Restructure GPU execution to model GPU pipelines in the node graph (#1088)

* Start implementing GpuExecutor for wgpu

* Implement read_output_buffer function

* Implement extraction node in the compiler

* Generate type annotations during shader compilation

* Start adding node wrapprs for graph execution api

* Wrap more of the api in nodes

* Restructure Pipeline to accept arbitrary shader inputs

* Adapt nodes to new trait definitions

* Start implementing gpu-compiler trait

* Adapt shader generation

* Hardstuck on pointer casts

* Pass nodes as references in gpu code to avoid zsts

* Update gcore to compile on the gpu

* Fix color doc tests

* Impl Node for node refs

node-graph/gpu-compiler/src/templates/spirv-template.rs

@@ -1,6 +1,5 @@
 #![no_std]
 #![feature(unchecked_math)]
-#![deny(warnings)]
 
 #[cfg(target_arch = "spirv")]
 extern crate spirv_std;
@@ -14,25 +13,23 @@ pub mod gpu {
 	#[allow(unused)]
 	#[spirv(compute(threads({{compute_threads}})))]
 	pub fn eval (
-		#[spirv(global_invocation_id)] global_id: UVec3,
-		#[spirv(storage_buffer, descriptor_set = 0, binding = 0)] a: &[{{input_type}}],
-		#[spirv(storage_buffer, descriptor_set = 0, binding = 1)] y: &mut [{{output_type}}],
-		//#[spirv(push_constant)] push_consts: &graphene_core::gpu::PushConstants,
+		{% for input in inputs %}
+		{{input}}
+		{% endfor %}
 	) {
-		let gid = global_id.x as usize;
-		// Only process up to n, which is the length of the buffers.
-		//if global_id.x < push_consts.n {
-			y[gid] = node_graph(a[gid]);
-		//}
-	}
-
-	fn node_graph(input: {{input_type}}) -> {{output_type}} {
 		use graphene_core::Node;
 
+		{% for input in input_nodes %}
+		let i{{loop.index0}} = graphene_core::value::CopiedNode::new(i{{loop.index0}});
+		let _{{input.id}} = {{input.fqn}}::new({% for arg in input.args %}{{arg}}, {% endfor %});
+		let {{input.id}} = graphene_core::structural::ComposeNode::new(i{{loop.index0}}, _{{input.id}});
+		{% endfor %}
+
 		{% for node in nodes %}
 		let {{node.id}} = {{node.fqn}}::new({% for arg in node.args %}{{arg}}, {% endfor %});
 		{% endfor %}
-		{{last_node}}.eval(input)
-	}
+		let output = {{last_node}}.eval(());
+		// TODO: Write output to buffer
 
+	}
 }