[msl-out] Replace per_stage_map option with per-entry-point_map

The existing `per_stage_map` field of MSL backend options specifies
resource binding maps that apply to all entry points of each stage type.
It is useful to have the ability to provide a separate binding index map
for each entry point, especially when the same shader module defines
multiple entry points of the same stage kind.

This patch replaces `per_stage_map` with a new `per_entry_point_map`
option where resources are keyed by the entry-point function name.

src/back/msl/mod.rs

@@ -27,10 +27,7 @@ holding the result.
 */
 
 use crate::{arena::Handle, proc::index, valid::ModuleInfo};
-use std::{
-    fmt::{Error as FmtError, Write},
-    ops,
-};
+use std::fmt::{Error as FmtError, Write};
 
 mod keywords;
 pub mod sampler;
@@ -69,7 +66,7 @@ pub type BindingMap = std::collections::BTreeMap<crate::ResourceBinding, BindTar
 #[cfg_attr(feature = "serialize", derive(serde::Serialize))]
 #[cfg_attr(feature = "deserialize", derive(serde::Deserialize))]
 #[cfg_attr(any(feature = "serialize", feature = "deserialize"), serde(default))]
-pub struct PerStageResources {
+pub struct EntryPointResources {
     pub resources: BindingMap,
 
     pub push_constant_buffer: Option<Slot>,
@@ -80,26 +77,7 @@ pub struct PerStageResources {
     pub sizes_buffer: Option<Slot>,
 }
 
-#[derive(Clone, Debug, Default, Hash, Eq, PartialEq)]
-#[cfg_attr(feature = "serialize", derive(serde::Serialize))]
-#[cfg_attr(feature = "deserialize", derive(serde::Deserialize))]
-#[cfg_attr(any(feature = "serialize", feature = "deserialize"), serde(default))]
-pub struct PerStageMap {
-    pub vs: PerStageResources,
-    pub fs: PerStageResources,
-    pub cs: PerStageResources,
-}
-
-impl ops::Index<crate::ShaderStage> for PerStageMap {
-    type Output = PerStageResources;
-    fn index(&self, stage: crate::ShaderStage) -> &PerStageResources {
-        match stage {
-            crate::ShaderStage::Vertex => &self.vs,
-            crate::ShaderStage::Fragment => &self.fs,
-            crate::ShaderStage::Compute => &self.cs,
-        }
-    }
-}
+pub type EntryPointResourceMap = std::collections::BTreeMap<String, EntryPointResources>;
 
 enum ResolvedBinding {
     BuiltIn(crate::BuiltIn),
@@ -198,8 +176,8 @@ enum LocationMode {
 pub struct Options {
     /// (Major, Minor) target version of the Metal Shading Language.
     pub lang_version: (u8, u8),
-    /// Map of per-stage resources to slots.
-    pub per_stage_map: PerStageMap,
+    /// Map of entry-point resources, indexed by entry point function name, to slots.
+    pub per_entry_point_map: EntryPointResourceMap,
     /// Samplers to be inlined into the code.
     pub inline_samplers: Vec<sampler::InlineSampler>,
     /// Make it possible to link different stages via SPIRV-Cross.
@@ -217,7 +195,7 @@ impl Default for Options {
     fn default() -> Self {
         Options {
             lang_version: (2, 0),
-            per_stage_map: PerStageMap::default(),
+            per_entry_point_map: EntryPointResourceMap::default(),
             inline_samplers: Vec::new(),
             spirv_cross_compatibility: false,
             fake_missing_bindings: true,
@@ -296,12 +274,26 @@ impl Options {
         }
     }
 
+    fn get_entry_point_resources(&self, ep: &crate::EntryPoint) -> Option<&EntryPointResources> {
+        self.per_entry_point_map.get(&ep.name)
+    }
+
+    fn get_resource_binding_target(
+        &self,
+        ep: &crate::EntryPoint,
+        res_binding: &crate::ResourceBinding,
+    ) -> Option<&BindTarget> {
+        self.get_entry_point_resources(ep)
+            .and_then(|res| res.resources.get(res_binding))
+    }
+
     fn resolve_resource_binding(
         &self,
-        stage: crate::ShaderStage,
+        ep: &crate::EntryPoint,
         res_binding: &crate::ResourceBinding,
     ) -> Result<ResolvedBinding, EntryPointError> {
-        match self.per_stage_map[stage].resources.get(res_binding) {
+        let target = self.get_resource_binding_target(ep, res_binding);
+        match target {
             Some(target) => Ok(ResolvedBinding::Resource(target.clone())),
             None if self.fake_missing_bindings => Ok(ResolvedBinding::User {
                 prefix: "fake",
@@ -312,15 +304,13 @@ impl Options {
         }
     }
 
-    const fn resolve_push_constants(
+    fn resolve_push_constants(
         &self,
-        stage: crate::ShaderStage,
+        ep: &crate::EntryPoint,
     ) -> Result<ResolvedBinding, EntryPointError> {
-        let slot = match stage {
-            crate::ShaderStage::Vertex => self.per_stage_map.vs.push_constant_buffer,
-            crate::ShaderStage::Fragment => self.per_stage_map.fs.push_constant_buffer,
-            crate::ShaderStage::Compute => self.per_stage_map.cs.push_constant_buffer,
-        };
+        let slot = self
+            .get_entry_point_resources(ep)
+            .and_then(|res| res.push_constant_buffer);
         match slot {
             Some(slot) => Ok(ResolvedBinding::Resource(BindTarget {
                 buffer: Some(slot),
@@ -340,9 +330,11 @@ impl Options {
 
     fn resolve_sizes_buffer(
         &self,
-        stage: crate::ShaderStage,
+        ep: &crate::EntryPoint,
     ) -> Result<ResolvedBinding, EntryPointError> {
-        let slot = self.per_stage_map[stage].sizes_buffer;
+        let slot = self
+            .get_entry_point_resources(ep)
+            .and_then(|res| res.sizes_buffer);
         match slot {
             Some(slot) => Ok(ResolvedBinding::Resource(BindTarget {
                 buffer: Some(slot),

src/back/msl/writer.rs

@@ -3368,7 +3368,8 @@ impl<W: Write> Writer<W> {
                                     break;
                                 }
                             };
-                            let good = match options.per_stage_map[ep.stage].resources.get(br) {
+                            let target = options.get_resource_binding_target(&ep, &br);
+                            let good = match target {
                                 Some(target) => {
                                     let binding_ty = match module.types[var.ty].inner {
                                         crate::TypeInner::BindingArray { base, .. } => {
@@ -3393,7 +3394,7 @@ impl<W: Write> Writer<W> {
                             }
                         }
                         crate::AddressSpace::PushConstant => {
-                            if let Err(e) = options.resolve_push_constants(ep.stage) {
+                            if let Err(e) = options.resolve_push_constants(ep) {
                                 ep_error = Some(e);
                                 break;
                             }
@@ -3404,7 +3405,7 @@ impl<W: Write> Writer<W> {
                     }
                 }
                 if supports_array_length {
-                    if let Err(err) = options.resolve_sizes_buffer(ep.stage) {
+                    if let Err(err) = options.resolve_sizes_buffer(ep) {
                         ep_error = Some(err);
                     }
                 }
@@ -3673,15 +3674,13 @@ impl<W: Write> Writer<W> {
                 }
                 // the resolves have already been checked for `!fake_missing_bindings` case
                 let resolved = match var.space {
-                    crate::AddressSpace::PushConstant => {
-                        options.resolve_push_constants(ep.stage).ok()
-                    }
+                    crate::AddressSpace::PushConstant => options.resolve_push_constants(ep).ok(),
                     crate::AddressSpace::WorkGroup => None,
                     crate::AddressSpace::Storage { .. } if options.lang_version < (2, 0) => {
                         return Err(Error::UnsupportedAddressSpace(var.space))
                     }
                     _ => options
-                        .resolve_resource_binding(ep.stage, var.binding.as_ref().unwrap())
+                        .resolve_resource_binding(ep, var.binding.as_ref().unwrap())
                         .ok(),
                 };
                 if let Some(ref resolved) = resolved {
@@ -3726,7 +3725,7 @@ impl<W: Write> Writer<W> {
             // passed as a final struct-typed argument.
             if supports_array_length {
                 // this is checked earlier
-                let resolved = options.resolve_sizes_buffer(ep.stage).unwrap();
+                let resolved = options.resolve_sizes_buffer(ep).unwrap();
                 let separator = if module.global_variables.is_empty() {
                     ' '
                 } else {
@@ -3786,7 +3785,7 @@ impl<W: Write> Writer<W> {
                     };
                 } else if let Some(ref binding) = var.binding {
                     // write an inline sampler
-                    let resolved = options.resolve_resource_binding(ep.stage, binding).unwrap();
+                    let resolved = options.resolve_resource_binding(ep, binding).unwrap();
                     if let Some(sampler) = resolved.as_inline_sampler(options) {
                         let name = &self.names[&NameKey::GlobalVariable(handle)];
                         writeln!(

tests/in/access.param.ron

@@ -6,8 +6,8 @@
 	),
 	msl: (
 		lang_version: (2, 0),
-		per_stage_map: (
-			vs: (
+		per_entry_point_map: {
+			"foo_vert": (
 				resources: {
 					(group: 0, binding: 0): (buffer: Some(0), mutable: false),
 					(group: 0, binding: 1): (buffer: Some(1), mutable: false),
@@ -16,20 +16,20 @@
 				},
 				sizes_buffer: Some(24),
 			),
-			fs: (
+			"foo_frag": (
 				resources: {
 					(group: 0, binding: 0): (buffer: Some(0), mutable: true),
 					(group: 0, binding: 2): (buffer: Some(2), mutable: true),
 				},
 				sizes_buffer: Some(24),
 			),
-			cs: (
+			"atomics": (
 				resources: {
 					(group: 0, binding: 0): (buffer: Some(0), mutable: true),
 				},
 				sizes_buffer: Some(24),
 			),
-		),
+		},
 		inline_samplers: [],
 		spirv_cross_compatibility: false,
 		fake_missing_bindings: false,

tests/in/binding-arrays.param.ron

@@ -19,14 +19,14 @@
 	),
 	msl: (
 		lang_version: (2, 0),
-		per_stage_map: (
-			fs: (
+		per_entry_point_map: {
+			"main": (
 				resources: {
 					(group: 0, binding: 0): (texture: Some(0), binding_array_size: Some(10), mutable: false),
 				},
 				sizes_buffer: None,
 			)
-		),
+		},
 		inline_samplers: [],
 		spirv_cross_compatibility: false,
 		fake_missing_bindings: true,

tests/in/bitcast.params.ron

@@ -1,13 +1,13 @@
 (
 	msl: (
 		lang_version: (1, 2),
-		per_stage_map: (
-			cs: (
+		per_entry_point_map: {
+			"main": (
 				resources: {
 				},
 				sizes_buffer: Some(0),
 			)
-		),
+		},
 		inline_samplers: [],
 		spirv_cross_compatibility: false,
 		fake_missing_bindings: false,

tests/in/bits.param.ron

@@ -1,13 +1,13 @@
 (
 	msl: (
 		lang_version: (1, 2),
-		per_stage_map: (
-			cs: (
+		per_entry_point_map: {
+			"main": (
 				resources: {
 				},
 				sizes_buffer: Some(0),
 			)
-		),
+		},
 		inline_samplers: [],
 		spirv_cross_compatibility: false,
 		fake_missing_bindings: false,

tests/in/boids.param.ron

@@ -6,16 +6,16 @@
 	),
 	msl: (
 		lang_version: (2, 0),
-		per_stage_map: (
-			cs: (
+		per_entry_point_map: {
+			"main": (
 				resources: {
 					(group: 0, binding: 0): (buffer: Some(0), mutable: false),
 					(group: 0, binding: 1): (buffer: Some(1), mutable: true),
 					(group: 0, binding: 2): (buffer: Some(2), mutable: true),
 				},
 				sizes_buffer: Some(3),
 			)
-		),
+		},
 		inline_samplers: [],
 		spirv_cross_compatibility: false,
 		fake_missing_bindings: false,

tests/in/extra.param.ron

@@ -5,11 +5,11 @@
 	),
 	msl: (
 		lang_version: (2, 2),
-		per_stage_map: (
-			fs: (
+		per_entry_point_map: {
+			"main": (
 				push_constant_buffer: Some(1),
 			),
-		),
+		},
 		inline_samplers: [],
 		spirv_cross_compatibility: false,
 		fake_missing_bindings: false,

tests/in/interface.param.ron

@@ -19,7 +19,7 @@
 	),
 	msl: (
 		lang_version: (2, 1),
-		per_stage_map: (),
+		per_entry_point_map: {},
 		inline_samplers: [],
 		spirv_cross_compatibility: false,
 		fake_missing_bindings: false,

tests/in/padding.param.ron

@@ -6,15 +6,15 @@
 	),
 	msl: (
 		lang_version: (2, 0),
-		per_stage_map: (
-			vs: (
+		per_entry_point_map: {
+			"vertex": (
 				resources: {
 					(group: 0, binding: 0): (buffer: Some(0), mutable: false),
                     (group: 0, binding: 1): (buffer: Some(1), mutable: false),
                     (group: 0, binding: 2): (buffer: Some(2), mutable: false),
 				},
 			),
-		),
+		},
 		inline_samplers: [],
 		spirv_cross_compatibility: false,
 		fake_missing_bindings: false,