diff --git a/misc/call_fuzzer.rb b/misc/call_fuzzer.rb
new file mode 100644
index 00000000000000..c3f9f90490c0bc
--- /dev/null
+++ b/misc/call_fuzzer.rb
@@ -0,0 +1,372 @@
+require 'optparse'
+require 'set'
+
+# Number of iterations to test
+num_iters = 10_000
+
+# Parse the command-line options
+OptionParser.new do |opts|
+  opts.on("--num-iters=N") do |n|
+    num_iters = n.to_i
+  end
+end.parse!
+
+# Format large numbers with comma separators for readability
+def format_number(pad, number)
+  s = number.to_s
+  i = s.index('.') || s.size
+  s.insert(i -= 3, ',') while i > 3
+  s.rjust(pad, ' ')
+end
+
+# Wrap an integer to pass as argument
+# We use this so we can have some object arguments
+class IntWrapper
+  def initialize(v)
+    # Force the object to have a random shape
+    if rand() < 50
+      @v0 = 1
+    end
+    if rand() < 50
+      @v1 = 1
+    end
+    if rand() < 50
+      @v2 = 1
+    end
+    if rand() < 50
+      @v3 = 1
+    end
+    if rand() < 50
+      @v4 = 1
+    end
+    if rand() < 50
+      @v5 = 1
+    end
+    if rand() < 50
+      @v6 = 1
+    end
+
+    @value = v
+  end
+
+  attr_reader :value
+end
+
+# Generate a random argument value, integer or string or object
+def sample_arg()
+  c = ['int', 'string', 'object'].sample()
+
+  if c == 'int'
+    return rand(0...100)
+  end
+
+  if c == 'string'
+    return 'f' * rand(0...100)
+  end
+
+  if c == 'object'
+    return IntWrapper.new(rand(0...100))
+  end
+
+  raise "should not get here"
+end
+
+# Evaluate the value of an argument with respect to the checksum
+def arg_val(arg)
+  if arg.kind_of? Integer
+    return arg
+  end
+
+  if arg.kind_of? String
+    return arg.length
+  end
+
+  if arg.kind_of? Object
+    return arg.value
+  end
+
+  raise "unknown arg type"
+end
+
+# List of parameters/arguments for a method
+class ParamList
+  def initialize()
+    self.sample_params()
+    self.sample_args()
+  end
+
+  # Sample/generate a random set of parameters for a method
+  def sample_params()
+    # Choose how many positional arguments to use, and how many are optional
+    num_pargs = rand(10)
+    @opt_parg_idx = rand(num_pargs)
+    @num_opt_pargs = rand(num_pargs + 1 - @opt_parg_idx)
+    @num_pargs_req = num_pargs - @num_opt_pargs
+    @pargs = (0...num_pargs).map do |i|
+      {
+        :name => "p#{i}",
+        :optional => (i >= @opt_parg_idx && i < @opt_parg_idx + @num_opt_pargs)
+      }
+    end
+
+    # Choose how many kwargs to use, and how many are optional
+    num_kwargs = rand(10)
+    @kwargs = (0...num_kwargs).map do |i|
+      {
+        :name => "k#{i}",
+        :optional => rand() < 0.5
+      }
+    end
+
+    # Choose whether to have rest parameters or not
+    @has_rest = @num_opt_pargs == 0 && rand() < 0.5
+    @has_kwrest = rand() < 0.25
+
+    # Choose whether to have a named block parameter or not
+    @has_block_param = rand() < 0.25
+  end
+
+  # Sample/generate a random set of arguments corresponding to the parameters
+  def sample_args()
+    # Choose how many positional args to pass
+    num_pargs_passed = rand(@num_pargs_req..@pargs.size)
+
+    # How many optional arguments will be filled
+    opt_pargs_filled = num_pargs_passed - @num_pargs_req
+
+    @pargs.each_with_index do |parg, i|
+      if parg[:optional]
+        parg[:default] = rand(100)
+      end
+
+      if !parg[:optional] || i < @opt_parg_idx + opt_pargs_filled
+        parg[:argval] = rand(100)
+      end
+    end
+
+    @kwargs.each_with_index do |kwarg, i|
+      if kwarg[:optional]
+        kwarg[:default] = rand(100)
+      end
+
+      if !kwarg[:optional] || rand() < 0.5
+        kwarg[:argval] = rand(100)
+      end
+    end
+
+    # Randomly pass a block or not
+    @block_arg = nil
+    if rand() < 0.5
+      @block_arg = rand(100)
+    end
+  end
+
+  # Compute the expected checksum of arguments ahead of time
+  def compute_checksum()
+    checksum = 0
+
+    @pargs.each_with_index do |arg, i|
+      value = (arg.key? :argval)? arg[:argval]:arg[:default]
+      checksum += (i+1) * arg_val(value)
+    end
+
+    @kwargs.each_with_index do |arg, i|
+      value = (arg.key? :argval)? arg[:argval]:arg[:default]
+      checksum += (i+1) * arg_val(value)
+    end
+
+    if @block_arg
+      if @has_block_param
+        checksum += arg_val(@block_arg)
+      end
+
+      checksum += arg_val(@block_arg)
+    end
+
+    checksum
+  end
+
+  # Generate code for the method signature and method body
+  def gen_method_str()
+    m_str = "def m("
+
+    @pargs.each do |arg|
+      if !m_str.end_with?("(")
+        m_str += ", "
+      end
+
+      m_str += arg[:name]
+
+      # If this has a default value
+      if arg[:optional]
+        m_str += " = #{arg[:default]}"
+      end
+    end
+
+    if @has_rest
+      if !m_str.end_with?("(")
+        m_str += ", "
+      end
+      m_str += "*rest"
+    end
+
+    @kwargs.each do |arg|
+      if !m_str.end_with?("(")
+        m_str += ", "
+      end
+
+      m_str += "#{arg[:name]}:"
+
+      # If this has a default value
+      if arg[:optional]
+        m_str += " #{arg[:default]}"
+      end
+    end
+
+    if @has_kwrest
+      if !m_str.end_with?("(")
+        m_str += ", "
+      end
+      m_str += "**kwrest"
+    end
+
+    if @has_block_param
+      if !m_str.end_with?("(")
+        m_str += ", "
+      end
+
+      m_str += "&block"
+    end
+
+    m_str += ")\n"
+
+    # Add some useless locals
+    rand(0...16).times do |i|
+      m_str += "local#{i} = #{i}\n"
+    end
+
+    # Add some useless if statements
+    @pargs.each_with_index do |arg, i|
+      if rand() < 50
+        m_str += "if #{arg[:name]} > 4; end\n"
+      end
+    end
+
+    m_str += "checksum = 0\n"
+
+    @pargs.each_with_index do |arg, i|
+      m_str += "checksum += #{i+1} * arg_val(#{arg[:name]})\n"
+    end
+
+    @kwargs.each_with_index do |arg, i|
+      m_str += "checksum += #{i+1} * arg_val(#{arg[:name]})\n"
+    end
+
+    if @has_block_param
+      m_str += "if block; r = block.call; checksum += arg_val(r); end\n"
+    end
+
+    m_str += "if block_given?; r = yield; checksum += arg_val(r); end\n"
+
+    if @has_rest
+      m_str += "raise 'rest is not array' unless rest.kind_of?(Array)\n"
+      m_str += "raise 'rest size not integer' unless rest.size.kind_of?(Integer)\n"
+    end
+
+    if @has_kwrest
+      m_str += "raise 'kwrest is not a hash' unless kwrest.kind_of?(Hash)\n"
+      m_str += "raise 'kwrest size not integer' unless kwrest.size.kind_of?(Integer)\n"
+    end
+
+    m_str += "checksum\n"
+    m_str += "end"
+
+    m_str
+  end
+
+  # Generate code to call into the method and pass the arguments
+  def gen_call_str()
+    c_str = "m("
+
+    @pargs.each_with_index do |arg, i|
+      if !arg.key? :argval
+        next
+      end
+
+      if !c_str.end_with?("(")
+        c_str += ", "
+      end
+
+      c_str += "#{arg[:argval]}"
+    end
+
+    @kwargs.each_with_index do |arg, i|
+      if !arg.key? :argval
+        next
+      end
+
+      if !c_str.end_with?("(")
+        c_str += ", "
+      end
+
+      c_str += "#{arg[:name]}: #{arg[:argval]}"
+    end
+
+    c_str += ")"
+
+    # Randomly pass a block or not
+    if @block_arg
+      c_str += " { #{@block_arg} }"
+    end
+
+    c_str
+  end
+end
+
+iseqs_compiled_start = RubyVM::YJIT.runtime_stats[:compiled_iseq_entry]
+start_time = Time.now.to_f
+
+num_iters.times do |i|
+  puts "Iteration #{i}"
+
+  lst = ParamList.new()
+  m_str = lst.gen_method_str()
+  c_str = lst.gen_call_str()
+  checksum = lst.compute_checksum()
+
+  f = Object.new
+
+  # Define the method on f
+  puts "Defining"
+  p m_str
+  f.instance_eval(m_str)
+  #puts RubyVM::InstructionSequence.disasm(f.method(:m))
+  #exit 0
+
+  puts "Calling"
+  c_str = "f.#{c_str}"
+  p c_str
+  r = eval(c_str)
+  puts "checksum=#{r}"
+
+  if r != checksum
+    raise "return value #{r} doesn't match checksum #{checksum}"
+  end
+
+  puts ""
+end
+
+# Make sure that YJIT actually compiled the tests we ran
+# Should be run with --yjit-call-threshold=1
+iseqs_compiled_end = RubyVM::YJIT.runtime_stats[:compiled_iseq_entry]
+if iseqs_compiled_end - iseqs_compiled_start < num_iters
+  raise "YJIT did not compile enough ISEQs"
+end
+
+puts "Code region size: #{ format_number(0, RubyVM::YJIT.runtime_stats[:code_region_size]) }"
+
+end_time = Time.now.to_f
+itrs_per_sec = num_iters / (end_time - start_time)
+itrs_per_hour = 3600 * itrs_per_sec
+puts "#{'%.1f' % itrs_per_sec} iterations/s"
+puts "#{format_number(0, itrs_per_hour.round)} iterations/hour"
diff --git a/misc/call_fuzzer.sh b/misc/call_fuzzer.sh
new file mode 100755
index 00000000000000..cf4ec76fe825a6
--- /dev/null
+++ b/misc/call_fuzzer.sh
@@ -0,0 +1,13 @@
+# Stop at first error
+set -e
+
+# TODO
+# TODO: boost --num-iters to 1M+ for actual test
+# TODO
+export NUM_ITERS=25000
+
+# Enable code GC so we don't stop compiling when we hit the code size limit
+ruby --yjit-call-threshold=1 --yjit-code-gc misc/call_fuzzer.rb --num-iters=$NUM_ITERS
+
+# Do another pass with --verify-ctx
+ruby --yjit-call-threshold=1 --yjit-code-gc --yjit-verify-ctx misc/call_fuzzer.rb --num-iters=$NUM_ITERS