Refactor attributes and add descriptor_set/binding (#145)

* Move entry declarations to their own file

Also clean up attribute parsing (and make it allow multiple arguments in
the process)

* Add descriptor_set and binding attributes

* clippy fix

* Fix test

* Reserve descriptor_set 0 for future use

* Add book page on attributes

docs/src/SUMMARY.md

@@ -1,3 +1,4 @@
 # Summary
 
 - [Introduction](./introduction.md)
+- [Attribute syntax](./attributes.md)

docs/src/attributes.md

@@ -0,0 +1,48 @@
+# Attribute syntax
+
+rust-gpu introduces a number of SPIR-V related attributes to express behavior specific to SPIR-V not exposed in the base rust language.
+
+There are a few different categories of attributes:
+
+## Entry points
+
+When declaring an entry point to your shader, SPIR-V needs to know what type of function it is. For example, it could be a fragment shader, or vertex shader. Specifying this attribute is also the way rust-gpu knows that you would like to export a function as an entry point, no other functions are exported.
+
+Example:
+
+```rust
+#[spirv(fragment)]
+fn main() { }
+```
+
+Common values are `#[spirv(fragment)]` and `#[spirv(vertex)]`. A list of all supported names can be found in [spirv_headers](https://docs.rs/spirv_headers/1.5.0/spirv_headers/enum.ExecutionModel.html) - convert the enum name to snake_case for the rust-gpu attribute name.
+
+## Builtins
+
+When declaring inputs and outputs, sometimes you want to declare it as a "builtin". This means many things, but one example is `gl_Position` from glsl - the GPU assigns inherent meaning to the variable and uses it for placing the vertex in clip space. The equivalent in rust-gpu is called `position`.
+
+Example:
+
+```rust:
+#[spirv(fragment)]
+fn main(
+    #[spirv(position)] mut out_pos: Output<Vec4>,
+) { }
+```
+
+Common values are `#[spirv(position)]`, `#[spirv(vertex_id)]`, and many more. A list of all supported names can be found in [spirv_headers](https://docs.rs/spirv_headers/1.5.0/spirv_headers/enum.BuiltIn.html) - convert the enum name to snake_case for the rust-gpu attribute name.
+
+## Descriptor set and binding
+
+A SPIR-V shader must declare where uniform variables are located with explicit indices that match up with CPU-side code. This can be done with the `descriptor_set` and `binding` attributes. Note that `descriptor_set = 0` is reserved for future use, and cannot be used.
+
+Example:
+
+```rust:
+#[spirv(fragment)]
+fn main(
+    #[spirv(descriptor_set = 2, binding = 5)] mut var: Uniform<Vec4>,
+) { }
+```
+
+Both descriptor_set and binding take an integer argument that specifies the uniform's index.

examples/example-shader/src/lib.rs

@@ -194,7 +194,7 @@ pub fn fs(screen_pos: Vec2) -> Vec4 {
 }
 
 #[allow(unused_attributes)]
-#[spirv(entry = "fragment")]
+#[spirv(fragment)]
 pub fn main_fs(input: Input<Vec4>, mut output: Output<Vec4>) {
     let v = input.load();
     let color = fs(Vec2::new(v.0, v.1));
@@ -202,11 +202,11 @@ pub fn main_fs(input: Input<Vec4>, mut output: Output<Vec4>) {
 }
 
 #[allow(unused_attributes)]
-#[spirv(entry = "vertex")]
+#[spirv(vertex)]
 pub fn main_vs(
     in_pos: Input<Vec4>,
     _in_color: Input<Vec4>,
-    #[spirv(builtin = "position")] mut out_pos: Output<Vec4>,
+    #[spirv(position)] mut out_pos: Output<Vec4>,
     mut out_color: Output<Vec4>,
 ) {
     out_pos.store(in_pos.load());

rustc_codegen_spirv/src/abi.rs

@@ -3,7 +3,7 @@
 
 use crate::codegen_cx::CodegenCx;
 use crate::spirv_type::SpirvType;
-use crate::symbols::{parse_attr, SpirvAttribute};
+use crate::symbols::{parse_attrs, SpirvAttribute};
 use rspirv::spirv::{StorageClass, Word};
 use rustc_middle::bug;
 use rustc_middle::ty::layout::{FnAbiExt, TyAndLayout};
@@ -538,8 +538,8 @@ fn dig_scalar_pointee_adt<'tcx>(
 // TODO: Enforce this is only used in spirv-std.
 fn get_storage_class<'tcx>(cx: &CodegenCx<'tcx>, ty: TyAndLayout<'tcx>) -> Option<StorageClass> {
     if let TyKind::Adt(adt, _substs) = ty.ty.kind() {
-        for attr in cx.tcx.get_attrs(adt.did) {
-            if let Some(SpirvAttribute::StorageClass(storage_class)) = parse_attr(cx, attr) {
+        for attr in parse_attrs(cx, cx.tcx.get_attrs(adt.did)) {
+            if let SpirvAttribute::StorageClass(storage_class) = attr {
                 return Some(storage_class);
             }
         }

rustc_codegen_spirv/src/codegen_cx/declare.rs

@@ -2,14 +2,10 @@ use super::CodegenCx;
 use crate::abi::ConvSpirvType;
 use crate::builder_spirv::{SpirvConst, SpirvValue, SpirvValueExt};
 use crate::spirv_type::SpirvType;
-use crate::symbols::{parse_attr, SpirvAttribute};
-use rspirv::dr::Operand;
-use rspirv::spirv::{
-    Decoration, ExecutionMode, ExecutionModel, FunctionControl, LinkageType, StorageClass, Word,
-};
+use crate::symbols::{parse_attrs, SpirvAttribute};
+use rspirv::spirv::{FunctionControl, LinkageType, StorageClass, Word};
 use rustc_attr::InlineAttr;
 use rustc_codegen_ssa::traits::{PreDefineMethods, StaticMethods};
-use rustc_hir::Param;
 use rustc_middle::bug;
 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
 use rustc_middle::mir::mono::{Linkage, MonoItem, Visibility};
@@ -18,9 +14,7 @@ use rustc_middle::ty::{Instance, ParamEnv, Ty, TypeFoldable};
 use rustc_span::def_id::DefId;
 use rustc_span::Span;
 use rustc_target::abi::call::FnAbi;
-use rustc_target::abi::call::PassMode;
 use rustc_target::abi::{Align, LayoutOf};
-use std::collections::HashMap;
 
 fn attrs_to_spirv(attrs: &CodegenFnAttrs) -> FunctionControl {
     let mut control = FunctionControl::NONE;
@@ -156,194 +150,6 @@ impl<'tcx> CodegenCx<'tcx> {
         self.zombie_with_span(result.def, span, "Globals are not supported yet");
         result
     }
-
-    // Entry points declare their "interface" (all uniforms, inputs, outputs, etc.) as parameters. spir-v uses globals
-    // to declare the interface. So, we need to generate a lil stub for the "real" main that collects all those global
-    // variables and calls the user-defined main function.
-    fn shader_entry_stub(
-        &self,
-        entry_func: SpirvValue,
-        hir_params: &[Param<'_>],
-        name: String,
-        execution_model: ExecutionModel,
-    ) {
-        let void = SpirvType::Void.def(self);
-        let fn_void_void = SpirvType::Function {
-            return_type: void,
-            arguments: vec![],
-        }
-        .def(self);
-        let (entry_func_return, entry_func_args) = match self.lookup_type(entry_func.ty) {
-            SpirvType::Function {
-                return_type,
-                arguments,
-            } => (return_type, arguments),
-            other => self.tcx.sess.fatal(&format!(
-                "Invalid entry_stub type: {}",
-                other.debug(entry_func.ty, self)
-            )),
-        };
-        let mut emit = self.emit_global();
-        let mut decoration_locations = HashMap::new();
-        // Create OpVariables before OpFunction so they're global instead of local vars.
-        let arguments = entry_func_args
-            .iter()
-            .zip(hir_params)
-            .map(|(&arg, hir_param)| {
-                let storage_class = match self.lookup_type(arg) {
-                    SpirvType::Pointer { storage_class, .. } => storage_class,
-                    other => self.tcx.sess.fatal(&format!(
-                        "Invalid entry arg type {}",
-                        other.debug(arg, self)
-                    )),
-                };
-                let mut has_location = match storage_class {
-                    StorageClass::Input | StorageClass::Output | StorageClass::UniformConstant => {
-                        true
-                    }
-                    _ => false,
-                };
-                // Note: this *declares* the variable too.
-                let variable = emit.variable(arg, None, storage_class, None);
-                for attr in hir_param.attrs {
-                    if let Some(SpirvAttribute::Builtin(builtin)) = parse_attr(self, attr) {
-                        emit.decorate(
-                            variable,
-                            Decoration::BuiltIn,
-                            std::iter::once(Operand::BuiltIn(builtin)),
-                        );
-                        has_location = false;
-                    }
-                }
-                // Assign locations from left to right, incrementing each storage class
-                // individually.
-                // TODO: Is this right for UniformConstant? Do they share locations with
-                // input/outpus?
-                if has_location {
-                    let location = decoration_locations
-                        .entry(storage_class)
-                        .or_insert_with(|| 0);
-                    emit.decorate(
-                        variable,
-                        Decoration::Location,
-                        std::iter::once(Operand::LiteralInt32(*location)),
-                    );
-                    *location += 1;
-                }
-                variable
-            })
-            .collect::<Vec<_>>();
-        let fn_id = emit
-            .begin_function(void, None, FunctionControl::NONE, fn_void_void)
-            .unwrap();
-        emit.begin_block(None).unwrap();
-        emit.function_call(
-            entry_func_return,
-            None,
-            entry_func.def,
-            arguments.iter().copied(),
-        )
-        .unwrap();
-        emit.ret().unwrap();
-        emit.end_function().unwrap();
-
-        let interface = arguments;
-        emit.entry_point(execution_model, fn_id, name, interface);
-        if execution_model == ExecutionModel::Fragment {
-            // TODO: Make this configurable.
-            emit.execution_mode(fn_id, ExecutionMode::OriginUpperLeft, &[]);
-        }
-    }
-
-    // Kernel mode takes its interface as function parameters(??)
-    // OpEntryPoints cannot be OpLinkage, so write out a stub to call through.
-    fn kernel_entry_stub(
-        &self,
-        entry_func: SpirvValue,
-        name: String,
-        execution_model: ExecutionModel,
-    ) {
-        let (entry_func_return, entry_func_args) = match self.lookup_type(entry_func.ty) {
-            SpirvType::Function {
-                return_type,
-                arguments,
-            } => (return_type, arguments),
-            other => self.tcx.sess.fatal(&format!(
-                "Invalid kernel_entry_stub type: {}",
-                other.debug(entry_func.ty, self)
-            )),
-        };
-        let mut emit = self.emit_global();
-        let fn_id = emit
-            .begin_function(
-                entry_func_return,
-                None,
-                FunctionControl::NONE,
-                entry_func.ty,
-            )
-            .unwrap();
-        let arguments = entry_func_args
-            .iter()
-            .map(|&ty| emit.function_parameter(ty).unwrap())
-            .collect::<Vec<_>>();
-        emit.begin_block(None).unwrap();
-        let call_result = emit
-            .function_call(entry_func_return, None, entry_func.def, arguments)
-            .unwrap();
-        if self.lookup_type(entry_func_return) == SpirvType::Void {
-            emit.ret().unwrap();
-        } else {
-            emit.ret_value(call_result).unwrap();
-        }
-        emit.end_function().unwrap();
-
-        emit.entry_point(execution_model, fn_id, name, &[]);
-    }
-
-    fn entry_stub(
-        &self,
-        instance: &Instance<'_>,
-        fn_abi: &FnAbi<'_, Ty<'_>>,
-        entry_func: SpirvValue,
-        name: String,
-        execution_model: ExecutionModel,
-    ) {
-        let local_id = match instance.def_id().as_local() {
-            Some(id) => id,
-            None => {
-                self.tcx
-                    .sess
-                    .err(&format!("Cannot declare {} as an entry point", name));
-                return;
-            }
-        };
-        let fn_hir_id = self.tcx.hir().local_def_id_to_hir_id(local_id);
-        let body = self.tcx.hir().body(self.tcx.hir().body_owned_by(fn_hir_id));
-        for (abi, arg) in fn_abi.args.iter().zip(body.params) {
-            if let PassMode::Direct(_) = abi.mode {
-            } else {
-                self.tcx.sess.span_err(
-                    arg.span,
-                    &format!("PassMode {:?} invalid for entry point parameter", abi.mode),
-                )
-            }
-        }
-        if let PassMode::Ignore = fn_abi.ret.mode {
-        } else {
-            self.tcx.sess.span_err(
-                self.tcx.hir().span(fn_hir_id),
-                &format!(
-                    "PassMode {:?} invalid for entry point return type",
-                    fn_abi.ret.mode
-                ),
-            )
-        }
-        if execution_model == ExecutionModel::Kernel {
-            self.kernel_entry_stub(entry_func, name, execution_model);
-        } else {
-            self.shader_entry_stub(entry_func, body.params, name, execution_model);
-        }
-    }
 }
 
 impl<'tcx> PreDefineMethods<'tcx> for CodegenCx<'tcx> {
@@ -403,16 +209,16 @@ impl<'tcx> PreDefineMethods<'tcx> for CodegenCx<'tcx> {
         let declared =
             self.declare_fn_ext(symbol_name, Some(&human_name), linkage2, spv_attrs, &fn_abi);
 
-        for attr in self.tcx.get_attrs(instance.def_id()) {
-            match parse_attr(self, attr) {
-                Some(SpirvAttribute::Entry(execution_model)) => self.entry_stub(
+        for attr in parse_attrs(self, self.tcx.get_attrs(instance.def_id())) {
+            match attr {
+                SpirvAttribute::Entry(execution_model) => self.entry_stub(
                     &instance,
                     &fn_abi,
                     declared,
                     human_name.clone(),
                     execution_model,
                 ),
-                Some(SpirvAttribute::ReallyUnsafeIgnoreBitcasts) => {
+                SpirvAttribute::ReallyUnsafeIgnoreBitcasts => {
                     self.really_unsafe_ignore_bitcasts
                         .borrow_mut()
                         .insert(declared);

rustc_codegen_spirv/src/codegen_cx/entry.rs

@@ -0,0 +1,245 @@
+use super::CodegenCx;
+use crate::builder_spirv::SpirvValue;
+use crate::spirv_type::SpirvType;
+use crate::symbols::{parse_attrs, SpirvAttribute};
+use rspirv::dr::Operand;
+use rspirv::spirv::{
+    Decoration, ExecutionMode, ExecutionModel, FunctionControl, StorageClass, Word,
+};
+use rustc_hir::Param;
+use rustc_middle::ty::{Instance, Ty};
+use rustc_target::abi::call::{FnAbi, PassMode};
+use std::collections::HashMap;
+
+impl<'tcx> CodegenCx<'tcx> {
+    // Entry points declare their "interface" (all uniforms, inputs, outputs, etc.) as parameters.
+    // spir-v uses globals to declare the interface. So, we need to generate a lil stub for the
+    // "real" main that collects all those global variables and calls the user-defined main
+    // function.
+    pub fn entry_stub(
+        &self,
+        instance: &Instance<'_>,
+        fn_abi: &FnAbi<'_, Ty<'_>>,
+        entry_func: SpirvValue,
+        name: String,
+        execution_model: ExecutionModel,
+    ) {
+        let local_id = match instance.def_id().as_local() {
+            Some(id) => id,
+            None => {
+                self.tcx
+                    .sess
+                    .err(&format!("Cannot declare {} as an entry point", name));
+                return;
+            }
+        };
+        let fn_hir_id = self.tcx.hir().local_def_id_to_hir_id(local_id);
+        let body = self.tcx.hir().body(self.tcx.hir().body_owned_by(fn_hir_id));
+        for (abi, arg) in fn_abi.args.iter().zip(body.params) {
+            if let PassMode::Direct(_) = abi.mode {
+            } else {
+                self.tcx.sess.span_err(
+                    arg.span,
+                    &format!("PassMode {:?} invalid for entry point parameter", abi.mode),
+                )
+            }
+        }
+        if let PassMode::Ignore = fn_abi.ret.mode {
+        } else {
+            self.tcx.sess.span_err(
+                self.tcx.hir().span(fn_hir_id),
+                &format!(
+                    "PassMode {:?} invalid for entry point return type",
+                    fn_abi.ret.mode
+                ),
+            )
+        }
+        if execution_model == ExecutionModel::Kernel {
+            self.kernel_entry_stub(entry_func, name, execution_model);
+        } else {
+            self.shader_entry_stub(entry_func, body.params, name, execution_model);
+        }
+    }
+
+    fn shader_entry_stub(
+        &self,
+        entry_func: SpirvValue,
+        hir_params: &[Param<'tcx>],
+        name: String,
+        execution_model: ExecutionModel,
+    ) {
+        let void = SpirvType::Void.def(self);
+        let fn_void_void = SpirvType::Function {
+            return_type: void,
+            arguments: vec![],
+        }
+        .def(self);
+        let (entry_func_return, entry_func_args) = match self.lookup_type(entry_func.ty) {
+            SpirvType::Function {
+                return_type,
+                arguments,
+            } => (return_type, arguments),
+            other => self.tcx.sess.fatal(&format!(
+                "Invalid entry_stub type: {}",
+                other.debug(entry_func.ty, self)
+            )),
+        };
+        let mut decoration_locations = HashMap::new();
+        // Create OpVariables before OpFunction so they're global instead of local vars.
+        let arguments = entry_func_args
+            .iter()
+            .zip(hir_params)
+            .map(|(&arg, hir_param)| {
+                self.declare_parameter(arg, hir_param, &mut decoration_locations)
+            })
+            .collect::<Vec<_>>();
+        let mut emit = self.emit_global();
+        let fn_id = emit
+            .begin_function(void, None, FunctionControl::NONE, fn_void_void)
+            .unwrap();
+        emit.begin_block(None).unwrap();
+        emit.function_call(
+            entry_func_return,
+            None,
+            entry_func.def,
+            arguments.iter().map(|&(a, _)| a),
+        )
+        .unwrap();
+        emit.ret().unwrap();
+        emit.end_function().unwrap();
+
+        let interface: Vec<_> = if emit.version().unwrap() > (1, 3) {
+            // SPIR-V >= v1.4 includes all OpVariables in the interface.
+            arguments.into_iter().map(|(a, _)| a).collect()
+        } else {
+            // SPIR-V <= v1.3 only includes Input and Output in the interface.
+            arguments
+                .into_iter()
+                .filter(|&(_, s)| s == StorageClass::Input || s == StorageClass::Output)
+                .map(|(a, _)| a)
+                .collect()
+        };
+        emit.entry_point(execution_model, fn_id, name, interface);
+        if execution_model == ExecutionModel::Fragment {
+            // TODO: Make this configurable.
+            emit.execution_mode(fn_id, ExecutionMode::OriginUpperLeft, &[]);
+        }
+    }
+
+    fn declare_parameter(
+        &self,
+        arg: Word,
+        hir_param: &Param<'tcx>,
+        decoration_locations: &mut HashMap<StorageClass, u32>,
+    ) -> (Word, StorageClass) {
+        let storage_class = match self.lookup_type(arg) {
+            SpirvType::Pointer { storage_class, .. } => storage_class,
+            other => self.tcx.sess.fatal(&format!(
+                "Invalid entry arg type {}",
+                other.debug(arg, self)
+            )),
+        };
+        let mut has_location = matches!(
+            storage_class,
+            StorageClass::Input | StorageClass::Output | StorageClass::UniformConstant
+        );
+        // Note: this *declares* the variable too.
+        let variable = self.emit_global().variable(arg, None, storage_class, None);
+        for attr in parse_attrs(self, hir_param.attrs) {
+            match attr {
+                SpirvAttribute::Builtin(builtin) => {
+                    self.emit_global().decorate(
+                        variable,
+                        Decoration::BuiltIn,
+                        std::iter::once(Operand::BuiltIn(builtin)),
+                    );
+                    has_location = false;
+                }
+                SpirvAttribute::DescriptorSet(index) => {
+                    self.emit_global().decorate(
+                        variable,
+                        Decoration::DescriptorSet,
+                        std::iter::once(Operand::LiteralInt32(index)),
+                    );
+                    has_location = false;
+                }
+                SpirvAttribute::Binding(index) => {
+                    if index == 0 {
+                        self.tcx.sess.span_err(
+                            hir_param.span,
+                            "descriptor_set 0 is reserved for internal / future use",
+                        );
+                    }
+                    self.emit_global().decorate(
+                        variable,
+                        Decoration::Binding,
+                        std::iter::once(Operand::LiteralInt32(index)),
+                    );
+                    has_location = false;
+                }
+                _ => {}
+            }
+        }
+        // Assign locations from left to right, incrementing each storage class
+        // individually.
+        // TODO: Is this right for UniformConstant? Do they share locations with
+        // input/outpus?
+        if has_location {
+            let location = decoration_locations
+                .entry(storage_class)
+                .or_insert_with(|| 0);
+            self.emit_global().decorate(
+                variable,
+                Decoration::Location,
+                std::iter::once(Operand::LiteralInt32(*location)),
+            );
+            *location += 1;
+        }
+        (variable, storage_class)
+    }
+
+    // Kernel mode takes its interface as function parameters(??)
+    // OpEntryPoints cannot be OpLinkage, so write out a stub to call through.
+    fn kernel_entry_stub(
+        &self,
+        entry_func: SpirvValue,
+        name: String,
+        execution_model: ExecutionModel,
+    ) {
+        let (entry_func_return, entry_func_args) = match self.lookup_type(entry_func.ty) {
+            SpirvType::Function {
+                return_type,
+                arguments,
+            } => (return_type, arguments),
+            other => self.tcx.sess.fatal(&format!(
+                "Invalid kernel_entry_stub type: {}",
+                other.debug(entry_func.ty, self)
+            )),
+        };
+        let mut emit = self.emit_global();
+        let fn_id = emit
+            .begin_function(
+                entry_func_return,
+                None,
+                FunctionControl::NONE,
+                entry_func.ty,
+            )
+            .unwrap();
+        let arguments = entry_func_args
+            .iter()
+            .map(|&ty| emit.function_parameter(ty).unwrap())
+            .collect::<Vec<_>>();
+        emit.begin_block(None).unwrap();
+        let call_result = emit
+            .function_call(entry_func_return, None, entry_func.def, arguments)
+            .unwrap();
+        if self.lookup_type(entry_func_return) == SpirvType::Void {
+            emit.ret().unwrap();
+        } else {
+            emit.ret_value(call_result).unwrap();
+        }
+        emit.end_function().unwrap();
+
+        emit.entry_point(execution_model, fn_id, name, &[]);
+    }
+}

rustc_codegen_spirv/src/codegen_cx/mod.rs

@@ -1,5 +1,6 @@
 mod constant;
 mod declare;
+mod entry;
 mod type_;
 
 use crate::builder::ExtInst;

rustc_codegen_spirv/src/symbols.rs

@@ -1,6 +1,6 @@
 use crate::codegen_cx::CodegenCx;
 use rspirv::spirv::{BuiltIn, ExecutionModel, StorageClass};
-use rustc_ast::ast::{AttrKind, Attribute};
+use rustc_ast::ast::{AttrKind, Attribute, Lit, LitIntType, LitKind, NestedMetaItem};
 use rustc_span::symbol::Symbol;
 use std::collections::HashMap;
 
@@ -13,19 +13,14 @@ pub struct Symbols {
     pub spirv: Symbol,
     pub spirv_std: Symbol,
     pub kernel: Symbol,
-    pub builtin: Symbol,
-    pub storage_class: Symbol,
-    pub entry: Symbol,
-    pub really_unsafe_ignore_bitcasts: Symbol,
-
-    builtins: HashMap<Symbol, BuiltIn>,
-    storage_classes: HashMap<Symbol, StorageClass>,
-    execution_models: HashMap<Symbol, ExecutionModel>,
+    descriptor_set: Symbol,
+    binding: Symbol,
+    attributes: HashMap<Symbol, SpirvAttribute>,
 }
 
-fn make_builtins() -> HashMap<Symbol, BuiltIn> {
+const BUILTINS: &[(&str, BuiltIn)] = {
     use BuiltIn::*;
-    [
+    &[
         ("position", Position),
         ("point_size", PointSize),
         ("clip_distance", ClipDistance),
@@ -126,15 +121,12 @@ fn make_builtins() -> HashMap<Symbol, BuiltIn> {
         ("warp_id_nv", WarpIDNV),
         ("SMIDNV", SMIDNV),
     ]
-    .iter()
-    .map(|&(a, b)| (Symbol::intern(a), b))
-    .collect()
-}
+};
 
-fn make_storage_classes() -> HashMap<Symbol, StorageClass> {
+const STORAGE_CLASSES: &[(&str, StorageClass)] = {
     use StorageClass::*;
     // make sure these strings stay synced with spirv-std's pointer types
-    [
+    &[
         ("uniform_constant", UniformConstant),
         ("input", Input),
         ("uniform", Uniform),
@@ -165,14 +157,11 @@ fn make_storage_classes() -> HashMap<Symbol, StorageClass> {
         ),
         ("physical_storage_buffer", PhysicalStorageBuffer),
     ]
-    .iter()
-    .map(|&(a, b)| (Symbol::intern(a), b))
-    .collect()
-}
+};
 
-fn make_execution_models() -> HashMap<Symbol, ExecutionModel> {
+const EXECUTION_MODELS: &[(&str, ExecutionModel)] = {
     use ExecutionModel::*;
-    [
+    &[
         ("vertex", Vertex),
         ("tessellation_control", TessellationControl),
         ("tessellation_evaluation", TessellationEvaluation),
@@ -189,137 +178,143 @@ fn make_execution_models() -> HashMap<Symbol, ExecutionModel> {
         ("miss_nv", MissNV),
         ("callable_nv", CallableNV),
     ]
-    .iter()
-    .map(|&(a, b)| (Symbol::intern(a), b))
-    .collect()
-}
+};
 
 impl Symbols {
     pub fn new() -> Self {
+        let builtins = BUILTINS
+            .iter()
+            .map(|&(a, b)| (a, SpirvAttribute::Builtin(b)));
+        let storage_classes = STORAGE_CLASSES
+            .iter()
+            .map(|&(a, b)| (a, SpirvAttribute::StorageClass(b)));
+        let execution_models = EXECUTION_MODELS
+            .iter()
+            .map(|&(a, b)| (a, SpirvAttribute::Entry(b)));
+        let custom = std::iter::once((
+            "really_unsafe_ignore_bitcasts",
+            SpirvAttribute::ReallyUnsafeIgnoreBitcasts,
+        ));
+        let attributes_iter = builtins
+            .chain(storage_classes)
+            .chain(execution_models)
+            .chain(custom)
+            .map(|(a, b)| (Symbol::intern(a), b));
+        let mut attributes = HashMap::new();
+        for attr in attributes_iter {
+            let old = attributes.insert(attr.0, attr.1);
+            // `.collect()` into a HashMap does not error on duplicates, so manually write out the
+            // loop here to error on duplicates.
+            assert!(old.is_none());
+        }
         Self {
             spirv: Symbol::intern("spirv"),
             spirv_std: Symbol::intern("spirv_std"),
             kernel: Symbol::intern("kernel"),
-            builtin: Symbol::intern("builtin"),
-            storage_class: Symbol::intern("storage_class"),
-            entry: Symbol::intern("entry"),
-            really_unsafe_ignore_bitcasts: Symbol::intern("really_unsafe_ignore_bitcasts"),
-            builtins: make_builtins(),
-            storage_classes: make_storage_classes(),
-            execution_models: make_execution_models(),
+            descriptor_set: Symbol::intern("descriptor_set"),
+            binding: Symbol::intern("binding"),
+            attributes,
         }
     }
-
-    pub fn symbol_to_builtin(&self, sym: Symbol) -> Option<BuiltIn> {
-        self.builtins.get(&sym).copied()
-    }
-
-    pub fn symbol_to_storageclass(&self, sym: Symbol) -> Option<StorageClass> {
-        self.storage_classes.get(&sym).copied()
-    }
-
-    pub fn symbol_to_execution_model(&self, sym: Symbol) -> Option<ExecutionModel> {
-        self.execution_models.get(&sym).copied()
-    }
 }
 
+#[derive(Debug, Clone)]
 pub enum SpirvAttribute {
     Builtin(BuiltIn),
     StorageClass(StorageClass),
     Entry(ExecutionModel),
+    DescriptorSet(u32),
+    Binding(u32),
     ReallyUnsafeIgnoreBitcasts,
 }
 
-// Note that we could mark the attr as used via cx.tcx.sess.mark_attr_used(attr), but unused reporting already happens
-// even before we get here :(
-/// Returns None if this attribute is not a spirv attribute, or if it's malformed (and an error is reported).
-pub fn parse_attr<'tcx>(cx: &CodegenCx<'tcx>, attr: &Attribute) -> Option<SpirvAttribute> {
-    // Example attributes that we parse here:
-    // #[spirv(storage_class = "uniform")]
-    // #[spirv(entry = "kernel")]
-    let is_spirv = match attr.kind {
-        AttrKind::Normal(ref item) => {
-            // TODO: We ignore the rest of the path. Is this right?
-            let last = item.path.segments.last();
-            last.map_or(false, |seg| seg.ident.name == cx.sym.spirv)
-        }
-        AttrKind::DocComment(..) => false,
-    };
-    if !is_spirv {
-        return None;
-    }
-    let args = if let Some(args) = attr.meta_item_list() {
-        args
-    } else {
-        cx.tcx
-            .sess
-            .span_err(attr.span, "#[spirv(..)] attribute must have one argument");
-        return None;
-    };
-    if args.len() != 1 {
-        cx.tcx
-            .sess
-            .span_err(attr.span, "#[spirv(..)] attribute must have one argument");
-        return None;
-    }
-    let arg = &args[0];
-    if arg.has_name(cx.sym.builtin) {
-        if let Some(builtin_arg) = arg.value_str() {
-            match cx.sym.symbol_to_builtin(builtin_arg) {
-                Some(builtin) => Some(SpirvAttribute::Builtin(builtin)),
-                None => {
-                    cx.tcx.sess.span_err(attr.span, "unknown spir-v builtin");
-                    None
-                }
+// Note that we could mark the attr as used via cx.tcx.sess.mark_attr_used(attr), but unused
+// reporting already happens even before we get here :(
+/// Returns empty if this attribute is not a spirv attribute, or if it's malformed (and an error is
+/// reported).
+pub fn parse_attrs(
+    cx: &CodegenCx<'_>,
+    attrs: &[Attribute],
+) -> impl Iterator<Item = SpirvAttribute> {
+    let result = attrs.iter().flat_map(|attr| {
+        let is_spirv = match attr.kind {
+            AttrKind::Normal(ref item) => {
+                // TODO: We ignore the rest of the path. Is this right?
+                let last = item.path.segments.last();
+                last.map_or(false, |seg| seg.ident.name == cx.sym.spirv)
             }
+            AttrKind::DocComment(..) => false,
+        };
+        let args = if !is_spirv {
+            // Use an empty vec here to return empty
+            Vec::new()
+        } else if let Some(args) = attr.meta_item_list() {
+            args
         } else {
             cx.tcx.sess.span_err(
                 attr.span,
-                "builtin must have value: #[spirv(builtin = \"..\")]",
+                "#[spirv(..)] attribute must have at least one argument",
             );
-            None
-        }
-    } else if arg.has_name(cx.sym.storage_class) {
-        if let Some(storage_arg) = arg.value_str() {
-            match cx.sym.symbol_to_storageclass(storage_arg) {
-                Some(storage_class) => Some(SpirvAttribute::StorageClass(storage_class)),
-                None => {
-                    cx.tcx
-                        .sess
-                        .span_err(attr.span, "unknown spir-v storage class");
-                    None
+            Vec::new()
+        };
+        args.into_iter().filter_map(move |ref arg| {
+            if arg.has_name(cx.sym.descriptor_set) {
+                match parse_attr_int_value(cx, arg) {
+                    Some(x) => Some(SpirvAttribute::DescriptorSet(x)),
+                    None => None,
+                }
+            } else if arg.has_name(cx.sym.binding) {
+                match parse_attr_int_value(cx, arg) {
+                    Some(x) => Some(SpirvAttribute::Binding(x)),
+                    None => None,
+                }
+            } else {
+                let name = match arg.ident() {
+                    Some(i) => i,
+                    None => {
+                        cx.tcx.sess.span_err(
+                            arg.span(),
+                            "#[spirv(..)] attribute argument must be single identifier",
+                        );
+                        return None;
+                    }
+                };
+                match cx.sym.attributes.get(&name.name) {
+                    Some(a) => Some(a.clone()),
+                    None => {
+                        cx.tcx
+                            .sess
+                            .span_err(name.span, "unknown argument to spirv attribute");
+                        None
+                    }
                 }
             }
-        } else {
-            cx.tcx.sess.span_err(
-                attr.span,
-                "storage_class must have value: #[spirv(storage_class = \"..\")]",
-            );
-            None
-        }
-    } else if arg.has_name(cx.sym.entry) {
-        if let Some(storage_arg) = arg.value_str() {
-            match cx.sym.symbol_to_execution_model(storage_arg) {
-                Some(execution_model) => Some(SpirvAttribute::Entry(execution_model)),
-                None => {
-                    cx.tcx
-                        .sess
-                        .span_err(attr.span, "unknown spir-v execution model");
-                    None
-                }
-            }
-        } else {
+        })
+    });
+    // lifetimes are hard :(
+    result.collect::<Vec<_>>().into_iter()
+}
+
+fn parse_attr_int_value(cx: &CodegenCx<'_>, arg: &NestedMetaItem) -> Option<u32> {
+    let arg = match arg.meta_item() {
+        Some(arg) => arg,
+        None => {
             cx.tcx
                 .sess
-                .span_err(attr.span, "entry must have value: #[spirv(entry = \"..\")]");
+                .span_err(arg.span(), "attribute must have value");
+            return None;
+        }
+    };
+    match arg.name_value_literal() {
+        Some(&Lit {
+            kind: LitKind::Int(x, LitIntType::Unsuffixed),
+            ..
+        }) if x <= u32::MAX as u128 => Some(x as u32),
+        _ => {
+            cx.tcx
+                .sess
+                .span_err(arg.span, "attribute value must be integer");
             None
         }
-    } else if arg.has_name(cx.sym.really_unsafe_ignore_bitcasts) {
-        Some(SpirvAttribute::ReallyUnsafeIgnoreBitcasts)
-    } else {
-        cx.tcx
-            .sess
-            .span_err(attr.span, "unknown argument to spirv attribute");
-        None
     }
 }

spirv-builder/src/test/basic.rs

@@ -4,7 +4,7 @@ use super::val;
 fn hello_world() {
     val(r#"
 #[allow(unused_attributes)]
-#[spirv(entry = "fragment")]
+#[spirv(fragment)]
 pub fn main() {
 }
 "#);

spirv-std/src/lib.rs

@@ -54,9 +54,9 @@ macro_rules! pointer_addrspace_write {
 }
 
 macro_rules! pointer_addrspace {
-    ($storage_class:literal, $type_name:ident, $writeable:tt) => {
+    ($storage_class:ident, $type_name:ident, $writeable:tt) => {
         #[allow(unused_attributes)]
-        #[spirv(storage_class = $storage_class)]
+        #[spirv($storage_class)]
         pub struct $type_name<'a, T> {
             x: &'a mut T,
         }
@@ -76,26 +76,26 @@ macro_rules! pointer_addrspace {
 
 // Make sure these strings stay synced with symbols.rs
 // Note the type names don't have to match anything, they can be renamed (only the string must match)
-pointer_addrspace!("uniform_constant", UniformConstant, false);
-pointer_addrspace!("input", Input, false);
-pointer_addrspace!("uniform", Uniform, true);
-pointer_addrspace!("output", Output, true);
-pointer_addrspace!("workgroup", Workgroup, true);
-pointer_addrspace!("cross_workgroup", CrossWorkgroup, true);
-pointer_addrspace!("private", Private, true);
-pointer_addrspace!("function", Function, true);
-pointer_addrspace!("generic", Generic, true);
-pointer_addrspace!("push_constant", PushConstant, false);
-pointer_addrspace!("atomic_counter", AtomicCounter, true);
-pointer_addrspace!("image", Image, true);
-pointer_addrspace!("storage_buffer", StorageBuffer, true);
-pointer_addrspace!("callable_data_khr", CallableDataKHR, true);
-pointer_addrspace!("incoming_callable_data_khr", IncomingCallableDataKHR, true);
-pointer_addrspace!("ray_payload_khr", RayPayloadKHR, true);
-pointer_addrspace!("hit_attribute_khr", HitAttributeKHR, true);
-pointer_addrspace!("incoming_ray_payload_khr", IncomingRayPayloadKHR, true);
-pointer_addrspace!("shader_record_buffer_khr", ShaderRecordBufferKHR, true);
-pointer_addrspace!("physical_storage_buffer", PhysicalStorageBuffer, true);
+pointer_addrspace!(uniform_constant, UniformConstant, false);
+pointer_addrspace!(input, Input, false);
+pointer_addrspace!(uniform, Uniform, true);
+pointer_addrspace!(output, Output, true);
+pointer_addrspace!(workgroup, Workgroup, true);
+pointer_addrspace!(cross_workgroup, CrossWorkgroup, true);
+pointer_addrspace!(private, Private, true);
+pointer_addrspace!(function, Function, true);
+pointer_addrspace!(generic, Generic, true);
+pointer_addrspace!(push_constant, PushConstant, false);
+pointer_addrspace!(atomic_counter, AtomicCounter, true);
+pointer_addrspace!(image, Image, true);
+pointer_addrspace!(storage_buffer, StorageBuffer, true);
+pointer_addrspace!(callable_data_khr, CallableDataKHR, true);
+pointer_addrspace!(incoming_callable_data_khr, IncomingCallableDataKHR, true);
+pointer_addrspace!(ray_payload_khr, RayPayloadKHR, true);
+pointer_addrspace!(hit_attribute_khr, HitAttributeKHR, true);
+pointer_addrspace!(incoming_ray_payload_khr, IncomingRayPayloadKHR, true);
+pointer_addrspace!(shader_record_buffer_khr, ShaderRecordBufferKHR, true);
+pointer_addrspace!(physical_storage_buffer, PhysicalStorageBuffer, true);
 
 #[allow(non_camel_case_types)]
 #[derive(Debug, Clone, Copy)]