Ruby

Improve the performance of super

This PR improves the performance of super calls. While working on some
Rails optimizations jhawthorn discovered that super calls were slower
than expected.

The changes here do the following:

1. Adds a check for whether the call frame is not equal to the method
   entry iseq. This avoids the rb_obj_is_kind_of check on the next line
   which is quite slow. If the current call frame is equal to the method
   entry we know we can't have an instance eval, etc.
2. Changes FL_TEST to FL_TEST_RAW. This is safe because we've
   already done the check for T_ICLASS above.
3. Adds a benchmark for T_ICLASS super calls.
4. Note: makes a chage for method_entry_cref to use const.

On master the benchmarks showed that super is 1.76x slower. Our
changes improved the performance so that it is now only 1.36x slower.

Benchmark IPS:

Warming up --------------------------------------
               super   244.918k i/100ms
         method call   383.007k i/100ms
Calculating -------------------------------------
               super      2.280M (± 6.7%) i/s -     11.511M in   5.071758s
         method call      3.834M (± 4.9%) i/s -     19.150M in   5.008444s

Comparison:
         method call:  3833648.3 i/s
               super:  2279837.9 i/s - 1.68x  (± 0.00) slower

With changes:

Warming up --------------------------------------
               super   308.777k i/100ms
         method call   375.051k i/100ms
Calculating -------------------------------------
               super      2.951M (± 5.4%) i/s -     14.821M in   5.039592s
         method call      3.551M (± 4.9%) i/s -     18.002M in   5.081695s

Comparison:
         method call:  3551372.7 i/s
               super:  2950557.9 i/s - 1.20x  (± 0.00) slower

Ruby VM benchmarks also showed an improvement:

Existing vm_super benchmark`.

$ make benchmark ITEM=vm_super

|          |compare-ruby|built-ruby|
|:---------|-----------:|---------:|
|vm_super  |     21.555M|   37.819M|
|          |           -|     1.75x|

New vm_iclass_super benchmark:

$ make benchmark ITEM=vm_iclass_super

|                 |compare-ruby|built-ruby|
|:----------------|-----------:|---------:|
|vm_iclass_super  |      1.669M|    3.683M|
|                 |           -|     2.21x|

This is the benchmark script used for the benchmark-ips benchmarks:

require "benchmark/ips"

class Foo
  def zuper; end
  def top; end

  last_method = "top"

  ("A".."M").each do |module_name|
    eval <<-EOM
    module #{module_name}
      def zuper; super; end
      def #{module_name.downcase}
        #{last_method}
      end
    end
    prepend #{module_name}
    EOM
    last_method = module_name.downcase
  end
end

foo = Foo.new

Benchmark.ips do |x|
  x.report "super" do
    foo.zuper
  end

  x.report "method call" do
    foo.m
  end

  x.compare!
end

Co-authored-by: Aaron Patterson [email protected]
Co-authored-by: John Hawthorn [email protected]