On Fri, 2 Jul 2021 09:37:47 GMT, Andrew Haley <a...@openjdk.org> wrote:
>> Brian Burkhalter has updated the pull request incrementally with one >> additional commit since the last revision: >> >> 8188044: Add @see links between multiplyHigh() and unsignedMultiplyHigh(). > > src/java.base/share/classes/java/lang/Math.java line 1211: > >> 1209: long z1 = t >>> 32; >> 1210: >> 1211: return x1 * y1 + z1 + (z0 >>> 32); > > Suggestion: > > long result = Math.multiplyHigh(x, y); > if (x < 0) result += y; > if (y < 0) result += x; > return result; This is just subtracting the 2's-complement offset. I guess the idea, longer term, is that this be an intrinsic anyway, but if you do `unsignedMultiplyHigh` this way you'll utilize the existing `multiplyHigh` intrinsic on all platforms that have it. ------------- PR: https://git.openjdk.java.net/jdk/pull/4644
