Remove __bp__ and speed-up bmethod calls (#8060)

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

1 files changed, 0 insertions, 1 deletions

diff --git a/vm_core.h b/vm_core.h
index 4338d65d5e..29ce46e1c3 100644
--- a/vm_core.h
+++ b/vm_core.h
@@ -815,7 +815,6 @@ typedef struct rb_control_frame_struct {
     VALUE self;			/* cfp[3] / block[0] */
     const VALUE *ep;		/* cfp[4] / block[1] */
     const void *block_code;     /* cfp[5] / block[2] */ /* iseq or ifunc or forwarded block handler */
-    VALUE *__bp__;              /* cfp[6] */ /* outside vm_push_frame, use vm_base_ptr instead. */
 
 #if VM_DEBUG_BP_CHECK
     VALUE *bp_check;		/* cfp[7] */