glslang/hlsl/hlslGrammar.cpp

//
//Copyright (C) 2016 Google, Inc.
//
//All rights reserved.
//
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//modification, are permitted provided that the following conditions
//are met:
//
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//    notice, this list of conditions and the following disclaimer.
//
//    Redistributions in binary form must reproduce the above
//    copyright notice, this list of conditions and the following
//    disclaimer in the documentation and/or other materials provided
//    with the distribution.
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//    contributors may be used to endorse or promote products derived
//    from this software without specific prior written permission.
//
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//"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
//LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
//FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
//COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
//INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
//BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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//LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
//ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
//POSSIBILITY OF SUCH DAMAGE.
//

//
// This is a set of mutually recursive methods implementing the HLSL grammar.
// Generally, each returns
//  - through an argument: a type specifically appropriate to which rule it
//    recognized
//  - through the return value: true/false to indicate whether or not it
//    recognized its rule
//
// As much as possible, only grammar recognition should happen in this file,
// with all other work being farmed out to hlslParseHelper.cpp, which in turn
// will build the AST.
//
// The next token, yet to be "accepted" is always sitting in 'token'.
// When a method says it accepts a rule, that means all tokens involved
// in the rule will have been consumed, and none left in 'token'.
//

#include "hlslTokens.h"
#include "hlslGrammar.h"

namespace glslang {

// Root entry point to this recursive decent parser.
// Return true if compilation unit was successfully accepted.
bool HlslGrammar::parse()
{
    advanceToken();
    return acceptCompilationUnit();
}

void HlslGrammar::expected(const char* syntax)
{
    parseContext.error(token.loc, "Expected", syntax, "");
}

// Only process the next token if it is an identifier.
// Return true if it was an identifier.
bool HlslGrammar::acceptIdentifier(HlslToken& idToken)
{
    if (peekTokenClass(EHTokIdentifier)) {
        idToken = token;
        advanceToken();
        return true;
    }

    return false;
}

// compilationUnit
//      : list of externalDeclaration
//
bool HlslGrammar::acceptCompilationUnit()
{
    TIntermNode* unitNode = nullptr;

    while (! peekTokenClass(EHTokNone)) {
        // externalDeclaration
        TIntermNode* declarationNode;
        if (! acceptDeclaration(declarationNode))
            return false;

        // hook it up
        unitNode = intermediate.growAggregate(unitNode, declarationNode);
    }

    // set root of AST
    intermediate.setTreeRoot(unitNode);

    return true;
}

// declaration
//      : SEMICOLON
//      : fully_specified_type SEMICOLON
//      | fully_specified_type identifier SEMICOLON
//      | fully_specified_type identifier = expression SEMICOLON
//      | fully_specified_type identifier function_parameters SEMICOLON                          // function prototype
//      | fully_specified_type identifier function_parameters COLON semantic compound_statement  // function definition
//
// 'node' could get created if the declaration creates code, like an initializer
// or a function body.
//
bool HlslGrammar::acceptDeclaration(TIntermNode*& node)
{
    node = nullptr;

    // fully_specified_type
    TType type;
    if (! acceptFullySpecifiedType(type))
        return false;

    // identifier
    HlslToken idToken;
    if (acceptIdentifier(idToken)) {
        // = expression
        TIntermTyped* expressionNode = nullptr;
        if (acceptTokenClass(EHTokAssign)) {
            if (! acceptExpression(expressionNode)) {
                expected("initializer");
                return false;
            }
        }

        // SEMICOLON
        if (acceptTokenClass(EHTokSemicolon)) {
            node = parseContext.declareVariable(idToken.loc, *idToken.string, type, 0, expressionNode);
            return true;
        }

        // function_parameters
        TFunction* function = new TFunction(idToken.string, type);
        if (acceptFunctionParameters(*function)) {
            // COLON semantic
            acceptSemantic();

            // compound_statement
            if (peekTokenClass(EHTokLeftBrace))
                return acceptFunctionDefinition(*function, node);

            // SEMICOLON
            if (acceptTokenClass(EHTokSemicolon))
                return true;

            return false;
        }
    }

    // SEMICOLON
    if (acceptTokenClass(EHTokSemicolon))
        return true;

    return true;
}

// fully_specified_type
//      : type_specifier
//      | type_qualifier type_specifier
//
bool HlslGrammar::acceptFullySpecifiedType(TType& type)
{
    // type_qualifier
    TQualifier qualifier;
    qualifier.clear();
    acceptQualifier(qualifier);

    // type_specifier
    if (! acceptType(type))
        return false;
    type.getQualifier() = qualifier;

    return true;
}

// If token is a qualifier, return its token class and advance to the next
// qualifier.  Otherwise, return false, and don't advance.
void HlslGrammar::acceptQualifier(TQualifier& qualifier)
{
    switch (peek()) {
    case EHTokUniform:
        qualifier.storage = EvqUniform;
        break;
    case EHTokConst:
        qualifier.storage = EvqConst;
        break;
    default:
        return;
    }

    advanceToken();
}

// If token is for a type, update 'type' with the type information,
// and return true and advance.
// Otherwise, return false, and don't advance
bool HlslGrammar::acceptType(TType& type)
{
    if (! token.isType)
        return false;

    switch (peek()) {
    case EHTokInt:
    case EHTokInt1:
    case EHTokDword:
        new(&type) TType(EbtInt);
        break;
    case EHTokFloat:
        new(&type) TType(EbtFloat);
        break;

    case EHTokFloat1:
        new(&type) TType(EbtFloat);
        type.makeVector();
        break;

    case EHTokFloat2:
        new(&type) TType(EbtFloat, EvqTemporary, 2);
        break;
    case EHTokFloat3:
        new(&type) TType(EbtFloat, EvqTemporary, 3);
        break;
    case EHTokFloat4:
        new(&type) TType(EbtFloat, EvqTemporary, 4);
        break;

    case EHTokInt2:
        new(&type) TType(EbtInt, EvqTemporary, 2);
        break;
    case EHTokInt3:
        new(&type) TType(EbtInt, EvqTemporary, 3);
        break;
    case EHTokInt4:
        new(&type) TType(EbtInt, EvqTemporary, 4);
        break;

    case EHTokBool2:
        new(&type) TType(EbtBool, EvqTemporary, 2);
        break;
    case EHTokBool3:
        new(&type) TType(EbtBool, EvqTemporary, 3);
        break;
    case EHTokBool4:
        new(&type) TType(EbtBool, EvqTemporary, 4);
        break;

    case EHTokInt1x1:
        new(&type) TType(EbtInt, EvqTemporary, 0, 1, 1);
        break;
    case EHTokInt1x2:
        new(&type) TType(EbtInt, EvqTemporary, 0, 2, 1);
        break;
    case EHTokInt1x3:
        new(&type) TType(EbtInt, EvqTemporary, 0, 3, 1);
        break;
    case EHTokInt1x4:
        new(&type) TType(EbtInt, EvqTemporary, 0, 4, 1);
        break;
    case EHTokInt2x1:
        new(&type) TType(EbtInt, EvqTemporary, 0, 1, 2);
        break;
    case EHTokInt2x2:
        new(&type) TType(EbtInt, EvqTemporary, 0, 2, 2);
        break;
    case EHTokInt2x3:
        new(&type) TType(EbtInt, EvqTemporary, 0, 3, 2);
        break;
    case EHTokInt2x4:
        new(&type) TType(EbtInt, EvqTemporary, 0, 4, 2);
        break;
    case EHTokInt3x1:
        new(&type) TType(EbtInt, EvqTemporary, 0, 1, 3);
        break;
    case EHTokInt3x2:
        new(&type) TType(EbtInt, EvqTemporary, 0, 2, 3);
        break;
    case EHTokInt3x3:
        new(&type) TType(EbtInt, EvqTemporary, 0, 3, 3);
        break;
    case EHTokInt3x4:
        new(&type) TType(EbtInt, EvqTemporary, 0, 4, 3);
        break;
    case EHTokInt4x1:
        new(&type) TType(EbtInt, EvqTemporary, 0, 1, 4);
        break;
    case EHTokInt4x2:
        new(&type) TType(EbtInt, EvqTemporary, 0, 2, 4);
        break;
    case EHTokInt4x3:
        new(&type) TType(EbtInt, EvqTemporary, 0, 3, 4);
        break;
    case EHTokInt4x4:
        new(&type) TType(EbtInt, EvqTemporary, 0, 4, 4);
        break;

    case EHTokFloat1x1:
        new(&type) TType(EbtFloat, EvqTemporary, 0, 1, 1);
        break;
    case EHTokFloat1x2:
        new(&type) TType(EbtFloat, EvqTemporary, 0, 2, 1);
        break;
    case EHTokFloat1x3:
        new(&type) TType(EbtFloat, EvqTemporary, 0, 3, 1);
        break;
    case EHTokFloat1x4:
        new(&type) TType(EbtFloat, EvqTemporary, 0, 4, 1);
        break;
    case EHTokFloat2x1:
        new(&type) TType(EbtFloat, EvqTemporary, 0, 1, 2);
        break;
    case EHTokFloat2x2:
        new(&type) TType(EbtFloat, EvqTemporary, 0, 2, 2);
        break;
    case EHTokFloat2x3:
        new(&type) TType(EbtFloat, EvqTemporary, 0, 3, 2);
        break;
    case EHTokFloat2x4:
        new(&type) TType(EbtFloat, EvqTemporary, 0, 4, 2);
        break;
    case EHTokFloat3x1:
        new(&type) TType(EbtFloat, EvqTemporary, 0, 1, 3);
        break;
    case EHTokFloat3x2:
        new(&type) TType(EbtFloat, EvqTemporary, 0, 2, 3);
        break;
    case EHTokFloat3x3:
        new(&type) TType(EbtFloat, EvqTemporary, 0, 3, 3);
        break;
    case EHTokFloat3x4:
        new(&type) TType(EbtFloat, EvqTemporary, 0, 4, 3);
        break;
    case EHTokFloat4x1:
        new(&type) TType(EbtFloat, EvqTemporary, 0, 1, 4);
        break;
    case EHTokFloat4x2:
        new(&type) TType(EbtFloat, EvqTemporary, 0, 2, 4);
        break;
    case EHTokFloat4x3:
        new(&type) TType(EbtFloat, EvqTemporary, 0, 3, 4);
        break;
    case EHTokFloat4x4:
        new(&type) TType(EbtFloat, EvqTemporary, 0, 4, 4);
        break;

    case EHTokDouble1x1:
        new(&type) TType(EbtDouble, EvqTemporary, 0, 1, 1);
        break;
    case EHTokDouble1x2:
        new(&type) TType(EbtDouble, EvqTemporary, 0, 2, 1);
        break;
    case EHTokDouble1x3:
        new(&type) TType(EbtDouble, EvqTemporary, 0, 3, 1);
        break;
    case EHTokDouble1x4:
        new(&type) TType(EbtDouble, EvqTemporary, 0, 4, 1);
        break;
    case EHTokDouble2x1:
        new(&type) TType(EbtDouble, EvqTemporary, 0, 1, 2);
        break;
    case EHTokDouble2x2:
        new(&type) TType(EbtDouble, EvqTemporary, 0, 2, 2);
        break;
    case EHTokDouble2x3:
        new(&type) TType(EbtDouble, EvqTemporary, 0, 3, 2);
        break;
    case EHTokDouble2x4:
        new(&type) TType(EbtDouble, EvqTemporary, 0, 4, 2);
        break;
    case EHTokDouble3x1:
        new(&type) TType(EbtDouble, EvqTemporary, 0, 1, 3);
        break;
    case EHTokDouble3x2:
        new(&type) TType(EbtDouble, EvqTemporary, 0, 2, 3);
        break;
    case EHTokDouble3x3:
        new(&type) TType(EbtDouble, EvqTemporary, 0, 3, 3);
        break;
    case EHTokDouble3x4:
        new(&type) TType(EbtDouble, EvqTemporary, 0, 4, 3);
        break;
    case EHTokDouble4x1:
        new(&type) TType(EbtDouble, EvqTemporary, 0, 1, 4);
        break;
    case EHTokDouble4x2:
        new(&type) TType(EbtDouble, EvqTemporary, 0, 2, 4);
        break;
    case EHTokDouble4x3:
        new(&type) TType(EbtDouble, EvqTemporary, 0, 3, 4);
        break;
    case EHTokDouble4x4:
        new(&type) TType(EbtDouble, EvqTemporary, 0, 4, 4);
        break;

    default:
        return false;
    }

    advanceToken();

    return true;
}

// function_parameters
//      : LEFT_PAREN parameter_declaration COMMA parameter_declaration ... RIGHT_PAREN
//
bool HlslGrammar::acceptFunctionParameters(TFunction& function)
{
    // LEFT_PAREN
    if (! acceptTokenClass(EHTokLeftParen))
        return false;

    do {
        // parameter_declaration
        if (! acceptParameterDeclaration(function))
            break;

        // COMMA
        if (! acceptTokenClass(EHTokComma))
            break;
    } while (true);

    // RIGHT_PAREN
    if (! acceptTokenClass(EHTokRightParen)) {
        expected("right parenthesis");
        return false;
    }

    return true;
}

// parameter_declaration
//      : fully_specified_type
//      | fully_specified_type identifier
//
bool HlslGrammar::acceptParameterDeclaration(TFunction& function)
{
    // fully_specified_type
    TType* type = new TType;
    if (! acceptFullySpecifiedType(*type))
        return false;

    // identifier
    HlslToken idToken;
    acceptIdentifier(idToken);

    TParameter param = { idToken.string, type };
    function.addParameter(param);

    return true;
}

// Do the work to create the function definition in addition to
// parsing the body (compound_statement).
bool HlslGrammar::acceptFunctionDefinition(TFunction& function, TIntermNode*& node)
{
    TFunction* functionDeclarator = parseContext.handleFunctionDeclarator(token.loc, function, false /* not prototype */);

    // This does a symbol table push
    node = parseContext.handleFunctionDefinition(token.loc, *functionDeclarator);

    // compound_statement
    TIntermAggregate* functionBody = nullptr;
    if (acceptCompoundStatement(functionBody)) {
        node = intermediate.growAggregate(node, functionBody);
        intermediate.setAggregateOperator(node, EOpFunction, functionDeclarator->getType(), token.loc);
        node->getAsAggregate()->setName(functionDeclarator->getMangledName().c_str());
        parseContext.symbolTable.pop(nullptr);

        return true;
    }

    return false;
}

// The top-level full expression recognizer.
//
// expression
//      : assignment_expression COMMA assignment_expression COMMA assignment_expression ...
//
bool HlslGrammar::acceptExpression(TIntermTyped*& node)
{
    // assignment_expression
    if (! acceptAssignmentExpression(node))
        return false;

    if (! peekTokenClass(EHTokComma))
        return true;

    do {
        // ... COMMA
        TSourceLoc loc = token.loc;
        advanceToken();

        // ... assignment_expression
        TIntermTyped* rightNode = nullptr;
        if (! acceptAssignmentExpression(rightNode)) {
            expected("assignment expression");
            return false;
        }

        node = intermediate.addComma(node, rightNode, loc);

        if (! peekTokenClass(EHTokComma))
            return true;
    } while (true);
}

// Accept an assignment expression, where assignment operations
// associate right-to-left.  This is, it is implicit, for example
//
//    a op (b op (c op d))
//
// assigment_expression
//      : binary_expression op binary_expression op binary_expression ...
//
bool HlslGrammar::acceptAssignmentExpression(TIntermTyped*& node)
{
    if (! acceptBinaryExpression(node, PlLogicalOr))
        return false;

    TOperator assignOp = HlslOpMap::assignment(peek());
    if (assignOp == EOpNull)
        return true;

    // ... op
    TSourceLoc loc = token.loc;
    advanceToken();

    // ... binary_expression
    // But, done by recursing this function, which automatically
    // gets the right-to-left associativity.
    TIntermTyped* rightNode = nullptr;
    if (! acceptAssignmentExpression(rightNode)) {
        expected("assignment expression");
        return false;
    }

    node = intermediate.addAssign(assignOp, node, rightNode, loc);

    if (! peekTokenClass(EHTokComma))
        return true;

    return true;
}

// Accept a binary expression, for binary operations that
// associate left-to-right.  This is, it is implicit, for example
//
//    ((a op b) op c) op d
//
// binary_expression
//      : expression op expression op expression ...
//
// where 'expression' is the next higher level in precedence.
//
bool HlslGrammar::acceptBinaryExpression(TIntermTyped*& node, PrecedenceLevel precedenceLevel)
{
    if (precedenceLevel > PlMul)
        return acceptUnaryExpression(node);

    // assignment_expression
    if (! acceptBinaryExpression(node, (PrecedenceLevel)(precedenceLevel + 1)))
        return false;

    TOperator op = HlslOpMap::binary(peek());
    PrecedenceLevel tokenLevel = HlslOpMap::precedenceLevel(op);
    if (tokenLevel < precedenceLevel)
        return true;

    do {
        // ... op
        TSourceLoc loc = token.loc;
        advanceToken();

        // ... expression
        TIntermTyped* rightNode = nullptr;
        if (! acceptBinaryExpression(rightNode, (PrecedenceLevel)(precedenceLevel + 1))) {
            expected("expression");
            return false;
        }

        node = intermediate.addBinaryMath(op, node, rightNode, loc);

        if (! peekTokenClass(EHTokComma))
            return true;
    } while (true);
}

// unary_expression
//      : + unary_expression
//      | - unary_expression
//      | ! unary_expression
//      | ~ unary_expression
//      | ++ unary_expression
//      | -- unary_expression
//      | postfix_expression
//
bool HlslGrammar::acceptUnaryExpression(TIntermTyped*& node)
{
    TOperator unaryOp = HlslOpMap::preUnary(peek());
    
    // postfix_expression
    if (unaryOp == EOpNull)
        return acceptPostfixExpression(node);

    // op unary_expression
    TSourceLoc loc = token.loc;
    advanceToken();
    if (! acceptUnaryExpression(node))
        return false;

    // + is a no-op
    if (unaryOp == EOpAdd)
        return true;

    node = intermediate.addUnaryMath(unaryOp, node, loc);

    return node != nullptr;
}

// postfix_expression
//      : LEFT_PAREN expression RIGHT_PAREN
//      | literal
//      | constructor
//      | identifier
//      | function_call
//      | postfix_expression LEFT_BRACKET integer_expression RIGHT_BRACKET
//      | postfix_expression DOT IDENTIFIER
//      | postfix_expression INC_OP
//      | postfix_expression DEC_OP
//
bool HlslGrammar::acceptPostfixExpression(TIntermTyped*& node)
{
    // Not implemented as self-recursive:
    // The logical "right recursion" is done with an loop at the end

    // idToken will pick up either a variable or a function name in a function call
    HlslToken idToken;

    // LEFT_PAREN expression RIGHT_PAREN
    if (acceptTokenClass(EHTokLeftParen)) {
        if (! acceptExpression(node)) {
            expected("expression");
            return false;
        }
        if (! acceptTokenClass(EHTokRightParen)) {
            expected("right parenthesis");
            return false;
        }
    } else if (acceptLiteral(node)) {
        // literal (nothing else to do yet), go on to the 
    } else if (acceptConstructor(node)) {
        // constructor (nothing else to do yet)
    } else if (acceptIdentifier(idToken)) {
        // identifier or function_call name
        if (! peekTokenClass(EHTokLeftParen)) {
            node = parseContext.handleVariable(idToken.loc, idToken.symbol, token.string);
        } else if (acceptFunctionCall(idToken, node)) {
            // function_call (nothing else to do yet)
        } else {
            expected("function call arguments");
            return false;
        }
    }

    do {
        TSourceLoc loc = token.loc;
        TOperator postOp = HlslOpMap::postUnary(peek());

        // Consume only a valid post-unary operator, otherwise we are done.
        switch (postOp) {
        case EOpIndexDirectStruct:
        case EOpIndexIndirect:
        case EOpPostIncrement:
        case EOpPostDecrement:
            advanceToken();
            break;
        default:
            return true;
        }

        // We have a valid post-unary operator, process it.
        switch (postOp) {
        case EOpIndexDirectStruct:
            // todo
            break;
        case EOpIndexIndirect:
        {
            TIntermTyped* indexNode = nullptr;
            if (! acceptExpression(indexNode) ||
                ! peekTokenClass(EHTokRightBracket)) {
                expected("expression followed by ']'");
                return false;
            }
            // todo:      node = intermediate.addBinaryMath(
        }
        case EOpPostIncrement:
        case EOpPostDecrement:
            node = intermediate.addUnaryMath(postOp, node, loc);
            break;
        default:
            assert(0);
            break;
        }
    } while (true);
}

// constructor
//      : type argument_list
//
bool HlslGrammar::acceptConstructor(TIntermTyped*& node)
{
    // type
    TType type;
    if (acceptType(type)) {
        TFunction* constructorFunction = parseContext.handleConstructorCall(token.loc, type);
        if (constructorFunction == nullptr)
            return false;

        // arguments
        TIntermTyped* arguments = nullptr;
        if (! acceptArguments(constructorFunction, arguments)) {
            expected("constructor arguments");
            return false;
        }

        // hook it up
        node = parseContext.handleFunctionCall(arguments->getLoc(), constructorFunction, arguments);

        return true;
    }

    return false;
}

// The function_call identifier was already recognized, and passed in as idToken.
//
// function_call
//      : [idToken] arguments
//
bool HlslGrammar::acceptFunctionCall(HlslToken idToken, TIntermTyped*& node)
{
    // arguments
    TFunction* function = new TFunction(idToken.string, TType(EbtVoid));
    TIntermTyped* arguments = nullptr;
    if (! acceptArguments(function, arguments))
        return false;

    node = parseContext.handleFunctionCall(idToken.loc, function, arguments);

    return true;
}

// arguments
//      : LEFT_PAREN expression COMMA expression COMMA ... RIGHT_PAREN
//
// The arguments are pushed onto the 'function' argument list and
// onto the 'arguments' aggregate.
//
bool HlslGrammar::acceptArguments(TFunction* function, TIntermTyped*& arguments)
{
    // LEFT_PAREN
    if (! acceptTokenClass(EHTokLeftParen))
        return false;

    do {
        // expression
        TIntermTyped* arg;
        if (! acceptAssignmentExpression(arg))
            break;

        // hook it up
        parseContext.handleFunctionArgument(function, arguments, arg);

        // COMMA
        if (! acceptTokenClass(EHTokComma))
            break;
    } while (true);

    // RIGHT_PAREN
    if (! acceptTokenClass(EHTokRightParen)) {
        expected("right parenthesis");
        return false;
    }

    return true;
}

bool HlslGrammar::acceptLiteral(TIntermTyped*& node)
{
    switch (token.tokenClass) {
    case EHTokIntConstant:
        node = intermediate.addConstantUnion(token.i, token.loc, true);
        break;
    case EHTokFloatConstant:
        node = intermediate.addConstantUnion(token.d, EbtFloat, token.loc, true);
        break;
    case EHTokDoubleConstant:
        node = intermediate.addConstantUnion(token.d, EbtDouble, token.loc, true);
        break;
    case EHTokBoolConstant:
        node = intermediate.addConstantUnion(token.b, token.loc, true);
        break;

    default:
        return false;
    }

    advanceToken();

    return true;
}

// compound_statement
//      : LEFT_CURLY statement statement ... RIGHT_CURLY
//
bool HlslGrammar::acceptCompoundStatement(TIntermAggregate*& compoundStatement)
{
    // LEFT_CURLY
    if (! acceptTokenClass(EHTokLeftBrace))
        return false;

    // statement statement ...
    TIntermNode* statement = nullptr;
    while (acceptStatement(statement)) {
        // hook it up
        compoundStatement = intermediate.growAggregate(compoundStatement, statement);
    }
    if (compoundStatement)
        compoundStatement->setOperator(EOpSequence);

    // RIGHT_CURLY
    return acceptTokenClass(EHTokRightBrace);
}

// statement
//      : compound_statement
//      | return SEMICOLON
//      | return expression SEMICOLON
//      | expression SEMICOLON
//
bool HlslGrammar::acceptStatement(TIntermNode*& statement)
{
    // compound_statement
    TIntermAggregate* compoundStatement = nullptr;
    if (acceptCompoundStatement(compoundStatement)) {
        statement = compoundStatement;
        return true;
    }

    // RETURN
    if (acceptTokenClass(EHTokReturn)) {
        // expression
        TIntermTyped* node;
        if (acceptExpression(node)) {
            // hook it up
            statement = intermediate.addBranch(EOpReturn, node, token.loc);
        } else
            statement = intermediate.addBranch(EOpReturn, token.loc);

        // SEMICOLON
        if (! acceptTokenClass(EHTokSemicolon))
            return false;

        return true;
    }

    // expression
    TIntermTyped* node;
    if (acceptExpression(node))
        statement = node;

    // SEMICOLON
    if (! acceptTokenClass(EHTokSemicolon))
        return false;

    return true;
}

// COLON semantic
bool HlslGrammar::acceptSemantic()
{
    // COLON
    if (acceptTokenClass(EHTokColon)) {
        // semantic
        HlslToken idToken;
        if (! acceptIdentifier(idToken)) {
            expected("semantic");
            return false;
        }
    }

    return true;
}

} // end namespace glslang