__builtin_inline!

Add an experimental `__builtin_inline!(c_expression)` special intrinsic
which run a C code snippet.
In `c_expression`, you can access the following variables:
  * ec (rb_execution_context_t *)
  * self (const VALUE)
  * local variables (const VALUE)
Not that you can read these variables, but you can not write them.
You need to return from this expression and return value will be a
result of __builtin_inline!().

Examples:
  `def foo(x) __builtin_inline!('return rb_p(x);'); end` calls `p(x)`.
  `def double(x) __builtin_inline!('return INT2NUM(NUM2INT(x) * 2);')`
  returns x*2.

1 files changed, 13 insertions, 2 deletions

diff --git a/builtin.c b/builtin.c
index d936d1ceb6..d0d998da49 100644
--- a/builtin.c
+++ b/builtin.c
@@ -25,9 +25,12 @@ rb_load_with_builtin_functions(const char *feature_name, const struct rb_builtin
     const unsigned char *bin = builtin_lookup(feature_name, &size);
 
     // load binary
-    GET_VM()->builtin_function_table = table;
+    rb_vm_t *vm = GET_VM();
+    if (vm->builtin_function_table != NULL) rb_bug("vm->builtin_function_table should be NULL.");
+    vm->builtin_function_table = table;
+    vm->builtin_inline_index = 0;
     const rb_iseq_t *iseq = rb_iseq_ibf_load_bytes((const char *)bin, size);
-    GET_VM()->builtin_function_table = NULL;
+    vm->builtin_function_table = NULL;
 
     // exec
     rb_iseq_eval(iseq);
@@ -38,3 +41,11 @@ Init_builtin(void)
 {
     //
 }
+
+// inline
+VALUE
+rb_vm_lvar_exposed(rb_execution_context_t *ec, int index)
+{
+    const rb_control_frame_t *cfp = ec->cfp;
+    return cfp->ep[index];
+}