PoC1: Move materialize_frames from side exits to jit_exec/JIT_EXEC

Instead of calling rb_zjit_materialize_frames in every side exit's
generated code, call zjit_materialize_frames once in jit_exec() and
JIT_EXEC() after the ZJIT entry trampoline returns. This reduces
generated code size by removing a C function call from each unique
side exit.

Author: k0kubun

vm.c

@@ -559,6 +559,8 @@ zjit_compile(rb_execution_context_t *ec)
 # define zjit_compile(ec) ((rb_jit_func_t)0)
 #endif
 
+static inline void zjit_materialize_frames(rb_control_frame_t *cfp);
+
 // Execute JIT code compiled by yjit_compile() or zjit_compile()
 static inline VALUE
 jit_exec(rb_execution_context_t *ec)
@@ -578,7 +580,14 @@ jit_exec(rb_execution_context_t *ec)
     if (zjit_entry) {
         rb_jit_func_t func = zjit_compile(ec);
         if (func) {
-            return ((rb_zjit_func_t)zjit_entry)(ec, ec->cfp, func);
+            VALUE result = ((rb_zjit_func_t)zjit_entry)(ec, ec->cfp, func);
+            // Materialize any remaining lightweight ZJIT frames on side exit.
+            // This is done here (once per JIT entry) instead of in each side exit
+            // to reduce generated code size.
+            if (UNDEF_P(result)) {
+                zjit_materialize_frames(ec->cfp);
+            }
+            return result;
         }
     }
 #endif

vm_exec.h

@@ -189,6 +189,7 @@ default:                        \
             rb_jit_func_t func = zjit_compile(ec); \
             if (func) { \
                 val = zjit_entry(ec, ec->cfp, func); \
+                if (UNDEF_P(val)) zjit_materialize_frames(ec->cfp); \
             } \
         } \
     } \

zjit/src/backend/lir.rs

@@ -2641,12 +2641,6 @@ impl Assembler
 
             asm_comment!(asm, "save cfp->jit_return");
             asm.store(Opnd::mem(64, CFP, RUBY_OFFSET_CFP_JIT_RETURN), 0.into());
-
-            asm_comment!(asm, "materialize caller frames");
-            unsafe extern "C" {
-                fn rb_zjit_materialize_frames(cfp: CfpPtr);
-            }
-            asm_ccall!(asm, rb_zjit_materialize_frames, CFP);
         }
 
         /// Tear down the JIT frame and return to the interpreter.

zjit/src/codegen.rs

@@ -2911,10 +2911,8 @@ c_callable! {
             // If we side-exit from function_stub_hit (before JIT code runs), we need to set them here.
             fn prepare_for_exit(iseq: IseqPtr, cfp: CfpPtr, sp: *mut VALUE, compile_error: &CompileError) {
                 unsafe {
-                    unsafe extern "C" {
-                        fn rb_zjit_materialize_frames(cfp: CfpPtr);
-                    }
-                    rb_zjit_materialize_frames(cfp);
+                    // Caller frames are materialized by jit_exec() after the entry trampoline returns.
+                    // The current frame's pc and iseq are already set by function_stub_hit before this point.
 
                     // Set SP which gen_push_frame() doesn't set
                     rb_set_cfp_sp(cfp, sp);