RFR: 8283699: Improve the peephole mechanism of hotspot [v4]

[Quan Anh Mai]

On Fri, 7 Oct 2022 20:23:28 GMT, Vladimir Ivanov <vlivanov at openjdk.org> wrote:

>> Yes, good idea.
>
> Considering `peephole_x86.cpp` contains  only x64-specific code, I had a suggestion to rename it into `peephole_x86_64.cpp` and move `#ifdef _LP64` into `peephole_x86.hpp` to guard x64-specific declarations. But if you intend to include the header directly from `x86_64.ad`, you can rename the header to `peephole_x86_64.hpp` and get rid of `#ifdef _LP64` completely.

I have refactored that and removed `opto/peephole.hpp` as well as other peephole headers. `peephole_x86.cpp` is also renamed to `peephole_x86_64.cpp`. Thanks very much.

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PR: https://git.openjdk.org/jdk/pull/8025