[vectorIntrinsics] RFR: 8274631: assert(false) failed: bad AD file with -XX:UseKNLSetting [v2]

[Jatin Bhateja]

On Fri, 1 Oct 2021 18:35:12 GMT, Paul Sandoz <psandoz at openjdk.org> wrote:

>> So IIUC it's because the flags create an artificial scenario that does not ordinarily arise. If so can we add a comment regarding the configuration that might result in this code path being taken?
>
> Also can we double check if this only arises for debug builds?

>From X86 standpoint, this case will only arise over KNL, where certain masks (depending on the species) are either propagated through a vector or predicate register.  This is exactly what the code checks. I did not add a comment in code since its a common IR code.  Over KNL predicate registers are used only if corresponding vector is 512 bit wide.
Thus a casting b/w Int256Mask and Double512Mask is not being handled over KNL currently under the assumption that most mask are used for vector predication and since KNL does not support EVEX instruction over partial vectors (128 and 256 bits) so masks corresponding these sizes will be propagated using vectors and not predicate registers.

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PR: https://git.openjdk.java.net/panama-vector/pull/141