[llvm] [llvm-exegesis] [AArch64] Add support for Load Instructions in subprocess execution mode (PR #144895)

[Aiden Grossman via llvm-commits]

boomanaiden154 wrote:

With how much higher the measurements are in subprocess mode, it seems like configuring the perf counter isn't actually doing anything. I don't believe there is any error handling there, so it could be that the system calls are just failing. I've been meaning to wire up error handling for that and mmap failures but have never gotten around to it. The best way I found to validate it was to single step through the assembly in a debugger. There's some flag that I think I remember putting somewhere to not have `llvm-exegesis` ptrace attach to the child process so you can actually debug.

https://github.com/llvm/llvm-project/pull/144895