added initial GLSL support to skslc

src/sksl/SkSLGLSLCodeGenerator.cpp

Index: src/sksl/SkSLGLSLCodeGenerator.cpp
diff --git a/src/sksl/SkSLGLSLCodeGenerator.cpp b/src/sksl/SkSLGLSLCodeGenerator.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..b725a2f48e5ea8bef85a51164c90dedb841df3ed
--- /dev/null
+++ b/src/sksl/SkSLGLSLCodeGenerator.cpp
@@ -0,0 +1,470 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+ 
+#include "SkSLGLSLCodeGenerator.h"
+
+#include "string.h"
+
+#include "GLSL.std.450.h"
+
+#include "ir/SkSLExpressionStatement.h"
+#include "ir/SkSLExtension.h"
+#include "ir/SkSLIndexExpression.h"
+#include "ir/SkSLVariableReference.h"
+
+namespace SkSL {
+
+void GLSLCodeGenerator::write(const char* s) {
+    if (s[0] == 0) {
+        return;
+    }
+    if (fAtLineStart) {
+        for (int i = 0; i < fIndentation; i++) {
+            *fOut << "    ";
+        }
+    }
+    *fOut << s;
+    fAtLineStart = false;
+}
+
+void GLSLCodeGenerator::writeLine(const char* s) {
+    this->write(s);
+    *fOut << "\n";
+    fAtLineStart = true;
+}
+
+void GLSLCodeGenerator::write(const std::string& s) {
+    this->write(s.c_str());
+}
+
+void GLSLCodeGenerator::writeLine(const std::string& s) {
+    this->writeLine(s.c_str());
+}
+
+void GLSLCodeGenerator::writeLine() {
+    this->writeLine("");
+}
+
+void GLSLCodeGenerator::writeExtension(const Extension& ext) {
+    this->writeLine("#extension " + ext.fName + " : enable");
+}
+
+void GLSLCodeGenerator::writeType(const Type& type) {
+    if (type.kind() == Type::kStruct_Kind) {
+        this->writeLine("struct " + type.name() + " {");
+        fIndentation++;
+        for (const auto& f : type.fields()) {
+            this->writeModifiers(f.fModifiers);
+            this->writeType(f.fType);

[dogben, 2016/08/02 18:08:15]

Example from the GLSL spec:
struct S { float f; };
struct T {
    S; // Error: anonymous structures disallowed
    struct { ... }; // Error: embedded structures disallowed
    S s; // Okay: nested structures with name are allowed
};

If someone writes #3 (nested structures with name are allowed) in SkSL, you will
output #2 (embedded structures disallowed) as GLSL.

I think you may run into a similar problem with variable declarations, e.g.:
struct S { float f; };
S first_var;
S second_var;

would become:
struct S { float f; } first_var;
struct S { float f; } second_var;

which would cause a redefinition error.

[ethannicholas, 2016/08/02 20:43:06]

Good catch, fixed.

+            this->writeLine(" " + f.fName + ";");
+        }
+        fIndentation--;
+        this->writeLine("}");
+    } else {
+        this->write(type.name());

[dogben, 2016/08/02 18:08:15]

Maybe add a comment that array sizes are part of the type name.

[ethannicholas, 2016/08/02 20:43:06]

Done.

+    }
+}
+
+void GLSLCodeGenerator::writeExpression(const Expression& expr, Precedence parentPrecedence) {
+    switch (expr.fKind) {
+        case Expression::kBinary_Kind:
+            this->writeBinaryExpression((BinaryExpression&) expr, parentPrecedence);
+            break;
+        case Expression::kBoolLiteral_Kind:
+            this->writeBoolLiteral((BoolLiteral&) expr);
+            break;
+        case Expression::kConstructor_Kind:
+            this->writeConstructor((Constructor&) expr);
+            break;
+        case Expression::kIntLiteral_Kind:
+            this->writeIntLiteral((IntLiteral&) expr);
+            break;
+        case Expression::kFieldAccess_Kind:
+            this->writeFieldAccess(((FieldAccess&) expr));
+            break;
+        case Expression::kFloatLiteral_Kind:
+            this->writeFloatLiteral(((FloatLiteral&) expr));
+            break;
+        case Expression::kFunctionCall_Kind:
+            this->writeFunctionCall((FunctionCall&) expr);
+            break;
+        case Expression::kPrefix_Kind:
+            this->writePrefixExpression((PrefixExpression&) expr, parentPrecedence);
+            break;
+        case Expression::kPostfix_Kind:
+            this->writePostfixExpression((PostfixExpression&) expr, parentPrecedence);
+            break;
+        case Expression::kSwizzle_Kind:
+            this->writeSwizzle((Swizzle&) expr);
+            break;
+        case Expression::kVariableReference_Kind:
+            this->writeVariableReference((VariableReference&) expr);
+            break;
+        case Expression::kTernary_Kind:
+            this->writeTernaryExpression((TernaryExpression&) expr, parentPrecedence);
+            break;
+        case Expression::kIndex_Kind:
+            this->writeIndexExpression((IndexExpression&) expr);
+            break;
+        default:
+            ABORT("unsupported expression: %s", expr.description().c_str());
+    }
+}
+
+void GLSLCodeGenerator::writeFunctionCall(const FunctionCall& c) {
+    this->write(c.fFunction.fName + "(");
+    const char* separator = "";
+    for (const auto& arg : c.fArguments) {
+        this->write(separator);
+        separator = ", ";
+        this->writeExpression(*arg, kSequence_Precedence);
+    }
+    this->write(")");
+}
+
+void GLSLCodeGenerator::writeConstructor(const Constructor& c) {
+    this->write(c.fType.name() + "(");
+    const char* separator = "";
+    for (const auto& arg : c.fArguments) {
+        this->write(separator);
+        separator = ", ";
+        this->writeExpression(*arg, kSequence_Precedence);
+    }
+    this->write(")");
+}
+
+void GLSLCodeGenerator::writeVariableReference(const VariableReference& ref) {
+    this->write(ref.fVariable.fName);
+}
+
+void GLSLCodeGenerator::writeIndexExpression(const IndexExpression& expr) {
+    this->writeExpression(*expr.fBase, kPostfix_Precedence);
+    this->write("[");
+    this->writeExpression(*expr.fIndex, kTopLevel_Precedence);
+    this->write("]");
+}
+
+void GLSLCodeGenerator::writeFieldAccess(const FieldAccess& f) {
+    if (f.fOwnerKind == FieldAccess::kDefault_OwnerKind) {
+        this->writeExpression(*f.fBase, kPostfix_Precedence);
+        this->write(".");
+    }
+    this->write(f.fBase->fType.fields()[f.fFieldIndex].fName);
+}
+
+void GLSLCodeGenerator::writeSwizzle(const Swizzle& swizzle) {
+    this->writeExpression(*swizzle.fBase, kPostfix_Precedence);
+    this->write(".");
+    for (int c : swizzle.fComponents) {
+        this->write(&("x\0y\0z\0w\0"[c * 2]));
+    }
+}
+
+static GLSLCodeGenerator::Precedence get_binary_precedence(Token::Kind op) {
+    switch (op) {
+        case Token::STAR:         // fall through
+        case Token::SLASH:        // fall through
+        case Token::PERCENT:      return GLSLCodeGenerator::kMultiplicative_Precedence;
+        case Token::PLUS:         // fall through
+        case Token::MINUS:        return GLSLCodeGenerator::kAdditive_Precedence;
+        case Token::SHL:          // fall through
+        case Token::SHR:          return GLSLCodeGenerator::kShift_Precedence;
+        case Token::LT:           // fall through
+        case Token::GT:           // fall through
+        case Token::LTEQ:         // fall through
+        case Token::GTEQ:         return GLSLCodeGenerator::kRelational_Precedence;
+        case Token::EQEQ:         // fall through
+        case Token::NEQ:          return GLSLCodeGenerator::kEquality_Precedence;
+        case Token::BITWISEAND:   return GLSLCodeGenerator::kBitwiseAnd_Precedence;
+        case Token::BITWISEXOR:   return GLSLCodeGenerator::kBitwiseXor_Precedence;
+        case Token::BITWISEOR:    return GLSLCodeGenerator::kBitwiseOr_Precedence;
+        case Token::LOGICALAND:   return GLSLCodeGenerator::kLogicalAnd_Precedence;
+        case Token::LOGICALXOR:   return GLSLCodeGenerator::kLogicalXor_Precedence;
+        case Token::LOGICALOR:    return GLSLCodeGenerator::kLogicalOr_Precedence;
+        case Token::EQ:           // fall through
+        case Token::PLUSEQ:       // fall through
+        case Token::MINUSEQ:      // fall through
+        case Token::STAREQ:       // fall through
+        case Token::SLASHEQ:      // fall through
+        case Token::PERCENTEQ:    // fall through
+        case Token::SHLEQ:        // fall through
+        case Token::SHREQ:        // fall through
+        case Token::LOGICALANDEQ: // fall through
+        case Token::LOGICALXOREQ: // fall through
+        case Token::LOGICALOREQ:  // fall through
+        case Token::BITWISEANDEQ: // fall through
+        case Token::BITWISEXOREQ: // fall through
+        case Token::BITWISEOREQ:  return GLSLCodeGenerator::kAssignment_Precedence;
+        default: ABORT("unsupported binary operator");
+    }
+}
+
+void GLSLCodeGenerator::writeBinaryExpression(const BinaryExpression& b, 
+                                              Precedence parentPrecedence) {
+    Precedence precedence = get_binary_precedence(b.fOperator);
+    if (precedence >= parentPrecedence) {
+        this->write("(");
+    }
+    this->writeExpression(*b.fLeft, precedence);
+    this->write(" " + Token::OperatorName(b.fOperator) + " ");
+    this->writeExpression(*b.fRight, precedence);
+    if (precedence >= parentPrecedence) {
+        this->write(")");
+    }
+}
+
+void GLSLCodeGenerator::writeTernaryExpression(const TernaryExpression& t, 
+                                               Precedence parentPrecedence) {
+    if (kTernary_Precedence >= parentPrecedence) {
+        this->write("(");
+    }
+    this->writeExpression(*t.fTest, kTernary_Precedence);
+    this->write(" ? ");
+    this->writeExpression(*t.fIfTrue, kTernary_Precedence);
+    this->write(" : ");
+    this->writeExpression(*t.fIfFalse, kTernary_Precedence);
+    if (kTernary_Precedence >= parentPrecedence) {
+        this->write(")");
+    }
+}
+
+void GLSLCodeGenerator::writePrefixExpression(const PrefixExpression& p, 
+                                              Precedence parentPrecedence) {
+    if (kPrefix_Precedence >= parentPrecedence) {
+        this->write("(");
+    }
+    this->write(Token::OperatorName(p.fOperator));
+    this->writeExpression(*p.fOperand, kPrefix_Precedence);
+    if (kPrefix_Precedence >= parentPrecedence) {
+        this->write(")");
+    }
+}
+
+void GLSLCodeGenerator::writePostfixExpression(const PostfixExpression& p, 
+                                               Precedence parentPrecedence) {
+    if (kPostfix_Precedence >= parentPrecedence) {
+        this->write("(");
+    }
+    this->writeExpression(*p.fOperand, kPostfix_Precedence);
+    this->write(Token::OperatorName(p.fOperator));
+    if (kPostfix_Precedence >= parentPrecedence) {
+        this->write(")");
+    }
+}
+
+void GLSLCodeGenerator::writeBoolLiteral(const BoolLiteral& b) {
+    this->write(b.fValue ? "true" : "false");
+}
+
+void GLSLCodeGenerator::writeIntLiteral(const IntLiteral& i) {
+    this->write(to_string(i.fValue));
+}
+
+void GLSLCodeGenerator::writeFloatLiteral(const FloatLiteral& f) {
+    this->write(to_string(f.fValue));
+}
+
+void GLSLCodeGenerator::writeFunction(const FunctionDefinition& f) {
+    this->writeType(f.fDeclaration.fReturnType);
+    this->write(" " + f.fDeclaration.fName + "(");
+    const char* separator = "";
+    for (const auto& param : f.fDeclaration.fParameters) {
+        this->write(separator);
+        separator = ", ";
+        this->writeModifiers(param->fModifiers);
+        this->writeType(param->fType);
+        this->write(" " + param->fName);
+    }
+    this->write(") ");
+    this->writeBlock(*f.fBody);
+    this->writeLine();
+}
+
+void GLSLCodeGenerator::writeModifiers(const Modifiers& modifiers) {
+    this->write(modifiers.description());
+}
+
+void GLSLCodeGenerator::writeInterfaceBlock(const InterfaceBlock& intf) {
+    if (intf.fVariable.fName == "gl_PerVertex") {
+        return;
+    }
+    this->writeModifiers(intf.fVariable.fModifiers);
+    this->writeLine(intf.fVariable.fType.name() + " {");
+    fIndentation++;
+    for (const auto& f : intf.fVariable.fType.fields()) {
+        this->writeModifiers(f.fModifiers);
+        this->writeType(f.fType);
+        this->writeLine(" " + f.fName + ";");
+    }
+    fIndentation--;
+    this->writeLine("};");
+}
+
+void GLSLCodeGenerator::writeVarDeclaration(const VarDeclaration& decl) {
+    ASSERT(decl.fVars.size() > 0);
+    this->writeModifiers(decl.fVars[0]->fModifiers);
+    this->writeType(decl.fBaseType);
+    std::string separator = " ";
+    for (size_t i = 0; i < decl.fVars.size(); i++) {
+        ASSERT(decl.fVars[i]->fModifiers == decl.fVars[0]->fModifiers);
+        this->write(separator);
+        separator = ", ";
+        this->write(decl.fVars[i]->fName);
+        for (const auto& size : decl.fSizes[i]) {
+            this->write("[");
+            this->writeExpression(*size, kTopLevel_Precedence);
+            this->write("]");
+        }
+        if (decl.fValues[i]) {
+            this->write(" = ");
+            this->writeExpression(*decl.fValues[i], kTopLevel_Precedence);
+        }
+    }
+    this->write(";");
+}
+
+void GLSLCodeGenerator::writeStatement(const Statement& s) {
+    switch (s.fKind) {
+        case Statement::kBlock_Kind:
+            this->writeBlock((Block&) s);
+            break;
+        case Statement::kExpression_Kind:
+            this->writeExpression(*((ExpressionStatement&) s).fExpression, kTopLevel_Precedence);
+            this->write(";");
+            break;
+        case Statement::kReturn_Kind: 
+            this->writeReturnStatement((ReturnStatement&) s);
+            break;
+        case Statement::kVarDeclaration_Kind:
+            this->writeVarDeclaration(*((VarDeclarationStatement&) s).fDeclaration);
+            break;
+        case Statement::kIf_Kind:
+            this->writeIfStatement((IfStatement&) s);
+            break;
+        case Statement::kFor_Kind:
+            this->writeForStatement((ForStatement&) s);
+            break;
+        case Statement::kWhile_Kind:
+            this->writeWhileStatement((WhileStatement&) s);
+            break;
+        case Statement::kDo_Kind:
+            this->writeDoStatement((DoStatement&) s);
+            break;
+        case Statement::kBreak_Kind:
+            this->write("break;");
+            break;
+        case Statement::kContinue_Kind:
+            this->write("continue;");
+            break;
+        case Statement::kDiscard_Kind:
+            this->write("discard;");
+            break;
+        default:
+            ABORT("unsupported statement: %s", s.description().c_str());
+    }
+}
+
+void GLSLCodeGenerator::writeBlock(const Block& b) {
+    this->writeLine("{");
+    fIndentation++;
+    for (const auto& s : b.fStatements) {
+        this->writeStatement(*s);
+        this->writeLine();
+    }
+    fIndentation--;
+    this->write("}");
+}
+
+void GLSLCodeGenerator::writeIfStatement(const IfStatement& stmt) {
+    this->write("if (");
+    this->writeExpression(*stmt.fTest, kTopLevel_Precedence);
+    this->write(") ");
+    this->writeStatement(*stmt.fIfTrue);
+    if (stmt.fIfFalse) {
+        this->write(" else ");
+        this->writeStatement(*stmt.fIfFalse);
+    }
+}
+
+void GLSLCodeGenerator::writeForStatement(const ForStatement& f) {
+    this->write("for (");
+    if (f.fInitializer) {
+        this->writeStatement(*f.fInitializer);
+    } else {
+        this->write("; ");
+    }
+    if (f.fTest) {
+        this->writeExpression(*f.fTest, kTopLevel_Precedence);
+    }
+    this->write("; ");
+    if (f.fNext) {
+        this->writeExpression(*f.fNext, kTopLevel_Precedence);
+    }
+    this->write(") ");
+    this->writeStatement(*f.fStatement);
+}
+
+void GLSLCodeGenerator::writeWhileStatement(const WhileStatement& w) {
+    this->write("while (");
+    this->writeExpression(*w.fTest, kTopLevel_Precedence);
+    this->write(") ");
+    this->writeStatement(*w.fStatement);
+}
+
+void GLSLCodeGenerator::writeDoStatement(const DoStatement& d) {
+    this->write("do ");
+    this->writeStatement(*d.fStatement);
+    this->write(" while (");
+    this->writeExpression(*d.fTest, kTopLevel_Precedence);
+    this->write(");");
+}
+
+void GLSLCodeGenerator::writeReturnStatement(const ReturnStatement& r) {
+    this->write("return");
+    if (r.fExpression) {
+        this->write(" ");
+        this->writeExpression(*r.fExpression, kTopLevel_Precedence);
+    }
+    this->write(";");
+}
+
+void GLSLCodeGenerator::generateCode(const Program& program, std::ostream& out) {
+    ASSERT(fOut == nullptr);
+    fOut = &out;
+    this->write("#version " + to_string(fCaps.fVersion));
+    if (fCaps.fStandard == GLCaps::kGLES_Standard) {
+        this->write(" es");
+    }
+    this->writeLine();
+    for (const auto& e : program.fElements) {
+        switch (e->fKind) {
+            case ProgramElement::kExtension_Kind:
+                this->writeExtension((Extension&) *e);
+                break;
+            case ProgramElement::kVar_Kind: {
+                VarDeclaration& decl = (VarDeclaration&) *e;
+                if (decl.fVars.size() > 0 && decl.fVars[0]->fModifiers.fLayout.fBuiltin == -1) {
+                    this->writeVarDeclaration(decl);
+                    this->writeLine();
+                }
+                break;
+            }
+            case ProgramElement::kInterfaceBlock_Kind:
+                this->writeInterfaceBlock((InterfaceBlock&) *e);
+                break;
+            case ProgramElement::kFunction_Kind:
+                this->writeFunction((FunctionDefinition&) *e);
+                break;
+            default:
+                printf("%s\n", e->description().c_str());
+                ABORT("unsupported program element");
+        }
+    }
+    fOut = nullptr;
+}
+
+}