wgpu: Cache Program3D bind group layout

The bind group layout only depends on the texture registers
(and 2D/cubemap type) accessed by the fragment shader, not on
the runtime texture bound with Context3D. This means that we can
build and cache it when we compile the AGAL program to a Naga
module.

Since the bind group layout is used for the overall pipeline, I've
refactored the shader caching code into `ShaderPairAgal`, which
holds both the vertex and fragment shader bytecode, and compiles
both in the `compile` function.

core/src/avm2/object/context3d_object.rs

@@ -249,9 +249,8 @@ impl<'gc> Context3DObject<'gc> {
             .unwrap()
             .process_command(
                 Context3DCommand::UploadShaders {
-                    vertex_shader: program.vertex_shader_handle(),
+                    module: program.shader_module_handle(),
                     vertex_shader_agal,
-                    fragment_shader: program.fragment_shader_handle(),
                     fragment_shader_agal,
                 },
                 activation.context.gc_context,
@@ -263,15 +262,9 @@ impl<'gc> Context3DObject<'gc> {
         activation: &mut Activation<'_, 'gc>,
         program: Option<Program3DObject<'gc>>,
     ) {
-        let (vertex_shader, fragment_shader) = match program {
-            Some(program) => (
-                program.vertex_shader_handle(),
-                program.fragment_shader_handle(),
-            ),
-            None => (
-                GcCell::allocate(activation.context.gc_context, None),
-                GcCell::allocate(activation.context.gc_context, None),
-            ),
+        let module = match program {
+            Some(program) => program.shader_module_handle(),
+            None => GcCell::allocate(activation.context.gc_context, None),
         };
 
         self.0
@@ -280,10 +273,7 @@ impl<'gc> Context3DObject<'gc> {
             .as_mut()
             .unwrap()
             .process_command(
-                Context3DCommand::SetShaders {
-                    vertex_shader,
-                    fragment_shader,
-                },
+                Context3DCommand::SetShaders { module },
                 activation.context.gc_context,
             );
     }

core/src/avm2/object/program_3d_object.rs

@@ -33,8 +33,7 @@ impl<'gc> Program3DObject<'gc> {
             Program3DObjectData {
                 base,
                 context3d,
-                vertex_shader_handle: GcCell::allocate(activation.context.gc_context, None),
-                fragment_shader_handle: GcCell::allocate(activation.context.gc_context, None),
+                shader_module_handle: GcCell::allocate(activation.context.gc_context, None),
             },
         ))
         .into();
@@ -45,12 +44,8 @@ impl<'gc> Program3DObject<'gc> {
         Ok(this)
     }
 
-    pub fn vertex_shader_handle(&self) -> GcCell<'gc, Option<Rc<dyn ShaderModule>>> {
-        self.0.read().vertex_shader_handle
-    }
-
-    pub fn fragment_shader_handle(&self) -> GcCell<'gc, Option<Rc<dyn ShaderModule>>> {
-        self.0.read().fragment_shader_handle
+    pub fn shader_module_handle(&self) -> GcCell<'gc, Option<Rc<dyn ShaderModule>>> {
+        self.0.read().shader_module_handle
     }
 
     pub fn context3d(&self) -> Context3DObject<'gc> {
@@ -66,9 +61,7 @@ pub struct Program3DObjectData<'gc> {
 
     context3d: Context3DObject<'gc>,
 
-    vertex_shader_handle: GcCell<'gc, Option<Rc<dyn ShaderModule>>>,
-
-    fragment_shader_handle: GcCell<'gc, Option<Rc<dyn ShaderModule>>>,
+    shader_module_handle: GcCell<'gc, Option<Rc<dyn ShaderModule>>>,
 }
 
 impl<'gc> TObject<'gc> for Program3DObject<'gc> {

render/src/backend.rs

@@ -429,15 +429,13 @@ pub enum Context3DCommand<'a, 'gc> {
     },
 
     UploadShaders {
-        vertex_shader: GcCell<'gc, Option<Rc<dyn ShaderModule>>>,
+        module: GcCell<'gc, Option<Rc<dyn ShaderModule>>>,
         vertex_shader_agal: Vec<u8>,
-        fragment_shader: GcCell<'gc, Option<Rc<dyn ShaderModule>>>,
         fragment_shader_agal: Vec<u8>,
     },
 
     SetShaders {
-        vertex_shader: GcCell<'gc, Option<Rc<dyn ShaderModule>>>,
-        fragment_shader: GcCell<'gc, Option<Rc<dyn ShaderModule>>>,
+        module: GcCell<'gc, Option<Rc<dyn ShaderModule>>>,
     },
     SetProgramConstantsFromVector {
         program_type: ProgramType,