fix: preserve functions which are used in array_set instructions

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

@@ -87,6 +87,7 @@ fn used_functions(func: &Function) -> BTreeSet<FunctionId> {
                 Instruction::Store { .. }
                     | Instruction::Call { .. }
                     | Instruction::MakeArray { .. }
+                    | Instruction::ArraySet { .. }
             ) {
                 instruction.for_each_value(&mut find_functions);
             }
@@ -211,4 +212,38 @@ mod tests {
 
         assert_normalized_ssa_equals(ssa, src);
     }
+
+    #[test]
+    fn keep_functions_used_in_array_set() {
+        // Regression test for issue "V-NSCA-VUL-003: Missing ArraySet case in Removing Unreachable Functions pass"
+        // found in Veridise Audit. https://github.com/noir-lang/noir/issues/8890
+
+        // f2 is written to an array using an `array_set` instruction. Thus, we do not want to remove it.
+        let src = r#"
+        acir(inline) fn main f0 {
+          b0(v0: Field, v1: Field):
+            v2 = make_array [f1] : [function; 1]
+            v3 = array_set v2, index u32 0, value f2
+            v4 = array_get v3, index u32 0 -> function
+            v5 = call v4(v0) -> Field
+            return
+          }
+
+          acir(inline) fn my_fun f1 {
+            b0(v0: Field):
+              v2 = add v0, Field 1
+              return v2
+          }
+
+          acir(inline) fn my_fun2 f2 {
+            b0(v0: Field):
+              v2 = add v0, Field 2
+              return v2
+          }"#;
+
+        let ssa = Ssa::from_str(src).unwrap();
+        let ssa = ssa.remove_unreachable_functions();
+
+        assert_normalized_ssa_equals(ssa, src);
+    }
 }

cspell.json

@@ -195,6 +195,7 @@
         "nomicfoundation",
         "noncanonical",
         "nouner",
+        "NSCA",
         "oneof",
         "oneshot",
         "Ottenstein",
@@ -288,6 +289,7 @@
         "vecmap",
         "vecs",
         "Vecs",
+        "Veridise",
         "vitkov",
         "VM",
         "walkdir",

test_programs/execution_success/regression_8890/Nargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "regression_8890"
+version = "0.1.0"
+type = "bin"
+authors = [""]
+
+[dependencies]

test_programs/execution_success/regression_8890/Prover.toml

@@ -0,0 +1,4 @@
+x = "3"
+y = "4"
+
+return = 5

test_programs/execution_success/regression_8890/src/main.nr

@@ -0,0 +1,17 @@
+// Regression test for issue "V-NSCA-VUL-003: Missing ArraySet case in Removing Unreachable Functions pass"
+// found in Veridise Audit.
+
+fn main(x: Field, y: pub Field) -> pub Field {
+    assert(x != y);
+    let mut f = [my_fun];
+    f[0] = my_fun2;
+    (f[0])(x)
+}
+
+fn my_fun(x: Field) -> Field {
+    x + 1
+}
+
+fn my_fun2(x: Field) -> Field {
+    x + 2
+}