version.c: show +JIT when --jit is passed

in version output.
version.h: ditto
ruby.c: propagate option for it
common.mk: updated dependency for version.c

mjit.c: overwrites the RUBY_DESCRIPTION to have +JIT when --jit is passed

test/ruby/test_rubyoptions.rb: add test for them

Only `ruby --jit -v` will have "+JIT", but this is intentional.
This may not be convenient for debugging by ticket with `ruby -v`,
but it's convenient for benchmark tools that pass options (--jit)
when showing it. At least such behavior is planned for benchmark_driver.gem
and this behavior is designed for it. Other benchmark tools are
recommended to follow the behavior too if they show version.
RUBY_DESCRIPTION might be useful for it too.

The position of "+JIT" is changed from original proposal because other
platforms like JRuby and TruffleRuby end it with archtecture.
It's made similar to JRuby, but it's upper-cased because Matz made approval
for "+JIT" in the ticket.

Example:
$ ruby -v
ruby 2.6.0dev (2018-02-22 trunk 62529) [x86_64-linux]
$ ruby --jit -v
ruby 2.6.0dev (2018-02-22 trunk 62529) +JIT [x86_64-linux]

After --jit is made default in the future, this output may be removed.
So do not rely on this output if possible.

[Feature #14462]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@62530 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

common.mk

@@ -2847,9 +2847,11 @@ version.$(OBJEXT): {$(VPATH)}config.h
 version.$(OBJEXT): {$(VPATH)}defines.h
 version.$(OBJEXT): {$(VPATH)}intern.h
 version.$(OBJEXT): {$(VPATH)}missing.h
+version.$(OBJEXT): {$(VPATH)}mjit.h
 version.$(OBJEXT): {$(VPATH)}st.h
 version.$(OBJEXT): {$(VPATH)}subst.h
 version.$(OBJEXT): {$(VPATH)}version.c
+version.$(OBJEXT): {$(VPATH)}vm_core.h
 vm.$(OBJEXT): $(CCAN_DIR)/check_type/check_type.h
 vm.$(OBJEXT): $(CCAN_DIR)/container_of/container_of.h
 vm.$(OBJEXT): $(CCAN_DIR)/list/list.h

mjit.c

@@ -1314,12 +1314,16 @@ system_tmpdir(void)
 /* Minimum value for JIT cache size.  */
 #define MIN_CACHE_SIZE 10
 
+extern const char ruby_description_with_jit[];
+
 /* Initialize MJIT.  Start a thread creating the precompiled header and
    processing ISeqs.  The function should be called first for using MJIT.
    If everything is successfull, MJIT_INIT_P will be TRUE.  */
 void
 mjit_init(struct mjit_options *opts)
 {
+    VALUE rb_description;
+
     mjit_opts = *opts;
     mjit_init_p = TRUE;
 
@@ -1366,6 +1370,11 @@ mjit_init(struct mjit_options *opts)
         rb_id_table_foreach(RCLASS_CONST_TBL(rb_cObject), valid_class_serials_add_i, NULL);
     }
 
+    /* Overwrites RUBY_DESCRIPTION constant */
+    rb_const_remove(rb_cObject, rb_intern("RUBY_DESCRIPTION"));
+    rb_description = rb_usascii_str_new_static(ruby_description_with_jit, strlen(ruby_description_with_jit));
+    rb_define_global_const("RUBY_DESCRIPTION", rb_obj_freeze(rb_description));
+
     /* Initialize worker thread */
     finish_worker_p = FALSE;
     worker_finished = FALSE;

ruby.c

@@ -1506,6 +1506,10 @@ process_options(int argc, char **argv, ruby_cmdline_options_t *opt)
     const struct rb_block *base_block;
     unsigned int dump = opt->dump & dump_exit_bits;
 
+#ifndef MJIT_FORCE_ENABLE /* to use with: ./configure cppflags="-DMJIT_FORCE_ENABLE" */
+    opt->mjit.on = 1;
+#endif
+
     if (opt->dump & (DUMP_BIT(usage)|DUMP_BIT(help))) {
 	const char *const progname =
 	    (argc > 0 && argv && argv[0] ? argv[0] :
@@ -1538,6 +1542,7 @@ process_options(int argc, char **argv, ruby_cmdline_options_t *opt)
 	rb_warning("-K is specified; it is for 1.8 compatibility and may cause odd behavior");
 
     if (opt->dump & (DUMP_BIT(version) | DUMP_BIT(version_v))) {
+        mjit_opts.on = opt->mjit.on; /* used by ruby_show_version(). mjit_init() is still not called here. */
 	ruby_show_version();
 	if (opt->dump & DUMP_BIT(version)) return Qtrue;
     }
@@ -1590,9 +1595,7 @@ process_options(int argc, char **argv, ruby_cmdline_options_t *opt)
     ruby_gc_set_params(opt->safe_level);
     ruby_init_loadpath_safe(opt->safe_level);
 
-#ifndef MJIT_FORCE_ENABLE /* to use with: ./configure cppflags="-DMJIT_FORCE_ENABLE" */
     if (opt->mjit.on)
-#endif
         /* Using TMP_RUBY_PREFIX created by ruby_init_loadpath_safe(). */
         mjit_init(&opt->mjit);
 

test/ruby/test_rubyoptions.rb

@@ -96,6 +96,15 @@ class TestRubyOptions < Test::Unit::TestCase
     end
   private_constant :VERSION_PATTERN
 
+  VERSION_PATTERN_WITH_JIT =
+    case RUBY_ENGINE
+    when 'jruby'
+      VERSIN_PATTERN
+    else
+      /^ruby #{q[RUBY_VERSION]}(?:[p ]|dev|rc).*? \+JIT \[#{q[RUBY_PLATFORM]}\]$/
+    end
+  private_constant :VERSION_PATTERN_WITH_JIT
+
   def test_verbose
     assert_in_out_err(["-vve", ""]) do |r, e|
       assert_match(VERSION_PATTERN, r[0])
@@ -155,7 +164,20 @@ class TestRubyOptions < Test::Unit::TestCase
   def test_version
     assert_in_out_err(%w(--version)) do |r, e|
       assert_match(VERSION_PATTERN, r[0])
-      assert_equal(RUBY_DESCRIPTION, r[0])
+      if RubyVM::MJIT.enabled?
+        assert_equal(EnvUtil.invoke_ruby(['-e', 'print RUBY_DESCRIPTION'], '', true).first, r[0])
+      else
+        assert_equal(RUBY_DESCRIPTION, r[0])
+      end
+      assert_equal([], e)
+    end
+    assert_in_out_err(%w(--version --jit)) do |r, e|
+      assert_match(VERSION_PATTERN_WITH_JIT, r[0])
+      if RubyVM::MJIT.enabled?
+        assert_equal(RUBY_DESCRIPTION, r[0])
+      else
+        assert_equal(EnvUtil.invoke_ruby(['--jit', '-e', 'print RUBY_DESCRIPTION'], '', true).first, r[0])
+      end
       assert_equal([], e)
     end
   end

version.c

@@ -11,6 +11,8 @@
 
 #include "ruby/ruby.h"
 #include "version.h"
+#include "vm_core.h"
+#include "mjit.h"
 #include <stdio.h>
 
 #ifndef EXIT_SUCCESS
@@ -31,6 +33,7 @@ const char ruby_release_date[] = RUBY_RELEASE_DATE;
 const char ruby_platform[] = RUBY_PLATFORM;
 const int ruby_patchlevel = RUBY_PATCHLEVEL;
 const char ruby_description[] = RUBY_DESCRIPTION;
+const char ruby_description_with_jit[] = RUBY_DESCRIPTION_WITH_JIT;
 const char ruby_copyright[] = RUBY_COPYRIGHT;
 const char ruby_engine[] = "ruby";
 
@@ -65,6 +68,7 @@ Init_version(void)
     rb_define_global_const("RUBY_REVISION", MKINT(revision));
     /*
      * The full ruby version string, like <tt>ruby -v</tt> prints'
+     * This might be overwritten by mjit_init().
      */
     rb_define_global_const("RUBY_DESCRIPTION", MKSTR(description));
     /*
@@ -86,7 +90,12 @@ Init_version(void)
 void
 ruby_show_version(void)
 {
-    PRINT(description);
+    if (mjit_opts.on) {
+        PRINT(description_with_jit);
+    }
+    else {
+        PRINT(description);
+    }
 #ifdef RUBY_LAST_COMMIT_TITLE
     fputs("last_commit=" RUBY_LAST_COMMIT_TITLE, stdout);
 #endif

version.h

@@ -66,6 +66,12 @@
     " ("RUBY_RELEASE_DATE	    \
     RUBY_REVISION_STR") "	    \
     "["RUBY_PLATFORM"]"
+# define RUBY_DESCRIPTION_WITH_JIT  \
+    "ruby "RUBY_VERSION             \
+    RUBY_PATCHLEVEL_STR             \
+    " ("RUBY_RELEASE_DATE           \
+    RUBY_REVISION_STR") +JIT "      \
+    "["RUBY_PLATFORM"]"
 # define RUBY_COPYRIGHT		    \
     "ruby - Copyright (C) "	    \
     RUBY_BIRTH_YEAR_STR"-"   \