Remove rb_control_frame_t::__bp__ and optimize bmethod calls This commit removes the __bp__ field from rb_control_frame_t. It was introduced to help MJIT, but since MJIT was replaced by RJIT, we can use vm_base_ptr() to compute it from the SP of the previous control frame instead. Removing the field avoids needing to set it up when pushing new frames. Simply removing __bp__ would cause crashes since RJIT and YJIT used a slightly different stack layout for bmethod calls than the interpreter. At the moment of the call, the two layouts looked as follows: ┌────────────┐ ┌────────────┐ │ frame_base │ │ frame_base │ ├────────────┤ ├────────────┤ │ ... │ │ ... │ ├────────────┤ ├────────────┤ │ args │ │ args │ ├────────────┤ └────────────┘<─prev_frame_sp │ receiver │ prev_frame_sp─>└────────────┘ RJIT & YJIT interpreter Essentially, vm_base_ptr() needs to compute the address to frame_base given prev_frame_sp in the diagrams. The presence of the receiver created an off-by-one situation. Make the interpreter use the layout the JITs use for iseq-to-iseq bmethod calls. Doing so removes unnecessary argument shifting and vm_exec_core() re-entry from the interpreter, yielding a speed improvement visible through `benchmark/vm_defined_method.yml`: patched: 7578743.1 i/s master: 4796596.3 i/s - 1.58x slower C-to-iseq bmethod calls now store one more VALUE than before, but that should have negligible impact on overall performance. Note that re-entering vm_exec_core() used to be necessary for firing TracePoint events, but that's no longer the case since 9121e57a5f50bc91bae48b3b91edb283bf96cb6b. Closes ruby/ruby#6428