Don't emit unchecked operations for Fields, or when multiplying bools

compiler/noirc_evaluator/src/ssa/function_builder/mod.rs

@@ -251,14 +251,6 @@ impl FunctionBuilder {
         operator: BinaryOp,
         rhs: ValueId,
     ) -> ValueId {
-        let lhs_type = self.type_of_value(lhs);
-        let rhs_type = self.type_of_value(rhs);
-        if operator != BinaryOp::Shl && operator != BinaryOp::Shr {
-            assert_eq!(
-                lhs_type, rhs_type,
-                "ICE - Binary instruction operands must have the same type"
-            );
-        }
         let instruction = Instruction::Binary(Binary { lhs, rhs, operator });
         self.insert_instruction(instruction, None).first()
     }

compiler/noirc_evaluator/src/ssa/ir/dfg.rs

@@ -7,7 +7,8 @@ use super::{
     call_stack::{CallStack, CallStackHelper, CallStackId},
     function::{FunctionId, RuntimeType},
     instruction::{
-        Instruction, InstructionId, InstructionResultType, Intrinsic, TerminatorInstruction,
+        Binary, BinaryOp, Instruction, InstructionId, InstructionResultType, Intrinsic,
+        TerminatorInstruction,
     },
     map::DenseMap,
     types::{NumericType, Type},
@@ -174,6 +175,44 @@ impl DataFlowGraph {
         instruction_data: Instruction,
         ctrl_typevars: Option<Vec<Type>>,
     ) -> InstructionId {
+        let instruction_data = if let Instruction::Binary(binary) = instruction_data {
+            let lhs = binary.lhs;
+            let rhs = binary.rhs;
+            let operator = binary.operator;
+            let lhs_type = self.type_of_value(lhs);
+            let rhs_type = self.type_of_value(rhs);
+            if operator != BinaryOp::Shl && operator != BinaryOp::Shr {
+                assert_eq!(
+                    lhs_type, rhs_type,
+                    "ICE - Binary instruction operands must have the same type"
+                );
+            }
+
+            let operator = if lhs_type.is_field() {
+                // Unchecked operations between fields or bools don't make sense, so we convert those to non-unchecked
+                // to reduce noise and confusion in the generated SSA.
+                match operator {
+                    BinaryOp::Add { unchecked: true } => BinaryOp::Add { unchecked: false },
+                    BinaryOp::Sub { unchecked: true } => BinaryOp::Sub { unchecked: false },
+                    BinaryOp::Mul { unchecked: true } => BinaryOp::Mul { unchecked: false },
+                    _ => operator,
+                }
+            } else if lhs_type.is_bool() {
+                // Unchecked mul between bools doesn't make sense, so we convert that to non-unchecked
+                if let BinaryOp::Mul { unchecked: true } = operator {
+                    BinaryOp::Mul { unchecked: false }
+                } else {
+                    operator
+                }
+            } else {
+                operator
+            };
+
+            Instruction::Binary(Binary { operator, ..binary })
+        } else {
+            instruction_data
+        };
+
         let id = self.instructions.insert(instruction_data);
         self.make_instruction_results(id, ctrl_typevars);
         id

compiler/noirc_evaluator/src/ssa/ir/types.rs

@@ -119,6 +119,16 @@ impl Type {
         matches!(self, Type::Numeric(NumericType::Unsigned { .. }))
     }
 
+    /// Returns whether the `Type` represents the Field type.
+    pub(crate) fn is_field(&self) -> bool {
+        matches!(self, Type::Numeric(NumericType::NativeField))
+    }
+
+    /// Returns whether the `Type` is `u1`
+    pub(crate) fn is_bool(&self) -> bool {
+        matches!(self, Type::Numeric(NumericType::Unsigned { bit_size: 1 }))
+    }
+
     /// Create a new signed integer type with the given amount of bits.
     pub(crate) fn signed(bit_size: u32) -> Type {
         Type::Numeric(NumericType::Signed { bit_size })

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

@@ -850,9 +850,9 @@ mod test {
                 enable_side_effects u1 1
                 v3 = cast v0 as Field
                 v4 = cast v1 as Field
-                v6 = unchecked_mul v3, Field 3
-                v8 = unchecked_mul v4, Field 4
-                v9 = unchecked_add v6, v8
+                v6 = mul v3, Field 3
+                v8 = mul v4, Field 4
+                v9 = add v6, v8
                 return v9
             }
             ";
@@ -881,7 +881,7 @@ mod test {
             acir(inline) fn main f0 {
               b0(v0: u1, v1: u1):
                 enable_side_effects v0
-                v2 = unchecked_mul v1, v0
+                v2 = mul v1, v0
                 constrain v2 == v0
                 v3 = not v0
                 enable_side_effects u1 1
@@ -916,9 +916,9 @@ mod test {
                 v3 = not v0
                 v4 = cast v0 as Field
                 v5 = cast v3 as Field
-                v7 = unchecked_mul v4, Field 5
-                v8 = unchecked_mul v5, v2
-                v9 = unchecked_add v7, v8
+                v7 = mul v4, Field 5
+                v8 = mul v5, v2
+                v9 = add v7, v8
                 store v9 at v1
                 enable_side_effects u1 1
                 return
@@ -954,17 +954,17 @@ mod test {
                 v3 = not v0
                 v4 = cast v0 as Field
                 v5 = cast v3 as Field
-                v7 = unchecked_mul v4, Field 5
-                v8 = unchecked_mul v5, v2
-                v9 = unchecked_add v7, v8
+                v7 = mul v4, Field 5
+                v8 = mul v5, v2
+                v9 = add v7, v8
                 store v9 at v1
                 enable_side_effects v3
                 v10 = load v1 -> Field
                 v11 = cast v3 as Field
                 v12 = cast v0 as Field
-                v14 = unchecked_mul v11, Field 6
-                v15 = unchecked_mul v12, v10
-                v16 = unchecked_add v14, v15
+                v14 = mul v11, Field 6
+                v15 = mul v12, v10
+                v16 = add v14, v15
                 store v16 at v1
                 enable_side_effects u1 1
                 return
@@ -1066,32 +1066,32 @@ mod test {
             v3 = not v0
             v4 = cast v0 as Field
             v5 = cast v3 as Field
-            v7 = unchecked_mul v4, Field 2
-            v8 = unchecked_add v7, v5
-            v9 = unchecked_mul v0, v1
+            v7 = mul v4, Field 2
+            v8 = add v7, v5
+            v9 = mul v0, v1
             enable_side_effects v9
             v10 = not v9
             v11 = cast v9 as Field
             v12 = cast v10 as Field
-            v14 = unchecked_mul v11, Field 5
-            v15 = unchecked_mul v12, v8
-            v16 = unchecked_add v14, v15
+            v14 = mul v11, Field 5
+            v15 = mul v12, v8
+            v16 = add v14, v15
             v17 = not v1
-            v18 = unchecked_mul v0, v17
+            v18 = mul v0, v17
             enable_side_effects v18
             v19 = not v18
             v20 = cast v18 as Field
             v21 = cast v19 as Field
-            v23 = unchecked_mul v20, Field 6
-            v24 = unchecked_mul v21, v16
-            v25 = unchecked_add v23, v24
+            v23 = mul v20, Field 6
+            v24 = mul v21, v16
+            v25 = add v23, v24
             enable_side_effects v0
             enable_side_effects v3
             v26 = cast v3 as Field
             v27 = cast v0 as Field
-            v29 = unchecked_mul v26, Field 3
-            v30 = unchecked_mul v27, v25
-            v31 = unchecked_add v29, v30
+            v29 = mul v26, Field 3
+            v30 = mul v27, v25
+            v31 = add v29, v30
             enable_side_effects u1 1
             return v31
         }";
@@ -1446,9 +1446,9 @@ mod test {
             v2 = not v0
             v3 = cast v0 as Field
             v4 = cast v2 as Field
-            v6 = unchecked_mul v3, Field 2
-            v7 = unchecked_mul v4, v3
-            v8 = unchecked_add v6, v7
+            v6 = mul v3, Field 2
+            v7 = mul v4, v3
+            v8 = add v6, v7
             enable_side_effects u1 1
             return v8
         }
@@ -1491,7 +1491,7 @@ mod test {
           b0(v0: u1, v1: u1):
             enable_side_effects v0
             v2 = cast v0 as Field
-            v4 = unchecked_mul v2, Field 2
+            v4 = mul v2, Field 2
             v5 = make_array [v4] : [Field; 1]
             enable_side_effects u1 1
             return v5

compiler/noirc_evaluator/src/ssa/parser/tests.rs

@@ -346,7 +346,7 @@ fn test_binary() {
         let src = format!(
             "
             acir(inline) fn main f0 {{
-              b0(v0: Field, v1: Field):
+              b0(v0: u32, v1: u32):
                 v2 = {op} v0, v1
                 return
             }}