[jspi] - Use new -sJSPI flag to enable JSPI. (#21824)

Author: brendandahl

ChangeLog.md

@@ -23,6 +23,7 @@ See docs/process.md for more on how version tagging works.
 - Fix the location of the dummy `.worker.js` file that is now generated as part
   of pthread builds so that is generated alongside the main JavaScript file.
   See #21701. ()
+- `-sASYNCIFY=2` is setting now deprecated, use `-sJSPI` instead.
 
 3.1.58 - 04/23/24
 -----------------

emcc.py

@@ -298,6 +298,9 @@ def apply_user_settings():
     if key == 'WASM_OBJECT_FILES':
       settings.LTO = 0 if value else 'full'
 
+    if key == 'JSPI':
+      settings.ASYNCIFY = 2
+
 
 def cxx_to_c_compiler(cxx):
   # Convert C++ compiler name into C compiler name

site/source/docs/tools_reference/settings_reference.rst

@@ -1030,16 +1030,11 @@ ASYNCIFY
 Whether to support async operations in the compiled code. This makes it
 possible to call JS functions from synchronous-looking code in C/C++.
 
-- Run binaryen's Asyncify pass to transform the code using asyncify. This
-  emits a normal wasm file in the end, so it works everywhere, but it has a
-  significant cost in terms of code size and speed.
+- 1 (default): Run binaryen's Asyncify pass to transform the code using
+  asyncify. This emits a normal wasm file in the end, so it works everywhere,
+  but it has a significant cost in terms of code size and speed.
   See https://emscripten.org/docs/porting/asyncify.html
-- Depend on VM support for the wasm stack switching proposal. This allows
-  async operations to happen without the overhead of modifying the wasm.
-  This is experimental atm while spec discussion is ongoing, see
-  https://github.com/WebAssembly/js-promise-integration/
-  TODO: document which of the following flags are still relevant in this
-  mode (e.g. IGNORE_INDIRECT etc. are not needed)
+- 2 (deprecated): Use ``-sJSPI`` instead.
 
 .. _asyncify_imports:
 
@@ -1186,6 +1181,18 @@ Specify which of the exports will have JSPI applied to them and return a
 promise.
 Only supported for ASYNCIFY==2 mode.
 
+.. _jspi:
+
+JSPI
+====
+
+Use VM support for the JavaScript Promise Integration proposal. This allows
+async operations to happen without the overhead of modifying the wasm. This
+is experimental atm while spec discussion is ongoing, see
+https://github.com/WebAssembly/js-promise-integration/ TODO: document which
+of the following flags are still relevant in this mode (e.g. IGNORE_INDIRECT
+etc. are not needed)
+
 .. _exported_runtime_methods:
 
 EXPORTED_RUNTIME_METHODS

src/settings.js

@@ -805,16 +805,11 @@ var NODEJS_CATCH_REJECTION = true;
 // Whether to support async operations in the compiled code. This makes it
 // possible to call JS functions from synchronous-looking code in C/C++.
 //
-// - Run binaryen's Asyncify pass to transform the code using asyncify. This
-//   emits a normal wasm file in the end, so it works everywhere, but it has a
-//   significant cost in terms of code size and speed.
+// - 1 (default): Run binaryen's Asyncify pass to transform the code using
+//   asyncify. This emits a normal wasm file in the end, so it works everywhere,
+//   but it has a significant cost in terms of code size and speed.
 //   See https://emscripten.org/docs/porting/asyncify.html
-// - Depend on VM support for the wasm stack switching proposal. This allows
-//   async operations to happen without the overhead of modifying the wasm.
-//   This is experimental atm while spec discussion is ongoing, see
-//   https://github.com/WebAssembly/js-promise-integration/
-//   TODO: document which of the following flags are still relevant in this
-//   mode (e.g. IGNORE_INDIRECT etc. are not needed)
+// - 2 (deprecated): Use ``-sJSPI`` instead.
 //
 // [link]
 var ASYNCIFY = 0;
@@ -933,6 +928,16 @@ var ASYNCIFY_DEBUG = 0;
 // [link]
 var ASYNCIFY_EXPORTS = [];
 
+// Use VM support for the JavaScript Promise Integration proposal. This allows
+// async operations to happen without the overhead of modifying the wasm. This
+// is experimental atm while spec discussion is ongoing, see
+// https://github.com/WebAssembly/js-promise-integration/ TODO: document which
+// of the following flags are still relevant in this mode (e.g. IGNORE_INDIRECT
+// etc. are not needed)
+//
+// [link]
+var JSPI = 0;
+
 // Runtime elements that are exported on Module by default. We used to export
 // quite a lot here, but have removed them all. You should use
 // EXPORTED_RUNTIME_METHODS for things you want to export from the runtime.

test/common.py

@@ -881,7 +881,7 @@ def require_jspi(self):
     # emcc warns about stack switching being experimental, and we build with
     # warnings-as-errors, so disable that warning
     self.emcc_args += ['-Wno-experimental']
-    self.set_setting('ASYNCIFY', 2)
+    self.set_setting('JSPI')
     if self.is_wasm2js():
       self.skipTest('JSPI is not currently supported for WASM2JS')