feat: data bus

compiler/noirc_driver/src/abi_gen.rs

@@ -2,11 +2,12 @@ use std::collections::BTreeMap;
 
 use acvm::acir::native_types::Witness;
 use iter_extended::{btree_map, vecmap};
-use noirc_abi::{Abi, AbiParameter, AbiType};
+use noirc_abi::{Abi, AbiParameter, AbiReturnType, AbiType};
 use noirc_frontend::{
     hir::Context,
     hir_def::{function::Param, stmt::HirPattern},
     node_interner::{FuncId, NodeInterner},
+    Visibility,
 };
 use std::ops::Range;
 
@@ -17,9 +18,12 @@ pub(super) fn gen_abi(
     func_id: &FuncId,
     input_witnesses: Vec<Witness>,
     return_witnesses: Vec<Witness>,
+    return_visibility: Visibility,
 ) -> Abi {
     let (parameters, return_type) = compute_function_abi(context, func_id);
     let param_witnesses = param_witnesses_from_abi_param(&parameters, input_witnesses);
+    let return_type = return_type
+        .map(|typ| AbiReturnType { abi_type: typ, visibility: return_visibility.into() });
     Abi { parameters, return_type, param_witnesses, return_witnesses }
 }
 

compiler/noirc_driver/src/lib.rs

@@ -346,11 +346,12 @@ pub fn compile_no_check(
     if !force_compile && hashes_match {
         return Ok(cached_program.expect("cache must exist for hashes to match"));
     }
-
+    let visibility = program.return_visibility;
     let (circuit, debug, input_witnesses, return_witnesses, warnings) =
         create_circuit(program, options.show_ssa, options.show_brillig)?;
 
-    let abi = abi_gen::gen_abi(context, &main_function, input_witnesses, return_witnesses);
+    let abi =
+        abi_gen::gen_abi(context, &main_function, input_witnesses, return_witnesses, visibility);
     let file_map = filter_relevant_files(&[debug.clone()], &context.file_manager);
 
     Ok(CompiledProgram {

compiler/noirc_evaluator/src/ssa/acir_gen/mod.rs

@@ -5,6 +5,7 @@ use std::collections::HashSet;
 use std::fmt::Debug;
 
 use self::acir_ir::acir_variable::{AcirContext, AcirType, AcirVar};
+use super::function_builder::data_bus::DataBus;
 use super::ir::dfg::CallStack;
 use super::{
     ir::{
@@ -90,6 +91,8 @@ struct Context {
     /// Maps SSA array values to their slice size and any nested slices internal to the parent slice.
     /// This enables us to maintain the slice structure of a slice when performing an array get.
     slice_sizes: HashMap<Id<Value>, Vec<usize>>,
+
+    data_bus: DataBus,
 }
 
 #[derive(Clone)]
@@ -199,6 +202,7 @@ impl Context {
             internal_mem_block_lengths: HashMap::default(),
             max_block_id: 0,
             slice_sizes: HashMap::default(),
+            data_bus: DataBus::default(),
         }
     }
 
@@ -226,6 +230,8 @@ impl Context {
         let dfg = &main_func.dfg;
         let entry_block = &dfg[main_func.entry_block()];
         let input_witness = self.convert_ssa_block_params(entry_block.parameters(), dfg)?;
+
+        self.data_bus = dfg.data_bus.to_owned();
         let mut warnings = Vec::new();
         for instruction_id in entry_block.instructions() {
             warnings.extend(self.convert_ssa_instruction(
@@ -892,10 +898,26 @@ impl Context {
         dfg: &DataFlowGraph,
     ) -> Result<AcirValue, RuntimeError> {
         let (array_id, _, block_id) = self.check_array_is_initialized(array, dfg)?;
-
         let results = dfg.instruction_results(instruction);
         let res_typ = dfg.type_of_value(results[0]);
 
+        // Get operations to call-data parameters are replaced by a get to the call-data-bus array
+        if let Some(call_data) = self.data_bus.call_data {
+            if self.data_bus.call_data_map.contains_key(&array_id) {
+                // TODO: the block_id of call-data must be notified to the backend
+                // TODO: should we do the same for return-data?
+                let type_size = res_typ.flattened_size();
+                let type_size =
+                    self.acir_context.add_constant(FieldElement::from(type_size as i128));
+                let offset = self.acir_context.mul_var(var_index, type_size)?;
+                let bus_index = self.acir_context.add_constant(FieldElement::from(
+                    self.data_bus.call_data_map[&array_id] as i128,
+                ));
+                let new_index = self.acir_context.add_var(offset, bus_index)?;
+                return self.array_get(instruction, call_data, new_index, dfg);
+            }
+        }
+
         let value = if !res_typ.contains_slice_element() {
             self.array_get_value(&res_typ, block_id, &mut var_index, &[])?
         } else {

compiler/noirc_evaluator/src/ssa/function_builder/data_bus.rs

@@ -0,0 +1,144 @@
+use std::rc::Rc;
+
+use crate::ssa::ir::{types::Type, value::ValueId};
+use acvm::FieldElement;
+use fxhash::FxHashMap as HashMap;
+use noirc_frontend::hir_def::function::FunctionSignature;
+
+use super::FunctionBuilder;
+
+/// Used to create a data bus, which is an array of private inputs
+/// replacing public inputs
+pub(crate) struct DataBusBuilder {
+    pub(crate) values: im::Vector<ValueId>,
+    index: usize,
+    pub(crate) map: HashMap<ValueId, usize>,
+    pub(crate) databus: Option<ValueId>,
+}
+
+impl DataBusBuilder {
+    pub(crate) fn new() -> DataBusBuilder {
+        DataBusBuilder {
+            index: 0,
+            map: HashMap::default(),
+            databus: None,
+            values: im::Vector::new(),
+        }
+    }
+
+    /// Generates a boolean vector telling which (ssa) parameter from the given function signature
+    /// are tagged with databus visibility
+    pub(crate) fn is_databus(main_signature: &FunctionSignature) -> Vec<bool> {
+        let mut params_is_databus = Vec::new();
+
+        for param in &main_signature.0 {
+            let is_databus = match param.2 {
+                noirc_frontend::Visibility::Public | noirc_frontend::Visibility::Private => false,
+                noirc_frontend::Visibility::DataBus => true,
+            };
+            let len = param.1.field_count() as usize;
+            params_is_databus.extend(vec![is_databus; len]);
+        }
+        params_is_databus
+    }
+}
+
+#[derive(Clone, Default, Debug)]
+pub(crate) struct DataBus {
+    pub(crate) call_data: Option<ValueId>,
+    pub(crate) call_data_map: HashMap<ValueId, usize>,
+    pub(crate) return_data: Option<ValueId>,
+}
+
+impl DataBus {
+    /// Updates the databus values with the provided function
+    pub(crate) fn map_values(&self, mut f: impl FnMut(ValueId) -> ValueId) -> DataBus {
+        let mut call_data_map = HashMap::default();
+        for (k, v) in self.call_data_map.iter() {
+            call_data_map.insert(f(*k), *v);
+        }
+        DataBus {
+            call_data: self.call_data.map(&mut f),
+            call_data_map,
+            return_data: self.return_data.map(&mut f),
+        }
+    }
+
+    /// Construct a databus from call_data and return_data data bus builders
+    pub(crate) fn get_data_bus(call_data: DataBusBuilder, return_data: DataBusBuilder) -> DataBus {
+        DataBus {
+            call_data: call_data.databus,
+            call_data_map: call_data.map,
+            return_data: return_data.databus,
+        }
+    }
+}
+
+impl FunctionBuilder {
+    /// Insert a value into a data bus builder
+    fn add_to_data_bus(&mut self, value: ValueId, databus: &mut DataBusBuilder) {
+        assert!(databus.databus.is_none(), "initialising finalized call data");
+        let typ = self.current_function.dfg[value].get_type().clone();
+        match typ {
+            Type::Numeric(_) => {
+                databus.values.push_back(value);
+                databus.index += 1;
+            }
+            Type::Reference(_) => unreachable!(),
+            Type::Array(typ, len) => {
+                assert!(typ.len() == 1, "unsupported composite type");
+                databus.map.insert(value, databus.index);
+                for i in 0..len {
+                    // load each element of the array
+                    let index = self
+                        .current_function
+                        .dfg
+                        .make_constant(FieldElement::from(i as i128), Type::field());
+                    let element = self.insert_array_get(value, index, typ[0].clone());
+                    self.add_to_data_bus(element, databus);
+                }
+            }
+            Type::Slice(_) => unreachable!(),
+            Type::Function => unreachable!(),
+        }
+    }
+
+    /// Create a data bus builder from a list of values
+    pub(crate) fn initialize_data_bus(
+        &mut self,
+        values: &[ValueId],
+        mut databus: DataBusBuilder,
+    ) -> DataBusBuilder {
+        for value in values {
+            self.add_to_data_bus(*value, &mut databus);
+        }
+        let len = databus.values.len();
+
+        let array = if len > 0 {
+            let array =
+                self.array_constant(databus.values, Type::Array(Rc::new(vec![Type::field()]), len));
+            Some(array)
+        } else {
+            None
+        };
+
+        DataBusBuilder { index: 0, map: databus.map, databus: array, values: im::Vector::new() }
+    }
+
+    /// Generate the data bus for call-data, based on the parameters of the entry block
+    /// and a boolean vector telling which ones are call-data
+    pub(crate) fn call_data_bus(&mut self, is_params_databus: Vec<bool>) -> DataBusBuilder {
+        //filter parameters of the first block that have call-data visilibity
+        let first_block = self.current_function.entry_block();
+        let params = self.current_function.dfg[first_block].parameters();
+        let mut databus_param = Vec::new();
+        for (param, is_databus) in params.iter().zip(is_params_databus) {
+            if is_databus {
+                databus_param.push(param.to_owned());
+            }
+        }
+        // create the call-data-bus from the filtered list
+        let call_data = DataBusBuilder::new();
+        self.initialize_data_bus(&databus_param, call_data)
+    }
+}

compiler/noirc_evaluator/src/ssa/function_builder/mod.rs

@@ -1,3 +1,5 @@
+pub(crate) mod data_bus;
+
 use std::{borrow::Cow, rc::Rc};
 
 use acvm::FieldElement;

compiler/noirc_evaluator/src/ssa/ir/dfg.rs

@@ -1,6 +1,6 @@
 use std::borrow::Cow;
 
-use crate::ssa::ir::instruction::SimplifyResult;
+use crate::ssa::{function_builder::data_bus::DataBus, ir::instruction::SimplifyResult};
 
 use super::{
     basic_block::{BasicBlock, BasicBlockId},
@@ -80,6 +80,8 @@ pub(crate) struct DataFlowGraph {
     /// Instructions inserted by internal SSA passes that don't correspond to user code
     /// may not have a corresponding location.
     locations: HashMap<InstructionId, CallStack>,
+
+    pub(crate) data_bus: DataBus,
 }
 
 pub(crate) type CallStack = im::Vector<Location>;

compiler/noirc_evaluator/src/ssa/opt/die.rs

@@ -33,6 +33,10 @@ impl Ssa {
 /// of its instructions are needed elsewhere.
 fn dead_instruction_elimination(function: &mut Function) {
     let mut context = Context::default();
+    if let Some(call_data) = function.dfg.data_bus.call_data {
+        context.mark_used_instruction_results(&function.dfg, call_data);
+    }
+
     let blocks = PostOrder::with_function(function);
 
     for block in blocks.as_slice() {

compiler/noirc_evaluator/src/ssa/opt/fill_internal_slices.rs

@@ -67,8 +67,11 @@ impl Ssa {
             // The pass is also currently only setup to handle a function with a single flattened block.
             // For complex Brillig functions we can expect this pass to panic.
             if function.runtime() == RuntimeType::Acir {
+                let databus = function.dfg.data_bus.clone();
                 let mut context = Context::new(function);
                 context.process_blocks();
+                // update the databus with the new array instructions
+                function.dfg.data_bus = databus.map_values(|t| context.inserter.resolve(t));
             }
         }
         self

compiler/noirc_evaluator/src/ssa/opt/inlining.rs

@@ -139,11 +139,15 @@ impl InlineContext {
 
         context.blocks.insert(context.source_function.entry_block(), entry_block);
         context.inline_blocks(ssa);
+        // translate databus values
+        let databus = entry_point.dfg.data_bus.map_values(|t| context.translate_value(t));
 
         // Finally, we should have 1 function left representing the inlined version of the target function.
         let mut new_ssa = self.builder.finish();
         assert_eq!(new_ssa.functions.len(), 1);
-        new_ssa.functions.pop_first().unwrap().1
+        let mut new_func = new_ssa.functions.pop_first().unwrap().1;
+        new_func.dfg.data_bus = databus;
+        new_func
     }
 
     /// Inlines a function into the current function and returns the translated return values

compiler/noirc_evaluator/src/ssa/opt/mem2reg.rs

@@ -91,6 +91,7 @@ impl Ssa {
             let mut context = PerFunctionContext::new(function);
             context.mem2reg();
             context.remove_instructions();
+            context.update_data_bus();
         }
         self
     }
@@ -362,6 +363,11 @@ impl<'f> PerFunctionContext<'f> {
         }
     }
 
+    fn update_data_bus(&mut self) {
+        let databus = self.inserter.function.dfg.data_bus.clone();
+        self.inserter.function.dfg.data_bus = databus.map_values(|t| self.inserter.resolve(t));
+    }
+
     fn handle_terminator(&mut self, block: BasicBlockId, references: &mut Block) {
         self.inserter.map_terminator_in_place(block);