Luminarys commented on a change in pull request #8344:
URL: https://github.com/apache/arrow/pull/8344#discussion_r503538015
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File path: cpp/src/arrow/util/basic_decimal.cc
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@@ -254,67 +252,126 @@ BasicDecimal128& BasicDecimal128::operator>>=(uint32_t
bits) {
namespace {
-// TODO: Remove this guard once it's used by BasicDecimal256
-#ifndef ARROW_USE_NATIVE_INT128
-// This method losslessly multiplies x and y into a 128 bit unsigned integer
-// whose high bits will be stored in hi and low bits in lo.
-void ExtendAndMultiplyUint64(uint64_t x, uint64_t y, uint64_t* hi, uint64_t*
lo) {
-#ifdef ARROW_USE_NATIVE_INT128
- const __uint128_t r = static_cast<__uint128_t>(x) * y;
- *lo = r & kInt64Mask;
- *hi = r >> 64;
-#else
- // If we can't use a native fallback, perform multiplication
- // by splitting up x and y into 32 bit high/low bit components,
+// Multiply two N bit word components into a 2*N bit result, with high bits
+// stored in hi and low bits in lo.
+template <typename Word>
+inline void ExtendAndMultiplyUint(Word x, Word y, Word* hi, Word* lo) {
Review comment:
Done,
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