RFR: 8287091: aarch64 : guarantee(val < (1ULL << nbits)) failed: Field too big for insn

[Aleksey Shipilev]

On Mon, 23 May 2022 14:55:34 GMT, Andrew Haley <aph at openjdk.org> wrote:

> This is fallout from the patch for JDK-8285923.
> 
> The root cause of this bug is that there is a template definition of `cmp(register, immediate)` but there is not a template definition of `cmn(register, immediate)`. Given that we are close to rampdown, this patch fixes the bug in the most minimal way possible, by using `adds(zr, register, immediate)`, which correctly handles 64-bit operands.
> 
> In the next release cycle we should tidy up `cmn()` in the same way that was done for JDK-8206895.
> 
> Alternatively, we could back out JDK-8285923. I'd rather not, given that it fixes a real (if latent) bug, but if needs be I'll do so.

All right, so we just store the result to `zr`, which is effectively no-op, and ride on the updated flags done by `add*s*`. Looks fine.

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Marked as reviewed by shade (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/8845