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..09fd91e72d2cccfd94e6ea7e94e234c3bce0a756
--- /dev/null
+++ b/src/sksl/SkSLGLSLCodeGenerator.cpp
@@ -0,0 +1,422 @@
+/*
+ * 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 (fAtLineStart) {

[dogben, 2016/07/31 23:20:20]

nit: maybe "if (s[0] == '\0') return;"? Maybe I'm being too OCD, but it bugs me
that writeLine() will indent the empty line.

[ethannicholas, 2016/08/02 16:13:17]

Done.

+        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(std::string s) {
+    this->write(s.c_str());
+}
+
+void GLSLCodeGenerator::writeLine(std::string s) {
+    this->writeLine(s.c_str());
+}
+
+void GLSLCodeGenerator::write(std::string& s) {
+    this->write(s.c_str());
+}
+
+void GLSLCodeGenerator::writeLine(std::string& s) {
+    this->writeLine(s.c_str());
+}
+
+void GLSLCodeGenerator::writeLine() {
+    this->writeLine("");
+}
+
+void GLSLCodeGenerator::writeExtension(Extension& ext) {
+    this->writeLine("#extension " + ext.fName + " : enable");
+}
+
+void GLSLCodeGenerator::writeStruct(const Type& type) {
+    this->writeLine("struct " + type.name() + " {");
+    fIndentation++;
+    for (const auto& f : type.fields()) {
+        this->writeLine(f.fType.name() + " " + f.fName + ";");

[dogben, 2016/07/31 23:20:20]

Missing modifiers?

[ethannicholas, 2016/08/02 16:13:17]

Fixed.

+    }
+    fIndentation--;
+    this->writeLine("};");
+}
+
+void GLSLCodeGenerator::writeExpression(Expression& expr, Precedence parentPrecedence) {
+    switch (expr.fKind) {
+        case Expression::kBinary_Kind:

[dogben, 2016/07/31 23:20:20]

nit: Indentation is inconsistent.

[ethannicholas, 2016/08/02 16:13:17]

Damn you, tabs!

+            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);

[dogben, 2016/07/31 23:20:20]

Don't we need to pass in parentPrecedence? Maybe it doesn't matter because all
postfix operations operate on things that no prefix operations can produce?

[ethannicholas, 2016/08/02 16:13:17]

We sure do!

+			break;
+		case Expression::kPostfix_Kind:
+            this->writePostfixExpression((PostfixExpression&) expr);
+			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(FunctionCall& c) {
+    this->write(c.fFunction.fName + "(");
+    const char* separator = "";
+    for (const auto& arg : c.fArguments) {
+        this->write(separator);
+        separator = ", ";
+        this->writeExpression(*arg, kTopLevel_Precedence);

[dogben, 2016/07/31 23:20:20]

nit: kSequence_Precedence, although it shouldn't matter assuming SkSL will never
support the sequence operator.

Same for writeConstructor.

+    }
+    this->write(")");
+}
+
+void GLSLCodeGenerator::writeConstructor(Constructor& c) {
+    this->write(c.fType.name() + "(");
+    const char* separator = "";
+    for (const auto& arg : c.fArguments) {
+        this->write(separator);
+        separator = ", ";
+        this->writeExpression(*arg, kTopLevel_Precedence);
+    }
+    this->write(")");
+}
+
+void GLSLCodeGenerator::writeVariableReference(VariableReference& ref) {
+    this->write(ref.fVariable.fName);
+}
+
+void GLSLCodeGenerator::writeIndexExpression(IndexExpression& expr) {
+    this->writeExpression(*expr.fBase, kPostfix_Precedence);
+    this->write("[");
+    this->writeExpression(*expr.fIndex, kTopLevel_Precedence);
+    this->write("]");
+}
+
+void GLSLCodeGenerator::writeFieldAccess(FieldAccess& f) {
+    if (!f.fInAnonymousInterfaceBlock) {
+        this->writeExpression(*f.fBase, kPostfix_Precedence);
+        this->write(".");
+    }
+    this->write(f.fBase->fType.fields()[f.fFieldIndex].fName);
+}
+
+void GLSLCodeGenerator::writeSwizzle(Swizzle& swizzle) {
+    this->writeExpression(*swizzle.fBase, kPostfix_Precedence);
+    this->write(".");
+    for (int c : swizzle.fComponents) {
+        this->write(&("x\0y\0z\0w\0"[c * 2]));

[egdaniel, 2016/08/01 13:18:27]

not that functionally it really matters, but is the idea to just always use xyzw
even for colors that we wrote rbga in the shaders?

[ethannicholas, 2016/08/02 16:13:17]

Correct. Since it doesn't matter whether you use rgba / xyzw / stpq when
swizzling, the compiler doesn't actually keep track of which ones you picked.

+    }
+}
+
+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:  return GLSLCodeGenerator::kAssignment_Precedence;
+        default: ABORT("unsupported binary operator");
+    }
+}
+
+void GLSLCodeGenerator::writeBinaryExpression(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(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(PrefixExpression& p) {
+    this->write(Token::OperatorName(p.fOperator));
+    this->writeExpression(*p.fOperand, kPrefix_Precedence);
+}
+
+void GLSLCodeGenerator::writePostfixExpression(PostfixExpression& p) {
+    this->writeExpression(*p.fOperand, kPostfix_Precedence);
+    this->write(Token::OperatorName(p.fOperator));
+}
+
+void GLSLCodeGenerator::writeBoolLiteral(BoolLiteral& b) {
+    this->write(b.fValue ? "true" : "false");
+}
+
+void GLSLCodeGenerator::writeIntLiteral(IntLiteral& i) {
+    this->write(to_string(i.fValue));
+}
+
+void GLSLCodeGenerator::writeFloatLiteral(FloatLiteral& f) {
+    this->write(to_string(f.fValue));

[dogben, 2016/07/31 23:20:19]

Docs for std::to_string say std::to_string(1e-9) == "0.000000", so I don't think
this will work.
http://en.cppreference.com/w/cpp/string/basic_string/to_string

[ethannicholas, 2016/08/02 16:13:17]

My implementation of to_string (note that this is not std::to_string) now always
uses sufficient digits.

+}
+
+void GLSLCodeGenerator::writeFunction(const FunctionDefinition& f) {
+    this->write(f.fDeclaration.fReturnType.name() + " " + f.fDeclaration.fName + "(");
+    const char* separator = "";
+    for (const auto& param : f.fDeclaration.fParameters) {
+        this->write(separator);
+        separator = ", ";
+        this->write(param->fType.name() + " " + param->fName);

[dogben, 2016/07/31 23:20:19]

Missing modifiers and sizes.

[ethannicholas, 2016/08/02 16:13:17]

Fixed.

+    }
+    this->write(") ");
+    this->writeBlock(*f.fBody);
+}
+
+void GLSLCodeGenerator::writeModifiers(const Modifiers& modifiers) {
+    this->write(modifiers.description());
+}
+
+void GLSLCodeGenerator::writeInterfaceBlock(InterfaceBlock& intf) {
+    if (intf.fVariable.fName == "gl_PerVertex") {
+        return;
+    }
+    this->writeModifiers(intf.fVariable.fModifiers);
+    this->writeStruct(intf.fVariable.fType);

[dogben, 2016/07/31 23:20:20]

We're generating a struct for an interface? I don't see how that will work for
anonymous interface fields.

[ethannicholas, 2016/08/02 16:13:17]

Stupid extra "struct" keyword. Fixed.

+}
+
+void GLSLCodeGenerator::writeVarDeclaration(VarDeclaration& decl) {
+    for (size_t i = 0; i < decl.fVars.size(); i++) {
+        if (decl.fVars[i]->fModifiers.fLayout.fBuiltin >= 0) {

[dogben, 2016/07/31 23:20:20]

I don't know what this is about. builtin isn't documented in the GLSL spec or
anywhere in src/sksl.

[ethannicholas, 2016/08/02 16:13:17]

It's from the SPIR-V spec. I've added a comment to that effect.

+            continue;
+        }
+        this->writeModifiers(decl.fVars[i]->fModifiers);
+        this->write(decl.fVars[i]->fType.name() + " " + decl.fVars[i]->fName);

[dogben, 2016/07/31 23:20:20]

If this is a top-level var declaration, fType might need to be a struct
declaration.

Missing sizes.

[ethannicholas, 2016/08/02 16:13:17]

Done.

+        if (decl.fValues[i]) {
+            this->write(" = ");
+            this->writeExpression(*decl.fValues[i], kTopLevel_Precedence);

[dogben, 2016/07/31 23:20:20]

nit: kSequence_Precedence, with same caveat as above.

[ethannicholas, 2016/08/02 16:13:17]

Done.

+        }
+        this->writeLine(";");
+    }
+}
+
+void GLSLCodeGenerator::writeStatement(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->writeLine(";");
+            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->writeLine("break;");
+            break;
+        case Statement::kContinue_Kind:
+            this->writeLine("continue;");
+            break;
+        case Statement::kDiscard_Kind:
+            this->writeLine("discard;");
+            break;
+        default:
+            ABORT("unsupported statement: %s", s.description().c_str());
+    }
+}
+
+void GLSLCodeGenerator::writeBlock(Block& b) {
+    this->writeLine("{");
+    fIndentation++;
+    for (const auto& s : b.fStatements) {
+        this->writeStatement(*s);
+    }
+    fIndentation--;
+    this->writeLine("}");
+}
+
+void GLSLCodeGenerator::writeIfStatement(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(ForStatement& f) {
+    this->write("for (");
+    if (f.fInitializer) {
+        this->writeStatement(*f.fInitializer);
+    }

[dogben, 2016/07/31 23:20:20]

else write semicolon

[ethannicholas, 2016/08/02 16:13:17]

Done.

+    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(WhileStatement& w) {
+    this->write("while (");
+    this->writeExpression(*w.fTest, kTopLevel_Precedence);
+    this->write(") ");
+    this->writeStatement(*w.fStatement);
+}
+
+void GLSLCodeGenerator::writeDoStatement(DoStatement& d) {
+    this->write("do ");
+    this->writeStatement(*d.fStatement);
+    this->write("while (");
+    this->writeExpression(*d.fTest, kTopLevel_Precedence);
+    this->writeLine(");");
+}
+
+void GLSLCodeGenerator::writeReturnStatement(ReturnStatement& r) {
+    this->write("return");
+    if (r.fExpression) {
+        this->write(" ");
+        this->writeExpression(*r.fExpression, kTopLevel_Precedence);
+    }
+    this->writeLine(";");
+}
+
+void GLSLCodeGenerator::generateCode(Program& program, std::ostream& out) {
+    ASSERT(fOut == nullptr);
+    fOut = &out;
+    this->write("#version " + to_string(fCaps.fVersion));
+    if (fCaps.fStandard == GLCaps::kGLES_Standard) {

[egdaniel, 2016/08/01 13:18:27]

I don't see fCaps used anywhere else so why split it into int and enum? Why not
just have a version string that includes the whole thing?

[ethannicholas, 2016/08/02 16:13:17]

Going to start paying a lot more attention to it in the next change. Right now
this is just "this basically produces correct GLSL". I have to go from that to
"this produces correct GLSL / GLSL ES for every single device we support", and
for that I need to know the version and 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:
+                this->writeVarDeclaration((VarDeclaration&) *e);
+                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;
+}
+
+}