src/compiler/ValidateLimitations.cpp - external/angle - Git at Google

 //
 // Copyright (c) 2002-2010 The ANGLE Project Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //

 #include "compiler/ValidateLimitations.h"
 #include "compiler/InfoSink.h"
 #include "compiler/InitializeParseContext.h"
 #include "compiler/ParseContext.h"

 namespace {
 bool IsLoopIndex(const TIntermSymbol* symbol, const TLoopStack& stack) {
     for (TLoopStack::const_iterator i = stack.begin(); i != stack.end(); ++i) {
         if (i->index.id == symbol->getId())
             return true;
     }
     return false;
 }

 void MarkLoopForUnroll(const TIntermSymbol* symbol, TLoopStack& stack) {
     for (TLoopStack::iterator i = stack.begin(); i != stack.end(); ++i) {
         if (i->index.id == symbol->getId()) {
             ASSERT(i->loop != NULL);
             i->loop->setUnrollFlag(true);
             return;
         }
     }
     UNREACHABLE();
 }

 // Traverses a node to check if it represents a constant index expression.
 // Definition:
 // constant-index-expressions are a superset of constant-expressions.
 // Constant-index-expressions can include loop indices as defined in
 // GLSL ES 1.0 spec, Appendix A, section 4.
 // The following are constant-index-expressions:
 // - Constant expressions
 // - Loop indices as defined in section 4
 // - Expressions composed of both of the above
 class ValidateConstIndexExpr : public TIntermTraverser {
 public:
     ValidateConstIndexExpr(const TLoopStack& stack)
         : mValid(true), mLoopStack(stack) {}

     // Returns true if the parsed node represents a constant index expression.
     bool isValid() const { return mValid; }

     virtual void visitSymbol(TIntermSymbol* symbol) {
         // Only constants and loop indices are allowed in a
         // constant index expression.
         if (mValid) {
             mValid = (symbol->getQualifier() == EvqConst) ||
                      IsLoopIndex(symbol, mLoopStack);
         }
     }

 private:
     bool mValid;
     const TLoopStack& mLoopStack;
 };

 // Traverses a node to check if it uses a loop index.
 // If an int loop index is used in its body as a sampler array index,
 // mark the loop for unroll.
 class ValidateLoopIndexExpr : public TIntermTraverser {
 public:
     ValidateLoopIndexExpr(TLoopStack& stack)
         : mUsesFloatLoopIndex(false),
           mUsesIntLoopIndex(false),
           mLoopStack(stack) {}

     bool usesFloatLoopIndex() const { return mUsesFloatLoopIndex; }
     bool usesIntLoopIndex() const { return mUsesIntLoopIndex; }

     virtual void visitSymbol(TIntermSymbol* symbol) {
         if (IsLoopIndex(symbol, mLoopStack)) {
             switch (symbol->getBasicType()) {
               case EbtFloat:
                 mUsesFloatLoopIndex = true;
                 break;
               case EbtInt:
                 mUsesIntLoopIndex = true;
                 MarkLoopForUnroll(symbol, mLoopStack);
                 break;
               default:
                 UNREACHABLE();
             }
         }
     }

 private:
     bool mUsesFloatLoopIndex;
     bool mUsesIntLoopIndex;
     TLoopStack& mLoopStack;
 };
 }  // namespace

 ValidateLimitations::ValidateLimitations(ShShaderType shaderType,
                                          TInfoSinkBase& sink)
     : mShaderType(shaderType),
       mSink(sink),
       mNumErrors(0)
 {
 }

 bool ValidateLimitations::visitBinary(Visit, TIntermBinary* node)
 {
     // Check if loop index is modified in the loop body.
     validateOperation(node, node->getLeft());

     // Check indexing.
     switch (node->getOp()) {
       case EOpIndexDirect:
         validateIndexing(node);
         break;
       case EOpIndexIndirect:
 #if defined(__APPLE__)
         // Loop unrolling is a work-around for a Mac Cg compiler bug where it
         // crashes when a sampler array's index is also the loop index.
         // Once Apple fixes this bug, we should remove the code in this CL.
         // See http://codereview.appspot.com/4331048/.
         if ((node->getLeft() != NULL) && (node->getRight() != NULL) &&
             (node->getLeft()->getAsSymbolNode())) {
             TIntermSymbol* symbol = node->getLeft()->getAsSymbolNode();
             if (IsSampler(symbol->getBasicType()) && symbol->isArray()) {
                 ValidateLoopIndexExpr validate(mLoopStack);
                 node->getRight()->traverse(&validate);
                 if (validate.usesFloatLoopIndex()) {
                     error(node->getLine(),
                           "sampler array index is float loop index",
                           "for");
                 }
             }
         }
 #endif
         validateIndexing(node);
         break;
       default: break;
     }
     return true;
 }

 bool ValidateLimitations::visitUnary(Visit, TIntermUnary* node)
 {
     // Check if loop index is modified in the loop body.
     validateOperation(node, node->getOperand());

     return true;
 }

 bool ValidateLimitations::visitAggregate(Visit, TIntermAggregate* node)
 {
     switch (node->getOp()) {
       case EOpFunctionCall:
         validateFunctionCall(node);
         break;
       default:
         break;
     }
     return true;
 }

 bool ValidateLimitations::visitLoop(Visit, TIntermLoop* node)
 {
     if (!validateLoopType(node))
         return false;

     TLoopInfo info;
     memset(&info, 0, sizeof(TLoopInfo));
     info.loop = node;
     if (!validateForLoopHeader(node, &info))
         return false;

     TIntermNode* body = node->getBody();
     if (body != NULL) {
         mLoopStack.push_back(info);
         body->traverse(this);
         mLoopStack.pop_back();
     }

     // The loop is fully processed - no need to visit children.
     return false;
 }

 void ValidateLimitations::error(TSourceLoc loc,
                                 const char *reason, const char* token)
 {
     mSink.prefix(EPrefixError);
     mSink.location(loc);
     mSink << "'" << token << "' : " << reason << "\n";
     ++mNumErrors;
 }

 bool ValidateLimitations::withinLoopBody() const
 {
     return !mLoopStack.empty();
 }

 bool ValidateLimitations::isLoopIndex(const TIntermSymbol* symbol) const
 {
     return IsLoopIndex(symbol, mLoopStack);
 }

 bool ValidateLimitations::validateLoopType(TIntermLoop* node) {
     TLoopType type = node->getType();
     if (type == ELoopFor)
         return true;

     // Reject while and do-while loops.
     error(node->getLine(),
           "This type of loop is not allowed",
           type == ELoopWhile ? "while" : "do");
     return false;
 }

 bool ValidateLimitations::validateForLoopHeader(TIntermLoop* node,
                                                 TLoopInfo* info)
 {
     ASSERT(node->getType() == ELoopFor);

     //
     // The for statement has the form:
     //    for ( init-declaration ; condition ; expression ) statement
     //
     if (!validateForLoopInit(node, info))
         return false;
     if (!validateForLoopCond(node, info))
         return false;
     if (!validateForLoopExpr(node, info))
         return false;

     return true;
 }

 bool ValidateLimitations::validateForLoopInit(TIntermLoop* node,
                                               TLoopInfo* info)
 {
     TIntermNode* init = node->getInit();
     if (init == NULL) {
         error(node->getLine(), "Missing init declaration", "for");
         return false;
     }

     //
     // init-declaration has the form:
     //     type-specifier identifier = constant-expression
     //
     TIntermAggregate* decl = init->getAsAggregate();
     if ((decl == NULL) || (decl->getOp() != EOpDeclaration)) {
         error(init->getLine(), "Invalid init declaration", "for");
         return false;
     }
     // To keep things simple do not allow declaration list.
     TIntermSequence& declSeq = decl->getSequence();
     if (declSeq.size() != 1) {
         error(decl->getLine(), "Invalid init declaration", "for");
         return false;
     }
     TIntermBinary* declInit = declSeq[0]->getAsBinaryNode();
     if ((declInit == NULL) || (declInit->getOp() != EOpInitialize)) {
         error(decl->getLine(), "Invalid init declaration", "for");
         return false;
     }
     TIntermSymbol* symbol = declInit->getLeft()->getAsSymbolNode();
     if (symbol == NULL) {
         error(declInit->getLine(), "Invalid init declaration", "for");
         return false;
     }
     // The loop index has type int or float.
     TBasicType type = symbol->getBasicType();
     if ((type != EbtInt) && (type != EbtFloat)) {
         error(symbol->getLine(),
               "Invalid type for loop index", getBasicString(type));
         return false;
     }
     // The loop index is initialized with constant expression.
     if (!isConstExpr(declInit->getRight())) {
         error(declInit->getLine(),
               "Loop index cannot be initialized with non-constant expression",
               symbol->getSymbol().c_str());
         return false;
     }

     info->index.id = symbol->getId();
     return true;
 }

 bool ValidateLimitations::validateForLoopCond(TIntermLoop* node,
                                               TLoopInfo* info)
 {
     TIntermNode* cond = node->getCondition();
     if (cond == NULL) {
         error(node->getLine(), "Missing condition", "for");
         return false;
     }
     //
     // condition has the form:
     //     loop_index relational_operator constant_expression
     //
     TIntermBinary* binOp = cond->getAsBinaryNode();
     if (binOp == NULL) {
         error(node->getLine(), "Invalid condition", "for");
         return false;
     }
     // Loop index should be to the left of relational operator.
     TIntermSymbol* symbol = binOp->getLeft()->getAsSymbolNode();
     if (symbol == NULL) {
         error(binOp->getLine(), "Invalid condition", "for");
         return false;
     }
     if (symbol->getId() != info->index.id) {
         error(symbol->getLine(),
               "Expected loop index", symbol->getSymbol().c_str());
         return false;
     }
     // Relational operator is one of: > >= < <= == or !=.
     switch (binOp->getOp()) {
       case EOpEqual:
       case EOpNotEqual:
       case EOpLessThan:
       case EOpGreaterThan:
       case EOpLessThanEqual:
       case EOpGreaterThanEqual:
         break;
       default:
         error(binOp->getLine(),
               "Invalid relational operator",
               getOperatorString(binOp->getOp()));
         break;
     }
     // Loop index must be compared with a constant.
     if (!isConstExpr(binOp->getRight())) {
         error(binOp->getLine(),
               "Loop index cannot be compared with non-constant expression",
               symbol->getSymbol().c_str());
         return false;
     }

     return true;
 }

 bool ValidateLimitations::validateForLoopExpr(TIntermLoop* node,
                                               TLoopInfo* info)
 {
     TIntermNode* expr = node->getExpression();
     if (expr == NULL) {
         error(node->getLine(), "Missing expression", "for");
         return false;
     }

     // for expression has one of the following forms:
     //     loop_index++
     //     loop_index--
     //     loop_index += constant_expression
     //     loop_index -= constant_expression
     //     ++loop_index
     //     --loop_index
     // The last two forms are not specified in the spec, but I am assuming
     // its an oversight.
     TIntermUnary* unOp = expr->getAsUnaryNode();
     TIntermBinary* binOp = unOp ? NULL : expr->getAsBinaryNode();

     TOperator op = EOpNull;
     TIntermSymbol* symbol = NULL;
     if (unOp != NULL) {
         op = unOp->getOp();
         symbol = unOp->getOperand()->getAsSymbolNode();
     } else if (binOp != NULL) {
         op = binOp->getOp();
         symbol = binOp->getLeft()->getAsSymbolNode();
     }

     // The operand must be loop index.
     if (symbol == NULL) {
         error(expr->getLine(), "Invalid expression", "for");
         return false;
     }
     if (symbol->getId() != info->index.id) {
         error(symbol->getLine(),
               "Expected loop index", symbol->getSymbol().c_str());
         return false;
     }

     // The operator is one of: ++ -- += -=.
     switch (op) {
         case EOpPostIncrement:
         case EOpPostDecrement:
         case EOpPreIncrement:
         case EOpPreDecrement:
             ASSERT((unOp != NULL) && (binOp == NULL));
             break;
         case EOpAddAssign:
         case EOpSubAssign:
             ASSERT((unOp == NULL) && (binOp != NULL));
             break;
         default:
             error(expr->getLine(), "Invalid operator", getOperatorString(op));
             return false;
     }

     // Loop index must be incremented/decremented with a constant.
     if (binOp != NULL) {
         if (!isConstExpr(binOp->getRight())) {
             error(binOp->getLine(),
                   "Loop index cannot be modified by non-constant expression",
                   symbol->getSymbol().c_str());
             return false;
         }
     }

     return true;
 }

 bool ValidateLimitations::validateFunctionCall(TIntermAggregate* node)
 {
     ASSERT(node->getOp() == EOpFunctionCall);

     // If not within loop body, there is nothing to check.
     if (!withinLoopBody())
         return true;

     // List of param indices for which loop indices are used as argument.
     typedef std::vector<size_t> ParamIndex;
     ParamIndex pIndex;
     TIntermSequence& params = node->getSequence();
     for (TIntermSequence::size_type i = 0; i < params.size(); ++i) {
         TIntermSymbol* symbol = params[i]->getAsSymbolNode();
         if (symbol && isLoopIndex(symbol))
             pIndex.push_back(i);
     }
     // If none of the loop indices are used as arguments,
     // there is nothing to check.
     if (pIndex.empty())
         return true;

     bool valid = true;
     TSymbolTable& symbolTable = GetGlobalParseContext()->symbolTable;
     TSymbol* symbol = symbolTable.find(node->getName());
     ASSERT(symbol && symbol->isFunction());
     TFunction* function = static_cast<TFunction*>(symbol);
     for (ParamIndex::const_iterator i = pIndex.begin();
          i != pIndex.end(); ++i) {
         const TParameter& param = function->getParam(*i);
         TQualifier qual = param.type->getQualifier();
         if ((qual == EvqOut) || (qual == EvqInOut)) {
             error(params[*i]->getLine(),
                   "Loop index cannot be used as argument to a function out or inout parameter",
                   params[*i]->getAsSymbolNode()->getSymbol().c_str());
             valid = false;
         }
     }

     return valid;
 }

 bool ValidateLimitations::validateOperation(TIntermOperator* node,
                                             TIntermNode* operand) {
     // Check if loop index is modified in the loop body.
     if (!withinLoopBody() || !node->modifiesState())
         return true;

     const TIntermSymbol* symbol = operand->getAsSymbolNode();
     if (symbol && isLoopIndex(symbol)) {
         error(node->getLine(),
               "Loop index cannot be statically assigned to within the body of the loop",
               symbol->getSymbol().c_str());
     }
     return true;
 }

 bool ValidateLimitations::isConstExpr(TIntermNode* node)
 {
     ASSERT(node != NULL);
     return node->getAsConstantUnion() != NULL;
 }

 bool ValidateLimitations::isConstIndexExpr(TIntermNode* node)
 {
     ASSERT(node != NULL);

     ValidateConstIndexExpr validate(mLoopStack);
     node->traverse(&validate);
     return validate.isValid();
 }

 bool ValidateLimitations::validateIndexing(TIntermBinary* node)
 {
     ASSERT((node->getOp() == EOpIndexDirect) ||
            (node->getOp() == EOpIndexIndirect));

     bool valid = true;
     TIntermTyped* index = node->getRight();
     // The index expression must have integral type.
     if (!index->isScalar() || (index->getBasicType() != EbtInt)) {
         error(index->getLine(),
               "Index expression must have integral type",
               index->getCompleteString().c_str());
         valid = false;
     }
     // The index expession must be a constant-index-expression unless
     // the operand is a uniform in a vertex shader.
     TIntermTyped* operand = node->getLeft();
     bool skip = (mShaderType == SH_VERTEX_SHADER) &&
                 (operand->getQualifier() == EvqUniform);
     if (!skip && !isConstIndexExpr(index)) {
         error(index->getLine(), "Index expression must be constant", "[]");
         valid = false;
     }
     return valid;
 }
	//
	// Copyright (c) 2002-2010 The ANGLE Project Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.
	//

	#include "compiler/ValidateLimitations.h"
	#include "compiler/InfoSink.h"
	#include "compiler/InitializeParseContext.h"
	#include "compiler/ParseContext.h"

	namespace {
	bool IsLoopIndex(const TIntermSymbol* symbol, const TLoopStack& stack) {
	for (TLoopStack::const_iterator i = stack.begin(); i != stack.end(); ++i) {
	if (i->index.id == symbol->getId())
	return true;
	}
	return false;
	}

	void MarkLoopForUnroll(const TIntermSymbol* symbol, TLoopStack& stack) {
	for (TLoopStack::iterator i = stack.begin(); i != stack.end(); ++i) {
	if (i->index.id == symbol->getId()) {
	ASSERT(i->loop != NULL);
	i->loop->setUnrollFlag(true);
	return;
	}
	}
	UNREACHABLE();
	}

	// Traverses a node to check if it represents a constant index expression.
	// Definition:
	// constant-index-expressions are a superset of constant-expressions.
	// Constant-index-expressions can include loop indices as defined in
	// GLSL ES 1.0 spec, Appendix A, section 4.
	// The following are constant-index-expressions:
	// - Constant expressions
	// - Loop indices as defined in section 4
	// - Expressions composed of both of the above
	class ValidateConstIndexExpr : public TIntermTraverser {
	public:
	ValidateConstIndexExpr(const TLoopStack& stack)
	: mValid(true), mLoopStack(stack) {}

	// Returns true if the parsed node represents a constant index expression.
	bool isValid() const { return mValid; }

	virtual void visitSymbol(TIntermSymbol* symbol) {
	// Only constants and loop indices are allowed in a
	// constant index expression.
	if (mValid) {
	mValid = (symbol->getQualifier() == EvqConst) \|\|
	IsLoopIndex(symbol, mLoopStack);
	}
	}

	private:
	bool mValid;
	const TLoopStack& mLoopStack;
	};

	// Traverses a node to check if it uses a loop index.
	// If an int loop index is used in its body as a sampler array index,
	// mark the loop for unroll.
	class ValidateLoopIndexExpr : public TIntermTraverser {
	public:
	ValidateLoopIndexExpr(TLoopStack& stack)
	: mUsesFloatLoopIndex(false),
	mUsesIntLoopIndex(false),
	mLoopStack(stack) {}

	bool usesFloatLoopIndex() const { return mUsesFloatLoopIndex; }
	bool usesIntLoopIndex() const { return mUsesIntLoopIndex; }

	virtual void visitSymbol(TIntermSymbol* symbol) {
	if (IsLoopIndex(symbol, mLoopStack)) {
	switch (symbol->getBasicType()) {
	case EbtFloat:
	mUsesFloatLoopIndex = true;
	break;
	case EbtInt:
	mUsesIntLoopIndex = true;
	MarkLoopForUnroll(symbol, mLoopStack);
	break;
	default:
	UNREACHABLE();
	}
	}
	}

	private:
	bool mUsesFloatLoopIndex;
	bool mUsesIntLoopIndex;
	TLoopStack& mLoopStack;
	};
	} // namespace

	ValidateLimitations::ValidateLimitations(ShShaderType shaderType,
	TInfoSinkBase& sink)
	: mShaderType(shaderType),
	mSink(sink),
	mNumErrors(0)
	{
	}

	bool ValidateLimitations::visitBinary(Visit, TIntermBinary* node)
	{
	// Check if loop index is modified in the loop body.
	validateOperation(node, node->getLeft());

	// Check indexing.
	switch (node->getOp()) {
	case EOpIndexDirect:
	validateIndexing(node);
	break;
	case EOpIndexIndirect:
	#if defined(__APPLE__)
	// Loop unrolling is a work-around for a Mac Cg compiler bug where it
	// crashes when a sampler array's index is also the loop index.
	// Once Apple fixes this bug, we should remove the code in this CL.
	// See http://codereview.appspot.com/4331048/.
	if ((node->getLeft() != NULL) && (node->getRight() != NULL) &&
	(node->getLeft()->getAsSymbolNode())) {
	TIntermSymbol* symbol = node->getLeft()->getAsSymbolNode();
	if (IsSampler(symbol->getBasicType()) && symbol->isArray()) {
	ValidateLoopIndexExpr validate(mLoopStack);
	node->getRight()->traverse(&validate);
	if (validate.usesFloatLoopIndex()) {
	error(node->getLine(),
	"sampler array index is float loop index",
	"for");
	}
	}
	}
	#endif
	validateIndexing(node);
	break;
	default: break;
	}
	return true;
	}

	bool ValidateLimitations::visitUnary(Visit, TIntermUnary* node)
	{
	// Check if loop index is modified in the loop body.
	validateOperation(node, node->getOperand());

	return true;
	}

	bool ValidateLimitations::visitAggregate(Visit, TIntermAggregate* node)
	{
	switch (node->getOp()) {
	case EOpFunctionCall:
	validateFunctionCall(node);
	break;
	default:
	break;
	}
	return true;
	}

	bool ValidateLimitations::visitLoop(Visit, TIntermLoop* node)
	{
	if (!validateLoopType(node))
	return false;

	TLoopInfo info;
	memset(&info, 0, sizeof(TLoopInfo));
	info.loop = node;
	if (!validateForLoopHeader(node, &info))
	return false;

	TIntermNode* body = node->getBody();
	if (body != NULL) {
	mLoopStack.push_back(info);
	body->traverse(this);
	mLoopStack.pop_back();
	}

	// The loop is fully processed - no need to visit children.
	return false;
	}

	void ValidateLimitations::error(TSourceLoc loc,
	const char reason, const char token)
	{
	mSink.prefix(EPrefixError);
	mSink.location(loc);
	mSink << "'" << token << "' : " << reason << "\n";
	++mNumErrors;
	}

	bool ValidateLimitations::withinLoopBody() const
	{
	return !mLoopStack.empty();
	}

	bool ValidateLimitations::isLoopIndex(const TIntermSymbol* symbol) const
	{
	return IsLoopIndex(symbol, mLoopStack);
	}

	bool ValidateLimitations::validateLoopType(TIntermLoop* node) {
	TLoopType type = node->getType();
	if (type == ELoopFor)
	return true;

	// Reject while and do-while loops.
	error(node->getLine(),
	"This type of loop is not allowed",
	type == ELoopWhile ? "while" : "do");
	return false;
	}

	bool ValidateLimitations::validateForLoopHeader(TIntermLoop* node,
	TLoopInfo* info)
	{
	ASSERT(node->getType() == ELoopFor);

	//
	// The for statement has the form:
	// for ( init-declaration ; condition ; expression ) statement
	//
	if (!validateForLoopInit(node, info))
	return false;
	if (!validateForLoopCond(node, info))
	return false;
	if (!validateForLoopExpr(node, info))
	return false;

	return true;
	}

	bool ValidateLimitations::validateForLoopInit(TIntermLoop* node,
	TLoopInfo* info)
	{
	TIntermNode* init = node->getInit();
	if (init == NULL) {
	error(node->getLine(), "Missing init declaration", "for");
	return false;
	}

	//
	// init-declaration has the form:
	// type-specifier identifier = constant-expression
	//
	TIntermAggregate* decl = init->getAsAggregate();
	if ((decl == NULL) \|\| (decl->getOp() != EOpDeclaration)) {
	error(init->getLine(), "Invalid init declaration", "for");
	return false;
	}
	// To keep things simple do not allow declaration list.
	TIntermSequence& declSeq = decl->getSequence();
	if (declSeq.size() != 1) {
	error(decl->getLine(), "Invalid init declaration", "for");
	return false;
	}
	TIntermBinary* declInit = declSeq[0]->getAsBinaryNode();
	if ((declInit == NULL) \|\| (declInit->getOp() != EOpInitialize)) {
	error(decl->getLine(), "Invalid init declaration", "for");
	return false;
	}
	TIntermSymbol* symbol = declInit->getLeft()->getAsSymbolNode();
	if (symbol == NULL) {
	error(declInit->getLine(), "Invalid init declaration", "for");
	return false;
	}
	// The loop index has type int or float.
	TBasicType type = symbol->getBasicType();
	if ((type != EbtInt) && (type != EbtFloat)) {
	error(symbol->getLine(),
	"Invalid type for loop index", getBasicString(type));
	return false;
	}
	// The loop index is initialized with constant expression.
	if (!isConstExpr(declInit->getRight())) {
	error(declInit->getLine(),
	"Loop index cannot be initialized with non-constant expression",
	symbol->getSymbol().c_str());
	return false;
	}

	info->index.id = symbol->getId();
	return true;
	}

	bool ValidateLimitations::validateForLoopCond(TIntermLoop* node,
	TLoopInfo* info)
	{
	TIntermNode* cond = node->getCondition();
	if (cond == NULL) {
	error(node->getLine(), "Missing condition", "for");
	return false;
	}
	//
	// condition has the form:
	// loop_index relational_operator constant_expression
	//
	TIntermBinary* binOp = cond->getAsBinaryNode();
	if (binOp == NULL) {
	error(node->getLine(), "Invalid condition", "for");
	return false;
	}
	// Loop index should be to the left of relational operator.
	TIntermSymbol* symbol = binOp->getLeft()->getAsSymbolNode();
	if (symbol == NULL) {
	error(binOp->getLine(), "Invalid condition", "for");
	return false;
	}
	if (symbol->getId() != info->index.id) {
	error(symbol->getLine(),
	"Expected loop index", symbol->getSymbol().c_str());
	return false;
	}
	// Relational operator is one of: > >= < <= == or !=.
	switch (binOp->getOp()) {
	case EOpEqual:
	case EOpNotEqual:
	case EOpLessThan:
	case EOpGreaterThan:
	case EOpLessThanEqual:
	case EOpGreaterThanEqual:
	break;
	default:
	error(binOp->getLine(),
	"Invalid relational operator",
	getOperatorString(binOp->getOp()));
	break;
	}
	// Loop index must be compared with a constant.
	if (!isConstExpr(binOp->getRight())) {
	error(binOp->getLine(),
	"Loop index cannot be compared with non-constant expression",
	symbol->getSymbol().c_str());
	return false;
	}

	return true;
	}

	bool ValidateLimitations::validateForLoopExpr(TIntermLoop* node,
	TLoopInfo* info)
	{
	TIntermNode* expr = node->getExpression();
	if (expr == NULL) {
	error(node->getLine(), "Missing expression", "for");
	return false;
	}

	// for expression has one of the following forms:
	// loop_index++
	// loop_index--
	// loop_index += constant_expression
	// loop_index -= constant_expression
	// ++loop_index
	// --loop_index
	// The last two forms are not specified in the spec, but I am assuming
	// its an oversight.
	TIntermUnary* unOp = expr->getAsUnaryNode();
	TIntermBinary* binOp = unOp ? NULL : expr->getAsBinaryNode();

	TOperator op = EOpNull;
	TIntermSymbol* symbol = NULL;
	if (unOp != NULL) {
	op = unOp->getOp();
	symbol = unOp->getOperand()->getAsSymbolNode();
	} else if (binOp != NULL) {
	op = binOp->getOp();
	symbol = binOp->getLeft()->getAsSymbolNode();
	}

	// The operand must be loop index.
	if (symbol == NULL) {
	error(expr->getLine(), "Invalid expression", "for");
	return false;
	}
	if (symbol->getId() != info->index.id) {
	error(symbol->getLine(),
	"Expected loop index", symbol->getSymbol().c_str());
	return false;
	}

	// The operator is one of: ++ -- += -=.
	switch (op) {
	case EOpPostIncrement:
	case EOpPostDecrement:
	case EOpPreIncrement:
	case EOpPreDecrement:
	ASSERT((unOp != NULL) && (binOp == NULL));
	break;
	case EOpAddAssign:
	case EOpSubAssign:
	ASSERT((unOp == NULL) && (binOp != NULL));
	break;
	default:
	error(expr->getLine(), "Invalid operator", getOperatorString(op));
	return false;
	}

	// Loop index must be incremented/decremented with a constant.
	if (binOp != NULL) {
	if (!isConstExpr(binOp->getRight())) {
	error(binOp->getLine(),
	"Loop index cannot be modified by non-constant expression",
	symbol->getSymbol().c_str());
	return false;
	}
	}

	return true;
	}

	bool ValidateLimitations::validateFunctionCall(TIntermAggregate* node)
	{
	ASSERT(node->getOp() == EOpFunctionCall);

	// If not within loop body, there is nothing to check.
	if (!withinLoopBody())
	return true;

	// List of param indices for which loop indices are used as argument.
	typedef std::vector<size_t> ParamIndex;
	ParamIndex pIndex;
	TIntermSequence& params = node->getSequence();
	for (TIntermSequence::size_type i = 0; i < params.size(); ++i) {
	TIntermSymbol* symbol = params[i]->getAsSymbolNode();
	if (symbol && isLoopIndex(symbol))
	pIndex.push_back(i);
	}
	// If none of the loop indices are used as arguments,
	// there is nothing to check.
	if (pIndex.empty())
	return true;

	bool valid = true;
	TSymbolTable& symbolTable = GetGlobalParseContext()->symbolTable;
	TSymbol* symbol = symbolTable.find(node->getName());
	ASSERT(symbol && symbol->isFunction());
	TFunction* function = static_cast<TFunction*>(symbol);
	for (ParamIndex::const_iterator i = pIndex.begin();
	i != pIndex.end(); ++i) {
	const TParameter& param = function->getParam(*i);
	TQualifier qual = param.type->getQualifier();
	if ((qual == EvqOut) \|\| (qual == EvqInOut)) {
	error(params[*i]->getLine(),
	"Loop index cannot be used as argument to a function out or inout parameter",
	params[*i]->getAsSymbolNode()->getSymbol().c_str());
	valid = false;
	}
	}

	return valid;
	}

	bool ValidateLimitations::validateOperation(TIntermOperator* node,
	TIntermNode* operand) {
	// Check if loop index is modified in the loop body.
	if (!withinLoopBody() \|\| !node->modifiesState())
	return true;

	const TIntermSymbol* symbol = operand->getAsSymbolNode();
	if (symbol && isLoopIndex(symbol)) {
	error(node->getLine(),
	"Loop index cannot be statically assigned to within the body of the loop",
	symbol->getSymbol().c_str());
	}
	return true;
	}

	bool ValidateLimitations::isConstExpr(TIntermNode* node)
	{
	ASSERT(node != NULL);
	return node->getAsConstantUnion() != NULL;
	}

	bool ValidateLimitations::isConstIndexExpr(TIntermNode* node)
	{
	ASSERT(node != NULL);

	ValidateConstIndexExpr validate(mLoopStack);
	node->traverse(&validate);
	return validate.isValid();
	}

	bool ValidateLimitations::validateIndexing(TIntermBinary* node)
	{
	ASSERT((node->getOp() == EOpIndexDirect) \|\|
	(node->getOp() == EOpIndexIndirect));

	bool valid = true;
	TIntermTyped* index = node->getRight();
	// The index expression must have integral type.
	if (!index->isScalar() \|\| (index->getBasicType() != EbtInt)) {
	error(index->getLine(),
	"Index expression must have integral type",
	index->getCompleteString().c_str());
	valid = false;
	}
	// The index expession must be a constant-index-expression unless
	// the operand is a uniform in a vertex shader.
	TIntermTyped* operand = node->getLeft();
	bool skip = (mShaderType == SH_VERTEX_SHADER) &&
	(operand->getQualifier() == EvqUniform);
	if (!skip && !isConstIndexExpr(index)) {
	error(index->getLine(), "Index expression must be constant", "[]");
	valid = false;
	}
	return valid;
	}