From bcf5c1cdc4998bd6019c771eb8d50d6ca24d10f2 Mon Sep 17 00:00:00 2001
From: Takashi Kokubun <takashikkbn@gmail.com>
Date: Tue, 11 Feb 2025 16:11:02 -0800
Subject: Generate working putnil-leave using the backend

---
 zjit/src/asm/mod.rs |  5 +++++
 zjit/src/codegen.rs | 23 +++++++++++++++++++++++
 zjit/src/lib.rs     | 10 ++++------
 3 files changed, 32 insertions(+), 6 deletions(-)
 create mode 100644 zjit/src/codegen.rs

diff --git a/zjit/src/asm/mod.rs b/zjit/src/asm/mod.rs
index a9d4621b1e..a95569a011 100644
--- a/zjit/src/asm/mod.rs
+++ b/zjit/src/asm/mod.rs
@@ -130,6 +130,11 @@ impl CodeBlock {
         //    self.dropped_bytes = true; // retry emitting the Insn after next_page
         //}
     }
+
+    /// Make all the code in the region executable. Call this at the end of a write session.
+    pub fn mark_all_executable(&mut self) {
+        self.mem_block.borrow_mut().mark_all_executable();
+    }
 }
 
 impl crate::virtualmem::CodePtrBase for CodeBlock {
diff --git a/zjit/src/codegen.rs b/zjit/src/codegen.rs
new file mode 100644
index 0000000000..19b09e4456
--- /dev/null
+++ b/zjit/src/codegen.rs
@@ -0,0 +1,23 @@
+use crate::{asm::CodeBlock, backend::ir::*, cruby::*};
+
+/// Compile code that pops a frame and returns Qnil
+pub fn gen_leave(cb: &mut CodeBlock) {
+    let mut asm = Assembler::new();
+
+    // rdi: EC, rsi: CFP
+    let ec = C_ARG_OPNDS[0];
+    let cfp = C_ARG_OPNDS[1];
+
+    // Pop frame: CFP = CFP + RUBY_SIZEOF_CONTROL_FRAME
+    let incr_cfp = asm.add(cfp, RUBY_SIZEOF_CONTROL_FRAME.into());
+    asm.mov(cfp, incr_cfp);
+
+    // Set ec->cfp: *(EC + RUBY_OFFSET_EC_CFP) = CFP
+    asm.mov(Opnd::mem(64, ec, RUBY_OFFSET_EC_CFP), cfp);
+
+    // Return Qnil
+    asm.cret(Qnil.into());
+
+    asm.compile_with_regs(cb, Assembler::get_alloc_regs());
+    cb.mark_all_executable();
+}
diff --git a/zjit/src/lib.rs b/zjit/src/lib.rs
index b50eb720f5..b557602ccc 100644
--- a/zjit/src/lib.rs
+++ b/zjit/src/lib.rs
@@ -4,6 +4,7 @@
 mod state;
 mod cruby;
 mod ir;
+mod codegen;
 mod stats;
 mod utils;
 mod virtualmem;
@@ -12,6 +13,7 @@ mod backend;
 mod disasm;
 mod options;
 
+use codegen::gen_leave;
 use state::ZJITState;
 #[cfg(feature = "disasm")]
 use options::get_option;
@@ -80,7 +82,7 @@ pub extern "C" fn rb_zjit_iseq_gen_entry_point(iseq: IseqPtr, _ec: EcPtr) -> *co
 
     let cb = ZJITState::get_code_block();
     let start_ptr = cb.get_write_ptr();
-    //x86_emit(cb);
+    gen_leave(cb);
 
     #[cfg(feature = "disasm")]
     if get_option!(dump_disasm) {
@@ -89,9 +91,5 @@ pub extern "C" fn rb_zjit_iseq_gen_entry_point(iseq: IseqPtr, _ec: EcPtr) -> *co
         println!("{}", disasm);
     }
 
-    if cfg!(target_arch = "x86_64") {
-        start_ptr.raw_ptr(cb)
-    } else {
-        std::ptr::null()
-    }
+    start_ptr.raw_ptr(cb)
 }
-- 
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