feat: recursion working in brillig (#1854)

* feat: recursion working in brillig

* Update crates/noirc_evaluator/src/brillig/brillig_ir/artifact.rs

* fix: removed redundant clone

* Update crates/noirc_evaluator/src/brillig/brillig_ir/artifact.rs

* fix: merge change

Author: sirasistant

crates/nargo_cli/tests/test_data_ssa_refactor/brillig_recursion/Nargo.toml

@@ -0,0 +1,5 @@
+[package]
+authors = [""]
+compiler_version = "0.1"
+
+[dependencies]

crates/nargo_cli/tests/test_data_ssa_refactor/brillig_recursion/Prover.toml

@@ -0,0 +1 @@
+x = "10"

crates/nargo_cli/tests/test_data_ssa_refactor/brillig_recursion/src/main.nr

@@ -0,0 +1,14 @@
+// Tests a very simple program.
+// 
+// The feature being tested is brillig recursion
+fn main(x: u32)  {
+    assert(fibonacci(x) == 55);
+}
+
+unconstrained fn fibonacci(x : u32) -> u32 {
+    if x <= 1 {
+        x
+    } else {
+        fibonacci(x - 1) + fibonacci(x - 2)
+    }
+}

crates/noirc_evaluator/src/brillig/brillig_ir/artifact.rs

@@ -73,14 +73,17 @@ impl BrilligArtifact {
         }
     }
 
-    /// Creates an entry point artifact wrapping the bytecode of the function provided.
-    pub(crate) fn to_entry_point_artifact(artifact: &BrilligArtifact) -> BrilligArtifact {
-        let mut entry_point_artifact =
-            BrilligArtifact::new(artifact.arguments.clone(), artifact.return_parameters.clone());
+    /// Creates an entry point artifact that will jump to the function label provided.
+    pub(crate) fn new_entry_point_artifact(
+        arguments: Vec<BrilligParameter>,
+        return_parameters: Vec<BrilligParameter>,
+        target_function: Label,
+    ) -> BrilligArtifact {
+        let mut entry_point_artifact = BrilligArtifact::new(arguments, return_parameters);
         entry_point_artifact.entry_point_instruction();
 
-        entry_point_artifact.add_unresolved_jumps_and_calls(artifact);
-        entry_point_artifact.byte_code.extend_from_slice(&artifact.byte_code);
+        entry_point_artifact
+            .add_unresolved_external_call(BrilligOpcode::Call { location: 0 }, target_function);
 
         entry_point_artifact.exit_point_instruction();
         entry_point_artifact
@@ -126,16 +129,6 @@ impl BrilligArtifact {
         // We want all functions to follow the calling convention of returning
         // their results in the first `n` registers. So we modify the bytecode of the
         // function to move the return values to the first `n` registers once completed.
-        //
-        // Swap the stop opcode with a jump to the exit point section
-
-        let stop_position =
-            self.byte_code.iter().position(|opcode| matches!(opcode, BrilligOpcode::Stop));
-
-        let stop_position = stop_position.expect("expected a stop opcode");
-
-        let exit_section = self.index_of_next_opcode();
-        self.byte_code[stop_position] = BrilligOpcode::Jump { location: exit_section };
 
         // TODO: this _seems_ like an abstraction leak, we need to know about the reserved
         // TODO: registers in order to do this.

crates/noirc_evaluator/src/ssa_refactor/acir_gen/mod.rs

@@ -2,7 +2,10 @@
 
 use std::collections::HashMap;
 
-use crate::brillig::{brillig_ir::artifact::BrilligArtifact, Brillig};
+use crate::brillig::{
+    brillig_gen::brillig_fn::FunctionContext as BrilligFunctionContext,
+    brillig_ir::artifact::BrilligArtifact, Brillig,
+};
 
 use self::acir_ir::{
     acir_variable::{AcirContext, AcirType, AcirVar},
@@ -338,7 +341,11 @@ impl Context {
 
     fn gen_brillig_for(&self, func: &Function, brillig: &Brillig) -> Vec<Opcode> {
         // Create the entry point artifact
-        let mut entry_point = BrilligArtifact::to_entry_point_artifact(&brillig[func.id()]);
+        let mut entry_point = BrilligArtifact::new_entry_point_artifact(
+            BrilligFunctionContext::parameters(func),
+            BrilligFunctionContext::return_values(func),
+            BrilligFunctionContext::function_id_to_function_label(func.id()),
+        );
         // Link the entry point with all dependencies
         while let Some(unresolved_fn_label) = entry_point.first_unresolved_function_call() {
             let artifact = &brillig