From 9d917e46126e3527486bcf24f0d0c4512543ff2b Mon Sep 17 00:00:00 2001
From: Maxim Vezenov <mvezenov@gmail.com>
Date: Wed, 26 Feb 2025 00:39:52 +0000
Subject: [PATCH] Do not run opt passes on Brillig functions post Brillig gen
---
compiler/noirc_evaluator/src/ssa.rs | 2 +-
.../src/ssa/opt/constant_folding.rs | 5 +++++
compiler/noirc_evaluator/src/ssa/opt/die.rs | 21 ++++++++++++++-----
.../src/ssa/opt/preprocess_fns.rs | 2 +-
4 files changed, 23 insertions(+), 7 deletions(-)
diff --git a/compiler/noirc_evaluator/src/ssa.rs b/compiler/noirc_evaluator/src/ssa.rs
index fce597d81bd..b3c509dc5cc 100644
--- a/compiler/noirc_evaluator/src/ssa.rs
+++ b/compiler/noirc_evaluator/src/ssa.rs
@@ -132,7 +132,7 @@ pub(crate) fn optimize_into_acir(
// It could happen that we inlined all calls to a given brillig function.
// In that case it's unused so we can remove it. This is what we check next.
.run_pass(Ssa::remove_unreachable_functions, "Removing Unreachable Functions (4th)")
- .run_pass(Ssa::dead_instruction_elimination, "Dead Instruction Elimination (3rd)")
+ .run_pass(Ssa::dead_instruction_elimination_acir, "Dead Instruction Elimination (3rd)")
.finish();
if !options.skip_underconstrained_check {
diff --git a/compiler/noirc_evaluator/src/ssa/opt/constant_folding.rs b/compiler/noirc_evaluator/src/ssa/opt/constant_folding.rs
index 05bd48b8830..373d99994a1 100644
--- a/compiler/noirc_evaluator/src/ssa/opt/constant_folding.rs
+++ b/compiler/noirc_evaluator/src/ssa/opt/constant_folding.rs
@@ -95,6 +95,11 @@ impl Ssa {
let brillig_info = Some(BrilligInfo { brillig, brillig_functions: &brillig_functions });
for function in self.functions.values_mut() {
+ // We have already performed our final Brillig generation, so constant folding
+ // Brillig functions is unnecessary work.
+ if function.dfg.runtime().is_brillig() {
+ continue;
+ }
function.constant_fold(false, brillig_info);
}
diff --git a/compiler/noirc_evaluator/src/ssa/opt/die.rs b/compiler/noirc_evaluator/src/ssa/opt/die.rs
index d23cfee8a14..c45e1886269 100644
--- a/compiler/noirc_evaluator/src/ssa/opt/die.rs
+++ b/compiler/noirc_evaluator/src/ssa/opt/die.rs
@@ -26,15 +26,21 @@ impl Ssa {
/// This step should come after the flattening of the CFG and mem2reg.
#[tracing::instrument(level = "trace", skip(self))]
pub(crate) fn dead_instruction_elimination(self) -> Ssa {
- self.dead_instruction_elimination_inner(true)
+ self.dead_instruction_elimination_inner(true, false)
}
- fn dead_instruction_elimination_inner(mut self, flattened: bool) -> Ssa {
+ /// Post the Brillig generation we do not need to run this pass on Brillig functions.
+ #[tracing::instrument(level = "trace", skip(self))]
+ pub(crate) fn dead_instruction_elimination_acir(self) -> Ssa {
+ self.dead_instruction_elimination_inner(true, true)
+ }
+
+ fn dead_instruction_elimination_inner(mut self, flattened: bool, skip_brillig: bool) -> Ssa {
let mut used_globals_map: HashMap<_, _> = self
.functions
.par_iter_mut()
.filter_map(|(id, func)| {
- let set = func.dead_instruction_elimination(true, flattened);
+ let set = func.dead_instruction_elimination(true, flattened, skip_brillig);
if func.runtime().is_brillig() {
Some((*id, set))
} else {
@@ -79,7 +85,12 @@ impl Function {
&mut self,
insert_out_of_bounds_checks: bool,
flattened: bool,
+ skip_brillig: bool,
) -> HashSet<ValueId> {
+ if skip_brillig && self.dfg.runtime().is_brillig() {
+ return HashSet::default();
+ }
+
let mut context = Context { flattened, ..Default::default() };
context.mark_function_parameter_arrays_as_used(self);
@@ -103,7 +114,7 @@ impl Function {
// instructions (we don't want to remove those checks, or instructions that are
// dependencies of those checks)
if inserted_out_of_bounds_checks {
- return self.dead_instruction_elimination(false, flattened);
+ return self.dead_instruction_elimination(false, flattened, skip_brillig);
}
context.remove_rc_instructions(&mut self.dfg);
@@ -1099,7 +1110,7 @@ mod test {
let ssa = Ssa::from_str(src).unwrap();
// Even though these ACIR functions only have 1 block, we have not inlined and flattened anything yet.
- let ssa = ssa.dead_instruction_elimination_inner(false);
+ let ssa = ssa.dead_instruction_elimination_inner(false, false);
let expected = "
acir(inline) fn main f0 {
diff --git a/compiler/noirc_evaluator/src/ssa/opt/preprocess_fns.rs b/compiler/noirc_evaluator/src/ssa/opt/preprocess_fns.rs
index 764fb6dd65b..c4f09ac94fe 100644
--- a/compiler/noirc_evaluator/src/ssa/opt/preprocess_fns.rs
+++ b/compiler/noirc_evaluator/src/ssa/opt/preprocess_fns.rs
@@ -59,7 +59,7 @@ impl Ssa {
// Try to reduce the number of blocks.
function.simplify_function();
// Remove leftover instructions.
- function.dead_instruction_elimination(true, false);
+ function.dead_instruction_elimination(true, false, false);
// Put it back into the SSA, so the next functions can pick it up.
self.functions.insert(id, function);