replace nanothread with custom task pool implementation

.gitmodules

@@ -4,6 +4,3 @@
 [submodule "external/metal-cpp"]
 	path = external/metal-cpp
 	url = https://github.com/bkaradzic/metal-cpp.git
-[submodule "external/nanothread"]
-	path = external/nanothread
-	url = https://github.com/skallweitNV/nanothread.git

CMakeLists.txt

@@ -374,12 +374,6 @@ if(APPLE)
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-assume -Wno-switch")
 endif()
 
-# nanothread
-# TODO: disabled for now as it introduces a dependency to libatomic which leads to issues with cross compilation
-# set(NANOTHREAD_STATIC ON)
-# add_subdirectory(external/nanothread)
-# set_target_properties(nanothread PROPERTIES POSITION_INDEPENDENT_CODE ON)
-
 # Setup compiler warnings
 target_compile_options(slang-rhi PRIVATE
     $<$<CXX_COMPILER_ID:MSVC>:
@@ -611,7 +605,6 @@ endif()
 
 target_include_directories(slang-rhi PUBLIC include)
 target_include_directories(slang-rhi PRIVATE src)
-# target_link_libraries(slang-rhi PRIVATE nanothread)
 target_compile_definitions(slang-rhi
     PRIVATE
     SLANG_RHI_ENABLE_CPU=$<BOOL:${SLANG_RHI_ENABLE_CPU}>

README.md

@@ -20,4 +20,3 @@ This library is under active refactoring and development, and is not yet ready f
 - [stb](https://github.com/nothings/stb) (Public Domain)
 - [Vulkan-Headers](https://github.com/KhronosGroup/Vulkan-Headers) (MIT)
 - [OffsetAllocator](https://github.com/sebbbi/OffsetAllocator) (MIT)
-- [nanothread](https://github.com/mitsuba-renderer/nanothread) (BSD 3-Clause)

include/slang-rhi.h

@@ -2552,26 +2552,50 @@ class IDevice : public ISlangUnknown
     convertCooperativeVectorMatrix(const ConvertCooperativeVectorMatrixDesc* descs, uint32_t descCount) = 0;
 };
 
-class ITaskScheduler : public ISlangUnknown
+class ITaskPool : public ISlangUnknown
 {
     SLANG_COM_INTERFACE(0xab272cee, 0xa546, 0x4ae6, {0xbd, 0x0d, 0xcd, 0xab, 0xa9, 0x3f, 0x6d, 0xa6});
 
 public:
     typedef void* TaskHandle;
 
-    /// Submit a task.
-    /// The scheduler needs to call the `run` function with the `payload` argument.
-    /// The `parentTasks` contains a list of tasks that need to be completed before the submitted task can run.
-    /// Every submitted task is released using `releaseTask` once the task handle is no longer used.
-    virtual SLANG_NO_THROW TaskHandle SLANG_MCALL
-    submitTask(TaskHandle* parentTasks, uint32_t parentTaskCount, void (*run)(void* /*payload*/), void* payload) = 0;
+    /// \brief Submit a new task.
+    /// The returned task must be released with `releaseTask()` when no longer needed
+    /// for specifying dependencies or issuing `waitTask()`.
+    /// \param func Function to execute.
+    /// \param payload Payload to pass to the function.
+    /// \param payloadDeleter Optional payload deleter (called when task is destroyed).
+    /// \param deps Parent tasks to wait for.
+    /// \param depsCount Number of parent tasks.
+    /// \return The new task.
+    virtual SLANG_NO_THROW TaskHandle SLANG_MCALL submitTask(
+        void (*func)(void*),
+        void* payload,
+        void (*payloadDeleter)(void*),
+        TaskHandle* deps,
+        size_t depsCount
+    ) = 0;
+
+    /// \brief Get the task payload data.
+    /// \param task Task to get the payload for.
+    /// \return The payload.
+    virtual SLANG_NO_THROW void* SLANG_MCALL getTaskPayload(TaskHandle task) = 0;
 
-    /// Release a task.
-    /// This is called when the task handle is no longer used.
+    /// \brief Release a task.
+    /// \param task Task to release.
     virtual SLANG_NO_THROW void SLANG_MCALL releaseTask(TaskHandle task) = 0;
 
-    // Wait for a task to complete.
-    virtual SLANG_NO_THROW void SLANG_MCALL waitForCompletion(TaskHandle task) = 0;
+    /// \brief Wait for a task to finish.
+    /// \param task Task to wait for.
+    virtual SLANG_NO_THROW void SLANG_MCALL waitTask(TaskHandle task) = 0;
+
+    /// \brief Check if a task is done.
+    /// \param task Task to check.
+    /// \return True if the task is done.
+    virtual SLANG_NO_THROW bool SLANG_MCALL isTaskDone(TaskHandle task) = 0;
+
+    /// \brief Wait for all tasks in the pool to finish.
+    virtual SLANG_NO_THROW void SLANG_MCALL waitAll() = 0;
 };
 
 class IPersistentShaderCache : public ISlangUnknown
@@ -2651,12 +2675,16 @@ class IRHI
 
     /// Set the global task pool worker count.
     /// Must be called before any devices are created.
-    /// This is ignored if the task scheduler is set.
+    /// This only affects the default task pool implementation and has no effect
+    /// if a custom task pool is used with `setTaskPool`.
+    /// If count is set to 0, a blocking task pool implementation is used.
+    /// If count is -1, a threaded task pool is used with a worker count equal to the number of logical cores.
+    /// If count is 1 or larger, a threaded task pool is used with the specified worker count.
     virtual SLANG_NO_THROW Result SLANG_MCALL setTaskPoolWorkerCount(uint32_t count) = 0;
 
-    /// Set the global task scheduler for the RHI.
+    /// Set the global task pool for the RHI.
     /// Must be called before any devices are created.
-    virtual SLANG_NO_THROW Result SLANG_MCALL setTaskScheduler(ITaskScheduler* scheduler) = 0;
+    virtual SLANG_NO_THROW Result SLANG_MCALL setTaskPool(ITaskPool* taskPool) = 0;
 };
 
 // Global public functions