Move JITLink from StringRefs to SymbolStringPtrs

[weliveindetail]

JITLink is using the lllvm::StringRef type in many places where llvm::orc::SymbolStringPtr would result in better performance and memory footprint, e.g.

llvm-project/llvm/include/llvm/ExecutionEngine/JITLink/JITLink.h

Lines 648 to 649 in 7748055

	// FIXME: A char* or SymbolStringPtr may pack better.
	StringRef Name;

In such cases the string should be interned in a llvm::orc::SymbolStringPool and referenced via llvm::orc::SymbolStringPtr.

[llvmbot]

@llvm/issue-subscribers-orcjit

[llvmbot]

@llvm/issue-subscribers-good-first-issue

[llvmbot]

@llvm/issue-subscribers-jitlink

[moazin]

I'm gonna try and fix this. Will report back on progress soon.

[weliveindetail]

@moazin Thanks for looking into this! If you have questions, feel free to reach out in the #JIT Channel in the LLVM Discord: https://discord.gg/5H8JSRe

[jaredwy]

There hadn't been any movement on this for a while. So I have a review up for it now. Sorry if I trod on any toes.

[weliveindetail]

Hi Jared, thanks for working on this. Can you maybe link your review here?

[lhames]

@weliveindetail -- The review is at https://reviews.llvm.org/D132988.

[diohabara]

There don't seem to be any updates to the review at all recently, is it possible to take over this review?

[lhames]

I reached out to @jaredwy and he said that he's almost done with the work and hopes to land it soon.

[miguelraz]

Hey @weliveindetail - I'm very interested in what this PR can help out Julia's rubtime for memory footprint.

Is there anyway I can help push this along?