Add more multiplication primitives

inc/zoo/swar/SWAR.h

@@ -258,6 +258,12 @@ constexpr auto horizontalEquality(SWAR<NBits, T> left, SWAR<NBits, T> right) {
     return left.m_v == right.m_v;
 }
 
+template <int NBits, typename T>
+constexpr static auto consumeMSB(SWAR<NBits, T> s) noexcept {
+    using S = SWAR<NBits, T>;
+    auto msbCleared = s & ~S{S::MostSignificantBit};
+    return S{static_cast<T>(msbCleared.value() << 1)};
+}
 
 
 #if ZOO_USE_LEASTNBITSMASK

inc/zoo/swar/associative_iteration.h

@@ -396,8 +396,7 @@ constexpr auto multiplication_OverflowUnsafe_SpecificBitCount(
     };
 
     auto halver = [](auto counts) {
-        auto msbCleared = counts & ~S{S::MostSignificantBit};
-        return S{msbCleared.value() << 1};
+        return swar::consumeMSB(counts);
     };
 
     auto shifted = S{multiplier.value() << (NB - ActualBits)};
@@ -539,8 +538,7 @@ constexpr auto saturatingExponentiation(
     };
 
     auto halver = [](auto counts) {
-        auto msbCleared = counts & ~S{S::MostSignificantBit};
-        return S{static_cast<T>(msbCleared.value() << 1)};
+        return swar::consumeMSB(counts);
     };
 
     return associativeOperatorIterated_regressive(