[clang] [llvm] [LTO][AllocToken] Support AllocToken instrumentation in backend (PR #169358)

[Marco Elver via llvm-commits]

melver wrote:

> > Could you also add the alloc token metadata, and/or whatever else is needed to cause the allocator calls to kick in, to at least one of the operator new calls in llvm/test/Transforms/InstCombine/simplify-libcalls-new.ll (or create a new small test that has this), and invoke various pipelines on it via opt to ensure we still get the expected transformations (to hot cold operator new and subsequently the alloc token version)? E.g. `opt -passes='thinlto<O2>'` and `opt -passes='lto<O2>'` ?
> 
> Largely lgtm to me, except I had a comment about simplifying the cl::opt checks.

Done.

> Also, please add a change to an existing memprof test like suggested above - this will ensure the phase ordering stays correct.

Sorry, missed that.
Added 2 new tests - it seems that we need -supports-hot-cold-new and the index so the LTO pipeline doesn't remove the hot/cold hints, correct? I added a dedicated test to the AllocToken suite and another in the LTO/X86 suite, the latter of which should ensure we catch any deeper regressions.

PTAL.

https://github.com/llvm/llvm-project/pull/169358