Use direct table access over dynCall in invoke_xx functions (#11979)

This change starts the transition away from dynCall and towards
direct use of the wasm table.

In particular this change replaces the use of dynCall in invoke_xx
functions where possible.  dynCall is still needed for functions with
i64 in thier signature when WASM_BIGINT is not enabled.  When
WASM_BIGING is enabled this change removes all use of dynCall by
invoke_xx functions.

Author: sbc100

src/preamble.js

@@ -896,6 +896,7 @@ function createWasm() {
     // then exported.
     // TODO: do not create a Memory earlier in JS
     wasmMemory = exports['memory'];
+    wasmTable = exports['__indirect_function_table'];
     updateGlobalBufferAndViews(wasmMemory.buffer);
 #if ASSERTIONS
     writeStackCookie();

src/support.js

@@ -301,7 +301,7 @@ function createInvokeFunction(sig) {
   return function() {
     var sp = stackSave();
     try {
-      return Module['dynCall_' + sig].apply(null, arguments);
+      return dynCall(sig, arguments[0], Array.prototype.slice.call(arguments, 1));
     } catch(e) {
       stackRestore(sp);
       if (e !== e+0 && e !== 'longjmp') throw e;
@@ -602,24 +602,29 @@ function makeBigInt(low, high, unsigned) {
 
 /** @param {Array=} args */
 function dynCall(sig, ptr, args) {
-  if (args && args.length) {
-#if ASSERTIONS
-    // j (64-bit integer) must be passed in as two numbers [low 32, high 32].
-    assert(args.length === sig.substring(1).replace(/j/g, '--').length);
-#endif
-#if ASSERTIONS
-    assert(('dynCall_' + sig) in Module, 'bad function pointer type - no table for sig \'' + sig + '\'');
-#endif
-    return Module['dynCall_' + sig].apply(null, [ptr].concat(args));
-  } else {
-#if ASSERTIONS
-    assert(sig.length == 1);
-#endif
+#if !WASM_BIGINT
+  // Without WASM_BIGINT support we cannot directly call function with i64 as
+  // part of their signature, so we rely on the dynCall functions generated by
+  // wasm-emscripten-finalize
+  if (sig.indexOf('j') != -1) {
 #if ASSERTIONS
     assert(('dynCall_' + sig) in Module, 'bad function pointer type - no table for sig \'' + sig + '\'');
+    if (args && args.length) {
+      // j (64-bit integer) must be passed in as two numbers [low 32, high 32].
+      assert(args.length === sig.substring(1).replace(/j/g, '--').length);
+    } else {
+      assert(sig.length == 1);
+    }
 #endif
-    return Module['dynCall_' + sig].call(null, ptr);
+    if (args && args.length) {
+      return Module['dynCall_' + sig].apply(null, [ptr].concat(args));
+    } else {
+      return Module['dynCall_' + sig].call(null, ptr);
+    }
   }
+#endif
+
+  return wasmTable.get(ptr).apply(null, args)
 }
 
 var tempRet0 = 0;

tests/other/metadce/libcxxabi_message_O3_STANDALONE_WASM.exports

@@ -1,2 +1,3 @@
+__indirect_function_table
 _start
 memory

tests/other/metadce/mem_O3_ALLOW_MEMORY_GROWTH_STANDALONE_WASM.exports

@@ -1,2 +1,3 @@
+__indirect_function_table
 _start
 memory

tests/other/metadce/mem_O3_STANDALONE_WASM.exports

@@ -1,2 +1,3 @@
+__indirect_function_table
 _start
 memory

tests/other/metadce/mem_no_argv_O3_STANDALONE_WASM.exports

@@ -1,2 +1,3 @@
+__indirect_function_table
 _start
 memory

tests/other/metadce/mem_no_argv_O3_STANDALONE_WASM_flto.exports

@@ -1,2 +1,3 @@
+__indirect_function_table
 _start
 memory

tests/other/metadce/mem_no_main_O3_STANDALONE_WASM_noentry.exports

@@ -1,3 +1,4 @@
+__indirect_function_table
 _initialize
 foo
 memory

tests/test_other.py

@@ -7111,7 +7111,7 @@ def test_metadce_mem(self, filename, *args):
                            [], [], 128), # noqa
     # argc/argv support code etc. is in the wasm
     'O3_standalone':      ('libcxxabi_message.cpp', ['-O3', '-s', 'STANDALONE_WASM'],
-                           [], [], 198), # noqa
+                           [], [], 242), # noqa
   })
   def test_metadce_libcxxabi_message(self, filename, *args):
     self.run_metadce_test(filename, *args)

tools/building.py

@@ -484,6 +484,8 @@ def lld_flags_for_executable(external_symbol_list):
   if not Settings.STANDALONE_WASM:
     cmd.append('--import-memory')
     cmd.append('--import-table')
+  else:
+    cmd.append('--export-table')
 
   if Settings.USE_PTHREADS:
     cmd.append('--shared-memory')
@@ -1136,7 +1138,10 @@ def add_to_path(dirname):
       logger.error(proc.stderr) # print list of errors (possibly long wall of text if input was minified)
 
       # Exit and print final hint to get clearer output
-      exit_with_error('closure compiler failed (rc: %d.%s)', proc.returncode, '' if pretty else ' the error message may be clearer with -g1 and EMCC_DEBUG=2 set')
+      msg = 'closure compiler failed (rc: %d): %s' % (proc.returncode, shared.shlex_join(cmd))
+      if not pretty:
+        msg += ' the error message may be clearer with -g1 and EMCC_DEBUG=2 set'
+      exit_with_error(msg)
 
     if len(proc.stderr.strip()) > 0 and Settings.CLOSURE_WARNINGS != 'quiet':
       # print list of warnings (possibly long wall of text if input was minified)
@@ -1227,6 +1232,12 @@ def metadce(js_file, wasm_file, minify_whitespace, debug_info):
       'reaches': [],
       'root': True
     })
+    graph.append({
+      'export': '__indirect_function_table',
+      'name': 'emcc$export$__indirect_function_table',
+      'reaches': [],
+      'root': True
+    })
   # fix wasi imports TODO: support wasm stable with an option?
   WASI_IMPORTS = set([
     'environ_get',

tools/shared.py

@@ -1209,28 +1209,34 @@ def make_jscall(sig):
     return ret
 
   @staticmethod
-  def make_dynCall(sig):
-    # Optimize dynCall accesses in the case when not building with dynamic
-    # linking enabled.
-    if not Settings.MAIN_MODULE and not Settings.SIDE_MODULE:
-      return 'dynCall_' + sig
+  def make_dynCall(sig, args):
+    # wasm2c and asyncify are not yet compatible with direct wasm table calls
+    if Settings.ASYNCIFY or Settings.WASM2C or not JS.is_legal_sig(sig):
+      args = ','.join(args)
+      if not Settings.MAIN_MODULE and not Settings.SIDE_MODULE:
+        # Optimize dynCall accesses in the case when not building with dynamic
+        # linking enabled.
+        return 'dynCall_%s(%s)' % (sig, args)
+      else:
+        return 'Module["dynCall_%s"](%s)' % (sig, args)
     else:
-      return 'Module["dynCall_' + sig + '"]'
+      return 'wasmTable.get(%s)(%s)' % (args[0], ','.join(args[1:]))
 
   @staticmethod
   def make_invoke(sig, named=True):
     legal_sig = JS.legalize_sig(sig) # TODO: do this in extcall, jscall?
-    args = ','.join(['a' + str(i) for i in range(1, len(legal_sig))])
-    args = 'index' + (',' if args else '') + args
+    args = ['index'] + ['a' + str(i) for i in range(1, len(legal_sig))]
     ret = 'return ' if sig[0] != 'v' else ''
-    body = '%s%s(%s);' % (ret, JS.make_dynCall(sig), args)
+    body = '%s%s;' % (ret, JS.make_dynCall(sig, args))
     # C++ exceptions are numbers, and longjmp is a string 'longjmp'
     if Settings.SUPPORT_LONGJMP:
       rethrow = "if (e !== e+0 && e !== 'longjmp') throw e;"
     else:
       rethrow = "if (e !== e+0) throw e;"
 
-    ret = '''function%s(%s) {
+    name = (' invoke_' + sig) if named else ''
+    ret = '''\
+function%s(%s) {
   var sp = stackSave();
   try {
     %s
@@ -1239,7 +1245,8 @@ def make_invoke(sig, named=True):
     %s
     _setThrew(1, 0);
   }
-}''' % ((' invoke_' + sig) if named else '', args, body, rethrow)
+}''' % (name, ','.join(args), body, rethrow)
+
     return ret
 
   @staticmethod