Minor cleanups.

- Add comment explaining why it's okay to use `back::spv::GlobalVariable::var_id` instead of `access_id`. - Rename `const_id` to `zero_id`. - Return early to reduce indentation.
gfx-rs · Jan 25, 2023 · 0458e45 · 0458e45
1 parent 623988c
commit 0458e45
Showing 1 changed file with 67 additions and 64 deletions.
diff --git a/src/back/spv/writer.rs b/src/back/spv/writer.rs
@@ -1240,92 +1240,95 @@ impl Writer {
                 !info[handle].is_empty() && var.space == crate::AddressSpace::WorkGroup
             })
             .map(|(handle, var)| {
+                // It's safe to use `var_id` here, not `access_id`, because only
+                // variables in the `Uniform` and `StorageBuffer` address spaces
+                // get wrapped, and we're initializing `WorkGroup` variables.
                 let var_id = self.global_variables[handle.index()].var_id;
                 let var_type_id = self.get_type_id(LookupType::Handle(var.ty));
                 let init_word = self.write_constant_null(var_type_id);
                 Instruction::store(var_id, init_word, None)
             })
             .collect::<Vec<_>>();
 
-        if !body.is_empty() {
-            let uint3_type_id = self.get_uint3_type_id();
+        if body.is_empty() {
+            return None;
+        }
 
-            let mut pre_if_block = Block::new(entry_id);
+        let uint3_type_id = self.get_uint3_type_id();
 
-            let global_invocation_id = if let Some(global_invocation_id) = global_invocation_id {
-                global_invocation_id
-            } else {
-                let varying_id = self.id_gen.next();
-                let class = spirv::StorageClass::Input;
-                let pointer_type_id = self.get_uint3_pointer_type_id(class);
+        let mut pre_if_block = Block::new(entry_id);
 
-                Instruction::variable(pointer_type_id, varying_id, class, None)
-                    .to_words(&mut self.logical_layout.declarations);
+        let global_invocation_id = if let Some(global_invocation_id) = global_invocation_id {
+            global_invocation_id
+        } else {
+            let varying_id = self.id_gen.next();
+            let class = spirv::StorageClass::Input;
+            let pointer_type_id = self.get_uint3_pointer_type_id(class);
 
-                self.decorate(
-                    varying_id,
-                    spirv::Decoration::BuiltIn,
-                    &[spirv::BuiltIn::GlobalInvocationId as u32],
-                );
+            Instruction::variable(pointer_type_id, varying_id, class, None)
+                .to_words(&mut self.logical_layout.declarations);
 
-                interface.varying_ids.push(varying_id);
-                let id = self.id_gen.next();
-                pre_if_block
-                    .body
-                    .push(Instruction::load(uint3_type_id, id, varying_id, None));
+            self.decorate(
+                varying_id,
+                spirv::Decoration::BuiltIn,
+                &[spirv::BuiltIn::GlobalInvocationId as u32],
+            );
 
-                id
-            };
+            interface.varying_ids.push(varying_id);
+            let id = self.id_gen.next();
+            pre_if_block
+                .body
+                .push(Instruction::load(uint3_type_id, id, varying_id, None));
 
-            let const_id = self.write_constant_null(uint3_type_id);
-            let bool3_type_id = self.get_bool3_type_id();
+            id
+        };
 
-            let eq_id = self.id_gen.next();
-            pre_if_block.body.push(Instruction::binary(
-                spirv::Op::IEqual,
-                bool3_type_id,
-                eq_id,
-                global_invocation_id,
-                const_id,
-            ));
+        let zero_id = self.write_constant_null(uint3_type_id);
+        let bool3_type_id = self.get_bool3_type_id();
 
-            let condition_id = self.id_gen.next();
-            let bool_type_id = self.get_bool_type_id();
-            pre_if_block.body.push(Instruction::relational(
-                spirv::Op::All,
-                bool_type_id,
-                condition_id,
-                eq_id,
-            ));
+        let eq_id = self.id_gen.next();
+        pre_if_block.body.push(Instruction::binary(
+            spirv::Op::IEqual,
+            bool3_type_id,
+            eq_id,
+            global_invocation_id,
+            zero_id,
+        ));
 
-            let merge_id = self.id_gen.next();
-            pre_if_block.body.push(Instruction::selection_merge(
-                merge_id,
-                spirv::SelectionControl::NONE,
-            ));
+        let condition_id = self.id_gen.next();
+        let bool_type_id = self.get_bool_type_id();
+        pre_if_block.body.push(Instruction::relational(
+            spirv::Op::All,
+            bool_type_id,
+            condition_id,
+            eq_id,
+        ));
 
-            let accept_id = self.id_gen.next();
-            function.consume(
-                pre_if_block,
-                Instruction::branch_conditional(condition_id, accept_id, merge_id),
-            );
+        let merge_id = self.id_gen.next();
+        pre_if_block.body.push(Instruction::selection_merge(
+            merge_id,
+            spirv::SelectionControl::NONE,
+        ));
 
-            let accept_block = Block {
-                label_id: accept_id,
-                body,
-            };
-            function.consume(accept_block, Instruction::branch(merge_id));
+        let accept_id = self.id_gen.next();
+        function.consume(
+            pre_if_block,
+            Instruction::branch_conditional(condition_id, accept_id, merge_id),
+        );
+
+        let accept_block = Block {
+            label_id: accept_id,
+            body,
+        };
+        function.consume(accept_block, Instruction::branch(merge_id));
 
-            let mut post_if_block = Block::new(merge_id);
+        let mut post_if_block = Block::new(merge_id);
 
-            self.write_barrier(crate::Barrier::WORK_GROUP, &mut post_if_block);
+        self.write_barrier(crate::Barrier::WORK_GROUP, &mut post_if_block);
 
-            let next_id = self.id_gen.next();
-            function.consume(post_if_block, Instruction::branch(next_id));
-            Some(next_id)
-        } else {
-            None
-        }
+        let next_id = self.id_gen.next();
+        function.consume(post_if_block, Instruction::branch(next_id));
+        Some(next_id)
     }
 
     /// Generate an `OpVariable` for one value in an [`EntryPoint`]'s IO interface.