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//
// 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.
//
// Implementation of the integer pow expressions HLSL bug workaround.
// See header for more info.
#include "compiler/translator/ExpandIntegerPowExpressions.h"
#include <cmath>
#include <cstdlib>
#include "compiler/translator/IntermTraverse.h"
namespace sh
{
namespace
{
class Traverser : public TIntermTraverser
{
public:
static void Apply(TIntermNode *root, TSymbolTable *symbolTable);
private:
Traverser(TSymbolTable *symbolTable);
bool visitAggregate(Visit visit, TIntermAggregate *node) override;
void nextIteration();
bool mFound = false;
};
// static
void Traverser::Apply(TIntermNode *root, TSymbolTable *symbolTable)
{
Traverser traverser(symbolTable);
do
{
traverser.nextIteration();
root->traverse(&traverser);
if (traverser.mFound)
{
traverser.updateTree();
}
} while (traverser.mFound);
}
Traverser::Traverser(TSymbolTable *symbolTable) : TIntermTraverser(true, false, false, symbolTable)
{
}
void Traverser::nextIteration()
{
mFound = false;
nextTemporaryId();
}
bool Traverser::visitAggregate(Visit visit, TIntermAggregate *node)
{
if (mFound)
{
return false;
}
// Test 0: skip non-pow operators.
if (node->getOp() != EOpPow)
{
return true;
}
const TIntermSequence *sequence = node->getSequence();
ASSERT(sequence->size() == 2u);
const TIntermConstantUnion *constantNode = sequence->at(1)->getAsConstantUnion();
// Test 1: check for a single constant.
if (!constantNode || constantNode->getNominalSize() != 1)
{
return true;
}
const TConstantUnion *constant = constantNode->getUnionArrayPointer();
TConstantUnion asFloat;
asFloat.cast(EbtFloat, *constant);
float value = asFloat.getFConst();
// Test 2: value is in the problematic range.
if (value < -5.0f || value > 9.0f)
{
return true;
}
// Test 3: value is integer or pretty close to an integer.
float absval = std::abs(value);
float frac = absval - std::round(absval);
if (frac > 0.0001f)
{
return true;
}
// Test 4: skip -1, 0, and 1
int exponent = static_cast<int>(value);
int n = std::abs(exponent);
if (n < 2)
{
return true;
}
// Potential problem case detected, apply workaround.
nextTemporaryId();
TIntermTyped *lhs = sequence->at(0)->getAsTyped();
ASSERT(lhs);
TIntermDeclaration *init = createTempInitDeclaration(lhs);
TIntermTyped *current = createTempSymbol(lhs->getType());
insertStatementInParentBlock(init);
// Create a chain of n-1 multiples.
for (int i = 1; i < n; ++i)
{
TIntermBinary *mul = new TIntermBinary(EOpMul, current, createTempSymbol(lhs->getType()));
mul->setLine(node->getLine());
current = mul;
}
// For negative pow, compute the reciprocal of the positive pow.
if (exponent < 0)
{
TConstantUnion *oneVal = new TConstantUnion();
oneVal->setFConst(1.0f);
TIntermConstantUnion *oneNode = new TIntermConstantUnion(oneVal, node->getType());
TIntermBinary *div = new TIntermBinary(EOpDiv, oneNode, current);
current = div;
}
queueReplacement(current, OriginalNode::IS_DROPPED);
mFound = true;
return false;
}
} // anonymous namespace
void ExpandIntegerPowExpressions(TIntermNode *root, TSymbolTable *symbolTable)
{
Traverser::Apply(root, symbolTable);
}
} // namespace sh
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