[Ppc64le] Added memory patch thunking for function calls

[alhad-deshpande]

This PR implements memory patch thunking for function calls atomically. This fixes sporadic crashes due to code being patched non-atomically including crashes observed in System.Text.RegularExpressions.Tests. This is similar to what was implemeted for s390x in PR 52783

[dotnet-issue-labeler]

I couldn't figure out the best area label to add to this PR. If you have write-permissions please help me learn by adding exactly one area label.

[alhad-deshpande]

@vargaz
The PR #73616 raised for memory patch thunking fixes crashes observed in System.Text.RegularExpressions.Tests due to code being patched non-atomically.

The assertion mentioned in issue 71080 - "Assertion at /home/directhex/Projects/runtime/src/mono/mono/mini/mini-ppc.c:5080, condition `ppc_is_imm16 (inst->inst_offset)' not met" is observed only in Release mode which we are looking at.

Also, there are new test cases added in RegexPcreTests.cs file which are also failing on Power and hence looking into it as well.

We are targeting this PR for RC1 release. Can you please review it?

[Sapana-Khemkar]

@vargaz can you please review this PR? We are targeting it for RC1 which is planned on 12th August .

[akoeplinger]

/azp run runtime-community

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[akoeplinger]

@vargaz is on vacation right now, I've triggered a CI run to see if the test is fixed and we can merge the PR and he can review when he is back.

[alhad-deshpande]

@vargaz is on vacation right now, I've triggered a CI run to see if the test is fixed and we can merge the PR and he can review when he is back.

@akoeplinger
The System.Text.RegularExpressions.Tests is not fully fixed as mentioned above. But this PR fixes a large part of it where sporadic crashes occurs due to code being patched non-atomically. This has been fixed by memory patch thunking for function calls atomically. Please merge this PR as such crashes can occur anytime during code patching especially in multithreading environment and this PR fixes the same. We are targeting this PR for RC1.

[akoeplinger]

Ok