Update documentation about RJIT

doc/rjit/rjit.md

@@ -4,17 +4,10 @@ This document has some tips that might be useful when you work on RJIT.
 
 ## Supported platforms
 
-The following platforms are either tested on CI or assumed to work.
+The following platforms are assumed to work. `linux-x86_64` is tested on CI.
 
-* OS: Linux, macOS
-* Arch: x86\_64, aarch64, arm64, i686, i386
-
-### Not supported
-
-The RJIT support for the following platforms is no longer maintained.
-
-* OS: Windows (mswin, MinGW), Solaris
-* Arch: SPARC, s390x
+* OS: Linux, macOS, BSD
+* Arch: x86\_64
 
 ## Developing RJIT
 
@@ -25,15 +18,14 @@ If you see an "RJIT bindgen" GitHub Actions failure, please commit the `git diff
 For doing the same thing locally, run `make rjit-bindgen` after installing libclang.
 macOS seems to have libclang by default. On Ubuntu, you can install it with `apt install libclang1`.
 
-### Always run make install
+### --enable-rjit
 
-Always run `make install` before running RJIT. It could easily cause a SEGV if you don't.
-RJIT looks for the installed header for security reasons.
+On supported platforms, `--enable-rjit` is set by default. You usually don't need to specify this.
+You may still manually pass `--enable-rjit` to try RJIT on unsupported platforms.
 
-### --rjit-debug vs --rjit-debug=-ggdb3
+### --enable-rjit=dev
 
-`--rjit-debug=[flags]` allows you to specify arbitrary flags while keeping other compiler flags like `-O3`,
-which is useful for profiling benchmarks.
+`--enable-rjit=dev` makes the interpreter slower, but enables the following two features:
 
-`--rjit-debug` alone, on the other hand, disables `-O3` and adds debug flags.
-If you're debugging RJIT, what you need to use is not `--rjit-debug=-ggdb3` but `--rjit-debug`.
+* `--rjit-dump-disasm`: Dump all JIT code.
+* `--rjit-stats`: Print RJIT stats.

rjit.c

@@ -225,9 +225,11 @@ rjit_setup_options(const char *s, struct rjit_options *rjit_opt)
 
 #define M(shortopt, longopt, desc) RUBY_OPT_MESSAGE(shortopt, longopt, desc)
 const struct ruby_opt_message rjit_option_messages[] = {
+#if RJIT_STATS
     M("--rjit-stats",              "", "Enable collecting RJIT statistics"),
+#endif
     M("--rjit-call-threshold=num", "", "Number of calls to trigger JIT (default: " STRINGIZE(DEFAULT_CALL_THRESHOLD) ")"),
-#if RUBY_DEBUG
+#ifdef HAVE_LIBCAPSTONE
     M("--rjit-dump-disasm",        "", "Dump all JIT code"),
 #endif
     {0}

ruby.c

@@ -286,11 +286,11 @@ usage(const char *name, int help, int highlight, int columns)
         M("-W[level=2|:category]",   "",	   "set warning level; 0=silence, 1=medium, 2=verbose"),
         M("-x[directory]", "",			   "strip off text before #!ruby line and perhaps cd to directory"),
         M("--jit",         "",                     "enable JIT for the platform, same as " PLATFORM_JIT_OPTION),
-#if USE_RJIT
-        M("--rjit",        "",                     "enable C compiler-based JIT compiler (experimental)"),
-#endif
 #if USE_YJIT
         M("--yjit",        "",                     "enable in-process JIT compiler"),
+#endif
+#if USE_RJIT
+        M("--rjit",        "",                     "enable pure-Ruby JIT compiler (experimental)"),
 #endif
         M("-h",		   "",			   "show this message, --help for more info"),
     };