chore!: change ec_add to unsafe implementation (but much better perf) (…

…#8374)

Use `unconditional_add` for ec_add ACIR opcode.
This improves a lot the performance of the opcode, but also makes it
unsafe.
~~I keep the PR as draft until aztec packages are sync with Noir PR
noir-lang/noir#5858 which adds the checks in the
stdlib function.~~
The unsafe version can then be used when we know the inputs are valid
(for instance if they come from a previous add).
n.b.: the real performance boost will happen when we will be able to use
the unsafe version.

Co-authored-by: Tom French <[email protected]>

barretenberg/cpp/src/barretenberg/dsl/acir_format/ec_operations.cpp

@@ -7,6 +7,11 @@
 
 namespace acir_format {
 
+// This functions assumes that:
+// 1. none of the points are infinity
+// 2. the points are on the curve
+// 3a. the points have not the same abssissa, OR
+// 3b. the points are identical (same witness index or same value)
 template <typename Builder>
 void create_ec_add_constraint(Builder& builder, const EcAdd& input, bool has_valid_witness_assignments)
 {
@@ -19,7 +24,32 @@ void create_ec_add_constraint(Builder& builder, const EcAdd& input, bool has_val
         input.input2_x, input.input2_y, input.input2_infinite, has_valid_witness_assignments, builder);
 
     // Addition
-    cycle_group_ct result = input1_point + input2_point;
+    // Check if operands are the same
+    bool x_match = false;
+    if (!input1_point.x.is_constant() && !input2_point.x.is_constant()) {
+        x_match = (input1_point.x.get_witness_index() == input2_point.x.get_witness_index());
+    } else {
+        if (input1_point.x.is_constant() && input2_point.x.is_constant()) {
+            x_match = (input1_point.x.get_value() == input2_point.x.get_value());
+        }
+    }
+    bool y_match = false;
+    if (!input1_point.y.is_constant() && !input2_point.y.is_constant()) {
+        y_match = (input1_point.y.get_witness_index() == input2_point.y.get_witness_index());
+    } else {
+        if (input1_point.y.is_constant() && input2_point.y.is_constant()) {
+            y_match = (input1_point.y.get_value() == input2_point.y.get_value());
+        }
+    }
+
+    cycle_group_ct result;
+    // If operands are the same, we double.
+    if (x_match && y_match) {
+        result = input1_point.dbl();
+    } else {
+        result = input1_point.unconditional_add(input2_point);
+    }
+
     cycle_group_ct standard_result = result.get_standard_form();
     auto x_normalized = standard_result.x.normalize();
     auto y_normalized = standard_result.y.normalize();
@@ -35,6 +65,8 @@ void create_ec_add_constraint(Builder& builder, const EcAdd& input, bool has_val
     } else {
         builder.assert_equal(y_normalized.witness_index, input.result_y);
     }
+    // TODO: remove the infinite result, because the function should always return a non-zero point.
+    // But this requires an ACIR serialisation change and it will be done in a subsequent PR.
     if (infinite.is_constant()) {
         builder.fix_witness(input.result_infinite, infinite.get_value());
     } else {

barretenberg/cpp/src/barretenberg/dsl/acir_format/witness_constant.cpp

@@ -12,10 +12,17 @@ bb::stdlib::cycle_group<Builder> to_grumpkin_point(const WitnessOrConstant<FF>&
                                                    bool has_valid_witness_assignments,
                                                    Builder& builder)
 {
-    using bool_ct = bb::stdlib::bool_t<Builder>;
     auto point_x = to_field_ct(input_x, builder);
     auto point_y = to_field_ct(input_y, builder);
-    auto infinite = bool_ct(to_field_ct(input_infinite, builder));
+    // We assume input_infinite is boolean, so we do not add a boolean gate
+    bool_t infinite(&builder);
+    if (!input_infinite.is_constant) {
+        infinite.witness_index = input_infinite.index;
+        infinite.witness_bool = get_value(input_infinite, builder) == FF::one();
+    } else {
+        infinite.witness_index = IS_CONSTANT;
+        infinite.witness_bool = input_infinite.value == FF::one();
+    }
 
     // When we do not have the witness assignments, we set is_infinite value to true if it is not constant
     // else default values would give a point which is not on the curve and this will fail verification

barretenberg/cpp/src/barretenberg/dsl/acir_format/witness_constant.hpp

@@ -39,4 +39,12 @@ bb::stdlib::cycle_group<Builder> to_grumpkin_point(const WitnessOrConstant<FF>&
                                                    bool has_valid_witness_assignments,
                                                    Builder& builder);
 
+template <typename Builder, typename FF> FF get_value(const WitnessOrConstant<FF>& input, Builder& builder)
+{
+    if (input.is_constant) {
+        return input.value;
+    }
+    return builder.variables[input.index];
+}
+
 } // namespace acir_format