Add exact_entrypoint_interface flag to shader! (Fixes #1556) (#1559)

* add `exact_entrypoint_interface` flag to vulkano-shaders

Signed-off-by: Arc-blroth <45273859+Arc-blroth@users.noreply.github.com>

* cargo fmt

Signed-off-by: Arc-blroth <45273859+Arc-blroth@users.noreply.github.com>

* oops

Signed-off-by: Arc-blroth <45273859+Arc-blroth@users.noreply.github.com>

CHANGELOG_VULKANO.md

@@ -37,6 +37,8 @@
   - Traits that no longer make sense in this context have been removed: `FormatDesc`, the `Possible*FormatDesc` traits, `StrongStorage`.
   - In types that had a type parameter for the format type, it has been removed.
   - `AcceptsPixels` has been converted to `Pixel`, which is implemented on the pixel type rather than on the format type.
+- **Breaking** `shader!` will generate descriptor information for all variables declared in the shader module, even if they are not used. *This reverts the default behavior from the last release.*
+  - **Breaking** Added the `exact_entrypoint_interface` option to `shader!` to force vulkano to only generate descriptor information for variables that are used. (the default behavior from the last release)
 - Added two methods to `Format`: `planes` to query the number of planes in the format, and `aspects` to query what aspects an image of this type has.
 - The deprecated `cause` trait function on Vulkano error types is replaced with `source`.
 - Fixed bug in descriptor array layers check when the image is a cubemap.

vulkano-shaders/src/codegen.rs

@@ -204,6 +204,7 @@ pub(super) fn reflect<'a, I>(
     spirv: &[u32],
     types_meta: TypesMeta,
     input_paths: I,
+    exact_entrypoint_interface: bool,
     dump: bool,
 ) -> Result<TokenStream, Error>
 where
@@ -263,8 +264,12 @@ where
     let mut entry_points_outside_impl: Vec<TokenStream> = vec![];
     for instruction in doc.instructions.iter() {
         if let &Instruction::EntryPoint { .. } = instruction {
-            let (outside, entry_point, descriptor_sets) =
-                entry_point::write_entry_point(&doc, instruction, &types_meta);
+            let (outside, entry_point, descriptor_sets) = entry_point::write_entry_point(
+                &doc,
+                instruction,
+                &types_meta,
+                exact_entrypoint_interface,
+            );
             entry_points_inside_impl.push(entry_point);
             entry_points_outside_impl.push(outside);
             entry_points_outside_impl.push(descriptor_sets);

vulkano-shaders/src/descriptor_sets.rs

@@ -31,11 +31,12 @@ pub(super) fn write_descriptor_sets(
     entrypoint_id: u32,
     interface: &[u32],
     types_meta: &TypesMeta,
+    exact_entrypoint_interface: bool,
 ) -> TokenStream {
     // TODO: somewhat implemented correctly
 
     // Finding all the descriptors.
-    let descriptors = find_descriptors(doc, entrypoint_id, interface);
+    let descriptors = find_descriptors(doc, entrypoint_id, interface, exact_entrypoint_interface);
 
     // Looping to find all the push constant structs.
     let mut push_constants_size = 0;
@@ -138,14 +139,19 @@ pub(super) fn write_descriptor_sets(
     }
 }
 
-fn find_descriptors(doc: &Spirv, entrypoint_id: u32, interface: &[u32]) -> Vec<Descriptor> {
+fn find_descriptors(
+    doc: &Spirv,
+    entrypoint_id: u32,
+    interface: &[u32],
+    exact: bool,
+) -> Vec<Descriptor> {
     let mut descriptors = Vec::new();
 
     // For SPIR-V 1.4+, the entrypoint interface can specify variables of all storage classes,
     // and most tools will put all used variables in the entrypoint interface. However,
     // SPIR-V 1.0-1.3 do not specify variables other than Input/Output ones in the interface,
     // and instead the function itself must be inspected.
-    let variables = {
+    let variables = if exact {
         let mut found_variables: HashSet<u32> = interface.iter().cloned().collect();
         let mut inspected_functions: HashSet<u32> = HashSet::new();
         find_variables_in_function(
@@ -154,14 +160,16 @@ fn find_descriptors(doc: &Spirv, entrypoint_id: u32, interface: &[u32]) -> Vec<D
             &mut inspected_functions,
             &mut found_variables,
         );
-        found_variables
+        Some(found_variables)
+    } else {
+        None
     };
 
     // Looping to find all the interface elements that have the `DescriptorSet` decoration.
     for set_decoration in doc.get_decorations(Decoration::DecorationDescriptorSet) {
         let variable_id = set_decoration.target_id;
 
-        if !variables.contains(&variable_id) {
+        if exact && !variables.as_ref().unwrap().contains(&variable_id) {
             continue;
         }
 
@@ -650,7 +658,7 @@ mod tests {
                 id, ref interface, ..
             } = instruction
             {
-                descriptors.push(find_descriptors(&doc, id, interface));
+                descriptors.push(find_descriptors(&doc, id, interface, true));
             }
         }
 
@@ -724,7 +732,7 @@ mod tests {
                 id, ref interface, ..
             } = instruction
             {
-                let descriptors = find_descriptors(&doc, id, interface);
+                let descriptors = find_descriptors(&doc, id, interface, true);
                 let mut bindings = Vec::new();
                 for d in descriptors {
                     bindings.push((d.set, d.binding));

vulkano-shaders/src/entry_point.rs

@@ -19,6 +19,7 @@ pub(super) fn write_entry_point(
     doc: &Spirv,
     instruction: &Instruction,
     types_meta: &TypesMeta,
+    exact_entrypoint_interface: bool,
 ) -> (TokenStream, TokenStream, TokenStream) {
     let (execution, id, ep_name, interface) = match instruction {
         &Instruction::EntryPoint {
@@ -67,6 +68,7 @@ pub(super) fn write_entry_point(
         id,
         interface,
         &types_meta,
+        exact_entrypoint_interface,
     );
 
     let spec_consts_struct = if crate::spec_consts::has_specialization_constants(doc) {

vulkano-shaders/src/lib.rs

@@ -134,6 +134,8 @@
 //! Provides the path to precompiled SPIR-V bytecode, relative to `Cargo.toml`.
 //! Cannot be used in conjunction with the `src` or `path` field.
 //! This allows using shaders compiled through a separate build system.
+//! **Note**: If your shader contains multiple entrypoints with different
+//! descriptor sets, you may also need to enable `exact_entrypoint_interface`.
 //!
 //! ## `include: ["...", "...", ..., "..."]`
 //!
@@ -172,6 +174,19 @@
 //! final output of generated code the user can also use `dump` macro
 //! option(see below).
 //!
+//! ## `exact_entrypoint_interface: true`
+//!
+//! By default, the macro assumes that all resources (Uniforms, Storage Buffers,
+//! Images, Samplers, etc) need to be bound into a descriptor set, even if they are
+//! not used in the shader code. However, shaders with multiple entrypoints may have
+//! conflicting descriptor sets for each entrypoint. Enabling this option will force
+//! the macro to only generate descriptor information for resources that are used
+//! in each entrypoint.
+//!
+//! The macro determines which resources are used by looking at each entrypoint's
+//! interface and bytecode. See [`src/descriptor_sets.rs`][descriptor_sets]
+//! for the exact logic.
+//!
 //! ## `dump: true`
 //!
 //! The crate fails to compile but prints the generated rust code to stdout.
@@ -186,6 +201,7 @@
 //! [PipelineLayoutDesc]: https://docs.rs/vulkano/*/vulkano/descriptor/pipeline_layout/trait.PipelineLayoutDesc.html
 //! [SpecializationConstants]: https://docs.rs/vulkano/*/vulkano/pipeline/shader/trait.SpecializationConstants.html
 //! [pipeline]: https://docs.rs/vulkano/*/vulkano/pipeline/index.html
+//! [descriptor_sets]: https://github.com/vulkano-rs/vulkano/blob/master/vulkano-shaders/src/descriptor_sets.rs#L142
 
 #![doc(html_logo_url = "https://raw.githubusercontent.com/vulkano-rs/vulkano/master/logo.png")]
 #![recursion_limit = "1024"]
@@ -276,6 +292,7 @@ struct MacroInput {
     include_directories: Vec<String>,
     macro_defines: Vec<(String, String)>,
     types_meta: TypesMeta,
+    exact_entrypoint_interface: bool,
     dump: bool,
 }
 
@@ -287,6 +304,7 @@ impl Parse for MacroInput {
         let mut include_directories = Vec::new();
         let mut macro_defines = Vec::new();
         let mut types_meta = None;
+        let mut exact_entrypoint_interface = None;
 
         while !input.is_empty() {
             let name: Ident = input.parse()?;
@@ -504,6 +522,13 @@ impl Parse for MacroInput {
 
                     types_meta = Some(meta);
                 }
+                "exact_entrypoint_interface" => {
+                    if exact_entrypoint_interface.is_some() {
+                        panic!("Only one `dump` can be defined")
+                    }
+                    let lit: LitBool = input.parse()?;
+                    exact_entrypoint_interface = Some(lit.value);
+                }
                 "dump" => {
                     if dump.is_some() {
                         panic!("Only one `dump` can be defined")
@@ -538,6 +563,7 @@ impl Parse for MacroInput {
             dump,
             macro_defines,
             types_meta: types_meta.unwrap_or_else(|| TypesMeta::default()),
+            exact_entrypoint_interface: exact_entrypoint_interface.unwrap_or(false),
         })
     }
 }
@@ -575,6 +601,7 @@ pub fn shader(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
             unsafe { from_raw_parts(bytes.as_slice().as_ptr() as *const u32, bytes.len() / 4) },
             input.types_meta,
             empty(),
+            input.exact_entrypoint_interface,
             input.dump,
         )
         .unwrap()
@@ -631,6 +658,7 @@ pub fn shader(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
             content.as_binary(),
             input.types_meta,
             input_paths,
+            input.exact_entrypoint_interface,
             input.dump,
         )
         .unwrap()