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//
// Copyright 2017 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.
//
// RunAtTheEndOfShader.cpp: Add code to be run at the end of the shader. In case main() contains a
// return statement, this is done by replacing the main() function with another function that calls
// the old main, like this:
//
// void main() { body }
// =>
// void main0() { body }
// void main()
// {
// main0();
// codeToRun
// }
//
// This way the code will get run even if the return statement inside main is executed.
//
// This is done if main ends in an unconditional |discard| as well, to help with SPIR-V generation
// that expects no dead-code to be present after branches in a block. To avoid bugs when |discard|
// is wrapped in unconditional blocks, any |discard| in main() is used as a signal to wrap it.
//
#include "compiler/translator/tree_util/RunAtTheEndOfShader.h"
#include "compiler/translator/Compiler.h"
#include "compiler/translator/IntermNode.h"
#include "compiler/translator/StaticType.h"
#include "compiler/translator/SymbolTable.h"
#include "compiler/translator/tree_util/FindMain.h"
#include "compiler/translator/tree_util/IntermNode_util.h"
#include "compiler/translator/tree_util/IntermTraverse.h"
namespace sh
{
namespace
{
constexpr const ImmutableString kMainString("main");
class ContainsReturnOrDiscardTraverser : public TIntermTraverser
{
public:
ContainsReturnOrDiscardTraverser()
: TIntermTraverser(true, false, false), mContainsReturnOrDiscard(false)
{}
bool visitBranch(Visit visit, TIntermBranch *node) override
{
if (node->getFlowOp() == EOpReturn || node->getFlowOp() == EOpKill)
{
mContainsReturnOrDiscard = true;
}
return false;
}
bool containsReturnOrDiscard() { return mContainsReturnOrDiscard; }
private:
bool mContainsReturnOrDiscard;
};
bool ContainsReturnOrDiscard(TIntermNode *node)
{
ContainsReturnOrDiscardTraverser traverser;
node->traverse(&traverser);
return traverser.containsReturnOrDiscard();
}
void WrapMainAndAppend(TIntermBlock *root,
TIntermFunctionDefinition *main,
TIntermNode *codeToRun,
TSymbolTable *symbolTable)
{
// Replace main() with main0() with the same body.
TFunction *oldMain =
new TFunction(symbolTable, kEmptyImmutableString, SymbolType::AngleInternal,
StaticType::GetBasic<EbtVoid, EbpUndefined>(), false);
TIntermFunctionDefinition *oldMainDefinition =
CreateInternalFunctionDefinitionNode(*oldMain, main->getBody());
bool replaced = root->replaceChildNode(main, oldMainDefinition);
ASSERT(replaced);
// void main()
TFunction *newMain = new TFunction(symbolTable, kMainString, SymbolType::UserDefined,
StaticType::GetBasic<EbtVoid, EbpUndefined>(), false);
TIntermFunctionPrototype *newMainProto = new TIntermFunctionPrototype(newMain);
// {
// main0();
// codeToRun
// }
TIntermBlock *newMainBody = new TIntermBlock();
TIntermSequence emptySequence;
TIntermAggregate *oldMainCall = TIntermAggregate::CreateFunctionCall(*oldMain, &emptySequence);
newMainBody->appendStatement(oldMainCall);
newMainBody->appendStatement(codeToRun);
// Add the new main() to the root node.
TIntermFunctionDefinition *newMainDefinition =
new TIntermFunctionDefinition(newMainProto, newMainBody);
root->appendStatement(newMainDefinition);
}
} // anonymous namespace
bool RunAtTheEndOfShader(TCompiler *compiler,
TIntermBlock *root,
TIntermNode *codeToRun,
TSymbolTable *symbolTable)
{
TIntermFunctionDefinition *main = FindMain(root);
if (ContainsReturnOrDiscard(main))
{
WrapMainAndAppend(root, main, codeToRun, symbolTable);
}
else
{
main->getBody()->appendStatement(codeToRun);
}
return compiler->validateAST(root);
}
} // namespace sh
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