[clang] [llvm] [BPF] Make -mcpu=v3 as the default (PR #107008)

[via llvm-commits]

yonghong-song wrote:

> > @yuvald-sweet-security Could you share which kernel you are used for above testing?
> 
> I ran this on my host machine which is Windows with WSL, kernel `6.6.75.1-microsoft-standard-WSL2`. However, I can see similar regressions on pretty much every testing VM that I have, for example here's Ubuntu 22.04 with kernel `6.8.0-1021-azure`:
> 
> ```
> $ sudo ~/veristat /tmp/test-v1.o --filter=trace_ret_vfs_writev_tail
> Processing 'test-v1.o'...
> File       Program                    Verdict  Duration (us)  Insns  States  Peak states
> ---------  -------------------------  -------  -------------  -----  ------  -----------
> test-v1.o  trace_ret_vfs_writev_tail  success          23429  25015    1859         1728
> ---------  -------------------------  -------  -------------  -----  ------  -----------
> Done. Processed 1 files, 0 programs. Skipped 1 files, 158 programs.
> 
> $ sudo ~/veristat /tmp/test-v3.o --filter=trace_ret_vfs_writev_tail
> Processing 'test-v3.o'...
> File       Program                    Verdict  Duration (us)  Insns  States  Peak states
> ---------  -------------------------  -------  -------------  -----  ------  -----------
> test-v3.o  trace_ret_vfs_writev_tail  failure          98260  80350    6184         2738
> ---------  -------------------------  -------  -------------  -----  ------  -----------
> Done. Processed 1 files, 0 programs. Skipped 1 files, 158 programs.
> ```

Thanks @yuvald-sweet-security I will take a look.

https://github.com/llvm/llvm-project/pull/107008