SimplifyLoopConditions.cpp

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Author : Olli Etuaho
Date : 2017-08-30 13:03:12
Hash : bb5a7e29
Message : Allow length() on arbitrary array expressions This is required to pass some dEQP GLES 3.1 tests for arrays of arrays, and WebGL conformance tests were also recently fixed to require this behavior. The intent of the GLSL ES spec was not to restrict usage of length(). In practice GL drivers don't implement array length() on expressions with side effects correctly in all cases. HLSL doesn't have an array length operator either. Because of this we always remove array length ops from the AST before output. BUG=angleproject:2142 TEST=angle_unittests, angle_end2end_tests, WebGL conformance tests Change-Id: I863a92e83ac5315b013af9a5626348482bad72b3 Reviewed-on: https://chromium-review.googlesource.com/643190 Commit-Queue: Olli Etuaho <oetuaho@nvidia.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>
src/compiler/translator/SimplifyLoopConditions.cpp
//
// Copyright (c) 2016 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.
//
// SimplifyLoopConditions is an AST traverser that converts loop conditions and loop expressions
// to regular statements inside the loop. This way further transformations that generate statements
// from loop conditions and loop expressions work correctly.
//

#include "compiler/translator/SimplifyLoopConditions.h"

#include "compiler/translator/IntermNodePatternMatcher.h"
#include "compiler/translator/IntermNode_util.h"
#include "compiler/translator/IntermTraverse.h"

namespace sh
{

namespace
{

class SimplifyLoopConditionsTraverser : public TLValueTrackingTraverser
{
  public:
    SimplifyLoopConditionsTraverser(unsigned int conditionsToSimplifyMask,
                                    TSymbolTable *symbolTable,
                                    int shaderVersion);

    void traverseLoop(TIntermLoop *node) override;

    bool visitUnary(Visit visit, TIntermUnary *node) override;
    bool visitBinary(Visit visit, TIntermBinary *node) override;
    bool visitAggregate(Visit visit, TIntermAggregate *node) override;
    bool visitTernary(Visit visit, TIntermTernary *node) override;
    bool visitDeclaration(Visit visit, TIntermDeclaration *node) override;

    bool foundLoopToChange() const { return mFoundLoopToChange; }

  protected:
    // Marked to true once an operation that needs to be hoisted out of a loop expression has been
    // found.
    bool mFoundLoopToChange;
    bool mInsideLoopInitConditionOrExpression;
    IntermNodePatternMatcher mConditionsToSimplify;
};

SimplifyLoopConditionsTraverser::SimplifyLoopConditionsTraverser(
    unsigned int conditionsToSimplifyMask,
    TSymbolTable *symbolTable,
    int shaderVersion)
    : TLValueTrackingTraverser(true, false, false, symbolTable, shaderVersion),
      mFoundLoopToChange(false),
      mInsideLoopInitConditionOrExpression(false),
      mConditionsToSimplify(conditionsToSimplifyMask)
{
}

// If we're inside a loop initialization, condition, or expression, we check for expressions that
// should be moved out of the loop condition or expression. If one is found, the loop is
// transformed.
// If we're not inside loop initialization, condition, or expression, we only need to traverse nodes
// that may contain loops.

bool SimplifyLoopConditionsTraverser::visitUnary(Visit visit, TIntermUnary *node)
{
    if (!mInsideLoopInitConditionOrExpression)
        return false;

    if (mFoundLoopToChange)
        return false;  // Already decided to change this loop.

    mFoundLoopToChange = mConditionsToSimplify.match(node);
    return !mFoundLoopToChange;
}

bool SimplifyLoopConditionsTraverser::visitBinary(Visit visit, TIntermBinary *node)
{
    if (!mInsideLoopInitConditionOrExpression)
        return false;

    if (mFoundLoopToChange)
        return false;  // Already decided to change this loop.

    mFoundLoopToChange = mConditionsToSimplify.match(node, getParentNode(), isLValueRequiredHere());
    return !mFoundLoopToChange;
}

bool SimplifyLoopConditionsTraverser::visitAggregate(Visit visit, TIntermAggregate *node)
{
    if (!mInsideLoopInitConditionOrExpression)
        return false;

    if (mFoundLoopToChange)
        return false;  // Already decided to change this loop.

    mFoundLoopToChange = mConditionsToSimplify.match(node, getParentNode());
    return !mFoundLoopToChange;
}

bool SimplifyLoopConditionsTraverser::visitTernary(Visit visit, TIntermTernary *node)
{
    if (!mInsideLoopInitConditionOrExpression)
        return false;

    if (mFoundLoopToChange)
        return false;  // Already decided to change this loop.

    mFoundLoopToChange = mConditionsToSimplify.match(node);
    return !mFoundLoopToChange;
}

bool SimplifyLoopConditionsTraverser::visitDeclaration(Visit visit, TIntermDeclaration *node)
{
    if (!mInsideLoopInitConditionOrExpression)
        return false;

    if (mFoundLoopToChange)
        return false;  // Already decided to change this loop.

    mFoundLoopToChange = mConditionsToSimplify.match(node);
    return !mFoundLoopToChange;
}

void SimplifyLoopConditionsTraverser::traverseLoop(TIntermLoop *node)
{
    // Mark that we're inside a loop condition or expression, and determine if the loop needs to be
    // transformed.

    ScopedNodeInTraversalPath addToPath(this, node);

    mInsideLoopInitConditionOrExpression = true;
    mFoundLoopToChange                   = false;

    if (!mFoundLoopToChange && node->getInit())
    {
        node->getInit()->traverse(this);
    }

    if (!mFoundLoopToChange && node->getCondition())
    {
        node->getCondition()->traverse(this);
    }

    if (!mFoundLoopToChange && node->getExpression())
    {
        node->getExpression()->traverse(this);
    }

    mInsideLoopInitConditionOrExpression = false;

    if (mFoundLoopToChange)
    {
        nextTemporaryId();

        // Replace the loop condition with a boolean variable that's updated on each iteration.
        TLoopType loopType = node->getType();
        if (loopType == ELoopWhile)
        {
            // Transform:
            //   while (expr) { body; }
            // into
            //   bool s0 = expr;
            //   while (s0) { { body; } s0 = expr; }
            TIntermSequence tempInitSeq;
            tempInitSeq.push_back(createTempInitDeclaration(node->getCondition()->deepCopy()));
            insertStatementsInParentBlock(tempInitSeq);

            TIntermBlock *newBody = new TIntermBlock();
            if (node->getBody())
            {
                newBody->getSequence()->push_back(node->getBody());
            }
            newBody->getSequence()->push_back(
                createTempAssignment(node->getCondition()->deepCopy()));

            // Can't use queueReplacement to replace old body, since it may have been nullptr.
            // It's safe to do the replacements in place here - the new body will still be
            // traversed, but that won't create any problems.
            node->setBody(newBody);
            node->setCondition(createTempSymbol(node->getCondition()->getType()));
        }
        else if (loopType == ELoopDoWhile)
        {
            // Transform:
            //   do {
            //     body;
            //   } while (expr);
            // into
            //   bool s0 = true;
            //   do {
            //     { body; }
            //     s0 = expr;
            //   } while (s0);
            TIntermSequence tempInitSeq;
            tempInitSeq.push_back(createTempInitDeclaration(CreateBoolNode(true)));
            insertStatementsInParentBlock(tempInitSeq);

            TIntermBlock *newBody = new TIntermBlock();
            if (node->getBody())
            {
                newBody->getSequence()->push_back(node->getBody());
            }
            newBody->getSequence()->push_back(
                createTempAssignment(node->getCondition()->deepCopy()));

            // Can't use queueReplacement to replace old body, since it may have been nullptr.
            // It's safe to do the replacements in place here - the new body will still be
            // traversed, but that won't create any problems.
            node->setBody(newBody);
            node->setCondition(createTempSymbol(node->getCondition()->getType()));
        }
        else if (loopType == ELoopFor)
        {
            // Move the loop condition inside the loop.
            // Transform:
            //   for (init; expr; exprB) { body; }
            // into
            //   {
            //     init;
            //     bool s0 = expr;
            //     while (s0) {
            //       { body; }
            //       exprB;
            //       s0 = expr;
            //     }
            //   }
            TIntermBlock *loopScope            = new TIntermBlock();
            TIntermSequence *loopScopeSequence = loopScope->getSequence();

            // Insert "init;"
            if (node->getInit())
            {
                loopScopeSequence->push_back(node->getInit());
            }

            // Insert "bool s0 = expr;" if applicable, "bool s0 = true;" otherwise
            TIntermTyped *conditionInitializer = nullptr;
            if (node->getCondition())
            {
                conditionInitializer = node->getCondition()->deepCopy();
            }
            else
            {
                conditionInitializer = CreateBoolNode(true);
            }
            loopScopeSequence->push_back(createTempInitDeclaration(conditionInitializer));

            // Insert "{ body; }" in the while loop
            TIntermBlock *whileLoopBody = new TIntermBlock();
            if (node->getBody())
            {
                whileLoopBody->getSequence()->push_back(node->getBody());
            }
            // Insert "exprB;" in the while loop
            if (node->getExpression())
            {
                whileLoopBody->getSequence()->push_back(node->getExpression());
            }
            // Insert "s0 = expr;" in the while loop
            if (node->getCondition())
            {
                whileLoopBody->getSequence()->push_back(
                    createTempAssignment(node->getCondition()->deepCopy()));
            }

            // Create "while(s0) { whileLoopBody }"
            TIntermLoop *whileLoop = new TIntermLoop(
                ELoopWhile, nullptr, createTempSymbol(conditionInitializer->getType()), nullptr,
                whileLoopBody);
            loopScope->getSequence()->push_back(whileLoop);
            queueReplacement(loopScope, OriginalNode::IS_DROPPED);

            // After this the old body node will be traversed and loops inside it may be
            // transformed. This is fine, since the old body node will still be in the AST after the
            // transformation that's queued here, and transforming loops inside it doesn't need to
            // know the exact post-transform path to it.
        }
    }

    mFoundLoopToChange = false;

    // We traverse the body of the loop even if the loop is transformed.
    if (node->getBody())
        node->getBody()->traverse(this);
}

}  // namespace

void SimplifyLoopConditions(TIntermNode *root,
                            unsigned int conditionsToSimplifyMask,
                            TSymbolTable *symbolTable,
                            int shaderVersion)
{
    SimplifyLoopConditionsTraverser traverser(conditionsToSimplifyMask, symbolTable, shaderVersion);
    root->traverse(&traverser);
    traverser.updateTree();
}

}  // namespace sh
kc3-lang/angle/src/compiler/translator/SimplifyLoopConditions.cpp

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kc3-lang/angle /src/compiler/translator/SimplifyLoopConditions.cpp
