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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.
//
// SeparateExpressionsReturningArrays splits array-returning expressions that are not array names
// from more complex expressions, assigning them to a temporary variable a#.
// Examples where a, b and c are all arrays:
// (a = b) == (a = c) is split into a = b; type[n] a1 = a; a = c; type[n] a2 = a; a1 == a2;
// type d = type[n](...)[i]; is split into type[n] a1 = type[n](...); type d = a1[i];
#include "compiler/translator/SeparateExpressionsReturningArrays.h"
#include "compiler/translator/IntermNodePatternMatcher.h"
#include "compiler/translator/IntermTraverse.h"
namespace sh
{
namespace
{
// Traverser that separates one array expression into a statement at a time.
class SeparateExpressionsTraverser : public TIntermTraverser
{
public:
SeparateExpressionsTraverser(TSymbolTable *symbolTable);
bool visitBinary(Visit visit, TIntermBinary *node) override;
bool visitAggregate(Visit visit, TIntermAggregate *node) override;
void nextIteration();
bool foundArrayExpression() const { return mFoundArrayExpression; }
protected:
// Marked to true once an operation that needs to be hoisted out of the expression has been
// found. After that, no more AST updates are performed on that traversal.
bool mFoundArrayExpression;
IntermNodePatternMatcher mPatternToSeparateMatcher;
};
SeparateExpressionsTraverser::SeparateExpressionsTraverser(TSymbolTable *symbolTable)
: TIntermTraverser(true, false, false, symbolTable),
mFoundArrayExpression(false),
mPatternToSeparateMatcher(IntermNodePatternMatcher::kExpressionReturningArray)
{
}
// Performs a shallow copy of an assignment node.
// These shallow copies are useful when a node gets inserted into an aggregate node
// and also needs to be replaced in its original location by a different node.
TIntermBinary *CopyAssignmentNode(TIntermBinary *node)
{
return new TIntermBinary(node->getOp(), node->getLeft(), node->getRight());
}
bool SeparateExpressionsTraverser::visitBinary(Visit visit, TIntermBinary *node)
{
if (mFoundArrayExpression)
return false;
// Return if the expression is not an array or if we're not inside a complex expression.
if (!mPatternToSeparateMatcher.match(node, getParentNode()))
return true;
ASSERT(node->getOp() == EOpAssign);
mFoundArrayExpression = true;
TIntermSequence insertions;
insertions.push_back(CopyAssignmentNode(node));
// TODO(oetuaho): In some cases it would be more optimal to not add the temporary node, but just
// use the original target of the assignment. Care must be taken so that this doesn't happen
// when the same array symbol is a target of assignment more than once in one expression.
insertions.push_back(createTempInitDeclaration(node->getLeft()));
insertStatementsInParentBlock(insertions);
queueReplacement(createTempSymbol(node->getType()), OriginalNode::IS_DROPPED);
return false;
}
bool SeparateExpressionsTraverser::visitAggregate(Visit visit, TIntermAggregate *node)
{
if (mFoundArrayExpression)
return false; // No need to traverse further
if (!mPatternToSeparateMatcher.match(node, getParentNode()))
return true;
ASSERT(node->isConstructor() || node->getOp() == EOpCallFunctionInAST);
mFoundArrayExpression = true;
TIntermSequence insertions;
insertions.push_back(createTempInitDeclaration(node->shallowCopy()));
insertStatementsInParentBlock(insertions);
queueReplacement(createTempSymbol(node->getType()), OriginalNode::IS_DROPPED);
return false;
}
void SeparateExpressionsTraverser::nextIteration()
{
mFoundArrayExpression = false;
nextTemporaryId();
}
} // namespace
void SeparateExpressionsReturningArrays(TIntermNode *root, TSymbolTable *symbolTable)
{
SeparateExpressionsTraverser traverser(symbolTable);
// Separate one expression at a time, and reset the traverser between iterations.
do
{
traverser.nextIteration();
root->traverse(&traverser);
if (traverser.foundArrayExpression())
traverser.updateTree();
} while (traverser.foundArrayExpression());
}
} // namespace sh
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