From fd04e1b4dbbb0dae130f3de79d69ca94ecdf883e Mon Sep 17 00:00:00 2001
From: Takashi Kokubun <takashikkbn@gmail.com>
Date: Sun, 11 Dec 2022 21:42:25 -0800
Subject: Implement a no-op JIT compiler

---
 lib/mjit/x86_64/assembler.rb | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)
 create mode 100644 lib/mjit/x86_64/assembler.rb

(limited to 'lib/mjit')

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
-- 
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