Name the iseq->body->param struct and update bindings for JITs

This will make reading the parameters nicer for the JITs. Should be
no-op for the C side.

Author: XrXr

vm_core.h

@@ -431,7 +431,7 @@ struct rb_iseq_constant_body {
      *  size         = M+N+O+(*1)+K+(&1)+(**1) // parameter size.
      */
 
-    struct {
+    struct rb_iseq_parameters {
         struct {
             unsigned int has_lead   : 1;
             unsigned int has_opt    : 1;

yjit/src/cruby_bindings.inc.rs

@@ -424,8 +424,12 @@ fn main() {
         .blocklist_type("VALUE")
         .blocklist_type("ID")
 
-        .opaque_type("rb_iseq_t")
-        .blocklist_type("rb_iseq_t")
+        // Avoid binding to stuff we don't use
+        .blocklist_item("rb_thread_struct.*")
+        .opaque_type("rb_thread_struct.*")
+        .blocklist_item("iseq_inline_storage_entry_.*")
+        .opaque_type("iseq_inline_storage_entry")
+        .opaque_type("iseq_compile_data")
 
         // Finish the builder and generate the bindings.
         .generate()

zjit/bindgen/src/main.rs

@@ -104,6 +104,7 @@ pub type RedefinitionFlag = u32;
 
 #[allow(unsafe_op_in_unsafe_fn)]
 #[allow(dead_code)]
+#[allow(unnecessary_transmutes)] // https://github.com/rust-lang/rust-bindgen/issues/2807
 #[allow(clippy::all)] // warning meant to help with reading; not useful for generated code
 mod autogened {
     use super::*;
@@ -246,14 +247,6 @@ pub fn insn_len(opcode: usize) -> u32 {
     }
 }
 
-/// Opaque iseq type for opaque iseq pointers from vm_core.h
-/// See: <https://doc.rust-lang.org/nomicon/ffi.html#representing-opaque-structs>
-#[repr(C)]
-pub struct rb_iseq_t {
-    _data: [u8; 0],
-    _marker: core::marker::PhantomData<(*mut u8, core::marker::PhantomPinned)>,
-}
-
 /// An object handle similar to VALUE in the C code. Our methods assume
 /// that this is a handle. Sometimes the C code briefly uses VALUE as
 /// an unsigned integer type and don't necessarily store valid handles but