RFR: 8261671: X86 I2L conversion can be skipped for certain masked positive values [v3]

Wed Feb 17 17:59:38 UTC 2021

On Wed, 17 Feb 2021 05:56:04 GMT, Florian Weimer <fweimer at openjdk.org> wrote:

>> Added `predicate(VM_Version::supports_bmi2() && VM_Version::is_intel());`
>
> I'm so sorry, I confused this with `PDEP` and `PEXT`. `BZHI` is actually fine on Zen. So the original code is correct.

No worries @fweimer. I've reverted to the original. I looked at Agner's Optimization Guide but I couldn't find a place that said Zen 2 and earlier used microcode for BZHI. I guess we know why now ��. 

Happy to hear any other review comments.

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

PR: https://git.openjdk.java.net/jdk/pull/2590