YJIT: Use u32 for CodePtr to save 4 bytes each

We've long had a size restriction on the code memory region such that a
u32 could refer to everything. This commit capitalizes on this
restriction by shrinking the size of `CodePtr` to be 4 bytes from 8.

To derive a full raw pointer from a `CodePtr`, one needs a base pointer.
Both `CodeBlock` and `VirtualMemory` can be used for this purpose. The
base pointer is readily available everywhere, except for in the case of
the `jit_return` "branch". Generalize lea_label() to lea_jump_target()
in the IR to delay deriving the `jit_return` address until `compile()`,
when the base pointer is available.

On railsbench, this yields roughly a 1% reduction to `yjit_alloc_size`
(58,397,765 to 57,742,248).

1 files changed, 1 insertions, 1 deletions

diff --git a/yjit/src/yjit.rs b/yjit/src/yjit.rs
index 8431168763..d2ec5f0568 100644
--- a/yjit/src/yjit.rs
+++ b/yjit/src/yjit.rs
@@ -145,7 +145,7 @@ pub extern "C" fn rb_yjit_iseq_gen_entry_point(iseq: IseqPtr, ec: EcPtr, jit_exc
     let maybe_code_ptr = with_compile_time(|| { gen_entry_point(iseq, ec, jit_exception) });
 
     match maybe_code_ptr {
-        Some(ptr) => ptr.raw_ptr(),
+        Some(ptr) => ptr,
         None => std::ptr::null(),
     }
 }