implement circuit_single_limb_less_than_guarantee_verify (#1212)

* implement circuit_single_limb_less_than_guarantee_verify

* fmt

* clippy

* Fix comment

Co-authored-by: Julian Gonzalez Calderon <gonzalezcalderonjulian@gmail.com>

---------

Co-authored-by: Julian Gonzalez Calderon <gonzalezcalderonjulian@gmail.com>
Co-authored-by: Gabriel Bosio <38794644+gabrielbosio@users.noreply.github.com>

Author: 3 people

src/libfuncs/circuit.rs

@@ -71,10 +71,12 @@ pub fn build<'ctx, 'this>(
         CircuitConcreteLibfunc::IntoU96Guarantee(info) => {
             build_into_u96_guarantee(context, registry, entry, location, helper, metadata, info)
         }
-        CircuitConcreteLibfunc::U96SingleLimbLessThanGuaranteeVerify(
-            SignatureOnlyConcreteLibfunc { signature, .. },
-        )
-        | CircuitConcreteLibfunc::U96GuaranteeVerify(SignatureOnlyConcreteLibfunc { signature }) => {
+        CircuitConcreteLibfunc::U96SingleLimbLessThanGuaranteeVerify(info) => {
+            build_u96_single_limb_less_than_guarantee_verify(
+                context, registry, entry, location, helper, metadata, info,
+            )
+        }
+        CircuitConcreteLibfunc::U96GuaranteeVerify(SignatureOnlyConcreteLibfunc { signature }) => {
             super::build_noop::<1, true>(
                 context,
                 registry,
@@ -821,6 +823,37 @@ fn build_u96_limbs_less_than_guarantee_verify<'ctx, 'this>(
     Ok(())
 }
 
+fn build_u96_single_limb_less_than_guarantee_verify<'ctx, 'this>(
+    context: &'ctx Context,
+    _registry: &ProgramRegistry<CoreType, CoreLibfunc>,
+    entry: &'this Block<'ctx>,
+    location: Location<'ctx>,
+    helper: &LibfuncHelper<'ctx, 'this>,
+    _metadata: &mut MetadataStorage,
+    _info: &SignatureOnlyConcreteLibfunc,
+) -> Result<()> {
+    let guarantee = entry.arg(0)?;
+
+    let u96_type = IntegerType::new(context, 96).into();
+    // this libfunc will always receive gate and modulus with single limb
+    let limb_struct_type = llvm::r#type::r#struct(context, &[u96_type; 1], false);
+
+    // extract gate and modulus from input value
+    let gate = entry.extract_value(context, location, guarantee, limb_struct_type, 0)?;
+    let modulus = entry.extract_value(context, location, guarantee, limb_struct_type, 1)?;
+
+    // extract the only limb from gate and modulus
+    let gate_limb = entry.extract_value(context, location, gate, u96_type, 0)?;
+    let modulus_limb = entry.extract_value(context, location, modulus, u96_type, 0)?;
+
+    // calcualte diff between limbs
+    let diff = entry.append_op_result(arith::subi(modulus_limb, gate_limb, location))?;
+
+    entry.append_operation(helper.br(0, &[diff], location));
+
+    Ok(())
+}
+
 /// Generate MLIR operations for the `get_circuit_output` libfunc.
 #[allow(clippy::too_many_arguments)]
 fn build_get_output<'ctx, 'this>(