Revert "Revert "Revert "eliminated GrGLSLExpr"""

This reverts commit 796001c82e.

Reason for revert: looks to be causing problems in Chrome (https://storage.googleapis.com/chromium-layout-test-archives/WebKit_Linux_Trusty__dbg_/1553/layout-test-results/results.html)

Original change's description:
> Revert "Revert "eliminated GrGLSLExpr""
> 
> This reverts commit 5e550ab57e.
> 
> Bug: skia:
> Change-Id: I4705e47dbd209aa8f43db3d28c856bd3aa9e49ab
> Reviewed-on: https://skia-review.googlesource.com/15187
> Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
> Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
> 

TBR=ethannicholas@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Change-Id: I6455a4f16b2dc0d6d1265541f7117e0cfb8dd91c
Reviewed-on: https://skia-review.googlesource.com/15309
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>

gn/gpu.gni

@@ -38,6 +38,7 @@ skia_gpu_sources = [
   # Private includes
   "$_include/private/GrAuditTrail.h",
   "$_include/private/GrGLSL.h",
+  "$_include/private/GrGLSL_impl.h",
   "$_include/private/GrInstancedPipelineInfo.h",
   "$_include/private/GrSingleOwner.h",
   "$_include/private/GrRenderTargetProxy.h",

include/private/GrGLSL.h

@@ -138,4 +138,245 @@ static inline const char* GrGLSLTypeString(GrSLType t) {
     return ""; // suppress warning
 }
 
+/** A generic base-class representing a GLSL expression.
+ * The instance can be a variable name, expression or vecN(0) or vecN(1). Does simple constant
+ * folding with help of 1 and 0.
+ *
+ * Clients should not use this class, rather the specific instantiations defined
+ * later, for example GrGLSLExpr4.
+ */
+template <typename Self>
+class GrGLSLExpr {
+public:
+    bool isOnes() const { return kOnes_ExprType == fType; }
+    bool isZeros() const { return kZeros_ExprType == fType; }
+
+    const char* c_str() const {
+        if (kZeros_ExprType == fType) {
+            return Self::ZerosStr();
+        } else if (kOnes_ExprType == fType) {
+            return Self::OnesStr();
+        }
+        SkASSERT(!fExpr.isEmpty()); // Empty expressions should not be used.
+        return fExpr.c_str();
+    }
+
+    bool isValid() const {
+        return kFullExpr_ExprType != fType || !fExpr.isEmpty();
+    }
+
+protected:
+    /** Constructs an invalid expression.
+     * Useful only as a return value from functions that never actually return
+     * this and instances that will be assigned to later. */
+    GrGLSLExpr()
+        : fType(kFullExpr_ExprType) {
+        // The only constructor that is allowed to build an empty expression.
+        SkASSERT(!this->isValid());
+    }
+
+    /** Constructs an expression with all components as value v */
+    explicit GrGLSLExpr(int v) {
+        if (v == 0) {
+            fType = kZeros_ExprType;
+        } else if (v == 1) {
+            fType = kOnes_ExprType;
+        } else {
+            fType = kFullExpr_ExprType;
+            fExpr.appendf(Self::CastIntStr(), v);
+        }
+    }
+
+    /** Constructs an expression from a string.
+     * Argument expr is a simple expression or a parenthesized expression. */
+    // TODO: make explicit once effects input Exprs.
+    GrGLSLExpr(const char expr[]) {
+        if (nullptr == expr) {  // TODO: remove this once effects input Exprs.
+            fType = kOnes_ExprType;
+        } else {
+            fType = kFullExpr_ExprType;
+            fExpr = expr;
+        }
+        SkASSERT(this->isValid());
+    }
+
+    /** Constructs an expression from a string.
+     * Argument expr is a simple expression or a parenthesized expression. */
+    // TODO: make explicit once effects input Exprs.
+    GrGLSLExpr(const SkString& expr) {
+        if (expr.isEmpty()) {  // TODO: remove this once effects input Exprs.
+            fType = kOnes_ExprType;
+        } else {
+            fType = kFullExpr_ExprType;
+            fExpr = expr;
+        }
+        SkASSERT(this->isValid());
+    }
+
+    /** Constructs an expression from a string with one substitution. */
+    GrGLSLExpr(const char format[], const char in0[])
+        : fType(kFullExpr_ExprType) {
+        fExpr.appendf(format, in0);
+    }
+
+    /** Constructs an expression from a string with two substitutions. */
+    GrGLSLExpr(const char format[], const char in0[], const char in1[])
+        : fType(kFullExpr_ExprType) {
+        fExpr.appendf(format, in0, in1);
+    }
+
+    /** Returns expression casted to another type.
+     * Generic implementation that is called for non-trivial cases of casts. */
+    template <typename T>
+    static Self VectorCastImpl(const T& other);
+
+    /** Returns a GLSL multiplication: component-wise or component-by-scalar.
+     * The multiplication will be component-wise or multiply each component by a scalar.
+     *
+     * The returned expression will compute the value of:
+     *    vecN(in0.x * in1.x, ...) if dim(T0) == dim(T1) (component-wise)
+     *    vecN(in0.x * in1, ...) if dim(T1) == 1 (vector by scalar)
+     *    vecN(in0 * in1.x, ...) if dim(T0) == 1 (scalar by vector)
+     */
+    template <typename T0, typename T1>
+    static Self Mul(T0 in0, T1 in1);
+
+    /** Returns a GLSL addition: component-wise or add a scalar to each component.
+     * Return value computes:
+     *   vecN(in0.x + in1.x, ...) or vecN(in0.x + in1, ...) or vecN(in0 + in1.x, ...).
+     */
+    template <typename T0, typename T1>
+    static Self Add(T0 in0, T1 in1);
+
+    /** Returns a GLSL subtraction: component-wise or subtract compoments by a scalar.
+     * Return value computes
+     *   vecN(in0.x - in1.x, ...) or vecN(in0.x - in1, ...) or vecN(in0 - in1.x, ...).
+     */
+    template <typename T0, typename T1>
+    static Self Sub(T0 in0, T1 in1);
+
+    /** Returns expression that accesses component(s) of the expression.
+     * format should be the form "%s.x" where 'x' is the component(s) to access.
+     * Caller is responsible for making sure the amount of components in the
+     * format string is equal to dim(T).
+     */
+    template <typename T>
+    T extractComponents(const char format[]) const;
+
+private:
+    enum ExprType {
+        kZeros_ExprType,
+        kOnes_ExprType,
+        kFullExpr_ExprType,
+    };
+    ExprType fType;
+    SkString fExpr;
+};
+
+class GrGLSLExpr1;
+class GrGLSLExpr4;
+
+/** Class representing a float GLSL expression. */
+class GrGLSLExpr1 : public GrGLSLExpr<GrGLSLExpr1> {
+public:
+    GrGLSLExpr1()
+        : INHERITED() {
+    }
+    explicit GrGLSLExpr1(int v)
+        : INHERITED(v) {
+    }
+    GrGLSLExpr1(const char* expr)
+        : INHERITED(expr) {
+    }
+    GrGLSLExpr1(const SkString& expr)
+        : INHERITED(expr) {
+    }
+
+    static GrGLSLExpr1 VectorCast(const GrGLSLExpr1& expr);
+
+private:
+    GrGLSLExpr1(const char format[], const char in0[])
+        : INHERITED(format, in0) {
+    }
+    GrGLSLExpr1(const char format[], const char in0[], const char in1[])
+        : INHERITED(format, in0, in1) {
+    }
+
+    static const char* ZerosStr();
+    static const char* OnesStr();
+    static const char* CastStr();
+    static const char* CastIntStr();
+
+    friend GrGLSLExpr1 operator*(const GrGLSLExpr1& in0, const GrGLSLExpr1&in1);
+    friend GrGLSLExpr1 operator+(const GrGLSLExpr1& in0, const GrGLSLExpr1&in1);
+    friend GrGLSLExpr1 operator-(const GrGLSLExpr1& in0, const GrGLSLExpr1&in1);
+
+    friend class GrGLSLExpr<GrGLSLExpr1>;
+    friend class GrGLSLExpr<GrGLSLExpr4>;
+
+    typedef GrGLSLExpr<GrGLSLExpr1> INHERITED;
+};
+
+/** Class representing a float vector (vec4) GLSL expression. */
+class GrGLSLExpr4 : public GrGLSLExpr<GrGLSLExpr4> {
+public:
+    GrGLSLExpr4()
+        : INHERITED() {
+    }
+    explicit GrGLSLExpr4(int v)
+        : INHERITED(v) {
+    }
+    GrGLSLExpr4(const char* expr)
+        : INHERITED(expr) {
+    }
+    GrGLSLExpr4(const SkString& expr)
+        : INHERITED(expr) {
+    }
+
+    typedef GrGLSLExpr1 AExpr;
+    AExpr a() const;
+
+    /** GLSL vec4 cast / constructor, eg vec4(floatv) -> vec4(floatv, floatv, floatv, floatv) */
+    static GrGLSLExpr4 VectorCast(const GrGLSLExpr1& expr);
+    static GrGLSLExpr4 VectorCast(const GrGLSLExpr4& expr);
+
+private:
+    GrGLSLExpr4(const char format[], const char in0[])
+        : INHERITED(format, in0) {
+    }
+    GrGLSLExpr4(const char format[], const char in0[], const char in1[])
+        : INHERITED(format, in0, in1) {
+    }
+
+    static const char* ZerosStr();
+    static const char* OnesStr();
+    static const char* CastStr();
+    static const char* CastIntStr();
+
+    // The vector-by-scalar and scalar-by-vector binary operations.
+    friend GrGLSLExpr4 operator*(const GrGLSLExpr1& in0, const GrGLSLExpr4&in1);
+    friend GrGLSLExpr4 operator+(const GrGLSLExpr1& in0, const GrGLSLExpr4&in1);
+    friend GrGLSLExpr4 operator-(const GrGLSLExpr1& in0, const GrGLSLExpr4&in1);
+    friend GrGLSLExpr4 operator*(const GrGLSLExpr4& in0, const GrGLSLExpr1&in1);
+    friend GrGLSLExpr4 operator+(const GrGLSLExpr4& in0, const GrGLSLExpr1&in1);
+    friend GrGLSLExpr4 operator-(const GrGLSLExpr4& in0, const GrGLSLExpr1&in1);
+
+    // The vector-by-vector, i.e. component-wise, binary operations.
+    friend GrGLSLExpr4 operator*(const GrGLSLExpr4& in0, const GrGLSLExpr4&in1);
+    friend GrGLSLExpr4 operator+(const GrGLSLExpr4& in0, const GrGLSLExpr4&in1);
+    friend GrGLSLExpr4 operator-(const GrGLSLExpr4& in0, const GrGLSLExpr4&in1);
+
+    friend class GrGLSLExpr<GrGLSLExpr4>;
+
+    typedef GrGLSLExpr<GrGLSLExpr4> INHERITED;
+};
+
+/**
+ * Does an inplace mul, *=, of vec4VarName by mulFactor.
+ * A semicolon is added after the assignment.
+ */
+void GrGLSLMulVarBy4f(SkString* outAppend, const char* vec4VarName, const GrGLSLExpr4& mulFactor);
+
+#include "GrGLSL_impl.h"
+
 #endif

include/private/GrGLSL_impl.h

@@ -0,0 +1,175 @@
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef GrGLSL_impl_DEFINED
+#define GrGLSL_impl_DEFINED
+
+template<typename Self>
+template<typename T>
+inline Self GrGLSLExpr<Self>::VectorCastImpl(const T& expr) {
+    if (expr.isZeros()) {
+        return Self(0);
+    }
+    if (expr.isOnes()) {
+        return Self(1);
+    }
+    return Self(Self::CastStr(), expr.c_str());
+}
+
+template<typename Self>
+template<typename T0, typename T1>
+inline Self GrGLSLExpr<Self>::Mul(T0 in0, T1 in1) {
+    if (in0.isZeros() || in1.isZeros()) {
+        return Self(0);
+    }
+    if (in0.isOnes()) {
+        return Self::VectorCast(in1);
+    }
+    if (in1.isOnes()) {
+        return Self::VectorCast(in0);
+    }
+    return Self("(%s * %s)", in0.c_str(), in1.c_str());
+}
+
+template<typename Self>
+template<typename T0, typename T1>
+inline Self GrGLSLExpr<Self>::Add(T0 in0, T1 in1) {
+    if (in1.isZeros()) {
+        return Self::VectorCast(in0);
+    }
+    if (in0.isZeros()) {
+        return Self::VectorCast(in1);
+    }
+    if (in0.isOnes() && in1.isOnes()) {
+        return Self(2);
+    }
+    return Self("(%s + %s)", in0.c_str(), in1.c_str());
+}
+
+template<typename Self>
+template<typename T0, typename T1>
+inline Self GrGLSLExpr<Self>::Sub(T0 in0, T1 in1) {
+    if (in1.isZeros()) {
+        return Self::VectorCast(in0);
+    }
+    if (in1.isOnes()) {
+        if (in0.isOnes()) {
+            return Self(0);
+        }
+    }
+
+    return Self("(%s - %s)", in0.c_str(), in1.c_str());
+}
+
+template <typename Self>
+template <typename T>
+T GrGLSLExpr<Self>::extractComponents(const char format[]) const {
+    if (this->isZeros()) {
+        return T(0);
+    }
+    if (this->isOnes()) {
+        return T(1);
+    }
+    return T(format, this->c_str());
+}
+
+inline GrGLSLExpr1 GrGLSLExpr1::VectorCast(const GrGLSLExpr1& expr) {
+    return expr;
+}
+
+inline const char* GrGLSLExpr1::ZerosStr() {
+    return "0";
+}
+
+inline const char* GrGLSLExpr1::OnesStr() {
+    return "1.0";
+}
+
+// GrGLSLExpr1::CastStr() is unimplemented because using them is likely an
+// error. This is now caught compile-time.
+
+inline const char* GrGLSLExpr1::CastIntStr() {
+    return "%d";
+}
+
+inline GrGLSLExpr1 operator*(const GrGLSLExpr1& in0, const GrGLSLExpr1& in1) {
+    return GrGLSLExpr1::Mul(in0, in1);
+}
+
+inline GrGLSLExpr1 operator+(const GrGLSLExpr1& in0, const GrGLSLExpr1& in1) {
+    return GrGLSLExpr1::Add(in0, in1);
+}
+
+inline GrGLSLExpr1 operator-(const GrGLSLExpr1& in0, const GrGLSLExpr1& in1) {
+    return GrGLSLExpr1::Sub(in0, in1);
+}
+
+inline const char* GrGLSLExpr4::ZerosStr() {
+    return "vec4(0)";
+}
+
+inline const char* GrGLSLExpr4::OnesStr() {
+    return "vec4(1)";
+}
+
+inline const char* GrGLSLExpr4::CastStr() {
+    return "vec4(%s)";
+}
+
+inline const char* GrGLSLExpr4::CastIntStr() {
+    return "vec4(%d)";
+}
+
+inline GrGLSLExpr4 GrGLSLExpr4::VectorCast(const GrGLSLExpr1& expr) {
+    return INHERITED::VectorCastImpl(expr);
+}
+
+inline GrGLSLExpr4 GrGLSLExpr4::VectorCast(const GrGLSLExpr4& expr) {
+    return expr;
+}
+
+inline GrGLSLExpr4::AExpr GrGLSLExpr4::a() const {
+    return this->extractComponents<GrGLSLExpr4::AExpr>("%s.a");
+}
+
+inline GrGLSLExpr4 operator*(const GrGLSLExpr1& in0, const GrGLSLExpr4& in1) {
+    return GrGLSLExpr4::Mul(in0, in1);
+}
+
+inline GrGLSLExpr4 operator+(const GrGLSLExpr1& in0, const GrGLSLExpr4& in1) {
+    return GrGLSLExpr4::Add(in0, in1);
+}
+
+inline GrGLSLExpr4 operator-(const GrGLSLExpr1& in0, const GrGLSLExpr4& in1) {
+    return GrGLSLExpr4::Sub(in0, in1);
+}
+
+inline GrGLSLExpr4 operator*(const GrGLSLExpr4& in0, const GrGLSLExpr1& in1) {
+    return GrGLSLExpr4::Mul(in0, in1);
+}
+
+inline GrGLSLExpr4 operator+(const GrGLSLExpr4& in0, const GrGLSLExpr1& in1) {
+    return GrGLSLExpr4::Add(in0, in1);
+}
+
+inline GrGLSLExpr4 operator-(const GrGLSLExpr4& in0, const GrGLSLExpr1& in1) {
+    return GrGLSLExpr4::Sub(in0, in1);
+}
+
+inline GrGLSLExpr4 operator*(const GrGLSLExpr4& in0, const GrGLSLExpr4& in1) {
+    return GrGLSLExpr4::Mul(in0, in1);
+}
+
+inline GrGLSLExpr4 operator+(const GrGLSLExpr4& in0, const GrGLSLExpr4& in1) {
+    return GrGLSLExpr4::Add(in0, in1);
+}
+
+inline GrGLSLExpr4 operator-(const GrGLSLExpr4& in0, const GrGLSLExpr4& in1) {
+    return GrGLSLExpr4::Sub(in0, in1);
+}
+
+#endif

src/core/SkLightingShader.cpp

@@ -168,7 +168,7 @@ public:
             fragBuilder->codeAppendf("vec4 diffuseColor = %s;", args.fInputColor);
 
             SkString dstNormalName("dstNormal");
-            this->emitChild(0, &dstNormalName, args);
+            this->emitChild(0, nullptr, &dstNormalName, args);
 
             fragBuilder->codeAppendf("vec3 normal = %s.xyz;", dstNormalName.c_str());
 

src/core/SkNormalMapSource.cpp

@@ -47,7 +47,7 @@ public:
                                                    kDefault_GrSLPrecision, "Xform", &xformUniName);
 
             SkString dstNormalColorName("dstNormalColor");
-            this->emitChild(0, &dstNormalColorName, args);
+            this->emitChild(0, nullptr, &dstNormalColorName, args);
             fragBuilder->codeAppendf("vec3 normal = normalize(%s.rgb - vec3(0.5));",
                                      dstNormalColorName.c_str());
 

src/effects/GrAlphaThresholdFragmentProcessor.cpp

@@ -127,7 +127,8 @@ void GrGLAlphaThresholdFragmentProcessor::emitCode(EmitArgs& args) {
                             "color.a = inner_thresh;"
                             "}");
 
-    fragBuilder->codeAppendf("%s = %s * color;", args.fOutputColor, args.fInputColor);
+    fragBuilder->codeAppendf("%s = %s;", args.fOutputColor,
+                             (GrGLSLExpr4(args.fInputColor) * GrGLSLExpr4("color")).c_str());
 }
 
 void GrGLAlphaThresholdFragmentProcessor::onSetData(const GrGLSLProgramDataManager& pdman,

src/effects/SkArithmeticImageFilter.cpp

@@ -238,7 +238,7 @@ private:
 
                 GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
                 SkString dstColor("dstColor");
-                this->emitChild(0, &dstColor, args);
+                this->emitChild(0, nullptr, &dstColor, args);
 
                 fKUni = args.fUniformHandler->addUniform(kFragment_GrShaderFlag, kVec4f_GrSLType,
                                                          kDefault_GrSLPrecision, "k");

src/effects/SkLightingImageFilter.cpp

@@ -1915,7 +1915,9 @@ void GrGLLightingEffect::emitCode(EmitArgs& args) {
                              args.fOutputColor, lightFunc.c_str(), normalName.c_str(), surfScale);
     fLight->emitLightColor(uniformHandler, fragBuilder, "surfaceToLight");
     fragBuilder->codeAppend(");\n");
-    fragBuilder->codeAppendf("%s *= %s;\n", args.fOutputColor, args.fInputColor);
+    SkString modulate;
+    GrGLSLMulVarBy4f(&modulate, args.fOutputColor, args.fInputColor);
+    fragBuilder->codeAppend(modulate.c_str());
 }
 
 void GrGLLightingEffect::GenKey(const GrProcessor& proc,

src/effects/SkMagnifierImageFilter.cpp

@@ -196,8 +196,10 @@ void GrGLMagnifierEffect::emitCode(EmitArgs& args) {
                                      &fColorSpaceHelper);
     fragBuilder->codeAppend(";\n");
 
-    fragBuilder->codeAppendf("\t\t%s = output_color;\n", args.fOutputColor);
-    fragBuilder->codeAppendf("%s *= %s;\n", args.fOutputColor, args.fInputColor);
+    fragBuilder->codeAppendf("\t\t%s = output_color;", args.fOutputColor);
+    SkString modulate;
+    GrGLSLMulVarBy4f(&modulate, args.fOutputColor, args.fInputColor);
+    fragBuilder->codeAppend(modulate.c_str());
 }
 
 void GrGLMagnifierEffect::onSetData(const GrGLSLProgramDataManager& pdman,

src/effects/SkMorphologyImageFilter.cpp

@@ -276,7 +276,9 @@ void GrGLMorphologyEffect::emitCode(EmitArgs& args) {
         fragBuilder->codeAppendf("\t\t\tcoord.%s = min(highBound, coord.%s);", dir, dir);
     }
     fragBuilder->codeAppend("\t\t}\n");
-    fragBuilder->codeAppendf("%s *= %s;\n", args.fOutputColor, args.fInputColor);
+    SkString modulate;
+    GrGLSLMulVarBy4f(&modulate, args.fOutputColor, args.fInputColor);
+    fragBuilder->codeAppend(modulate.c_str());
 }
 
 void GrGLMorphologyEffect::GenKey(const GrProcessor& proc,

src/effects/gradients/SkGradientShader.cpp

@@ -1434,7 +1434,8 @@ void GrGradientEffect::GLSLProcessor::emitColor(GrGLSLFPFragmentBuilder* fragBui
             if (ge.fColorSpaceXform) {
                 fragBuilder->codeAppend("colorTemp.rgb = clamp(colorTemp.rgb, 0, colorTemp.a);");
             }
-            fragBuilder->codeAppendf("%s = %s * colorTemp;", outputColor, inputColor);
+            fragBuilder->codeAppendf("%s = %s;", outputColor,
+                                     (GrGLSLExpr4(inputColor) * GrGLSLExpr4("colorTemp")).c_str());
 
             break;
         }
@@ -1472,7 +1473,8 @@ void GrGradientEffect::GLSLProcessor::emitColor(GrGLSLFPFragmentBuilder* fragBui
             if (ge.fColorSpaceXform) {
                 fragBuilder->codeAppend("colorTemp.rgb = clamp(colorTemp.rgb, 0, colorTemp.a);");
             }
-            fragBuilder->codeAppendf("%s = %s * colorTemp;", outputColor, inputColor);
+            fragBuilder->codeAppendf("%s = %s;", outputColor,
+                                     (GrGLSLExpr4(inputColor) * GrGLSLExpr4("colorTemp")).c_str());
 
             break;
         }
@@ -1510,7 +1512,8 @@ void GrGradientEffect::GLSLProcessor::emitColor(GrGLSLFPFragmentBuilder* fragBui
             if (ge.fColorSpaceXform) {
                 fragBuilder->codeAppend("colorTemp.rgb = clamp(colorTemp.rgb, 0, colorTemp.a);");
             }
-            fragBuilder->codeAppendf("%s = %s * colorTemp;", outputColor, inputColor);
+            fragBuilder->codeAppendf("%s = %s;", outputColor,
+                                     (GrGLSLExpr4(inputColor) * GrGLSLExpr4("colorTemp")).c_str());
 
             break;
         }
@@ -1536,7 +1539,8 @@ void GrGradientEffect::GLSLProcessor::emitColor(GrGLSLFPFragmentBuilder* fragBui
                 fragBuilder->codeAppend("colorTemp.rgb = clamp(colorTemp.rgb, 0, colorTemp.a);");
             }
 
-            fragBuilder->codeAppendf("%s = %s * colorTemp;", outputColor, inputColor);
+            fragBuilder->codeAppendf("%s = %s;", outputColor,
+                                     (GrGLSLExpr4(inputColor) * GrGLSLExpr4("colorTemp")).c_str());
 
             break;
         }
@@ -1567,7 +1571,8 @@ void GrGradientEffect::GLSLProcessor::emitColor(GrGLSLFPFragmentBuilder* fragBui
                 fragBuilder->codeAppend("colorTemp.rgb = clamp(colorTemp.rgb, 0, colorTemp.a);");
             }
 
-            fragBuilder->codeAppendf("%s = %s * colorTemp;", outputColor, inputColor);
+            fragBuilder->codeAppendf("%s = %s;", outputColor,
+                                     (GrGLSLExpr4(inputColor) * GrGLSLExpr4("colorTemp")).c_str());
 
             break;
         }

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, args);
+                    this->emitChild(0, nullptr, args);
                     fragBuilder->codeAppendf("%s.rgb *= %s.rgb;", args.fOutputColor,
                                                                 args.fInputColor);
                     fragBuilder->codeAppendf("%s *= %s.a;", args.fOutputColor, args.fInputColor);

src/gpu/effects/GrBicubicEffect.cpp

@@ -112,8 +112,9 @@ void GrGLBicubicEffect::emitCode(EmitArgs& args) {
         fragBuilder->appendColorGamutXform(&xformedColor, bicubicColor.c_str(), &fColorSpaceHelper);
         bicubicColor.swap(xformedColor);
     }
-    fragBuilder->codeAppendf("%s = %s * %s;", args.fOutputColor, bicubicColor.c_str(),
-                             args.fInputColor);
+    fragBuilder->codeAppendf("%s = %s;",
+                             args.fOutputColor, (GrGLSLExpr4(bicubicColor.c_str()) *
+                                                 GrGLSLExpr4(args.fInputColor)).c_str());
 }
 
 void GrGLBicubicEffect::onSetData(const GrGLSLProgramDataManager& pdman,

src/gpu/effects/GrConvexPolyEffect.cpp

@@ -132,7 +132,8 @@ void GLAARectEffect::emitCode(EmitArgs& args) {
     if (GrProcessorEdgeTypeIsInverseFill(aare.getEdgeType())) {
         fragBuilder->codeAppend("\t\talpha = 1.0 - alpha;\n");
     }
-    fragBuilder->codeAppendf("\t\t%s = %s * alpha;\n", args.fOutputColor, args.fInputColor);
+    fragBuilder->codeAppendf("\t\t%s = %s;\n", args.fOutputColor,
+                             (GrGLSLExpr4(args.fInputColor) * GrGLSLExpr1("alpha")).c_str());
 }
 
 void GLAARectEffect::onSetData(const GrGLSLProgramDataManager& pdman,
@@ -211,7 +212,8 @@ void GrGLConvexPolyEffect::emitCode(EmitArgs& args) {
     if (GrProcessorEdgeTypeIsInverseFill(cpe.getEdgeType())) {
         fragBuilder->codeAppend("\talpha = 1.0 - alpha;\n");
     }
-    fragBuilder->codeAppendf("\t%s = %s * alpha;\n", args.fOutputColor, args.fInputColor);
+    fragBuilder->codeAppendf("\t%s = %s;\n", args.fOutputColor,
+                             (GrGLSLExpr4(args.fInputColor) * GrGLSLExpr1("alpha")).c_str());
 }
 
 void GrGLConvexPolyEffect::onSetData(const GrGLSLProgramDataManager& pdman,

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, args.fInputColor);
+                             args.fOutputColor, GrGLSLExpr4(args.fInputColor).c_str());
 }
 
 //////////////////////////////////////////////////////////////////////////////

src/gpu/effects/GrGaussianConvolutionFragmentProcessor.cpp

@@ -91,7 +91,10 @@ void GrGLConvolutionEffect::emitCode(EmitArgs& args) {
         }
         fragBuilder->codeAppendf("coord += %s;\n", imgInc);
     }
-    fragBuilder->codeAppendf("%s *= %s;\n", args.fOutputColor, args.fInputColor);
+
+    SkString modulate;
+    GrGLSLMulVarBy4f(&modulate, args.fOutputColor, args.fInputColor);
+    fragBuilder->codeAppend(modulate.c_str());
 }
 
 void GrGLConvolutionEffect::onSetData(const GrGLSLProgramDataManager& pdman,

src/gpu/effects/GrMatrixConvolutionEffect.cpp

@@ -114,7 +114,10 @@ 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);
     }
-    fragBuilder->codeAppendf("%s *= %s;\n", args.fOutputColor, args.fInputColor);
+
+    SkString modulate;
+    GrGLSLMulVarBy4f(&modulate, args.fOutputColor, args.fInputColor);
+    fragBuilder->codeAppend(modulate.c_str());
 }
 
 void GrGLMatrixConvolutionEffect::GenKey(const GrProcessor& processor,

src/gpu/effects/GrOvalEffect.cpp

@@ -140,7 +140,8 @@ void GLCircleEffect::emitCode(EmitArgs& args) {
         fragBuilder->codeAppend("d = d > 0.5 ? 1.0 : 0.0;");
     }
 
-    fragBuilder->codeAppendf("%s = %s * d;", args.fOutputColor, args.fInputColor);
+    fragBuilder->codeAppendf("%s = %s;", args.fOutputColor,
+                             (GrGLSLExpr4(args.fInputColor) * GrGLSLExpr1("d")).c_str());
 }
 
 void GLCircleEffect::GenKey(const GrProcessor& processor, const GrShaderCaps&,
@@ -332,7 +333,8 @@ void GLEllipseEffect::emitCode(EmitArgs& args) {
             SkFAIL("Hairline not expected here.");
     }
 
-    fragBuilder->codeAppendf("%s = %s * alpha;", args.fOutputColor, args.fInputColor);
+    fragBuilder->codeAppendf("%s = %s;", args.fOutputColor,
+                             (GrGLSLExpr4(args.fInputColor) * GrGLSLExpr1("alpha")).c_str());
 }
 
 void GLEllipseEffect::GenKey(const GrProcessor& effect, const GrShaderCaps&,

src/gpu/effects/GrRRectEffect.cpp

@@ -279,7 +279,8 @@ void GLCircularRRectEffect::emitCode(EmitArgs& args) {
         fragBuilder->codeAppend("alpha = 1.0 - alpha;");
     }
 
-    fragBuilder->codeAppendf("%s = %s * alpha;", args.fOutputColor, args.fInputColor);
+    fragBuilder->codeAppendf("%s = %s;", args.fOutputColor,
+                             (GrGLSLExpr4(args.fInputColor) * GrGLSLExpr1("alpha")).c_str());
 }
 
 void GLCircularRRectEffect::GenKey(const GrProcessor& processor, const GrShaderCaps&,
@@ -589,7 +590,8 @@ void GLEllipticalRRectEffect::emitCode(EmitArgs& args) {
         fragBuilder->codeAppend("float alpha = clamp(0.5 + approx_dist, 0.0, 1.0);");
     }
 
-    fragBuilder->codeAppendf("%s = %s * alpha;", args.fOutputColor, args.fInputColor);
+    fragBuilder->codeAppendf("%s = %s;", args.fOutputColor,
+                             (GrGLSLExpr4(args.fInputColor) * GrGLSLExpr1("alpha")).c_str());
 }
 
 void GLEllipticalRRectEffect::GenKey(const GrProcessor& effect, const GrShaderCaps&,

src/gpu/effects/GrXfermodeFragmentProcessor.cpp

@@ -415,7 +415,7 @@ public:
         ComposeOneFragmentProcessor::Child child =
             args.fFp.cast<ComposeOneFragmentProcessor>().child();
         SkString childColor("child");
-        this->emitChild(0, &childColor, args);
+        this->emitChild(0, nullptr, &childColor, args);
 
         const char* inputColor = args.fInputColor;
         // We don't try to optimize for this case at all

src/gpu/gl/builders/GrGLProgramBuilder.cpp

@@ -42,7 +42,12 @@ GrGLProgram* GrGLProgramBuilder::CreateProgram(const GrPipeline& pipeline,
     // uniforms, varyings, textures, etc
     GrGLProgramBuilder builder(gpu, pipeline, primProc, desc);
 
-    if (!builder.emitAndInstallProcs()) {
+    // 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)) {
         builder.cleanupFragmentProcessors();
         return nullptr;
     }

src/gpu/glsl/GrGLSL.cpp

@@ -45,3 +45,15 @@ 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());
+    }
+}

src/gpu/glsl/GrGLSLFragmentProcessor.cpp

@@ -26,6 +26,7 @@ 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());
@@ -35,7 +36,6 @@ 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

src/gpu/glsl/GrGLSLFragmentProcessor.h

@@ -156,10 +156,6 @@ 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
@@ -171,10 +167,6 @@ 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);
 

src/gpu/glsl/GrGLSLProgramBuilder.cpp

@@ -53,24 +53,24 @@ void GrGLSLProgramBuilder::addFeature(GrShaderFlags shaders,
     }
 }
 
-bool GrGLSLProgramBuilder::emitAndInstallProcs() {
+bool GrGLSLProgramBuilder::emitAndInstallProcs(GrGLSLExpr4* inputColor,
+                                               GrGLSLExpr4* inputCoverage) {
     // 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();
 
-    SkString inputColor;
-    SkString inputCoverage;
-    this->emitAndInstallPrimProc(primProc, &inputColor, &inputCoverage);
-    this->emitAndInstallFragProcs(&inputColor, &inputCoverage);
-    this->emitAndInstallXferProc(inputColor, 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,
-                                                  SkString* outputColor,
-                                                  SkString* outputCoverage) {
+                                                  GrGLSLExpr4* outputColor,
+                                                  GrGLSLExpr4* 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(SkString* color, SkString* coverage) {
+void GrGLSLProgramBuilder::emitAndInstallFragProcs(GrGLSLExpr4* color, GrGLSLExpr4* coverage) {
     int transformedCoordVarsIdx = 0;
-    SkString** inOut = &color;
+    GrGLSLExpr4** inOut = &color;
     for (int i = 0; i < this->pipeline().numFragmentProcessors(); ++i) {
         if (i == this->pipeline().numColorFragmentProcessors()) {
             inOut = &coverage;
         }
-        SkString output;
+        GrGLSLExpr4 output;
         const GrFragmentProcessor& fp = this->pipeline().getFragmentProcessor(i);
-        output = this->emitAndInstallFragProc(fp, i, transformedCoordVarsIdx, **inOut, output);
+        this->emitAndInstallFragProc(fp, i, transformedCoordVarsIdx, **inOut, &output);
         GrFragmentProcessor::Iter iter(&fp);
         while (const GrFragmentProcessor* fp = iter.next()) {
             transformedCoordVarsIdx += fp->numCoordTransforms();
@@ -158,16 +158,15 @@ void GrGLSLProgramBuilder::emitAndInstallFragProcs(SkString* color, SkString* co
 }
 
 // TODO Processors cannot output zeros because an empty string is all 1s
-// 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());
+// 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) {
     // 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;
@@ -194,8 +193,8 @@ SkString GrGLSLProgramBuilder::emitAndInstallFragProc(const GrFragmentProcessor&
                                            this->uniformHandler(),
                                            this->shaderCaps(),
                                            fp,
-                                           output.c_str(),
-                                           input.c_str(),
+                                           output->c_str(),
+                                           input.isOnes() ? nullptr : input.c_str(),
                                            coords,
                                            textureSamplers,
                                            bufferSamplers,
@@ -210,11 +209,10 @@ SkString GrGLSLProgramBuilder::emitAndInstallFragProc(const GrFragmentProcessor&
     fFragmentProcessors.push_back(fragProc);
 
     fFS.codeAppend("}");
-    return output;
 }
 
-void GrGLSLProgramBuilder::emitAndInstallXferProc(const SkString& colorIn,
-                                                  const SkString& coverageIn) {
+void GrGLSLProgramBuilder::emitAndInstallXferProc(const GrGLSLExpr4& colorIn,
+                                                  const GrGLSLExpr4& coverageIn) {
     // Program builders have a bit of state we need to clear with each effect
     AutoStageAdvance adv(this);
 
@@ -251,8 +249,8 @@ void GrGLSLProgramBuilder::emitAndInstallXferProc(const SkString& colorIn,
                                        this->uniformHandler(),
                                        this->shaderCaps(),
                                        xp,
-                                       colorIn.size() ? colorIn.c_str() : "vec4(1)",
-                                       coverageIn.size() ? coverageIn.c_str() : "vec4(1)",
+                                       colorIn.c_str(),
+                                       coverageIn.c_str(),
                                        fFS.getPrimaryColorOutputName(),
                                        fFS.getSecondaryColorOutputName(),
                                        dstTextureSamplerHandle,
@@ -447,12 +445,12 @@ void GrGLSLProgramBuilder::nameVariable(SkString* out, char prefix, const char*
     }
 }
 
-void GrGLSLProgramBuilder::nameExpression(SkString* output, const char* baseName) {
+void GrGLSLProgramBuilder::nameExpression(GrGLSLExpr4* 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->size()) {
+    if (output->isValid()) {
         outName = output->c_str();
     } else {
         this->nameVariable(&outName, '\0', baseName);

src/gpu/glsl/GrGLSLProgramBuilder.h

@@ -22,7 +22,7 @@
 
 class GrShaderVar;
 class GrGLSLVaryingHandler;
-class SkString;
+class GrGLSLExpr4;
 class GrShaderCaps;
 
 typedef SkSTArray<8, GrGLSLFragmentProcessor*, true> GrGLSLFragProcs;
@@ -110,7 +110,7 @@ protected:
 
     void addFeature(GrShaderFlags shaders, uint32_t featureBit, const char* extensionName);
 
-    bool emitAndInstallProcs();
+    bool emitAndInstallProcs(GrGLSLExpr4* inputColor, GrGLSLExpr4* inputCoverage);
 
     void cleanupFragmentProcessors();
 
@@ -140,18 +140,19 @@ private:
     };
 
     // Generates a possibly mangled name for a stage variable and writes it to the fragment shader.
-    void nameExpression(SkString*, const char* baseName);
+    // If GrGLSLExpr4 has a valid name then it will use that instead
+    void nameExpression(GrGLSLExpr4*, const char* baseName);
 
     void emitAndInstallPrimProc(const GrPrimitiveProcessor&,
-                                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);
+                                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);
     void emitSamplersAndImageStorages(const GrResourceIOProcessor& processor,
                                       SkTArray<SamplerHandle>* outTexSamplerHandles,
                                       SkTArray<SamplerHandle>* outBufferSamplerHandles,

src/gpu/glsl/GrGLSLShaderBuilder.cpp

@@ -101,17 +101,9 @@ void GrGLSLShaderBuilder::appendTextureLookupAndModulate(
     if (colorXformHelper && colorXformHelper->isValid()) {
         SkString xform;
         this->appendColorGamutXform(&xform, lookup.c_str(), colorXformHelper);
-        if (modulation) {
-            this->codeAppendf("%s * %s", modulation, xform.c_str());
-        } else {
-            this->codeAppendf("%s", xform.c_str());
-        }
+        this->codeAppend((GrGLSLExpr4(modulation) * GrGLSLExpr4(xform)).c_str());
     } else {
-        if (modulation) {
-            this->codeAppendf("%s * %s", modulation, lookup.c_str());
-        } else {
-            this->codeAppendf("%s", lookup.c_str());
-        }
+        this->codeAppend((GrGLSLExpr4(modulation) * GrGLSLExpr4(lookup)).c_str());
     }
 }
 

src/gpu/vk/GrVkPipelineStateBuilder.cpp

@@ -25,7 +25,10 @@ GrVkPipelineState* GrVkPipelineStateBuilder::CreatePipelineState(
     // uniforms, varyings, textures, etc
     GrVkPipelineStateBuilder builder(gpu, pipeline, primProc, desc);
 
-    if (!builder.emitAndInstallProcs()) {
+    GrGLSLExpr4 inputColor;
+    GrGLSLExpr4 inputCoverage;
+
+    if (!builder.emitAndInstallProcs(&inputColor, &inputCoverage)) {
         builder.cleanupFragmentProcessors();
         return nullptr;
     }

tests/GLProgramsTest.cpp

@@ -113,7 +113,7 @@ private:
     class GLFP : public GrGLSLFragmentProcessor {
     public:
         void emitCode(EmitArgs& args) override {
-            this->emitChild(0, args);
+            this->emitChild(0, nullptr, args);
         }
 
     private: