Very marginally reduce branching in Karatsuba multiplication

diff --git a/src/crypto/bigint.rs b/src/crypto/bigint.rs
index 578f5fcd586bc46024ee46dc79ddb285b6868333..8fe97c7d6f77de78b23dd567157bbbd903774be3 100644 (file)
--- a/src/crypto/bigint.rs
+++ b/src/crypto/bigint.rs
@@ -409,18 +409,14 @@ macro_rules! define_mul { ($name: ident, $len: expr, $submul: ident) => {
                let l = const_subslice(&z0, $len / 2, $len);
                let (k, j_carry) = add(z0_start, z1_end);
                let (mut j, i_carry_a) = add(z1_start, z2_end);
-               let mut i_carry_b = false;
-               if j_carry {
-                       i_carry_b = add_u64!(j, 1);
-               }
+               let i_carry_b = add_u64!(j, j_carry as u64);
+
                let mut i = [0; $len / 2];
                let i_source = const_subslice(&z2, 0, $len / 2);
                copy_from_slice!(i, 0, $len / 2, i_source);
                let i_carry = i_carry_a as u64 + i_carry_b as u64 + z1_carry as u64;
-               if i_carry != 0 {
-                       let must_not_overflow = add_u64!(i, i_carry);
-                       debug_assert!(!must_not_overflow, "Two N*64 bit numbers, multiplied, will not use more than 2*N*64 bits");
-               }
+               let must_not_overflow = add_u64!(i, i_carry);
+               debug_assert!(!must_not_overflow, "Two N*64 bit numbers, multiplied, will not use more than 2*N*64 bits");
 
                let mut res = [0; $len * 2];
                copy_from_slice!(res, $len * 2 * 0 / 4, $len * 2 * 1 / 4, i);