kc3-lang/angle/src/compiler/translator/tree_util/RunAtTheEndOfShader.cpp

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• Hash : 16771259
  Author :
  Date : 2025-09-12T11:10:18
  

  Update main() prototype in shader if main() has been replaced.
  
  If the main() function definition has been wrapped/replaced in a shader
  and a main() function prototype is also present, the prototype needs to
  be replaced. Otherwise it will continue to reference the replaced
  main() which can cause issues with shader translation steps.
  
  Bug: angleproject:444653099
  Change-Id: Ie6ce85cac89e026876a1b6e25cd294f1d8a536c4
  Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/6944807
  Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
  Reviewed-by: Kimmo Kinnunen <kkinnunen@apple.com>
  

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• src/compiler/translator/tree_util/RunAtTheEndOfShader.cpp

• //
  // 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);
  
      // If a function prototype of main() also exists, it will need to be replaced. Otherwise it will
      // continue to internally reference the TFunction of the replaced 'main' function definition.
      TIntermFunctionPrototype *oldMainProto = FindMainPrototype(root);
      if (oldMainProto)
      {
          // Replace the prototype node but initialize it with the newMain TFunction; now this newly
          // created main() prototype will reference the new TFunction of newMain.
          newMainProto = new TIntermFunctionPrototype(newMain);
          replaced     = root->replaceChildNode(oldMainProto, newMainProto);
      }
  }
  
  }  // 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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