fix: map entry point indexes after all ssa passes (#6740)

compiler/noirc_evaluator/src/acir/mod.rs

@@ -821,14 +821,12 @@ impl<'a> Context<'a> {
                                     })
                                     .sum();
 
-                                let Some(acir_function_id) =
-                                    ssa.entry_point_to_generated_index.get(id)
-                                else {
+                                let Some(acir_function_id) = ssa.get_entry_point_index(id) else {
                                     unreachable!("Expected an associated final index for call to acir function {id} with args {arguments:?}");
                                 };
 
                                 let output_vars = self.acir_context.call_acir_function(
-                                    AcirFunctionId(*acir_function_id),
+                                    AcirFunctionId(acir_function_id),
                                     inputs,
                                     output_count,
                                     self.current_side_effects_enabled_var,
@@ -2979,7 +2977,7 @@ mod test {
 
         build_basic_foo_with_return(&mut builder, foo_id, false, inline_type);
 
-        let ssa = builder.finish();
+        let ssa = builder.finish().generate_entry_point_index();
 
         let (acir_functions, _, _, _) = ssa
             .into_acir(&Brillig::default(), ExpressionWidth::default())
@@ -3087,6 +3085,7 @@ mod test {
         let ssa = builder.finish();
 
         let (acir_functions, _, _, _) = ssa
+            .generate_entry_point_index()
             .into_acir(&Brillig::default(), ExpressionWidth::default())
             .expect("Should compile manually written SSA into ACIR");
         // The expected result should look very similar to the above test expect that the input witnesses of the `Call`
@@ -3184,7 +3183,7 @@ mod test {
 
         build_basic_foo_with_return(&mut builder, foo_id, false, inline_type);
 
-        let ssa = builder.finish();
+        let ssa = builder.finish().generate_entry_point_index();
 
         let (acir_functions, _, _, _) = ssa
             .into_acir(&Brillig::default(), ExpressionWidth::default())
@@ -3311,6 +3310,7 @@ mod test {
         let brillig = ssa.to_brillig(false);
 
         let (acir_functions, brillig_functions, _, _) = ssa
+            .generate_entry_point_index()
             .into_acir(&brillig, ExpressionWidth::default())
             .expect("Should compile manually written SSA into ACIR");
 
@@ -3375,6 +3375,7 @@ mod test {
         // The Brillig bytecode we insert for the stdlib is hardcoded so we do not need to provide any
         // Brillig artifacts to the ACIR gen pass.
         let (acir_functions, brillig_functions, _, _) = ssa
+            .generate_entry_point_index()
             .into_acir(&Brillig::default(), ExpressionWidth::default())
             .expect("Should compile manually written SSA into ACIR");
 
@@ -3449,6 +3450,7 @@ mod test {
         println!("{}", ssa);
 
         let (acir_functions, brillig_functions, _, _) = ssa
+            .generate_entry_point_index()
             .into_acir(&brillig, ExpressionWidth::default())
             .expect("Should compile manually written SSA into ACIR");
 
@@ -3537,6 +3539,7 @@ mod test {
         println!("{}", ssa);
 
         let (acir_functions, brillig_functions, _, _) = ssa
+            .generate_entry_point_index()
             .into_acir(&brillig, ExpressionWidth::default())
             .expect("Should compile manually written SSA into ACIR");
 

compiler/noirc_evaluator/src/ssa.rs

@@ -449,7 +449,7 @@ impl SsaBuilder {
     }
 
     fn finish(self) -> Ssa {
-        self.ssa
+        self.ssa.generate_entry_point_index()
     }
 
     /// Runs the given SSA pass and prints the SSA afterward if `print_ssa_passes` is true.

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

@@ -125,11 +125,13 @@ impl Ssa {
         }
 
         // The ones that remain are never called: let's remove them.
-        for func_id in brillig_functions.keys() {
+        for (func_id, func) in &brillig_functions {
             // We never want to remove the main function (it could be `unconstrained` or it
             // could have been turned into brillig if `--force-brillig` was given).
             // We also don't want to remove entry points.
-            if self.main_id == *func_id || self.entry_point_to_generated_index.contains_key(func_id)
+            let runtime = func.runtime();
+            if self.main_id == *func_id
+                || (runtime.is_entry_point() && matches!(runtime, RuntimeType::Acir(_)))
             {
                 continue;
             }

compiler/noirc_evaluator/src/ssa/ssa_gen/program.rs

@@ -25,7 +25,7 @@ pub(crate) struct Ssa {
     /// This mapping is necessary to use the correct function pointer for an ACIR call,
     /// as the final program artifact will be a list of only entry point functions.
     #[serde(skip)]
-    pub(crate) entry_point_to_generated_index: BTreeMap<FunctionId, u32>,
+    entry_point_to_generated_index: BTreeMap<FunctionId, u32>,
     // We can skip serializing this field as the error selector types end up as part of the
     // ABI not the actual SSA IR.
     #[serde(skip)]
@@ -47,25 +47,11 @@ impl Ssa {
             (f.id(), f)
         });
 
-        let entry_point_to_generated_index = btree_map(
-            functions
-                .iter()
-                .filter(|(_, func)| {
-                    let runtime = func.runtime();
-                    match func.runtime() {
-                        RuntimeType::Acir(_) => runtime.is_entry_point() || func.id() == main_id,
-                        RuntimeType::Brillig(_) => false,
-                    }
-                })
-                .enumerate(),
-            |(i, (id, _))| (*id, i as u32),
-        );
-
         Self {
             functions,
             main_id,
             next_id: AtomicCounter::starting_after(max_id),
-            entry_point_to_generated_index,
+            entry_point_to_generated_index: BTreeMap::new(),
             error_selector_to_type: error_types,
         }
     }
@@ -98,6 +84,33 @@ impl Ssa {
         self.functions.insert(new_id, function);
         new_id
     }
+    pub(crate) fn generate_entry_point_index(mut self) -> Self {
+        self.entry_point_to_generated_index = btree_map(
+            self.functions
+                .iter()
+                .filter(|(_, func)| {
+                    let runtime = func.runtime();
+                    match func.runtime() {
+                        RuntimeType::Acir(_) => {
+                            runtime.is_entry_point() || func.id() == self.main_id
+                        }
+                        RuntimeType::Brillig(_) => false,
+                    }
+                })
+                .enumerate(),
+            |(i, (id, _))| (*id, i as u32),
+        );
+        self
+    }
+
+    pub(crate) fn get_entry_point_index(&self, func_id: &FunctionId) -> Option<u32> {
+        // Ensure the map has been initialized
+        assert!(
+            !self.entry_point_to_generated_index.is_empty(),
+            "Trying to read uninitialized entry point index"
+        );
+        self.entry_point_to_generated_index.get(func_id).copied()
+    }
 }
 
 impl Display for Ssa {