Metal: Storage buffer and explicit bind location support

Adds support for Storage buffers, including changes to the resource
binding model to ensure explicit resource bind locations are supported
for all resource types.

Storage buffer support also includes required changes for shader
source generation and SSBO wrapper support for other resource
types such as GPUVertBuf, GPUIndexBuf and GPUUniformBuf.

Authored by Apple: Michael Parkin-White

@@ -463,0 +469,4 @@
+  if (ctx) {
+    ctx->compute_dispatch_indirect(indirect_buf);
+  }
+  }

@@ -883,0 +894,4 @@
+  MTLContext *ctx = reinterpret_cast<MTLContext *>(GPU_context_active_get());
+  id<MTLRenderCommandEncoder> rec = this->bind(0);
+  if (rec == nil) {
+    printf("Failed to open Render Command encoder for DRAW INDIRECT\n");

@@ -2012,1 +2118,4 @@
 
+  /* Early fragment tests. */
+  if(uses_early_fragment_test) {
+  out << "[[early_fragment_tests]]" << std::endl;

@@ -883,0 +919,4 @@
+  id<MTLBuffer> mtl_indirect_buf = mtlssbo->get_metal_buffer();
+  BLI_assert(mtl_indirect_buf != nil);
+  if (mtl_indirect_buf == nil) {
+    printf("Metal Indirect Draw Storage Buffer is nil.\n");

@@ -883,0 +910,4 @@
+  MTLPrimitiveType mtl_prim_type = gpu_prim_type_to_metal(this->prim_type);
+
+  if (mtl_needs_topology_emulation(this->prim_type)) {
+    printf("Metal Topology emulation unsupported for draw indirect.\n");

@@ -272,0 +298,4 @@
+  for (int i = 0; i < MTL_MAX_BUFFER_BINDINGS; i++) {
+    if (this->pipeline_state.ssbo_bindings[i].bound &&
+        this->pipeline_state.ssbo_bindings[i].ssbo != nullptr) {
+      GPUStorageBuf *ssbo = wrap(

@@ -1192,0 +1247,4 @@
+
+  /* Bind Global GPUStorageBuf's */
+  /* Iterate through expected SSBOs in the shader interface, and check if the globally bound ones
+   * match. This is used to support the gpu_uniformbuffer module, where the uniform data is global,

@@ -1192,0 +1263,4 @@
+
+      if (this->pipeline_state.ssbo_bindings[ssbo_location].bound) {
+
+        /* Fetch UBO global-binding properties from slot. */

@@ -1923,0 +2153,4 @@
+void MTLContext::compute_dispatch_indirect(StorageBuf *indirect_buf)
+{
+  /* Ensure all resources required by upcoming compute submission are correctly bound. */
+  if (this->ensure_compute_pipeline_state()) {

@@ -2003,3 +2286,4 @@
 {
   BLI_assert(mtl_texture);
 
+  MTLTextureBinding(

@@ -990,0 +992,4 @@
+     * and an additional space for the push constant block.
+     * If the shader does not have any uniform blocks, then we can place directly after the push
+     * constant block. As we do not need an extra spot for the UBO at index '0'. */
+    int MTL_storage_buffer_base_index = MTL_uniform_buffer_base_index + 1 +

@@ -713,0 +716,4 @@
+      const char *memory_scope = ((writeable) ? "device " : "constant ");
+      if (array_offset == -1) {
+        /* Create local class member as device pointer reference to bound SSBO.
+         * Given usage within a shader follows ssbo_name.ubo_element syntax, we can

@@ -1769,4 +1814,3 @@
           }
-          BLI_assert(used_slot >= 0 && used_slot < MTL_MAX_TEXTURE_SLOTS);
 
           /* Writeable image targets only assigned to Fragment and compute shaders. */

@@ -7,0 +228,4 @@
+void MTLStorageBuf::copy_sub(VertBuf *src_, uint dst_offset, uint src_offset, uint copy_size)
+{
+  /* TODO(Metal): Support Copy sub operation. */
+  MTL_LOG_WARNING("TLStorageBuf::copy_sub not yet supported.\n");