AK: Delete unused and untested sqrt, pow and pow_mod from UFixedBigInt

Author: https://github.com/DanShaders
Commit: https://github.com/SerenityOS/serenity/commit/2470fab05e
Pull-request: https://github.com/SerenityOS/serenity/pull/17330
Reviewed-by: https://github.com/ADKaster
Reviewed-by: https://github.com/Hendiadyoin1

AK/UFixedBigInt.h

@@ -475,130 +475,8 @@ public:
         return *this;
     }
 
-    constexpr R sqrt() const
-    {
-        // Bitwise method: https://en.wikipedia.org/wiki/Integer_square_root#Using_bitwise_operations
-        // the bitwise method seems to be way faster then Newtons:
-        // https://quick-bench.com/q/eXZwW1DVhZxLE0llumeCXkfOK3Q
-        if (*this == 1u)
-            return 1u;
-
-        ssize_t shift = (sizeof(R) * 8 - clz()) & ~1ULL;
-        // should be equivalent to:
-        // long shift = 2;
-        // while ((val >> shift) != 0)
-        //   shift += 2;
-
-        R res = 0u;
-        while (shift >= 0) {
-            res = res << 1u;
-            R large_cand = (res | 1u);
-            if (*this >> (size_t)shift >= large_cand * large_cand)
-                res = large_cand;
-            shift -= 2;
-        }
-        return res;
-    }
-
-    constexpr R pow(u64 exp)
-    {
-        // Montgomery's Ladder Technique
-        // https://en.wikipedia.org/wiki/Exponentiation_by_squaring#Montgomery's_ladder_technique
-        R x1 = *this;
-        R x2 = *this * *this;
-        u64 exp_copy = exp;
-        for (ssize_t i = sizeof(u64) * 8 - count_leading_zeroes(exp) - 2; i >= 0; --i) {
-            if (exp_copy & 1u) {
-                x2 *= x1;
-                x1 *= x1;
-            } else {
-                x1 *= x2;
-                x2 *= x2;
-            }
-            exp_copy >>= 1u;
-        }
-        return x1;
-    }
-    template<Unsigned U>
-    requires(sizeof(U) > sizeof(u64)) constexpr R pow(U exp)
-    {
-        // Montgomery's Ladder Technique
-        // https://en.wikipedia.org/wiki/Exponentiation_by_squaring#Montgomery's_ladder_technique
-        R x1 = *this;
-        R x2 = *this * *this;
-        U exp_copy = exp;
-        for (ssize_t i = sizeof(U) * 8 - exp().clz() - 2; i >= 0; --i) {
-            if (exp_copy & 1u) {
-                x2 *= x1;
-                x1 *= x1;
-            } else {
-                x1 *= x2;
-                x2 *= x2;
-            }
-            exp_copy >>= 1u;
-        }
-        return x1;
-    }
-
-    template<Unsigned U>
-    constexpr U pow_mod(u64 exp, U mod)
-    {
-        // Left to right binary method:
-        // https://en.wikipedia.org/wiki/Modular_exponentiation#Left-to-right_binary_method
-        // FIXME: this is not sidechanel proof
-        if (!mod)
-            return 0u;
-
-        U res = 1;
-        u64 exp_copy = exp;
-        for (size_t i = sizeof(u64) - count_leading_zeroes(exp) - 1u; i < exp; ++i) {
-            res *= res;
-            res %= mod;
-            if (exp_copy & 1u) {
-                res = (*this * res) % mod;
-            }
-            exp_copy >>= 1u;
-        }
-        return res;
-    }
-    template<Unsigned ExpT, Unsigned U>
-    requires(sizeof(ExpT) > sizeof(u64)) constexpr U pow_mod(ExpT exp, U mod)
-    {
-        // Left to right binary method:
-        // https://en.wikipedia.org/wiki/Modular_exponentiation#Left-to-right_binary_method
-        // FIXME: this is not side channel proof
-        if (!mod)
-            return 0u;
-
-        U res = 1;
-        ExpT exp_copy = exp;
-        for (size_t i = sizeof(ExpT) - exp.clz() - 1u; i < exp; ++i) {
-            res *= res;
-            res %= mod;
-            if (exp_copy & 1u) {
-                res = (*this * res) % mod;
-            }
-            exp_copy >>= 1u;
-        }
-        return res;
-    }
-
-    constexpr size_t log2()
-    {
-        // FIXME: proper rounding
-        return sizeof(R) - clz();
-    }
-    constexpr size_t logn(u64 base)
-    {
-        // FIXME: proper rounding
-        return log2() / (sizeof(u64) - count_leading_zeroes(base));
-    }
-    template<Unsigned U>
-    requires(sizeof(U) > sizeof(u64)) constexpr size_t logn(U base)
-    {
-        // FIXME: proper rounding
-        return log2() / base.log2();
-    }
+    // Note: If there ever be need for non side-channel proof sqrt/pow/pow_mod of UFixedBigInt, you
+    //       can restore them from Git history.
 
 #undef DEFINE_STANDARD_BINARY_OPERATOR
 #undef DEFINE_STANDARD_COMPOUND_ASSIGNMENT

Tests/AK/TestUFixedBigInt.cpp

@@ -39,15 +39,6 @@ TEST_CASE(identities)
     }
 }
 
-TEST_CASE(sqrt)
-{
-    srand(0);
-    for (int i = 0; i < test_iterations; ++i) {
-        u256 x = get_random<u128>();
-        EXPECT_EQ((x * x).sqrt(), x);
-    }
-}
-
 TEST_CASE(add_overflow_propagation)
 {
     u256 a = NumericLimits<u128>::max();