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Remove __bp__ and speed-up bmethod calls #8060

Merged
merged 1 commit into from
Jul 17, 2023
Merged

Remove __bp__ and speed-up bmethod calls #8060

merged 1 commit into from
Jul 17, 2023

Commits on Jul 17, 2023

  1. 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
9121e57.

Closes ruby#6428
    @XrXr
    XrXr committed Jul 17, 2023
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