Turned on SkSL->GLSL compiler

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2288033003

Review-Url: https://codereview.chromium.org/2288033003

9 files changed, 242 insertions, 33 deletions

diff --git a/src/sksl/README b/src/sksl/README
new file mode 100644
index 0000000000..da426923e3
--- /dev/null
+++ b/src/sksl/README
@@ -0,0 +1,34 @@
+Overview
+========
+
+SkSL ("Skia Shading Language") is a variant of GLSL which is used as Skia's 
+internal shading language. SkSL is, at its heart, a single standardized version
+of GLSL which avoids all of the various version and dialect differences found
+in GLSL "in the wild", but it does bring a few of its own changes to the table.
+
+Skia uses the SkSL compiler to convert SkSL code to GLSL, GLSL ES, or SPIR-V
+before handing it over to the graphics driver.
+
+Differences from GLSL
+=====================
+
+SkSL is based on GLSL 4.5. For the most part, write SkSL exactly as you would
+desktop GLSL, and the SkSL compiler will take care of version and dialect
+differences (for instance, you always use "in" and "out", and skslc will handle
+translating them to "varying" and "attribute" as appropriate). Be aware of the 
+following differences between SkSL and GLSL:
+
+* no #version or "precision" statement is required, and they will be ignored if
+  present
+* the output color is sk_FragColor (do not declare it)
+* lowp, mediump, and highp are always permitted (but will only be respected if 
+  you run on a GLES device)
+* you do not need to include ".0" to make a number a float (meaning that
+  "vec2(x, y) * 4" is perfectly legal in SkSL, unlike GLSL where it would have
+  to be expressed "vec2(x, y) * 4.0". There is no performance penalty for this, 
+  as the number is converted to a float at compile time)
+* some built-in functions and one or two rarely-used language features are not
+  yet supported (sorry!)
+
+SkSL is still under development, and is expected to diverge further from GLSL
+over time.
diff --git a/src/sksl/SkSLCompiler.h b/src/sksl/SkSLCompiler.h
index 9cd1eac3f9..3f76aec3a0 100644
--- a/src/sksl/SkSLCompiler.h
+++ b/src/sksl/SkSLCompiler.h
@@ -24,6 +24,8 @@ class IRGenerator;
  * file into an abstract syntax tree (a tree of ASTNodes), then performs semantic analysis to 
  * produce a Program (a tree of IRNodes), then feeds the Program into a CodeGenerator to produce
  * compiled output.
+ *
+ * See the README for information about SkSL.
  */
 class Compiler : public ErrorReporter {
 public:
diff --git a/src/sksl/SkSLGLSLCodeGenerator.cpp b/src/sksl/SkSLGLSLCodeGenerator.cpp
index da0bcb903c..f989decdee 100644
--- a/src/sksl/SkSLGLSLCodeGenerator.cpp
+++ b/src/sksl/SkSLGLSLCodeGenerator.cpp
@@ -16,6 +16,8 @@
 #include "ir/SkSLIndexExpression.h"
 #include "ir/SkSLVariableReference.h"
 
+#define SK_FRAGCOLOR_BUILTIN 10001
+
 namespace SkSL {
 
 void GLSLCodeGenerator::write(const char* s) {
@@ -66,7 +68,7 @@ void GLSLCodeGenerator::writeType(const Type& type) {
         this->writeLine("struct " + type.name() + " {");
         fIndentation++;
         for (const auto& f : type.fields()) {
-            this->writeModifiers(f.fModifiers);
+            this->writeModifiers(f.fModifiers, false);
             // sizes (which must be static in structs) are part of the type name here
             this->writeType(*f.fType);
             this->writeLine(" " + f.fName + ";");
@@ -124,7 +126,40 @@ void GLSLCodeGenerator::writeExpression(const Expression& expr, Precedence paren
     }
 }
 
+static bool is_abs(Expression& expr) {
+    if (expr.fKind != Expression::kFunctionCall_Kind) {
+        return false;
+    }
+    return ((FunctionCall&) expr).fFunction.fName == "abs";
+}
+
+// turns min(abs(x), y) into (abs(x) > (tmpVar = y) ? tmpVar : abs(x)) to avoid a Tegra3 compiler 
+// bug.
+void GLSLCodeGenerator::writeMinAbsHack(Expression& absExpr, Expression& otherExpr) {
+    ASSERT(!fCaps.fCanUseMinAndAbsTogether);
+    std::string varName = "minAbsHackVar" + to_string(fVarCount++);
+    this->fFunctionHeader += "    " + otherExpr.fType.name() + " " + varName + ";\n";
+    this->write("(");
+    this->writeExpression(absExpr, kTopLevel_Precedence);
+    this->write(" > (" + varName + " = ");
+    this->writeExpression(otherExpr, kRelational_Precedence);
+    this->write(") ? " + varName + " : ");
+    this->writeExpression(absExpr, kTernary_Precedence);
+    this->write(")");
+}
+
 void GLSLCodeGenerator::writeFunctionCall(const FunctionCall& c) {
+    if (!fCaps.fCanUseMinAndAbsTogether && c.fFunction.fName == "min") {
+        ASSERT(c.fArguments.size() == 2);
+        if (is_abs(*c.fArguments[0])) {
+            this->writeMinAbsHack(*c.fArguments[0], *c.fArguments[1]);
+            return;
+        }
+        if (is_abs(*c.fArguments[1])) {
+            this->writeMinAbsHack(*c.fArguments[1], *c.fArguments[0]);
+            return;
+        }
+    }
     this->write(c.fFunction.fName + "(");
     const char* separator = "";
     for (const auto& arg : c.fArguments) {
@@ -147,7 +182,15 @@ void GLSLCodeGenerator::writeConstructor(const Constructor& c) {
 }
 
 void GLSLCodeGenerator::writeVariableReference(const VariableReference& ref) {
-    this->write(ref.fVariable.fName);
+    if (ref.fVariable.fModifiers.fLayout.fBuiltin == SK_FRAGCOLOR_BUILTIN) {
+        if (fCaps.fMustDeclareFragmentShaderOutput) {
+            this->write("sk_FragColor");
+        } else {
+            this->write("gl_FragColor");
+        }
+    } else {
+        this->write(ref.fVariable.fName);
+    }
 }
 
 void GLSLCodeGenerator::writeIndexExpression(const IndexExpression& expr) {
@@ -284,28 +327,89 @@ void GLSLCodeGenerator::writeFunction(const FunctionDefinition& f) {
     for (const auto& param : f.fDeclaration.fParameters) {
         this->write(separator);
         separator = ", ";
-        this->writeModifiers(param->fModifiers);
+        this->writeModifiers(param->fModifiers, false);
         this->writeType(param->fType);
         this->write(" " + param->fName);
     }
-    this->write(") ");
-    this->writeBlock(*f.fBody);
-    this->writeLine();
+    this->writeLine(") {");
+
+    fFunctionHeader = "";
+    std::ostream* oldOut = fOut;
+    std::stringstream buffer;
+    fOut = &buffer;
+    fIndentation++;
+    for (const auto& s : f.fBody->fStatements) {
+        this->writeStatement(*s);
+        this->writeLine();
+    }
+    fIndentation--;
+    this->writeLine("}");
+
+    fOut = oldOut;
+    this->write(fFunctionHeader);
+    this->write(buffer.str());
 }
 
-void GLSLCodeGenerator::writeModifiers(const Modifiers& modifiers) {
-    this->write(modifiers.description());
+void GLSLCodeGenerator::writeModifiers(const Modifiers& modifiers, 
+                                       bool globalContext) {
+    if (modifiers.fFlags & Modifiers::kNoPerspective_Flag) {
+        this->write("noperspective ");
+    }
+    if (modifiers.fFlags & Modifiers::kFlat_Flag) {
+        this->write("flat ");
+    }
+    std::string layout = modifiers.fLayout.description();
+    if (layout.length()) {
+        this->write(layout + " ");
+    }
+    if ((modifiers.fFlags & Modifiers::kIn_Flag) && 
+        (modifiers.fFlags & Modifiers::kOut_Flag)) {
+        this->write("inout ");
+    } else if (modifiers.fFlags & Modifiers::kIn_Flag) {
+        if (globalContext && fCaps.fVersion < 130) {
+            this->write(fProgramKind == Program::kVertex_Kind ? "attribute "
+                                                              : "varying ");
+        } else {
+            this->write("in ");
+        }
+    } else if (modifiers.fFlags & Modifiers::kOut_Flag) {
+        if (globalContext && fCaps.fVersion < 130) {
+            this->write("varying ");
+        } else {
+            this->write("out ");
+        }
+    }
+    if (modifiers.fFlags & Modifiers::kUniform_Flag) {
+        this->write("uniform ");
+    }
+    if (modifiers.fFlags & Modifiers::kConst_Flag) {
+        this->write("const ");
+    }
+    if (fCaps.fUsesPrecisionModifiers) {
+        bool modifier = false;
+        if (modifiers.fFlags & Modifiers::kLowp_Flag) {
+            this->write("lowp ");
+            modifier = true;
+        }
+        if (modifiers.fFlags & Modifiers::kHighp_Flag) {
+            this->write("highp ");
+            modifier = true;
+        }
+        if (!modifier) {
+            this->write("mediump ");
+        }
+    }
 }
 
 void GLSLCodeGenerator::writeInterfaceBlock(const InterfaceBlock& intf) {
     if (intf.fVariable.fName == "gl_PerVertex") {
         return;
     }
-    this->writeModifiers(intf.fVariable.fModifiers);
+    this->writeModifiers(intf.fVariable.fModifiers, true);
     this->writeLine(intf.fVariable.fType.name() + " {");
     fIndentation++;
     for (const auto& f : intf.fVariable.fType.fields()) {
-        this->writeModifiers(f.fModifiers);
+        this->writeModifiers(f.fModifiers, false);
         this->writeType(*f.fType);
         this->writeLine(" " + f.fName + ";");
     }
@@ -313,9 +417,9 @@ void GLSLCodeGenerator::writeInterfaceBlock(const InterfaceBlock& intf) {
     this->writeLine("};");
 }
 
-void GLSLCodeGenerator::writeVarDeclarations(const VarDeclarations& decl) {
+void GLSLCodeGenerator::writeVarDeclarations(const VarDeclarations& decl, bool global) {
     ASSERT(decl.fVars.size() > 0);
-    this->writeModifiers(decl.fVars[0].fVar->fModifiers);
+    this->writeModifiers(decl.fVars[0].fVar->fModifiers, global);
     this->writeType(decl.fBaseType);
     std::string separator = " ";
     for (const auto& var : decl.fVars) {
@@ -349,7 +453,7 @@ void GLSLCodeGenerator::writeStatement(const Statement& s) {
             this->writeReturnStatement((ReturnStatement&) s);
             break;
         case Statement::kVarDeclarations_Kind:
-            this->writeVarDeclarations(*((VarDeclarationsStatement&) s).fDeclaration);
+            this->writeVarDeclarations(*((VarDeclarationsStatement&) s).fDeclaration, false);
             break;
         case Statement::kIf_Kind:
             this->writeIfStatement((IfStatement&) s);
@@ -444,9 +548,12 @@ void GLSLCodeGenerator::writeReturnStatement(const ReturnStatement& r) {
 void GLSLCodeGenerator::generateCode(const Program& program, std::ostream& out) {
     ASSERT(fOut == nullptr);
     fOut = &out;
+    fProgramKind = program.fKind;
     this->write("#version " + to_string(fCaps.fVersion));
     if (fCaps.fStandard == GLCaps::kGLES_Standard) {
         this->write(" es");
+    } else if (fCaps.fIsCoreProfile) {
+        this->write(" core");
     }
     this->writeLine();
     for (const auto& e : program.fElements) {
@@ -456,10 +563,16 @@ void GLSLCodeGenerator::generateCode(const Program& program, std::ostream& out)
                 break;
             case ProgramElement::kVar_Kind: {
                 VarDeclarations& decl = (VarDeclarations&) *e;
-                if (decl.fVars.size() > 0 && 
-                    decl.fVars[0].fVar->fModifiers.fLayout.fBuiltin == -1) {
-                    this->writeVarDeclarations(decl);
-                    this->writeLine();
+                if (decl.fVars.size() > 0) {
+                    int builtin = decl.fVars[0].fVar->fModifiers.fLayout.fBuiltin;
+                    if (builtin == -1) {
+                        // normal var
+                        this->writeVarDeclarations(decl, true);
+                        this->writeLine();
+                    } else if (builtin == SK_FRAGCOLOR_BUILTIN &&
+                               fCaps.fMustDeclareFragmentShaderOutput) {
+                        this->writeLine("out vec4 sk_FragColor;");
+                    }
                 }
                 break;
             }
diff --git a/src/sksl/SkSLGLSLCodeGenerator.h b/src/sksl/SkSLGLSLCodeGenerator.h
index 3534affccc..63fab05e08 100644
--- a/src/sksl/SkSLGLSLCodeGenerator.h
+++ b/src/sksl/SkSLGLSLCodeGenerator.h
@@ -50,6 +50,11 @@ struct GLCaps {
         kGL_Standard,
         kGLES_Standard
     } fStandard;
+    bool fIsCoreProfile;
+    bool fUsesPrecisionModifiers;
+    bool fMustDeclareFragmentShaderOutput;
+    // The Tegra3 compiler will sometimes never return if we have min(abs(x), y)
+    bool fCanUseMinAndAbsTogether;
 };
 
 /**
@@ -81,6 +86,7 @@ public:
     GLSLCodeGenerator(const Context* context, GLCaps caps)
     : fContext(*context)
     , fCaps(caps)
+    , fVarCount(0)
     , fIndentation(0)
     , fAtLineStart(true) {}
 
@@ -111,11 +117,11 @@ private:
 
     void writeLayout(const Layout& layout);
 
-    void writeModifiers(const Modifiers& modifiers);
+    void writeModifiers(const Modifiers& modifiers, bool globalContext);
     
     void writeGlobalVars(const VarDeclaration& vs);
 
-    void writeVarDeclarations(const VarDeclarations& decl);
+    void writeVarDeclarations(const VarDeclarations& decl, bool global);
 
     void writeVariableReference(const VariableReference& ref);
 
@@ -123,6 +129,8 @@ private:
     
     void writeIntrinsicCall(const FunctionCall& c);
 
+    void writeMinAbsHack(Expression& absExpr, Expression& otherExpr);
+
     void writeFunctionCall(const FunctionCall& c);
 
     void writeConstructor(const Constructor& c);
@@ -164,6 +172,9 @@ private:
     const Context& fContext;
     const GLCaps fCaps;
     std::ostream* fOut;
+    std::string fFunctionHeader;
+    Program::Kind fProgramKind;
+    int fVarCount;
     int fIndentation;
     bool fAtLineStart;
     // Keeps track of which struct types we have written. Given that we are unlikely to ever write 
diff --git a/src/sksl/SkSLIRGenerator.cpp b/src/sksl/SkSLIRGenerator.cpp
index c30cac17d7..5e136a4d2f 100644
--- a/src/sksl/SkSLIRGenerator.cpp
+++ b/src/sksl/SkSLIRGenerator.cpp
@@ -419,8 +419,9 @@ std::unique_ptr<FunctionDefinition> IRGenerator::convertFunction(const ASTFuncti
                     for (size_t i = 0; i < parameters.size(); i++) {
                         if (parameters[i]->fModifiers != other->fParameters[i]->fModifiers) {
                             fErrors.error(f.fPosition, "modifiers on parameter " + 
-                                                       to_string(i + 1) + " differ between " +
-                                                       "declaration and definition");
+                                                       to_string((uint64_t) i + 1) + 
+                                                       " differ between declaration and "
+                                                       "definition");
                             return nullptr;
                         }
                     }
@@ -616,8 +617,9 @@ std::unique_ptr<Expression> IRGenerator::coerce(std::unique_ptr<Expression> expr
         ASSERT(ctor);
         return this->call(Position(), std::move(ctor), std::move(args));
     }
-    ABORT("cannot coerce %s to %s", expr->fType.description().c_str(), 
-          type.description().c_str());
+    std::vector<std::unique_ptr<Expression>> args;
+    args.push_back(std::move(expr));
+    return std::unique_ptr<Expression>(new Constructor(Position(), type, std::move(args)));
 }
 
 static bool is_matrix_multiply(const Type& left, const Type& right) {
@@ -832,12 +834,12 @@ std::unique_ptr<Expression> IRGenerator::call(Position position,
                                               std::vector<std::unique_ptr<Expression>> arguments) {
     if (function.fParameters.size() != arguments.size()) {
         std::string msg = "call to '" + function.fName + "' expected " + 
-                                 to_string(function.fParameters.size()) + 
+                                 to_string((uint64_t) function.fParameters.size()) + 
                                  " argument";
         if (function.fParameters.size() != 1) {
             msg += "s";
         }
-        msg += ", but found " + to_string(arguments.size());
+        msg += ", but found " + to_string((uint64_t) arguments.size());
         fErrors.error(position, msg);
         return nullptr;
     }
@@ -938,7 +940,7 @@ std::unique_ptr<Expression> IRGenerator::convertConstructor(
         if (args.size() != 1) {
             fErrors.error(position, "invalid arguments to '" + type.description() + 
                                     "' constructor, (expected exactly 1 argument, but found " +
-                                    to_string(args.size()) + ")");
+                                    to_string((uint64_t) args.size()) + ")");
         }
         if (args[0]->fType == *fContext.fBool_Type) {
             std::unique_ptr<IntLiteral> zero(new IntLiteral(fContext, position, 0));
diff --git a/src/sksl/SkSLParser.cpp b/src/sksl/SkSLParser.cpp
index b240e4501e..f9e7498ee5 100644
--- a/src/sksl/SkSLParser.cpp
+++ b/src/sksl/SkSLParser.cpp
@@ -185,7 +185,8 @@ void Parser::precision() {
     this->expect(Token::SEMICOLON, "';'");
 }
 
-/* DIRECTIVE(#version) INT_LITERAL | DIRECTIVE(#extension) IDENTIFIER COLON IDENTIFIER */
+/* DIRECTIVE(#version) INT_LITERAL ("es" | "compatibility")? | 
+   DIRECTIVE(#extension) IDENTIFIER COLON IDENTIFIER */
 std::unique_ptr<ASTDeclaration> Parser::directive() {
     Token start;
     if (!this->expect(Token::DIRECTIVE, "a directive", &start)) {
@@ -193,7 +194,12 @@ std::unique_ptr<ASTDeclaration> Parser::directive() {
     }
     if (start.fText == "#version") {
         this->expect(Token::INT_LITERAL, "a version number");
-        // ignored for now
+        Token next = this->peek();
+        if (next.fText == "es" || next.fText == "compatibility") {
+            this->nextToken();
+        }
+        // version is ignored for now; it will eventually become an error when we stop pretending
+        // to be GLSL
         return nullptr;
     } else if (start.fText == "#extension") {
         Token name;
diff --git a/src/sksl/SkSLUtil.cpp b/src/sksl/SkSLUtil.cpp
index 327bffe4f1..aefad69367 100644
--- a/src/sksl/SkSLUtil.cpp
+++ b/src/sksl/SkSLUtil.cpp
@@ -9,6 +9,41 @@
 
 namespace SkSL {
 
+std::string to_string(double value) {
+    std::stringstream buffer;
+    buffer << std::setprecision(std::numeric_limits<double>::digits10) << value;
+    std::string result = buffer.str();
+    if (result.find_last_of(".") == std::string::npos && 
+        result.find_last_of("e") == std::string::npos) {
+        result += ".0";
+    }
+    return result;
+}
+
+std::string to_string(int32_t value) {
+    std::stringstream buffer;
+    buffer << value;
+    return buffer.str();
+}
+
+std::string to_string(uint32_t value) {
+    std::stringstream buffer;
+    buffer << value;
+    return buffer.str();
+}
+
+std::string to_string(int64_t value) {
+    std::stringstream buffer;
+    buffer << value;
+    return buffer.str();
+}
+
+std::string to_string(uint64_t value) {
+    std::stringstream buffer;
+    buffer << value;
+    return buffer.str();
+}
+
 int stoi(std::string s) {
     return atoi(s.c_str());
 }
diff --git a/src/sksl/SkSLUtil.h b/src/sksl/SkSLUtil.h
index 33611cde02..efffaaec01 100644
--- a/src/sksl/SkSLUtil.h
+++ b/src/sksl/SkSLUtil.h
@@ -19,11 +19,15 @@ namespace SkSL {
 
 // our own definitions of certain std:: functions, because they are not always present on Android
 
-template <typename T> std::string to_string(T value) {
-    std::stringstream buffer;
-    buffer << std::setprecision(std::numeric_limits<T>::digits10) << value;
-    return buffer.str();
-}
+std::string to_string(double value);
+
+std::string to_string(int32_t value);
+
+std::string to_string(uint32_t value);
+
+std::string to_string(int64_t value);
+
+std::string to_string(uint64_t value);
 
 #if _MSC_VER
 #define NORETURN __declspec(noreturn)
diff --git a/src/sksl/sksl_frag.include b/src/sksl/sksl_frag.include
index b4047fe091..d6c438910f 100644
--- a/src/sksl/sksl_frag.include
+++ b/src/sksl/sksl_frag.include
@@ -4,4 +4,6 @@ STRINGIFY(
 
 layout(builtin=15) in vec4 gl_FragCoord;
 
+layout(builtin=10001) vec4 sk_FragColor;
+
 )
\ No newline at end of file