Minor optimizations for BigInt operator/

Detect divisions by small powers of 2

1 files changed, 6 insertions, 0 deletions

diff --git a/src/lib/math/bigint/big_ops3.cpp b/src/lib/math/bigint/big_ops3.cpp
index 48d84c8b4..eed8a29a0 100644
--- a/src/lib/math/bigint/big_ops3.cpp
+++ b/src/lib/math/bigint/big_ops3.cpp
@@ -107,6 +107,9 @@ BigInt operator*(const BigInt& x, const BigInt& y)
 */
 BigInt operator/(const BigInt& x, const BigInt& y)
    {
+   if(y.sig_words() == 1 && is_power_of_2(y.word_at(0)))
+      return (x >> (y.bits() - 1));
+
    BigInt q, r;
    divide(x, y, q, r);
    return q;
@@ -137,6 +140,9 @@ word operator%(const BigInt& n, word mod)
    if(mod == 0)
       throw BigInt::DivideByZero();
 
+   if(mod == 1)
+      return 0;
+
    if(is_power_of_2(mod))
       return (n.word_at(0) & (mod - 1));