src/compiler/translator/FoldExpressions.cpp

//
// Copyright (c) 2018 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.
//
// FoldExpressions.cpp: Fold expressions. This may fold expressions so that the qualifier of the
// folded node differs from the qualifier of the original expression, so it needs to be done after
// parsing and validation of qualifiers is complete. Expressions that are folded:
//  1. Ternary ops with a constant condition.
//  2. Sequence aka comma ops where the left side has no side effects.
//  3. Any expressions containing any of the above.

#include "compiler/translator/FoldExpressions.h"

#include "compiler/translator/Diagnostics.h"
#include "compiler/translator/IntermNode.h"
#include "compiler/translator/IntermTraverse.h"

namespace sh
{

namespace
{

class FoldExpressionsTraverser : public TIntermTraverser
{
  public:
    FoldExpressionsTraverser(TDiagnostics *diagnostics)
        : TIntermTraverser(true, false, false), mDiagnostics(diagnostics), mDidReplace(false)
    {
    }

    bool didReplace() { return mDidReplace; }

    void nextIteration() { mDidReplace = false; }

  protected:
    bool visitTernary(Visit visit, TIntermTernary *node) override
    {
        TIntermTyped *folded = node->fold(mDiagnostics);
        if (folded != node)
        {
            queueReplacement(folded, OriginalNode::IS_DROPPED);
            mDidReplace = true;
            return false;
        }
        return true;
    }

    bool visitAggregate(Visit visit, TIntermAggregate *node) override
    {
        TIntermTyped *folded = node->fold(mDiagnostics);
        if (folded != node)
        {
            queueReplacement(folded, OriginalNode::IS_DROPPED);
            mDidReplace = true;
            return false;
        }
        return true;
    }

    bool visitBinary(Visit visit, TIntermBinary *node) override
    {
        TIntermTyped *folded = node->fold(mDiagnostics);
        if (folded != node)
        {
            queueReplacement(folded, OriginalNode::IS_DROPPED);
            mDidReplace = true;
            return false;
        }
        return true;
    }

    bool visitUnary(Visit visit, TIntermUnary *node) override
    {
        TIntermTyped *folded = node->fold(mDiagnostics);
        if (folded != node)
        {
            queueReplacement(folded, OriginalNode::IS_DROPPED);
            mDidReplace = true;
            return false;
        }
        return true;
    }

    bool visitSwizzle(Visit visit, TIntermSwizzle *node) override
    {
        TIntermTyped *folded = node->fold(mDiagnostics);
        if (folded != node)
        {
            queueReplacement(folded, OriginalNode::IS_DROPPED);
            mDidReplace = true;
            return false;
        }
        return true;
    }

  private:
    TDiagnostics *mDiagnostics;
    bool mDidReplace;
};

}  // anonymous namespace

void FoldExpressions(TIntermBlock *root, TDiagnostics *diagnostics)
{
    FoldExpressionsTraverser traverser(diagnostics);
    do
    {
        traverser.nextIteration();
        root->traverse(&traverser);
        traverser.updateTree();
    } while (traverser.didReplace());
}

}  // namespace sh