RFR: 8341137: Optimize long vector multiplication using x86 VPMULUDQ instruction [v2]

Thu Oct 17 21:57:06 UTC 2024

On Thu, 17 Oct 2024 19:40:52 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> MulVL (VectorCastI2X src1) (VectorCastI2X src2)

> It looks unsafe to me, since VectorCastI2L sign-extends integer lanes, ...

Hm, I don't see any problems with it if `VPMULDQ` is used. Sign extension becomes redundant when 64-bit multiplication is strength-reduced to 32-bit one (32x32->64). Am I missing something important here?

-------------

PR Comment: https://git.openjdk.org/jdk/pull/21244#issuecomment-2420668490