chore: reduce number of iterations of acvm::compiler::compile (#7050)

acvm-repo/acvm/src/compiler/mod.rs

@@ -16,10 +16,6 @@ pub use simulator::CircuitSimulator;
 use transformers::transform_internal;
 pub use transformers::{transform, MIN_EXPRESSION_WIDTH};
 
-/// We need multiple passes to stabilize the output.
-/// The value was determined by running tests.
-const MAX_OPTIMIZER_PASSES: usize = 3;
-
 /// This module moves and decomposes acir opcodes. The transformation map allows consumers of this module to map
 /// metadata they had about the opcodes to the new opcode structure generated after the transformation.
 #[derive(Debug)]
@@ -84,41 +80,10 @@ pub fn compile<F: AcirField>(
 ) -> (Circuit<F>, AcirTransformationMap) {
     let acir_opcode_positions = (0..acir.opcodes.len()).collect::<Vec<_>>();
 
-    if MAX_OPTIMIZER_PASSES == 0 {
-        return (acir, AcirTransformationMap::new(&acir_opcode_positions));
-    }
-
-    let mut pass = 0;
-    let mut prev_opcodes_hash = fxhash::hash64(&acir.opcodes);
-    let mut prev_acir = acir;
-    let mut prev_acir_opcode_positions = acir_opcode_positions;
-
-    // For most test programs it would be enough to only loop `transform_internal`,
-    // but some of them don't stabilize unless we also repeat the backend agnostic optimizations.
-    let (mut acir, acir_opcode_positions) = loop {
-        let (acir, acir_opcode_positions) =
-            optimize_internal(prev_acir, prev_acir_opcode_positions);
-
-        // Stop if we have already done at least one transform and an extra optimization changed nothing.
-        if pass > 0 && prev_opcodes_hash == fxhash::hash64(&acir.opcodes) {
-            break (acir, acir_opcode_positions);
-        }
-
-        let (acir, acir_opcode_positions) =
-            transform_internal(acir, expression_width, acir_opcode_positions);
-
-        let opcodes_hash = fxhash::hash64(&acir.opcodes);
-
-        // Stop if the output hasn't change in this loop or we went too long.
-        if pass == MAX_OPTIMIZER_PASSES - 1 || prev_opcodes_hash == opcodes_hash {
-            break (acir, acir_opcode_positions);
-        }
+    let (acir, acir_opcode_positions) = optimize_internal(acir, acir_opcode_positions);
 
-        pass += 1;
-        prev_acir = acir;
-        prev_opcodes_hash = opcodes_hash;
-        prev_acir_opcode_positions = acir_opcode_positions;
-    };
+    let (mut acir, acir_opcode_positions) =
+        transform_internal(acir, expression_width, acir_opcode_positions);
 
     let transformation_map = AcirTransformationMap::new(&acir_opcode_positions);
     acir.assert_messages = transform_assert_messages(acir.assert_messages, &transformation_map);

acvm-repo/acvm/src/compiler/transformers/mod.rs

@@ -14,12 +14,17 @@ mod csat;
 
 pub(crate) use csat::CSatTransformer;
 pub use csat::MIN_EXPRESSION_WIDTH;
+use tracing::info;
 
 use super::{
-    optimizers::MergeExpressionsOptimizer, transform_assert_messages, AcirTransformationMap,
-    MAX_OPTIMIZER_PASSES,
+    optimizers::{MergeExpressionsOptimizer, RangeOptimizer},
+    transform_assert_messages, AcirTransformationMap,
 };
 
+/// We need multiple passes to stabilize the output.
+/// The value was determined by running tests.
+const MAX_TRANSFORMER_PASSES: usize = 3;
+
 /// Applies [`ProofSystemCompiler`][crate::ProofSystemCompiler] specific optimizations to a [`Circuit`].
 pub fn transform<F: AcirField>(
     acir: Circuit<F>,
@@ -50,12 +55,18 @@ pub(super) fn transform_internal<F: AcirField>(
     expression_width: ExpressionWidth,
     mut acir_opcode_positions: Vec<usize>,
 ) -> (Circuit<F>, Vec<usize>) {
+    if acir.opcodes.len() == 1 && matches!(acir.opcodes[0], Opcode::BrilligCall { .. }) {
+        info!("Program is fully unconstrained, skipping transformation pass");
+        return (acir, acir_opcode_positions);
+    }
+
     // Allow multiple passes until we have stable output.
     let mut prev_opcodes_hash = fxhash::hash64(&acir.opcodes);
 
     // For most test programs it would be enough to loop here, but some of them
     // don't stabilize unless we also repeat the backend agnostic optimizations.
-    for _ in 0..MAX_OPTIMIZER_PASSES {
+    for _ in 0..MAX_TRANSFORMER_PASSES {
+        info!("Number of opcodes {}", acir.opcodes.len());
         let (new_acir, new_acir_opcode_positions) =
             transform_internal_once(acir, expression_width, acir_opcode_positions);
 
@@ -217,6 +228,12 @@ fn transform_internal_once<F: AcirField>(
         ..acir
     };
 
+    // The `MergeOptimizer` can merge two witnesses which have range opcodes applied to them
+    // so we run the `RangeOptimizer` afterwards to clear these up.
+    let range_optimizer = RangeOptimizer::new(acir);
+    let (acir, new_acir_opcode_positions) =
+        range_optimizer.replace_redundant_ranges(new_acir_opcode_positions);
+
     (acir, new_acir_opcode_positions)
 }