Support Rust v0 mangling

[ChoKyuWon]

For now, utils/demangle.c only care about the Itanium C++ ABI mangling rules.
However, Rust introduces a new mangling rule, v0 mangling. (See the RFC and PR)

For example, std::mem::align_of::<f64> mangles to _RINvNtC3std3mem8align_ofdE.
Note that this new mangling scheme starts with a new identifier, _R.

We need support for this new mangling scheme.

[namhyung]

What's the command line to enable the v0 mangling? It'd be nice if you share a result of uftrace + hello world in v0.

[ChoKyuWon]

$ cargo new --bin v0_mangling && cd v0_mangling
$ RUSTFLAGS="-Zsymbol-mangling-version=v0" cargo build

$ uftrace -P. -F _RNvCskxQuv2bvxbZ_11v0_mangling4main ./target/debug/v0_mangling
# DURATION     TID     FUNCTION
            [3613655] | _RNvCskxQuv2bvxbZ_11v0_mangling4main() {
   0.120 us [3613655] |   _RNvMs2_NtCscoN4IID3Vv4_4core3fmtNtB5_9Arguments6new_v1CskxQuv2bvxbZ_11v0_mangling();
            [3613655] |   std::io::stdio::_print() {
            [3613655] |     std::sync::once::Once::call_inner() {
            [3613655] |       std::sync::once::Once::call_once_force::_{{closure}}() {
   0.090 us [3613655] |         __rdl_alloc();
   0.351 us [3613655] |       } /* std::sync::once::Once::call_once_force::_{{closure}} */
   0.090 us [3613655] |       _<std..sync..once..WaiterQueue as core..ops..drop..Drop>::drop();
   0.741 us [3613655] |     } /* std::sync::once::Once::call_inner */
            [3613655] |     _<&std..io..stdio..Stdout as std..io..Write>::write_fmt() {
   0.090 us [3613655] |       std::sys_common::remutex::current_thread_unique_ptr::X::__getit();
            [3613655] |       core::fmt::write() {
            [3613655] |         _<std..io..Write..write_fmt..Adapter<T> as core..fmt..Write>::write_str() {
            [3613655] |           _<std..io..buffered..linewritershim..LineWriterShim<W> as std..io..Write>::write_all() {
            [3613655] |             _<std..io..stdio..StdoutRaw as std..io..Write>::write_all() {
   6.954 us [3613655] |               std::io::Write::write_all();
   7.184 us [3613655] |             } /* _<std..io..stdio..StdoutRaw as std..io..Write>::write_all */
   7.464 us [3613655] |           } /* _<std..io..buffered..linewritershim..LineWriterShim<W> as std..io..Write>::write_all */
   7.675 us [3613655] |         } /* _<std..io..Write..write_fmt..Adapter<T> as core..fmt..Write>::write_str */
   7.855 us [3613655] |       } /* core::fmt::write */
   8.235 us [3613655] |     } /* _<&std..io..stdio..Stdout as std..io..Write>::write_fmt */
   9.268 us [3613655] |   } /* std::io::stdio::_print */
  10.591 us [3613655] | } /* _RNvCskxQuv2bvxbZ_11v0_mangling4main */

$ uftrace -P. -F v0_mangling::main ./target/debug/v0_mangling
# DURATION     TID     FUNCTION
            [3613773] | main() {
            [3613773] |   _RINvNtCsjaRYnC5jcmR_3std2rt10lang_startuECskxQuv2bvxbZ_11v0_mangling() {
            [3613773] |     std::rt::lang_start_internal() {
            [3613773] |       std::rt::init() {
            [3613773] |         std::sys::unix::init() {
            [3613773] |           std::sys::unix::stack_overflow::imp::init() {
   2.365 us [3613773] |             std::sys::unix::stack_overflow::imp::make_handler();
   3.447 us [3613773] |           } /* std::sys::unix::stack_overflow::imp::init */
   8.336 us [3613773] |         } /* std::sys::unix::init */
  54.595 us [3613773] |         std::sys::unix::thread::guard::init();
            [3613773] |         _<&str as alloc..ffi..c_str..CString..new..SpecNewImpl>::spec_new_impl() {
   0.220 us [3613773] |           __rdl_alloc();
   0.130 us [3613773] |           alloc::vec::Vec<T,A>::into_boxed_slice();
   0.871 us [3613773] |         } /* _<&str as alloc..ffi..c_str..CString..new..SpecNewImpl>::spec_new_impl */
            [3613773] |         alloc::sync::Arc<T>::new_uninit() {
   0.110 us [3613773] |           __rdl_alloc();
   0.331 us [3613773] |         } /* alloc::sync::Arc<T>::new_uninit */
            [3613773] |         std::thread::local::LocalKey<T>::with() {
   0.471 us [3613773] |           std::sys_common::thread_info::THREAD_INFO::__getit();
   0.651 us [3613773] |         } /* std::thread::local::LocalKey<T>::with */
  65.405 us [3613773] |       } /* std::rt::init */
            [3613773] |       _RNCINvNtCsjaRYnC5jcmR_3std2rt10lang_startuE0CskxQuv2bvxbZ_11v0_mangling() {
            [3613773] |         _RINvNtNtCsjaRYnC5jcmR_3std10sys_common9backtrace28___rust_begin_short_backtraceFEuuECskxQuv2bvxbZ_11v0_mangling() {
            [3613773] |           _RNvYFEuINtNtNtCscoN4IID3Vv4_4core3ops8function6FnOnceuE9call_onceCskxQuv2bvxbZ_11v0_mangling() {
            [3613773] |             _RNvCskxQuv2bvxbZ_11v0_mangling4main() {
...