src/compiler/translator/Intermediate.cpp

//
// Copyright (c) 2002-2014 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.
//

//
// Build the intermediate representation.
//

#include <float.h>
#include <limits.h>
#include <algorithm>

#include "compiler/translator/Intermediate.h"
#include "compiler/translator/SymbolTable.h"

////////////////////////////////////////////////////////////////////////////
//
// First set of functions are to help build the intermediate representation.
// These functions are not member functions of the nodes.
// They are called from parser productions.
//
/////////////////////////////////////////////////////////////////////////////

//
// Add a terminal node for an identifier in an expression.
//
// Returns the added node.
//
TIntermSymbol *TIntermediate::addSymbol(
    int id, const TString &name, const TType &type, const TSourceLoc &line)
{
    TIntermSymbol *node = new TIntermSymbol(id, name, type);
    node->setLine(line);

    return node;
}

//
// Connect two nodes through an index operator, where the left node is the base
// of an array or struct, and the right node is a direct or indirect offset.
//
// Returns the added node.
// The caller should set the type of the returned node.
//
TIntermTyped *TIntermediate::addIndex(TOperator op,
                                      TIntermTyped *base,
                                      TIntermTyped *index,
                                      const TSourceLoc &line,
                                      TDiagnostics *diagnostics)
{
    TIntermBinary *node = new TIntermBinary(op, base, index);
    node->setLine(line);

    TIntermTyped *folded = node->fold(diagnostics);
    if (folded)
    {
        return folded;
    }

    return node;
}

//
// This is the safe way to change the operator on an aggregate, as it
// does lots of error checking and fixing.  Especially for establishing
// a function call's operation on it's set of parameters.  Sequences
// of instructions are also aggregates, but they just direnctly set
// their operator to EOpSequence.
//
// Returns an aggregate node, which could be the one passed in if
// it was already an aggregate but no operator was set.
//
TIntermAggregate *TIntermediate::setAggregateOperator(
    TIntermNode *node, TOperator op, const TSourceLoc &line)
{
    TIntermAggregate *aggNode;

    //
    // Make sure we have an aggregate.  If not turn it into one.
    //
    if (node)
    {
        aggNode = node->getAsAggregate();
        if (aggNode == NULL || aggNode->getOp() != EOpNull)
        {
            //
            // Make an aggregate containing this node.
            //
            aggNode = new TIntermAggregate();
            aggNode->getSequence()->push_back(node);
        }
    }
    else
    {
        aggNode = new TIntermAggregate();
    }

    //
    // Set the operator.
    //
    aggNode->setOp(op);
    aggNode->setLine(line);

    return aggNode;
}

//
// Safe way to combine two nodes into an aggregate.  Works with null pointers,
// a node that's not a aggregate yet, etc.
//
// Returns the resulting aggregate, unless 0 was passed in for
// both existing nodes.
//
TIntermAggregate *TIntermediate::growAggregate(
    TIntermNode *left, TIntermNode *right, const TSourceLoc &line)
{
    if (left == NULL && right == NULL)
        return NULL;

    TIntermAggregate *aggNode = NULL;
    if (left)
        aggNode = left->getAsAggregate();
    if (!aggNode || aggNode->getOp() != EOpNull)
    {
        aggNode = new TIntermAggregate;
        if (left)
            aggNode->getSequence()->push_back(left);
    }

    if (right)
        aggNode->getSequence()->push_back(right);

    aggNode->setLine(line);

    return aggNode;
}

//
// Turn an existing node into an aggregate.
//
// Returns an aggregate, unless NULL was passed in for the existing node.
//
TIntermAggregate *TIntermediate::MakeAggregate(TIntermNode *node, const TSourceLoc &line)
{
    if (node == nullptr)
        return nullptr;

    TIntermAggregate *aggNode = new TIntermAggregate;
    aggNode->getSequence()->push_back(node);

    aggNode->setLine(line);

    return aggNode;
}

// If the input node is nullptr, return nullptr.
// If the input node is a sequence (block) node, return it.
// If the input node is not a sequence node, put it inside a sequence node and return that.
TIntermAggregate *TIntermediate::EnsureSequence(TIntermNode *node)
{
    if (node == nullptr)
        return nullptr;
    TIntermAggregate *aggNode = node->getAsAggregate();
    if (aggNode != nullptr && aggNode->getOp() == EOpSequence)
        return aggNode;

    aggNode = MakeAggregate(node, node->getLine());
    aggNode->setOp(EOpSequence);
    return aggNode;
}

// For "if" test nodes.  There are three children; a condition,
// a true path, and a false path.  The two paths are in the
// nodePair.
//
// Returns the node created.
TIntermNode *TIntermediate::addIfElse(TIntermTyped *cond,
                                      TIntermNodePair nodePair,
                                      const TSourceLoc &line)
{
    // For compile time constant conditions, prune the code now.

    if (cond->getAsConstantUnion())
    {
        if (cond->getAsConstantUnion()->getBConst(0) == true)
        {
            return nodePair.node1 ? setAggregateOperator(nodePair.node1, EOpSequence,
                                                         nodePair.node1->getLine())
                                  : nullptr;
        }
        else
        {
            return nodePair.node2 ? setAggregateOperator(nodePair.node2, EOpSequence,
                                                         nodePair.node2->getLine())
                                  : nullptr;
        }
    }

    TIntermIfElse *node =
        new TIntermIfElse(cond, EnsureSequence(nodePair.node1), EnsureSequence(nodePair.node2));
    node->setLine(line);

    return node;
}

TIntermTyped *TIntermediate::addComma(TIntermTyped *left,
                                      TIntermTyped *right,
                                      const TSourceLoc &line,
                                      int shaderVersion)
{
    TQualifier resultQualifier = EvqConst;
    // ESSL3.00 section 12.43: The result of a sequence operator is not a constant-expression.
    if (shaderVersion >= 300 || left->getQualifier() != EvqConst ||
        right->getQualifier() != EvqConst)
    {
        resultQualifier = EvqTemporary;
    }

    TIntermTyped *commaNode = nullptr;
    if (!left->hasSideEffects())
    {
        commaNode = right;
    }
    else
    {
        commaNode = growAggregate(left, right, line);
        commaNode->getAsAggregate()->setOp(EOpComma);
        commaNode->setType(right->getType());
    }
    commaNode->getTypePointer()->setQualifier(resultQualifier);
    return commaNode;
}

// For "?:" test nodes.  There are three children; a condition,
// a true path, and a false path.  The two paths are specified
// as separate parameters.
//
// Returns the ternary node created, or one of trueExpression and falseExpression if the expression
// could be folded.
TIntermTyped *TIntermediate::AddTernarySelection(TIntermTyped *cond,
                                                 TIntermTyped *trueExpression,
                                                 TIntermTyped *falseExpression,
                                                 const TSourceLoc &line)
{
    // Note that the node resulting from here can be a constant union without being qualified as
    // constant.
    if (cond->getAsConstantUnion())
    {
        TQualifier resultQualifier =
            TIntermTernary::DetermineQualifier(cond, trueExpression, falseExpression);
        if (cond->getAsConstantUnion()->getBConst(0))
        {
            trueExpression->getTypePointer()->setQualifier(resultQualifier);
            return trueExpression;
        }
        else
        {
            falseExpression->getTypePointer()->setQualifier(resultQualifier);
            return falseExpression;
        }
    }

    // Make a ternary node.
    TIntermTernary *node = new TIntermTernary(cond, trueExpression, falseExpression);
    node->setLine(line);

    return node;
}

TIntermSwitch *TIntermediate::addSwitch(
    TIntermTyped *init, TIntermAggregate *statementList, const TSourceLoc &line)
{
    TIntermSwitch *node = new TIntermSwitch(init, statementList);
    node->setLine(line);

    return node;
}

TIntermCase *TIntermediate::addCase(
    TIntermTyped *condition, const TSourceLoc &line)
{
    TIntermCase *node = new TIntermCase(condition);
    node->setLine(line);

    return node;
}

//
// Constant terminal nodes.  Has a union that contains bool, float or int constants
//
// Returns the constant union node created.
//

TIntermConstantUnion *TIntermediate::addConstantUnion(const TConstantUnion *constantUnion,
                                                      const TType &type,
                                                      const TSourceLoc &line)
{
    TIntermConstantUnion *node = new TIntermConstantUnion(constantUnion, type);
    node->setLine(line);

    return node;
}

TIntermTyped *TIntermediate::AddSwizzle(TIntermTyped *baseExpression,
                                        const TVectorFields &fields,
                                        const TSourceLoc &dotLocation)
{
    TVector<int> fieldsVector;
    for (int i = 0; i < fields.num; ++i)
    {
        fieldsVector.push_back(fields.offsets[i]);
    }
    TIntermSwizzle *node = new TIntermSwizzle(baseExpression, fieldsVector);
    node->setLine(dotLocation);

    TIntermTyped *folded = node->fold();
    if (folded)
    {
        return folded;
    }

    return node;
}

//
// Create loop nodes.
//
TIntermNode *TIntermediate::addLoop(
    TLoopType type, TIntermNode *init, TIntermTyped *cond, TIntermTyped *expr,
    TIntermNode *body, const TSourceLoc &line)
{
    TIntermNode *node = new TIntermLoop(type, init, cond, expr, EnsureSequence(body));
    node->setLine(line);

    return node;
}

//
// Add branches.
//
TIntermBranch* TIntermediate::addBranch(
    TOperator branchOp, const TSourceLoc &line)
{
    return addBranch(branchOp, 0, line);
}

TIntermBranch* TIntermediate::addBranch(
    TOperator branchOp, TIntermTyped *expression, const TSourceLoc &line)
{
    TIntermBranch *node = new TIntermBranch(branchOp, expression);
    node->setLine(line);

    return node;
}

//
// This is to be executed once the final root is put on top by the parsing
// process.
//
TIntermAggregate *TIntermediate::PostProcess(TIntermNode *root)
{
    if (root == nullptr)
        return nullptr;

    //
    // Finish off the top level sequence, if any
    //
    TIntermAggregate *aggRoot = root->getAsAggregate();
    if (aggRoot != nullptr && aggRoot->getOp() == EOpNull)
    {
        aggRoot->setOp(EOpSequence);
    }
    else if (aggRoot == nullptr || aggRoot->getOp() != EOpSequence)
    {
        aggRoot = new TIntermAggregate(EOpSequence);
        aggRoot->setLine(root->getLine());
        aggRoot->getSequence()->push_back(root);
    }

    return aggRoot;
}

TIntermTyped *TIntermediate::foldAggregateBuiltIn(TIntermAggregate *aggregate,
                                                  TDiagnostics *diagnostics)
{
    switch (aggregate->getOp())
    {
        case EOpAtan:
        case EOpPow:
        case EOpMod:
        case EOpMin:
        case EOpMax:
        case EOpClamp:
        case EOpMix:
        case EOpStep:
        case EOpSmoothStep:
        case EOpMul:
        case EOpOuterProduct:
        case EOpLessThan:
        case EOpLessThanEqual:
        case EOpGreaterThan:
        case EOpGreaterThanEqual:
        case EOpVectorEqual:
        case EOpVectorNotEqual:
        case EOpDistance:
        case EOpDot:
        case EOpCross:
        case EOpFaceForward:
        case EOpReflect:
        case EOpRefract:
            return aggregate->fold(diagnostics);
        default:
            // TODO: Add support for folding array constructors
            if (aggregate->isConstructor() && !aggregate->isArray())
            {
                return aggregate->fold(diagnostics);
            }
            // Constant folding not supported for the built-in.
            return nullptr;
    }
}