feat(ssa): Pass to preprocess functions

compiler/noirc_evaluator/src/ssa.rs

@@ -150,15 +150,19 @@ pub(crate) fn optimize_into_acir(
 /// Run all SSA passes.
 fn optimize_all(builder: SsaBuilder, options: &SsaEvaluatorOptions) -> Result<Ssa, RuntimeError> {
     Ok(builder
-        .run_pass(Ssa::remove_unreachable_functions, "Removing Unreachable Functions")
+        .run_pass(Ssa::remove_unreachable_functions, "Removing Unreachable Functions (1st)")
         .run_pass(Ssa::defunctionalize, "Defunctionalization")
         .run_pass(Ssa::remove_paired_rc, "Removing Paired rc_inc & rc_decs")
+        .run_pass(
+            |ssa| ssa.preprocess_functions(options.inliner_aggressiveness),
+            "Preprocessing Functions",
+        )
         .run_pass(|ssa| ssa.inline_functions(options.inliner_aggressiveness), "Inlining (1st)")
         // Run mem2reg with the CFG separated into blocks
         .run_pass(Ssa::mem2reg, "Mem2Reg (1st)")
         .run_pass(Ssa::simplify_cfg, "Simplifying (1st)")
         .run_pass(Ssa::as_slice_optimization, "`as_slice` optimization")
-        .run_pass(Ssa::remove_unreachable_functions, "Removing Unreachable Functions")
+        .run_pass(Ssa::remove_unreachable_functions, "Removing Unreachable Functions (2nd)")
         .try_run_pass(
             Ssa::evaluate_static_assert_and_assert_constant,
             "`static_assert` and `assert_constant`",
@@ -188,7 +192,7 @@ fn optimize_all(builder: SsaBuilder, options: &SsaEvaluatorOptions) -> Result<Ss
         .run_pass(Ssa::fold_constants_using_constraints, "Constraint Folding")
         .run_pass(Ssa::make_constrain_not_equal_instructions, "Adding constrain not equal")
         .run_pass(Ssa::dead_instruction_elimination, "Dead Instruction Elimination (1st)")
-        .run_pass(Ssa::simplify_cfg, "Simplifying:")
+        .run_pass(Ssa::simplify_cfg, "Simplifying (3rd):")
         .run_pass(Ssa::array_set_optimization, "Array Set Optimizations")
         .finish())
 }

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

@@ -287,7 +287,8 @@ fn create_apply_function(
         let mut function_builder = FunctionBuilder::new("apply".to_string(), id);
         function_builder.set_globals(globals);
 
-        // We want to push for apply functions to be inlined more aggressively.
+        // We want to push for apply functions to be inlined more aggressively;
+        // they are expected to be optimized away by constants visible at the call site.
         let runtime = match caller_runtime {
             RuntimeType::Acir(_) => RuntimeType::Acir(InlineType::InlineAlways),
             RuntimeType::Brillig(_) => RuntimeType::Brillig(InlineType::InlineAlways),