module RubyVM::YJIT

This module allows for introspection of YJIT, CRuby’s just-in-time compiler. Everything in the module is highly implementation specific and the API might be less stable compared to the standard library.

This module may not exist if YJIT does not support the particular platform for which CRuby is built.

Public Class Methods

code_gc ()

Discard existing compiled code to reclaim memory and allow for recompilations in the future.

# File yjit.rb, line 211
def self.code_gc
  Primitive.rb_yjit_code_gc
end

dump_exit_locations (filename)

Marshal dumps exit locations to the given filename.

Usage:

If --yjit-exit-locations is passed, a file named “yjit_exit_locations.dump” will automatically be generated.

If you want to collect traces manually, call dump_exit_locations directly.

Note that calling this in a script will generate stats after the dump is created, so the stats data may include exits from the dump itself.

In a script call:

at_exit do
  RubyVM::YJIT.dump_exit_locations("my_file.dump")
end

Then run the file with the following options:

ruby --yjit --yjit-trace-exits test.rb

Once the code is done running, use Stackprof to read the dump file. See Stackprof documentation for options.

# File yjit.rb, line 148
def self.dump_exit_locations(filename)
  unless trace_exit_locations_enabled?
    raise ArgumentError, "--yjit-trace-exits must be enabled to use dump_exit_locations."
  end

  File.binwrite(filename, Marshal.dump(RubyVM::YJIT.exit_locations))
end

enable (stats: false)

Enable YJIT compilation. stats option decides whether to enable YJIT stats or not.

false: Disable stats.
true: Enable stats. Print stats at exit.
:quiet: Enable stats. Do not print stats at exit.

# File yjit.rb, line 36
def self.enable(stats: false)
  return false if enabled?
  at_exit { print_and_dump_stats } if stats
  Primitive.rb_yjit_enable(stats, stats != :quiet)
end

enabled? ()

Check if YJIT is enabled.

# File yjit.rb, line 12
def self.enabled?
  Primitive.cexpr! 'RBOOL(rb_yjit_enabled_p)'
end

reset_stats! ()

Discard statistics collected for --yjit-stats.

# File yjit.rb, line 27
def self.reset_stats!
  Primitive.rb_yjit_reset_stats_bang
end

runtime_stats ()

Return a hash for statistics generated for the --yjit-stats command line option. Return nil when option is not passed or unavailable.

# File yjit.rb, line 158
def self.runtime_stats()
  Primitive.rb_yjit_get_stats
end

stats_enabled? ()

Check if --yjit-stats is used.

# File yjit.rb, line 17
def self.stats_enabled?
  Primitive.rb_yjit_stats_enabled_p
end

stats_string ()

Format and print out counters as a String. This returns a non-empty content only when --yjit-stats is enabled.

# File yjit.rb, line 164
def self.stats_string
  # Lazily require StringIO to avoid breaking miniruby
  require 'stringio'
  strio = StringIO.new
  _print_stats(out: strio)
  strio.string
end