Merge branch 'ab/unchecked-math' of github.com:noir-lang/noir into ab…

…/unchecked-math
noir-lang · Jan 10, 2025 · c10520c · c10520c
2 parents 7840ced + dfad378
commit c10520c
Show file tree

Hide file tree

Showing 2 changed files with 5 additions and 4 deletions.
diff --git a/compiler/noirc_evaluator/src/ssa/opt/remove_bit_shifts.rs b/compiler/noirc_evaluator/src/ssa/opt/remove_bit_shifts.rs
@@ -134,7 +134,7 @@ impl Context<'_> {
             let pow = self.pow(base, rhs);
             let pow = self.insert_cast(pow, typ);
 
-            // Unchecked mul because predicate is 0 or 1
+            // Unchecked mul because `predicate` will be 1 or 0
             (
                 FieldElement::max_num_bits(),
                 self.insert_binary(predicate, BinaryOp::Mul { unchecked: true }, pow),
@@ -218,8 +218,8 @@ impl Context<'_> {
             let rhs_bits = rhs_bits[0];
             let one = self.field_constant(FieldElement::one());
             let mut r = one;
+            // All operations are unchecked as we're acting on Field types (which are always unchecked)
             for i in 1..bit_size + 1 {
-                // All of these operations are unchecked because they deal with fields
                 let r_squared = self.insert_binary(r, BinaryOp::Mul { unchecked: true }, r);
                 let a = self.insert_binary(r_squared, BinaryOp::Mul { unchecked: true }, lhs);
                 let idx = self.field_constant(FieldElement::from((bit_size - i) as i128));

diff --git a/compiler/noirc_evaluator/src/ssa/ssa_gen/context.rs b/compiler/noirc_evaluator/src/ssa/ssa_gen/context.rs
@@ -329,6 +329,7 @@ impl<'a> FunctionContext<'a> {
             BinaryOp::Mul { unchecked: true },
             two_complement,
         );
+        // Unchecked addition because either `positive_predicate` or `negative_predicate` will be 0
         self.builder.insert_binary(
             positive_predicate,
             BinaryOp::Add { unchecked: true },
@@ -488,7 +489,7 @@ impl<'a> FunctionContext<'a> {
                 //Check the result has the same sign as its inputs
                 let result_sign = self.builder.insert_binary(result, BinaryOp::Lt, half_width);
                 let sign_diff = self.builder.insert_binary(result_sign, BinaryOp::Eq, lhs_sign);
-                // Unchecked mul because sign_diff is a boolean
+                // Unchecked multiplication because boolean inputs
                 let sign_diff_with_predicate = self.builder.insert_binary(
                     sign_diff,
                     BinaryOp::Mul { unchecked: true },
@@ -522,7 +523,7 @@ impl<'a> FunctionContext<'a> {
                 let not_same = self.builder.insert_not(same_sign);
                 let not_same_sign_field =
                     self.insert_safe_cast(not_same, NumericType::unsigned(bit_size), location);
-                // This shouldn't overflow so it's unchecked
+                // TODO: should this be unchecked?
                 let positive_maximum_with_offset = self.builder.insert_binary(
                     half_width,
                     BinaryOp::Add { unchecked: true },