fixed sksl static ifs to work for CircleEffect

static ifs (and switches) in .fp files are a bit tricky, because they
aren't necessarily static when the CPP file is being produced. They
become static when the CPP file produces the final SkSL; at this point
the final values of the 'in' variables are known.

This change permits 'deferred' static ifs and switches. The initial
compilation (.fp -> .cpp) passes the @if / @switch through, and then
the final compilation (.cpp's generated SkSL -> GLSL or whatever)
enforces the static test.

Bug: skia:
Change-Id: I0087dfe1725c8fd350507ac77f64db1d82659cdf
Reviewed-on: https://skia-review.googlesource.com/23403
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>

8 files changed, 47 insertions, 17 deletions

diff --git a/src/gpu/effects/GrCircleEffect.cpp b/src/gpu/effects/GrCircleEffect.cpp
index acd2a9b977..23d6551770 100644
--- a/src/gpu/effects/GrCircleEffect.cpp
+++ b/src/gpu/effects/GrCircleEffect.cpp
@@ -25,7 +25,7 @@ public:
         (void) _outer;
 prevRadius = -1.0;
         fCircleVar = args.fUniformHandler->addUniform(kFragment_GrShaderFlag, kVec4f_GrSLType, kDefault_GrSLPrecision, "circle");
-        fragBuilder->codeAppendf("vec2 prevCenter;\nfloat prevRadius = %f;\nfloat d;\nif (%d == 2 || %d == 3) {\n    d = (length((%s.xy - sk_FragCoord.xy) * %s.w) - 1.0) * %s.z;\n} else {\n    d = (1.0 - length((%s.xy - sk_FragCoord.xy) * %s.w)) * %s.z;\n}\nif ((%d == 1 || %d == 3) || %d == 4) {\n    d = clamp(d, 0.0, 1.0);\n} else {\n    d = d > 0.5 ? 1.0 : 0.0;\n}\n%s = %s * d;\n", prevRadius, _outer.edgeType(), _outer.edgeType(), args.fUniformHandler->getUniformCStr(fCircleVar), args.fUniformHandler->getUniformCStr(fCircleVar), args.fUniformHandler->getUniformCStr(fCircleVar), args.fUniformHandler->getUniformCStr(fCircleVar), args.fUniformHandler->getUniformCStr(fCircleVar), args.fUniformHandler->getUniformCStr(fCircleVar), _outer.edgeType(), _outer.edgeType(), _outer.edgeType(), args.fOutputColor, args.fInputColor ? args.fInputColor : "vec4(1)");
+        fragBuilder->codeAppendf("vec2 prevCenter;\nfloat prevRadius = %f;\nfloat d;\n@if (%d == 2 || %d == 3) {\n    d = (length((%s.xy - sk_FragCoord.xy) * %s.w) - 1.0) * %s.z;\n} else {\n    d = (1.0 - length((%s.xy - sk_FragCoord.xy) * %s.w)) * %s.z;\n}\n@if ((%d == 1 || %d == 3) || %d == 4) {\n    d = clamp(d, 0.0, 1.0);\n} else {\n    d = d > 0.5 ? 1.0 : 0.0;\n}\n%s = %s * d;\n", prevRadius, _outer.edgeType(), _outer.edgeType(), args.fUniformHandler->getUniformCStr(fCircleVar), args.fUniformHandler->getUniformCStr(fCircleVar), args.fUniformHandler->getUniformCStr(fCircleVar), args.fUniformHandler->getUniformCStr(fCircleVar), args.fUniformHandler->getUniformCStr(fCircleVar), args.fUniformHandler->getUniformCStr(fCircleVar), _outer.edgeType(), _outer.edgeType(), _outer.edgeType(), args.fOutputColor, args.fInputColor ? args.fInputColor : "vec4(1)");
     }
 private:
     void onSetData(const GrGLSLProgramDataManager& pdman, const GrFragmentProcessor& _proc) override {
diff --git a/src/gpu/effects/GrCircleEffect.fp b/src/gpu/effects/GrCircleEffect.fp
index 3f0b85017e..74973ca064 100644
--- a/src/gpu/effects/GrCircleEffect.fp
+++ b/src/gpu/effects/GrCircleEffect.fp
@@ -37,15 +37,15 @@ void main() {
     // radius and then denormalized. This is to prevent overflow on devices that have a "real"
     // mediump. It'd be nice to only do this on mediump devices.
     float d;
-    if (edgeType == 2 /* kInverseFillBW_GrProcessorEdgeType */ ||
-        edgeType == 3 /* kInverseFillAA_GrProcessorEdgeType */) {
+    @if (edgeType == 2 /* kInverseFillBW_GrProcessorEdgeType */ ||
+         edgeType == 3 /* kInverseFillAA_GrProcessorEdgeType */) {
         d = (length((circle.xy - sk_FragCoord.xy) * circle.w) - 1.0) * circle.z;
     } else {
         d = (1.0 - length((circle.xy - sk_FragCoord.xy) *  circle.w)) * circle.z;
     }
-    if (edgeType == 1 /* kFillAA_GrProcessorEdgeType */ ||
-        edgeType == 3 /* kInverseFillAA_GrProcessorEdgeType */ ||
-        edgeType == 4 /* kHairlineAA_GrProcessorEdgeType */) {
+    @if (edgeType == 1 /* kFillAA_GrProcessorEdgeType */ ||
+         edgeType == 3 /* kInverseFillAA_GrProcessorEdgeType */ ||
+         edgeType == 4 /* kHairlineAA_GrProcessorEdgeType */) {
         d = clamp(d, 0.0, 1.0);
     } else {
         d = d > 0.5 ? 1.0 : 0.0;
diff --git a/src/sksl/SkSLCPPCodeGenerator.cpp b/src/sksl/SkSLCPPCodeGenerator.cpp
index 238615db49..3da7e8e5f0 100644
--- a/src/sksl/SkSLCPPCodeGenerator.cpp
+++ b/src/sksl/SkSLCPPCodeGenerator.cpp
@@ -225,6 +225,20 @@ void CPPCodeGenerator::writeVariableReference(const VariableReference& ref) {
     }
 }
 
+void CPPCodeGenerator::writeIfStatement(const IfStatement& s) {
+    if (s.fIsStatic) {
+        this->write("@");
+    }
+    INHERITED::writeIfStatement(s);
+}
+
+void CPPCodeGenerator::writeSwitchStatement(const SwitchStatement& s) {
+    if (s.fIsStatic) {
+        this->write("@");
+    }
+    INHERITED::writeSwitchStatement(s);
+}
+
 void CPPCodeGenerator::writeFunctionCall(const FunctionCall& c) {
     if (c.fFunction.fBuiltin && c.fFunction.fName == "COLORSPACE") {
         String tmpVar = "_tmpVar" + to_string(++fVarCount);
diff --git a/src/sksl/SkSLCPPCodeGenerator.h b/src/sksl/SkSLCPPCodeGenerator.h
index 0f6da5f5c4..7f60563e51 100644
--- a/src/sksl/SkSLCPPCodeGenerator.h
+++ b/src/sksl/SkSLCPPCodeGenerator.h
@@ -41,6 +41,10 @@ private:
 
     String getSamplerHandle(const Variable& var);
 
+    void writeIfStatement(const IfStatement& s) override;
+
+    void writeSwitchStatement(const SwitchStatement& s) override;
+
     void writeFunctionCall(const FunctionCall& c) override;
 
     void writeFunction(const FunctionDefinition& f) override;
diff --git a/src/sksl/SkSLCompiler.cpp b/src/sksl/SkSLCompiler.cpp
index 593397bd2a..3a037e798e 100644
--- a/src/sksl/SkSLCompiler.cpp
+++ b/src/sksl/SkSLCompiler.cpp
@@ -54,8 +54,9 @@ static const char* SKSL_FP_INCLUDE =
 
 namespace SkSL {
 
-Compiler::Compiler()
-: fErrorCount(0) {
+Compiler::Compiler(Flags flags)
+: fFlags(flags)
+, fErrorCount(0) {
     auto types = std::shared_ptr<SymbolTable>(new SymbolTable(this));
     auto symbols = std::shared_ptr<SymbolTable>(new SymbolTable(types, this));
     fIRGenerator = new IRGenerator(&fContext, symbols, *this);
@@ -931,7 +932,7 @@ void Compiler::simplifyStatement(DefinitionMap& definitions,
                             (*iter)->setStatement(std::move(newBlock));
                             break;
                         } else {
-                            if (s.fIsStatic) {
+                            if (s.fIsStatic && !(fFlags & kPermitInvalidStaticTests_Flag)) {
                                 this->error(s.fPosition,
                                             "static switch contains non-static conditional break");
                                 s.fIsStatic = false;
@@ -947,7 +948,7 @@ void Compiler::simplifyStatement(DefinitionMap& definitions,
                         if (newBlock) {
                             (*iter)->setStatement(std::move(newBlock));
                         } else {
-                            if (s.fIsStatic) {
+                            if (s.fIsStatic && !(fFlags & kPermitInvalidStaticTests_Flag)) {
                                 this->error(s.fPosition,
                                             "static switch contains non-static conditional break");
                                 s.fIsStatic = false;
@@ -1047,13 +1048,15 @@ void Compiler::scanCFG(FunctionDefinition& f) {
                 const Statement& s = **iter->statement();
                 switch (s.fKind) {
                     case Statement::kIf_Kind:
-                        if (((const IfStatement&) s).fIsStatic) {
+                        if (((const IfStatement&) s).fIsStatic &&
+                            !(fFlags & kPermitInvalidStaticTests_Flag)) {
                             this->error(s.fPosition, "static if has non-static test");
                         }
                         ++iter;
                         break;
                     case Statement::kSwitch_Kind:
-                        if (((const SwitchStatement&) s).fIsStatic) {
+                        if (((const SwitchStatement&) s).fIsStatic &&
+                             !(fFlags & kPermitInvalidStaticTests_Flag)) {
                             this->error(s.fPosition, "static switch has non-static test");
                         }
                         ++iter;
diff --git a/src/sksl/SkSLCompiler.h b/src/sksl/SkSLCompiler.h
index 2acb55958f..38f63e542c 100644
--- a/src/sksl/SkSLCompiler.h
+++ b/src/sksl/SkSLCompiler.h
@@ -43,7 +43,15 @@ class IRGenerator;
  */
 class Compiler : public ErrorReporter {
 public:
-    Compiler();
+    enum Flags {
+        kNone_Flags = 0,
+        // permits static if/switch statements to be used with non-constant tests. This is used when
+        // producing H and CPP code; the static tests don't have to have constant values *yet*, but
+        // the generated code will contain a static test which then does have to be a constant.
+        kPermitInvalidStaticTests_Flag = 1,
+    };
+
+    Compiler(Flags flags = kNone_Flags);
 
     ~Compiler() override;
 
@@ -109,6 +117,7 @@ private:
     std::shared_ptr<SymbolTable> fTypes;
     IRGenerator* fIRGenerator;
     String fSkiaVertText; // FIXME store parsed version instead
+    int fFlags;
 
     Context fContext;
     int fErrorCount;
diff --git a/src/sksl/SkSLGLSLCodeGenerator.h b/src/sksl/SkSLGLSLCodeGenerator.h
index 5716bde70d..6fe25d3a69 100644
--- a/src/sksl/SkSLGLSLCodeGenerator.h
+++ b/src/sksl/SkSLGLSLCodeGenerator.h
@@ -162,7 +162,7 @@ protected:
 
     void writeBlock(const Block& b);
 
-    void writeIfStatement(const IfStatement& stmt);
+    virtual void writeIfStatement(const IfStatement& stmt);
 
     void writeForStatement(const ForStatement& f);
 
@@ -170,7 +170,7 @@ protected:
 
     void writeDoStatement(const DoStatement& d);
 
-    void writeSwitchStatement(const SwitchStatement& s);
+    virtual void writeSwitchStatement(const SwitchStatement& s);
 
     void writeReturnStatement(const ReturnStatement& r);
 
diff --git a/src/sksl/SkSLMain.cpp b/src/sksl/SkSLMain.cpp
index 3e3d747304..9f1fec1f1b 100644
--- a/src/sksl/SkSLMain.cpp
+++ b/src/sksl/SkSLMain.cpp
@@ -95,7 +95,7 @@ int main(int argc, const char** argv) {
         }
     } else if (name.endsWith(".h")) {
         SkSL::FileOutputStream out(argv[2]);
-        SkSL::Compiler compiler;
+        SkSL::Compiler compiler(SkSL::Compiler::kPermitInvalidStaticTests_Flag);
         if (!out.isValid()) {
             printf("error writing '%s'\n", argv[2]);
             exit(4);
@@ -112,7 +112,7 @@ int main(int argc, const char** argv) {
         }
     } else if (name.endsWith(".cpp")) {
         SkSL::FileOutputStream out(argv[2]);
-        SkSL::Compiler compiler;
+        SkSL::Compiler compiler(SkSL::Compiler::kPermitInvalidStaticTests_Flag);
         if (!out.isValid()) {
             printf("error writing '%s'\n", argv[2]);
             exit(4);