[metal] Add some TODOs for expected changes in command buffer
diff --git a/experimental/metal/direct_command_buffer.m b/experimental/metal/direct_command_buffer.m
index a6f3fbf..246b420 100644
--- a/experimental/metal/direct_command_buffer.m
+++ b/experimental/metal/direct_command_buffer.m
@@ -199,6 +199,9 @@
// binding buffers. So we need to cache the descriptor information by ourselves and apply them in
// a delayed manner.
+ // TODO(antiagainst): Switch to use separate lists for different descriptor sets to avoid the
+ // overhead of sorting and iterating through the whole list.
+
// A sorted flat list of descriptors from all pushed descriptor sets.
iree_hal_metal_descriptor_t current_descriptors[IREE_HAL_METAL_MAX_BINDING_COUNT];
// The total used slot count / next unused slot index in |current_descriptors|.
@@ -468,6 +471,9 @@
static iree_status_t iree_hal_metal_command_segment_record_barrier(
iree_hal_metal_command_buffer_t* command_buffer, iree_hal_metal_barrier_segment_t* segment) {
+ // TODO(antiagainst): Analyze segments before and after to optimize barriers, e.g., switching
+ // encoders would require its own synchronization; so we don't need extract barriers in the
+ // middle.
if (segment->memory_barrier_count == 0 && segment->buffer_barrier_count == 0) {
// There is no direct corresponding APIs for execution only barrier in Metal. We just signal and
// wait on the same value of a MTLEvent here.
@@ -1013,6 +1019,8 @@
uint32_t current_set = descriptors[i].set;
// Build argument encoder and argument buffer for the current descriptor set.
+ // TODO(antiagainst): Use a cache layer to cache and reuse argument buffers with the same
+ // content, to avoid duplicating overhead.
id<MTLBuffer> argument_buffer = command_buffer->staging_buffer->metal_buffer;
id<MTLArgumentEncoder> argument_encoder =
[segment->kernel_params.function newArgumentEncoderWithBufferIndex:current_set]; // +1
