Method EliminateDeadCode

Source/SpireCore/VariantIR.cpp:10–103

	namespace Compiler
	{
		void ShaderIR::EliminateDeadCode()
		{
			// mark entry points
			auto MarkUsing = [&](String compName, String userWorld)
			{
				if (auto defs = DefinitionsByComponent.TryGetValue(compName))
				{
					if (auto def = defs->TryGetValue(userWorld))
						(*def)->IsEntryPoint = true;
					else
					{
						for (auto & world : Shader->Pipeline->WorldDependency[userWorld]())
						{
							if (auto def2 = defs->TryGetValue(world))
							{
								(*def2)->IsEntryPoint = true;
								break;
							}
						}
					}
				}
			};
			for (auto & impOp : Shader->Pipeline->SyntaxNode->GetImportOperators())
				for (auto & ref : impOp->Usings)
					MarkUsing(ref, impOp->DestWorld.Content);
			for (auto & req : Shader->Pipeline->Components)
				if (req.Value->IsRequire())
				{
					for (auto & impl : req.Value->Implementations)
					{
						if (impl->Worlds.Count())
						{
							for (auto & world : impl->Worlds)
								MarkUsing(req.Key, world);
						}
						else
						{
							for (auto & world : Shader->Pipeline->Worlds)
								MarkUsing(req.Key, world.Key);
						}
					}
				}
			for (auto & def : Definitions)
				if (def->SyntaxNode->HasSimpleAttribute("FragDepth"))
					def->IsEntryPoint = true;
			List<ComponentDefinitionIR*> workList;
			HashSet<ComponentDefinitionIR*> referencedDefs;
			for (auto & def : Definitions)
			{
				if (def->IsEntryPoint)
				{
					if (referencedDefs.Add(def.Ptr()))
						workList.Add(def.Ptr());
				}
			}
			for (int i = 0; i < workList.Count(); i++)
			{
				auto def = workList[i];