RFR: 8268229: Aarch64: Use Neon in intrinsics for String.equals

[Andrew Haley]

On Tue, 15 Jun 2021 08:52:16 GMT, Andrew Haley <aph at openjdk.org> wrote:

> > With this change the size of the`string_equals` intrinsic increases by ~60% from 120 bytes to 196 bytes and this gets expanded at every `String.equals` call site. It looks good on a micro-benchmark but I wonder if on a larger program this improvement is outweighed by the negative effects of methods taking up more space in the icache.
> 
> That's an excellent point. There's no need at all for the Neon part to be expanded inline: it could be a subroutine. We'd have to use fixed Neon registers at the call site.

Thinking some more,we could use this opportunity to move as much of the bulk comparison code as we can out of line, hopefully achieving a reduction in footprint as well as an improvement in performance.

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PR: https://git.openjdk.java.net/jdk/pull/4423