Cycles: Adapt shared kernel/device/gpu layer for MSL

This patch adapts the shared kernel entrypoints so that they can be compiled as MSL (Metal Shading Language). Where possible, the adaptations avoid changes in common code.

In MSL, kernel function inputs are explicitly bound to resources. In the case of argument buffers, we declare a struct containing the kernel arguments, accessible via device pointer. This differs from CUDA and HIP where kernel function arguments are declared as traditional C-style function parameters. This patch adapts the entrypoints declared in kernel.h so that they can be translated via a new `ccl_gpu_kernel_signature` macro into the required parameter struct + kernel entrypoint pairing for MSL.

MSL buffer attribution must be applied to function parameters or non-static class data members. To allow universal access to the integrator state, kernel data, and texture fetch adapters, we wrap all of the shared kernel code in a `MetalKernelContext` class. This is achieved by bracketing the appropriate kernel headers with "context_begin.h" and "context_end.h" on Metal. When calling deeper into the kernel code, we must reference the context class (e.g. `context.integrator_init_from_camera`). This extra prefixing is performed by a set of defines in "context_end.h". These will require explicit maintenance if entrypoints change. We invite discussion on more maintainable ways to enforce correctness.

Lambda expressions are not supported on MSL, so a new `ccl_gpu_kernel_lambda` macro generates an inline function object and optionally capturing any required state. This yields the same behaviour. This approach is applied to all parallel_... implementations which are templated by operation. The lambda expressions in the film_convert... kernels don't adapt cleanly to use function objects. However, these entrypoints can be macro-generated more concisely to avoid lambda expressions entirely, instead relying on constant folding to handle the pixel/channel conversions.

A separate implementation of `gpu_parallel_active_index_array` is provided for Metal to workaround some subtle differences in SIMD width, and also to encapsulate some required thread parameters which must be declared as explicit entrypoint function parameters.

Ref T92212

Reviewed By: brecht

Maniphest Tasks: T92212

Differential Revision: https://developer.blender.org/D13109

16 files changed, 877 insertions, 482 deletions

diff --git a/intern/cycles/kernel/CMakeLists.txt b/intern/cycles/kernel/CMakeLists.txt
index 29ff69df864..f311b0e74bb 100644
--- a/intern/cycles/kernel/CMakeLists.txt
+++ b/intern/cycles/kernel/CMakeLists.txt
@@ -39,6 +39,10 @@ set(SRC_KERNEL_DEVICE_HIP
   device/hip/kernel.cpp
 )
 
+set(SRC_KERNEL_DEVICE_METAL
+  device/metal/kernel.metal
+)
+
 set(SRC_KERNEL_DEVICE_OPTIX
   device/optix/kernel.cu
   device/optix/kernel_shader_raytrace.cu
@@ -79,6 +83,13 @@ set(SRC_KERNEL_DEVICE_OPTIX_HEADERS
   device/optix/globals.h
 )
 
+set(SRC_KERNEL_DEVICE_METAL_HEADERS
+  device/metal/compat.h
+  device/metal/context_begin.h
+  device/metal/context_end.h
+  device/metal/globals.h
+)
+
 set(SRC_KERNEL_CLOSURE_HEADERS
   closure/alloc.h
   closure/bsdf.h
@@ -368,6 +379,7 @@ if(WITH_CYCLES_CUDA_BINARIES)
     ${SRC_KERNEL_HEADERS}
     ${SRC_KERNEL_DEVICE_GPU_HEADERS}
     ${SRC_KERNEL_DEVICE_CUDA_HEADERS}
+    ${SRC_KERNEL_DEVICE_METAL_HEADERS}
     ${SRC_UTIL_HEADERS}
   )
   set(cuda_cubins)
@@ -723,12 +735,14 @@ cycles_add_library(cycles_kernel "${LIB}"
   ${SRC_KERNEL_DEVICE_CUDA}
   ${SRC_KERNEL_DEVICE_HIP}
   ${SRC_KERNEL_DEVICE_OPTIX}
+  ${SRC_KERNEL_DEVICE_METAL}
   ${SRC_KERNEL_HEADERS}
   ${SRC_KERNEL_DEVICE_CPU_HEADERS}
   ${SRC_KERNEL_DEVICE_GPU_HEADERS}
   ${SRC_KERNEL_DEVICE_CUDA_HEADERS}
   ${SRC_KERNEL_DEVICE_HIP_HEADERS}
   ${SRC_KERNEL_DEVICE_OPTIX_HEADERS}
+  ${SRC_KERNEL_DEVICE_METAL_HEADERS}
 )
 
 source_group("bake" FILES ${SRC_KERNEL_BAKE_HEADERS})
@@ -740,6 +754,7 @@ source_group("device\\cuda" FILES ${SRC_KERNEL_DEVICE_CUDA} ${SRC_KERNEL_DEVICE_
 source_group("device\\gpu" FILES ${SRC_KERNEL_DEVICE_GPU_HEADERS})
 source_group("device\\hip" FILES ${SRC_KERNEL_DEVICE_HIP} ${SRC_KERNEL_DEVICE_HIP_HEADERS})
 source_group("device\\optix" FILES ${SRC_KERNEL_DEVICE_OPTIX} ${SRC_KERNEL_DEVICE_OPTIX_HEADERS})
+source_group("device\\metal" FILES ${SRC_KERNEL_DEVICE_METAL} ${SRC_KERNEL_DEVICE_METAL_HEADERS})
 source_group("film" FILES ${SRC_KERNEL_FILM_HEADERS})
 source_group("geom" FILES ${SRC_KERNEL_GEOM_HEADERS})
 source_group("integrator" FILES ${SRC_KERNEL_INTEGRATOR_HEADERS})
@@ -772,6 +787,8 @@ delayed_install(${CMAKE_CURRENT_SOURCE_DIR} "${SRC_KERNEL_DEVICE_HIP}" ${CYCLES_
 delayed_install(${CMAKE_CURRENT_SOURCE_DIR} "${SRC_KERNEL_DEVICE_HIP_HEADERS}" ${CYCLES_INSTALL_PATH}/source/kernel/device/hip)
 delayed_install(${CMAKE_CURRENT_SOURCE_DIR} "${SRC_KERNEL_DEVICE_OPTIX}" ${CYCLES_INSTALL_PATH}/source/kernel/device/optix)
 delayed_install(${CMAKE_CURRENT_SOURCE_DIR} "${SRC_KERNEL_DEVICE_OPTIX_HEADERS}" ${CYCLES_INSTALL_PATH}/source/kernel/device/optix)
+delayed_install(${CMAKE_CURRENT_SOURCE_DIR} "${SRC_KERNEL_DEVICE_METAL}" ${CYCLES_INSTALL_PATH}/source/kernel/device/metal)
+delayed_install(${CMAKE_CURRENT_SOURCE_DIR} "${SRC_KERNEL_DEVICE_METAL_HEADERS}" ${CYCLES_INSTALL_PATH}/source/kernel/device/metal)
 delayed_install(${CMAKE_CURRENT_SOURCE_DIR} "${SRC_KERNEL_FILM_HEADERS}" ${CYCLES_INSTALL_PATH}/source/kernel/film)
 delayed_install(${CMAKE_CURRENT_SOURCE_DIR} "${SRC_KERNEL_GEOM_HEADERS}" ${CYCLES_INSTALL_PATH}/source/kernel/geom)
 delayed_install(${CMAKE_CURRENT_SOURCE_DIR} "${SRC_KERNEL_INTEGRATOR_HEADERS}" ${CYCLES_INSTALL_PATH}/source/kernel/integrator)
diff --git a/intern/cycles/kernel/device/cuda/compat.h b/intern/cycles/kernel/device/cuda/compat.h
index 1ee82e6eb7c..2feebad074f 100644
--- a/intern/cycles/kernel/device/cuda/compat.h
+++ b/intern/cycles/kernel/device/cuda/compat.h
@@ -75,6 +75,7 @@ typedef unsigned long long uint64_t;
 #define ccl_gpu_block_idx_x (blockIdx.x)
 #define ccl_gpu_grid_dim_x (gridDim.x)
 #define ccl_gpu_warp_size (warpSize)
+#define ccl_gpu_thread_mask(thread_warp) uint(0xFFFFFFFF >> (ccl_gpu_warp_size - thread_warp))
 
 #define ccl_gpu_global_id_x() (ccl_gpu_block_idx_x * ccl_gpu_block_dim_x + ccl_gpu_thread_idx_x)
 #define ccl_gpu_global_size_x() (ccl_gpu_grid_dim_x * ccl_gpu_block_dim_x)
diff --git a/intern/cycles/kernel/device/cuda/config.h b/intern/cycles/kernel/device/cuda/config.h
index 46196dcdb51..e333fe90332 100644
--- a/intern/cycles/kernel/device/cuda/config.h
+++ b/intern/cycles/kernel/device/cuda/config.h
@@ -93,11 +93,35 @@
 /* Compute number of threads per block and minimum blocks per multiprocessor
  * given the maximum number of registers per thread. */
 
-#define ccl_gpu_kernel(block_num_threads, thread_num_registers) \
+#define ccl_gpu_kernel_threads(block_num_threads) \
+  extern "C" __global__ void __launch_bounds__(block_num_threads)
+
+#define ccl_gpu_kernel_threads_registers(block_num_threads, thread_num_registers) \
   extern "C" __global__ void __launch_bounds__(block_num_threads, \
                                                GPU_MULTIPRESSOR_MAX_REGISTERS / \
                                                    (block_num_threads * thread_num_registers))
 
+/* allow ccl_gpu_kernel to accept 1 or 2 parameters */
+#define SELECT_MACRO(_1, _2, NAME, ...) NAME
+#define ccl_gpu_kernel(...) \
+  SELECT_MACRO(__VA_ARGS__, ccl_gpu_kernel_threads_registers, ccl_gpu_kernel_threads)(__VA_ARGS__)
+
+#define ccl_gpu_kernel_signature(name, ...) kernel_gpu_##name(__VA_ARGS__)
+
+#define ccl_gpu_kernel_call(x) x
+
+/* define a function object where "func" is the lambda body, and additional parameters are used to
+ * specify captured state  */
+#define ccl_gpu_kernel_lambda(func, ...) \
+  struct KernelLambda { \
+    __VA_ARGS__; \
+    __device__ int operator()(const int state) \
+    { \
+      return (func); \
+    } \
+  } ccl_gpu_kernel_lambda_pass; \
+  ccl_gpu_kernel_lambda_pass
+
 /* sanity checks */
 
 #if GPU_KERNEL_BLOCK_NUM_THREADS > GPU_BLOCK_MAX_THREADS
diff --git a/intern/cycles/kernel/device/gpu/image.h b/intern/cycles/kernel/device/gpu/image.h
index 95a37c693ae..0900a45c83d 100644
--- a/intern/cycles/kernel/device/gpu/image.h
+++ b/intern/cycles/kernel/device/gpu/image.h
@@ -65,7 +65,9 @@ ccl_device float cubic_h1(float a)
 
 /* Fast bicubic texture lookup using 4 bilinear lookups, adapted from CUDA samples. */
 template<typename T>
-ccl_device_noinline T kernel_tex_image_interp_bicubic(const TextureInfo &info, float x, float y)
+ccl_device_noinline T kernel_tex_image_interp_bicubic(ccl_global const TextureInfo &info,
+                                                      float x,
+                                                      float y)
 {
   ccl_gpu_tex_object tex = (ccl_gpu_tex_object)info.data;
 
@@ -94,7 +96,7 @@ ccl_device_noinline T kernel_tex_image_interp_bicubic(const TextureInfo &info, f
 /* Fast tricubic texture lookup using 8 trilinear lookups. */
 template<typename T>
 ccl_device_noinline T
-kernel_tex_image_interp_tricubic(const TextureInfo &info, float x, float y, float z)
+kernel_tex_image_interp_tricubic(ccl_global const TextureInfo &info, float x, float y, float z)
 {
   ccl_gpu_tex_object tex = (ccl_gpu_tex_object)info.data;
 
@@ -169,7 +171,7 @@ ccl_device T kernel_tex_image_interp_tricubic_nanovdb(S &s, float x, float y, fl
 
 template<typename T>
 ccl_device_noinline T kernel_tex_image_interp_nanovdb(
-    const TextureInfo &info, float x, float y, float z, uint interpolation)
+    ccl_global const TextureInfo &info, float x, float y, float z, uint interpolation)
 {
   using namespace nanovdb;
 
@@ -191,7 +193,7 @@ ccl_device_noinline T kernel_tex_image_interp_nanovdb(
 
 ccl_device float4 kernel_tex_image_interp(KernelGlobals kg, int id, float x, float y)
 {
-  const TextureInfo &info = kernel_tex_fetch(__texture_info, id);
+  ccl_global const TextureInfo &info = kernel_tex_fetch(__texture_info, id);
 
   /* float4, byte4, ushort4 and half4 */
   const int texture_type = info.data_type;
@@ -226,7 +228,7 @@ ccl_device float4 kernel_tex_image_interp_3d(KernelGlobals kg,
                                              float3 P,
                                              InterpolationType interp)
 {
-  const TextureInfo &info = kernel_tex_fetch(__texture_info, id);
+  ccl_global const TextureInfo &info = kernel_tex_fetch(__texture_info, id);
 
   if (info.use_transform_3d) {
     P = transform_point(&info.transform_3d, P);
diff --git a/intern/cycles/kernel/device/gpu/kernel.h b/intern/cycles/kernel/device/gpu/kernel.h
index 5848ba5df9d..2ec6a49ec7b 100644
--- a/intern/cycles/kernel/device/gpu/kernel.h
+++ b/intern/cycles/kernel/device/gpu/kernel.h
@@ -21,6 +21,10 @@
 #include "kernel/device/gpu/parallel_sorted_index.h"
 #include "kernel/device/gpu/work_stealing.h"
 
+#ifdef __KERNEL_METAL__
+#  include "kernel/device/metal/context_begin.h"
+#endif
+
 #include "kernel/integrator/state.h"
 #include "kernel/integrator/state_flow.h"
 #include "kernel/integrator/state_util.h"
@@ -40,6 +44,11 @@
 #include "kernel/bake/bake.h"
 
 #include "kernel/film/adaptive_sampling.h"
+
+#ifdef __KERNEL_METAL__
+#  include "kernel/device/metal/context_end.h"
+#endif
+
 #include "kernel/film/read.h"
 
 /* --------------------------------------------------------------------
@@ -47,7 +56,8 @@
  */
 
 ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
-    kernel_gpu_integrator_reset(int num_states)
+ccl_gpu_kernel_signature(integrator_reset,
+                          int num_states)
 {
   const int state = ccl_gpu_global_id_x();
 
@@ -58,10 +68,11 @@ ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
 }
 
 ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
-    kernel_gpu_integrator_init_from_camera(KernelWorkTile *tiles,
-                                           const int num_tiles,
-                                           float *render_buffer,
-                                           const int max_tile_work_size)
+    ccl_gpu_kernel_signature(integrator_init_from_camera,
+                             ccl_global KernelWorkTile *tiles,
+                             const int num_tiles,
+                             ccl_global float *render_buffer,
+                             const int max_tile_work_size)
 {
   const int work_index = ccl_gpu_global_id_x();
 
@@ -72,7 +83,7 @@ ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
   const int tile_index = work_index / max_tile_work_size;
   const int tile_work_index = work_index - tile_index * max_tile_work_size;
 
-  const KernelWorkTile *tile = &tiles[tile_index];
+  ccl_global const KernelWorkTile *tile = &tiles[tile_index];
 
   if (tile_work_index >= tile->work_size) {
     return;
@@ -83,14 +94,16 @@ ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
   uint x, y, sample;
   get_work_pixel(tile, tile_work_index, &x, &y, &sample);
 
-  integrator_init_from_camera(nullptr, state, tile, render_buffer, x, y, sample);
+  ccl_gpu_kernel_call(
+      integrator_init_from_camera(nullptr, state, tile, render_buffer, x, y, sample));
 }
 
 ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
-    kernel_gpu_integrator_init_from_bake(KernelWorkTile *tiles,
-                                         const int num_tiles,
-                                         float *render_buffer,
-                                         const int max_tile_work_size)
+    ccl_gpu_kernel_signature(integrator_init_from_bake,
+                             ccl_global KernelWorkTile *tiles,
+                             const int num_tiles,
+                             ccl_global float *render_buffer,
+                             const int max_tile_work_size)
 {
   const int work_index = ccl_gpu_global_id_x();
 
@@ -101,7 +114,7 @@ ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
   const int tile_index = work_index / max_tile_work_size;
   const int tile_work_index = work_index - tile_index * max_tile_work_size;
 
-  const KernelWorkTile *tile = &tiles[tile_index];
+  ccl_global const KernelWorkTile *tile = &tiles[tile_index];
 
   if (tile_work_index >= tile->work_size) {
     return;
@@ -112,228 +125,260 @@ ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
   uint x, y, sample;
   get_work_pixel(tile, tile_work_index, &x, &y, &sample);
 
-  integrator_init_from_bake(nullptr, state, tile, render_buffer, x, y, sample);
+  ccl_gpu_kernel_call(
+      integrator_init_from_bake(nullptr, state, tile, render_buffer, x, y, sample));
 }
 
 ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
-    kernel_gpu_integrator_intersect_closest(const int *path_index_array, const int work_size)
+    ccl_gpu_kernel_signature(integrator_intersect_closest,
+                             ccl_global const int *path_index_array,
+                             const int work_size)
 {
   const int global_index = ccl_gpu_global_id_x();
 
   if (global_index < work_size) {
     const int state = (path_index_array) ? path_index_array[global_index] : global_index;
-    integrator_intersect_closest(NULL, state);
+    ccl_gpu_kernel_call(integrator_intersect_closest(NULL, state));
   }
 }
 
 ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
-    kernel_gpu_integrator_intersect_shadow(const int *path_index_array, const int work_size)
+    ccl_gpu_kernel_signature(integrator_intersect_shadow,
+                             ccl_global const int *path_index_array,
+                             const int work_size)
 {
   const int global_index = ccl_gpu_global_id_x();
 
   if (global_index < work_size) {
     const int state = (path_index_array) ? path_index_array[global_index] : global_index;
-    integrator_intersect_shadow(NULL, state);
+    ccl_gpu_kernel_call(integrator_intersect_shadow(NULL, state));
   }
 }
 
 ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
-    kernel_gpu_integrator_intersect_subsurface(const int *path_index_array, const int work_size)
+    ccl_gpu_kernel_signature(integrator_intersect_subsurface,
+                             ccl_global const int *path_index_array,
+                             const int work_size)
 {
   const int global_index = ccl_gpu_global_id_x();
 
   if (global_index < work_size) {
     const int state = (path_index_array) ? path_index_array[global_index] : global_index;
-    integrator_intersect_subsurface(NULL, state);
+    ccl_gpu_kernel_call(integrator_intersect_subsurface(NULL, state));
   }
 }
 
 ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
-    kernel_gpu_integrator_intersect_volume_stack(const int *path_index_array, const int work_size)
+    ccl_gpu_kernel_signature(integrator_intersect_volume_stack,
+                             ccl_global const int *path_index_array,
+                             const int work_size)
 {
   const int global_index = ccl_gpu_global_id_x();
 
   if (global_index < work_size) {
     const int state = (path_index_array) ? path_index_array[global_index] : global_index;
-    integrator_intersect_volume_stack(NULL, state);
+    ccl_gpu_kernel_call(integrator_intersect_volume_stack(NULL, state));
   }
 }
 
 ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
-    kernel_gpu_integrator_shade_background(const int *path_index_array,
-                                           float *render_buffer,
-                                           const int work_size)
+    ccl_gpu_kernel_signature(integrator_shade_background,
+                             ccl_global const int *path_index_array,
+                             ccl_global float *render_buffer,
+                             const int work_size)
 {
   const int global_index = ccl_gpu_global_id_x();
 
   if (global_index < work_size) {
     const int state = (path_index_array) ? path_index_array[global_index] : global_index;
-    integrator_shade_background(NULL, state, render_buffer);
+    ccl_gpu_kernel_call(integrator_shade_background(NULL, state, render_buffer));
   }
 }
 
 ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
-    kernel_gpu_integrator_shade_light(const int *path_index_array,
-                                      float *render_buffer,
-                                      const int work_size)
+    ccl_gpu_kernel_signature(integrator_shade_light,
+                             ccl_global const int *path_index_array,
+                             ccl_global float *render_buffer,
+                             const int work_size)
 {
   const int global_index = ccl_gpu_global_id_x();
 
   if (global_index < work_size) {
     const int state = (path_index_array) ? path_index_array[global_index] : global_index;
-    integrator_shade_light(NULL, state, render_buffer);
+    ccl_gpu_kernel_call(integrator_shade_light(NULL, state, render_buffer));
   }
 }
 
 ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
-    kernel_gpu_integrator_shade_shadow(const int *path_index_array,
-                                       float *render_buffer,
-                                       const int work_size)
+    ccl_gpu_kernel_signature(integrator_shade_shadow,
+                             ccl_global const int *path_index_array,
+                             ccl_global float *render_buffer,
+                             const int work_size)
 {
   const int global_index = ccl_gpu_global_id_x();
 
   if (global_index < work_size) {
     const int state = (path_index_array) ? path_index_array[global_index] : global_index;
-    integrator_shade_shadow(NULL, state, render_buffer);
+    ccl_gpu_kernel_call(integrator_shade_shadow(NULL, state, render_buffer));
   }
 }
 
 ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
-    kernel_gpu_integrator_shade_surface(const int *path_index_array,
-                                        float *render_buffer,
-                                        const int work_size)
+    ccl_gpu_kernel_signature(integrator_shade_surface,
+                             ccl_global const int *path_index_array,
+                             ccl_global float *render_buffer,
+                             const int work_size)
 {
   const int global_index = ccl_gpu_global_id_x();
 
   if (global_index < work_size) {
     const int state = (path_index_array) ? path_index_array[global_index] : global_index;
-    integrator_shade_surface(NULL, state, render_buffer);
+    ccl_gpu_kernel_call(integrator_shade_surface(NULL, state, render_buffer));
   }
 }
 
 ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
-    kernel_gpu_integrator_shade_surface_raytrace(const int *path_index_array,
-                                                 float *render_buffer,
-                                                 const int work_size)
+    ccl_gpu_kernel_signature(integrator_shade_surface_raytrace,
+                             ccl_global const int *path_index_array,
+                             ccl_global float *render_buffer,
+                             const int work_size)
 {
   const int global_index = ccl_gpu_global_id_x();
 
   if (global_index < work_size) {
     const int state = (path_index_array) ? path_index_array[global_index] : global_index;
-    integrator_shade_surface_raytrace(NULL, state, render_buffer);
+    ccl_gpu_kernel_call(integrator_shade_surface_raytrace(NULL, state, render_buffer));
   }
 }
 
 ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
-    kernel_gpu_integrator_shade_volume(const int *path_index_array,
-                                       float *render_buffer,
-                                       const int work_size)
+    ccl_gpu_kernel_signature(integrator_shade_volume,
+                             ccl_global const int *path_index_array,
+                             ccl_global float *render_buffer,
+                             const int work_size)
 {
   const int global_index = ccl_gpu_global_id_x();
 
   if (global_index < work_size) {
     const int state = (path_index_array) ? path_index_array[global_index] : global_index;
-    integrator_shade_volume(NULL, state, render_buffer);
+    ccl_gpu_kernel_call(integrator_shade_volume(NULL, state, render_buffer));
   }
 }
 
-extern "C" __global__ void __launch_bounds__(GPU_PARALLEL_ACTIVE_INDEX_DEFAULT_BLOCK_SIZE)
-    kernel_gpu_integrator_queued_paths_array(int num_states,
-                                             int *indices,
-                                             int *num_indices,
-                                             int kernel)
+ccl_gpu_kernel(GPU_PARALLEL_ACTIVE_INDEX_DEFAULT_BLOCK_SIZE)
+    ccl_gpu_kernel_signature(integrator_queued_paths_array,
+                             int num_states,
+                             ccl_global int *indices,
+                             ccl_global int *num_indices,
+                             int kernel_index)
 {
-  gpu_parallel_active_index_array<GPU_PARALLEL_ACTIVE_INDEX_DEFAULT_BLOCK_SIZE>(
-      num_states, indices, num_indices, [kernel](const int state) {
-        return (INTEGRATOR_STATE(state, path, queued_kernel) == kernel);
-      });
-}
+  ccl_gpu_kernel_lambda(INTEGRATOR_STATE(state, path, queued_kernel) == kernel_index,
+                        int kernel_index)
+      .kernel_index = kernel_index;
 
-extern "C" __global__ void __launch_bounds__(GPU_PARALLEL_ACTIVE_INDEX_DEFAULT_BLOCK_SIZE)
-    kernel_gpu_integrator_queued_shadow_paths_array(int num_states,
-                                                    int *indices,
-                                                    int *num_indices,
-                                                    int kernel)
-{
   gpu_parallel_active_index_array<GPU_PARALLEL_ACTIVE_INDEX_DEFAULT_BLOCK_SIZE>(
-      num_states, indices, num_indices, [kernel](const int state) {
-        return (INTEGRATOR_STATE(state, shadow_path, queued_kernel) == kernel);
-      });
+      num_states, indices, num_indices, ccl_gpu_kernel_lambda_pass);
 }
 
-extern "C" __global__ void __launch_bounds__(GPU_PARALLEL_ACTIVE_INDEX_DEFAULT_BLOCK_SIZE)
-    kernel_gpu_integrator_active_paths_array(int num_states, int *indices, int *num_indices)
+ccl_gpu_kernel(GPU_PARALLEL_ACTIVE_INDEX_DEFAULT_BLOCK_SIZE)
+    ccl_gpu_kernel_signature(integrator_queued_shadow_paths_array,
+                             int num_states,
+                             ccl_global int *indices,
+                             ccl_global int *num_indices,
+                             int kernel_index)
 {
+  ccl_gpu_kernel_lambda(INTEGRATOR_STATE(state, shadow_path, queued_kernel) == kernel_index,
+                        int kernel_index)
+      .kernel_index = kernel_index;
+
   gpu_parallel_active_index_array<GPU_PARALLEL_ACTIVE_INDEX_DEFAULT_BLOCK_SIZE>(
-      num_states, indices, num_indices, [](const int state) {
-        return (INTEGRATOR_STATE(state, path, queued_kernel) != 0);
-      });
+      num_states, indices, num_indices, ccl_gpu_kernel_lambda_pass);
 }
 
-extern "C" __global__ void __launch_bounds__(GPU_PARALLEL_ACTIVE_INDEX_DEFAULT_BLOCK_SIZE)
-    kernel_gpu_integrator_terminated_paths_array(int num_states,
-                                                 int *indices,
-                                                 int *num_indices,
-                                                 int indices_offset)
+ccl_gpu_kernel(GPU_PARALLEL_ACTIVE_INDEX_DEFAULT_BLOCK_SIZE)
+    ccl_gpu_kernel_signature(integrator_active_paths_array,
+                             int num_states,
+                             ccl_global int *indices,
+                             ccl_global int *num_indices)
 {
+  ccl_gpu_kernel_lambda(INTEGRATOR_STATE(state, path, queued_kernel) != 0);
   gpu_parallel_active_index_array<GPU_PARALLEL_ACTIVE_INDEX_DEFAULT_BLOCK_SIZE>(
-      num_states, indices + indices_offset, num_indices, [](const int state) {
-        return (INTEGRATOR_STATE(state, path, queued_kernel) == 0);
-      });
+      num_states, indices, num_indices, ccl_gpu_kernel_lambda_pass);
 }
 
-extern "C" __global__ void __launch_bounds__(GPU_PARALLEL_ACTIVE_INDEX_DEFAULT_BLOCK_SIZE)
-    kernel_gpu_integrator_terminated_shadow_paths_array(int num_states,
-                                                        int *indices,
-                                                        int *num_indices,
-                                                        int indices_offset)
+ccl_gpu_kernel(GPU_PARALLEL_ACTIVE_INDEX_DEFAULT_BLOCK_SIZE)
+    ccl_gpu_kernel_signature(integrator_terminated_paths_array,
+                             int num_states,
+                             ccl_global int *indices,
+                             ccl_global int *num_indices,
+                             int indices_offset)
 {
+  ccl_gpu_kernel_lambda(INTEGRATOR_STATE(state, path, queued_kernel) == 0);
   gpu_parallel_active_index_array<GPU_PARALLEL_ACTIVE_INDEX_DEFAULT_BLOCK_SIZE>(
-      num_states, indices + indices_offset, num_indices, [](const int state) {
-        return (INTEGRATOR_STATE(state, shadow_path, queued_kernel) == 0);
-      });
+      num_states, indices + indices_offset, num_indices, ccl_gpu_kernel_lambda_pass);
 }
 
-extern "C" __global__ void __launch_bounds__(GPU_PARALLEL_SORTED_INDEX_DEFAULT_BLOCK_SIZE)
-    kernel_gpu_integrator_sorted_paths_array(int num_states,
-                                             int num_states_limit,
-                                             int *indices,
-                                             int *num_indices,
-                                             int *key_counter,
-                                             int *key_prefix_sum,
-                                             int kernel)
+ccl_gpu_kernel(GPU_PARALLEL_ACTIVE_INDEX_DEFAULT_BLOCK_SIZE)
+    ccl_gpu_kernel_signature(integrator_terminated_shadow_paths_array,
+                             int num_states,
+                             ccl_global int *indices,
+                             ccl_global int *num_indices,
+                             int indices_offset)
 {
-  gpu_parallel_sorted_index_array<GPU_PARALLEL_SORTED_INDEX_DEFAULT_BLOCK_SIZE>(
+  ccl_gpu_kernel_lambda(INTEGRATOR_STATE(state, shadow_path, queued_kernel) == 0);
+  gpu_parallel_active_index_array<GPU_PARALLEL_ACTIVE_INDEX_DEFAULT_BLOCK_SIZE>(
+      num_states, indices + indices_offset, num_indices, ccl_gpu_kernel_lambda_pass);
+}
+
+ccl_gpu_kernel(GPU_PARALLEL_SORTED_INDEX_DEFAULT_BLOCK_SIZE)
+    ccl_gpu_kernel_signature(integrator_sorted_paths_array,
+                             int num_states,
+                             int num_states_limit,
+                             ccl_global int *indices,
+                             ccl_global int *num_indices,
+                             ccl_global int *key_counter,
+                             ccl_global int *key_prefix_sum,
+                             int kernel_index)
+{
+  ccl_gpu_kernel_lambda((INTEGRATOR_STATE(state, path, queued_kernel) == kernel_index) ?
+                            INTEGRATOR_STATE(state, path, shader_sort_key) :
+                            GPU_PARALLEL_SORTED_INDEX_INACTIVE_KEY,
+                        int kernel_index)
+    .kernel_index = kernel_index;
+  
+  const uint state_index = ccl_gpu_global_id_x();
+  gpu_parallel_sorted_index_array(
+      state_index,
       num_states,
       num_states_limit,
       indices,
-      num_indices,
-      key_counter,
-      key_prefix_sum,
-      [kernel](const int state) {
-        return (INTEGRATOR_STATE(state, path, queued_kernel) == kernel) ?
-                   INTEGRATOR_STATE(state, path, shader_sort_key) :
-                   GPU_PARALLEL_SORTED_INDEX_INACTIVE_KEY;
-      });
-}
-
-extern "C" __global__ void __launch_bounds__(GPU_PARALLEL_ACTIVE_INDEX_DEFAULT_BLOCK_SIZE)
-    kernel_gpu_integrator_compact_paths_array(int num_states,
-                                              int *indices,
-                                              int *num_indices,
-                                              int num_active_paths)
-{
+                                  num_indices,
+                                  key_counter,
+                                  key_prefix_sum,
+                                  ccl_gpu_kernel_lambda_pass);
+}
+
+ccl_gpu_kernel(GPU_PARALLEL_ACTIVE_INDEX_DEFAULT_BLOCK_SIZE)
+    ccl_gpu_kernel_signature(integrator_compact_paths_array,
+                             int num_states,
+                             ccl_global int *indices,
+                         ccl_global int *num_indices,
+                         int num_active_paths)
+{
+  ccl_gpu_kernel_lambda((state >= num_active_paths) && (INTEGRATOR_STATE(state, path, queued_kernel) != 0),
+                        int num_active_paths)
+    .num_active_paths = num_active_paths;
+  
   gpu_parallel_active_index_array<GPU_PARALLEL_ACTIVE_INDEX_DEFAULT_BLOCK_SIZE>(
-      num_states, indices, num_indices, [num_active_paths](const int state) {
-        return (state >= num_active_paths) && (INTEGRATOR_STATE(state, path, queued_kernel) != 0);
-      });
+      num_states, indices, num_indices, ccl_gpu_kernel_lambda_pass);
 }
 
-extern "C" __global__ void __launch_bounds__(GPU_PARALLEL_SORTED_INDEX_DEFAULT_BLOCK_SIZE)
-    kernel_gpu_integrator_compact_states(const int *active_terminated_states,
-                                         const int active_states_offset,
-                                         const int terminated_states_offset,
-                                         const int work_size)
+ccl_gpu_kernel(GPU_PARALLEL_SORTED_INDEX_DEFAULT_BLOCK_SIZE)
+    ccl_gpu_kernel_signature(integrator_compact_states,
+                             ccl_global const int *active_terminated_states,
+                             const int active_states_offset,
+                             const int terminated_states_offset,
+                             const int work_size)
 {
   const int global_index = ccl_gpu_global_id_x();
 
@@ -341,28 +386,31 @@ extern "C" __global__ void __launch_bounds__(GPU_PARALLEL_SORTED_INDEX_DEFAULT_B
     const int from_state = active_terminated_states[active_states_offset + global_index];
     const int to_state = active_terminated_states[terminated_states_offset + global_index];
 
-    integrator_state_move(NULL, to_state, from_state);
+    ccl_gpu_kernel_call(integrator_state_move(NULL, to_state, from_state));
   }
 }
 
-extern "C" __global__ void __launch_bounds__(GPU_PARALLEL_ACTIVE_INDEX_DEFAULT_BLOCK_SIZE)
-    kernel_gpu_integrator_compact_shadow_paths_array(int num_states,
-                                                     int *indices,
-                                                     int *num_indices,
-                                                     int num_active_paths)
+ccl_gpu_kernel(GPU_PARALLEL_ACTIVE_INDEX_DEFAULT_BLOCK_SIZE)
+    ccl_gpu_kernel_signature(integrator_compact_shadow_paths_array,
+                             int num_states,
+                             ccl_global int *indices,
+                         ccl_global int *num_indices,
+                         int num_active_paths)
 {
+  ccl_gpu_kernel_lambda((state >= num_active_paths) && (INTEGRATOR_STATE(state, shadow_path, queued_kernel) != 0),
+                        int num_active_paths)
+    .num_active_paths = num_active_paths;
+
   gpu_parallel_active_index_array<GPU_PARALLEL_ACTIVE_INDEX_DEFAULT_BLOCK_SIZE>(
-      num_states, indices, num_indices, [num_active_paths](const int state) {
-        return (state >= num_active_paths) &&
-               (INTEGRATOR_STATE(state, shadow_path, queued_kernel) != 0);
-      });
+      num_states, indices, num_indices, ccl_gpu_kernel_lambda_pass);
 }
 
-extern "C" __global__ void __launch_bounds__(GPU_PARALLEL_SORTED_INDEX_DEFAULT_BLOCK_SIZE)
-    kernel_gpu_integrator_compact_shadow_states(const int *active_terminated_states,
-                                                const int active_states_offset,
-                                                const int terminated_states_offset,
-                                                const int work_size)
+ccl_gpu_kernel(GPU_PARALLEL_SORTED_INDEX_DEFAULT_BLOCK_SIZE)
+    ccl_gpu_kernel_signature(integrator_compact_shadow_states,
+                             ccl_global const int *active_terminated_states,
+                             const int active_states_offset,
+                             const int terminated_states_offset,
+                             const int work_size)
 {
   const int global_index = ccl_gpu_global_id_x();
 
@@ -370,15 +418,14 @@ extern "C" __global__ void __launch_bounds__(GPU_PARALLEL_SORTED_INDEX_DEFAULT_B
     const int from_state = active_terminated_states[active_states_offset + global_index];
     const int to_state = active_terminated_states[terminated_states_offset + global_index];
 
-    integrator_shadow_state_move(NULL, to_state, from_state);
+    ccl_gpu_kernel_call(integrator_shadow_state_move(NULL, to_state, from_state));
   }
 }
 
-extern "C" __global__ void __launch_bounds__(GPU_PARALLEL_PREFIX_SUM_DEFAULT_BLOCK_SIZE)
-    kernel_gpu_prefix_sum(int *counter, int *prefix_sum, int num_values)
+ccl_gpu_kernel(GPU_PARALLEL_PREFIX_SUM_DEFAULT_BLOCK_SIZE) ccl_gpu_kernel_signature(
+    prefix_sum, ccl_global int *counter, ccl_global int *prefix_sum, int num_values)
 {
-  gpu_parallel_prefix_sum<GPU_PARALLEL_PREFIX_SUM_DEFAULT_BLOCK_SIZE>(
-      counter, prefix_sum, num_values);
+  gpu_parallel_prefix_sum(ccl_gpu_global_id_x(), counter, prefix_sum, num_values);
 }
 
 /* --------------------------------------------------------------------
@@ -386,16 +433,17 @@ extern "C" __global__ void __launch_bounds__(GPU_PARALLEL_PREFIX_SUM_DEFAULT_BLO
  */
 
 ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
-    kernel_gpu_adaptive_sampling_convergence_check(float *render_buffer,
-                                                   int sx,
-                                                   int sy,
-                                                   int sw,
-                                                   int sh,
-                                                   float threshold,
-                                                   bool reset,
-                                                   int offset,
-                                                   int stride,
-                                                   uint *num_active_pixels)
+    ccl_gpu_kernel_signature(adaptive_sampling_convergence_check,
+                             ccl_global float *render_buffer,
+                             int sx,
+                             int sy,
+                             int sw,
+                             int sh,
+                             float threshold,
+                             bool reset,
+                             int offset,
+                             int stride,
+                             ccl_global uint *num_active_pixels)
 {
   const int work_index = ccl_gpu_global_id_x();
   const int y = work_index / sw;
@@ -404,37 +452,51 @@ ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
   bool converged = true;
 
   if (x < sw && y < sh) {
-    converged = kernel_adaptive_sampling_convergence_check(
-        nullptr, render_buffer, sx + x, sy + y, threshold, reset, offset, stride);
+    converged = ccl_gpu_kernel_call(kernel_adaptive_sampling_convergence_check(
+        nullptr, render_buffer, sx + x, sy + y, threshold, reset, offset, stride));
   }
 
   /* NOTE: All threads specified in the mask must execute the intrinsic. */
-  const uint num_active_pixels_mask = ccl_gpu_ballot(!converged);
+  const auto num_active_pixels_mask = ccl_gpu_ballot(!converged);
   const int lane_id = ccl_gpu_thread_idx_x % ccl_gpu_warp_size;
   if (lane_id == 0) {
-    atomic_fetch_and_add_uint32(num_active_pixels, __popc(num_active_pixels_mask));
+    atomic_fetch_and_add_uint32(num_active_pixels, ccl_gpu_popc(num_active_pixels_mask));
   }
 }
 
 ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
-    kernel_gpu_adaptive_sampling_filter_x(
-        float *render_buffer, int sx, int sy, int sw, int sh, int offset, int stride)
+    ccl_gpu_kernel_signature(adaptive_sampling_filter_x,
+                             ccl_global float *render_buffer,
+                             int sx,
+                             int sy,
+                             int sw,
+                             int sh,
+                             int offset,
+                             int stride)
 {
   const int y = ccl_gpu_global_id_x();
 
   if (y < sh) {
-    kernel_adaptive_sampling_filter_x(NULL, render_buffer, sy + y, sx, sw, offset, stride);
+    ccl_gpu_kernel_call(
+        kernel_adaptive_sampling_filter_x(NULL, render_buffer, sy + y, sx, sw, offset, stride));
   }
 }
 
 ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
-    kernel_gpu_adaptive_sampling_filter_y(
-        float *render_buffer, int sx, int sy, int sw, int sh, int offset, int stride)
+    ccl_gpu_kernel_signature(adaptive_sampling_filter_y,
+                             ccl_global float *render_buffer,
+                             int sx,
+                             int sy,
+                             int sw,
+                             int sh,
+                             int offset,
+                             int stride)
 {
   const int x = ccl_gpu_global_id_x();
 
   if (x < sw) {
-    kernel_adaptive_sampling_filter_y(NULL, render_buffer, sx + x, sy, sh, offset, stride);
+    ccl_gpu_kernel_call(
+        kernel_adaptive_sampling_filter_y(NULL, render_buffer, sx + x, sy, sh, offset, stride));
   }
 }
 
@@ -443,12 +505,14 @@ ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
  */
 
 ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
-    kernel_gpu_cryptomatte_postprocess(float *render_buffer, int num_pixels)
+    ccl_gpu_kernel_signature(cryptomatte_postprocess,
+                             ccl_global float *render_buffer,
+                             int num_pixels)
 {
   const int pixel_index = ccl_gpu_global_id_x();
 
   if (pixel_index < num_pixels) {
-    kernel_cryptomatte_post(nullptr, render_buffer, pixel_index);
+    ccl_gpu_kernel_call(kernel_cryptomatte_post(nullptr, render_buffer, pixel_index));
   }
 }
 
@@ -456,206 +520,102 @@ ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
  * Film.
  */
 
-/* Common implementation for float destination. */
-template<typename Processor>
-ccl_device_inline void kernel_gpu_film_convert_common(const KernelFilmConvert *kfilm_convert,
-                                                      float *pixels,
-                                                      float *render_buffer,
-                                                      int num_pixels,
-                                                      int width,
-                                                      int offset,
-                                                      int stride,
-                                                      int dst_offset,
-                                                      int dst_stride,
-                                                      const Processor &processor)
-{
-  const int render_pixel_index = ccl_gpu_global_id_x();
-  if (render_pixel_index >= num_pixels) {
-    return;
-  }
-
-  const int x = render_pixel_index % width;
-  const int y = render_pixel_index / width;
-
-  ccl_global const float *buffer = render_buffer + offset + x * kfilm_convert->pass_stride +
-                                   y * stride * kfilm_convert->pass_stride;
-
-  ccl_global float *pixel = pixels +
-                            (render_pixel_index + dst_offset) * kfilm_convert->pixel_stride;
-
-  processor(kfilm_convert, buffer, pixel);
-}
-
-/* Common implementation for half4 destination and 4-channel input pass. */
-template<typename Processor>
-ccl_device_inline void kernel_gpu_film_convert_half_rgba_common_rgba(
-    const KernelFilmConvert *kfilm_convert,
-    uchar4 *rgba,
-    float *render_buffer,
-    int num_pixels,
-    int width,
-    int offset,
-    int stride,
-    int rgba_offset,
-    int rgba_stride,
-    const Processor &processor)
-{
-  const int render_pixel_index = ccl_gpu_global_id_x();
-  if (render_pixel_index >= num_pixels) {
-    return;
-  }
-
-  const int x = render_pixel_index % width;
-  const int y = render_pixel_index / width;
-
-  ccl_global const float *buffer = render_buffer + offset + x * kfilm_convert->pass_stride +
-                                   y * stride * kfilm_convert->pass_stride;
-
-  float pixel[4];
-  processor(kfilm_convert, buffer, pixel);
-
-  film_apply_pass_pixel_overlays_rgba(kfilm_convert, buffer, pixel);
-
-  ccl_global half4 *out = ((ccl_global half4 *)rgba) + rgba_offset + y * rgba_stride + x;
-  *out = float4_to_half4_display(make_float4(pixel[0], pixel[1], pixel[2], pixel[3]));
-}
-
-/* Common implementation for half4 destination and 3-channel input pass. */
-template<typename Processor>
-ccl_device_inline void kernel_gpu_film_convert_half_rgba_common_rgb(
-    const KernelFilmConvert *kfilm_convert,
-    uchar4 *rgba,
-    float *render_buffer,
-    int num_pixels,
-    int width,
-    int offset,
-    int stride,
-    int rgba_offset,
-    int rgba_stride,
-    const Processor &processor)
-{
-  kernel_gpu_film_convert_half_rgba_common_rgba(
-      kfilm_convert,
-      rgba,
-      render_buffer,
-      num_pixels,
-      width,
-      offset,
-      stride,
-      rgba_offset,
-      rgba_stride,
-      [&processor](const KernelFilmConvert *kfilm_convert,
-                   ccl_global const float *buffer,
-                   float *pixel_rgba) {
-        processor(kfilm_convert, buffer, pixel_rgba);
-        pixel_rgba[3] = 1.0f;
-      });
-}
-
-/* Common implementation for half4 destination and single channel input pass. */
-template<typename Processor>
-ccl_device_inline void kernel_gpu_film_convert_half_rgba_common_value(
-    const KernelFilmConvert *kfilm_convert,
-    uchar4 *rgba,
-    float *render_buffer,
-    int num_pixels,
-    int width,
-    int offset,
-    int stride,
-    int rgba_offset,
-    int rgba_stride,
-    const Processor &processor)
-{
-  kernel_gpu_film_convert_half_rgba_common_rgba(
-      kfilm_convert,
-      rgba,
-      render_buffer,
-      num_pixels,
-      width,
-      offset,
-      stride,
-      rgba_offset,
-      rgba_stride,
-      [&processor](const KernelFilmConvert *kfilm_convert,
-                   ccl_global const float *buffer,
-                   float *pixel_rgba) {
-        float value;
-        processor(kfilm_convert, buffer, &value);
-
-        pixel_rgba[0] = value;
-        pixel_rgba[1] = value;
-        pixel_rgba[2] = value;
-        pixel_rgba[3] = 1.0f;
-      });
-}
-
-#define KERNEL_FILM_CONVERT_PROC(name) \
-  ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS) name
-
-#define KERNEL_FILM_CONVERT_DEFINE(variant, channels) \
-  KERNEL_FILM_CONVERT_PROC(kernel_gpu_film_convert_##variant) \
-  (const KernelFilmConvert kfilm_convert, \
-   float *pixels, \
-   float *render_buffer, \
-   int num_pixels, \
-   int width, \
-   int offset, \
-   int stride, \
-   int rgba_offset, \
-   int rgba_stride) \
+#define KERNEL_FILM_CONVERT_VARIANT(variant, input_channel_count) \
+  ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS) \
+      ccl_gpu_kernel_signature(film_convert_##variant, \
+                               const KernelFilmConvert kfilm_convert, \
+                               ccl_global uchar4 *rgba, \
+                               ccl_global float *render_buffer, \
+                               int num_pixels, \
+                               int width, \
+                               int offset, \
+                               int stride, \
+                               int rgba_offset, \
+                               int rgba_stride) \
   { \
-    kernel_gpu_film_convert_common(&kfilm_convert, \
-                                   pixels, \
-                                   render_buffer, \
-                                   num_pixels, \
-                                   width, \
-                                   offset, \
-                                   stride, \
-                                   rgba_offset, \
-                                   rgba_stride, \
-                                   film_get_pass_pixel_##variant); \
+    const int render_pixel_index = ccl_gpu_global_id_x(); \
+    if (render_pixel_index >= num_pixels) { \
+      return; \
+    } \
+\
+    const int x = render_pixel_index % width; \
+    const int y = render_pixel_index / width; \
+\
+    ccl_global const float *buffer = render_buffer + offset + x * kfilm_convert.pass_stride + \
+                                     y * stride * kfilm_convert.pass_stride; \
+\
+    float pixel[4]; \
+    film_get_pass_pixel_##variant(&kfilm_convert, buffer, pixel); \
+\
+    film_apply_pass_pixel_overlays_rgba(&kfilm_convert, buffer, pixel); \
+\
+    if (input_channel_count == 1) { \
+      pixel[1] = pixel[2] = pixel[0]; \
+    } \
+    if (input_channel_count <= 3) { \
+      pixel[3] = 1.0f; \
+    } \
+\
+    ccl_global float *out = ((ccl_global float *)rgba) + rgba_offset + y * rgba_stride + x; \
+    *(ccl_global float4 *)out = make_float4(pixel[0], pixel[1], pixel[2], pixel[3]); \
   } \
-  KERNEL_FILM_CONVERT_PROC(kernel_gpu_film_convert_##variant##_half_rgba) \
-  (const KernelFilmConvert kfilm_convert, \
-   uchar4 *rgba, \
-   float *render_buffer, \
-   int num_pixels, \
-   int width, \
-   int offset, \
-   int stride, \
-   int rgba_offset, \
-   int rgba_stride) \
+\
+  ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS) \
+      ccl_gpu_kernel_signature(film_convert_##variant##_half_rgba, \
+                               const KernelFilmConvert kfilm_convert, \
+                               ccl_global uchar4 *rgba, \
+                               ccl_global float *render_buffer, \
+                               int num_pixels, \
+                               int width, \
+                               int offset, \
+                               int stride, \
+                               int rgba_offset, \
+                               int rgba_stride) \
   { \
-    kernel_gpu_film_convert_half_rgba_common_##channels(&kfilm_convert, \
-                                                        rgba, \
-                                                        render_buffer, \
-                                                        num_pixels, \
-                                                        width, \
-                                                        offset, \
-                                                        stride, \
-                                                        rgba_offset, \
-                                                        rgba_stride, \
-                                                        film_get_pass_pixel_##variant); \
-  }
-
-KERNEL_FILM_CONVERT_DEFINE(depth, value)
-KERNEL_FILM_CONVERT_DEFINE(mist, value)
-KERNEL_FILM_CONVERT_DEFINE(sample_count, value)
-KERNEL_FILM_CONVERT_DEFINE(float, value)
-
-KERNEL_FILM_CONVERT_DEFINE(light_path, rgb)
-KERNEL_FILM_CONVERT_DEFINE(float3, rgb)
-
-KERNEL_FILM_CONVERT_DEFINE(motion, rgba)
-KERNEL_FILM_CONVERT_DEFINE(cryptomatte, rgba)
-KERNEL_FILM_CONVERT_DEFINE(shadow_catcher, rgba)
-KERNEL_FILM_CONVERT_DEFINE(shadow_catcher_matte_with_shadow, rgba)
-KERNEL_FILM_CONVERT_DEFINE(combined, rgba)
-KERNEL_FILM_CONVERT_DEFINE(float4, rgba)
-
-#undef KERNEL_FILM_CONVERT_DEFINE
-#undef KERNEL_FILM_CONVERT_HALF_RGBA_DEFINE
-#undef KERNEL_FILM_CONVERT_PROC
+    const int render_pixel_index = ccl_gpu_global_id_x(); \
+    if (render_pixel_index >= num_pixels) { \
+      return; \
+    } \
+\
+    const int x = render_pixel_index % width; \
+    const int y = render_pixel_index / width; \
+\
+    ccl_global const float *buffer = render_buffer + offset + x * kfilm_convert.pass_stride + \
+                                     y * stride * kfilm_convert.pass_stride; \
+\
+    float pixel[4]; \
+    film_get_pass_pixel_##variant(&kfilm_convert, buffer, pixel); \
+\
+    film_apply_pass_pixel_overlays_rgba(&kfilm_convert, buffer, pixel); \
+\
+    if (input_channel_count == 1) { \
+      pixel[1] = pixel[2] = pixel[0]; \
+    } \
+    if (input_channel_count <= 3) { \
+      pixel[3] = 1.0f; \
+    } \
+\
+    ccl_global half4 *out = ((ccl_global half4 *)rgba) + (rgba_offset + y * rgba_stride + x); \
+    *out = float4_to_half4_display(make_float4(pixel[0], pixel[1], pixel[2], pixel[3])); \
+  }
+
+/* 1 channel inputs */
+KERNEL_FILM_CONVERT_VARIANT(depth, 1)
+KERNEL_FILM_CONVERT_VARIANT(mist, 1)
+KERNEL_FILM_CONVERT_VARIANT(sample_count, 1)
+KERNEL_FILM_CONVERT_VARIANT(float, 1)
+
+/* 3 channel inputs */
+KERNEL_FILM_CONVERT_VARIANT(light_path, 3)
+KERNEL_FILM_CONVERT_VARIANT(float3, 3)
+
+/* 4 channel inputs */
+KERNEL_FILM_CONVERT_VARIANT(motion, 4)
+KERNEL_FILM_CONVERT_VARIANT(cryptomatte, 4)
+KERNEL_FILM_CONVERT_VARIANT(shadow_catcher, 4)
+KERNEL_FILM_CONVERT_VARIANT(shadow_catcher_matte_with_shadow, 4)
+KERNEL_FILM_CONVERT_VARIANT(combined, 4)
+KERNEL_FILM_CONVERT_VARIANT(float4, 4)
 
 /* --------------------------------------------------------------------
  * Shader evaluation.
@@ -664,42 +624,46 @@ KERNEL_FILM_CONVERT_DEFINE(float4, rgba)
 /* Displacement */
 
 ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
-    kernel_gpu_shader_eval_displace(KernelShaderEvalInput *input,
-                                    float *output,
-                                    const int offset,
-                                    const int work_size)
+    ccl_gpu_kernel_signature(shader_eval_displace,
+                             ccl_global KernelShaderEvalInput *input,
+                             ccl_global float *output,
+                             const int offset,
+                             const int work_size)
 {
   int i = ccl_gpu_global_id_x();
   if (i < work_size) {
-    kernel_displace_evaluate(NULL, input, output, offset + i);
+    ccl_gpu_kernel_call(kernel_displace_evaluate(NULL, input, output, offset + i));
   }
 }
 
 /* Background */
 
 ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
-    kernel_gpu_shader_eval_background(KernelShaderEvalInput *input,
-                                      float *output,
-                                      const int offset,
-                                      const int work_size)
+    ccl_gpu_kernel_signature(shader_eval_background,
+                             ccl_global KernelShaderEvalInput *input,
+                             ccl_global float *output,
+                             const int offset,
+                             const int work_size)
 {
   int i = ccl_gpu_global_id_x();
   if (i < work_size) {
-    kernel_background_evaluate(NULL, input, output, offset + i);
+    ccl_gpu_kernel_call(kernel_background_evaluate(NULL, input, output, offset + i));
   }
 }
 
 /* Curve Shadow Transparency */
 
 ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
-    kernel_gpu_shader_eval_curve_shadow_transparency(KernelShaderEvalInput *input,
-                                                     float *output,
-                                                     const int offset,
-                                                     const int work_size)
+    ccl_gpu_kernel_signature(shader_eval_curve_shadow_transparency,
+                             ccl_global KernelShaderEvalInput *input,
+                             ccl_global float *output,
+                             const int offset,
+                             const int work_size)
 {
   int i = ccl_gpu_global_id_x();
   if (i < work_size) {
-    kernel_curve_shadow_transparency_evaluate(NULL, input, output, offset + i);
+    ccl_gpu_kernel_call(
+        kernel_curve_shadow_transparency_evaluate(NULL, input, output, offset + i));
   }
 }
 
@@ -708,15 +672,16 @@ ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
  */
 
 ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
-    kernel_gpu_filter_color_preprocess(float *render_buffer,
-                                       int full_x,
-                                       int full_y,
-                                       int width,
-                                       int height,
-                                       int offset,
-                                       int stride,
-                                       int pass_stride,
-                                       int pass_denoised)
+    ccl_gpu_kernel_signature(filter_color_preprocess,
+                             ccl_global float *render_buffer,
+                             int full_x,
+                             int full_y,
+                             int width,
+                             int height,
+                             int offset,
+                             int stride,
+                             int pass_stride,
+                             int pass_denoised)
 {
   const int work_index = ccl_gpu_global_id_x();
   const int y = work_index / width;
@@ -727,31 +692,32 @@ ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
   }
 
   const uint64_t render_pixel_index = offset + (x + full_x) + (y + full_y) * stride;
-  float *buffer = render_buffer + render_pixel_index * pass_stride;
+  ccl_global float *buffer = render_buffer + render_pixel_index * pass_stride;
 
-  float *color_out = buffer + pass_denoised;
+  ccl_global float *color_out = buffer + pass_denoised;
   color_out[0] = clamp(color_out[0], 0.0f, 10000.0f);
   color_out[1] = clamp(color_out[1], 0.0f, 10000.0f);
   color_out[2] = clamp(color_out[2], 0.0f, 10000.0f);
 }
 
 ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
-    kernel_gpu_filter_guiding_preprocess(float *guiding_buffer,
-                                         int guiding_pass_stride,
-                                         int guiding_pass_albedo,
-                                         int guiding_pass_normal,
-                                         const float *render_buffer,
-                                         int render_offset,
-                                         int render_stride,
-                                         int render_pass_stride,
-                                         int render_pass_sample_count,
-                                         int render_pass_denoising_albedo,
-                                         int render_pass_denoising_normal,
-                                         int full_x,
-                                         int full_y,
-                                         int width,
-                                         int height,
-                                         int num_samples)
+    ccl_gpu_kernel_signature(filter_guiding_preprocess,
+                             ccl_global float *guiding_buffer,
+                             int guiding_pass_stride,
+                             int guiding_pass_albedo,
+                             int guiding_pass_normal,
+                             ccl_global const float *render_buffer,
+                             int render_offset,
+                             int render_stride,
+                             int render_pass_stride,
+                             int render_pass_sample_count,
+                             int render_pass_denoising_albedo,
+                             int render_pass_denoising_normal,
+                             int full_x,
+                             int full_y,
+                             int width,
+                             int height,
+                             int num_samples)
 {
   const int work_index = ccl_gpu_global_id_x();
   const int y = work_index / width;
@@ -762,10 +728,10 @@ ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
   }
 
   const uint64_t guiding_pixel_index = x + y * width;
-  float *guiding_pixel = guiding_buffer + guiding_pixel_index * guiding_pass_stride;
+  ccl_global float *guiding_pixel = guiding_buffer + guiding_pixel_index * guiding_pass_stride;
 
   const uint64_t render_pixel_index = render_offset + (x + full_x) + (y + full_y) * render_stride;
-  const float *buffer = render_buffer + render_pixel_index * render_pass_stride;
+  ccl_global const float *buffer = render_buffer + render_pixel_index * render_pass_stride;
 
   float pixel_scale;
   if (render_pass_sample_count == PASS_UNUSED) {
@@ -779,8 +745,8 @@ ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
   if (guiding_pass_albedo != PASS_UNUSED) {
     kernel_assert(render_pass_denoising_albedo != PASS_UNUSED);
 
-    const float *aledo_in = buffer + render_pass_denoising_albedo;
-    float *albedo_out = guiding_pixel + guiding_pass_albedo;
+    ccl_global const float *aledo_in = buffer + render_pass_denoising_albedo;
+    ccl_global float *albedo_out = guiding_pixel + guiding_pass_albedo;
 
     albedo_out[0] = aledo_in[0] * pixel_scale;
     albedo_out[1] = aledo_in[1] * pixel_scale;
@@ -791,8 +757,8 @@ ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
   if (guiding_pass_normal != PASS_UNUSED) {
     kernel_assert(render_pass_denoising_normal != PASS_UNUSED);
 
-    const float *normal_in = buffer + render_pass_denoising_normal;
-    float *normal_out = guiding_pixel + guiding_pass_normal;
+    ccl_global const float *normal_in = buffer + render_pass_denoising_normal;
+    ccl_global float *normal_out = guiding_pixel + guiding_pass_normal;
 
     normal_out[0] = normal_in[0] * pixel_scale;
     normal_out[1] = normal_in[1] * pixel_scale;
@@ -801,11 +767,12 @@ ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
 }
 
 ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
-    kernel_gpu_filter_guiding_set_fake_albedo(float *guiding_buffer,
-                                              int guiding_pass_stride,
-                                              int guiding_pass_albedo,
-                                              int width,
-                                              int height)
+    ccl_gpu_kernel_signature(filter_guiding_set_fake_albedo,
+                             ccl_global float *guiding_buffer,
+                             int guiding_pass_stride,
+                             int guiding_pass_albedo,
+                             int width,
+                             int height)
 {
   kernel_assert(guiding_pass_albedo != PASS_UNUSED);
 
@@ -818,9 +785,9 @@ ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
   }
 
   const uint64_t guiding_pixel_index = x + y * width;
-  float *guiding_pixel = guiding_buffer + guiding_pixel_index * guiding_pass_stride;
+  ccl_global float *guiding_pixel = guiding_buffer + guiding_pixel_index * guiding_pass_stride;
 
-  float *albedo_out = guiding_pixel + guiding_pass_albedo;
+  ccl_global float *albedo_out = guiding_pixel + guiding_pass_albedo;
 
   albedo_out[0] = 0.5f;
   albedo_out[1] = 0.5f;
@@ -828,20 +795,21 @@ ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
 }
 
 ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
-    kernel_gpu_filter_color_postprocess(float *render_buffer,
-                                        int full_x,
-                                        int full_y,
-                                        int width,
-                                        int height,
-                                        int offset,
-                                        int stride,
-                                        int pass_stride,
-                                        int num_samples,
-                                        int pass_noisy,
-                                        int pass_denoised,
-                                        int pass_sample_count,
-                                        int num_components,
-                                        bool use_compositing)
+    ccl_gpu_kernel_signature(filter_color_postprocess,
+                             ccl_global float *render_buffer,
+                             int full_x,
+                             int full_y,
+                             int width,
+                             int height,
+                             int offset,
+                             int stride,
+                             int pass_stride,
+                             int num_samples,
+                             int pass_noisy,
+                             int pass_denoised,
+                             int pass_sample_count,
+                             int num_components,
+                             bool use_compositing)
 {
   const int work_index = ccl_gpu_global_id_x();
   const int y = work_index / width;
@@ -852,7 +820,7 @@ ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
   }
 
   const uint64_t render_pixel_index = offset + (x + full_x) + (y + full_y) * stride;
-  float *buffer = render_buffer + render_pixel_index * pass_stride;
+  ccl_global float *buffer = render_buffer + render_pixel_index * pass_stride;
 
   float pixel_scale;
   if (pass_sample_count == PASS_UNUSED) {
@@ -862,7 +830,7 @@ ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
     pixel_scale = __float_as_uint(buffer[pass_sample_count]);
   }
 
-  float *denoised_pixel = buffer + pass_denoised;
+  ccl_global float *denoised_pixel = buffer + pass_denoised;
 
   denoised_pixel[0] *= pixel_scale;
   denoised_pixel[1] *= pixel_scale;
@@ -875,7 +843,7 @@ ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
     /* Currently compositing passes are either 3-component (derived by dividing light passes)
      * or do not have transparency (shadow catcher). Implicitly rely on this logic, as it
      * simplifies logic and avoids extra memory allocation. */
-    const float *noisy_pixel = buffer + pass_noisy;
+    ccl_global const float *noisy_pixel = buffer + pass_noisy;
     denoised_pixel[3] = noisy_pixel[3];
   }
   else {
@@ -891,21 +859,22 @@ ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
  */
 
 ccl_gpu_kernel(GPU_KERNEL_BLOCK_NUM_THREADS, GPU_KERNEL_MAX_REGISTERS)
-    kernel_gpu_integrator_shadow_catcher_count_possible_splits(int num_states,
-                                                               uint *num_possible_splits)
+    ccl_gpu_kernel_signature(integrator_shadow_catcher_count_possible_splits,
+                             int num_states,
+                             ccl_global uint *num_possible_splits)
 {
   const int state = ccl_gpu_global_id_x();
 
   bool can_split = false;
 
   if (state < num_states) {
-    can_split = kernel_shadow_catcher_path_can_split(nullptr, state);
+    can_split = ccl_gpu_kernel_call(kernel_shadow_catcher_path_can_split(nullptr, state));
   }
 
   /* NOTE: All threads specified in the mask must execute the intrinsic. */
-  const uint can_split_mask = ccl_gpu_ballot(can_split);
+  const auto can_split_mask = ccl_gpu_ballot(can_split);
   const int lane_id = ccl_gpu_thread_idx_x % ccl_gpu_warp_size;
   if (lane_id == 0) {
-    atomic_fetch_and_add_uint32(num_possible_splits, __popc(can_split_mask));
+    atomic_fetch_and_add_uint32(num_possible_splits, ccl_gpu_popc(can_split_mask));
   }
 }
diff --git a/intern/cycles/kernel/device/gpu/parallel_active_index.h b/intern/cycles/kernel/device/gpu/parallel_active_index.h
index d7416beb783..f667ede2712 100644
--- a/intern/cycles/kernel/device/gpu/parallel_active_index.h
+++ b/intern/cycles/kernel/device/gpu/parallel_active_index.h
@@ -31,10 +31,43 @@ CCL_NAMESPACE_BEGIN
 #  define GPU_PARALLEL_ACTIVE_INDEX_DEFAULT_BLOCK_SIZE 512
 #endif
 
+#ifdef __KERNEL_METAL__
+struct ActiveIndexContext {
+  ActiveIndexContext(int _thread_index,
+                     int _global_index,
+                     int _threadgroup_size,
+                     int _simdgroup_size,
+                     int _simd_lane_index,
+                     int _simd_group_index,
+                     int _num_simd_groups,
+                     threadgroup int *_simdgroup_offset)
+      : thread_index(_thread_index),
+        global_index(_global_index),
+        blocksize(_threadgroup_size),
+        ccl_gpu_warp_size(_simdgroup_size),
+        thread_warp(_simd_lane_index),
+        warp_index(_simd_group_index),
+        num_warps(_num_simd_groups),
+        warp_offset(_simdgroup_offset)
+  {
+  }
+
+  const int thread_index, global_index, blocksize, ccl_gpu_warp_size, thread_warp, warp_index,
+      num_warps;
+  threadgroup int *warp_offset;
+
+  template<uint blocksizeDummy, typename IsActiveOp>
+  void active_index_array(const uint num_states,
+                          ccl_global int *indices,
+                          ccl_global int *num_indices,
+                          IsActiveOp is_active_op)
+  {
+    const uint state_index = global_index;
+#else
 template<uint blocksize, typename IsActiveOp>
 __device__ void gpu_parallel_active_index_array(const uint num_states,
-                                                int *indices,
-                                                int *num_indices,
+                                                ccl_global int *indices,
+                                                ccl_global int *num_indices,
                                                 IsActiveOp is_active_op)
 {
   extern ccl_gpu_shared int warp_offset[];
@@ -45,43 +78,62 @@ __device__ void gpu_parallel_active_index_array(const uint num_states,
   const uint warp_index = thread_index / ccl_gpu_warp_size;
   const uint num_warps = blocksize / ccl_gpu_warp_size;
 
-  /* Test if state corresponding to this thread is active. */
   const uint state_index = ccl_gpu_block_idx_x * blocksize + thread_index;
-  const uint is_active = (state_index < num_states) ? is_active_op(state_index) : 0;
+#endif
 
-  /* For each thread within a warp compute how many other active states precede it. */
-  const uint thread_mask = 0xFFFFFFFF >> (ccl_gpu_warp_size - thread_warp);
-  const uint thread_offset = ccl_gpu_popc(ccl_gpu_ballot(is_active) & thread_mask);
+    /* Test if state corresponding to this thread is active. */
+    const uint is_active = (state_index < num_states) ? is_active_op(state_index) : 0;
 
-  /* Last thread in warp stores number of active states for each warp. */
-  if (thread_warp == ccl_gpu_warp_size - 1) {
-    warp_offset[warp_index] = thread_offset + is_active;
-  }
+    /* For each thread within a warp compute how many other active states precede it. */
+    const uint thread_offset = ccl_gpu_popc(ccl_gpu_ballot(is_active) &
+                                            ccl_gpu_thread_mask(thread_warp));
 
-  ccl_gpu_syncthreads();
-
-  /* Last thread in block converts per-warp sizes to offsets, increments global size of
-   * index array and gets offset to write to. */
-  if (thread_index == blocksize - 1) {
-    /* TODO: parallelize this. */
-    int offset = 0;
-    for (int i = 0; i < num_warps; i++) {
-      int num_active = warp_offset[i];
-      warp_offset[i] = offset;
-      offset += num_active;
+    /* Last thread in warp stores number of active states for each warp. */
+    if (thread_warp == ccl_gpu_warp_size - 1) {
+      warp_offset[warp_index] = thread_offset + is_active;
     }
 
-    const uint block_num_active = warp_offset[warp_index] + thread_offset + is_active;
-    warp_offset[num_warps] = atomic_fetch_and_add_uint32(num_indices, block_num_active);
-  }
+    ccl_gpu_syncthreads();
+
+    /* Last thread in block converts per-warp sizes to offsets, increments global size of
+     * index array and gets offset to write to. */
+    if (thread_index == blocksize - 1) {
+      /* TODO: parallelize this. */
+      int offset = 0;
+      for (int i = 0; i < num_warps; i++) {
+        int num_active = warp_offset[i];
+        warp_offset[i] = offset;
+        offset += num_active;
+      }
+
+      const uint block_num_active = warp_offset[warp_index] + thread_offset + is_active;
+      warp_offset[num_warps] = atomic_fetch_and_add_uint32(num_indices, block_num_active);
+    }
 
-  ccl_gpu_syncthreads();
+    ccl_gpu_syncthreads();
 
-  /* Write to index array. */
-  if (is_active) {
-    const uint block_offset = warp_offset[num_warps];
-    indices[block_offset + warp_offset[warp_index] + thread_offset] = state_index;
+    /* Write to index array. */
+    if (is_active) {
+      const uint block_offset = warp_offset[num_warps];
+      indices[block_offset + warp_offset[warp_index] + thread_offset] = state_index;
+    }
   }
-}
+
+#ifdef __KERNEL_METAL__
+}; /* end class ActiveIndexContext */
+
+/* inject the required thread params into a struct, and redirect to its templated member function
+ */
+#  define gpu_parallel_active_index_array \
+    ActiveIndexContext(metal_local_id, \
+                       metal_global_id, \
+                       metal_local_size, \
+                       simdgroup_size, \
+                       simd_lane_index, \
+                       simd_group_index, \
+                       num_simd_groups, \
+                       simdgroup_offset) \
+        .active_index_array
+#endif
 
 CCL_NAMESPACE_END
diff --git a/intern/cycles/kernel/device/gpu/parallel_prefix_sum.h b/intern/cycles/kernel/device/gpu/parallel_prefix_sum.h
index 6de3a022569..4bd002c27e4 100644
--- a/intern/cycles/kernel/device/gpu/parallel_prefix_sum.h
+++ b/intern/cycles/kernel/device/gpu/parallel_prefix_sum.h
@@ -33,10 +33,12 @@ CCL_NAMESPACE_BEGIN
 #  define GPU_PARALLEL_PREFIX_SUM_DEFAULT_BLOCK_SIZE 512
 #endif
 
-template<uint blocksize>
-__device__ void gpu_parallel_prefix_sum(int *counter, int *prefix_sum, const int num_values)
+__device__ void gpu_parallel_prefix_sum(const int global_id,
+                                        ccl_global int *counter,
+                                        ccl_global int *prefix_sum,
+                                        const int num_values)
 {
-  if (!(ccl_gpu_block_idx_x == 0 && ccl_gpu_thread_idx_x == 0)) {
+  if (global_id != 0) {
     return;
   }
 
diff --git a/intern/cycles/kernel/device/gpu/parallel_sorted_index.h b/intern/cycles/kernel/device/gpu/parallel_sorted_index.h
index c06d7be444f..c092e2a21ee 100644
--- a/intern/cycles/kernel/device/gpu/parallel_sorted_index.h
+++ b/intern/cycles/kernel/device/gpu/parallel_sorted_index.h
@@ -33,16 +33,16 @@ CCL_NAMESPACE_BEGIN
 #endif
 #define GPU_PARALLEL_SORTED_INDEX_INACTIVE_KEY (~0)
 
-template<uint blocksize, typename GetKeyOp>
-__device__ void gpu_parallel_sorted_index_array(const uint num_states,
+template<typename GetKeyOp>
+__device__ void gpu_parallel_sorted_index_array(const uint state_index,
+                                                const uint num_states,
                                                 const int num_states_limit,
-                                                int *indices,
-                                                int *num_indices,
-                                                int *key_counter,
-                                                int *key_prefix_sum,
+                                                ccl_global int *indices,
+                                                ccl_global int *num_indices,
+                                                ccl_global int *key_counter,
+                                                ccl_global int *key_prefix_sum,
                                                 GetKeyOp get_key_op)
 {
-  const uint state_index = ccl_gpu_block_idx_x * blocksize + ccl_gpu_thread_idx_x;
   const int key = (state_index < num_states) ? get_key_op(state_index) :
                                                GPU_PARALLEL_SORTED_INDEX_INACTIVE_KEY;
 
diff --git a/intern/cycles/kernel/device/hip/compat.h b/intern/cycles/kernel/device/hip/compat.h
index 282c3eca641..fb07602539b 100644
--- a/intern/cycles/kernel/device/hip/compat.h
+++ b/intern/cycles/kernel/device/hip/compat.h
@@ -74,6 +74,7 @@ typedef unsigned long long uint64_t;
 #define ccl_gpu_block_idx_x (blockIdx.x)
 #define ccl_gpu_grid_dim_x (gridDim.x)
 #define ccl_gpu_warp_size (warpSize)
+#define ccl_gpu_thread_mask(thread_warp) uint(0xFFFFFFFF >> (ccl_gpu_warp_size - thread_warp))
 
 #define ccl_gpu_global_id_x() (ccl_gpu_block_idx_x * ccl_gpu_block_dim_x + ccl_gpu_thread_idx_x)
 #define ccl_gpu_global_size_x() (ccl_gpu_grid_dim_x * ccl_gpu_block_dim_x)
diff --git a/intern/cycles/kernel/device/hip/config.h b/intern/cycles/kernel/device/hip/config.h
index 2fde0d46015..b9dbc2f7fa8 100644
--- a/intern/cycles/kernel/device/hip/config.h
+++ b/intern/cycles/kernel/device/hip/config.h
@@ -36,11 +36,35 @@
 /* Compute number of threads per block and minimum blocks per multiprocessor
  * given the maximum number of registers per thread. */
 
-#define ccl_gpu_kernel(block_num_threads, thread_num_registers) \
+#define ccl_gpu_kernel_threads(block_num_threads) \
+  extern "C" __global__ void __launch_bounds__(block_num_threads)
+
+#define ccl_gpu_kernel_threads_registers(block_num_threads, thread_num_registers) \
   extern "C" __global__ void __launch_bounds__(block_num_threads, \
                                                GPU_MULTIPRESSOR_MAX_REGISTERS / \
                                                    (block_num_threads * thread_num_registers))
 
+/* allow ccl_gpu_kernel to accept 1 or 2 parameters */
+#define SELECT_MACRO(_1, _2, NAME, ...) NAME
+#define ccl_gpu_kernel(...) \
+  SELECT_MACRO(__VA_ARGS__, ccl_gpu_kernel_threads_registers, ccl_gpu_kernel_threads)(__VA_ARGS__)
+
+#define ccl_gpu_kernel_signature(name, ...) kernel_gpu_##name(__VA_ARGS__)
+
+#define ccl_gpu_kernel_call(x) x
+
+/* define a function object where "func" is the lambda body, and additional parameters are used to
+ * specify captured state  */
+#define ccl_gpu_kernel_lambda(func, ...) \
+  struct KernelLambda { \
+    __VA_ARGS__; \
+    __device__ int operator()(const int state) \
+    { \
+      return (func); \
+    } \
+  } ccl_gpu_kernel_lambda_pass; \
+  ccl_gpu_kernel_lambda_pass
+
 /* sanity checks */
 
 #if GPU_KERNEL_BLOCK_NUM_THREADS > GPU_BLOCK_MAX_THREADS
diff --git a/intern/cycles/kernel/device/metal/compat.h b/intern/cycles/kernel/device/metal/compat.h
index 77cea30914c..57c6845e508 100644
--- a/intern/cycles/kernel/device/metal/compat.h
+++ b/intern/cycles/kernel/device/metal/compat.h
@@ -58,6 +58,95 @@ using namespace metal;
 
 #define kernel_assert(cond)
 
+#define ccl_gpu_global_id_x() metal_global_id
+#define ccl_gpu_warp_size simdgroup_size
+#define ccl_gpu_thread_idx_x simd_group_index
+#define ccl_gpu_thread_mask(thread_warp) uint64_t((1ull << thread_warp) - 1)
+
+#define ccl_gpu_ballot(predicate) ((uint64_t)((simd_vote::vote_t)simd_ballot(predicate)))
+#define ccl_gpu_popc(x) popcount(x)
+
+// clang-format off
+
+/* kernel.h adapters */
+
+#define ccl_gpu_kernel(...)
+
+/* convert a comma-separated list into a semicolon-separated list (so that we can generate a struct based on kernel entrypoint parameters) */
+#define FN0()
+#define FN1(p1) p1;
+#define FN2(p1, p2) p1; p2;
+#define FN3(p1, p2, p3) p1; p2; p3;
+#define FN4(p1, p2, p3, p4) p1; p2; p3; p4;
+#define FN5(p1, p2, p3, p4, p5) p1; p2; p3; p4; p5;
+#define FN6(p1, p2, p3, p4, p5, p6) p1; p2; p3; p4; p5; p6;
+#define FN7(p1, p2, p3, p4, p5, p6, p7) p1; p2; p3; p4; p5; p6; p7;
+#define FN8(p1, p2, p3, p4, p5, p6, p7, p8) p1; p2; p3; p4; p5; p6; p7; p8;
+#define FN9(p1, p2, p3, p4, p5, p6, p7, p8, p9) p1; p2; p3; p4; p5; p6; p7; p8; p9;
+#define FN10(p1, p2, p3, p4, p5, p6, p7, p8, p9, p10) p1; p2; p3; p4; p5; p6; p7; p8; p9; p10;
+#define FN11(p1, p2, p3, p4, p5, p6, p7, p8, p9, p10, p11) p1; p2; p3; p4; p5; p6; p7; p8; p9; p10; p11;
+#define FN12(p1, p2, p3, p4, p5, p6, p7, p8, p9, p10, p11, p12) p1; p2; p3; p4; p5; p6; p7; p8; p9; p10; p11; p12;
+#define FN13(p1, p2, p3, p4, p5, p6, p7, p8, p9, p10, p11, p12, p13) p1; p2; p3; p4; p5; p6; p7; p8; p9; p10; p11; p12; p13;
+#define FN14(p1, p2, p3, p4, p5, p6, p7, p8, p9, p10, p11, p12, p13, p14) p1; p2; p3; p4; p5; p6; p7; p8; p9; p10; p11; p12; p13; p14;
+#define FN15(p1, p2, p3, p4, p5, p6, p7, p8, p9, p10, p11, p12, p13, p14, p15) p1; p2; p3; p4; p5; p6; p7; p8; p9; p10; p11; p12; p13; p14; p15;
+#define FN16(p1, p2, p3, p4, p5, p6, p7, p8, p9, p10, p11, p12, p13, p14, p15, p16) p1; p2; p3; p4; p5; p6; p7; p8; p9; p10; p11; p12; p13; p14; p15; p16;
+#define GET_LAST_ARG(p0, p1, p2, p3, p4, p5, p6, p7, p8, p9, p10, p11, p12, p13, p14, p15, p16, ...) p16
+#define PARAMS_MAKER(...) GET_LAST_ARG(__VA_ARGS__, FN16, FN15, FN14, FN13, FN12, FN11, FN10, FN9, FN8, FN7, FN6, FN5, FN4, FN3, FN2, FN1, FN0)
+
+/* generate a struct containing the entrypoint parameters and a "run" method which can access them implicitly via this-> */
+#define ccl_gpu_kernel_signature(name, ...) \
+struct kernel_gpu_##name \
+{ \
+  PARAMS_MAKER(__VA_ARGS__)(__VA_ARGS__) \
+  void run(thread MetalKernelContext& context, \
+           threadgroup int *simdgroup_offset, \
+           const uint metal_global_id, \
+           const ushort metal_local_id, \
+           const ushort metal_local_size, \
+           uint simdgroup_size, \
+           uint simd_lane_index, \
+           uint simd_group_index, \
+           uint num_simd_groups) ccl_global const; \
+}; \
+kernel void kernel_metal_##name(device const kernel_gpu_##name *params_struct, \
+                                constant KernelParamsMetal &ccl_restrict   _launch_params_metal, \
+                                constant MetalAncillaries *_metal_ancillaries, \
+                                threadgroup int *simdgroup_offset[[ threadgroup(0) ]], \
+                                const uint metal_global_id [[thread_position_in_grid]], \
+                                const ushort metal_local_id   [[thread_position_in_threadgroup]], \
+                                const ushort metal_local_size [[threads_per_threadgroup]], \
+                                uint simdgroup_size [[threads_per_simdgroup]], \
+                                uint simd_lane_index [[thread_index_in_simdgroup]], \
+                                uint simd_group_index [[simdgroup_index_in_threadgroup]], \
+                                uint num_simd_groups [[simdgroups_per_threadgroup]]) { \
+  MetalKernelContext context(_launch_params_metal, _metal_ancillaries); \
+  INIT_DEBUG_BUFFER \
+  params_struct->run(context, simdgroup_offset, metal_global_id, metal_local_id, metal_local_size, simdgroup_size, simd_lane_index, simd_group_index, num_simd_groups); \
+} \
+void kernel_gpu_##name::run(thread MetalKernelContext& context, \
+                  threadgroup int *simdgroup_offset, \
+                  const uint metal_global_id, \
+                  const ushort metal_local_id, \
+                  const ushort metal_local_size, \
+                  uint simdgroup_size, \
+                  uint simd_lane_index, \
+                  uint simd_group_index, \
+                  uint num_simd_groups) ccl_global const
+
+#define ccl_gpu_kernel_call(x) context.x
+
+/* define a function object where "func" is the lambda body, and additional parameters are used to specify captured state  */
+#define ccl_gpu_kernel_lambda(func, ...) \
+  struct KernelLambda \
+  { \
+    KernelLambda(ccl_private MetalKernelContext &_context) : context(_context) {} \
+    ccl_private MetalKernelContext &context; \
+    __VA_ARGS__; \
+    int operator()(const int state) const { return (func); } \
+  }ccl_gpu_kernel_lambda_pass(context); ccl_gpu_kernel_lambda_pass
+
+// clang-format on
+
 /* make_type definitions with Metal style element initializers */
 #ifdef make_float2
 #  undef make_float2
@@ -124,3 +213,38 @@ using namespace metal;
 #define logf(x) trigmode::log(float(x))
 
 #define NULL 0
+
+/* texture bindings and sampler setup */
+
+struct Texture2DParamsMetal {
+  texture2d<float, access::sample> tex;
+};
+struct Texture3DParamsMetal {
+  texture3d<float, access::sample> tex;
+};
+
+struct MetalAncillaries {
+  device Texture2DParamsMetal *textures_2d;
+  device Texture3DParamsMetal *textures_3d;
+};
+
+enum SamplerType {
+  SamplerFilterNearest_AddressRepeat,
+  SamplerFilterNearest_AddressClampEdge,
+  SamplerFilterNearest_AddressClampZero,
+
+  SamplerFilterLinear_AddressRepeat,
+  SamplerFilterLinear_AddressClampEdge,
+  SamplerFilterLinear_AddressClampZero,
+
+  SamplerCount
+};
+
+constant constexpr array<sampler, SamplerCount> metal_samplers = {
+    sampler(address::repeat, filter::nearest),
+    sampler(address::clamp_to_edge, filter::nearest),
+    sampler(address::clamp_to_zero, filter::nearest),
+    sampler(address::repeat, filter::linear),
+    sampler(address::clamp_to_edge, filter::linear),
+    sampler(address::clamp_to_zero, filter::linear),
+};
\ No newline at end of file
diff --git a/intern/cycles/kernel/device/metal/context_begin.h b/intern/cycles/kernel/device/metal/context_begin.h
new file mode 100644
index 00000000000..3b5fcdd1f7f
--- /dev/null
+++ b/intern/cycles/kernel/device/metal/context_begin.h
@@ -0,0 +1,79 @@
+/*
+ * Copyright 2021 Blender Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// clang-format off
+
+/* Open the Metal kernel context class
+ * Necessary to access resource bindings */
+class MetalKernelContext {
+  public:
+    constant KernelParamsMetal &launch_params_metal;
+    constant MetalAncillaries *metal_ancillaries;
+
+    MetalKernelContext(constant KernelParamsMetal &_launch_params_metal, constant MetalAncillaries * _metal_ancillaries)
+    : launch_params_metal(_launch_params_metal), metal_ancillaries(_metal_ancillaries)
+    {}
+
+    /* texture fetch adapter functions */
+    typedef uint64_t ccl_gpu_tex_object;
+
+    template<typename T>
+    inline __attribute__((__always_inline__))
+    T ccl_gpu_tex_object_read_2D(ccl_gpu_tex_object tex, float x, float y) const {
+      kernel_assert(0);
+      return 0;
+    }
+    template<typename T>
+    inline __attribute__((__always_inline__))
+    T ccl_gpu_tex_object_read_3D(ccl_gpu_tex_object tex, float x, float y, float z) const {
+      kernel_assert(0);
+      return 0;
+    }
+
+    // texture2d
+    template<>
+    inline __attribute__((__always_inline__))
+    float4 ccl_gpu_tex_object_read_2D(ccl_gpu_tex_object tex, float x, float y) const {
+      const uint tid(tex);
+      const uint sid(tex >> 32);
+      return metal_ancillaries->textures_2d[tid].tex.sample(metal_samplers[sid], float2(x, y));
+    }
+    template<>
+    inline __attribute__((__always_inline__))
+    float ccl_gpu_tex_object_read_2D(ccl_gpu_tex_object tex, float x, float y) const {
+      const uint tid(tex);
+      const uint sid(tex >> 32);
+      return metal_ancillaries->textures_2d[tid].tex.sample(metal_samplers[sid], float2(x, y)).x;
+    }
+
+    // texture3d
+    template<>
+    inline __attribute__((__always_inline__))
+    float4 ccl_gpu_tex_object_read_3D(ccl_gpu_tex_object tex, float x, float y, float z) const {
+      const uint tid(tex);
+      const uint sid(tex >> 32);
+      return metal_ancillaries->textures_3d[tid].tex.sample(metal_samplers[sid], float3(x, y, z));
+    }
+    template<>
+    inline __attribute__((__always_inline__))
+    float ccl_gpu_tex_object_read_3D(ccl_gpu_tex_object tex, float x, float y, float z) const {
+      const uint tid(tex);
+      const uint sid(tex >> 32);
+      return metal_ancillaries->textures_3d[tid].tex.sample(metal_samplers[sid], float3(x, y, z)).x;
+    }
+#    include "kernel/device/gpu/image.h"
+
+  // clang-format on
\ No newline at end of file
diff --git a/intern/cycles/kernel/device/metal/context_end.h b/intern/cycles/kernel/device/metal/context_end.h
new file mode 100644
index 00000000000..811abdec150
--- /dev/null
+++ b/intern/cycles/kernel/device/metal/context_end.h
@@ -0,0 +1,23 @@
+/*
+ * Copyright 2021 Blender Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+}
+; /* end of MetalKernelContext class definition */
+
+/* Silently redirect into the MetalKernelContext instance */
+/* NOTE: These macros will need maintaining as entrypoints change */
+
+#undef kernel_integrator_state
+#define kernel_integrator_state context.launch_params_metal.__integrator_state
diff --git a/intern/cycles/kernel/device/metal/globals.h b/intern/cycles/kernel/device/metal/globals.h
new file mode 100644
index 00000000000..b4963518b63
--- /dev/null
+++ b/intern/cycles/kernel/device/metal/globals.h
@@ -0,0 +1,51 @@
+/*
+ * Copyright 2021 Blender Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/* Constant Globals */
+
+#include "kernel/types.h"
+#include "kernel/util/profiling.h"
+
+#include "kernel/integrator/state.h"
+
+CCL_NAMESPACE_BEGIN
+
+typedef struct KernelParamsMetal {
+
+#define KERNEL_TEX(type, name) ccl_constant type *name;
+#include "kernel/textures.h"
+#undef KERNEL_TEX
+
+  const IntegratorStateGPU __integrator_state;
+  const KernelData data;
+
+} KernelParamsMetal;
+
+typedef struct KernelGlobalsGPU {
+  int unused[1];
+} KernelGlobalsGPU;
+
+typedef ccl_global const KernelGlobalsGPU *ccl_restrict KernelGlobals;
+
+#define kernel_data launch_params_metal.data
+#define kernel_integrator_state launch_params_metal.__integrator_state
+
+/* data lookup defines */
+
+#define kernel_tex_fetch(tex, index) launch_params_metal.tex[index]
+#define kernel_tex_array(tex) launch_params_metal.tex
+
+CCL_NAMESPACE_END
diff --git a/intern/cycles/kernel/device/metal/kernel.metal b/intern/cycles/kernel/device/metal/kernel.metal
new file mode 100644
index 00000000000..feca20ff475
--- /dev/null
+++ b/intern/cycles/kernel/device/metal/kernel.metal
@@ -0,0 +1,25 @@
+/*
+ * Copyright 2021 Blender Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/* Metal kernel entry points */
+
+// clang-format off
+
+#include "kernel/device/metal/compat.h"
+#include "kernel/device/metal/globals.h"
+#include "kernel/device/gpu/kernel.h"
+
+// clang-format on
\ No newline at end of file
diff --git a/intern/cycles/kernel/device/optix/compat.h b/intern/cycles/kernel/device/optix/compat.h
index 835e4621d47..482b921a1a8 100644
--- a/intern/cycles/kernel/device/optix/compat.h
+++ b/intern/cycles/kernel/device/optix/compat.h
@@ -76,6 +76,7 @@ typedef unsigned long long uint64_t;
 #define ccl_gpu_block_idx_x (blockIdx.x)
 #define ccl_gpu_grid_dim_x (gridDim.x)
 #define ccl_gpu_warp_size (warpSize)
+#define ccl_gpu_thread_mask(thread_warp) uint(0xFFFFFFFF >> (ccl_gpu_warp_size - thread_warp))
 
 #define ccl_gpu_global_id_x() (ccl_gpu_block_idx_x * ccl_gpu_block_dim_x + ccl_gpu_thread_idx_x)
 #define ccl_gpu_global_size_x() (ccl_gpu_grid_dim_x * ccl_gpu_block_dim_x)