Rename RubyVM::MJIT to RubyVM::JIT

because the name "MJIT" is an internal code name, it's inconsistent with
--jit while they are related to each other, and I want to discourage future
JIT implementation-specific (e.g. MJIT-specific) APIs by this rename.

[Feature #17490]

34 files changed, 86 insertions, 81 deletions

diff --git a/NEWS.md b/NEWS.md
index 604be60ce4..1e3202c235 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -37,6 +37,8 @@ Excluding feature bug fixes.
 
 ### JIT
 
+* `RubyVM::MJIT` is renamed to `RubyVM::JIT`.
+
 ## Static analysis
 
 ### RBS
diff --git a/benchmark/lib/benchmark_driver/runner/mjit.rb b/benchmark/lib/benchmark_driver/runner/mjit.rb
index 1d4693e8be..abefa463b3 100644
--- a/benchmark/lib/benchmark_driver/runner/mjit.rb
+++ b/benchmark/lib/benchmark_driver/runner/mjit.rb
@@ -14,17 +14,17 @@ class BenchmarkDriver::Runner::Mjit < BenchmarkDriver::Runner::Ips
       jobs.map do |job|
         job = job.dup
         job.prelude = "#{job.prelude}\n#{<<~EOS}"
-          if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled?
+          if defined?(RubyVM::JIT) && RubyVM::JIT.enabled?
             __bmdv_ruby_i = 0
             while __bmdv_ruby_i < 10000 # jit_min_calls
               #{job.script}
               __bmdv_ruby_i += 1
             end
-            RubyVM::MJIT.pause # compile
+            RubyVM::JIT.pause # compile
             #{job.script}
-            RubyVM::MJIT.resume; RubyVM::MJIT.pause # recompile
+            RubyVM::JIT.resume; RubyVM::JIT.pause # recompile
             #{job.script}
-            RubyVM::MJIT.resume; RubyVM::MJIT.pause # recompile 2
+            RubyVM::JIT.resume; RubyVM::JIT.pause # recompile 2
           end
         EOS
         job
diff --git a/benchmark/lib/benchmark_driver/runner/mjit_exec.rb b/benchmark/lib/benchmark_driver/runner/mjit_exec.rb
index eac3dfba84..46e662bc7c 100644
--- a/benchmark/lib/benchmark_driver/runner/mjit_exec.rb
+++ b/benchmark/lib/benchmark_driver/runner/mjit_exec.rb
@@ -135,7 +135,7 @@ class BenchmarkDriver::Runner::MjitExec
           nil
         end
         % end
-        RubyVM::MJIT.pause if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled?
+        RubyVM::JIT.pause if defined?(RubyVM::JIT) && RubyVM::JIT.enabled?
 
         def vm
           t = Process.clock_gettime(Process::CLOCK_MONOTONIC)
@@ -172,7 +172,7 @@ class BenchmarkDriver::Runner::MjitExec
         a<%= i %>
         a<%= i %> # --jit-min-calls=2
         % end
-        RubyVM::MJIT.pause if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled?
+        RubyVM::JIT.pause if defined?(RubyVM::JIT) && RubyVM::JIT.enabled?
 
         def vm
           t = Process.clock_gettime(Process::CLOCK_MONOTONIC)
@@ -228,7 +228,7 @@ class BenchmarkDriver::Runner::MjitExec
 
         jit
         jit
-        RubyVM::MJIT.pause if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled?
+        RubyVM::JIT.pause if defined?(RubyVM::JIT) && RubyVM::JIT.enabled?
         File.write(<%= result.dump %>, jit)
       EOS
     end
diff --git a/bootstraptest/runner.rb b/bootstraptest/runner.rb
index 2cd91ffd07..11d5a6c17e 100755
--- a/bootstraptest/runner.rb
+++ b/bootstraptest/runner.rb
@@ -383,7 +383,7 @@ def assert_normal_exit(testsrc, *rest, timeout: nil, **opt)
 end
 
 def assert_finish(timeout_seconds, testsrc, message = '')
-  if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # for --jit-wait
+  if defined?(RubyVM::JIT) && RubyVM::JIT.enabled? # for --jit-wait
     timeout_seconds *= 3
   end
   newtest
diff --git a/spec/ruby/core/io/flush_spec.rb b/spec/ruby/core/io/flush_spec.rb
index 34cf42c425..8de373a0bd 100644
--- a/spec/ruby/core/io/flush_spec.rb
+++ b/spec/ruby/core/io/flush_spec.rb
@@ -23,7 +23,7 @@ describe "IO#flush" do
     # For instance, MJIT creates a worker before @r.close with fork(), @r.close happens,
     # and the MJIT worker keeps the pipe open until the worker execve().
     # TODO: consider acquiring GVL from MJIT worker.
-    guard_not -> { defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? } do
+    guard_not -> { defined?(RubyVM::JIT) && RubyVM::JIT.enabled? } do
       it "raises Errno::EPIPE if sync=false and the read end is closed" do
         @w.sync = false
         @w.write "foo"
diff --git a/spec/ruby/core/io/shared/write.rb b/spec/ruby/core/io/shared/write.rb
index 270b84ac39..5e53d981c5 100644
--- a/spec/ruby/core/io/shared/write.rb
+++ b/spec/ruby/core/io/shared/write.rb
@@ -99,7 +99,7 @@ describe :io_write, shared: true do
     # For instance, MJIT creates a worker before @r.close with fork(), @r.close happens,
     # and the MJIT worker keeps the pipe open until the worker execve().
     # TODO: consider acquiring GVL from MJIT worker.
-    guard_not -> { defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? } do
+    guard_not -> { defined?(RubyVM::JIT) && RubyVM::JIT.enabled? } do
       it "raises Errno::EPIPE if the read end is closed and does not die from SIGPIPE" do
         @r.close
         -> { @w.send(@method, "foo") }.should raise_error(Errno::EPIPE, /Broken pipe/)
diff --git a/template/fake.rb.in b/template/fake.rb.in
index f1da719ecb..25053d3dbf 100644
--- a/template/fake.rb.in
+++ b/template/fake.rb.in
@@ -32,7 +32,7 @@ class Object
   CROSS_COMPILING = RUBY_PLATFORM
   constants.grep(/^RUBY_/) {|n| remove_const n}
 % arg['versions'].each {|n, v|
-  <%=n%> = <%if n=='RUBY_DESCRIPTION' %>RubyVM.const_defined?(:MJIT) && RubyVM::MJIT.enabled? ?
+  <%=n%> = <%if n=='RUBY_DESCRIPTION' %>RubyVM.const_defined?(:JIT) && RubyVM::JIT.enabled? ?
     <%=arg['RUBY_DESCRIPTION_WITH_JIT'].inspect%> :
     <%end%><%=v.inspect%>
 % }
diff --git a/test/-ext-/bug_reporter/test_bug_reporter.rb b/test/-ext-/bug_reporter/test_bug_reporter.rb
index 6b8e1754a7..ac6d92bb67 100644
--- a/test/-ext-/bug_reporter/test_bug_reporter.rb
+++ b/test/-ext-/bug_reporter/test_bug_reporter.rb
@@ -7,7 +7,7 @@ class TestBugReporter < Test::Unit::TestCase
     skip if ENV['RUBY_ON_BUG']
 
     description = RUBY_DESCRIPTION
-    description = description.sub(/\+JIT /, '') if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled?
+    description = description.sub(/\+JIT /, '') if defined?(RubyVM::JIT) && RubyVM::JIT.enabled?
     expected_stderr = [
       :*,
       /\[BUG\]\sSegmentation\sfault.*\n/,
diff --git a/test/csv/parse/test_general.rb b/test/csv/parse/test_general.rb
index 52b0cab000..14903d462c 100644
--- a/test/csv/parse/test_general.rb
+++ b/test/csv/parse/test_general.rb
@@ -247,7 +247,7 @@ line,5,jkl
   def assert_parse_errors_out(data, **options)
     assert_raise(CSV::MalformedCSVError) do
       timeout = 0.2
-      if defined?(RubyVM::MJIT.enabled?) and RubyVM::MJIT.enabled?
+      if defined?(RubyVM::JIT.enabled?) and RubyVM::JIT.enabled?
         timeout = 5  # for --jit-wait
       end
       Timeout.timeout(timeout) do
diff --git a/test/drb/drbtest.rb b/test/drb/drbtest.rb
index 16ffec904b..acef380ad6 100644
--- a/test/drb/drbtest.rb
+++ b/test/drb/drbtest.rb
@@ -216,7 +216,7 @@ module DRbCore
   def test_06_timeout
     skip if RUBY_PLATFORM.include?("armv7l-linux")
     skip if RUBY_PLATFORM.include?("sparc-solaris2.10")
-    skip if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # expecting a certain delay is difficult for --jit-wait CI
+    skip if defined?(RubyVM::JIT) && RubyVM::JIT.enabled? # expecting a certain delay is difficult for --jit-wait CI
     Timeout.timeout(60) do
       ten = Onecky.new(10)
       assert_raise(Timeout::Error) do
diff --git a/test/lib/jit_support.rb b/test/lib/jit_support.rb
index 2f6d637ec9..3bca63a549 100644
--- a/test/lib/jit_support.rb
+++ b/test/lib/jit_support.rb
@@ -74,7 +74,7 @@ module JITSupport
   end
 
   def remove_mjit_logs(stderr)
-    if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # utility for -DFORCE_MJIT_ENABLE
+    if defined?(RubyVM::JIT) && RubyVM::JIT.enabled? # utility for -DFORCE_MJIT_ENABLE
       stderr.gsub(/^MJIT warning: Skipped to compile unsupported instruction: \w+\n/m, '')
     else
       stderr
diff --git a/test/net/ftp/test_ftp.rb b/test/net/ftp/test_ftp.rb
index 023e79435a..6cd32add90 100644
--- a/test/net/ftp/test_ftp.rb
+++ b/test/net/ftp/test_ftp.rb
@@ -762,7 +762,7 @@ class FTPTest < Test::Unit::TestCase
     begin
       begin
         ftp = Net::FTP.new
-        ftp.read_timeout *= 5 if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # for --jit-wait
+        ftp.read_timeout *= 5 if defined?(RubyVM::JIT) && RubyVM::JIT.enabled? # for --jit-wait
         ftp.connect(SERVER_ADDR, server.port)
         ftp.login
         assert_match(/\AUSER /, commands.shift)
@@ -807,7 +807,7 @@ class FTPTest < Test::Unit::TestCase
     begin
       begin
         ftp = Net::FTP.new
-        ftp.read_timeout *= 5 if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # for --jit-wait
+        ftp.read_timeout *= 5 if defined?(RubyVM::JIT) && RubyVM::JIT.enabled? # for --jit-wait
         ftp.connect(SERVER_ADDR, server.port)
         ftp.login
         assert_match(/\AUSER /, commands.shift)
@@ -1545,7 +1545,7 @@ EOF
     begin
       begin
         ftp = Net::FTP.new
-        ftp.read_timeout *= 5 if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # for --jit-wait
+        ftp.read_timeout *= 5 if defined?(RubyVM::JIT) && RubyVM::JIT.enabled? # for --jit-wait
         ftp.connect(SERVER_ADDR, server.port)
         assert_equal(['LANG EN*', 'UTF8'], ftp.features)
         assert_equal("FEAT\r\n", commands.shift)
@@ -1568,7 +1568,7 @@ EOF
     begin
       begin
         ftp = Net::FTP.new
-        ftp.read_timeout *= 5 if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # for --jit-wait
+        ftp.read_timeout *= 5 if defined?(RubyVM::JIT) && RubyVM::JIT.enabled? # for --jit-wait
         ftp.connect(SERVER_ADDR, server.port)
         assert_raise(Net::FTPPermError) do
           ftp.features
@@ -1594,7 +1594,7 @@ EOF
     begin
       begin
         ftp = Net::FTP.new
-        ftp.read_timeout *= 5 if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # for --jit-wait
+        ftp.read_timeout *= 5 if defined?(RubyVM::JIT) && RubyVM::JIT.enabled? # for --jit-wait
         ftp.connect(SERVER_ADDR, server.port)
         ftp.option("UTF8", "ON")
         assert_equal("OPTS UTF8 ON\r\n", commands.shift)
@@ -1653,7 +1653,7 @@ EOF
     begin
       begin
         ftp = Net::FTP.new
-        ftp.read_timeout *= 5 if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # for --jit-wait
+        ftp.read_timeout *= 5 if defined?(RubyVM::JIT) && RubyVM::JIT.enabled? # for --jit-wait
         ftp.connect(SERVER_ADDR, server.port)
         entry = ftp.mlst("foo")
         assert_equal("/foo", entry.pathname)
@@ -1740,7 +1740,7 @@ EOF
     begin
       begin
         ftp = Net::FTP.new
-        ftp.read_timeout *= 5 if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # for --jit-wait
+        ftp.read_timeout *= 5 if defined?(RubyVM::JIT) && RubyVM::JIT.enabled? # for --jit-wait
         ftp.connect(SERVER_ADDR, server.port)
         ftp.login
         assert_match(/\AUSER /, commands.shift)
@@ -1779,7 +1779,7 @@ EOF
 
   def test_parse257
     ftp = Net::FTP.new
-    ftp.read_timeout *= 5 if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # for --jit-wait
+    ftp.read_timeout *= 5 if defined?(RubyVM::JIT) && RubyVM::JIT.enabled? # for --jit-wait
     assert_equal('/foo/bar',
                  ftp.send(:parse257, '257 "/foo/bar" directory created'))
     assert_equal('/foo/bar"baz',
@@ -1918,7 +1918,7 @@ EOF
                          port: port,
                          ssl: { ca_file: CA_FILE },
                          passive: false)
-      ftp.read_timeout *= 5 if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # for --jit-wait
+      ftp.read_timeout *= 5 if defined?(RubyVM::JIT) && RubyVM::JIT.enabled? # for --jit-wait
       begin
         assert_equal("AUTH TLS\r\n", commands.shift)
         assert_equal("PBSZ 0\r\n", commands.shift)
@@ -2003,7 +2003,7 @@ EOF
                          port: port,
                          ssl: { ca_file: CA_FILE },
                          passive: true)
-      ftp.read_timeout *= 5 if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # for --jit-wait
+      ftp.read_timeout *= 5 if defined?(RubyVM::JIT) && RubyVM::JIT.enabled? # for --jit-wait
       begin
         assert_equal("AUTH TLS\r\n", commands.shift)
         assert_equal("PBSZ 0\r\n", commands.shift)
@@ -2079,7 +2079,7 @@ EOF
                          ssl: { ca_file: CA_FILE },
                          private_data_connection: false,
                          passive: false)
-      ftp.read_timeout *= 5 if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # for --jit-wait
+      ftp.read_timeout *= 5 if defined?(RubyVM::JIT) && RubyVM::JIT.enabled? # for --jit-wait
       begin
         assert_equal("AUTH TLS\r\n", commands.shift)
         ftp.login
@@ -2149,7 +2149,7 @@ EOF
                          ssl: { ca_file: CA_FILE },
                          private_data_connection: false,
                          passive: true)
-      ftp.read_timeout *= 5 if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # for --jit-wait
+      ftp.read_timeout *= 5 if defined?(RubyVM::JIT) && RubyVM::JIT.enabled? # for --jit-wait
       begin
         assert_equal("AUTH TLS\r\n", commands.shift)
         ftp.login
@@ -2230,7 +2230,7 @@ EOF
         ftp = Net::FTP.new(SERVER_NAME,
                            port: server.port,
                            ssl: { ca_file: CA_FILE })
-        ftp.read_timeout *= 5 if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # for --jit-wait
+        ftp.read_timeout *= 5 if defined?(RubyVM::JIT) && RubyVM::JIT.enabled? # for --jit-wait
         assert_equal("AUTH TLS\r\n", commands.shift)
         assert_equal("PBSZ 0\r\n", commands.shift)
         assert_equal("PROT P\r\n", commands.shift)
@@ -2283,7 +2283,7 @@ EOF
           begin
             ftp = Net::FTP.new
             ftp.resume = resume
-            ftp.read_timeout = (defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled?) ? 300 : 0.2 # use large timeout for --jit-wait
+            ftp.read_timeout = (defined?(RubyVM::JIT) && RubyVM::JIT.enabled?) ? 300 : 0.2 # use large timeout for --jit-wait
             ftp.connect(SERVER_ADDR, server.port)
             ftp.login
             assert_match(/\AUSER /, commands.shift)
@@ -2342,7 +2342,7 @@ EOF
       chdir_to_tmpdir do
         begin
           ftp = Net::FTP.new
-          ftp.read_timeout *= 5 if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # for --jit-wait
+          ftp.read_timeout *= 5 if defined?(RubyVM::JIT) && RubyVM::JIT.enabled? # for --jit-wait
           ftp.connect(SERVER_ADDR, server.port)
           ftp.login
           assert_match(/\AUSER /, commands.shift)
@@ -2393,7 +2393,7 @@ EOF
         File.binwrite("./|echo hello", binary_data)
         begin
           ftp = Net::FTP.new
-          ftp.read_timeout = RubyVM::MJIT.enabled? ? 300 : 0.2 # use large timeout for --jit-wait
+          ftp.read_timeout = RubyVM::JIT.enabled? ? 300 : 0.2 # use large timeout for --jit-wait
           ftp.connect(SERVER_ADDR, server.port)
           ftp.login
           assert_match(/\AUSER /, commands.shift)
@@ -2448,7 +2448,7 @@ EOF
         end
         begin
           ftp = Net::FTP.new
-          ftp.read_timeout *= 5 if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # for --jit-wait
+          ftp.read_timeout *= 5 if defined?(RubyVM::JIT) && RubyVM::JIT.enabled? # for --jit-wait
           ftp.connect(SERVER_ADDR, server.port)
           ftp.login
           assert_match(/\AUSER /, commands.shift)
diff --git a/test/net/http/test_httpresponse.rb b/test/net/http/test_httpresponse.rb
index a70a9bce34..5063384569 100644
--- a/test/net/http/test_httpresponse.rb
+++ b/test/net/http/test_httpresponse.rb
@@ -78,7 +78,7 @@ EOS
 
   def test_read_body_block_mod
     # http://ci.rvm.jp/results/trunk-mjit-wait@silicon-docker/3019353
-    skip 'too unstable with --jit-wait, and extending read_timeout did not help it' if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled?
+    skip 'too unstable with --jit-wait, and extending read_timeout did not help it' if defined?(RubyVM::JIT) && RubyVM::JIT.enabled?
     IO.pipe do |r, w|
       buf = 'x' * 1024
       buf.freeze
diff --git a/test/net/smtp/test_smtp.rb b/test/net/smtp/test_smtp.rb
index e909909dec..9b044ec1a2 100644
--- a/test/net/smtp/test_smtp.rb
+++ b/test/net/smtp/test_smtp.rb
@@ -31,7 +31,7 @@ module Net
     def setup
       # Avoid hanging at fake_server_start's IO.select on --jit-wait CI like http://ci.rvm.jp/results/trunk-mjit-wait@phosphorus-docker/3302796
       # Unfortunately there's no way to configure read_timeout for Net::SMTP.start.
-      if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled?
+      if defined?(RubyVM::JIT) && RubyVM::JIT.enabled?
         Net::SMTP.prepend Module.new {
           def initialize(*)
             super
diff --git a/test/reline/test_within_pipe.rb b/test/reline/test_within_pipe.rb
index 70a0e0a5de..4a46c9c9f1 100644
--- a/test/reline/test_within_pipe.rb
+++ b/test/reline/test_within_pipe.rb
@@ -8,7 +8,7 @@ class Reline::WithinPipeTest < Reline::TestCase
     @reader, @output_writer = IO.pipe((RELINE_TEST_ENCODING rescue Encoding.default_external))
     @output = Reline.output = @output_writer
     @config = Reline.send(:core).config
-    @config.keyseq_timeout *= 600 if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # for --jit-wait CI
+    @config.keyseq_timeout *= 600 if defined?(RubyVM::JIT) && RubyVM::JIT.enabled? # for --jit-wait CI
     @line_editor = Reline.send(:core).line_editor
   end
 
diff --git a/test/rinda/test_rinda.rb b/test/rinda/test_rinda.rb
index 00e1ba7877..f155e88de1 100644
--- a/test/rinda/test_rinda.rb
+++ b/test/rinda/test_rinda.rb
@@ -402,7 +402,7 @@ module TupleSpaceTestModule
   end
 
   def test_cancel_02
-    skip 'this test is unstable with --jit-wait' if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled?
+    skip 'this test is unstable with --jit-wait' if defined?(RubyVM::JIT) && RubyVM::JIT.enabled?
     entry = @ts.write([:removeme, 1])
     assert_equal([[:removeme, 1]], @ts.read_all([nil, nil]))
     entry.cancel
@@ -662,7 +662,7 @@ class TestRingServer < Test::Unit::TestCase
   end
 
   def test_do_reply_local
-    skip 'timeout-based test becomes unstable with --jit-wait' if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled?
+    skip 'timeout-based test becomes unstable with --jit-wait' if defined?(RubyVM::JIT) && RubyVM::JIT.enabled?
     with_timeout(30) {_test_do_reply_local}
   end
 
diff --git a/test/ruby/test_fiber.rb b/test/ruby/test_fiber.rb
index ff4658a20b..a5e35c0fd6 100644
--- a/test/ruby/test_fiber.rb
+++ b/test/ruby/test_fiber.rb
@@ -34,7 +34,7 @@ class TestFiber < Test::Unit::TestCase
   end
 
   def test_many_fibers
-    skip 'This is unstable on GitHub Actions --jit-wait. TODO: debug it' if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled?
+    skip 'This is unstable on GitHub Actions --jit-wait. TODO: debug it' if defined?(RubyVM::JIT) && RubyVM::JIT.enabled?
     max = 10_000
     assert_equal(max, max.times{
       Fiber.new{}
diff --git a/test/ruby/test_io.rb b/test/ruby/test_io.rb
index 9f9318eaf7..42149ac32a 100644
--- a/test/ruby/test_io.rb
+++ b/test/ruby/test_io.rb
@@ -607,7 +607,7 @@ class TestIO < Test::Unit::TestCase
 
   if have_nonblock?
     def test_copy_stream_no_busy_wait
-      skip "MJIT has busy wait on GC. This sometimes fails with --jit." if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled?
+      skip "MJIT has busy wait on GC. This sometimes fails with --jit." if defined?(RubyVM::JIT) && RubyVM::JIT.enabled?
       skip "multiple threads already active" if Thread.list.size > 1
 
       msg = 'r58534 [ruby-core:80969] [Backport #13533]'
@@ -1562,7 +1562,7 @@ class TestIO < Test::Unit::TestCase
   end if have_nonblock?
 
   def test_read_nonblock_no_exceptions
-    skip '[ruby-core:90895] MJIT worker may leave fd open in a forked child' if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # TODO: consider acquiring GVL from MJIT worker.
+    skip '[ruby-core:90895] MJIT worker may leave fd open in a forked child' if defined?(RubyVM::JIT) && RubyVM::JIT.enabled? # TODO: consider acquiring GVL from MJIT worker.
     with_pipe {|r, w|
       assert_equal :wait_readable, r.read_nonblock(4096, exception: false)
       w.puts "HI!"
@@ -2210,7 +2210,7 @@ class TestIO < Test::Unit::TestCase
   def test_autoclose_true_closed_by_finalizer
     # http://ci.rvm.jp/results/trunk-mjit@silicon-docker/1465760
     # http://ci.rvm.jp/results/trunk-mjit@silicon-docker/1469765
-    skip 'this randomly fails with MJIT' if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled?
+    skip 'this randomly fails with MJIT' if defined?(RubyVM::JIT) && RubyVM::JIT.enabled?
 
     feature2250 = '[ruby-core:26222]'
     pre = 'ft2250'
diff --git a/test/ruby/test_jit.rb b/test/ruby/test_jit.rb
index 3bc4a871a1..54f9698afa 100644
--- a/test/ruby/test_jit.rb
+++ b/test/ruby/test_jit.rb
@@ -1085,7 +1085,7 @@ class TestJIT < Test::Unit::TestCase
   def test_mjit_pause_wait
     assert_eval_with_jit("#{<<~"begin;"}\n#{<<~"end;"}", stdout: '', success_count: 0, min_calls: 1)
     begin;
-      RubyVM::MJIT.pause
+      RubyVM::JIT.pause
       proc {}.call
     end;
   end
diff --git a/test/ruby/test_optimization.rb b/test/ruby/test_optimization.rb
index d0790c7463..b0090d654a 100644
--- a/test/ruby/test_optimization.rb
+++ b/test/ruby/test_optimization.rb
@@ -452,7 +452,7 @@ class TestRubyOptimization < Test::Unit::TestCase
   end
 
   def test_tailcall_not_to_grow_stack
-    skip 'currently JIT-ed code always creates a new stack frame' if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled?
+    skip 'currently JIT-ed code always creates a new stack frame' if defined?(RubyVM::JIT) && RubyVM::JIT.enabled?
     bug16161 = '[ruby-core:94881]'
 
     tailcall("#{<<-"begin;"}\n#{<<~"end;"}")
diff --git a/test/ruby/test_process.rb b/test/ruby/test_process.rb
index d1b9d8a478..33144aa62f 100644
--- a/test/ruby/test_process.rb
+++ b/test/ruby/test_process.rb
@@ -1706,7 +1706,7 @@ class TestProcess < Test::Unit::TestCase
       Process.wait pid
       assert_send [sig_r, :wait_readable, 5], 'self-pipe not readable'
     end
-    if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # checking -DMJIT_FORCE_ENABLE. It may trigger extra SIGCHLD.
+    if defined?(RubyVM::JIT) && RubyVM::JIT.enabled? # checking -DMJIT_FORCE_ENABLE. It may trigger extra SIGCHLD.
       assert_equal [true], signal_received.uniq, "[ruby-core:19744]"
     else
       assert_equal [true], signal_received, "[ruby-core:19744]"
diff --git a/test/ruby/test_rubyoptions.rb b/test/ruby/test_rubyoptions.rb
index b7831948f0..d860bf4a15 100644
--- a/test/ruby/test_rubyoptions.rb
+++ b/test/ruby/test_rubyoptions.rb
@@ -8,7 +8,7 @@ require_relative '../lib/jit_support'
 
 class TestRubyOptions < Test::Unit::TestCase
   NO_JIT_DESCRIPTION =
-    if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # checking -DMJIT_FORCE_ENABLE
+    if defined?(RubyVM::JIT) && RubyVM::JIT.enabled? # checking -DMJIT_FORCE_ENABLE
       RUBY_DESCRIPTION.sub(/\+JIT /, '')
     else
       RUBY_DESCRIPTION
@@ -128,7 +128,7 @@ class TestRubyOptions < Test::Unit::TestCase
   def test_verbose
     assert_in_out_err(["-vve", ""]) do |r, e|
       assert_match(VERSION_PATTERN, r[0])
-      if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? && !mjit_force_enabled? # checking -DMJIT_FORCE_ENABLE
+      if defined?(RubyVM::JIT) && RubyVM::JIT.enabled? && !mjit_force_enabled? # checking -DMJIT_FORCE_ENABLE
         assert_equal(NO_JIT_DESCRIPTION, r[0])
       else
         assert_equal(RUBY_DESCRIPTION, r[0])
@@ -191,7 +191,7 @@ class TestRubyOptions < Test::Unit::TestCase
   def test_version
     assert_in_out_err(%w(--version)) do |r, e|
       assert_match(VERSION_PATTERN, r[0])
-      if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # checking -DMJIT_FORCE_ENABLE
+      if defined?(RubyVM::JIT) && RubyVM::JIT.enabled? # checking -DMJIT_FORCE_ENABLE
         assert_equal(EnvUtil.invoke_ruby(['-e', 'print RUBY_DESCRIPTION'], '', true).first, r[0])
       else
         assert_equal(RUBY_DESCRIPTION, r[0])
@@ -221,7 +221,7 @@ class TestRubyOptions < Test::Unit::TestCase
       ].each do |args|
         assert_in_out_err(args) do |r, e|
           assert_match(VERSION_PATTERN_WITH_JIT, r[0])
-          if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # checking -DMJIT_FORCE_ENABLE
+          if defined?(RubyVM::JIT) && RubyVM::JIT.enabled? # checking -DMJIT_FORCE_ENABLE
             assert_equal(RUBY_DESCRIPTION, r[0])
           else
             assert_equal(EnvUtil.invoke_ruby(['--jit', '-e', 'print RUBY_DESCRIPTION'], '', true).first, r[0])
diff --git a/test/ruby/test_rubyvm_mjit.rb b/test/ruby/test_rubyvm_jit.rb
index ef7475670c..2104ce3d18 100644
--- a/test/ruby/test_rubyvm_mjit.rb
+++ b/test/ruby/test_rubyvm_jit.rb
@@ -4,7 +4,7 @@ require_relative '../lib/jit_support'
 
 return if RbConfig::CONFIG["MJIT_SUPPORT"] == 'no'
 
-class TestRubyVMMJIT < Test::Unit::TestCase
+class TestRubyVMJIT < Test::Unit::TestCase
   include JITSupport
 
   def setup
@@ -20,13 +20,13 @@ class TestRubyVMMJIT < Test::Unit::TestCase
         eval("def mjit#{i}; end; mjit#{i}")
         i += 1
       end
-      print RubyVM::MJIT.pause
-      print RubyVM::MJIT.pause
+      print RubyVM::JIT.pause
+      print RubyVM::JIT.pause
       while i < 10
         eval("def mjit#{i}; end; mjit#{i}")
         i += 1
       end
-      print RubyVM::MJIT.pause # no JIT here
+      print RubyVM::JIT.pause # no JIT here
     EOS
     assert_equal('truefalsefalse', out)
     assert_equal(
@@ -39,7 +39,7 @@ class TestRubyVMMJIT < Test::Unit::TestCase
     out, err = eval_with_jit(<<~'EOS', verbose: 1, min_calls: 1, wait: false)
       def a() end; a
       def b() end; b
-      RubyVM::MJIT.pause
+      RubyVM::JIT.pause
     EOS
     assert_equal(
       2, err.scan(/#{JITSupport::JIT_SUCCESS_PREFIX}/).size,
@@ -58,7 +58,7 @@ class TestRubyVMMJIT < Test::Unit::TestCase
         eval("def mjit#{i}; end; mjit#{i}")
         i += 1
       end
-      print RubyVM::MJIT.pause
+      print RubyVM::JIT.pause
     EOS
     assert_equal('true', out)
   end
@@ -70,8 +70,8 @@ class TestRubyVMMJIT < Test::Unit::TestCase
         eval("def mjit#{i}; end; mjit#{i}")
         i += 1
       end
-      print RubyVM::MJIT.pause(wait: false)
-      print RubyVM::MJIT.pause(wait: false)
+      print RubyVM::JIT.pause(wait: false)
+      print RubyVM::JIT.pause(wait: false)
     EOS
     assert_equal('truefalse', out)
     assert_equal(true, err.scan(/#{JITSupport::JIT_SUCCESS_PREFIX}/).size < 10)
@@ -79,11 +79,11 @@ class TestRubyVMMJIT < Test::Unit::TestCase
 
   def test_resume
     out, err = eval_with_jit(<<~'EOS', verbose: 1, min_calls: 1, wait: false)
-      print RubyVM::MJIT.resume
-      print RubyVM::MJIT.pause
-      print RubyVM::MJIT.resume
-      print RubyVM::MJIT.resume
-      print RubyVM::MJIT.pause
+      print RubyVM::JIT.resume
+      print RubyVM::JIT.pause
+      print RubyVM::JIT.resume
+      print RubyVM::JIT.resume
+      print RubyVM::JIT.pause
     EOS
     assert_equal('falsetruetruefalsetrue', out)
     assert_equal(0, err.scan(/#{JITSupport::JIT_SUCCESS_PREFIX}/).size)
diff --git a/test/ruby/test_settracefunc.rb b/test/ruby/test_settracefunc.rb
index 7821a221dc..1d16b2e154 100644
--- a/test/ruby/test_settracefunc.rb
+++ b/test/ruby/test_settracefunc.rb
@@ -1963,7 +1963,7 @@ class TestSetTraceFunc < Test::Unit::TestCase
     Thread.pass until t.status == 'sleep'
     # When MJIT thread exists, t.status becomes 'sleep' even if it does not reach m2t_q.pop.
     # This sleep forces it to reach m2t_q.pop for --jit-wait.
-    sleep 1 if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled?
+    sleep 1 if defined?(RubyVM::JIT) && RubyVM::JIT.enabled?
 
     t.add_trace_func proc{|ev, file, line, *args|
       if file == __FILE__
diff --git a/test/ruby/test_thread.rb b/test/ruby/test_thread.rb
index 3852cb7020..6005e5b001 100644
--- a/test/ruby/test_thread.rb
+++ b/test/ruby/test_thread.rb
@@ -309,7 +309,7 @@ class TestThread < Test::Unit::TestCase
       s += 1
     end
     Thread.pass until t.stop?
-    sleep 1 if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # t.stop? behaves unexpectedly with --jit-wait
+    sleep 1 if defined?(RubyVM::JIT) && RubyVM::JIT.enabled? # t.stop? behaves unexpectedly with --jit-wait
     assert_equal(1, s)
     t.wakeup
     Thread.pass while t.alive?
@@ -1338,7 +1338,7 @@ q.pop
     opts = { timeout: 5, timeout_error: nil }
 
     # prevent SIGABRT from slow shutdown with MJIT
-    opts[:reprieve] = 3 if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled?
+    opts[:reprieve] = 3 if defined?(RubyVM::JIT) && RubyVM::JIT.enabled?
 
     assert_normal_exit(<<-_end, '[Bug #8996]', **opts)
       Thread.report_on_exception = false
diff --git a/test/rubygems/test_gem_stream_ui.rb b/test/rubygems/test_gem_stream_ui.rb
index ca6dbc6a8b..e154a723c9 100644
--- a/test/rubygems/test_gem_stream_ui.rb
+++ b/test/rubygems/test_gem_stream_ui.rb
@@ -5,7 +5,7 @@ require 'timeout'
 
 class TestGemStreamUI < Gem::TestCase
   # increase timeout with MJIT for --jit-wait testing
-  mjit_enabled = defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled?
+  mjit_enabled = defined?(RubyVM::JIT) && RubyVM::JIT.enabled?
   SHORT_TIMEOUT = (RUBY_ENGINE == "ruby" && !mjit_enabled) ? 0.1 : 1.0
 
   module IsTty
diff --git a/test/socket/test_socket.rb b/test/socket/test_socket.rb
index 49587dc244..9cef9f0d6f 100644
--- a/test/socket/test_socket.rb
+++ b/test/socket/test_socket.rb
@@ -478,7 +478,7 @@ class TestSocket < Test::Unit::TestCase
         end while IO.select([r], nil, nil, 0.1).nil?
         n
       end
-      timeout = (defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? ? 120 : 30) # for --jit-wait
+      timeout = (defined?(RubyVM::JIT) && RubyVM::JIT.enabled? ? 120 : 30) # for --jit-wait
       assert_equal([[s1],[],[]], IO.select([s1], nil, nil, timeout))
       msg, _, _, stamp = s1.recvmsg
       assert_equal("a", msg)
diff --git a/tool/lib/minitest/unit.rb b/tool/lib/minitest/unit.rb
index f70762e5d5..ddd7cfe74d 100644
--- a/tool/lib/minitest/unit.rb
+++ b/tool/lib/minitest/unit.rb
@@ -973,7 +973,7 @@ module MiniTest
           puts if @verbose
           $stdout.flush
 
-          unless defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # compiler process is wrongly considered as leak
+          unless defined?(RubyVM::JIT) && RubyVM::JIT.enabled? # compiler process is wrongly considered as leak
             leakchecker.check("#{inst.class}\##{inst.__name__}")
           end
 
diff --git a/tool/lib/test/unit/core_assertions.rb b/tool/lib/test/unit/core_assertions.rb
index abd0e45035..118c0d111b 100644
--- a/tool/lib/test/unit/core_assertions.rb
+++ b/tool/lib/test/unit/core_assertions.rb
@@ -115,7 +115,7 @@ module Test
 
       def assert_no_memory_leak(args, prepare, code, message=nil, limit: 2.0, rss: false, **opt)
         # TODO: consider choosing some appropriate limit for MJIT and stop skipping this once it does not randomly fail
-        pend 'assert_no_memory_leak may consider MJIT memory usage as leak' if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled?
+        pend 'assert_no_memory_leak may consider MJIT memory usage as leak' if defined?(RubyVM::JIT) && RubyVM::JIT.enabled?
 
         require_relative '../../memory_status'
         raise MiniTest::Skip, "unsupported platform" unless defined?(Memory::Status)
diff --git a/tool/test/testunit/test_hideskip.rb b/tool/test/testunit/test_hideskip.rb
index 13d887189e..e90be5da32 100644
--- a/tool/test/testunit/test_hideskip.rb
+++ b/tool/test/testunit/test_hideskip.rb
@@ -6,7 +6,7 @@ class TestHideSkip < Test::Unit::TestCase
     assert_not_match(/^ *1\) Skipped/, hideskip)
     assert_match(/^ *1\) Skipped/, hideskip("--show-skip"))
     output = hideskip("--hide-skip")
-    output.gsub!(/Successful MJIT finish\n/, '') if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled?
+    output.gsub!(/Successful MJIT finish\n/, '') if defined?(RubyVM::JIT) && RubyVM::JIT.enabled?
     assert_match(/assertions\/s.\n+1 tests, 0 assertions, 0 failures, 0 errors, 1 skips/, output)
   end
 
diff --git a/tool/test/testunit/test_parallel.rb b/tool/test/testunit/test_parallel.rb
index 44e9eb18d8..fa87ca53ab 100644
--- a/tool/test/testunit/test_parallel.rb
+++ b/tool/test/testunit/test_parallel.rb
@@ -6,7 +6,7 @@ module TestParallel
   PARALLEL_RB = "#{File.dirname(__FILE__)}/../../lib/test/unit/parallel.rb"
   TESTS = "#{File.dirname(__FILE__)}/tests_for_parallel"
   # use large timeout for --jit-wait
-  TIMEOUT = EnvUtil.apply_timeout_scale(defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? ? 100 : 30)
+  TIMEOUT = EnvUtil.apply_timeout_scale(defined?(RubyVM::JIT) && RubyVM::JIT.enabled? ? 100 : 30)
 
   class TestParallelWorker < Test::Unit::TestCase
     def setup
diff --git a/tool/test/webrick/test_httpserver.rb b/tool/test/webrick/test_httpserver.rb
index 4133be85ad..f905ff04e8 100644
--- a/tool/test/webrick/test_httpserver.rb
+++ b/tool/test/webrick/test_httpserver.rb
@@ -253,7 +253,7 @@ class TestWEBrickHTTPServer < Test::Unit::TestCase
       server.virtual_host(WEBrick::HTTPServer.new(vhost_config))
 
       Thread.pass while server.status != :Running
-      sleep 1 if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # server.status behaves unexpectedly with --jit-wait
+      sleep 1 if defined?(RubyVM::JIT) && RubyVM::JIT.enabled? # server.status behaves unexpectedly with --jit-wait
       assert_equal(1, started, log.call)
       assert_equal(0, stopped, log.call)
       assert_equal(0, accepted, log.call)
diff --git a/tool/test/webrick/test_server.rb b/tool/test/webrick/test_server.rb
index 815cc3ce39..0fd3f3b63b 100644
--- a/tool/test/webrick/test_server.rb
+++ b/tool/test/webrick/test_server.rb
@@ -65,7 +65,7 @@ class TestWEBrickServer < Test::Unit::TestCase
     }
     TestWEBrick.start_server(Echo, config){|server, addr, port, log|
       true while server.status != :Running
-      sleep 1 if defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? # server.status behaves unexpectedly with --jit-wait
+      sleep 1 if defined?(RubyVM::JIT) && RubyVM::JIT.enabled? # server.status behaves unexpectedly with --jit-wait
       assert_equal(1, started, log.call)
       assert_equal(0, stopped, log.call)
       assert_equal(0, accepted, log.call)
diff --git a/vm.c b/vm.c
index faea6885a8..5beb6d0df4 100644
--- a/vm.c
+++ b/vm.c
@@ -3198,13 +3198,13 @@ core_hash_merge_kwd(VALUE hash, VALUE kw)
 
 /* Returns true if JIT is enabled */
 static VALUE
-mjit_enabled_p(VALUE _)
+jit_enabled_p(VALUE _)
 {
     return mjit_enabled ? Qtrue : Qfalse;
 }
 
 static VALUE
-mjit_pause_m(int argc, VALUE *argv, RB_UNUSED_VAR(VALUE self))
+jit_pause_m(int argc, VALUE *argv, RB_UNUSED_VAR(VALUE self))
 {
     VALUE options = Qnil;
     VALUE wait = Qtrue;
@@ -3221,7 +3221,7 @@ mjit_pause_m(int argc, VALUE *argv, RB_UNUSED_VAR(VALUE self))
 }
 
 static VALUE
-mjit_resume_m(VALUE _)
+jit_resume_m(VALUE _)
 {
     return mjit_resume();
 }
@@ -3317,7 +3317,7 @@ Init_VM(void)
     VALUE opts;
     VALUE klass;
     VALUE fcore;
-    VALUE mjit;
+    VALUE jit;
 
     /*
      * Document-class: RubyVM
@@ -3362,14 +3362,17 @@ Init_VM(void)
     rb_gc_register_mark_object(fcore);
     rb_mRubyVMFrozenCore = fcore;
 
-    /* ::RubyVM::MJIT
+    /* ::RubyVM::JIT
      * Provides access to the Method JIT compiler of MRI.
      * Of course, this module is MRI specific.
      */
-    mjit = rb_define_module_under(rb_cRubyVM, "MJIT");
-    rb_define_singleton_method(mjit, "enabled?", mjit_enabled_p, 0);
-    rb_define_singleton_method(mjit, "pause", mjit_pause_m, -1);
-    rb_define_singleton_method(mjit, "resume", mjit_resume_m, 0);
+    jit = rb_define_module_under(rb_cRubyVM, "JIT");
+    rb_define_singleton_method(jit, "enabled?", jit_enabled_p, 0);
+    rb_define_singleton_method(jit, "pause", jit_pause_m, -1);
+    rb_define_singleton_method(jit, "resume", jit_resume_m, 0);
+    /* RubyVM::MJIT for short-term backward compatibility */
+    rb_const_set(rb_cRubyVM, rb_intern("MJIT"), jit);
+    rb_deprecate_constant(rb_cRubyVM, "MJIT");
 
     /*
      * Document-class: Thread