Use direct table access over dynCall where possible

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

emcc.py

@@ -1576,10 +1576,11 @@ def check(input_file):
       # memalign is used to ensure allocated thread stacks are aligned.
       shared.Settings.EXPORTED_FUNCTIONS += ['_memalign', '_malloc']
 
-      # dynCall_ii is used to call pthread entry points in worker.js (as
-      # metadce does not consider worker.js, which is external, we must
-      # consider it a user export, i.e., one which can never be removed).
-      building.user_requested_exports += ['dynCall_ii']
+      if not shared.Settings.WASM:
+        # dynCall_ii is used to call pthread entry points in worker.js (as
+        # metadce does not consider worker.js, which is external, we must
+        # consider it a user export, i.e., one which can never be removed).
+        building.user_requested_exports += ['dynCall_ii']
 
       if shared.Settings.MINIMAL_RUNTIME:
         building.user_requested_exports += ['exit']

src/preamble.js

@@ -428,11 +428,7 @@ function callRuntimeCallbacks(callbacks) {
     }
     var func = callback.func;
     if (typeof func === 'number') {
-      if (callback.arg === undefined) {
-        Module['dynCall_v'](func);
-      } else {
-        Module['dynCall_vi'](func, callback.arg);
-      }
+      dynCallDirect(func, [callback.arg]);
     } else {
       func(callback.arg === undefined ? null : callback.arg);
     }
@@ -902,6 +898,7 @@ 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/preamble_minimal.js

@@ -200,6 +200,11 @@ var wasmOffsetConverter;
 #include "wasm_offset_converter.js"
 #endif
 
+/** @param {Array=} args */
+function dynCallDirect(ptr, args) {
+  return wasmTable.get(ptr).apply(null, args);
+}
+
 #if EXIT_RUNTIME
 
 function callRuntimeCallbacks(callbacks) {
@@ -211,11 +216,7 @@ function callRuntimeCallbacks(callbacks) {
     }
     var func = callback.func;
     if (typeof func === 'number') {
-      if (callback.arg === undefined) {
-        dynCall_v(func);
-      } else {
-        dynCall_vi(func, callback.arg);
-      }
+      dynCallDirect(func, [callback.arg]);
     } else {
       func(callback.arg === undefined ? null : callback.arg);
     }

src/support.js

@@ -577,16 +577,16 @@ function getFuncWrapper(func, sig) {
   if (!sigCache[func]) {
     // optimize away arguments usage in common cases
     if (sig.length === 1) {
-      sigCache[func] = function dynCall_wrapper() {
+      sigCache[func] = function() {
         return dynCall(sig, func);
       };
     } else if (sig.length === 2) {
-      sigCache[func] = function dynCall_wrapper(arg) {
+      sigCache[func] = function(arg) {
         return dynCall(sig, func, [arg]);
       };
     } else {
       // general case
-      sigCache[func] = function dynCall_wrapper() {
+      sigCache[func] = function() {
         return dynCall(sig, func, Array.prototype.slice.call(arguments));
       };
     }
@@ -600,26 +600,38 @@ function makeBigInt(low, high, unsigned) {
   return unsigned ? ((+((low>>>0)))+((+((high>>>0)))*4294967296.0)) : ((+((low>>>0)))+((+((high|0)))*4294967296.0));
 }
 
+/** @param {Array=} args */
+function dynCallDirect(ptr, args) {
+  return wasmTable.get(ptr).apply(null, args);
+}
+
 /** @param {Array=} args */
 function dynCall(sig, ptr, args) {
-  if (args && args.length) {
 #if ASSERTIONS
+  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);
     // 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
+  if (sig.indexOf('j') != -1) {
 #if ASSERTIONS
-    assert(('dynCall_' + sig) in Module, 'bad function pointer type - no table for sig \'' + sig + '\'');
+      assert(('dynCall_' + sig) in Module, 'bad function pointer type - no table for sig \'' + sig + '\'');
 #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
+
+  dynCallDirect(ptr, args);
 }
 
 var tempRet0 = 0;

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')

tools/shared.py

@@ -1212,25 +1212,35 @@ def make_jscall(sig):
   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
-    else:
+    if Settings.MAIN_MODULE or Settings.SIDE_MODULE:
       return 'Module["dynCall_' + sig + '"]'
+    else:
+      return 'dynCall_' + sig
 
   @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
     ret = 'return ' if sig[0] != 'v' else ''
-    body = '%s%s(%s);' % (ret, JS.make_dynCall(sig), args)
+    args = 'index' + (',' if args else '') + args
+    if Settings.WASM_BIGINT or 'j' not in sig:
+      new_args = ['a' + str(i) for i in range(1, len(legal_sig))]
+      for i in range(len(sig) - 1):
+        if sig[i+1] == 'j':
+          new_args[i] = 'BigInt(%s)' % new_args[i]
+      new_args = ','.join(new_args)
+      body = '%sdynCallDirect(index, [%s]);' % (ret, new_args)
+    else:
+      body = '%s%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 +1249,8 @@ def make_invoke(sig, named=True):
     %s
     _setThrew(1, 0);
   }
-}''' % ((' invoke_' + sig) if named else '', args, body, rethrow)
+}''' % (name, args, body, rethrow)
+
     return ret
 
   @staticmethod