RFR(S): 8209544: AES encrypt performance regression in jdk11b11

[Roland Westrelin]

> mkay, but how, exactly? Is it simply the case that Intel is improved
> so the patch is good, even if AArch64 regresses?

Well, no, I don't think that's an accurate description of what this
is. Dmitry reported a performance regression but the generated code is
almost identical with or without the patch (the only difference being
that in one case the generated code uses b.cc and in the other
b.eq). Dmitry also hypothesized that branch prediction may not perform
as well with the patch. That doesn't seem directly related to the patch
but more of an unfortunate side effect. So the patch simplifies the IR
so less instructions may need to be emitted. That's not x86 specific. It
just happens that aarch64 don't seem to be able to take advantage of it
but it doesn't increase the number of instructions that aarch64 needs
either or forces aarch64 to use less efficient instructions. So overall,
it seemed to me there was no reasonable reason to not push this patch.

Roland.