RewriteRepeatedAssignToSwizzled.cpp

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//

// Copyright 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.

//

// RewriteRepeatedAssignToSwizzled.cpp: Rewrite expressions that assign an assignment to a swizzled

// vector, like:

//     v.x = z = expression;

// to:

//     z = expression;

//     v.x = z;

//

// Note that this doesn't handle some corner cases: expressions nested inside other expressions,

// inside loop headers, or inside if conditions.

#include "compiler/translator/tree_ops/gl/RewriteRepeatedAssignToSwizzled.h"

#include "compiler/translator/tree_util/IntermNode_util.h"

#include "compiler/translator/tree_util/IntermTraverse.h"

namespace sh

namespace

class RewriteAssignToSwizzledTraverser : public TIntermTraverser

  public:

    [[nodiscard]] static bool rewrite(TCompiler *compiler, TIntermBlock *root);

  private:

    RewriteAssignToSwizzledTraverser();

    bool visitBinary(Visit, TIntermBinary *node) override;

    void nextIteration();

    bool didRewrite() { return mDidRewrite; }

    bool mDidRewrite;

};

// static

bool RewriteAssignToSwizzledTraverser::rewrite(TCompiler *compiler, TIntermBlock *root)

    RewriteAssignToSwizzledTraverser rewrite;

do

        rewrite.nextIteration();

        root->traverse(&rewrite);

        if (!rewrite.updateTree(compiler, root))

            return false;

    } while (rewrite.didRewrite());

    return true;

RewriteAssignToSwizzledTraverser::RewriteAssignToSwizzledTraverser()

    : TIntermTraverser(true, false, false), mDidRewrite(false)

{}

void RewriteAssignToSwizzledTraverser::nextIteration()

    mDidRewrite = false;

bool RewriteAssignToSwizzledTraverser::visitBinary(Visit, TIntermBinary *node)

    TIntermBinary *rightBinary = node->getRight()->getAsBinaryNode();

    TIntermBlock *parentBlock  = getParentNode()->getAsBlock();

    if (parentBlock && node->isAssignment() && node->getLeft()->getAsSwizzleNode() && rightBinary &&

        rightBinary->isAssignment())

        TIntermSequence replacements;

        replacements.push_back(rightBinary);

        TIntermTyped *rightAssignmentTargetCopy = rightBinary->getLeft()->deepCopy();

        TIntermBinary *lastAssign =

            new TIntermBinary(EOpAssign, node->getLeft(), rightAssignmentTargetCopy);

        replacements.push_back(lastAssign);

        mMultiReplacements.emplace_back(parentBlock, node, std::move(replacements));

        mDidRewrite = true;

        return false;

    return true;

}  // anonymous namespace

bool RewriteRepeatedAssignToSwizzled(TCompiler *compiler, TIntermBlock *root)

    return RewriteAssignToSwizzledTraverser::rewrite(compiler, root);

}  // namespace sh