RFR: 8253757: Add LLVM-based backend for hsdis [v8]

[Magnus Ihse Bursie]

On Wed, 16 Feb 2022 14:39:49 GMT, Magnus Ihse Bursie <ihse at openjdk.org> wrote:

>> This patch expands the newly added system for hsdis backends to include LLVM.
>> 
>> The actual code in hsdis-llvm.cpp is based heavily on the work by @luhenry, as published in the never integrated PR https://github.com/openjdk/jdk/pull/392. (I have basically just ripped out the binutils-based part of it.)
>> 
>> Unfortunately I have not been able to make this work properly on Windows. With some additional flags I made it compile without complaints, but it caused hotspot to segfault in `LoadLibrary` (!) in `os::dll_load` when I tried to load the library. This is somewhat ironic, since the initial implementation was created by Ludovic for the very purpose of using it on Windows.
>> 
>> The lack of Windows support in this patch does not mean it is impossible to get it to work, just that I need to co-operate with someone who has more experience of compiling LLVM on Windows, and/or are more eager to get this combination to work.
>
> Magnus Ihse Bursie has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Add section on using LLVM
>  - Allow override of LLVM location using --with-llvm

This PR has just gotten too messy. :-( I'll close this one for now, focus on getting the (much simpler) Capstone backend integrated, and then I can come back and revisit this functionality, but in a fresh new PR.

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PR: https://git.openjdk.java.net/jdk/pull/5920