stage result.  If we already have a valid output name, just use that
     // otherwise create a new mangled one.  This name is only valid if we are reordering stages
     // and have to tell stage exactly where to put its output.
     SkString outName;
-    if (output->isValid()) {
+    if (output->size()) {
         outName = output->c_str();
     } else {
         this->nameVariable(&outName, '\0', baseName);
diff --git a/src/gpu/glsl/GrGLSLProgramBuilder.h b/src/gpu/glsl/GrGLSLProgramBuilder.h
index f12ba5e925..933d422535 100644
--- a/src/gpu/glsl/GrGLSLProgramBuilder.h
+++ b/src/gpu/glsl/GrGLSLProgramBuilder.h
@@ -22,7 +22,7 @@
 
 class GrShaderVar;
 class GrGLSLVaryingHandler;
-class GrGLSLExpr4;
+class SkString;
 class GrShaderCaps;
 
 typedef SkSTArray<8, GrGLSLFragmentProcessor*, true> GrGLSLFragProcs;
@@ -115,7 +115,7 @@ protected:
 
     void addFeature(GrShaderFlags shaders, uint32_t featureBit, const char* extensionName);
 
-    bool emitAndInstallProcs(GrGLSLExpr4* inputColor, GrGLSLExpr4* inputCoverage);
+    bool emitAndInstallProcs();
 
     void cleanupFragmentProcessors();
 
@@ -145,19 +145,18 @@ private:
     };
 
     // Generates a possibly mangled name for a stage variable and writes it to the fragment shader.
-    // If GrGLSLExpr4 has a valid name then it will use that instead
-    void nameExpression(GrGLSLExpr4*, const char* baseName);
+    void nameExpression(SkString*, const char* baseName);
 
     void emitAndInstallPrimProc(const GrPrimitiveProcessor&,
-                                GrGLSLExpr4* outputColor,
-                                GrGLSLExpr4* outputCoverage);
-    void emitAndInstallFragProcs(GrGLSLExpr4* colorInOut, GrGLSLExpr4* coverageInOut);
-    void emitAndInstallFragProc(const GrFragmentProcessor&,
-                                int index,
-                                int transformedCoordVarsIdx,
-                                const GrGLSLExpr4& input,
-                                GrGLSLExpr4* output);
-    void emitAndInstallXferProc(const GrGLSLExpr4& colorIn, const GrGLSLExpr4& coverageIn);
+                                SkString* outputColor,
+                                SkString* outputCoverage);
+    void emitAndInstallFragProcs(SkString* colorInOut, SkString* coverageInOut);
+    SkString emitAndInstallFragProc(const GrFragmentProcessor&,
+                                    int index,
+                                    int transformedCoordVarsIdx,
+                                    const SkString& input,
+                                    SkString output);
+    void emitAndInstallXferProc(const SkString& colorIn, const SkString& coverageIn);
     void emitSamplersAndImageStorages(const GrResourceIOProcessor& processor,
                                       SkTArray<SamplerHandle>* outTexSamplerHandles,
                                       SkTArray<TexelBufferHandle>* outTexelBufferHandles,
diff --git a/src/gpu/glsl/GrGLSLShaderBuilder.cpp b/src/gpu/glsl/GrGLSLShaderBuilder.cpp
index de7b326917..542cee672c 100644
--- a/src/gpu/glsl/GrGLSLShaderBuilder.cpp
+++ b/src/gpu/glsl/GrGLSLShaderBuilder.cpp
@@ -101,9 +101,17 @@ void GrGLSLShaderBuilder::appendTextureLookupAndModulate(
     if (colorXformHelper && colorXformHelper->isValid()) {
         SkString xform;
         this->appendColorGamutXform(&xform, lookup.c_str(), colorXformHelper);
-        this->codeAppend((GrGLSLExpr4(modulation) * GrGLSLExpr4(xform)).c_str());
+        if (modulation) {
+            this->codeAppendf("%s * %s", modulation, xform.c_str());
+        } else {
+            this->codeAppendf("%s", xform.c_str());
+        }
     } else {
-        this->codeAppend((GrGLSLExpr4(modulation) * GrGLSLExpr4(lookup)).c_str());
+        if (modulation) {
+            this->codeAppendf("%s * %s", modulation, lookup.c_str());
+        } else {
+            this->codeAppendf("%s", lookup.c_str());
+        }
     }
 }
 
diff --git a/src/gpu/vk/GrVkPipelineStateBuilder.cpp b/src/gpu/vk/GrVkPipelineStateBuilder.cpp
index 40c0dfa49a..45b297895f 100644
--- a/src/gpu/vk/GrVkPipelineStateBuilder.cpp
+++ b/src/gpu/vk/GrVkPipelineStateBuilder.cpp
@@ -25,10 +25,7 @@ GrVkPipelineState* GrVkPipelineStateBuilder::CreatePipelineState(
     // uniforms, varyings, textures, etc
     GrVkPipelineStateBuilder builder(gpu, pipeline, primProc, desc);
 
-    GrGLSLExpr4 inputColor;
-    GrGLSLExpr4 inputCoverage;
-
-    if (!builder.emitAndInstallProcs(&inputColor, &inputCoverage)) {
+    if (!builder.emitAndInstallProcs()) {
         builder.cleanupFragmentProcessors();
         return nullptr;
     }