address more of Alex' comments

Author: frank-emrich

crates/cli-flags/src/lib.rs

@@ -1005,9 +1005,6 @@ impl CommonOptions {
             ("gc", gc, wasm_gc)
             ("gc", reference_types, wasm_reference_types)
             ("gc", function_references, wasm_function_references)
-            // FIXME(frank-emrich): If function-references depends on the gc
-            // feature, and stack-switching requires function-references, that
-            // probably means that stack-switching should depend on gc.
             ("stack-switching", stack_switching, wasm_stack_switching)
         }
         Ok(())

crates/cranelift/src/func_environ.rs

@@ -2287,7 +2287,6 @@ impl FuncEnvironment<'_> {
             WasmHeapTopType::Any | WasmHeapTopType::Extern => pos.ins().iconst(types::I32, 0),
             WasmHeapTopType::Cont => {
                 let zero = pos.ins().iconst(self.pointer_type(), 0);
-                // TODO do this nicer
                 stack_switching::fatpointer::construct(self, &mut pos, zero, zero)
             }
         })

crates/cranelift/src/gc/enabled.rs

@@ -149,7 +149,10 @@ fn read_field_at_addr(
                     builder.func.dfg.first_result(call_inst)
                 }
                 WasmHeapTopType::Cont => {
-                    unimplemented!("Stack switching feature not compatible with GC, yet")
+                    // TODO(#10248) GC integration for stack switching
+                    return Err(wasmtime_environ::WasmError::Unsupported(
+                        "Stack switching feature not compatbile with GC, yet".to_string(),
+                    ));
                 }
             },
         },
@@ -1068,7 +1071,7 @@ pub fn translate_ref_test(
             func_env.is_subtype(builder, actual_shared_ty, expected_shared_ty)
         }
         WasmHeapType::ConcreteCont(_) => {
-            // TODO(#10248)
+            // TODO(#10248) GC integration for stack switching
             return Err(wasmtime_environ::WasmError::Unsupported(
                 "Stack switching feature not compatbile with GC, yet".to_string(),
             ));

crates/cranelift/src/stack_switching/fatpointer.rs

@@ -22,9 +22,7 @@ pub(crate) fn deconstruct<'a>(
 ) -> (ir::Value, ir::Value) {
     debug_assert_eq!(pos.func.dfg.value_type(contobj), POINTER_TYPE);
 
-    let lsbs = pos.ins().ireduce(I64, contobj);
-    let msbs = pos.ins().ushr_imm(contobj, 64);
-    let msbs = pos.ins().ireduce(I64, msbs);
+    let (lsbs, msbs) = pos.ins().isplit(contobj);
 
     let (revision_counter, contref) = match env.isa.endianness() {
         ir::Endianness::Little => (lsbs, msbs),

crates/wasmtime/src/runtime/externals/global.rs

@@ -130,9 +130,10 @@ impl Global {
                                 })
                                 .into(),
                         ),
-                        HeapType::NoCont | HeapType::ConcreteCont(_) | HeapType::Cont => todo!(
-                            "Embedder support for continuations has not yet been implemented!"
-                        ),
+                        HeapType::NoCont | HeapType::ConcreteCont(_) | HeapType::Cont => {
+                            // TODO(#10248) Required to support stack switching in the embedder API.
+                            unimplemented!()
+                        }
 
                         HeapType::NoExtern => Ref::Extern(None),
 

crates/wasmtime/src/runtime/externals/table.rs

@@ -189,7 +189,10 @@ impl Table {
                     }
                 }
 
-                runtime::TableElement::ContRef(_c) => todo!(), // TODO(dhil): Required for the embedder API.
+                runtime::TableElement::ContRef(_c) => {
+                    // TODO(#10248) Required to support stack switching in the embedder API.
+                    unimplemented!()
+                }
             }
         }
     }

crates/wasmtime/src/runtime/values.rs

@@ -281,8 +281,9 @@ impl Val {
                     HeapType::NoFunc => Ref::Func(None),
 
                     HeapType::NoCont | HeapType::ConcreteCont(_) | HeapType::Cont => {
+                        // TODO(#10248): Required to support stack switching in the embedder API.
                         unimplemented!()
-                    } // TODO(dhil): Need to do this for the embedder API.
+                    }
 
                     HeapType::Extern => ExternRef::_from_raw(store, raw.get_externref()).into(),
 

crates/wast-util/src/lib.rs

@@ -305,10 +305,8 @@ impl Compiler {
                 if config.threads() {
                     return true;
                 }
-                // Unsupported proposals. Note that other proposals have partial
-                // support at this time (pulley is a work-in-progress) and so
-                // individual tests are listed below as "should fail" even if
-                // they're not covered in this list.
+
+                // Stack switching is not supported by Pulley.
                 if config.stack_switching() {
                     return true;
                 }