add negative check the build_egcd_function

Author: FrancoGiachetta

src/libfuncs/circuit.rs

@@ -637,26 +637,6 @@ fn build_gate_evaluation<'ctx, 'this>(
                     ));
                     block = has_inverse_block;
 
-                    // if the inverse is negative, then add modulus
-                    let zero = block.const_int_from_type(context, location, 0, u768_type)?;
-                    let is_negative = block
-                        .append_operation(arith::cmpi(
-                            context,
-                            CmpiPredicate::Slt,
-                            inverse,
-                            zero,
-                            location,
-                        ))
-                        .result(0)?
-                        .into();
-                    let wrapped_inverse = block.addi(inverse, circuit_modulus_u768, location)?;
-                    let inverse = block.append_op_result(arith::select(
-                        is_negative,
-                        wrapped_inverse,
-                        inverse,
-                        location,
-                    ))?;
-
                     // Truncate back
                     let inverse = block.trunci(inverse, u384_type, location)?;
 

src/libfuncs/felt252.rs

@@ -21,7 +21,7 @@ use cairo_lang_sierra::{
 use melior::{
     dialect::arith::{self, CmpiPredicate},
     helpers::{ArithBlockExt, BuiltinBlockExt, LlvmBlockExt},
-    ir::{r#type::IntegerType, Block, BlockLike, Location, Value, ValueLike},
+    ir::{r#type::IntegerType, Block, Location, Value, ValueLike},
     Context,
 };
 use num_bigint::{BigInt, Sign};
@@ -168,30 +168,6 @@ pub fn build_binary_operation<'ctx, 'this>(
 
             let inverse = entry.extract_value(context, location, euclidean_result, i512, 1)?;
 
-            // egcd sometimes returns a negative number for the inverse,
-            // in such cases we must simply wrap it around back into [0, PRIME)
-            // this suffices because |inv_i| <= divfloor(PRIME,2)
-            let zero = entry.const_int_from_type(context, location, 0, i512)?;
-
-            let is_negative = entry
-                .append_operation(arith::cmpi(
-                    context,
-                    CmpiPredicate::Slt,
-                    inverse,
-                    zero,
-                    location,
-                ))
-                .result(0)?
-                .into();
-            // if the inverse is < 0, add PRIME
-            let wrapped_inverse = entry.addi(inverse, prime, location)?;
-            let inverse = entry.append_op_result(arith::select(
-                is_negative,
-                wrapped_inverse,
-                inverse,
-                location,
-            ))?;
-
             // Peform lhs * (1 / rhs)
             let result = entry.muli(lhs, inverse, location)?;
             // Apply modulo and convert result to felt252

src/metadata/runtime_bindings.rs

@@ -947,17 +947,37 @@ fn build_egcd_function<'ctx>(
         location,
     ));
 
+    let gcd = end_block.arg(0)?;
+    let inverse = end_block.arg(1)?;
+
+    // EGDC sometimes returns a negative number for the inverse,
+    // in such cases we must simply wrap it around back into [0, MODULUS)
+    // this suffices because |inv_i| <= divfloor(MODULUS,2)
+    let zero = end_block.const_int_from_type(context, location, 0, integer_type)?;
+    let is_negative = end_block
+        .append_operation(arith::cmpi(
+            context,
+            CmpiPredicate::Slt,
+            inverse,
+            zero,
+            location,
+        ))
+        .result(0)?
+        .into();
+    let wrapped_inverse = end_block.addi(inverse, b, location)?;
+    let inverse = end_block.append_op_result(arith::select(
+        is_negative,
+        wrapped_inverse,
+        inverse,
+        location,
+    ))?;
+
     // Create the struct that will contain the results
     let results = end_block.append_op_result(llvm::undef(
         llvm::r#type::r#struct(context, &[integer_type, integer_type], false),
         location,
     ))?;
-    let results = end_block.insert_values(
-        context,
-        location,
-        results,
-        &[end_block.arg(0)?, end_block.arg(1)?],
-    )?;
+    let results = end_block.insert_values(context, location, results, &[gcd, inverse])?;
     end_block.append_operation(llvm::r#return(Some(results), location));
 
     let func_name = StringAttribute::new(context, func_symbol);