From 4436c0eae6bacac66e456ebac45b150c080df1cf Mon Sep 17 00:00:00 2001
From: Alex Crichton <alex@alexcrichton.com>
Date: Sat, 21 Apr 2018 13:14:33 -0700
Subject: [PATCH] Avoid invoking a function pointer with JsStatic

The previous codegen wasn't enough to convince LLVM that the function pointer
was a constant value and could be aggressively inlined, so this updates the
`JsStatic` internals slightly to guarantee to LLVM that the function pointer is
constant and no dynamic dispatch is needed after all
---
 crates/backend/src/codegen.rs | 4 +++-
 src/lib.rs                    | 4 ++--
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/crates/backend/src/codegen.rs b/crates/backend/src/codegen.rs
index a91c44df9..0377db161 100644
--- a/crates/backend/src/codegen.rs
+++ b/crates/backend/src/codegen.rs
@@ -779,8 +779,10 @@ impl ToTokens for ast::ImportStatic {
 
                     }
                 }
+                static mut _VAL: ::wasm_bindgen::__rt::core::cell::UnsafeCell<Option<#ty>> =
+                    ::wasm_bindgen::__rt::core::cell::UnsafeCell::new(None);
                 ::wasm_bindgen::JsStatic {
-                    __inner: ::wasm_bindgen::__rt::core::cell::UnsafeCell::new(None),
+                    __inner: unsafe { &_VAL },
                     __init: init,
                 }
             };
diff --git a/src/lib.rs b/src/lib.rs
index 85667269e..cb3321cc6 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -303,9 +303,9 @@ impl Drop for JsValue {
 ///
 /// This type implements `Deref` to the inner type so it's typically used as if
 /// it were `&T`.
-pub struct JsStatic<T> {
+pub struct JsStatic<T: 'static> {
     #[doc(hidden)]
-    pub __inner: UnsafeCell<Option<T>>,
+    pub __inner: &'static UnsafeCell<Option<T>>,
     #[doc(hidden)]
     pub __init: fn() -> T,
 }