Remove __wbindgen_global_argument_ptr intrinsic

We don't actually need this since we can simply pass in a number like 8
for the return pointer all the time. There's no need to allocate more
space in static data for a return pointer tha may not even get used!

Author: alexcrichton

crates/cli-support/src/js/binding.rs

@@ -118,14 +118,20 @@ impl<'a, 'b> Builder<'a, 'b> {
         if incoming_args {
             let mut webidl_params = webidl.params.iter();
 
-            // If we're returning via an out pointer then it's guaranteed to be the
-            // first argument. This isn't an argument of the function shim we're
-            // generating so synthesize the parameter and its value.
+            // If we're returning via an out pointer then it's guaranteed to be
+            // the first argument. This isn't an argument of the function shim
+            // we're generating so synthesize the parameter and its value.
+            //
+            // For the actual value of the return pointer we just pick the first
+            // properly aligned nonzero address. We use the address for a
+            // BigInt64Array sometimes which means it needs to be 8-byte
+            // aligned. Otherwise valid code is unlikely to ever be working
+            // around address 8, so this should be a safe address to use for
+            // returning data through.
             if binding.return_via_outptr.is_some() {
                 drop(webidl_params.next());
-                self.cx.expose_global_argument_ptr()?;
                 self.args_prelude
-                    .push_str("const retptr = globalArgumentPtr();\n");
+                    .push_str("const retptr = 8;\n");
                 arg_names.push("retptr".to_string());
             }
 

crates/cli-support/src/js/mod.rs

@@ -1558,25 +1558,6 @@ impl<'a> Context<'a> {
         })
     }
 
-    fn expose_global_argument_ptr(&mut self) -> Result<(), Error> {
-        if !self.should_write_global("global_argument_ptr") {
-            return Ok(());
-        }
-        self.require_internal_export("__wbindgen_global_argument_ptr")?;
-        self.global(
-            "
-            let cachedGlobalArgumentPtr = null;
-            function globalArgumentPtr() {
-                if (cachedGlobalArgumentPtr === null) {
-                    cachedGlobalArgumentPtr = wasm.__wbindgen_global_argument_ptr();
-                }
-                return cachedGlobalArgumentPtr;
-            }
-            ",
-        );
-        Ok(())
-    }
-
     fn expose_get_inherited_descriptor(&mut self) {
         if !self.should_write_global("get_inherited_descriptor") {
             return;

src/lib.rs

@@ -1017,20 +1017,6 @@ pub mod __rt {
         }
     }
 
-    pub const GLOBAL_STACK_CAP: usize = 16;
-
-    // Increase the alignment to 8 here because this can be used as a
-    // BigUint64Array pointer base which requires alignment 8
-    #[repr(align(8))]
-    struct GlobalData([u32; GLOBAL_STACK_CAP]);
-
-    static mut GLOBAL_STACK: GlobalData = GlobalData([0; GLOBAL_STACK_CAP]);
-
-    #[no_mangle]
-    pub unsafe extern "C" fn __wbindgen_global_argument_ptr() -> *mut u32 {
-        GLOBAL_STACK.0.as_mut_ptr()
-    }
-
     /// This is a curious function necessary to get wasm-bindgen working today,
     /// and it's a bit of an unfortunate hack.
     ///