Compile with MicroJIT disabled when scrape fails

This is just so we can build successfully on -O0 and other cases that
are not supported by the code scraper.

tool/ruby_vm/models/micro_jit.rb

@@ -176,21 +176,21 @@ module RubyVM::MicroJIT
       else
         raise 'Unkonwn platform. Only Mach-O on macOS and ELF on Linux are supported'
       end
+      [true, comma_separated_hex_string(@pre_call_bytes), comma_separated_hex_string(@post_call_bytes)]
+    rescue => e
+      print_warning("scrape failed: #{e.message}")
+      [false, '', '']
+    end
+
+    def print_warning(text)
+      text = "ujit warning: #{text}"
+      text = "\x1b[1m#{text}\x1b[0m" if STDOUT.tty?
+      STDOUT.puts(text)
     end
 
     def comma_separated_hex_string(nums)
       nums.map{ |byte| '0x'+byte}.join(', ')
     end
-
-    def pre_call_bytes
-      scrape unless @pre_call_bytes
-      comma_separated_hex_string(@pre_call_bytes)
-    end
-
-    def post_call_bytes
-      scrape unless @post_call_bytes
-      comma_separated_hex_string(@post_call_bytes)
-    end
   end
 end
 

tool/ruby_vm/views/ujit_examples.inc.erb

@@ -12,5 +12,7 @@
     edit: __FILE__,
 } -%>
 
-static const uint8_t ujit_pre_call_bytes[] = { <%= RubyVM::MicroJIT.pre_call_bytes %> };
+% success, pre_call_bytes, post_call_bytes = RubyVM::MicroJIT.scrape
-static const uint8_t ujit_post_call_bytes[] = { <%= RubyVM::MicroJIT.post_call_bytes %> };
+static const uint8_t ujit_scrape_successful = <%= success %>;
+static const uint8_t ujit_pre_call_bytes[] = { <%= pre_call_bytes %> };
+static const uint8_t ujit_post_call_bytes[] = { <%= post_call_bytes %> };

ujit_compile.c

@@ -505,6 +505,9 @@ rb_ujit_enabled_p(void)
 void
 rb_ujit_init(void)
 {
+    if (!ujit_scrape_successful) {
+        return;
+    }
     // Initialize the code blocks
     size_t mem_size = 64 * 1024 * 1024;
     uint8_t* mem_block = alloc_exec_mem(mem_size);