feat: add native u128 type (#7301)

Co-authored-by: kashbrti <kashbrti@gmail.com>
Co-authored-by: Ary Borenszweig <asterite@gmail.com>

compiler/noirc_evaluator/src/acir/acir_variable.rs

@@ -777,7 +777,8 @@ impl<F: AcirField, B: BlackBoxFunctionSolver<F>> AcirContext<F, B> {
     pub(crate) fn not_var(&mut self, x: AcirVar, typ: AcirType) -> Result<AcirVar, RuntimeError> {
         let bit_size = typ.bit_size::<F>();
         // Subtracting from max flips the bits
-        let max = self.add_constant((1_u128 << bit_size) - 1);
+        let max = power_of_two::<F>(bit_size) - F::one();
+        let max = self.add_constant(max);
         self.sub_var(max, x)
     }
 
@@ -908,19 +909,9 @@ impl<F: AcirField, B: BlackBoxFunctionSolver<F>> AcirContext<F, B> {
         self.assert_eq_var(lhs_constraint, rhs_constraint, None)?;
 
         // Avoids overflow: 'q*b+r < 2^max_q_bits*2^max_rhs_bits'
-        let mut avoid_overflow = false;
         if max_q_bits + max_rhs_bits >= F::max_num_bits() - 1 {
             // q*b+r can overflow; we avoid this when b is constant
-            if rhs_expr.is_const() {
-                avoid_overflow = true;
-            } else {
-                // we do not support unbounded division
-                unreachable!("overflow in unbounded division");
-            }
-        }
-
-        if let Some(rhs_const) = rhs_expr.to_const() {
-            if avoid_overflow {
+            if let Some(rhs_const) = rhs_expr.to_const() {
                 // we compute q0 = p/rhs
                 let rhs_big = BigUint::from_bytes_be(&rhs_const.to_be_bytes());
                 let q0_big = F::modulus() / &rhs_big;
@@ -944,6 +935,20 @@ impl<F: AcirField, B: BlackBoxFunctionSolver<F>> AcirContext<F, B> {
                     predicate,
                     rhs_const.num_bits(),
                 )?;
+            } else if bit_size == 128 {
+                // q and b are u128 and q*b could overflow so we check that either q or b are less than 2^64
+                let two_pow_64: F = power_of_two(64);
+                let two_pow_64 = self.add_constant(two_pow_64);
+
+                let (q_upper, _) =
+                    self.euclidean_division_var(quotient_var, two_pow_64, bit_size, predicate)?;
+                let (rhs_upper, _) =
+                    self.euclidean_division_var(rhs, two_pow_64, bit_size, predicate)?;
+                let mul_uppers = self.mul_var(q_upper, rhs_upper)?;
+                self.assert_eq_var(mul_uppers, zero, None)?;
+            } else {
+                // we do not support unbounded division
+                unreachable!("overflow in unbounded division");
             }
         }
 

compiler/noirc_evaluator/src/acir/mod.rs

@@ -1973,26 +1973,7 @@ impl<'a> Context<'a> {
     ) -> Result<AcirVar, RuntimeError> {
         let lhs = self.convert_numeric_value(binary.lhs, dfg)?;
         let rhs = self.convert_numeric_value(binary.rhs, dfg)?;
-
         let binary_type = self.type_of_binary_operation(binary, dfg);
-        match &binary_type {
-            Type::Numeric(NumericType::Unsigned { bit_size })
-            | Type::Numeric(NumericType::Signed { bit_size }) => {
-                // Conservative max bit size that is small enough such that two operands can be
-                // multiplied and still fit within the field modulus. This is necessary for the
-                // truncation technique: result % 2^bit_size to be valid.
-                let max_integer_bit_size = FieldElement::max_num_bits() / 2;
-                if *bit_size > max_integer_bit_size {
-                    return Err(RuntimeError::UnsupportedIntegerSize {
-                        num_bits: *bit_size,
-                        max_num_bits: max_integer_bit_size,
-                        call_stack: self.acir_context.get_call_stack(),
-                    });
-                }
-            }
-            _ => {}
-        }
-
         let binary_type = AcirType::from(binary_type);
         let bit_count = binary_type.bit_size::<FieldElement>();
         let num_type = binary_type.to_numeric_type();

compiler/noirc_evaluator/src/ssa.rs

@@ -214,6 +214,7 @@ fn optimize_all(builder: SsaBuilder, options: &SsaEvaluatorOptions) -> Result<Ss
         .run_pass(Ssa::remove_enable_side_effects, "EnableSideEffectsIf removal")
         .run_pass(Ssa::fold_constants_using_constraints, "Constraint Folding")
         .run_pass(Ssa::make_constrain_not_equal_instructions, "Adding constrain not equal")
+        .run_pass(Ssa::check_u128_mul_overflow, "Check u128 mul overflow")
         .run_pass(Ssa::dead_instruction_elimination, "Dead Instruction Elimination (1st)")
         .run_pass(Ssa::simplify_cfg, "Simplifying (3rd):")
         .run_pass(Ssa::array_set_optimization, "Array Set Optimizations")

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

@@ -1,4 +1,4 @@
-use binary::truncate_field;
+use binary::{truncate, truncate_field};
 use serde::{Deserialize, Serialize};
 use std::hash::{Hash, Hasher};
 
@@ -911,8 +911,10 @@ impl Instruction {
                     // would be incorrect however since the extra bits on the field would not be flipped.
                     Value::NumericConstant { constant, typ } if typ.is_unsigned() => {
                         // As we're casting to a `u128`, we need to clear out any upper bits that the NOT fills.
-                        let value = !constant.to_u128() % (1 << typ.bit_size());
-                        SimplifiedTo(dfg.make_constant(value.into(), *typ))
+                        let bit_size = typ.bit_size();
+                        assert!(bit_size <= 128);
+                        let not_value: u128 = truncate(!constant.to_u128(), bit_size);
+                        SimplifiedTo(dfg.make_constant(not_value.into(), *typ))
                     }
                     Value::Instruction { instruction, .. } => {
                         // !!v => v

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

@@ -509,7 +509,7 @@ fn convert_signed_integer_to_field_element(int: i128, bit_size: u32) -> FieldEle
 }
 
 /// Truncates `int` to fit within `bit_size` bits.
-fn truncate(int: u128, bit_size: u32) -> u128 {
+pub(super) fn truncate(int: u128, bit_size: u32) -> u128 {
     if bit_size == 128 {
         int
     } else {

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

@@ -65,7 +65,7 @@ impl NumericType {
     ) -> Option<String> {
         match self {
             NumericType::Unsigned { bit_size } => {
-                let max = 2u128.pow(bit_size) - 1;
+                let max = if bit_size == 128 { u128::MAX } else { 2u128.pow(bit_size) - 1 };
                 if negative {
                     return Some(format!("0..={}", max));
                 }