Implement a no-op JIT compiler

1 files changed, 35 insertions, 0 deletions

diff --git a/lib/mjit/x86_64/assembler.rb b/lib/mjit/x86_64/assembler.rb
new file mode 100644
index 0000000000..14f414b33b
--- /dev/null
+++ b/lib/mjit/x86_64/assembler.rb
@@ -0,0 +1,35 @@
+class RubyVM::MJIT::Assembler
+  ByteWriter = RubyVM::MJIT::CType::Immediate.parse('char')
+
+  def initialize
+    @bytes = []
+  end
+
+  def compile(compiler)
+    RubyVM::MJIT::C.mjit_mark_writable
+    write_bytes(compiler.write_addr, @bytes)
+    RubyVM::MJIT::C.mjit_mark_executable
+
+    compiler.write_pos += @bytes.size
+    @bytes.clear
+  end
+
+  def mov(_reg, val)
+    @bytes.push(0xb8, val, 0x00, 0x00, 0x00)
+  end
+
+  def ret
+    @bytes.push(0xc3)
+  end
+
+  private
+
+  def write_bytes(addr, bytes)
+    writer = ByteWriter.new(addr)
+    # If you pack bytes containing \x00, Ruby fails to recognize bytes after \x00.
+    # So writing byte by byte to avoid hitting that situation.
+    bytes.each_with_index do |byte, index|
+      writer[index] = byte
+    end
+  end
+end