feat: simplify constant MSM calls in SSA (#6547)

acvm-repo/bn254_blackbox_solver/src/embedded_curve_ops.rs

@@ -16,7 +16,6 @@ pub fn multi_scalar_mul(
     scalars_hi: &[FieldElement],
 ) -> Result<(FieldElement, FieldElement, FieldElement), BlackBoxResolutionError> {
     if points.len() != 3 * scalars_lo.len() || scalars_lo.len() != scalars_hi.len() {
-        dbg!(&points.len(), &scalars_lo.len(), &scalars_hi.len());
         return Err(BlackBoxResolutionError::Failed(
             BlackBoxFunc::MultiScalarMul,
             "Points and scalars must have the same length".to_string(),

compiler/noirc_evaluator/src/ssa/ir/instruction/call.rs

@@ -572,7 +572,9 @@ fn simplify_black_box_func(
             acvm::blackbox_solver::ecdsa_secp256r1_verify,
         ),
 
-        BlackBoxFunc::MultiScalarMul => SimplifyResult::None,
+        BlackBoxFunc::MultiScalarMul => {
+            blackbox::simplify_msm(dfg, solver, arguments, block, call_stack)
+        }
         BlackBoxFunc::EmbeddedCurveAdd => {
             blackbox::simplify_ec_add(dfg, solver, arguments, block, call_stack)
         }

compiler/noirc_evaluator/src/ssa/ir/instruction/call/blackbox.rs

@@ -63,6 +63,64 @@ pub(super) fn simplify_ec_add(
     }
 }
 
+pub(super) fn simplify_msm(
+    dfg: &mut DataFlowGraph,
+    solver: impl BlackBoxFunctionSolver<FieldElement>,
+    arguments: &[ValueId],
+    block: BasicBlockId,
+    call_stack: &CallStack,
+) -> SimplifyResult {
+    // TODO: Handle MSMs where a subset of the terms are constant.
+    match (dfg.get_array_constant(arguments[0]), dfg.get_array_constant(arguments[1])) {
+        (Some((points, _)), Some((scalars, _))) => {
+            let Some(points) = points
+                .into_iter()
+                .map(|id| dfg.get_numeric_constant(id))
+                .collect::<Option<Vec<_>>>()
+            else {
+                return SimplifyResult::None;
+            };
+
+            let Some(scalars) = scalars
+                .into_iter()
+                .map(|id| dfg.get_numeric_constant(id))
+                .collect::<Option<Vec<_>>>()
+            else {
+                return SimplifyResult::None;
+            };
+
+            let mut scalars_lo = Vec::new();
+            let mut scalars_hi = Vec::new();
+            for (i, scalar) in scalars.into_iter().enumerate() {
+                if i % 2 == 0 {
+                    scalars_lo.push(scalar);
+                } else {
+                    scalars_hi.push(scalar);
+                }
+            }
+
+            let Ok((result_x, result_y, result_is_infinity)) =
+                solver.multi_scalar_mul(&points, &scalars_lo, &scalars_hi)
+            else {
+                return SimplifyResult::None;
+            };
+
+            let result_x = dfg.make_constant(result_x, Type::field());
+            let result_y = dfg.make_constant(result_y, Type::field());
+            let result_is_infinity = dfg.make_constant(result_is_infinity, Type::bool());
+
+            let elements = im::vector![result_x, result_y, result_is_infinity];
+            let typ = Type::Array(Arc::new(vec![Type::field()]), 3);
+            let instruction = Instruction::MakeArray { elements, typ };
+            let result_array =
+                dfg.insert_instruction_and_results(instruction, block, None, call_stack.clone());
+
+            SimplifyResult::SimplifiedTo(result_array.first())
+        }
+        _ => SimplifyResult::None,
+    }
+}
+
 pub(super) fn simplify_poseidon2_permutation(
     dfg: &mut DataFlowGraph,
     solver: impl BlackBoxFunctionSolver<FieldElement>,

test_programs/compile_success_empty/embedded_curve_msm_simplification/Nargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "embedded_curve_msm_simplification"
+type = "bin"
+authors = [""]
+
+[dependencies]

test_programs/compile_success_empty/embedded_curve_msm_simplification/src/main.nr

@@ -0,0 +1,12 @@
+fn main() {
+    let pub_x = 0x0000000000000000000000000000000000000000000000000000000000000001;
+    let pub_y = 0x0000000000000002cf135e7506a45d632d270d45f1181294833fc48d823f272c;
+
+    let g1_y = 17631683881184975370165255887551781615748388533673675138860;
+    let g1 = std::embedded_curve_ops::EmbeddedCurvePoint { x: 1, y: g1_y, is_infinite: false };
+    let scalar = std::embedded_curve_ops::EmbeddedCurveScalar { lo: 1, hi: 0 };
+    // Test that multi_scalar_mul correctly derives the public key
+    let res = std::embedded_curve_ops::multi_scalar_mul([g1], [scalar]);
+    assert(res.x == pub_x);
+    assert(res.y == pub_y);
+}