fix: handle nested arrays in calldata (noir-lang#6232)

# Description

## Problem\*

This PR builds on noir-lang#6225 and adds support for nested arrays in calldata

## Summary\*
Reconstruct the acir array when reading a nested structure from
calldata.


## Additional Context



## Documentation\*

Check one:
- [X] No documentation needed.
- [ ] Documentation included in this PR.
- [ ] **[For Experimental Features]** Documentation to be submitted in a
separate PR.

# PR Checklist\*

- [X] I have tested the changes locally.
- [X] I have formatted the changes with [Prettier](https://prettier.io/)
and/or `cargo fmt` on default settings.

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

@@ -1303,6 +1303,29 @@ impl<'a> Context<'a> {
         }
     }
 
+    /// Returns the acir value at the provided databus offset
+    fn get_from_call_data(
+        &mut self,
+        offset: &mut AcirVar,
+        call_data_block: BlockId,
+        typ: &Type,
+    ) -> Result<AcirValue, RuntimeError> {
+        match typ {
+            Type::Numeric(_) => self.array_get_value(&Type::field(), call_data_block, offset),
+            Type::Array(arc, len) => {
+                let mut result = Vector::new();
+                for _i in 0..*len {
+                    for sub_type in arc.iter() {
+                        let element = self.get_from_call_data(offset, call_data_block, sub_type)?;
+                        result.push_back(element);
+                    }
+                }
+                Ok(AcirValue::Array(result))
+            }
+            _ => unimplemented!("Unsupported type in databus"),
+        }
+    }
+
     /// Generates a read opcode for the array
     /// `index_side_effect == false` means that we ensured `var_index` will have a type matching the value in the array
     fn array_get(
@@ -1316,27 +1339,19 @@ impl<'a> Context<'a> {
         let block_id = self.ensure_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.iter().find(|cd| cd.index_map.contains_key(&array))
-        {
-            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 call_data =
+            self.data_bus.call_data.iter().find(|cd| cd.index_map.contains_key(&array)).cloned();
+        if let Some(call_data) = call_data {
+            let call_data_block = self.ensure_array_is_initialized(call_data.array_id, dfg)?;
             let bus_index = self
                 .acir_context
                 .add_constant(FieldElement::from(call_data.index_map[&array] as i128));
-            let new_index = self.acir_context.add_var(offset, bus_index)?;
-            return self.array_get(
-                instruction,
-                call_data.array_id,
-                new_index,
-                dfg,
-                index_side_effect,
-            );
+            let mut current_index = self.acir_context.add_var(bus_index, var_index)?;
+            let result = self.get_from_call_data(&mut current_index, call_data_block, &res_typ)?;
+            self.define_result(dfg, instruction, result.clone());
+            return Ok(result);
         }
-
         // Compiler sanity check
         assert!(
             !res_typ.contains_slice_element(),

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

@@ -122,15 +122,21 @@ impl FunctionBuilder {
             }
             Type::Array(typ, len) => {
                 databus.map.insert(value, databus.index);
-                for i in 0..len {
-                    for (subitem_index, subitem_typ) in typ.iter().enumerate() {
-                        let index = i * typ.len() + subitem_index;
-                        // load each element of the array
-                        let index = self
+
+                let mut index = 0;
+                for _i in 0..len {
+                    for subitem_typ in typ.iter() {
+                        // load each element of the array, and add it to the databus
+                        let index_var = self
                             .current_function
                             .dfg
                             .make_constant(FieldElement::from(index as i128), Type::length_type());
-                        let element = self.insert_array_get(value, index, subitem_typ.clone());
+                        let element = self.insert_array_get(value, index_var, subitem_typ.clone());
+                        index += match subitem_typ {
+                            Type::Array(_, _) | Type::Slice(_) => subitem_typ.element_size(),
+                            Type::Numeric(_) => 1,
+                            _ => unreachable!("Unsupported type for databus"),
+                        };
                         self.add_to_data_bus(element, databus);
                     }
                 }

test_programs/execution_success/databus_composite_calldata/Prover.toml

@@ -1,9 +1,11 @@
 zero = "0"
 one = "1"
+values = [[["12", "33"], ["37", "11"]],[["14", "37"], ["30", "10"]],[["10", "30"], ["30", "10"]]]
+
 [[foos]]
-x = "27"
-y = "40"
+x = 1
+y = [1,2,3,4,5,6,7,8,9,0]
 
 [[foos]]
-x = "28"
-y = "42"
+x = 2
+y = [1,2,3,5,6,8,7,8,9,0]

test_programs/execution_success/databus_composite_calldata/src/main.nr

@@ -1,11 +1,16 @@
 struct Foo {
     x: u32,
-    y: u32,
+    y: [u32; 10],
 }
 
-fn main(foos: call_data(0) [Foo; 2], zero: u32, one: u32) -> return_data u32 {
+fn main(
+    foos: call_data(0) [Foo; 2],
+    values: call_data(0) [[[u32; 2]; 2]; 3],
+    zero: u32,
+    one: u32
+) -> pub u32 {
     assert_eq(foos[zero].x + 1, foos[one].x);
-    assert_eq(foos[zero].y + 2, foos[one].y);
-    foos[zero].x + foos[one].y
+    assert_eq(foos[zero].y[3] + 2, foos[one].y[4]);
+    assert_eq(values[zero][one][zero], values[one][zero][one]);
+    foos[zero].x + foos[one].y[0]
 }
-