[llvm] [InstrRef] Preserve debug instr num in aarch64-cond-br-tuning. (PR #132081)

[Shubham Sandeep Rastogi via llvm-commits]

rastogishubham wrote:

The reason I have not included a mir test that just runs the aarch64-cond-br-tuning pass on the mir and checks for the debug instruction number is:

Just because a pass runs in the pass pipeline doesn't mean it is registered in the pass registry, if we look at the code in `llvm/lib/Target/AArch64/AArch64TargetMachine.cpp` in function `AArch64PassConfig::addILPOpts` all the passes added to the passmanager here are not registered in the pass registry, so you will see them run, but if you want to use -stop-after -stop-before -run-pass etc options, you cannot do that, I don't have a rationale for why this is the case.

Therefore the test is an llvm IR and dwarfdump test that checks to make sure that the debug location does indeed survive

https://github.com/llvm/llvm-project/pull/132081