Handle struct members alignments in generated code

vulkano-shaders/src/lib.rs

@@ -486,6 +486,7 @@ unsafe impl ::vulkano::descriptor_set::PipelineLayoutDesc for Layout {{
     output
 }
 
+// TODO: struct definitions don't use this function, so irrelevant elements should be removed
 fn type_from_id(doc: &parse::Spirv, searched: u32) -> String {
     for instruction in doc.instructions.iter() {
         match instruction {

vulkano-shaders/src/structs.rs

@@ -1,3 +1,5 @@
+use std::mem;
+
 use parse;
 use enums;
 
@@ -24,16 +26,21 @@ fn write_struct(doc: &parse::Spirv, struct_id: u32, members: &[u32]) -> String {
 
     let mut members_defs = Vec::with_capacity(members.len());
 
+    // Contains the offset of the next field.
+    // Equals to `None` if there's a runtime-sized field in there.
+    let mut current_rust_offset = Some(0);
+
     for (num, &member) in members.iter().enumerate() {
-        let ty = ::type_from_id(doc, member);
+        let (ty, rust_size, rust_align) = type_from_id(doc, member);
         let member_name = ::member_name_from_id(doc, struct_id, num as u32);
 
-        // Ignore the field if it is built in, which includes `gl_Position` for example.
+        // Ignore the whole struct is a member is built in, which includes
+        // `gl_Position` for example.
         if is_builtin_member(doc, struct_id, num as u32) {
-            continue;
+            return String::new();
         }
 
-        let offset = doc.instructions.iter().filter_map(|i| {
+        let spirv_offset = doc.instructions.iter().filter_map(|i| {
             match *i {
                 parse::Instruction::MemberDecorate { target_id, member,
                                                    decoration: enums::Decoration::DecorationOffset,
@@ -47,20 +54,39 @@ fn write_struct(doc: &parse::Spirv, struct_id: u32, members: &[u32]) -> String {
 
             None
         }).next().expect(&format!("Struct member `{}` of `{}` is missing an `Offset` decoration",
-                                  member_name, name));
+                                  member_name, name)) as usize;
 
-        members_defs.push(format!("{name}: {ty} /* {off} */", name = member_name, ty = ty, off = offset));
+        // We need to add a dummy field if necessary.
+        {
+            let current_rust_offset = current_rust_offset.as_mut().expect("Found runtime-sized member in non-final position");
+
+            // Updating current_rust_offset to take the alignment of the next field into account
+            *current_rust_offset = if *current_rust_offset == 0 {
+                0
+            } else {
+                (1 + (*current_rust_offset - 1) / rust_align) * rust_align
+            };
+
+            if spirv_offset != *current_rust_offset {
+                let diff = spirv_offset.checked_sub(*current_rust_offset).unwrap();
+                members_defs.push(format!("_dummy: [u8; {}]", diff));       // FIXME: fix name if there are multiple dummies
+                *current_rust_offset += diff;
+            }
+        }
+
+        // Updating `current_rust_offset`.
+        if let Some(s) = rust_size {
+            *current_rust_offset.as_mut().unwrap() += s;
+        } else {
+            current_rust_offset = None;
+        }
+
+        members_defs.push(format!("{name}: {ty}", name = member_name, ty = ty));
     }
 
-    // GLSL doesn't allow empty structures. However it is possible to have structures entirely
-    // made of built-in members, hence this check.
-    if !members_defs.is_empty() {
     format!("#[repr(C)]\n#[derive(Copy, Clone, Debug, Default)]\n\
              pub struct {name} {{\n\t{members}\n}}\n",
             name = name, members = members_defs.join(",\n\t"))
-    } else {
-        String::new()
-    }
 }
 
 /// Returns true if a `BuiltIn` decorator is applied on a struct member.
@@ -81,3 +107,58 @@ fn is_builtin_member(doc: &parse::Spirv, id: u32, member_id: u32) -> bool {
 
     false
 }
+
+/// Returns the type name to put in the Rust struct, and its size and alignment.
+///
+/// The size can be `None` if it's only known at runtime.
+fn type_from_id(doc: &parse::Spirv, searched: u32) -> (String, Option<usize>, usize) {
+    for instruction in doc.instructions.iter() {
+        match instruction {
+            &parse::Instruction::TypeBool { result_id } if result_id == searched => {
+                return ("bool".to_owned(), Some(mem::size_of::<bool>()), mem::align_of::<bool>())
+            },
+            &parse::Instruction::TypeInt { result_id, width, signedness } if result_id == searched => {
+                // FIXME: width
+                return ("i32".to_owned(), Some(mem::size_of::<i32>()), mem::align_of::<i32>())
+            },
+            &parse::Instruction::TypeFloat { result_id, width } if result_id == searched => {
+                // FIXME: width
+                return ("f32".to_owned(), Some(mem::size_of::<f32>()), mem::align_of::<f32>())
+            },
+            &parse::Instruction::TypeVector { result_id, component_id, count } if result_id == searched => {
+                debug_assert_eq!(mem::align_of::<[u32; 3]>(), mem::align_of::<u32>());
+                let (t, t_size, t_align) = type_from_id(doc, component_id);
+                return (format!("[{}; {}]", t, count), t_size.map(|s| s * count as usize), t_align);
+            },
+            &parse::Instruction::TypeMatrix { result_id, column_type_id, column_count } if result_id == searched => {
+                // FIXME: row-major or column-major
+                debug_assert_eq!(mem::align_of::<[u32; 3]>(), mem::align_of::<u32>());
+                let (t, t_size, t_align) = type_from_id(doc, column_type_id);
+                return (format!("[{}; {}]", t, column_count), t_size.map(|s| s * column_count as usize), t_align);
+            },
+            &parse::Instruction::TypeArray { result_id, type_id, length_id } if result_id == searched => {
+                debug_assert_eq!(mem::align_of::<[u32; 3]>(), mem::align_of::<u32>());
+                let (t, t_size, t_align) = type_from_id(doc, type_id);
+                let len = doc.instructions.iter().filter_map(|e| {
+                    match e { &parse::Instruction::Constant { result_id, ref data, .. } if result_id == length_id => Some(data.clone()), _ => None }
+                }).next().expect("failed to find array length");
+                let len = len.iter().rev().fold(0u64, |a, &b| (a << 32) | b as u64);
+                return (format!("[{}; {}]", t, len), t_size.map(|s| s * len as usize), t_align);       // FIXME:
+            },
+            &parse::Instruction::TypeRuntimeArray { result_id, type_id } if result_id == searched => {
+                debug_assert_eq!(mem::align_of::<[u32; 3]>(), mem::align_of::<u32>());
+                let (t, _, t_align) = type_from_id(doc, type_id);
+                return (format!("[{}]", t), None, t_align);
+            },
+            &parse::Instruction::TypeStruct { result_id, ref member_types } if result_id == searched => {
+                let name = ::name_from_id(doc, result_id);
+                let size = member_types.iter().filter_map(|&t| type_from_id(doc, t).1).fold(0, |a,b|a+b);
+                let align = member_types.iter().map(|&t| type_from_id(doc, t).2).max().unwrap_or(1);
+                return (name, Some(size), align);
+            },
+            _ => ()
+        }
+    }
+
+    panic!("Type #{} not found", searched)
+}