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//
// Copyright (c) 2002-2015 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.
//
// RemovePow is an AST traverser to convert pow(x, y) built-in calls where y is a
// constant to exp2(y * log2(x)). This works around an issue in NVIDIA 311 series
// OpenGL drivers.
//
#include "compiler/translator/RemovePow.h"
#include "compiler/translator/InfoSink.h"
#include "compiler/translator/IntermNode.h"
namespace sh
{
namespace
{
bool IsProblematicPow(TIntermTyped *node)
{
TIntermAggregate *agg = node->getAsAggregate();
if (agg != nullptr && agg->getOp() == EOpPow)
{
ASSERT(agg->getSequence()->size() == 2);
return agg->getSequence()->at(1)->getAsConstantUnion() != nullptr;
}
return false;
}
// Traverser that converts all pow operations simultaneously.
class RemovePowTraverser : public TIntermTraverser
{
public:
RemovePowTraverser();
bool visitAggregate(Visit visit, TIntermAggregate *node) override;
void nextIteration() { mNeedAnotherIteration = false; }
bool needAnotherIteration() const { return mNeedAnotherIteration; }
protected:
bool mNeedAnotherIteration;
};
RemovePowTraverser::RemovePowTraverser()
: TIntermTraverser(true, false, false),
mNeedAnotherIteration(false)
{
}
bool RemovePowTraverser::visitAggregate(Visit visit, TIntermAggregate *node)
{
if (IsProblematicPow(node))
{
TIntermTyped *x = node->getSequence()->at(0)->getAsTyped();
TIntermTyped *y = node->getSequence()->at(1)->getAsTyped();
TIntermUnary *log = new TIntermUnary(EOpLog2, x);
log->setLine(node->getLine());
TOperator op = TIntermBinary::GetMulOpBasedOnOperands(y->getType(), log->getType());
TIntermBinary *mul = new TIntermBinary(op, y, log);
mul->setLine(node->getLine());
TIntermUnary *exp = new TIntermUnary(EOpExp2, mul);
exp->setLine(node->getLine());
queueReplacement(node, exp, OriginalNode::IS_DROPPED);
// If the x parameter also needs to be replaced, we need to do that in another traversal,
// since it's parent node will change in a way that's not handled correctly by updateTree().
if (IsProblematicPow(x))
{
mNeedAnotherIteration = true;
return false;
}
}
return true;
}
} // namespace
void RemovePow(TIntermNode *root)
{
RemovePowTraverser traverser;
// Iterate as necessary, and reset the traverser between iterations.
do
{
traverser.nextIteration();
root->traverse(&traverser);
traverser.updateTree();
}
while (traverser.needAnotherIteration());
}
} // namespace sh
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